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A torus

As the distance to the axis of revolution decreases, the ring torus becomes a spindle torus and then degenerates into a sphere.

In geometry, a torus (pl. tori) is a surface of revolution generated by revolving a circle in three dimensional space about an axis coplanar with the circle. In most contexts it is assumed that the axis does not touch the circle – in this case the surface has a ring shape and is called a ring torus or simply torus if the ring shape is implicit.

Other types of torus include the horn torus, which is generated when the axis is tangent to the circle, and the spindle torus, which is generated when the axis is a chord of the circle. A degenerate case is when the axis is a diameter of the circle, which simply generates the surface of a sphere. The ring torus bounds a solid known as a toroid. The adjective toroidal can be applied to tori, toroids or, more generally, any ring shape as in toroidal inductors and transformers. Real world examples of (approximately) toroidal objects include doughnuts, inner tubes, many lifebuoys, O-rings and vortex rings.

In topology, a ring torus is homeomorphic to the Cartesian product of two circles: S¹ × S¹, and the latter is taken to be the definition in that context. It is a compact 2-manifold of genus 1. The ring torus is one way to embed this space into Euclidean space, but another way to do this is the Cartesian product of the embedding of S¹ in the plane. This produces a geometric object called the Clifford torus, surface in 4-space.

The word torus comes from the Latin word meaning cushion.^[1]

1 Geometry
2 Topology
3 Two-sheeted cover
4 n-dimensional torus
- 4.1 Configuration space
5 Flat torus
6 n-fold torus
7 Toroidal polyhedra
8 Automorphisms
9 Coloring a torus
10 Cutting a torus
11 See also
12 Notes
13 References
14 External links

Geometry

A torus is the product of two circles, in this case the red circle is swept around axis defining the pink circle. R is the radius of the pink circle, r is the radius of the red one.

Ring torus

Horn torus

Spindle torus

Bottom-halves and cross-sections of the three classes

A diagram depicting the poloidal ( $θ$ ) direction, represented by the red arrow, and the toroidal ( $ζ$ or $φ$ ) direction, represented by the blue arrow.

A torus can be defined parametrically by:^[2]

$x(u, v) = (R + r \cos{v}) \cos{u} \,$

$y(u, v) = (R + r \cos{v}) \sin{u} \,$

$z(u, v) = r \sin{v} \,$

where

u,v are in the interval [0, 2π),

R (or A) is the distance from the center of the tube to the center of the torus,

r (or a) is the radius of the tube.

R and r are also known as the "major radius" and "minor radius", respectively. The ratio of the two is known as the "aspect ratio". A doughnut has an aspect ratio of 2 to 3.

An implicit equation in Cartesian coordinates for a torus radially symmetric about the z-axis is

$\left(R - \sqrt{x^2 + y^2}\right)^2 + z^2 = r^2, \,\!$

or the solution of $f (x, y, z) = 0$ , where

$f(x,y,z) = \left(R - \sqrt{x^2 + y^2}\right)^2 + z^2 - r^2.\,\!$

Algebraically eliminating the square root gives a quartic equation,

$(x^2+y^2+z^2 + R^2 - r^2)^2 = 4R^2(x^2+y^2). \,\!$

The three different classes of standard tori correspond to the three possible relative sizes of r and R. When R > r, the surface will be the familiar ring torus. The case R = r corresponds to the horn torus, which in effect is a torus with no "hole". The case R < r describes the self-intersecting spindle torus. When R = 0, the torus degenerates to the sphere.

The surface area and interior volume of this torus are easily computed using Pappus's centroid theorem giving^[3]

$A = 4 \pi^2 R r = \left( 2\pi r \right) \left(2 \pi R \right) \,$

$V = 2 \pi^2 R r^2 = \left ( \pi r ^2 \right ) \left( 2 \pi R \right). \,$

These formulas are the same as for a cylinder of length 2πR and radius r, created by cutting the tube and unrolling it by straightening out the line running around the center of the tube. The losses in surface area and volume on the inner side of the tube exactly cancel out the gains on the outer side.

As a torus is the product of two circles, a modified version of the spherical coordinate system is sometimes used. In traditional spherical coordinates there are three measures, R, the distance from the center of the coordinate system, and $θ$ and $φ$ , angles measured from the center point. As a torus has, effectively, two center points, the centerpoints of the angles are moved; $φ$ measures the same angle as it does in the spherical system, but is known as the “toroidal” direction. The center point of $θ$ is moved to the center of r, and is known as the “poloidal” direction. These terms were first used in a discussion of the Earth’s magnetic field, where “poloidal” was used to denote “the direction toward the poles”.^[4] In modern use these terms are more commonly used to discuss magnetic confinement fusion devices.

Topology

Topologically, a torus is a closed surface defined as the product of two circles: S¹ × S¹. This can be viewed as lying in C² and is a subset of the 3-sphere S³ of radius √2. This topological torus is also often called the Clifford torus. In fact, S³ is filled out by a family of nested tori in this manner (with two degenerate circles), a fact which is important in the study of S³ as a fiber bundle over S² (the Hopf bundle).

The surface described above, given the relative topology from R³, is homeomorphic to a topological torus as long as it does not intersect its own axis. A particular homeomorphism is given by stereographically projecting the topological torus into R³ from the north pole of S³.

The torus can also be described as a quotient of the Cartesian plane under the identifications

(x,y) ~ (x+1,y) ~ (x,y+1).

Or, equivalently, as the quotient of the unit square by pasting the opposite edges together, described as a fundamental polygon $A B A - 1 B - 1$ .

Turning a punctured torus inside-out

The fundamental group of the torus is just the direct product of the fundamental group of the circle with itself:

$\pi_1(\mathbb{T}^2) = \pi_1(S^1) \times \pi_1(S^1) \cong \mathbb{Z} \times \mathbb{Z}.$

Intuitively speaking, this means that a closed path that circles the torus’ “hole” (say, a circle that traces out a particular latitude) and then circles the torus’ “body” (say, a circle that traces out a particular longitude) can be deformed to a path that circles the body and then the hole. So, strictly ‘latitudinal’ and strictly ‘longitudinal’ paths commute. This might be imagined as two shoelaces passing through each other, then unwinding, then rewinding.

If a torus is punctured and turned inside out then another torus results, with lines of latitude and longitude interchanged.

The first homology group of the torus is isomorphic to the fundamental group (this follows from Hurewicz theorem since the fundamental group is abelian).

Two-sheeted cover

The 2-torus double-covers the 2-sphere, with four ramification points. Every conformal structure on the 2-torus can be represented as a two-sheeted cover of the 2-sphere. The points on the torus corresponding to the ramification points are the Weierstrass points. In fact, the conformal type of the torus is determined by the cross-ratio of the four points.

n-dimensional torus

The torus has a generalization to higher dimensions, the n-dimensional torus, often called the n-torus for short. (This is one of two different meanings of the term “n-torus”.) Recalling that the torus is the product space of two circles, the n-dimensional torus is the product of n circles. That is:

$\mathbb{T}^n = \underbrace{S^1 \times S^1 \times \cdots \times S^1}_n.$

The torus discussed above is the 2-dimensional torus. The 1-dimensional torus is just the circle. Just as for the 2-torus, the n-torus can be described as a quotient of Rⁿ under integral shifts in any coordinate. That is, the n-torus is Rⁿ modulo the action of the integer lattice Zⁿ (with the action being taken as vector addition). Equivalently, the n-torus is obtained from the n-dimensional hypercube by gluing the opposite faces together.

An n-torus in this sense is an example of an n-dimensional compact manifold. It is also an example of a compact abelian Lie group. This follows from the fact that the unit circle is a compact abelian Lie group (when identified with the unit complex numbers with multiplication). Group multiplication on the torus is then defined by coordinate-wise multiplication.

Toroidal groups play an important part in the theory of compact Lie groups. This is due in part to the fact that in any compact Lie group G one can always find a maximal torus; that is, a closed subgroup which is a torus of the largest possible dimension. Such maximal tori T have a controlling role to play in theory of connected G.

Automorphisms of T are easily constructed from automorphisms of the lattice Zⁿ, which are classified by integral matrices M of size n×n which are invertible with integral inverse; these are just the integral M of determinant +1 or −1. Making M act on Rⁿ in the usual way, one has the typical toral automorphism on the quotient.

The fundamental group of an n-torus is a free abelian group of rank n. The k-th homology group of an n-torus is a free abelian group of rank n choose k. It follows that the Euler characteristic of the n-torus is 0 for all n. The cohomology ring H^•(Tⁿ,Z) can be identified with the exterior algebra over the Z-module Zⁿ whose generators are the duals of the n nontrivial cycles.

Configuration space

The configuration space of 2 not necessarily distinct points on the circle is the orbifold quotient of the 2-torus, $T 2 / S 2,$ which is the Möbius strip.

As the n-torus is the n-fold product of the circle, the n-torus is the configuration space of n ordered, not necessarily distinct points on the circle. Symbolically, $T n = (S 1) n .$ The configuration space of unordered, not necessarily distinct points is accordingly the orbifold $T n / S n,$ which is the quotient of the torus by the symmetric group on n letters (by permuting the coordinates).

For $n = 2,$ the quotient is the Möbius strip, the edge corresponding to the orbifold points where the two coordinates coincide. For $n = 3$ this quotient may be described as a solid torus with cross-section an equilateral triangle, with a twist; equivalently, as a triangular prism whose top and bottom faces are connected with a ⅓ twist (120°): the 3-dimensional interior corresponds to the points on the 3-torus where all 3 coordinates are distinct, the 2-dimensional face corresponds to points with 2 coordinates equal and the 3rd different, while the 1-dimensional edge corresponds to points with all 3 coordinates identical.

These orbifolds have found significant applications to music theory in the work of Dmitri Tymoczko and collaborators (Felipe Posada and Michael Kolinas, et al.), being used to model musical triads.^[5]^[6]

Flat torus

The flat torus is a specific embedding of the familiar 2-torus into Euclidean 4-space or higher dimensions. Its surface has zero Gaussian curvature everywhere. Its surface is “flat” in the same sense that the surface of a cylinder is “flat”. In 3 dimensions one can bend a flat sheet of paper into a cylinder without stretching the paper, but you cannot then bend this cylinder into a torus without stretching the paper. In 4 dimensions one can (mathematically).

A simple 4-d Euclidean embedding is as follows: <x,y,z,w> = <R cos u, R sin u, P cos v, P sin v> where R and P are constants determining the aspect ratio. It is diffeomorphic to a regular torus but not isometric. It can not be isometrically embedded into Euclidean 3-space. Mapping it into 3-space requires you to “bend” it, in which case it looks like a regular torus, for example, the following map <x,y,z> = <(R + P sin v)cos u, (R + P sin v)sin u, P cos v>.

A flat torus partitions the 3-sphere into two congruent solid tori subsets with the aforsaid flat torus surface as their common boundary.

A stereographic projection of a Clifford torus performing a simple rotation through the xz-plane.

n-fold torus

In the theory of surfaces the term n-torus has a different meaning. Instead of the product of n circles, they use the phrase to mean the connected sum of n 2-dimensional tori. To form a connected sum of two surfaces, remove from each the interior of a disk and “glue” the surfaces together along the disks’ boundary circles. To form the connected sum of more than two surfaces, sum two of them at a time until they are all connected together. In this sense, an n-torus resembles the surface of n doughnuts stuck together side by side, or a 2-dimensional sphere with n handles attached.

An ordinary torus is a 1-torus, a 2-torus is called a double torus, a 3-torus a triple torus, and so on. The n-torus is said to be an “orientable surface” of “genus” n, the genus being the number of handles. The 0-torus is the 2-dimensional sphere.

The classification theorem for surfaces states that every compact connected surface is either a sphere, an n-torus with n > 0, or the connected sum of n projective planes (that is, projective planes over the real numbers) with n > 0.

double torus	triple torus

Toroidal polyhedra

For more details on this topic, see Toroidal polyhedron.

A toroidal polyhedron with 6×4=24 quadrilateral faces.

Polyhedra with the topological type of a torus are called toroidal polyhedra, and satisfy a modified version of the polyhedron formula, $E - F - V = 0.$

The term “toroidal polydron” is also used for higher genus polyhedra and for immersions of toroidal polyhedra.

This section requires expansion.

Automorphisms

The homeomorphism group (or the subgroup of diffeomorphisms) of the torus is studied in geometric topology. Its mapping class group (the group of connected components) is isomorphic to the group GL(n, Z) of invertible integer matrices, and can be realized as linear maps on the universal covering space $\mathbf{R}^n$ that preserve the standard lattice $\mathbf{Z}^n$ (this corresponds to integer coefficients) and thus descend to the quotient.

At the level of homotopy and homology, the mapping class group can be identified as the action on the first homology (or equivalently, first cohomology, or on the fundamental group, as these are all naturally isomorphic; note also that the first cohomology group generates the cohomology algebra):

$\mathrm{MCG}(T^n) = \mathrm{Aut}(\pi_1(X)) = \mathrm{Aut}(\mathbf{Z}^n) = \mathrm{GL}(n,\mathbf{Z}).$

Since the torus is an Eilenberg-MacLane space K(G, 1), its homotopy equivalences, up to homotopy, can be identified with automorphisms of the fundamental group); that this agrees with the mapping class group reflects that all homotopy equivalences can be realized by homeomorphisms – every homotopy equivalence is homotopic to a homeomorphism – and that homotopic homeomorphisms are in fact isotopic (connected through homeomorphisms, not just through homotopy equivalences). More tersely, the map $\mathrm{Homeo}(T^n) \to \mathrm{SHE}(T^n)$ is 1-connected (isomorphic on path-components, onto fundamental group). This is a “homeomorphism reduces to homotopy reduces to algebra” result.

Thus the short exact sequence of the mapping class group splits (an identification of the torus as the quotient of $\mathbf{R}^n$ gives a splitting, via the linear maps, as above):

$1 \rightarrow {\rm Homeo}_0(T^n) \rightarrow {\rm Homeo}(T^n) \rightarrow {\rm MCG}(T^n) \rightarrow 1,$

so the homeomorphism group of the torus is a semidirect product, $\mathrm{Homeo}(T^n) \cong \mathrm{Homeo}_0(T^n) \rtimes \mathrm{GL}(n,\mathbf{Z}).$

The mapping class group of higher genus surfaces is much more complicated, and an area of active research.

Coloring a torus

If a torus is divided into regions, then it is always possible to color the regions with no more than seven colors so that neighboring regions have different colors. (Contrast with the four color theorem for the plane.)

This construction shows the torus divided into the maximum of seven regions, every one of which touches every other.

Cutting a torus

A standard torus (specifically, a ring torus) can be cut with n planes into at most 16(n³ + 3n² + 8n) parts, integer sequence A003600.^[7] The initial terms of this sequence are 1, 2, 6, 13, for n starting from 0.

Notes

^ Harold A. Stein … (2002). Fitting guide for rigid and soft contact lenses : a practical approach. St. Louis: Mosby. p. 16. ISBN 9780323014403. http://books.google.com/?id=GGoNQzt3I_IC&pg=PA16&lpg=PA16&dq=torus+Latin+word+for+a+cushion+of+this+shape.
^ http://www.geom.uiuc.edu/zoo/toptype/torus/standard/eqns.html
^ Weisstein, Eric W., “Torus” from MathWorld.
^ “Oxford English Dictionary Online”. poloidal. Oxford University Press. http://dictionary.oed.com/cgi/entry/50183023?single=1&query_type=word&queryword=poloidal&first=1&max_to_show=10. Retrieved 2007-08-10.
^ Tymoczko, Dmitri (7 July 2006).
“The Geometry of Musical Chords”
. Science 313 (5783): 72–74. doi:10.1126/science.1126287. PMID 16825563.
http://www.brainmusic.org/EducationalActivitiesFolder/Tymoczko_chords2006.pdf
^ Tony Phillips, Tony Phillips’ Take on Math in the Media, American Mathematical Society, October 2006
^ Weisstein, Eric W., “Torus Cutting” from MathWorld.

References

NOCIONES DE GEOMETRIA ANALITICA Y ALGEBRA LINEAL, ISBN 9789701065969, Author: KOZAK ANA MARIA, POMPEYA PASTORELLI SONIA, VERDANEGA PEDRO EMILIO, Editorial: MCGRAW-HILL, Edition 2007, 744 pages, language; spanish
Allen Hatcher. Algebraic topology. Cambridge University Press, 2002. ISBN 0-521-79540-0.
V.V. Nikulin, I.R.Shafarevich. Geometries and Groups. Springer, 1987. ISBN 3540152814, ISBN 9783540152811.
http://www.mathcurve.com/surfaces/tore/tore.shtml
“Tore (notion géométrique)” at Encyclopédie des Formes Mathématiques Remarquables

External links

Wikimedia Commons has media related to: Torus

Creation of a torus at cut-the-knot
“4D torus” Fly-through cross-sections of a four dimensional torus.
“Relational Perspective Map” Visualizing high dimensional data with flat torus.
“Torus Games” Free downloadable games for Windows and Mac OS X that highlight the topology of a torus.
Polydos

This information originally retrieved from http://en.wikipedia.org/wiki/Torus
on Wednesday 24th August 2011 12:48 pm EDT
Now edited and maintained by ManufacturingET.org

Wire-Frame Modeling

4:45 pm |

ManufacturingET.org > 2011 > August

Sample rendering of a wireframe cube, icosahedron, and approximate sphere

A wireframe image using hidden line removal

Perspective displayed in Wireframe representation of an architectural project

A wire frame model is a visual presentation of a three dimensional or physical object used in 3D computer graphics. It is created by specifying each edge of the physical object where two mathematically continuous smooth surfaces meet, or by connecting an object’s constituent vertices using straight lines or curves. The object is projected onto the computer screen by drawing lines at the location of each edge.

Using a wire frame model allows visualization of the underlying design structure of a 3D model. Traditional 2-dimensional views and drawings can be created by appropriate rotation of the object and selection of hidden line removal via cutting planes.

Since wireframe renderings are relatively simple and fast to calculate, they are often used in cases where a high screen frame rate is needed (for instance, when working with a particularly complex 3D model, or in real-time systems that model exterior phenomena). When greater graphical detail is desired, surface textures can be added automatically after completion of the initial rendering of the wireframe. This allows the designer to quickly review changes or rotate the object to new desired views without long delays associated with more realistic rendering.

The wire frame format is also well suited and widely used in programming tool paths for DNC (Direct Numerical Control) machine tools.

Wire frame models were used extensively in video games to represent 3D objects during the 1980s and early 1990s when properly filled 3D objects would have been too complex to calculate and draw with the computers of the time.

Introduction

The technology has encompassed two main fields. Either creating aesthetic (Class A surfaces) that also perform a function; for example, car bodies and consumer product outer forms, or technical surfaces for components such as gas turbine blades and other fluid dynamic engineering components.

CAD software packages use two basic methods for the creation of surfaces. The first begins with construction curves (splines) from which the 3D surface is then swept (section along guide rail) or meshed (lofted) through.

A surface being created from curves.

Animated version

The second method is direct creation of the surface with manipulation of the surface poles/control points.

Surface edit by poles

From these initially created surfaces, other surfaces are constructed using either derived methods such as offset or angled extensions from surfaces; or via bridging and blending between groups of surfaces.

Variable smooth blend between surfaces.

Animated version

Surfaces

Freeform surface, or freeform surfacing, is used in CAD and other computer graphics software to describe the skin of a 3D geometric element. Freeform surfaces do not have rigid radial dimensions, unlike regular surfaces such as planes, cylinders and conic surfaces. They are used to describe forms such as turbine blades, car bodies and boat hulls. Initially developed for the automotive and aerospace industries, freeform surfacing is now widely used in all engineering design disciplines from consumer goods products to ships. Most systems today use nonuniform rational B-spline (NURBS) mathematics to describe the surface forms; however, there are other methods such as Gorden surfaces or Coons surfaces .

The forms of freeform surfaces (and curves) are not stored or defined in CAD software in terms of polynomial equations, but by their poles, degree, and number of patches (segments with spline curves). The degree of a surface determines its mathematical properties, and can be seen as representing the shape by a polynomial with variables to the power of the degree value. For example, a surface with a degree of 1 would be a flat cross section surface. A surface with degree 2 would be curved in one direction, while a degree 3 surface could (but does not necessarily) change once from concave to convex curvature. Some CAD systems use the term order instead of degree. The order of a polynomial is one greater than the degree, and gives the number of coefficients rather than the greatest exponent.

Example surface pole map

The poles (sometimes known as control points) of a surface define its shape. The natural surface edges are defined by the positions of the first and last poles. (Note that a surface can have trimmed boundaries.) The intermediate poles act like magnets drawing the surface in their direction. The surface does not, however, go through these points. The second and third poles as well as defining shape, respectively determine the start and tangent angles and the curvature. In a single patch surface (Bézier surface), there is one more pole than the degree values of the surface. Surface patches can be merged into a single NURBS surface; at these points are knot lines. The number of knots will determine the influence of the poles on either side and how smooth the transition is. The smoothness between patches, known as continuity, is often referred to in terms of a C value:

C0: just touching, could have a nick
C1: tangent, but could have sudden change in curvature
C2: the patches are curvature continuous to one another

Two more important aspects are the U and V parameters. These are values on the surface ranging from 0 to 1, used in the mathematical definition of the surface and for defining paths on the surface: for example, a trimmed boundary edge. Note that they are not proportionally spaced along the surface. A curve of constant U or constant V is known as an isoperimetric curve, or U (V) line. In CAD systems, surfaces are often displayed with their poles of constant U or constant V values connected together by lines; these are known as control polygons.

Modelling

When defining a form, an important factor is the continuity between surfaces – how smoothly they connect to one another.

One example of where surfacing excels is automotive body panels. Just blending two curved areas of the panel with different radii of curvature together, maintaining tangential continuity (meaning that the blended surface doesn’t change direction suddenly, but smoothly) won’t be enough. They need to have a continuous rate of curvature change between the two sections, or else their reflections will appear disconnected.

The continuity is defined using the terms

G0 – position (touching)
G1 – tangent (angle)
G2 – curvature (radius)
G3 – acceleration (rate of change of curvature)

To achieve a high quality NURBS or Bezier surface, degrees of 5 or greater are generally used. Depending on the product and production process, different levels of accuracy are used but tolerances usually range from 0.02 mm to .001 mm (for example, in the fairing of BIW concept surfaces to production surface). For ship building, this need not be so tight, but for precision gears and medical devices it is much finer.

History of Terms

The term lofting originally came from the shipbuilding industry where loftsmen worked on “barn loft” type structures to create the keel and bulkhead forms out of wood. This was then passed on to the aircraft then automotive industries who also required streamline shapes.

The term spline also has nautical origins coming from East Anglian dialect word for a thin long strip of wood (probably from old English and Germanic word splint).

Freeform Surface Modelling Software

CATIA
Cobalt (Ashlar-Vellum)
form•Z (http:www.formz.com)
ICEM Surf
Imageware
ProEngineer ISDX ([1])
NX (Unigraphics)
ProEngineer
Rhinoceros 3D
FreeForm Modeling Plus from SensAble Technologies (Sensable.com)
solidThinking
Autodesk Inventor
Solidworks
Alias StudioTools
FreeSHIP (FreeSHIP)
GenesisIOD (GenesisIOD)
OmniCAD (OmniCAD)
Thinkdesign (Thinkdesign)
MicroStation (Bentley Systems Inc)
Shark FX (Punch!)
Moi Moment of Inspiration 3D modeling for designers and artists (Moi3d)

Overview

The use of solid modeling techniques allows for the automation of several difficult engineering calculations that are carried out as a part of the design process. Simulation, planning, and verification of processes such as machining and assembly were one of the main catalysts for the development of solid modeling. More recently, the range of supported manufacturing applications has been greatly expanded to include sheet metal manufacturing, injection molding, welding, pipe routing etc. Beyond traditional manufacturing, solid modeling techniques serve as the foundation for rapid prototyping, digital data archival and reverse engineering by reconstructing solids from sampled points on physical objects, mechanical analysis using finite elements, motion planning and NC path verification, kinematic and dynamic analysis of mechanisms, and so on. A central problem in all these applications is the ability to effectively represent and manipulate three dimensional geometry in a fashion that is consistent with the physical behavior of real artifacts. Solid modeling research and development has effectively addressed many of these issues, and continues to be a central focus of computer aided engineering.

Mathematical foundations

The notion of solid modeling as practiced today relies on the specific need for informational completeness in mechanical geometric modeling systems, in the sense that any computer model should support all geometric queries that may be asked of its corresponding physical object. The requirement implicitly recognizes the possibility of several computer representations of the same physical object as long as any two such representations are consistent. It is impossible to computationally verify informational completeness of a representation unless the notion of a physical object is defined in terms of computable mathematical properties and independent of any particular representation. Such reasoning led to the development of the modeling paradigm that has shaped the field of solid modeling as we know it today.^[2]

All manufactured components have finite size and well behaved boundaries, so initially the focus was on mathematically modeling rigid parts made of homogeneous isotropic material that could be added or removed. These postulated properties can be translated into properties of subsets of three dimensional Euclidean space. The two common approaches to define solidity rely on point-set topology and algebraic topology respectively. Both models specify how solids can be built from simple pieces or cells.

Regularization of a 2-d set by taking the closure of its interior

According to the continuum point set model of solidity, all the points of any X ⊂ ℝ³ can be classified according to their neighborhoods with respect to X as interior, exterior, or boundary points. Assuming ℝ³ is endowed with the typical Euclidean metric, a neighborhood of a point p ∈X takes the form of an open ball. For X to be considered solid every neighborhood of any p ∈X must be consistently three dimensional; points with lower dimensional neighborhoods indicate a lack of solidity. Dimensional homogeneity of neighborhoods is guaranteed for the class of closed regular sets, defined as sets equal to the closure of their interior. Any X ⊂ ℝ³ can be turned into a closed regular set or regularized by taking the closure of its interior, and thus the modeling space of solids is mathematically defined to be the space of closed regular subsets of ℝ³ (by the Heine-Borel theorem it is implied that all solids are compact sets). In addition, solids are required to be closed under the Boolean operations of set union, intersection, and difference (to guarantee solidity after material addition and removal). Applying the standard Boolean operations to closed regular sets may not produce a closed regular set, but this problem can be solved by regularizing the result of applying the standard Boolean operations.^[3] The regularized set operations are denoted ∪^∗, ∩^∗, and −^∗.

The combinatorial characterization of a set X ⊂ ℝ³ as a solid involves representing X as an orientable cell complex so that the cells provide finite spatial addresses for points in an otherwise innumerable continuum.^[1] The class of semi-analytic bounded subsets of Euclidean space is closed under Boolean operations (standard and regularized) and exhibits the additional property that every semi-analytic set can be stratified into a collection of disjoint cells of dimensions 0,1,2,3. A triangulation of a semi-analytic set into a collection of points, line segments, triangular faces, and tetrahedral elements is an example of a stratification that is commonly used. The combinatorial model of solidity is then summarized by saying that in addition to being semi-analytic bounded subsets, solids are three dimensional topological polyhedra, specifically three dimensional orientable manifolds with boundary.^[4] In particular this implies the Euler characteristic of the combinatorial boundary^[5] of the polyhedron is 2. The combinatorial manifold model of solidity also guarantees the boundary of a solid separates space into exactly two components as a consequence of the Jordan-Brouwer theorem, thus eliminating sets with non-manifold neighborhoods that are deemed impossible to manufacture.

The point-set and combinatorial models of solids are entirely consistent with each other, can be used interchangeably relying on continuum or combinatorial properties as needed, and can be extended to n dimensions. The key property that facilitates this consistency is that the class of closed regular subsets of ℝⁿ coincides precisely with homogeneously n-dimensional topological polyhedra. Therefore every n-dimensional solid may be unambiguously represented by its boundary and the boundary has the combinatorial structure of an n-1-dimensional polyhedron having homogeneously n-1 dimensional neighborhoods.

Solid representation schemes

Based on assumed mathematical properties, any scheme of representing solids is a method for capturing information about the class of semi-analytic subsets of Euclidean space. This means all representations are different ways of organizing the same geometric and topological data in the form of a data structure. All representation schemes are organized in terms of a finite number of operations on a set of primitives. Therefore the modeling space of any particular representation is finite, and any single representation scheme may not completely suffice to represent all types of solids. For example, solids defined via combinations of regularized boolean operations cannot necessarily be represented as the sweep of a primitive moving according to a space trajectory, except in very simple cases. This forces modern geometric modeling systems to maintain several representation schemes of solids and also facilitate efficient conversion between representation schemes.

Below is a list of common techniques used to create or represent solid models.^[4] Modern modeling software may use a combination of these schemes to represent a solid.

Parameterized primitive instancing

This scheme is based on the notion of families of objects, each member of a family distinguishable from the other by a few parameters. Each object family is called a generic primitive, and individual objects within a family are called primitive instances. For example a family of bolts is a generic primitive, and a single bolt specified by a particular set of parameters is a primitive instance. The distinguishing characteristic of pure parameterized instancing schemes is the lack of means for combining instances to create new structures which represent new and more complex objects. The other main drawback of this scheme is the difficulty of writing algorithms for computing properties of represented solids. A considerable amount of family-specific information must be built into the algorithms and therefore each generic primitive must be treated as a special case, allowing no uniform overall treatment.

Spatial occupancy enumeration

This scheme is essentially a list of spatial cells occupied by the solid. The cells, also called voxels are cubes of a fixed size and are arranged in a fixed spatial grid (other polyhedral arrangements are also possible but cubes are the simplest). Each cell may be represented by the coordinates of a single point, such as the cell’s centroid. Usually a specific scanning order is imposed and the corresponding ordered set of coordinates is called a spatial array. Spatial arrays are unambiguous and unique solid representations but are too verbose for use as ‘master’ or definitional representations. They can, however, represent coarse approximations of parts and can be used to improve the performance of geometric algorithms, especially when used in conjunction with other representations such as Constructive Solid Geometry.

Cell decomposition

This scheme follows from the combinatoric (algebraic topological) descriptions of solids detailed above. A solid can be represented by its decomposition into several cells. Spatial occupancy enumeration schemes are a particular case of cell decompositions where all the cells are cubical and lie in a regular grid. Cell decompositions provide convenient ways for computing certain topological properties of solids such as its connectedness (number of pieces) and genus (number of holes). Cell decompositions in the form of triangulations are the representations used in 3d finite elements for the numerical solution of partial differential equations. Other cell decompositions such as a Whitney regular stratification or Morse decompositions may be used for applications in robot motion planning.^[6]

Boundary representation

Main article: Boundary representation

In this scheme a solid is represented by the cellular decomposition of its boundary. Since the boundaries of solids have the distinguishing property that they separate space into regions defined by the interior of the solid and the complementary exterior according to the Jordan-Brouwer theorem discussed above, every point in space can unambiguously be tested against the solid by testing the point against the boundary of the solid. Recall that ability to test every point in the solid provides a guarantee of solidity. Using ray casting it is possible to count the number of intersections of a cast ray against the boundary of the solid. Even number of intersections correspond to exterior points, and odd number of intersections correspond to interior points. The assumption of boundaries as manifold cell complexes forces any boundary representation to obey disjointedness of distinct primitives, i.e. there are no self intersections that cause non-manifold points. In particular, the manifoldness condition implies all pairs of vertices are disjoint, pairs of edges are either disjoint or intersect at one vertex, and pairs of faces are disjoint or intersect at a common edge. Several data structures that are combinatorial maps have been developed to store boundary representations of solids. In addition to planar faces, modern systems provide the ability to store quadrics and NURBS surfaces as a part of the boundary representation. Boundary representations have evolved into a ubiquitous representation scheme of solids in most commercial geometric modelers because of their flexibility in representing solids exhibiting a high level of geometric complexity.

Constructive Solid Geometry

Main article: Constructive Solid Geometry

Constructive Solid Geometry (CSG) connotes a family of schemes for representing rigid solids as Boolean constructions or combinations of primitives via the regularized set operations discussed above. CSG and boundary representations are currently the most important representation schemes for solids. CSG representations take the form of ordered binary trees where non-terminal nodes represent either rigid transformations (orientation preserving isometries) or regularized set operations. Terminal nodes are primitive leaves that represent closed regular sets. The semantics of CSG representations is clear. Each subtree represents a set resulting from applying the indicated transformations/regularized set operations on the set represented by the primitive leaves of the subtree. CSG representations are particularly useful for capturing design intent in the form of features corresponding to material addition or removal (bosses, holes, pockets etc). The attractive properties of CSG include conciseness, guaranteed validity of solids, computationally convenient Boolean algebraic properties, and natural control of a solid’s shape in terms of high level parameters defining the solid’s primitives and their positions and orientations. The relatively simple data structure and elegant recursive algorithms have further contributed to the popularity of CSG.

Sweeping

The basic notion embodied in sweeping schemes is simple. A set moving through space may trace or sweep out volume ( a solid) that may be represented by the moving set and its trajectory. Such a representation is important in the context of applications such as detecting the material removed from a cutter as it moves along a specified trajectory, computing dynamic interference of two solids undergoing relative motion, motion planning, and even in computer graphics applications such as tracing the motions of a brush moved on a canvas. Most commercial CAD systems provide (limited) functionality for constructing swept solids mostly in the form of a two dimensional cross section moving on a space trajectory transversal to the section. However, current research has shown several approximations of three dimensional shapes moving across one parameter, and even multi-parameter motions.

Implicit representation

Main article: Function_representation

A very general method of defining a set of points X is to specify a predicate that can be evaluated at any point in space. In other words, X is defined implicitly to consist of all the points that satisfy the condition specified by the predicate. The simplest form of a predicate is the condition on the sign of a real valued function resulting in the familiar representation of sets by equalities and inequalities. For example if

f = a x + b y + c z + d

the conditions

f (p) = 0

f (p) > 0

, and

f (p) < 0

represent respectively a plane and two open linear halfspaces. More complex functional primitives may be defined by boolean combinations of simpler predicates. Furthermore, the theory of R-functions allow conversions of such representations into a single function inequality for any closed semi analytic set. Such a representation can be converted to a boundary representation using polygonization algorithms, for example, the marching cubes algorithm.

Parametric and Feature based modeling

Features are defined to be parametric shapes associated with attributes such as intrinsic geometric parameters (length, width, depth etc), position and orientation, geometric tolerances, material properties, and references to other features.^[7] Features also provide access to related production processes and resource models. Thus, features have a semantically higher level than primitive closed regular sets. Features are generally expected to form a basis for linking CAD with downstream manufacturing applications, and also for organizing databases for design data reuse.

History of Solid Modelers

The historical development of solid modelers has to be seen in context of the whole history of CAD, the key milestones being the development of the research system BUILD followed by its commercial spin-off Romulus which went on to influence the development of Parasolid, ACIS and Solid Modeling Solutions. Other contributions came from Mäntylä, with his GWB and from the GPM project which contributed, among other things, hybrid modeling techniques at the beginning of the 1980s.

Computer aided design

Main article: Computer-aided design

Solid modelers have become commonplace in engineering departments in the last ten years due to faster computers and competitive software pricing. Solid modeling software creates a virtual 3D representation of components for machine design and analysis.^[8] A typical graphical user interface includes programmable macros, keyboard shortcuts and dynamic model manipulation. The ability to dynamically re-orient the model, in real-time shaded 3-D, is emphasized and helps the designer maintain a mental 3-D image.

Creation of a solid model in NX

A solid part model generally consists of a group of features, added one at a time, until the model is complete. Engineering solid models are built mostly with sketcher-based features; 2-D sketches that are swept along a path to become 3-D. These may be cuts, or extrusions for example.

Design work on components is usually done within the context of the whole product using assembly modeling methods. An assembly model incorporates references to individual part models that comprise the product.^[9]

Another type of modeling technique is ‘surfacing’ (Freeform surface modeling). Here, surfaces are defined, trimmed and merged, and filled to make solid. The surfaces are usually defined with datum curves in space and a variety of complex commands. Surfacing is more difficult, but better applicable to some manufacturing techniques, like injection molding. Solid models for injection molded parts usually have both surfacing and sketcher based features.

Engineering drawings are created semi-automatically and reference the solid models.

The learning curve for these software packages is steep, but a fluent machine designer who can master these software packages is highly productive.

The modeling of solids is only the minimum requirement of a CAD system’s capabilities.

Parametric modeling uses parameters to define a model (dimensions, for example). The parameter may be modified later, and the model will update to reflect the modification. Typically, there is a relationship between parts, assemblies, and drawings. A part consists of multiple features, and an assembly consists of multiple parts. Drawings can be made from either parts or assemblies.

Example: A shaft is created by extruding a circle 100 mm. A hub is assembled to the end of the shaft. Later, the shaft is modified to be 200 mm long (click on the shaft, select the length dimension, modify to 200). When the model is updated the shaft will be 200 mm long, the hub will relocate to the end of the shaft to which it was assembled, and the engineering drawings and mass properties will reflect all changes automatically.

Examples of parameters are: dimensions used to create model features, material density, formulas to describe swept features, imported data (that describe a reference surface, for example).

Related to parameters, but slightly different are Constraints. Constraints are relationships between entities that make up a particular shape. For a window, the sides might be defined as being parallel, and of the same length.

Parametric modeling is obvious and intuitive. But for the first three decades of CAD this was not the case. Modification meant re-draw, or add a new cut or protrusion on top of old ones. Dimensions on engineering drawings were created, instead of shown.

Parametric modeling is very powerful, but requires more skill in model creation. A complicated model for an injection molded part may have a thousand features, and modifying an early feature may cause later features to fail. Skillfully created parametric models are easier to maintain and modify.

Parametric modeling also lends itself to data re-use. A whole family of capscrews can be contained in one model, for example.

Entertainment

Animation of computer generated characters is, technically, an example of parametric modeling, though few in the industry would consider it to be.^{[original research?]} Characters’ skin is modeled with NURBS patches and stitched together or polygon modeled. The skin of characters is then parametrically associated to a skeleton within characters (with many characters’ skins now being driven by muscle simulation systems). The skeleton of a character is rotated into poses, which parametrically drives the shape of the characters’ skin for each frame to create animation.

Medical solid modeling

Modern computed axial tomography and magnetic resonance imaging scanners can be used to create solid models of internal body features, so-called volume rendering. Optical 3D scanners can be used to create point clouds or polygon mesh models of external body features.

Uses of medical solid modeling;

Visualization
Visualization of specific body tissues (just blood vessels and tumor, for example)
Designing prosthetics, orthotics, and other medical and dental devices (this is sometimes called mass customization)
Creating polygon mesh models for rapid prototyping (to aid surgeons preparing for difficult surgeries, for example)
Combining polygon mesh models with CAD solid modeling (design of hip replacement parts, for example)
Computational analysis of complex biological processes, e.g. air flow, blood flow
Computational simulation of new medical devices and implants in vivo

If the use goes beyond visualization of the scan data, processes like image segmentation and image-based meshing will be necessary to generate an accurate and realistic geometrical description of the scan data.

Engineering

Mass properties window of a model in Cobalt

Because CAD programs running on computers “understand” the true geometry comprising complex shapes, many attributes of for a 3‑D solid, such as its center of gravity, volume, and mass, can be quickly calculated. For instance, the cube shown at the top of this article measures 8.4 mm from flat to flat. Despite its many radii and the shallow pyramid on each of its six faces, its properties are readily calculated for the designer, as shown in in the screenshot at right.

References

^ ^a ^b Shapiro, Vadim (2001). Solid Modeling. Elsevier. http://sal-cnc.me.wisc.edu/index.php?option=com_remository&Itemid=143&func=fileinfo&id=53. Retrieved 20 April 2010.
^ Requicha, A.A.G and Voelcker, H. (1983). Solid Modeling: Current Status and Research Directions. IEEE Computer Graphics. http://www.computer.org/portal/web/csdl/doi/10.1109/MCG.1983.263271. Retrieved 20 April 2010.
^ Tilove, R.B. and Requicha, A.A.G (1980). Closure of Boolean operations on geometric entities. Computer Aided Design. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TYR-481DX38-P3&_user=443835&_coverDate=09/30/1980&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1307947802&_rerunOrigin=scholar.google&_acct=C000020958&_version=1&_urlVersion=0&_userid=443835&md5=746253db42dc581e1d64d396ed605799. Retrieved 20 April 2010.
^ ^a ^b Requicha, A.A.G. (1980). Representations for Rigid Solids: Theory, Methods, and Systems. ACM Computing Surveys. http://portal.acm.org/citation.cfm?id=356833&dl=. Retrieved 20 April 2010.
^ Hatcher, A. (2002). Algebraic Topology. Cambridge University Press. http://www.math.cornell.edu/~hatcher/AT/ATpage.html. Retrieved 20 April 2010.
^ Canny, John F. (1987). The Complexity of Robot Motion Planning. MIT press, ACM doctoral dissertation award. http://mitpress.mit.edu/catalog/item/default.asp?tid=4749&ttype=2. Retrieved 20 April 2010.
^ Mantyla, M., Nau, D. , and Shah, J. (1996). Challenges in feature based manufacturing research. Communications of the ACM. http://portal.acm.org/citation.cfm?id=230808. Retrieved 20 April 2010.
^ LaCourse, Donald (1995). “2″. Handbook of Solid Modeling. McGraw Hill. pp. 2.5. ISBN 0-07-035788-9.
^ LaCourse, Donald (1995). “11″. Handbook of Solid Modeling. McGraw Hill. pp. 111.2. ISBN 0-07-035788-9.

External links

This information originally retrieved from http://en.wikipedia.org/wiki/Solid_modeling
on Wednesday 24th August 2011 12:37 pm EDT
Now edited and maintained by ManufacturingET.org

Single Point Cutting Tools

7:01 pm | August 12, 2011

Author: ManufacturingET.org | Category: Machining Manufacturing | Tags: Cutting Tool | Comments: None

ManufacturingET.org > 2011 > August

Images of Single Point Cutting Tools

Images of single point tool being used on a lathe

CAD Model of Single Point Cutting Tool (exported to dwg)

CAD Model of Single Point Cutting Tool (Native NX7)

ANSI standard B94.50

Back rake angle
Side rake angle
End relief angle
Side relief angle
End cutting edge angle
Side cutting edge angle
Nose radius

Rake Face

Surface the chip flows across

Flank

Surface that forms the outer boundary of the wedge

Rake Angle

Angle between the tool face and a line perpendicular to the cut workpiece surface

Clearance (relief) Angle

Angle between the tool flank and the workpiece

ANSI Tool Signature

Project Management

7:07 pm | August 11, 2011

Author: ManufacturingET.org | Category: Engineering Design Manufacturing | Tags: Project Management | Comments: None

ManufacturingET.org > 2011 > August

Project management is the discipline of planning, organizing, securing and managing resources to bring about the successful completion of specific project goals and objectives.

A project is a temporary endeavor, having a defined beginning and end (usually constrained by date, but can be by funding or deliverables),^[1] undertaken to meet unique goals and objectives,^[2] usually to bring about beneficial change or added value. The temporary nature of projects stands in contrast to business as usual (or operations),^[3] which are repetitive, permanent or semi-permanent functional work to produce products or services. In practice, the management of these two systems is often found to be quite different, and as such requires the development of distinct technical skills and the adoption of separate management.

The primary challenge of project management is to achieve all of the project goals^[4] and objectives while honoring the preconceived project constraints.^[5] Typical constraints are scope, time, and budget.^[1] The secondary—and more ambitious—challenge is to optimize the allocation and integration of inputs necessary to meet pre-defined objectives.

History

Roman Soldiers Building a Fortress, Trajan’s Column 113 AD

Project management has been practiced since early civilization. Until 1900 civil engineering projects were generally managed by creative architects, engineers, and master builders themselves, among those for example Vitruvius (1st century BC), Christopher Wren (1632–1723) , Thomas Telford (1757–1834) and Isambard Kingdom Brunel (1806–1859).^[6] It was in the 1950s that organizations started to systematically apply project management tools and techniques to complex engineering projects.^[7]

Henry Gantt (1861-1919), the father of planning and control techniques.

As a discipline, Project Management developed from several fields of application including civil construction, engineering, and heavy defense activity.^[8] Two forefathers of project management are Henry Gantt, called the father of planning and control techniques,^[9] who is famous for his use of the Gantt chart as a project management tool; and Henri Fayol for his creation of the 5 management functions which form the foundation of the body of knowledge associated with project and program management.^[10] Both Gantt and Fayol were students of Frederick Winslow Taylor‘s theories of scientific management. His work is the forerunner to modern project management tools including work breakdown structure (WBS) and resource allocation.

The 1950s marked the beginning of the modern Project Management era where core engineering fields come together working as one. Project management became recognized as a distinct discipline arising from the management discipline with engineering model.^[11] In the United States, prior to the 1950s, projects were managed on an ad hoc basis using mostly Gantt Charts, and informal techniques and tools. At that time, two mathematical project-scheduling models were developed. The “Critical Path Method” (CPM) was developed as a joint venture between DuPont Corporation and Remington Rand Corporation for managing plant maintenance projects. And the “Program Evaluation and Review Technique” or PERT, was developed by Booz Allen Hamilton as part of the United States Navy‘s (in conjunction with the Lockheed Corporation) Polaris missile submarine program;^[12] These mathematical techniques quickly spread into many private enterprises.

PERT network chart for a seven-month project with five milestones

At the same time, as project-scheduling models were being developed, technology for project cost estimating, cost management, and engineering economics was evolving, with pioneering work by Hans Lang and others. In 1956, the American Association of Cost Engineers (now AACE International; the Association for the Advancement of Cost Engineering) was formed by early practitioners of project management and the associated specialties of planning and scheduling, cost estimating, and cost/schedule control (project control). AACE continued its pioneering work and in 2006 released the first integrated process for portfolio, program and project management (Total Cost Management Framework).

The International Project Management Association (IPMA) was founded in Europe in 1967,^[13] as a federation of several national project management associations. IPMA maintains its federal structure today and now includes member associations on every continent except Antarctica. IPMA offers a Four Level Certification program based on the IPMA Competence Baseline (ICB).^[14] The ICB covers technical competences, contextual competences, and behavioral competences.

In 1969, the Project Management Institute (PMI) was formed in the USA.^[15] PMI publishes A Guide to the Project Management Body of Knowledge (PMBOK Guide), which describes project management practices that are common to “most projects, most of the time.” PMI also offers multiple certifications.

Approaches

There are a number of approaches to managing project activities including agile, interactive, incremental, and phased approaches.

Regardless of the methodology employed, careful consideration must be given to the overall project objectives, timeline, and cost, as well as the roles and responsibilities of all participants and stakeholders.

The traditional approach

A traditional phased approach identifies a sequence of steps to be completed. In the “traditional approach”, we can distinguish 5 components of a project (4 stages plus control) in the development of a project:

Typical development phases of an engineering project

Project initiation stage;
Project planning and design stage;
Project execution and construction stage;
Project monitoring and controlling systems;
Project completion.

Not all the projects will visit every stage as projects can be terminated before they reach completion. Some projects do not follow a structured planning and/or monitoring stages. Some projects will go through steps 2, 3 and 4 multiple times.

Many industries use variations on these project stages. For example, when working on a brick and mortar design and construction, projects will typically progress through stages like Pre-Planning, Conceptual Design, Schematic Design, Design Development, Construction Drawings (or Contract Documents), and Construction Administration. In software development, this approach is often known as the waterfall model,^[16] i.e., one series of tasks after another in linear sequence. In software development many organizations have adapted the Rational Unified Process (RUP) to fit this methodology, although RUP does not require or explicitly recommend this practice. Waterfall development works well for small, well defined projects, but often fails in larger projects of undefined and ambiguous nature. The Cone of Uncertainty explains some of this as the planning made on the initial phase of the project suffers from a high degree of uncertainty. This becomes especially true as software development is often the realization of a new or novel product. In projects where requirements have not been finalized and can change, requirements management is used to develop an accurate and complete definition of the behavior of software that can serve as the basis for software development.^[17] While the terms may differ from industry to industry, the actual stages typically follow common steps to problem solving — “defining the problem, weighing options, choosing a path, implementation and evaluation.”

Critical Chain Project Management

Critical Chain Project Management (CCPM) is a method of planning and managing projects that puts more emphasis on the resources (physical and human) needed in order to execute project tasks. The most complex part involves engineering professionals of different fields (Civil, Electrical, Mechanical etc.) working together. It is an application of the Theory of Constraints (TOC) to projects. The goal is to increase the rate of throughput (or completion rates) of projects in an organization. Applying the first three of the five focusing steps of TOC, the system constraint for all projects is identified as are the resources. To exploit the constraint, tasks on the critical chain are given priority over all other activities. Finally, projects are planned and managed to ensure that the resources are ready when the critical chain tasks must start, subordinating all other resources to the critical chain.

Regardless of project type, the project plan should undergo Resource Leveling, and the longest sequence of resource-constrained tasks should be identified as the critical chain. In multi-project environments, resource leveling should be performed across projects. However, it is often enough to identify (or simply select) a single “drum” resource—a resource that acts as a constraint across projects—and stagger projects based on the availability of that single resource.

Planning and feedback loops in Extreme Programming (XP) with the time frames of the multiple loops.

Extreme Project Management

In critical studies of project management it has been noted that several PERT based models are not well suited for the multi-project company environment of today.^{[citation needed]} Most of them are aimed at very large-scale, one-time, non-routine projects, and currently all kinds of management are expressed in terms of projects.

Using complex models for “projects” (or rather “tasks”) spanning a few weeks has been proven to cause unnecessary costs and low maneuverability in several cases^{[citation needed]}. Instead, project management experts try to identify different “lightweight” models, such as Agile Project Management methods including Extreme Programming for software development and Scrum techniques.

The generalization of Extreme Programming to other kinds of projects is extreme project management, which may be used in combination with the process modeling and management principles of human interaction management.

Event chain methodology

Event chain methodology is another method that complements critical path method and critical chain project management methodologies.

Event chain methodology is an uncertainty modeling and schedule network analysis technique that is focused on identifying and managing events and event chains that affect project schedules. Event chain methodology helps to mitigate the negative impact of psychological heuristics and biases, as well as to allow for easy modeling of uncertainties in the project schedules. Event chain methodology is based on the following principles.

Probabilistic moment of risk: An activity (task) in most real life processes is not a continuous uniform process. Tasks are affected by external events, which can occur at some point in the middle of the task.
Event chains: Events can cause other events, which will create event chains. These event chains can significantly affect the course of the project. Quantitative analysis is used to determine a cumulative effect of these event chains on the project schedule.
Critical events or event chains: The single events or the event chains that have the most potential to affect the projects are the “critical events” or “critical chains of events.” They can be determined by the analysis.
Project tracking with events: Even if a project is partially completed and data about the project duration, cost, and events occurred is available, it is still possible to refine information about future potential events and helps to forecast future project performance.
Event chain visualization: Events and event chains can be visualized using event chain diagrams on a Gantt chart.

The PRINCE2 process model

PRINCE2

PRINCE2 is a structured approach to project management, released in 1996 as a generic project management method.^[18] It combined the original PROMPT methodology (which evolved into the PRINCE methodology) with IBM’s MITP (managing the implementation of the total project) methodology. PRINCE2 provides a method for managing projects within a clearly defined framework. PRINCE2 describes procedures to coordinate people and activities in a project, how to design and supervise the project, and what to do if the project has to be adjusted if it does not develop as planned.

In the method, each process is specified with its key inputs and outputs and with specific goals and activities to be carried out. This allows for automatic control of any deviations from the plan. Divided into manageable stages, the method enables an efficient control of resources. On the basis of close monitoring, the project can be carried out in a controlled and organized way.

PRINCE2 provides a common language for all participants in the project. The various management roles and responsibilities involved in a project are fully described and are adaptable to suit the complexity of the project and skills of the organization.

Capability Maturity Model, predecessor of the CMMI Model

Process-based management

Also furthering the concept of project control is the incorporation of process-based management. This area has been driven by the use of Maturity models such as the CMMI (Capability Maturity Model Integration) and ISO/IEC15504 (SPICE – Software Process Improvement and Capability Estimation).

Agile Project Management

Agile Project Management approaches based on the principles of human interaction management are founded on a process view of human collaboration. This contrasts sharply with the traditional approach. In the agile software development or flexible product development approach, the project is seen as a series of relatively small tasks conceived and executed as the situation demands in an adaptive manner, rather than as a completely pre-planned process.

Processes

Traditionally, project management includes a number of elements: four to five process groups, and a control system. Regardless of the methodology or terminology used, the same basic project management processes will be used.

The project development stages^[19]

Major process groups generally include^[20]:

Initiation
Planning or development
Production or execution
Monitoring and controlling
Closing

In project environments with a significant exploratory element (e.g., Research and development), these stages may be supplemented with decision points (go/no go decisions) at which the project’s continuation is debated and decided. An example is the Stage-Gate model.

Initiating

Initiating Process Group Processes^[19]

The initiating processes determine the nature and scope of the project.^[21] If this stage is not performed well, it is unlikely that the project will be successful in meeting the business’ needs. The key project controls needed here are an understanding of the business environment and making sure that all necessary controls are incorporated into the project. Any deficiencies should be reported and a recommendation should be made to fix them.

The initiating stage should include a plan that encompasses the following areas:

Analyzing the business needs/requirements in measurable goals
Reviewing of the current operations
Financial analysis of the costs and benefits including a budget
Stakeholder analysis, including users, and support personnel for the project
Project charter including costs, tasks, deliverables, and schedule

Planning and design

Planning Process Group Activities^[19]

After the initiation stage, the project is planned to an appropriate level of detail. The main purpose is to plan time, cost and resources adequately to estimate the work needed and to effectively manage risk during project execution. As with the Initiation process group, a failure to adequately plan greatly reduces the project’s chances of successfully accomplishing its goals.

Project planning generally consists of^[22]

determining how to plan (e.g. by level of detail or rolling wave);
developing the scope statement;
selecting the planning team;
identifying deliverables and creating the work breakdown structure;
identifying the activities needed to complete those deliverables and networking the activities in their logical sequence;
estimating the resource requirements for the activities;
estimating time and cost for activities;
developing the schedule;
developing the budget;
risk planning;
gaining formal approval to begin work.

Additional processes, such as planning for communications and for scope management, identifying roles and responsibilities, determining what to purchase for the project and holding a kick-off meeting are also generally advisable.

For new product development projects, conceptual design of the operation of the final product may be performed concurrent with the project planning activities, and may help to inform the planning team when identifying deliverables and planning activities.

Executing

Executing Process Group Processes^[19]

Executing consists of the processes used to complete the work defined in the project plan to accomplish the project’s requirements. Execution process involves coordinating people and resources, as well as integrating and performing the activities of the project in accordance with the project management plan. The deliverables are produced as outputs from the processes performed as defined in the project management plan and other frameworks that might be applicable to the type of project at hand.

Monitoring and controlling

Monitoring and controlling consists of those processes performed to observe project execution so that potential problems can be identified in a timely manner and corrective action can be taken, when necessary, to control the execution of the project. The key benefit is that project performance is observed and measured regularly to identify variances from the project management plan.

Monitoring and Controlling Process Group Processes^[19]

Monitoring and Controlling includes:^[23]

Measuring the ongoing project activities (‘where we are’);
Monitoring the project variables (cost, effort, scope, etc.) against the project management plan and the project performance baseline (where we should be);
Identify corrective actions to address issues and risks properly (How can we get on track again);
Influencing the factors that could circumvent integrated change control so only approved changes are implemented

In multi-phase projects, the monitoring and control process also provides feedback between project phases, in order to implement corrective or preventive actions to bring the project into compliance with the project management plan.

Project Maintenance is an ongoing process, and it includes:^[20]

Continuing support of end users
Correction of errors
Updates of the software over time

Monitoring and Controlling cycle

In this stage, auditors should pay attention to how effectively and quickly user problems are resolved.

Over the course of any construction project, the work scope may change. Change is a normal and expected part of the construction process. Changes can be the result of necessary design modifications, differing site conditions, material availability, contractor-requested changes, value engineering and impacts from third parties, to name a few. Beyond executing the change in the field, the change normally needs to be documented to show what was actually constructed. This is referred to as Change Management. Hence, the owner usually requires a final record to show all changes or, more specifically, any change that modifies the tangible portions of the finished work. The record is made on the contract documents – usually, but not necessarily limited to, the design drawings. The end product of this effort is what the industry terms as-built drawings, or more simply, “as built.” The requirement for providing them is a norm in construction contracts.

When changes are introduced to the project, the viability of the project has to be re-assessed. It is important not to lose sight of the initial goals and targets of the projects. When the changes accumulate, the forecasted result may not justify the original proposed investment in the project.

Closing

Closing Process Group Processes.^[19]

Closing includes the formal acceptance of the project and the ending thereof. Administrative activities include the archiving of the files and documenting lessons learned.

This phase consists of:^[20]

Project close: Finalize all activities across all of the process groups to formally close the project or a project phase
Contract closure: Complete and settle each contract (including the resolution of any open items) and close each contract applicable to the project or project phase.

Project controlling and Project control systems

Project controlling should be established as an independent function in project management. It implements verification and controlling function during the processing of a project in order to reinforce the defined performance and formal goals.^[24] The tasks of project controlling are also:

creation of infrastructure for the supply of the right information and its update
establishment of a way to communicate disparities of project parameters
development of project information technology based on an intranet or the determination of a project key performance index system (KPI)
divergence analyses and generation of proposals for potential project regulations^[25]
the establishment of methods to accomplish an appropriate the project structure, project workflow organization, project control and governance
creation of transparency among the project parameters^[26]

Fulfillment and implementation of these tasks can be achieved by applying specific methods and instruments of project controlling. The following methods of project controlling can be applied:

investment analysis
cost-benefit analyses
value benefit Analysis
expert surveys
simulation calculations
risk profile analyses
surcharge calculations
milestone trend analysis
cost trend analysis
target/actual-comparison^[27]

Project control is that element of a project that keeps it on-track, on-time and within budget.^[23] Project control begins early in the project with planning and ends late in the project with post-implementation review, having a thorough involvement of each step in the process. Each project should be assessed for the appropriate level of control needed: too much control is too time consuming, too little control is very risky. If project control is not implemented correctly, the cost to the business should be clarified in terms of errors, fixes, and additional audit fees.

Control systems are needed for cost, risk, quality, communication, time, change, procurement, and human resources. In addition, auditors should consider how important the projects are to the financial statements, how reliant the stakeholders are on controls, and how many controls exist. Auditors should review the development process and procedures for how they are implemented. The process of development and the quality of the final product may also be assessed if needed or requested. A business may want the auditing firm to be involved throughout the process to catch problems earlier on so that they can be fixed more easily. An auditor can serve as a controls consultant as part of the development team or as an independent auditor as part of an audit.

Businesses sometimes use formal systems development processes. These help assure that systems are developed successfully. A formal process is more effective in creating strong controls, and auditors should review this process to confirm that it is well designed and is followed in practice. A good formal systems development plan outlines:

A strategy to align development with the organization’s broader objectives
Standards for new systems
Project management policies for timing and budgeting
Procedures describing the process
Evaluation of quality of change

Topics

Project managers

A project manager is a professional in the field of project management. Project managers can have the responsibility of the planning, execution, and closing of any project, typically relating to construction industry, engineering, architecture, computing, or telecommunications. Many other fields in the production engineering and design engineering and heavy industrial also have project managers.

A project manager is the person accountable for accomplishing the stated project objectives. Key project management responsibilities include creating clear and attainable project objectives, building the project requirements, and managing the triple constraint for projects, which is cost, time, and scope.

A project manager is often a client representative and has to determine and implement the exact needs of the client, based on knowledge of the firm they are representing. The ability to adapt to the various internal procedures of the contracting party, and to form close links with the nominated representatives, is essential in ensuring that the key issues of cost, time, quality and above all, client satisfaction, can be realized.

Project management triangle

The project management triangle.

Like any human undertaking, projects need to be performed and delivered under certain constraints. Traditionally, these constraints have been listed as “scope,” “time,” and “cost”.^[1] These are also referred to as the “project management triangle“, where each side represents a constraint. One side of the triangle cannot be changed without affecting the others. A further refinement of the constraints separates product “quality” or “performance” from scope, and turns quality into a fourth constraint.

The time constraint refers to the amount of time available to complete a project. The cost constraint refers to the budgeted amount available for the project. The scope constraint refers to what must be done to produce the project’s end result. These three constraints are often competing constraints: increased scope typically means increased time and increased cost, a tight time constraint could mean increased costs and reduced scope, and a tight budget could mean increased time and reduced scope.

The discipline of project management is about providing the tools and techniques that enable the project team (not just the project manager) to organize their work to meet these constraints.

Work breakdown structure

Example of a work breakdown structure applied in a NASA reporting structure.^[28]

The work breakdown structure (WBS) is a tree structure, which shows a subdivision of effort required to achieve an objective; for example a program, project, and contract. The WBS may be hardware, product, service, or process oriented.

A WBS can be developed by starting with the end objective and successively subdividing it into manageable components in terms of size, duration, and responsibility (e.g., systems, subsystems, components, tasks, subtasks, and work packages), which include all steps necessary to achieve the objective.^[17]

The work breakdown structure provides a common framework for the natural development of the overall planning and control of a contract and is the basis for dividing work into definable increments from which the statement of work can be developed and technical, schedule, cost, and labor hour reporting can be established.^[28]

Project Management Framework

Example of an IT Project Management Framework.^[19]

The Program (Investment) Life Cycle integrates the project management and system development life cycles with the activities directly associated with system deployment and operation. By design, system operation management and related activities occur after the project is complete and are not documented within this guide.^[19]

For example, see figure, in the US United States Department of Veterans Affairs (VA) the program management life cycle is depicted and describe in the overall VA IT Project Management Framework to address the integration of OMB Exhibit 300 project (investment) management activities and the overall project budgeting process. The VA IT Project Management Framework diagram illustrates Milestone 4 which occurs following the deployment of a system and the closing of the project. The project closing phase activities at the VA continues through system deployment and into system operation for the purpose of illustrating and describing the system activities the VA considers part of the project. The figure illustrates the actions and associated artifacts of the VA IT Project and Program Management process.^[19]

International standards

There have been several attempts to develop Project Management standards, such as:

Capability Maturity Model from the Software Engineering Institute.
GAPPS, Global Alliance for Project Performance Standards- an open source standard describing COMPETENCIES for project and program managers.
A Guide to the Project Management Body of Knowledge
HERMES method, Swiss general project management method, selected for use in Luxembourg and international organizations.
The ISO standards ISO 9000, a family of standards for quality management systems, and the ISO 10006:2003, for Quality management systems and guidelines for quality management in projects.
PRINCE2, PRojects IN Controlled Environments.
Team Software Process (TSP) from the Software Engineering Institute.
Total Cost Management Framework, AACE International’s Methodology for Integrated Portfolio, Program and Project Management)
V-Model, an original systems development method.
The Logical framework approach, which is popular in international development organizations.
IAPPM, The International Association of Project & Program Management, guide to Project Auditing and Rescuing Troubled Projects.

Project portfolio management

An increasing number of organizations are using, what is referred to as, project portfolio management (PPM) as a means of selecting the right projects and then using project management techniques^[29] as the means for delivering the outcomes in the form of benefits to the performing private or not-for-profit organization.

References

^ ^a ^b ^c Chatfield, Carl. “A short course in project management”. Microsoft. http://office.microsoft.com/en-us/project/HA102354821033.aspx.
^ *The Definitive Guide to Project Management. Nokes, Sebastian. 2nd Ed.n. London (Financial Times / Prentice Hall): 2007. ISBN 978 0 273 71097 4
^ Paul C. Dinsmore et al (2005) The right projects done right! John Wiley and Sons, 2005. ISBN 0-7879-7113-8. p.35 and further.
^ Lewis R. Ireland (2006) Project Management. McGraw-Hill Professional, 2006. ISBN 0-07-147160-X. p.110.
^ Joseph Phillips (2003). PMP Project Management Professional Study Guide. McGraw-Hill Professional, 2003. ISBN 0-07-223062-2 p.354.
^ Dennis Lock (2007) Project management (9e ed.) Gower Publishing, Ltd., 2007. ISBN 0-566-08772-3
^ Young-Hoon Kwak (2005). “A brief history of Project Management”. In: The story of managing projects. Elias G. Carayannis et al. (9 eds), Greenwood Publishing Group, 2005. ISBN 1-56720-506-2
^ David I. Cleland, Roland Gareis (2006). Global project management handbook. “Chapter 1: “The evolution of project management”. McGraw-Hill Professional, 2006. ISBN 0-07-146045-4
^ Martin Stevens (2002). Project Management Pathways. Association for Project Management. APM Publishing Limited, 2002 ISBN 1-903494-01-X p.xxii
^ Morgen Witzel (2003). Fifty key figures in management‎. Routledge, 2003. ISBN 0-415-36977-0. p. 96-101.
^ David I. Cleland, Roland Gareis (2006). Global project management handbook. McGraw-Hill Professional, 2006. ISBN 0-07-146045-4. p.1-4 states: “It was in the 1950s when project management was formally recognized as a distinct contribution arising from the management discipline.“
^ Booz Allen Hamilton – History of Booz Allen 1950s
^ Bjarne Kousholt (2007). Project Management‎ –. Theory and practice.. Nyt Teknisk Forlag. ISBN 87-571-2603-8. p.59.
^ http://www.ipma.ch/publication/Pages/ICB-IPMACompetenceBaseline.aspx
^ F. L. Harrison, Dennis Lock (2004). Advanced project management: a structured approach‎. Gower Publishing, Ltd., 2004. ISBN 0-566-07822-8. p.34.
^ Winston W. Royce (1970).
“Managing the Development of Large Software Systems”
in: In: Technical Papers of Western Electronic Show and Convention (WesCon) August 25–28, 1970, Los Angeles, USA.
^ ^a ^b Stellman, Andrew; Greene, Jennifer (2005). Applied Software Project Management. O’Reilly Media. ISBN 978-0-596-00948-9. http://www.stellman-greene.com/aspm/.
^ OGC – PRINCE2 – Background
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ VA Office of Information and Technology (2003)
Project Management Guide
US DEPARTMENT OF VETERANS AFFAIRS. March 3, 2005.
^ ^a ^b ^c PMI (2010). A Guide to the Project Management Body of Knowledge p.27-35
^ Peter Nathan, Gerald Everett Jones (2003). PMP certification for dummies. p.63.
^ Harold Kerzner (2003). Project Management: A Systems Approach to Planning, Scheduling, and Controlling (8th Ed. ed.). Wiley. ISBN 0-471-22577-0.
^ ^a ^b James P. Lewis (2000). The project manager’s desk reference: : a comprehensive guide to project planning, scheduling, evaluation, and systems. p.185
^ Jörg Becker, Martin Kugeler, Michael Rosemann (2003). Process management: a guide for the design of business processes. ISBN-13: 978-3540434993. p.27.
^ Bernhard Schlagheck (2000). Objektorientierte Referenzmodelle für das Prozess- und Projektcontrolling. Grundlagen – Konstruktionen – Anwendungsmöglichkeiten. ISBN-13: 978-3824471621. p.131.
^ Josef E. Riedl (1990). Projekt – Controlling in Forschung und Entwicklung. ISBN: 9783540519638. p.99.
^ Steinle, Bruch, Lawa (1995). Projektmanagement. FAZ Verlagsbereich Wirtschaftsbücher. p.136-143
^ ^a ^b NASA (2001). NASA NPR 9501.2D. May 23, 2001.
^ Albert Hamilton (2004). Handbook of Project Management Procedures. TTL Publishing, Ltd. ISBN 0-7277-3258-7

External links

Wikimedia Commons has media related to: Project management

Guidelines for Managing Projects
from the UK Department for Business, Enterprise and Regulatory Reform (BERR)
Max Wideman’s “Open Source” Comparative Glossary of Project Management Terms
Open Source Project Management manual

Software engineering

Fields

Requirements analysis • Systems analysis • Software design • Computer programming • Formal methods • Software testing • Software deployment • Software maintenance

Concepts

Data modeling • Enterprise architecture • Functional specification • Modeling language • Programming paradigm • Software • Software architecture • Software development methodology • Software development process • Software quality • Software quality assurance • Software archaeology • Structured analysis

Orientations

Agile • Aspect-oriented • Object orientation • Ontology • Service orientation • SDLC

Models

Development models	Agile • Iterative model • RUP • Scrum • Spiral model • Waterfall model • XP • V-Model • Incremental model • Prototype model

Other models	Automotive SPICE • CMMI • Data model • Function model • Information model • Metamodeling • Object model • Systems model • View model

Modeling languages	IDEF • UML

Softwareengineers

Kent Beck • Grady Booch • Fred Brooks • Barry Boehm • Ward Cunningham • Ole-Johan Dahl • Tom DeMarco • Martin Fowler • C. A. R. Hoare • Watts Humphrey • Michael A. Jackson • Ivar Jacobson • Craig Larman • James Martin • Bertrand Meyer • David Parnas • Winston W. Royce • Colette Rolland • James Rumbaugh • Niklaus Wirth • Edward Yourdon • Victor Basili

Related fields

Computer science • Computer engineering • Enterprise engineering • History • Management • Project management • Quality management • Software ergonomics • Systems engineering

This information originally retrieved from http://en.wikipedia.org/wiki/Project_Management
on Thursday 11th August 2011 3:07 pm EDT
Now edited and maintained by ManufacturingET.org

Product Management

7:06 pm |

Author: ManufacturingET.org | Category: Engineering Design Manufacturing | Tags: Product Management | Comments: None

ManufacturingET.org > 2011 > August

Product management is an organizational lifecycle function within a company dealing with the planning or forecasting or marketing of a product or products at all stages of the product lifecycle.

Product development (inbound-focused) and product marketing (outbound-focused) are different yet complementary efforts with the objective of maximizing sales revenues, market share, and profit margins. The role of product management spans many activities from strategic to tactical and varies based on the organizational structure of the company. Product management can be a function separate on its own and a member of marketing or engineering.

While involved with the entire product lifecycle, product management’s main focus is on driving new product development. According to the Product Development and Management Association (PDMA), superior and differentiated new products — ones that deliver unique benefits and superior value to the customer — is the number one driver of success and product profitability.^[1]

Aspects of product Depending on the company size and history, product management has a variety of functions and roles. Sometimes there is a product manager, and sometimes the role of product manager is shared by other roles. Frequently there is Profit and Loss (P&L) responsibility as a key metric for evaluating product manager performance. In some companies, the product management function is the hub of many other activities around the product. In others, it is one of many things that need to happen to bring a product to market and actively monitor and manage it in-market.

Product management often serves an inter-disciplinary role, bridging gaps within the company between teams of different expertise, most notably between engineering-oriented teams and commercial-oriented teams. For example product managers often translate business objectives set for a product by Marketing or Sales into engineering requirements. Conversely they may work to explain the capabilities and limitations of the finished product back to Marketing and Sales. Product Managers may also have one or more direct reports who manage operational tasks and/or a Change Manager who can oversee new initiatives.

1 Product development
2 Product marketing
3 See also
4 References
5 External links

Product development

Identifying new product candidates
Gathering the Voice of customer
Defining product requirements
Determine business-case and feasibility
Scoping and defining new products at high level
Evangelizing new products within the company
Building product roadmaps, particularly Technology roadmaps
Developing all products on schedule, working to a critical path
Ensuring products are within optimal price margins and up to specifications

Product marketing

Product Life Cycle considerations
Product differentiation
Product naming and branding
7 functions of marketing
Product positioning and outbound messaging
Promoting the product externally with press, customers, and partners
Conduct customer feedback and enabling (pre-production, beta software)
Launching new products to market
Monitoring the competition

References

^ Kahn, Kenneth B. (Editor). The PDMA Handbook of New Product Development. Second Edition. Hoboken, NJ: John Wiley & Sons, 2005. ISBN 0-471-48524-1

External links

This information originally retrieved from http://en.wikipedia.org/wiki/Product_management
on Thursday 11th August 2011 3:04 pm EDT
Now edited and maintained by ManufacturingET.org

Concurrent Engineering

6:53 pm |

Author: ManufacturingET.org | Category: Engineering Design | Tags: Concurrent Design, PLM | Comments: None

ManufacturingET.org > 2011 > August

Concurrent engineering is a work methodology based on the parallelization of tasks (i.e. performing tasks concurrently). It refers to an approach used in product development in which functions of design engineering, manufacturing engineering and other functions are integrated to reduce the elapsed time required to bring a new product to the market.

1 Introduction
2 Concurrent engineering elements
3 Definition
4 Using C.E.
5 See also
6 References

Introduction

The concurrent engineering method is still a relatively new design management system, but has had the opportunity to mature in recent years to become a well-defined systems approach towards optimizing engineering design cycles.^[1] Because of this, concurrent engineering has gathered much attention from industry and has been implemented in a multitude of companies, organizations and universities, most notably in the aerospace industry.

The basic premise for concurrent engineering revolves around two concepts. The first is the idea that all elements of a product’s life-cycle, from functionality, producibility, assembly, testability, maintenance issues, environmental impact and finally disposal and recycling, should be taken into careful consideration in the early design phases.^[2]

The second concept is that the preceding design activities should all be occurring at the same time, or concurrently. The overall goal being that the concurrent nature of these processes significantly increases productivity and product quality, aspects that are obviously important in today’s fast-paced market.^[3] This philosophy is key to the success of concurrent engineering because it allows for errors and redesigns to be discovered early in the design process when the project is still in a more abstract and possibly digital realm. By locating and fixing these issues early, the design team can avoid what often become costly errors as the project moves to more complicated computational models and eventually into the physical realm.^[4]

As mentioned above, part of the design process is to ensure that the entire product’s life cycle is taken into consideration. This includes establishing user requirements, propagating early conceptual designs, running computational models, creating physical prototypes and eventually manufacturing the product. Included in the process is taking into full account funding, work force capability and time, subject areas that are extremely important factors in the success of a concurrent engineering system. As before, the extensive use of forward planning allows for unforeseen design problems to be caught early so that the basic conceptual design can be altered before actual physical production commences. The amount of money that can be saved by doing this correctly has proven to be significant and is generally the deciding factor for companies moving to a concurrent design framework.^[3]

One of the most important reasons for the huge success of concurrent engineering is that by definition it redefines the basic design process structure that was common place for decades. This was a structure based on a sequential design flow, sometimes called the ‘Waterfall Model’.^[5]^[6] Concurrent engineering significantly modifies this outdated method and instead opts to use what has been termed an iterative or integrated development method.^[7] The difference between these two methods is that the ‘Waterfall’ method moves in a completely linear fashion by starting with user requirements and sequentially moving forward to design, implementation and additional steps until you have a finished product. The problem here is that the design system does not look backwards or forwards from the step it is on to fix possible problems. In the case that something does go wrong, the design usually must be scrapped or heavily altered. On the other hand, the iterative design process is more cyclic in that, as mentioned before, all aspects of the life cycle of the product are taken into account, allowing for a more evolutionary approach to design.^[8] The difference between the two design processes can be seen graphically in Figure 1.

Fig. 1 – “Waterfall” or Sequential Development Method vs. Iterative Development Method

A significant part of this new method is that the individual engineer is given much more say in the overall design process due to the collaborative nature of concurrent engineering. Giving the designer ownership plays a large role in the productivity of the employee and quality of the product that is being produced. This stems from the fact that people given a sense of gratification and ownership over their work tend to work harder and design a more robust product, as opposed to an employee that is assigned a task with little say in the general process.^[4]

By making this sweeping change, many organizational and managerial challenges arise that must be taken into special consideration when companies and organizations move towards such a system. From this standpoint, issues such as the implementation of early design reviews, enabling communication between engineers, software compatibility and opening the design process up to allow for concurrency creates problems of its own .^[9] Similarly, there must be a strong basis for teamwork since the overall success of the method relies on the ability of engineers to effectively work together. Often this can be a difficult obstacle, but is something that must be tackled early to avoid later problems .^[10]

Similarly, now more than ever, software is playing a huge role in the engineering design process. Be it from CAD packages to finite element analysis tools, the ability to quickly and easily modify digital models to predict future design problems is hugely important no matter what design process you are using. However, in concurrent engineering software’s role becomes much more significant as the collaborative nature must take into the account that each engineer’s design models must be able to ‘talk’ to each other in order to successfully utilize the concepts of concurrent engineering.

Concurrent engineering elements

Cross-functional teams

Include members from various disciplines involved in the process, including manufacturing, hardware and software design, marketing, and so forth

Concurrent product realization

A process activities are at the heart of concurrent engineering. Doing several things at once, such as designing various subsystems simultaneously, is critical to reducing design time.

Incremental information sharing

It helps minimize the chance that concurrent product realization will lead to surprises. As soon as new information becomes available, it is shared and integrated into the design. Cross functional teams are important to the effective sharing of information in a timely fashion.===

Integrated project management

It ensures that someone is responsible for the entire project, and that responsibility is not abdicated once one aspect of the work is done.

Definition

Several definitions of concurrent engineering are in use.

The first one is used by the Concurrent Design Facility (ESA):

“

Concurrent Engineering (CE) is a systematic approach to integrated product development that emphasizes the response to customer expectations. It embodies team values of co-operation, trust and sharing in such a manner that decision making is by consensus, involving all perspectives in parallel, from the beginning of the product life cycle.

”

The second one is by Pennell and Winner, 1989:

“

Concurrent Engineering is a systematic approach to the integrated, concurrent design of products and their related processes, including, manufacturing and support. This approach is intended to cause the developers from the very outset to consider all elements of the product life cycle, from conception to disposal, including cost, schedule, quality and user requirements.

”

Using C.E.

Currently, several companies, agencies and universities use CE. Among them can be mentioned:

• European Space Agency Concurrent Design Facility

• NASA Team X – Jet Propulsion Laboratory

• NASA Integrated Design Center (IDC), Mission Design Lab (MDL), and Instrument Design Lab (IDL) – Goddard Space Flight Center

• CNES – French Space Agency

• ASI – Italian Space Agency

• Boeing

• EADS Astrium – Satellite Design Office

• Thales Alenia Space

• The Aerospace Corporation Concept Design Center

• STV Incorporated – [1]

• German Aerospace Center Deutsches Zentrum fur Luft – Und Raumfahrt Deutsches Zentrum fur Luft Und Raumfahrt

• JAQAR Concurrent Design Services

• EPFL Space Center

References

^ Ma, Y., Chen, G. & Thimm, G.; “Paradigm Shift: Unified and Associative Feature-based Concurrent Engineering and Collaborative Engineering”, Journal of Intelligent Manufacturing, DOI 10.1007/s10845-008-0128-y
^ Kusiak, Andrew; Concurrent Engineering: Automation, Tools and Techniques
^ ^a ^b Quan, W. & Jianmin, H., A Study on Collaborative Mechanism for Product Design in Distributed Concurrent Engineering IEEE
^ ^a ^b Kusiak, Andrew, Concurrent Engineering: Automation, Tools and Techniques
^ “The standard waterfall model for systems development”, NASA Webpage, November 14, 2008
^ Kock, N. and Nosek, J., “Expanding the Boundaries of E-Collaboration”, IEEE Transactions on Professional Communication, Vol 48 No 1, March 2005.
^ Ma, Y., Chen, G., Thimm, G., “Paradigm Shift: Unified and Associative Feature-based Concurrent Engineering and Collaborative Engineering”, Journal of Intelligent Manufacturing, DOI 10.1007/s10845-008-0128-y
^ Royce, Winston, “Managing the Development of Large Software Systems”, Proceedings of IEEE WESCON 26 (August 1970): 1-9.
^ Kusiak, Andrew, “Concurrent Engineering: Automation, Tools and Techniques”
^ Rosenblatt, A. and Watson, G. (1991). “Concurrent Engineering”, IEEE Spectrum, July, pp 22-37.

This information originally retrieved from http://en.wikipedia.org/wiki/Concurrent_engineering
on Thursday 11th August 2011 2:52 pm EDT
Now edited and maintained by ManufacturingET.org

Product Lifecycle Management (PLM)

3:38 pm |

Author: ManufacturingET.org | Category: Engineering Design | Tags: CAx, PLM | Comments: None

ManufacturingET.org > 2011 > August

In industry, product lifecycle management (PLM) is the process of managing the entire lifecycle of a product from its conception, through design and manufacture, to service and disposal.^[1] PLM integrates people, data, processes and business systems and provides a product information backbone for companies and their extended enterprise.^[2]

‘Product lifecycle management’ (PLM) should be distinguished from ‘Product life cycle management (marketing)‘ (PLCM). PLM describes the engineering aspect of a product, from managing descriptions and properties of a product through its development and useful life; whereas, PLCM refers to the commercial management of life of a product in the business market with respect to costs and sales measures.

Product lifecycle management is one of the four cornerstones of a corporation’s information technology structure.^[3] All companies need to manage communications and information with their customers (CRM-Customer Relationship Management), their suppliers (SCM-Supply Chain Management), their resources within the enterprise (ERP-Enterprise Resource Planning) and their planning (SDLC-Systems Development Life Cycle). In addition, manufacturing engineering companies must also develop, describe, manage and communicate information about their products.

One form of PLM is called people-centric PLM. While traditional PLM tools have been deployed only on release or during the release phase, people-centric PLM targets the design phase.

Recent (as of 2009) ICT development (EU funded PROMISE project 2004-2008) has allowed PLM to extend beyond traditional PLM and integrate sensor data and real time ‘lifecycle event data’ into PLM, as well as allowing this information to be made available to different players in the total lifecycle of an individual product (closing the information loop). This has resulted in the extension of PLM into Closed Loop Lifecycle Management (CL₂M).

Benefits

Documented benefits of product lifecycle management include:^[4]^[5]

Reduced time to market
Improved product quality
Reduced prototyping costs
More accurate and timely Request For Quote generation
Ability to quickly identify potential sales opportunities and revenue contributions
Savings through the re-use of original data
A framework for product optimization
Reduced waste
Savings through the complete integration of engineering workflows
Documentation that can assist in proving Compliance for RoHS or Title 21 CFR Part 11
Ability to provide Contract Manufacturers with access to a centralized product record

Areas of PLM

Within PLM there are five primary areas;

Note: While application software is not required for PLM processes, the business complexity and rate of change requires organizations execute as rapidly as possible.

Systems Engineering is focused on meeting all requirements, primary meeting customer needs, and coordinating the Systems Design process by involving all relevant disciplines. Product and Portfolio Management is focused on managing resource allocation, tracking progress vs. plan for projects in the new product development projects that are in process (or in a holding status). Portfolio management is a tool that assists management in tracking progress on new products and making trade-off decisions when allocating scarce resources. Product Data Management is focused on capturing and maintaining information on products and/or services through their development and useful life.

Introduction to development process

The core of PLM (product lifecycle management) is in the creations and central management of all product data and the technology used to access this information and knowledge. PLM as a discipline emerged from tools such as CAD, CAM and PDM, but can be viewed as the integration of these tools with methods, people and the processes through all stages of a product’s life.^[6] It is not just about software technology but is also a business strategy.^[7]

For simplicity the stages described are shown in a traditional sequential engineering workflow. The exact order of event and tasks will vary according to the product and industry in question but the main processes are:^[8]

Conceive
- Specification
- Concept design
Design
- Detailed design
- Validation and analysis (simulation)
- Tool design
Realize
- Plan manufacturing
- Manufacture
- Build/Assemble
- Test (quality check)
Service
- Sell and Deliver
- Use
- Maintain and Support
- Dispose

The major key point events are:

Order
Idea
Kick-off
Design freeze
Launch

The reality is however more complex, people and departments cannot perform their tasks in isolation and one activity cannot simply finish and the next activity start. Design is an iterative process, often designs need to be modified due to manufacturing constraints or conflicting requirements. Where exactly a customer order fits into the time line depends on the industry type, whether the products are for example Build to Order, Engineer to Order, or Assemble to Order.

History

Inspiration for the burgeoning business process now known as PLM came when American Motors Corporation (AMC) was looking for a way to speed up its product development process to compete better against its larger competitors in 1985, according to François Castaing, Vice President for Product Engineering and Development.^[9] After introducing its compact Jeep Cherokee (XJ), the vehicle that launched the modern sport utility vehicle (SUV) market, AMC began development of a new model, that later came out as the Jeep Grand Cherokee. The first part in its quest for faster product development was computer-aided design (CAD) software system that make engineers more productive. The second part in this effort was the new communication system that allowed conflicts to be resolved faster, as well as reducing costly engineering changes because all drawings and documents were in a central database. The product data management was so effective, that after AMC was purchased by Chrysler, the system was expanded throughout the enterprise connecting everyone involved in designing and building products. While an early adopter of PLM technology, Chrysler was able to become the auto industry’s lowest-cost producer, recording development costs that were half of the industry average by the mid-1990s.^[9]

Phases of product lifecycle and corresponding technologies

Many software solutions have developed to organize and integrate the different phases of a product’s lifecycle. PLM should not be seen as a single software product but a collection of software tools and working methods integrated together to address either single stages of the lifecycle or connect different tasks or manage the whole process. Some software providers cover the whole PLM range while others a single niche application. Some applications can span many fields of PLM with different modules within the same data model. An overview of the fields within PLM is covered here. It should be noted however that the simple classifications do not always fit exactly, many areas overlap and many software products cover more than one area or do not fit easily into one category. It should also not be forgotten that one of the main goals of PLM is to collect knowledge that can be reused for other projects and to coordinate simultaneous concurrent development of many products. It is about business processes, people and methods as much as software application solutions. Although PLM is mainly associated with engineering tasks it also involves marketing activities such as Product Portfolio Management (PPM), particularly with regards to new product development (NPD). There are several life-cycle models in industry to consider, but most are rather similar. What follows below is one possible life-cycle model; while it emphasizes hardware-oriented products, similar phases would describe any form of product or service, including non-technical or software-based products:

Phase 1: Conceive

Imagine, specify, plan, innovate

The first stage in idea is the definition of its requirements based on customer, company, market and regulatory bodies’ viewpoints. From this specification of the products major technical parameters can be defined. Parallel to the requirements specification the initial concept design work is carried out defining the aesthetics of the product together with its main functional aspects. For the Industrial Design, Styling, work many different media are used from pencil and paper, clay models to 3D CAID Computer-aided industrial design software.

In some concepts, the investment of resources into research or analysis-of-options may be included in the conception phase – e.g. bringing the technology to a level of maturity sufficent to move to the next phase. However, life-cycle engineering is iterative. It is always possible that something doesn’t work well in any phase enough to back up into a prior phase – perhaps all the way back to conception or research. There are many examples to draw from.

Phase 2: Design

Describe, define, develop, test, analyze and validate

This is where the detailed design and development of the product’s form starts, progressing to prototype testing, through pilot release to full product launch. It can also involve redesign and ramp for improvement to existing products as well as planned obsolescence. The main tool used for design and development is CAD Computer-aided design. This can be simple 2D Drawing / Drafting or 3D Parametric Feature Based Solid/Surface Modeling. Such software includes technology such as Hybrid Modeling, Reverse Engineering, KBE (Knowledge-Based Engineering), NDT (Nondestructive testing), Assembly construction.

This step covers many engineering disciplines including: Mechanical, Electrical, Electronic, Software (embedded), and domain-specific, such as Architectural, Aerospace, Automotive, … Along with the actual creation of geometry there is the analysis of the components and product assemblies. Simulation, validation and optimization tasks are carried out using CAE (Computer-aided engineering) software either integrated in the CAD package or stand-alone. These are used to perform tasks such as:- Stress analysis, FEA (Finite Element Analysis); Kinematics; Computational fluid dynamics (CFD); and mechanical event simulation (MES). CAQ (Computer-aided quality) is used for tasks such as Dimensional Tolerance (engineering) Analysis. Another task performed at this stage is the sourcing of bought out components, possibly with the aid of Procurement systems.

Phase 3: Realize

Manufacture, make, build, procure, produce, sell and deliver

Once the design of the product’s components is complete the method of manufacturing is defined. This includes CAD tasks such as tool design; creation of CNC Machining instructions for the product’s parts as well as tools to manufacture those parts, using integrated or separate CAM Computer-aided manufacturing software. This will also involve analysis tools for process simulation for operations such as casting, molding, and die press forming. Once the manufacturing method has been identified CPM comes into play. This involves CAPE (Computer-aided Production Engineering) or CAP/CAPP – (Production Planning) tools for carrying out Factory, Plant and Facility Layout and Production Simulation. For example: Press-Line Simulation; and Industrial Ergonomics; as well as tool selection management. Once components are manufactured their geometrical form and size can be checked against the original CAD data with the use of Computer Aided Inspection equipment and software. Parallel to the engineering tasks, sales product configuration and marketing documentation work will be taking place. This could include transferring engineering data (geometry and part list data) to a web based sales configurator and other Desktop Publishing systems.

Phase 4: Service

Use, operate, maintain, support, sustain, phase-out, retire, recycle and disposal

The final phase of the lifecycle involves managing of in service information. Providing customers and service engineers with support information for repair and maintenance, as well as waste management/recycling information. This involves using such tools as Maintenance, Repair and Operations Management (MRO) software.

It is easy to forget that there is an end-of-life to every product. Whether it be disposal or destruction of material objects or information, this needs to be considered since it may not be free from ramifications.

All phases: product lifecycle

Communicate, manage and collaborate

None of the above phases can be seen in isolation. In reality a project does not run sequentially or in isolation of other product development projects. Information is flowing between different people and systems. A major part of PLM is the co-ordination of and management of product definition data. This includes managing engineering changes and release status of components; configuration product variations; document management; planning project resources and timescale and risk assessment.

For these tasks graphical, text and metadata such as product bills of materials (BOMs) needs to be managed. At the engineering departments level this is the domain of PDM – (Product Data Management) software, at the corporate level EDM (Enterprise Data Management) software, these two definitions tend to blur however but it is typical to see two or more data management systems within an organization. These systems are also linked to other corporate systems such as SCM, CRM, and ERP. Associated with these system are Project Management Systems for Project/Program Planning.

This central role is covered by numerous Collaborative Product Development tools which run throughout the whole lifecycle and across organizations. This requires many technology tools in the areas of Conferencing, Data Sharing and Data Translation. The field being Product visualization which includes technologies such as DMU (Digital Mock-Up), Immersive Virtual Digital Prototyping (virtual reality) and Photo realistic Imaging.

User skills

The broad array of solutions that make up the tools used within a PLM solution-set (e.g., CAD, CAM, CAx…) were initially used by dedicated practitioners who invested time and effort to gain the required skills. Designers and engineers worked wonders with CAD systems, manufacturing engineers became highly skilled CAM users while analysts, administrators and managers fully mastered their support technologies. However, achieving the full advantages of PLM requires the participation of many people of various skills from throughout an extended enterprise, each requiring the ability to access and operate on the inputs and output of other participants.

Despite the increased ease of use of PLM tools, cross-training all personnel on the entire PLM tool-set has not proven to be practical. Now, however, advances are being made to address ease of use for all participants within the PLM arena. One such advance is the availability of “role” specific user interfaces. Through Tailorable UIs, the commands that are presented to users are appropriate to their function and expertise.

Product development processes and methodologies

A number of established methodologies have been adopted by PLM and been further advanced. Together with PLM digital engineering techniques, they have been advanced to meet company goals such as reduced time to market and lower production costs. Reducing lead times is a major factor as getting a product to market quicker than the competition will help with higher revenue and profit margins and increase market share.

These techniques include:-

Concurrent engineering workflow
Industrial Design
Bottom-up design
Top-down design
Front loading design workflow
Design in context
Modular design
NPD New product development
DFSS Design for Six Sigma
DFMA Design for manufacture / assembly
Digital simulation engineering
Requirement driven design
Specification managed validation
Configuration Management

Concurrent engineering workflow

Concurrent engineering (British English: simultaneous engineering) is a workflow that, instead of working sequentially through stages, carries out a number of tasks in parallel. For example: starting tool design before the detailed designs of the product are finished, or starting on detail design solid models before the concept design surfaces models are complete. Although this does not necessarily reduce the amount of manpower required for a project, it does drastically reduce lead times and thus time to market. Feature-based CAD systems have for many years allowed the simultaneous work on 3D solid model and the 2D drawing by means of two separate files, with the drawing looking at the data in the model; when the model changes the drawing will associatively update. Some CAD packages also allow associative copying of geometry between files. This allows, for example, the copying of a part design into the files used by the tooling designer. The manufacturing engineer can then start work on tools before the final design freeze; when a design changes size or shape the tool geometry will then update. Concurrent engineering also has the added benefit of providing better and more immediate communication between departments, reducing the chance of costly, late design changes. It adopts a problem prevention method as compared to the problem solving and re-designing method of traditional sequential engineering.

Bottom-up design

Bottom-up design (CAD Centric) occurs where the definition of 3D models of a product starts with the construction of individual components. These are then virtually brought together in sub-assemblies of more than one level until the full product is digitally defined. This is sometimes known as the review structure showing what the product will look like. The BOM contains all of the physical (solid) components; it may (but not also) contain other items required for the final product BOM such as paint, glue, oil and other materials commonly described as ‘bulk items’. Bulk items typically have mass and quantities but are not usually modelled with geometry.

Bottom-up design tends to focus on the capabilities of available real-world physical technology, implementing those solutions which this technology is most suited to. When these bottom-up solutions have real-world value, bottom-up design can be much more efficient than top-down design. The risk of bottom-up design is that it very efficiently provides solutions to low-value problems. The focus of Bottom-Up design is “what can we most efficiently do with this technology?” rather than the focus of Top-Down which is “What is the most valuable thing to do?”

Top-down design

Top-Down design is focused on high-level functional requirements, with relatively less focus on existing implementation technology. A top level spec is decomposed into lower and lower level structures and specifications, until the physical implementation layer is reached. The risk of a top-down design is that it will not take advantage of the most efficient applications of current physical technology, especially with respect to hardware implementation. Top-Down design sometimes results in excessive layers of lower-level abstraction and inefficient performance when the Top-Down model has followed an abstraction path which does not efficiently fit available physical-level technology. The positive value of Top-Down design is that it preserves a focus on the optimum solution requirements.

A Part-Centric Top-down design may eliminate some of the risks of Top-Down design. This starts with a layout model, often a simple 2D sketch defining basic sizes and some major defining parameters. Industrial Design, brings creative ideas to product development. Geometry from this is associatively copied down to the next level, which represents different sub-systems of the product. The geometry in the sub-systems is then used to define more detail in levels below. Depending on the complexity of the product, a number of levels of this assembly are created until the basic definition of components can be identified, such as position and principal dimensions. This information is then associatively copied to component files. In these files the components are detailed; this is where the classic bottom-up assembly starts.

The top down assembly is sometime known as a control structure. If a single file is used to define the layout and parameters for the review structure it is often known as a skeleton file.

Defense engineering traditionally develops the product structure from the top down. The system engineering process^[10] prescribes a functional decomposition of requirements and then physical allocation of product structure to the functions. This top down approach would normally have lower levels of the product structure developed from CAD data as a bottom up structure or design.

Both-Ends-Against-The-Middle design

Both-Ends-Against-The-Middle (BEATM) design is a design process that endeavors to combine the best features of Top-Down design, and Bottom-Up design into one process. A BEATM design process flow may begin with an emergent technology which suggests solutions which may have value, or it may begin with a top-down view of an important problem which needs a solution. In either case the key attribute of BEATM design methodology is to immediately focus at both ends of the design process flow: a top-down view of the solution requirements, and a bottom-up view of the available technology which may offer promise of an efficient solution. The BEATM design process proceeds from both ends in search of an optimum merging somewhere between the top-down requirements, and bottom-up efficient implementation. In this fashion, BEATM has been shown to genuinely offer the best of both methodologies. Indeed some of the best success stories from either top-down or bottom-up have been successful because of an intuitive, yet unconscious use of the BEATM methodology. When employed consciously, BEATM offers even more powerful advantages.

Front loading design and workflow

Front loading is taking top-down design to the next stage. The complete control structure and review structure, as well as downstream data such as drawings, tooling development and CAM models, are constructed before the product has been defined or a project kick-off has been authorized. These assemblies of files constitute a template from which a family of products can be constructed. When the decision has been made to go with a new product, the parameters of the product are entered into the template model and all the associated data is updated. Obviously predefined associative models will not be able to predict all possibilities and will require additional work. The main principle is that a lot of the experimental/investigative work has already been completed. A lot of knowledge is built into these templates to be reused on new products. This does require additional resources “up front” but can drastically reduce the time between project kick-off and launch. Such methods do however require organizational changes, as considerable engineering efforts are moved into “offline” development departments. It can be seen as an analogy to creating a concept car to test new technology for future products, but in this case the work is directly used for the next product generation.

Design in context

Individual components cannot be constructed in isolation. CAD; CAiD models of components are designed within the context of part or all of the product being developed. This is achieved using assembly modelling techniques. Other components’ geometry can be seen and referenced within the CAD tool being used. The other components within the sub-assembly, may or may not have been constructed in the same system, their geometry being translated from other CPD formats. Some assembly checking such as DMU is also carried out using Product visualization software.

Product and process lifecycle management (PPLM)

Product and process lifecycle management (PPLM) is an alternate genre of PLM in which the process by which the product is made is just as important as the product itself. Typically, this is the life sciences and advanced specialty chemicals markets. The process behind the manufacture of a given compound is a key element of the regulatory filing for a new drug application. As such, PPLM seeks to manage information around the development of the process in a similar fashion that baseline PLM talks about managing information around development of the product.

Market size

Total spending on PLM software and services was estimated in 2006 to be above $15 billion a year, but it is difficult to find any two market analysis reports that agree on figures.^[11]^[12] Market growth estimates are in the 10% area.

References

^ “About PLM”. CIMdata. http://www.cimdata.com/plm.html.
^ “What is PLM?”. PLM Technology Guide. http://plmtechnologyguide.com/site/?page_id=435.
^ Evans, Mike. “The PLM Debate”. Cambashi. http://www.cambashi.com/the-plm-debate—outsourcing-upsets-the-it-integration-pillars.
^ Day, Martyn (2002.04.15). “What is PLM”. Cad Digest. http://www.caddigest.com/subjects/PLM/select/day_plm.htm.
^ Hill, Sidney (2006.12.01). “A winning strategy”. Manufacturing Business Technology. http://www.mbtmag.com/current_issues/2006/sept/coverstory1.asp?CategoryID=66.
^ Teresko, John (2004.01.02). “The PLM Revolution”. IndustryWeek. http://www.industryweek.com/CurrentArticles/Asp/articles.asp?ArticleId=1558.
^ Stackpole, Beth (2003.05.15). “There’s a New App in Town”. CIO Magazine. http://www.cio.com/archive/051503/app.html.
^ Goul, Lawrence (2002.06.05). “Additional ABCs About PLM”. Automotive Design and Production. http://www.autofieldguide.com/articles/120506.html.
^ ^a ^b Sidney Hill, Jr., “How To Be A Trendsetter: Dassault And IBM PLM Customers Swap Tales From The PLM Front”, retrieved on March 28, 2008.
^ Incose SYSTEMS ENGINEERING HANDBOOK, A “HOW TO” GUIDE For All Engineers, Version 2.0, July 2000. pg 358
^ CIMdata… (2006-10-11). “Comprehensive Information and Analysis of the PLM Market”. Press release. http://www.cimdata.com/news_events/press_release.html?press_release_ID=30.
^ Daratech (2006-03-13). “PLM Market Projected to Reach $12 Billion in 2006, Up 14%”. Press release. http://www.daratech.com/press/releases/2006/060313a.html.

Characteristics

Etched surface from a high purity (99.9998%) aluminium bar, size 55×37 mm

Physical

Aluminium is a soft, durable, lightweight, ductile and malleable metal with appearance ranging from silvery to dull gray, depending on the surface roughness. Aluminium is nonmagnetic and nonsparking.^{[clarification needed]} It is also insoluble in alcohol, though it can be soluble in water in certain forms. The yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa.^[7] Aluminium has about one-third the density and stiffness of steel. It is easily machined, cast, drawn and extruded.

Corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper.^[7] This corrosion resistance is also often greatly reduced when many aqueous salts are present, particularly in the presence of dissimilar metals.

Aluminium atoms are arranged in a face-centered cubic (fcc) structure. Aluminium has a stacking-fault energy of approximately 200 mJ/m².^[8]

Aluminium is one of the few metals that retain full silvery reflectance in finely powdered form, making it an important component of silver-colored paints. Aluminium mirror finish has the highest reflectance of any metal in the 200–400 nm (UV) and the 3,000–10,000 nm (far IR) regions; in the 400–700 nm visible range it is slightly outperformed by tin and silver and in the 700–3000 (near IR) by silver, gold, and copper.^[9]

Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical. Aluminium is capable of being a superconductor, with a superconducting critical temperature of 1.2 Kelvin and a critical magnetic field of about 100 gauss (10 milliteslas).^[10]

Creation

Stable aluminium is created when hydrogen fuses with magnesium either in large stars or in supernovae.^[11]

Isotopes

Main article: Isotopes of aluminium

Aluminium has many known isotopes, whose mass numbers range from 21 to 42; however, only ²⁷Al (stable isotope) and ²⁶Al (radioactive isotope, t_1/2 = 7.2×10⁵ y) occur naturally. ²⁷Al has a natural abundance above 99.9%. ²⁶Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of ²⁶Al to ¹⁰Be has been used to study the role of transport, deposition, sediment storage, burial times, and erosion on 10⁵ to 10⁶ year time scales.^[12] Cosmogenic ²⁶Al was first applied in studies of the Moon and meteorites. Meteoroid fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial ²⁶Al production. After falling to Earth, atmospheric shielding drastically reduces ²⁶Al production, and its decay can then be used to determine the meteorite’s terrestrial age. Meteorite research has also shown that ²⁶Al was relatively abundant at the time of formation of our planetary system. Most meteorite scientists believe that the energy released by the decay of ²⁶Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.^[13]

Natural occurrence

In the Earth’s crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon).^[14] Because of its strong affinity to oxygen, it is almost never found in the elemental state; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth’s crust, are aluminosilicates. Native aluminium metal can be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes.^[15] Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea and Chen et al. (2011)^[16] have proposed a theory of its origin as resulting by reduction from tetrahydroxoaluminate Al(OH)₄^- to metallic aluminium by bacteria.^[16]

It also occurs in the minerals beryl, cryolite, garnet, spinel and turquoise. Impurities in Al₂O₃, such as chromium or iron yield the gemstones ruby and sapphire, respectively.

Although aluminium is an extremely common and widespread element, the common aluminium minerals are not economic sources of the metal. Almost all metallic aluminium is produced from the ore bauxite (AlO_x(OH)_3-2x). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions.^[17] Large deposits of bauxite occur in Australia, Brazil, Guinea and Jamaica and the primary mining areas for the ore are in Australia, Brazil, China, India, Guinea, Indonesia, Jamaica, Russia and Surinam.

Production and refinement

Although aluminium is the most abundant metallic element in the Earth’s crust, it is never found in free, metallic form.

Bauxite

Aluminium forms strong chemical bonds with oxygen. Compared to most other metals, it is difficult to extract from ore, such as bauxite, due to the energy required to reduce aluminium oxide (Al₂O₃). For example, direct reduction with carbon, as is used to produce iron, is not chemically possible, since aluminium is a stronger reducing agent than carbon. There is an indirect carbothermic reduction possible by using carbon and Al₂O₃, which forms an intermediate Al₄C₃ and this can further yield aluminium metal at a temperature of 1900–2000°C. This process is still under development. This process costs less energy and yields less CO₂ than the Hall-Héroult process, the major industrial process for aluminium extraction.^[18] Aluminium oxide has a melting point of about 2,000 °C (3,600 °F). Therefore, it must be extracted by electrolysis. In this process, the aluminium oxide is dissolved in molten cryolite with calcium fluoride and then reduced to the pure metal. The operational temperature of the reduction cells is around 950 to 980 °C (1,740 to 1,800 °F). Cryolite is found as a mineral in Greenland, but in industrial use it has been replaced by a synthetic substance. Cryolite is a chemical compound of aluminium and sodium fluorides: (Na₃AlF₆). The aluminium oxide (a white powder) is obtained by refining bauxite in the Bayer process of Karl Bayer. (Previously, the Deville process was the predominant refining technology.)

The electrolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminium chloride with potassium. Both of the electrodes used in the electrolysis of aluminium oxide are carbon. Once the refined alumina is dissolved in the electrolyte, its ions are free to move around. The reaction at the cathode is:

Al³⁺ + 3 e⁻ → Al

Here the aluminium ion is being reduced. The aluminium metal then sinks to the bottom and is tapped off, usually cast into large blocks called aluminium billets for further processing.

At the anode, oxygen is formed:

2 O²⁻ → O₂ + 4 e⁻

To some extent, the carbon anode is degraded by the oxygen. The anodes in a reduction cell must therefore be replaced regularly, since they are consumed in the process. The cathodes do erode, mainly due to electrochemical processes and metal movement. After five to ten years, depending on the current used in the electrolysis, a cell has to be rebuilt because of cathode wear.

World production trend of aluminium

Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologically. The worldwide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters achieve approximately 12.8 kW·h/kg (46.1 MJ/kg). (Compare this to the heat of reaction, 31 MJ/kg, and the Gibbs free energy of reaction, 29 MJ/kg.) Reduction line currents for older technologies are typically 100 to 200 kiloamperes; state-of-the-art smelters operate at about 350 kA. Trials have been reported with 500 kA cells.

The Hall-Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoope process. The process involves the electrolysis of molten aluminium with a sodium, barium and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%.^[19]^[20]

Electric power represents about 20% to 40% of the cost of producing aluminium, depending on the location of the smelter. Aluminum production consumes roughly 5% of electricity generated in the U.S.^[21] Smelters tend to be situated where electric power is both plentiful and inexpensive, such as the United Arab Emirates with excess natural gas supplies and Iceland and Norway with energy generated from renewable sources. The world’s largest smelters of alumina are People’s Republic of China, Russia, and Quebec and British Columbia in Canada.^[22]^[23]^[21]

Aluminium output in 2005

In 2005, the People’s Republic of China was the top producer of aluminium with almost a one-fifth world share, followed by Russia, Canada, and the USA, reports the British Geological Survey.

Over the last 50 years, Australia has become a major producer of bauxite ore and a major producer and exporter of alumina (before being overtaken by China in 2007).^[22]^[24] Australia produced 62 million tonnes of bauxite in 2005. The Australian deposits have some refining problems, some being high in silica, but have the advantage of being shallow and relatively easy to mine.^[25]

Recycling

Aluminium recycling code

Main article: Aluminium recycling

Aluminium is 100% recyclable without any loss of its natural qualities. Recovery of the metal via recycling has become an important facet of the aluminium industry. Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to the public awareness.

Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as dross (ash-like oxide).^[26] The dross can undergo a further process to extract aluminium.

In Europe aluminium experiences high rates of recycling, ranging from 42% of beverage cans, 85% of construction materials and 95% of transport vehicles.^[27]

Recycled aluminium is known as secondary aluminium, but maintains the same physical properties as primary aluminium. Secondary aluminium is produced in a wide range of formats and is employed in 80% of the alloy injections. Another important use is for extrusion.

White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be extracted industrially.^[28] The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manage. It reacts with water, releasing a mixture of gases (including, among others, hydrogen, acetylene, and ammonia), which spontaneously ignites on contact with air;^[29] contact with damp air results in the release of copious quantities of ammonia gas. Despite these difficulties, the waste has found use as a filler in asphalt and concrete.^[30]

Compounds

Oxidation state +3

The vast majority of compounds, including all Al-containing minerals and all commercially significant aluminium compounds, feature aluminium in the oxidation state 3+. The coordination number of such compounds varies, but generally Al³⁺ is six-coordinate or tetracoordinate. Almost all compounds of aluminium(III) are colorless.^[14]

Halides

All four trihalides are well known. Unlike the structures of the three heavier trihalides, aluminium fluoride (AlF₃) features six-coordinate Al. The octahedral coordination environment for AlF₃ is related to the compactness of fluoride ion, six of which can fit around the small Al³⁺ centre. AlF₃ sublimes (with cracking) at 1,291 °C (2,356 °F). With heavier halides, the coordination numbers are lower. The other trihalides are dimeric or polymeric with tetrahedral Al centers. These materials are prepared by treating aluminium metal with the halogen, although other methods exist. Acidification of the oxides or hydroxides affords hydrates. In aqueous solution, the halides often form mixtures, generally containing six-coordinate Al centres, which are feature both halide and aquo ligands. When aluminium and fluoride are together in aqueous solution, they readily form complex ions such as [AlF(H₂O)₅]²⁺, AlF₃(H₂O)₃, and [AlF₆]³⁻. In the case of chloride, polyaluminium clusters are formed such as [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺.

Oxide and hydroxides

Aluminium forms one stable oxide, known by its mineral name corundum. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. The two oxide-hydroxides (AlO(OH) are boehmite and diaspore. There are three trihydroxides: bayerite, gibbsite, and nordstrandite, which differ in their crystalline structure (polymorphs). Most are produced from ores by a variety of wet processes using acid and base. Heating the hydroxides leads to formation of corundrum. These materials are of central importance to the production of aluminium and are themselves extremely useful.

Carbide, nitride, and related materials

Aluminium carbide (Al₄C₃) is made by heating a mixture of the elements above 1,000 °C (1,832 °F). The pale yellow crystals consist of tetrahedral aluminium centres. It reacts with water or dilute acids to give methane. The acetylide, Al₂(C₂)₃, is made by passing acetylene over heated aluminium.

Aluminium nitride (AlN) is the only nitride known for aluminium. Unlike the oxides it features tetrahedral Al centres. It can be made from the elements at 800 °C (1,472 °F). It is air-stable material with a usefully high thermal conductivity. Aluminium phosphide (AlP) is made similarly, and hydrolyses to give phosphine:

AlP + 3 H₂O → Al(OH)₃ + PH₃

Organoaluminium compounds and related hydrides

Main article: Organoaluminium compound

Structure of trimethylaluminium, a compound that features five-coordinate carbon.

A variety of compounds of empirical formula AlR₃ and AlR_1.5Cl_1.5 exist.^[31] These species usually feature tetrahedral Al centres, e.g. “trimethylaluminium” has the formula Al₂(CH₃)₆ (see figure). With large organic groups, triorganoaluminium exist as three-coordinate monomers, such as triisobutylaluminium. Such compounds are widely used in industrial chemistry, despite the fact that they are often highly pyrophoric. Few analogues exist between organoaluminium and organoboron compounds except for large organic groups.

The important aluminium hydride is lithium aluminium hydride (LiAlH₄), which is used in as a reducing agent in organic chemistry. It can be produced from lithium hydride and aluminium trichloride:

4 LiH + AlCl₃ → LiAlH₄ + 3 LiCl

Several useful derivatives of LiAlH₄ are known, e.g. Sodium bis(2-methoxyethoxy)dihydridoaluminate. The simplest hydride, aluminium hydride or alane, remains a laboratory curiosity. It is a polymer with the formula (AlH₃)_n, in contrast to the corresponding boron hydride with the formula (BH₃)₂.

Oxidation states +1 and 2+

Although the great majority of aluminium compounds feature Al³⁺ centres, compounds with lower oxidation states are known and sometime of significance as precursors to the Al³⁺ species.

Aluminium(I)

AlF, AlCl and AlBr exist in the gaseous phase when the tri-halide is heated with aluminium. The composition AlI is unstable at room temperature with respect to the triiodide:^[32]

3 AlI → AlI₃ + 2 Al

A stable derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al₄I₄(NEt₃)₄. Also of theoretical interest but only of fleeting existence are Al₂O and Al₂S is made by heating the normal oxide, Al₂O₃, with silicon at 1,800 °C (3,272 °F) in a vacuum.^[32] Such materials quickly disproportionates to the starting materials.

Aluminium(II)

Very simple Al(II) compounds are invoked or observed in the reactions of Al metal with oxidants. For example, aluminium monoxide, AlO, has been detected in the gas phase after explosion^[33] and in stellar absorption spectra.^[34] More thoroughly investigated are compounds of the formula R₄Al₂ where R is a large organic ligand.^[35]

Analysis

The presence of aluminium can be detected in qualitative analysis using aluminon.

Applications

General use

Aluminium is the most widely used non-ferrous metal.^[36] Global production of aluminium in 2005 was 31.9 million tonnes. It exceeded that of any other metal except iron (837.5 million tonnes).^[37] Forecast for 2012 is 42–45 million tons, driven by rising Chinese output.^[38] Relatively pure aluminium is encountered only when corrosion resistance and/or workability is more important than strength or hardness. A thin layer of aluminium can be deposited onto a flat surface by physical vapour deposition or (very infrequently) chemical vapour deposition or other chemical means to form optical coatings and mirrors. When so deposited, a fresh, pure aluminium film serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%) of medium and far infrared radiation.

Pure aluminium has a low tensile strength, but when combined with thermo-mechanical processing, aluminium alloys display a marked improvement in mechanical properties, especially when tempered. Aluminium alloys form vital components of aircraft and rockets as a result of their high strength-to-weight ratio. Aluminium readily forms alloys with many elements such as copper, zinc, magnesium, manganese, and silicon (e.g., duralumin). Today, almost all bulk metal materials that are referred to loosely as “aluminium”, are actually alloys. For example, the common aluminium foils and beverage cans are alloys of 92% to 99% aluminium.^[39]

Household aluminium foil

Aluminium-bodied Austin “A40 Sports” (circa 1951)

Aluminium slabs being transported from a smelter

Some of the many uses for aluminium metal are in:

Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, etc.) as sheet, tube, castings, etc.
Packaging (cans, foil, etc.)
Construction (windows, doors, siding, building wire, etc.)
A wide range of household items, from cooking utensils to baseball bats, watches.^[40]
Street lighting poles, sailing ship masts, walking poles, etc.
Outer shells of consumer electronics, also cases for equipment e.g. photographic equipment.
Electrical transmission lines for power distribution
MKM steel and Alnico magnets
Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs.
Heat sinks for electronic appliances such as transistors and CPUs.
Substrate material of metal-core copper clad laminates used in high brightness LED lighting.
Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.
Aluminium can be reacted with hydrochloric acid or with sodium hydroxide to prodce hydrogen gas.
A variety of countries, including France, Italy, Poland, Finland, Romania, Israel, and the former Yugoslavia, have issued coins struck in aluminium or aluminium-copper alloys.^[41]
Some guitar models sports aluminium diamond plates on the surface of the instruments, usually either chrome or black. Kramer Guitars and Travis Bean are both known for having produced guitars with necks made of aluminium, which gives the instrument a very distinct sound.
Sustainability of Aluminium in Buildings

Aluminium compounds

Because aluminium is abundant and most of its compounds exhibit low toxicity, the compounds of aluminium enjoy wide and sometimes large-scale applications.

Alumina

Main article: Aluminium oxide

Aluminium oxide (Al₂O₃) and the associated oxy-hydroxides and trihydroxides are produced or extracted from minerals on a large scale. The great majority of this material is converted to metallic aluminium. About 10% of the production capacity is used for other applications. A major use is as an absorbent, for example alumina will remove water from hydrocarbons, to enable subsequent processes that are poisoned by moisture. Aluminum oxides are common catalysts for industrial processes, e.g. the Claus process for converting hydrogen sulfide to sulfur in refineries and for the alkylation of amines. Many industrial catalysts are “supported”, meaning generally that an expensive catalyst (e.g., platinum) is dispersed over a high surface area material such as alumina. Being a very hard material (Mohs hardness 9), alumina is widely used as an abrasive and the production of applications that exploit its inertness, e.g., in high pressure sodium lamps.

Sulfates

Several sulfates of aluminium find applications. Aluminium sulfate (Al₂(SO₄)₃(H₂O)₁₈) is produced on the annual scale of several billions of kilograms. About half of the production is consumed in water treatment. The next major application is in the manufacture of paper. It is also used as a mordant, in fire extinguisher, as a food additive, in fireproofing, and in leather tanning. Aluminium ammonium sulfate ([Al(NH₄)](SO₄)₂)(H₂O)₁₂, also called ammonium alum, is used as a mordant and in leather tanning.^[6] Aluminium potassium sulfate ([Al(K)](SO₄)₂)(H₂O)₁₂ is used similarly. The consumption of both alums is declining.

Chlorides

Aluminium chloride (AlCl₃) is used in petroleum refining and in the production of synthetic rubber and polymers. Although it has a similar name, aluminium chlorohydrate has fewer and very different applications, e.g. as an hardening agent and an antiperspirant. It is an intermediate in the production of aluminium metal.

Niche compounds

Given the scale of aluminium compounds, a small scale application could still involve thousands of tons. One of the many compounds used at this intermediate level include aluminium acetate, a salt used in solution as an astringent. Aluminium borate (Al₂O₃ B₂O₃) is used in the production of glass and ceramics. Aluminium fluorosilicate (Al₂(SiF₆)₃) is used in the production of synthetic gemstones, glass and ceramic. Aluminium phosphate (AlPO₄) is used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement. Aluminium hydroxide (Al(OH)₃) is used as an antacid, as a mordant, in water purification, in the manufacture of glass and ceramic and in the waterproofing of fabrics. Lithium aluminium hydride is a powerful reducing agent used in organic chemistry

Aluminium alloys in structural applications

Aluminium foam

Main article: Aluminium alloy

Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO).

The strength and durability of aluminium alloys vary widely, not only as a result of the components of the specific alloy, but also as a result of heat treatments and manufacturing processes. A lack of knowledge of these aspects has from time to time led to improperly designed structures and gained aluminium a bad reputation.

One important structural limitation of aluminium alloys is their fatigue strength. Unlike steels, aluminium alloys have no well-defined fatigue limit, meaning that fatigue failure eventually occurs, under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite life.

Another important property of aluminium alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminium, unlike steel, melts without first glowing red. Forming operations where a blow torch is used therefore require some expertise, since no visual signs reveal how close the material is to melting. Aluminium alloys, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminium alloys in this regard is their low melting point, which make them more susceptible to distortions from thermally induced stress relief. Controlled stress relief can be done during manufacturing by heat-treating the parts in an oven, followed by gradual cooling—in effect annealing the stresses.

The low melting point of aluminium alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region.

Another alloy of some value is Aluminium bronze (CuAl₅).

History

The statue of the Anteros (commonly mistaken for either The Angel of Christian Charity or Eros) in Piccadilly Circus, London, was made in 1893 and is one of the first statues to be cast in aluminium.

Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; alum is still used as a styptic. In 1761, Guyton de Morveau suggested calling the base alum alumine. In 1808, Humphry Davy identified the existence of a metal base of alum, which he at first termed alumium and later aluminum (see etymology section, below).

The metal was first produced in 1825 (in an impure form) by Danish physicist and chemist Hans Christian Ørsted. He reacted anhydrous aluminium chloride with potassium amalgam and yielded a lump of metal looking similar to tin.^[42] Friedrich Wöhler was aware of these experiments and cited them, but after redoing the experiments of Ørsted he concluded that this metal was pure potassium. He conducted a similar experiment in 1827 by mixing anhydrous aluminium chloride with potassium and yielded aluminium.^[42] Wöhler is generally credited with isolating aluminium (Latin alumen, alum), but also Ørsted can be listed as its discoverer.^[43] Further, Pierre Berthier discovered aluminium in bauxite ore and successfully extracted it.^[44] Frenchman Henri Etienne Sainte-Claire Deville improved Wöhler’s method in 1846, and described his improvements in a book in 1859, chief among these being the substitution of sodium for the considerably more expensive potassium.^[45] Deville likely also conceived the idea of the electrolysis of aluminium oxide dissolved in cryolite; Charles Martin Hall and Paul Héroult might have developed the more practical process after Deville.

Before the Hall-Héroult process was developed, aluminium was exceedingly difficult to extract from its various ores. This made pure aluminium more valuable than gold.^[46] Bars of aluminium were exhibited at the Exposition Universelle of 1855.^[47] Napoleon III, Emperor of France, is reputed to have given a banquet where the most honoured guests were given aluminium utensils, while the others made do with gold.^[48]^[49] The Washington Monument was completed, with the 100 ounce (2.8 kg) aluminium capstone being put in place on December 6, 1884, in an elaborate dedication ceremony. It was the largest single piece of aluminium cast at the time, when aluminium was as expensive as silver.^[50] Aluminium has been produced in commercial quantities for just over 100 years.

Aluminium was selected as the material to be used for the apex of the Washington Monument in 1884, a time when one ounce (30 grams) cost the daily wage of a common worker on the project;^[51] aluminium was about the same value as silver.

The Cowles companies supplied aluminium alloy in quantity in the United States and England using smelters like the furnace of Carl Wilhelm Siemens by 1886.^[52] Charles Martin Hall of Ohio in the U.S. and Paul Héroult of France independently developed the Hall-Héroult electrolytic process that made extracting aluminium from minerals cheaper and is now the principal method used worldwide. Hall’s process,^[53] in 1888 with the financial backing of Alfred E. Hunt, started the Pittsburgh Reduction Company today known as Alcoa. Héroult’s process was in production by 1889 in Switzerland at Aluminium Industrie, now Alcan, and at British Aluminium, now Luxfer Group and Alcoa, by 1896 in Scotland.^[54]

By 1895, the metal was being used as a building material as far away as Sydney, Australia in the dome of the Chief Secretary’s Building.

Many navies have used an aluminium superstructure for their vessels; the 1975 fire aboard USS Belknap that gutted her aluminium superstructure, as well as observation of battle damage to British ships during the Falklands War, led to many navies switching to all steel superstructures. The Arleigh Burke class was the first such U.S. ship, being constructed entirely of steel.

Aluminium wire was once widely used for domestic electrical wiring. Owing to corrosion-induced failures, a number of fires resulted. This dicontinuation thus illustrates one failed application of the otherwise highly useful metal.

In 2008, the price of aluminium peaked at $1.45/lb in July but dropped to $0.70/lb by December.^[55]

Etymology

Two variants of the metal’s name are in current use, aluminium and aluminum (besides the obsolete alumium). The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990 but, three years later, recognized aluminum as an acceptable variant. Hence their periodic table includes both.^[56] IUPAC prefers the use of aluminium in its internal publications, although nearly as many IUPAC publications use the spelling aluminum.^[57]

Most countries use the spelling aluminium. In the United States, the spelling aluminum predominates.^[14]^[58] The Canadian Oxford Dictionary prefers aluminum, whereas the Australian Macquarie Dictionary prefers aluminium. In 1926, the American Chemical Society officially decided to use aluminum in its publications; American dictionaries typically label the spelling aluminium as a British variant.

The name aluminium derives from its status as a base of alum. It is borrowed from Old French; its ultimate source, alumen, in turn is a Latin word that literally means “bitter salt”.^[59]

The earliest citation given in the Oxford English Dictionary for any word used as a name for this element is alumium, which British chemist and inventor Humphry Davy employed in 1808 for the metal he was trying to isolate electrolytically from the mineral alumina. The citation is from the journal Philosophical Transactions of the Royal Society of London: “Had I been so fortunate as to have obtained more certain evidences on this subject, and to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium, alumium, zirconium, and glucium.”^[60]^[61]

Davy settled on aluminum by the time he published his 1812 book Chemical Philosophy: “This substance appears to contain a peculiar metal, but as yet Aluminum has not been obtained in a perfectly free state, though alloys of it with other metalline substances have been procured sufficiently distinct to indicate the probable nature of alumina.”^[62] But the same year, an anonymous contributor to the Quarterly Review, a British political-literary journal, in a review of Davy’s book, objected to aluminum and proposed the name aluminium, “for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound.”^[63]

The -ium suffix conformed to the precedent set in other newly discovered elements of the time: potassium, sodium, magnesium, calcium, and strontium (all of which Davy isolated himself). Nevertheless, -um spellings for elements were not unknown at the time, as for example platinum, known to Europeans since the 16th century, molybdenum, discovered in 1778, and tantalum, discovered in 1802. The -um suffix is consistent with the universal spelling alumina for the oxide, as lanthana is the oxide of lanthanum, and magnesia, ceria, and thoria are the oxides of magnesium, cerium, and thorium respectively.

The spelling used throughout the 19th century by most U.S. chemists was aluminium, but common usage is less clear.^[64] The aluminum spelling is used in the Webster’s Dictionary of 1828. In his advertising handbill for his new electrolytic method of producing the metal 1892, Charles Martin Hall used the -um spelling, despite his constant use of the -ium spelling in all the patents^[53] he filed between 1886 and 1903.^[65] It has consequently been suggested that the spelling reflects an easier to pronounce word with one fewer syllable, or that the spelling on the flier was a mistake. Hall’s domination of production of the metal ensured that the spelling aluminum became the standard in North America; the Webster Unabridged Dictionary of 1913, though, continued to use the -ium version.

Health concerns

NFPA 704
0 0 0
Fire diamond for aluminium shot

Despite its natural abundance, aluminium has no known function in biology. It is remarkably nontoxic, aluminium sulfate having an LD50 of 6207 mg/kg (oral, mouse), which corresponds to 500 grams for a 80 kg person.^[6] Despite the extremely low acute toxicity, the health effect of Al are of interest in view of the widespread occurrence of the element in the environment and in commerce.

Some toxicity can be traced to deposition in bone and the central nervous system, which is particularly increased in patients with reduced renal function. Because aluminium competes with calcium for absorption, increased amounts of dietary aluminium may contribute to the reduced skeletal mineralization (osteopenia) observed in preterm infants and infants with growth retardation. In very high doses, aluminium can cause neurotoxicity, and is associated with altered function of the blood-brain barrier.^[66] A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminium, such as deodorants or antacids. In those without allergies, aluminium is not as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts.^[67] Although the use of aluminium cookware has not been shown to lead to aluminium toxicity in general, excessive consumption of antacids containing aluminium compounds and excessive use of aluminium-containing antiperspirants provide more significant exposure levels. Studies have shown that consumption of acidic foods or liquids with aluminium significantly increases aluminium absorption,^[68] and maltol has been shown to increase the accumulation of aluminium in nervous and osseus tissue.^[69] Furthermore, aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory.^[70] The estrogen-like effects of these salts have led to their classification as a metalloestrogen.

The effects of aluminium in antiperspirants has been examined over the course of decades with little evidence of skin irritation.^[6] Nonetheless, its occurrence in antiperspirants, dyes (such as aluminium lake), and food additives is controversial in some quarters. Although there is little evidence that normal exposure to aluminium presents a risk to healthy adults,^[71] some studies point to risks associated with increased exposure to the metal.^[72] Aluminium in food may be absorbed more than aluminium from water.^[73] Some researchers have expressed concerns that the aluminium in antiperspirants may increase the risk of breast cancer,^[74] and aluminium has controversially been implicated as a factor in Alzheimer’s disease.^[75] The Camelford water pollution incident involved a number of people consuming aluminium sulfate. Investigations of the long-term health effects are still ongoing, but elevated brain aluminium concentrations have been found in post-mortem examinations of victims, and further research to determine if there is a link with cerebral amyloid angiopathy has been commissioned.^[76]

According to The Alzheimer’s Society, the overwhelming medical and scientific opinion is that studies have not convincingly demonstrated a causal relationship between aluminium and Alzheimer’s disease.^[77] Nevertheless, some studies, such as those on the PAQUID cohort,^[78] cite aluminium exposure as a risk factor for Alzheimer’s disease. Some brain plaques have been found to contain increased levels of the metal.^[79] Research in this area has been inconclusive; aluminium accumulation may be a consequence of the disease rather than a causal agent. In any event, if there is any toxicity of aluminium, it must be via a very specific mechanism, since total human exposure to the element in the form of naturally occurring clay in soil and dust is enormously large over a lifetime.^[80]^[81] Scientific consensus does not yet exist about whether aluminium exposure could directly increase the risk of Alzheimer’s disease.^[77]

Effect on plants

Aluminium is primary among the factors that reduce plant growth on acid soils. Although it is generally harmless to plant growth in pH-neutral soils, the concentration in acid soils of toxic Al³⁺ cations increases and disturbs root growth and function.^[82]^[83]^[84]^[85]

Most acid soils are saturated with aluminium rather than hydrogen ions. The acidity of the soil is therefore a result of hydrolysis of aluminium compounds.^[86] This concept of “corrected lime potential”^[87] to define the degree of base saturation in soils became the basis for procedures now used in soil testing laboratories to determine the “lime requirement”^[88] of soils.^[89]

Wheat‘s adaptation to allow aluminium tolerance is such that the aluminium induces a release of organic compounds that bind to the harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism. The first gene for aluminium tolerance has been identified in wheat. It was shown that sorghum’s aluminium tolerance is controlled by a single gene, as for wheat.^[90] This is not the case in all plants.

References

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^ Abreo, V.. “The Dangers of Aluminum Toxicity”. http://www.bellaonline.com/articles/art7739.asp. Retrieved 2009-05-05.
^ Slanina, P.; Frech, W; Ekström, LG; Lööf, L; Slorach, S; Cedergren, A (1 March 1986). “Dietary citric acid enhances absorption of aluminum in antacids”. Clinical Chemistry (American Association for Clinical Chemistry) 32 (3): 539–541. PMID 3948402. http://www.clinchem.org/cgi/content/abstract/32/3/539. Retrieved 2008-10-09.
^ Van Ginkel, MF; Van Der Voet, GB; D’haese, PC; De Broe, ME; De Wolff, FA (1993). “Effect of citric acid and maltol on the accumulation of aluminum in rat brain and bone”. The Journal of laboratory and clinical medicine 121 (3): 453–60. PMID 8445293.
^ Darbre, P. D. (2006). “Metalloestrogens: an emerging class of inorganic xenoestrogens with potential to add to the oestrogenic burden of the human breast”. Journal of Applied Toxicology 26 (3): 191–7. doi:10.1002/jat.1135. PMID 16489580.
^ Gitelman, H. J. “Physiology of Aluminum in Man”, in Aluminum and Health, CRC Press, 1988, ISBN 0824780264, p. 90
^ Ferreira, PC; Piai Kde, A; Takayanagui, AM; Segura-Muñoz, SI (2008). “Aluminum as a risk factor for Alzheimer’s disease”. Revista latino-americana de enfermagem 16 (1): 151–7. doi:10.1590/S0104-11692008000100023. PMID 18392545.
^ Yokel RA, Hicks CL, Florence RL (2008). “Aluminum bioavailability from basic sodium aluminum phosphate, an approved food additive emulsifying agent, incorporated in cheese”. Food and chemical toxicology 46 (6): 2261–6. doi:10.1016/j.fct.2008.03.004. PMC 2449821. PMID 18436363.
^ Exley C, Charles LM, Barr L, Martin C, Polwart A, Darbre PD (2007). “Aluminium in human breast tissue”. J. Inorg. Biochem. 101 (9): 1344–6. doi:10.1016/j.jinorgbio.2007.06.005. PMID 17629949.
^ Ferreira PC, Piai Kde A, Takayanagui AM, Segura-Muñoz SI (2008). “Aluminum as a risk factor for Alzheimer’s disease”. Rev Lat Am Enfermagem 16 (1): 151–7. doi:10.1590/S0104-11692008000100023. PMID 18392545. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-11692008000100023&lng=en&nrm=iso&tlng=en.
^ Hawkes, Nigel (2006-04-20). “Alzheimers linked to aluminium pollution in tap water”. The Times (London). http://www.timesonline.co.uk/tol/news/uk/health/article707311.ece. Retrieved 2010-04-07.
^ ^a ^b Aluminium and Alzheimer’s disease, The Alzheimer’s Society. Retrieved 30 January 2009.
^ Rondeau, V.; Jacqmin-Gadda, H.; Commenges, D.; Helmer, C.; Dartigues, J.-F. (2008). “Aluminum and Silica in Drinking Water and the Risk of Alzheimer’s Disease or Cognitive Decline: Findings From 15-Year Follow-up of the PAQUID Cohort”. American Journal of Epidemiology 169 (4): 489–96. doi:10.1093/aje/kwn348. PMC 2809081. PMID 19064650.
^ Yumoto, Sakae; Kakimi, Shigeo; Ohsaki, Akihiro; Ishikawa, Akira (2009). “Demonstration of aluminum in amyloid fibers in the cores of senile plaques in the brains of patients with Alzheimer’s disease”. Journal of Inorganic Biochemistry 103 (11): 1579–84. doi:10.1016/j.jinorgbio.2009.07.023. PMID 19744735.
^ “Alzheimer’s Disease and Aluminum”. National Institute of Environmental Health Sciences. 2005. http://www.niehs.nih.gov/external/faq/aluminum.htm.
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^ Horst, Walter J. (1995). “The role of the apoplast in aluminium toxicity and resistance of higher plants: A review”. Zeitschrift für Pflanzenernährung und Bodenkunde 158 (5): 419–428. doi:10.1002/jpln.19951580503.
^ Ma, Jian Feng; Ryan, PR; Delhaize, E (2001). “Aluminium tolerance in plants and the complexing role of organic acids”. Trends in Plant Science 6 (6): 273–278. doi:10.1016/S1360-1385(01)01961-6. PMID 11378470.
^ Turner, R.C. and Clark J.S. (1966). “Lime potential in acid clay and soil suspensions”. Trans. Comm. II & IV Int. Soc. Soil Science: 208–215.
^ “corrected lime potential (formula)”. Sis.agr.gc.ca. 2008-11-27. http://sis.agr.gc.ca/cansis/glossary/corrected_lime_potential.html. Retrieved 2010-05-03.
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v · d · eAluminium compounds

AlAs · AlB₂ · AlB₁₂ · Al(BH₄)₃ · AlBr₃ · AlCl · AlCl₃ · AlF · AlF₃ · AlH₃ · AlI₃ · AlN · Al(NO₃)₃ · AlO · Al(OH)₃ · AlON · AlP · AlPO₄ · AlSb · Al₂(MoO₄)₃ · Al₂O₃ · Al₂S₃ · Al₂(SO₄)₃ · Al₂Se₃ · Al₂SiO₅ · Al₄C₃

Alkaline earth metals

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Unknown chem. properties

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This information originally retrieved from http://en.wikipedia.org/wiki/Aluminum
on Monday 8th August 2011 9:06 pm EDT
Now edited and maintained by ManufacturingET.org

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