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

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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