Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

If you do not have a rotary table it is simple to make one since there is
zero force on the subject. A 100 tooth gear will give you accurate
indexing.

No art work is needed for the critical lines, either optical projection or a
laser line source.

Bertho



From: Rick Sparber Sent: Saturday, March 23, 2013 22:12
Bertho,
I was planning on driving the cylinder with a clockwork mechanism and
"roasting" it under my UV light. If that gives poor results, I will
certainly try your suggestion.

Rick

-----Original Message-----
From: Boman33 Sent: Wednesday, March 20, 2013 6:41 PM

If absolute best accuracy is wanted, coat the part with photoresist and
mount it on an accurate turntable. Set up an optical projector projecting
just one narrow line. Lock everything down and in a darkroom expose the
first line, change the turntable to the next line, expose and so on.

When done, the calibration accuracy is only limited by the turntable
accuracy, the centering of the part on the turntable and the roundness of
the part. The optical system never moved so it should be stable as long as
there are not any temperature gradients.

A second pass can be run projecting the numbers a required.

Bertho






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