Re: [CAD_CAM_EDM_DRO] big silicon, was Re: re:RE: re:RE: Epoxy Granite, SPDT glass

It doesn't matter how good the scales are if the machine is not
stable,temperature,humidity and floor the machine will not be stable
enough. I was at the Nist facility a few years ago and to make a machine
stable enough for .0001 in they had Heidenhain scales that fed a computer
that had thermal sensor input from all parts of the machine and the position
feedback was compensated for before it went to the CNC controller. The
facility was also kept at 68 deg F and 30 % humidity.


Harko

On 3/1/06, Elliot Burke <elliot@...> wrote:
>
> Jon,
> One can imagine such a big crystal though, at the present rate of silicon
> increae, it will be, what, 100 years? till we see 2 m silicon used in
> microlithography. Of course that will have to be fabbed in zero g.
>
> Silicon can be cast into very nice optical elements. A place I used to
> work
> had one fellow in a room full of glassware doing just that. He purified
> the
> silicon and cast it into hemispherical shells about 6" diameter. There
> wasn't any reason why they couldn't have been made larger. This is of
> course polycrystalline silicon. It diamond turns very nicely.
>
> Silicon is a fine material for lenses and mirror substrates; these require
> similar properties to machine tool structures. The melting point is
> pretty
> high, 1414 °C. It has low expansion, high thermal conductivity, high
> stiffness/weight, low toxicity.
>
> For the problem of making large optical elements in an interferometrically
> controlled grinding and polishing machine, has anyone worked out how rigid
> such a thing needs to be to prevent operational forces from distorting the
> structure and reducing accuracy? Even if the cutting forces were taken
> out
> of the structure separately from the metrology, rotation causes various
> stresses, there are sure to be other problems.
>
> The concept of a floppy machine making perfectly smooth cuts because the
> scales are used to provide feedback to correct cutter location; that would
> be fun to see. I think that's what Jack Hudler is proposing. Wish him
> luck!
>
>
> regards-
> Elliot Burke
>
> Message: 9
> Date: Tue, 28 Feb 2006 20:34:06 -0600
> From: Jon Elson <elson@...>
> Subject: Re: re:RE: re:RE: Epoxy Granite, SPDT glass
>
> Elliot Burke wrote:
>
> >Jack,
> >The PDF referenced below does not mention diamond turning glass. Lots
> for
> >crystal materials can be diamond turned, maybe you could get a 2 m
> silicon
> >blank?
> >
> >
> >
> I can guarantee with absolute certainty that nobody makes 2 M Silicon
> crystals.
> They are up to 12" or 300 mm, and that is already HUGE for a grown
> crystal!
>
> Jon
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