Re: [CAD_CAM_EDM_DRO] Re: making PC boards

Alan Marconett KM6VV wrote:

> Jon,
>
> That's quite impressive. Must be for more then a "hobby"! I'd heard
> that the laser printer wasn't exactly scaled. But how do you build a
> laser photoplotter?

See http://www.artsci.wustl.edu/~jmelson/photoplot.html

> What are the plots from?

There are 2 variants of the RS-274 G-code that are used by the printed
circuit
board industry to make photo plots for the copper layers, and to drill
the holes.
Most PCB software generates these files.

> I can guess that the
> heart of it is an X-Y positioning system, then several apertures of
> some
> sort?

No, that would be very slow - doing it like a pen plotter. Plot times
would be on
the order of hours. This is a RASTER plotter. The computer generates
raster
data by examining all the primitives to be drawn, and then sends it
rapidly to
the plotter. It spins the drum at 10 RPS, thus writing ten 1-thousandth
inch
wide raster lines per second, or .6" per minute. So, a 6" long plot
takes
10 minutes.

> Also obviously a laser! Do you use Gerber format (which seems
> somewhat related to RS274D??

Yes.

> g-code??)? Do you use protel
> (http://www.protel.com/)

> There is a freeware and a commercial
> version.

No, that is an antique. I use a commercial Protel version.

> The NC file (holes) from the PCB program is then correct for
> CNC? Do you convert Gerber to CNC to run your photoplotter?

The "Gerber" file, RS-274D, IS a CNC format, but it contains a bit more
information, or at least organizes it in a way that means a little bit
more
than plain G-code. I do not convert it to some other form, other than
the
final raster data that goes to the photoplotter.

> That's all
> quite impressive!

And, it took 10 years, on and off, to build it, too!

Jon