Re: [CAD_CAM_EDM_DRO] Help: PCB Trace Milling Software

Thanks Jon (and others),

for your thoughts on an algorithm to convert HPGL to "objects". I'm
gonna give it more thought, and try something.

My thoughts were similar, build the bitmap and a list of endpoints of
the pen lines. Find all neighbors of each pen line, build linked lists
of related pen lines: "islands" (objects). Sort lists and build
contours around each "island". Output list of contours. From there,
it's off to CAD/CAM for tool paths. Still rough algorithm.

I'm sure this all relates somehow to the .DLG (Hypsographic) files I
want to cut of the Felton valley area. And somehow .STL files come into
it!

I also got some more information from Eagle, and will see what it's
Gerber looks like on a small board (once I can run it!).

Alan So much free software, so little time!


Jon Elson wrote:

>
> 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
>
>
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