Re: [CAD_CAM_EDM_DRO] Re: taig pick and placing

Graham Stabler wrote:

> Sounds like a real ordeal, I wonder what they did before these "labour
> saving" devices.
>

Oh, a friend of mine cut a doorway between what essentially were
two houses with a common wall. He ignored my advice of using a
diamond saw, and rented a six foot tall jackhammer. The mess
was incredible! He had 1/4" concrete dust over everything
within 20 feet, and both entire houses, all 3 floors, were
covered with concrete dust, the entire place was a uniform tan
color, walls, floor and even ceiling! Windows, too. It took
them two months to clean up the mess.

I hired out the backbreaking labor, and am darn glad I did. My
mess was limited to a fine dust film for a couple feet inside,
plus lots of mud tracked everywhere on people's shoes. Not much
cleanup required at all!

> Experiments on etching are worth their weight in gold, I had terrible
> trouble for a long time and I tried everything, turned out that the
> light box lid was faulty and the art work was not being pressed
> against the pcb (only sometimes just to make it worse).

Oh, I already had the technology to make quite commercial
quality PC boards here. The only thing lacking is plated
through hole capability. I made my own laser photoplotter with
1000 x 1000 dot/inch resolution, writing onto Agfa litho imaging
film. I then print these onto DuPont Riston dry film
photoresist. I got a Kepro dry film laminator through eBay when
a guy was shutting his PCB shop down. (Maybe it was before
eBay, too, it was a long time ago.)

As for the exposure, I have my own system. I assemble the top
and bottom images together with rubber cement and a spacer the
same thickness as the material to be exposed onto. A clear
spacer to see the alignment through, and some piece of scrap
material for the gluing. I put it on a light table for the
alignment. When the glue is dry, I pull out the clear spacer
and slip in the board or shim material. In either case, the
material has photoresist on both sides already. Then, I slip
this between two pieces of thin Plexiglas, one of which has a
border of spacers and an O-ring around the spacers. The other
piece has a pipe fitting connected to a vacuum pump. When I
turn on the pump, it suchs the two pieces together, and holds
the whole assembly rigidly against the material to be exposed.

I have a light box with 4 blacklight bulbs and an aluminum foil
reflector. I set that facing down onto the Plexiglas vacuum
frame and expose one side. When done, I flip the vacuum frame
over and expose the other side, never breaking the vacuum seal.

This has worked real well for PCB work, and seems to work fine
for the brass shim stock stencils, too.

[CAD_CAM content: The photoplotter is a CAD_CAM machine, and I
wrote my own CAM software to read the "Gerber file" dialect of
G-code and turn it into raster pixels for the photoplotter.]

Jon