John,
The cones on our machine were just long enough to accept a screw in
nozzle that put the gas or air output in the focal plane. The screw
in nozzle was made of brass and came with different hole sizes but
the one we used the most was .060 inches. When they wore out I would
put them in a lathe and bore the hole to a larger size, face off the
tip and use them again.
The air or gas pressures were not very high, probably around 10 to 20
psi. You can experiment with this pressure for best results. Your
cutting speed and edge quality will be greatly improved using the
compressed air.
Your moving XY table is the best way to go because trying to align
the beam with the flying optics would be difficult for a hobby setup.
The gantry table allowed a smaller machine footprint but with very
complicated alignment procedures.
I have never tried any kind of engraving or etching of PCB laminates
with a laser but your idea would probably work. Some of the big PCB
lasers use a type of "shadow mask" to drill all of the holes in one
operation. The mask is kind of like a big negative film or metal
plate with clear holes where the laser power comes through and burns
through the laminate. The available laser power is divided across all
of the openings to form the holes. I saw something like this at the
NEPCON show several years ago and it was quite expensive, more than
$600,000.
I would also like to get some high power laser diodes since I have
several really nice CNC controlled XY tables that could be
retrofitted. That would be a great machine to have around for cutting
plastics and wood.
I use dry film photoresist and silk screening for making boards and
will probably not try the laser method. Most of my boards are short
runs on photoresist and I always keep some spare coated panels handy
for a quick job. Any large jobs are run with screen printing.
Tom
--- In
Homebrew_PCBs@yahoogroups.com, "John Myszkowski"
<myszka_us2000@y...> wrote:
> Hi Tom,
>
> I wouldn't mind the thinner kerf, also the power/area would
increase
> as well I suppose.
>
> The air funnel idea is a good one. I've been thinking of
implementing
> something like that. How much air pressure/flow would you suggest?
>
> I move my work in the X-Y direction (modified plotter). I want to
> avoid as many optical paths as possible. In other words, the less
> bends the better. I have too little power to spare as it is.
>
> The PCB resist etch idea will probably work fine. All you need to
do
> is vapourize the thin resist layer. The copper won't be touched
(for
> obvious reasons). An acrylic cage keeps any stray beams inside the
> work area.
>
> I would love to get my hands on one of the high power laser diodes.
> They would be perfect for resist etching. It would keep the overall
> size of the machine to a desktop size. You could probably retrofit
> any XY plotter to work with a laser "pen".
>
> John M...
> ==============