Re: [CAD_CAM_EDM_DRO] Homebrew stereo Lithography

> > Yes, something close to that has been done. There are at least a couple of
> > rapid prototyping processes that result in a metal part.
>
> Has anyone built a homebrew machine to do Stereo Lithography
> (ie building up a 3D model from wax/polymer/powdered metals etc)?
> Microstation Modeller (a CAD program) exports STL files for this purpose.

First off, "Stereo Lithography" is the trade name for one of these
methods, not a general name for the rapid prototyping methods. The
powder based methods are 3d printing (use an inkjet printhead to
deliver a binder solution into loose powder so it can be held together
in the desired shape during firing or sintering) and Selective Laser
Sintering, which is a similar idea where the sintering is done bit by
bit by you guessed it, a laser. There is also another technology that
has been described as a CNC hot glue gun. Finally, there are some
varients on 3d printing that use waxy ink-jet inks that actually build
up.

Many of these technologies were developed in research settings not far
removed from 'homebrew', only with more time and money at their
disposal. You could probably duplicate them for your own
non-commercial hobby use (they are patented) if you wanted to badly
enough.

STL files are the industry standard starting point, however these are
a compressed format encoding triangular surface elements. Since none
of these technologies have the ability to build in an arbitrary order
(gravity) you will need software to 'slice' the part into a series of
raster and/or vector commands to your machine. (You probably want
something more compact than G code for all but the smallest parts).

> I was reading about a commercial machine once which had a vat
> of light-sensitive liquid polymer, and which was hardened (to the layer
> underneath it) by an overhead XY laser. When that layer was done,
> the part (sitting on a scissor elevator) was lowered fractionally further
> into the liquid, so that a tiny film of liquid again covered the part,
> and so the process repeated.

That is stereolithography

>
> Possibly this could be approximated with a liquid glue dispensor on
> a CNC controlled milling head.

Yes, if you can figure out how to get the glue gun to shut off a
stream cleanly. It's apparently been done fairly well.

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
30 Griswold Street, Cambridge, MA 02138
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