Homebrew PCBs

John,

I agree with you about the odor in a circuit board plant. The dry 
film laminator was the odor that bothered me. We had all kinds of 
vents and fume scrubbers but it was still bad news. I keep in touch 
with some of the other shops that are still around and they tell me 
it's getting real tough to get ammonium hydroxide these days. Can you 
imagine exhausting some of those fumes to the outside? The cops would 
accuse you of running a meth lab!

My Mitsubishi laser used brass pins about 5" long that supported the 
work. They were spread out about 8" apart and screwed into a 
supporting framework. These pins were hex shaped and tapered to a 
point at the support end. Since they were brass the service life was 
very long and we only relaced a few. Non ferrous metals are hard to 
cut with a CO2 laser so the brass support pins seem to go forever.
I have seen other types of support systems that used interlocking 
sheet metal pieces that were cut with the laser. 

We also had a precision pin locating system for fixtures which we 
used most of the time for the small parts we made. I liked this method
because we used left over drill backup boards from the Excellon 
machines as fixture plates. I would clamp the masonite plate in the 
laser table and add about .1 inches or so compensation (G41 or G42)to 
the CNC program. Then the masonite was cut using the over compensated 
program which cleared a path through the masonite plate for the laser 
beam. The blanks to be cut would be taped down over the opening and 
cut. It worked good and we got double duty out of the drill backup 
boards. 

I should mention that we knew the exact XY positions for the tooling 
pins and we would cut these holes on the masonite using one of the 
Excellon routers. It was real handy to have both machines since we 
made laser tooling plates with the Excellon and special routing and 
multilayer fixtures with the Mitsubishi laser.

John,we are really off topic on this PWB list so if you would email 
me direct we could discuss these details at length.

Tom


--- In Homebrew_PCBs@yahoogroups.com, "John Myszkowski" 
<myszka_us2000@y...> wrote:
> Hi Tom,
> 
> I used to work at a "job shop" too at one time, for a few years. 
Many 
> years ago and for someone other than myself, but I learned quite a 
> bit. The owner was quite nice and let me learn all about the 
> bussiness. I would have stayed or got into my own, but for the 
> terrible smells. After a while it got to the point that I got 
almost 
> sick just thinking of the smell... :(
> 
> I was actually doing electronic design, so I just moved to a 
cleaner 
> place to work. And that was that for the PCB manufacturing 
experience.
> 
> Tom, I do have one question.
> What kind of table surface would you suggest for the laser cutter?
> I just have a throw away cardboard surface. With the compressed air 
I 
> would think there needs to be an exit somewhere, so a metal mesh or 
a 
> perforated surface or something with negative air pressure? Is 
there 
> something that works the best?
> 
> John M...
> =============
> 
> 
> 
> 
> > 
> > John,
> > 
> > I spent over twenty years in the printed circuit business as a 
> > commercial shop. We made all types of rigid boards up to ten 
layers 
> > and some flex boards as well. My main reason for getting into the 
> > business was to supply boards for my own products. The idea was 
to 
> > sell off the excess capacity as a job shop and get my boards at 
> cost. 
> > 
> > ...
> ...
> > TOM