At 18:09 24/07/97 +0930, Mike wrote:
     <snip>
     >>>      On a laser printer the result is camera-ready copy. >
     >I was reading some newsgroups that suggested lasers were bad gnus for pcb
     >artwork - they are fine in one dimension, but owing to the high
     possibility >of roller slippage, bad in the other.   You could probably
     compensate on a >s/s board, but d/s or multilayer?


     *********
     Unless the printer is pretty ragged out, the major error is caused by the
     paper stretching, and shrinking as it's heated to 9000 deg in the fuser.

     There are Gerber View/Edit programs (http://WWW.ECAM.com/) that allow you
     to scale the X and Y dims independently.  This allows you to compensate a
     little for the error that a laser printer adds.  Draw something like a 6
     inch by 6 inch square with your PWB CAD program.  Generate the Gerber file,
     print it, and measure it after the paper cools.

     Figure out how much stretch you need in each direction, and use those
     numbers as scaling factors in the Gerber edit software.  Print again, and
     Vola! Still not perfect, but an improvement.

     (Still, It's hard to beat AP Circuits (http://www.apcircuits.com/).  Just
     email the Gerber files, and get a board with plated thru holes in a few
     days.)

     Joe