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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: comp.graphics,comp.misc,misc.wanted,sci.chem,sci.misc,sci.engr
Subject: Re: Advice and Ideas Wanted For the Precision Cutting of Paper
Summary: Consider electrochemical machining
Message-ID: <12498@milton.u.washington.edu>
Date: 7 Dec 90 04:38:14 GMT
References: <18061@netcom.UUCP>
Organization: University of Washington, Seattle
Lines: 28

In article <18061@netcom.UUCP> noring@netcom.UUCP (Jon Noring) writes:
>
>I'm currently working on a project which requires the precision
>cutting (within 0.01 inch) of paper or paper-like material using a
>computer to guide the cutter.  The cut shape will, in general,
>be quite complex.

	Chemical and electrochemical machining (etching) routinely can
give this sort of precision.  One can simply contact-print a negative
onto a treated metal surface, develop the photoresist, and etch
for a few minutes.
	Homebrew kits for doing this are available (for making printed
circuits).  Typical etchant is ferric chloride/HCl at moderate
temperature.  A large beaker on a hotplate, with some agitation
mechanism, is an adequate etching bath.  A UV sunlamp and spray can
of KPR photoresist, and perhaps some Kodalith film (for making
negatives) complete the required equipment.
	Copper, brass, and stainless steel shim stock would
be possible materials.  Check the yellow pages for 'photochemical
machining' or 'chemical milling' if you want to job it out.

	I have done this from computer-plotter artwork at full scale
and at 4x scale (the latter is preferred, but requires a copy camera
to get the correct scale on a 1:1 negative.)  It's slow work, but easy.
To actually cut the material, you will want to etch from both sides
simultaneously, with careful registration of the artwork.

	John Whitmore


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