Re: [CAD_CAM_EDM_DRO] Re: Make your own linear scales

On Fri, 1 Mar 2002, ballendo wrote:

> What is your "gut" feeling about a homeshop guy or gal creating glass
> scales like this? Could we do the etching necessary?

I used to do anisotropic silicon etching in an optics R&D lab. You'd
probably laugh yourself silly if you saw our setup. (Except for the final
etch phase, which was one of the most baroque setups I've ever seen, most
of our chemical baths were done in Tupperware in a fume hood.)

I think it would be well within the reach of the home shop machinist, with
a couple of caveats:

1 - Your results depend hugely on the quality of your master. Laser
printed masters scatter toner everywhere. They aren't going to work that
great unless you've got a fantastic printer. If you can find a broken
scale or one that's been removed from equipment, clean it carefully and
use this as a master.

2 - Metal etchants are really nasty. Use with great caution.

3 - Getting a photoresist on your glass blank may be problematic. We made
a custom spin-coater for what we were doing (relatively large blocks of
silicon), but that would be unwieldy for large glass scales, and would be
major pain to make, just to get a scale. If you can get glass with an
evaporated metal coating, and get it pre-coated in photoresist, so much
the better.

4 - Compare your costs to the cost of some glass scales. If you find
yourself spending a couple thou making equipment to make these things,
you're fighting a losing battle.

This sounds a lot like the process that's used for making photolithography
masks for the integrated chip industry: glass with evaporated metal, which
is then photographically patterned and etched. If you're thinking of
doing this in your home shop, that's where I'd start my library search.

Tom