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

How about the scales which are a tube filled with precision ball bearings.
You then use a few coils on the sensor and have the sensor slide along the
stainless tube. As the coils get closer to each ball bearing they create the
phasing signals. Sounds like a beast to calibrate, but sounds easy enough to
make and is impervious to contamination.

Art
Master5 Software
http://users.andara.com/~fenerty/master.htm

----- Original Message -----
From: "Tom Benedict" <benedict@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, March 01, 2002 11:14 AM
Subject: 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
>
>
>
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