Re: [CAD_CAM_EDM_DRO] Help: PCB Trace Milling Software

Alan Marconett KM6VV wrote:

> So how do we get from Gerber files to CNC files? As you observe, the
> Gerber "plots" each trace, what we want is contours AROUND the traces!
>
> I examined an HPGL PCB plot file (see View Companion), and studied how
>
> multiple pen lines were combined to draw a trace.

I figured out a VERY crude algorithm to do this, if anyone wants to try
it.
First, you map the extent of the drawing onto a bitmap. You then draw
in the
traces and pads, with the actual width or dimensions of the object. For
instance,
if the grid is 1 mil, then a 50 mil trace would be drawn by filling in a
50 bits wide
track from start to finish.

After this is all done, both traces and pads, you could raster through
the thing,
identifying all points where you cross from one 'color' to another. You
have to do
this in both axes to make sure you completely surround the traces and
pads.
This should define a 'border' as a closed pattern of border bits.

A second pass could define all separated borders by starting randomly at
the
first border seen and following all the way around its edge until you
get back to
the starting point, and numbering all these bits as part of border # 1.
You then scan for the next unmarked border, and follow it, marking it
#2.
You repeat this until there are no unmarked border bits left in the map.

You can now check each border to see which side it encloses from some
starting
point, and create offset tool paths to cut them out.

This actually doesn't sound so difficult, now that I have kind of
figured
out how it can be done. It could be a memory hog for large boards,
however.

Jon