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

If you want to try and etch the coating on a mirror, use surface coated
mirror, it hase no protective coating on it.
They use them in copiers, cameras, etc. so that there is no refraction from
the glass. You can also "fume" a coating
of metal on. Ask someone who does ceramics, you need a kiln.

----- Original Message -----
From: "Carey L. Culpepper" <culpeppe@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, March 01, 2002 10:16 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Make your own linear scales


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