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

On Fri, 1 Mar 2002, Carey L. Culpepper wrote:

> What about etching the coating on the backside of a mirror?

If you remove the backer paint first, that might actually work. Still
need to get a photoresistive layer on first, but I don't see why not.

(The only photoresistive layers I'm familiar with are spin-coat
photoresists. I'm pretty sure photomask manufacturers use something else,
so I'm kinda getting out of my depth here.)

Tom

> Tom Benedict wrote:
>
> > 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
> >
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