13. Extension Theory

You do not need to know this for your studies, but we have included it because it is an interesting new way of making things.

There is now a another CAM method called Stereolithography pronounced
Stereo - Lith - ography

It makes use of a laser beam and a special liquid to build up the component one tiny layer at a time.

StereoLithography is a fascinating process that turns 3-D CAD drawings into 3-D physical components in a matter of hours.

It makes use of two things

• A laser beam that traces out a pattern on the surface of a liquid
• A special liquid that solidifies when touched by the laser beam.

A 3D CAD file is loaded into a computer that controls a scanning laser beam.
The steps needed to create a component are as follows:-

1. A table platform is placed just beneath the surface of the liquid.
2. The laser beam is made to trace out a pattern according to the CAD file.
3. The laser beam solidifies a thin layer of the liquid where ever it touches it.
4. The table is lowered a fraction of a millimeter
5. The laser beam traces out a pattern once again.
6. Table is lowered once again.
7. Repeat until the component is made.

So you begin with a very thin, solid shaped layer being formed on the surface. Then hundreds of layers later the component is finished.

The picture below show the types of components made by stereolithography.

A component made using stereolithography