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

hi

i have the 7475a also.
and i think it is good enough for making pcbs with components with leads,
and track with 0,3mm.
i have a pen for 0,18mm, this is quite close to the mechanical resolution
you can get with that setup.

you have to tape the pcb down on a piece of paper if it isn't big enough
(also the metal rollers would scratch it ((@Jan Rowland the metal rollers
are the driven ones, the rubber only for counterpressure.)

please don't use a heavy pen (forget about all that ohp pen scrap), use a
short metal tip pen instead.
this results in much more stable movement (at the corners you get "drops"
with ohp pens)
and set to suitable speed.

the alignment with double sided plot is really, really a problem.
i didn't think about it too much until now... (i still have some
photocoated clad here and do not need plotting)

one idea would be to get the pen to stop at a certain position and align
the board then.
should be possible with some hpgl command or transfering the hpgl file in
parts.

the other idea would be to use a real flatbed plotter.. ;-)

third idea:

use ohp transparency to tape pcb to.
then make a good edge on the plotter plastic.
so you can see your "target" through the transparency when aligning.
this is a targed referenced to the plotter frame, so differences in
transparency alignment will change nothing.
just like using a flatbed then i guess.

regards
st