Reading Assignment
Optional Reading
- Basic Fixture Design
- Low-Cost Jigs, Fixtures & Gages for Limited Production
- An Advanced Treatise on Fixture Design and Planning
- Advanced Computer-Aided Fixture Design
- Horizontal CNC Tombstones (Suburban tool video)
- Tube Fixture Design and Tolerance (PDF)
Fixture Examples
Outline
Lathe Fixtures
A lathe fixture must account for factors associated with a turning workpiece. Counterbalances may be necessary. Fixtures may attach directly to the spindle, or be held in the faceplate, collet or chuck already on the machine. Fixtures must clear any tooling or machine parts.
As with any machining setup, rigidity is fundamental to success. Always fixture components as rigidly as possible.
Some operations that are performed on a lathe (particularly boring) can be done with better success on a mill.
Below is an excerpt from Tool Design, MET331, Dr Simin Nasseri, Southern Polytechnic State University
- Since lathe fixtures are designed to rotate, they should be as lightweight as possible.
- Lathe fixtures must be balanced. While perfect balance is not normally required for slow
speed turning operations, high rotational speeds require the fixture to be well-balanced. In
most fixtures, balance is achieved by using counterweights positioned opposite the
heaviest part (or area) of the workpiece.
- Projections and sharp corners should be avoided, since these areas will become almost
invisible as the tool rotates and they could cause serious injury.
- Parts to be fixtured should, whenever possible, be gripped by their largest diameter or
cross section.
- The part should be positioned in the fixture so that most of the machine operation can be
performed in the first fixturing.
- Clamps should be positioned on rigid surfaces or areas before and after machining.
- Clamping over an area to be bored to a very thin-wall thickness could cause the part to
warp or deform, thus causing the hole to be bored incorrectly.
- As with other fixtures, some means of cutter setting should be incorporated into the
design. However, since the workholder will be rotating, this setting device should later be
removed.
- Whenever possible, standard lathe accessories should be adapted in the design of turning
fixtures. Lathe faceplates are an ideal method to mount large fixtures. Likewise, a standard
lathe chuck, or collets, can and should be modified for many fixturing applications.
Swing-up stops
Micrometer stops.
Plate Fixture
A plate fixture is useful when fixturing for 2-D feature placement (holes, slots, tapping, etc.). They are used primarily when only one face of the part will be machined.
http://www.konoco.com/samples.htm
Multipart or Multistation Fixture
http://www.konoco.com/samples.htm
Setup Gage
Set Block
Using a gage block to set tool.
Micrometer stop
http://www.cousinsuk.com/images/product/G4870_CMYK.JPG
Welding Fixtures
Welding fixtures can greatly increase the productivity of a welding operation. Aluminum is and ideal material for welding fixtures as it conducts electricity well and is light weight. Fixtures may also be constructed from steel or even wood (take fire precautions!).
Bicycle Frame Jig (Fixture)
http://www.cousinsuk.com/images/product/G4870_CMYK.JPG
MDF Bicycle Frame Jig (kickstarter)
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