🚀 go-pugleaf

rubin@chocktaw.cis.ohio-state.edu (Daniel Rubin) writes:

>Can the HP plotter correctly position a copper clad board?  I did not 
>know that it could handle material that thick.  If so this sounds like
>a much better route to take than messing with transfer sheets!

The modern HP plotters use a grit wheel drive system that relies on
"imprinting" the paper with the grit wheel pattern for proper repositioning.
It's more likely to work if you tape the board material to a stable piece
of paper.  But also be careful of plotters that have too high an 
acceleration.  Even if you set the speed low, it will try to slew
quickly when the pen is up.  The mass of the board may mess you up.

A potentially better solution is a flatbed plotter.  You may even be
able to find an HP 7220 or similar cheaper than a 7470.  Neither is
in current production.  Prices vary a great deal, depending a lot on
if you get it from an individual or a surplus equipment company.
One problem with the 7220, at least, is that it doesn't _normally_
lift the pen high enough to clear a 1/16" PC board, though a shortened
pen, or one not screwed into a holder all the way, can work.  Also,
for anyone with a 7220, be careful thinking you can modify the pen
stalls to hold a taller drafting pen:  the original design relies on
the pen top being constrained by the "roof" of the stall.  I found this
out the hard way ;-)

You can get pen holders for drafting pens pretty cheap from HP; the
holder is the part that the pen pickup "hand" knows how to hold.  That
could save quite a bit of futzing in the machine shop.  And if you
can get liquid ink of about the right consistency, a refillable drafting
pen might be just the ticket.

Many thanks to Dave for his trip around Austin testing pen inks!
Now maybe I can get my 7220 working on this, too!

Cheers,
Tom