Outline

Introduction

Plastics, ceramics, and composites have different structure and properties than metals
Principles of material selection and manufacturing are different
Large, complex shapes can be formed as a single unit
Processes can produce a near perfect shape and surface product

A successful plastic product is manufactured so that it satisfies the various mechanical and physical property requirements
The preferred manufacturing method is determined by the desired size, shape, and quantity
There are three main different types of polymers:
- Thermoplastics
- Thermosetsd
- Elastomers
  - TPEs – Thermoplastic Elastomers (PDF)

Each process has limitations and design considerations

Shrinkage in casting

Solidification issues

Part removal and ejection

Surface finish

Section thickness

Thick corners

Inserts

Metal (brass or steel) may be incorporated into plastic products to enhance performance
Threaded inserts
May serve as mounting surfaces
Often used for electrical terminals

Finish and appearance of plastics is important to consumers

Decorations or letters can be produced on the surface of the plastic, but may increase cost

Processes should be chosen so that secondary machining is minimized

If parting lines will result in flash, the parting lines should be placed in geometrically easy locations (i.e. corners and edges) if possible

Plastics have a low modulus of elasticity, so flat areas should be avoided

Flow marks may be apparent, so dimples or textured surfaces can be used

Holes should be countersunk