Re: Re: Hobbyists strike again

Andrew Werby wrote:

> From: Andrew Werby <drewid@...>
> [Even if he isn't, people keep asking me how they can do this. Is there a
> program out there (or a combination of programs, even) that simplifies this
> process so someone can go from a picture of a pc board to a g-code plot
> file? It would be nice if the hole-drilling were automated as well- am I
> dreaming? Does anybody out there cut pc boards with a mill, or is everybody
> convinced that etching is the way to go?]

If you never want to make two of a particular PCB, milling it may not be
so horrible, but it eats expensive carbide cutters for lunch. A typical
6" square board, double sided will just about use up a $20 milling tool.
This was confided to me by someone who sold the LPKF machine.
That didn't sound good! Plus, you have to flip the board over and
maintain registration for the 2nd side.

With etching, you develop and etch both sides of the board simultaneously.
If you are ingenious, you can also build a double-sided exposure frame
and print both sides of the board at the same time. Dry film resist for
both sides of a 6" square board costs about $2 maximum, including the
substantial waste with the big laminating machines. The initial investment
in the film and laminator is substantial, however. I don't want to minimize
that! The etchant costs maybe $.25 for that board, and it won't just burn
up suddenly like a milling bit. It will gradually slow down, so you have
plenty of warning that you need new etchant. When I got my used Kepro
bench-top etcher, I was horrified that it took 4 gallons of Fe2Cl3 to fill it
up, so I painted some bricks and plunked them into the tank. Unfortunately,
they only occupy a gallon of volume, so it still takes 3 gallons to fill.
But, I've been running on those same 3 gallons for about 4 years. Admittedly,
that is with VERY intermittent use, but it shows the chemical waste problem
is not so huge. When the stuff is depleted, you can just leave it exposed
and it will slowly dry out. Then, it is SOLID waste, and easy to dispose of.

Jon