I am building a CNC type PCB milling machine. Does anyone know of any software that will take as input either an HPGL file or a Gerber file and convert it so that it plots the outlines of the tracks (ie. suitable for PCB milling ? Have any of you folks used TurboCNC in this way for home brew millers.
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I do not think you want the outline, as there is no such thing as having a zero width milling tool - except a laser beam in comparison with the width of desired cutouts. Gerber format is good, in that it gives the tool size and the route (movement) to follow; the resulting cutouts will then look the same as what one would see with a Gerber viewer or plotted on a film. As far as i could find, all Gerber viewers require $$ to obtain (if you want to be able to use them for more than 15 days), and there are almost no Gerber converters (ore require $$ as mentioned). HPGL as far as i can determine, give zero info on tool size, and would seem to be unusable for your purposes. The Gerber format is well described, so one could write a program for interpreting to milling requirements.
Robert Baer wrote: : As far as i could find, all Gerber viewers require $$ to obtain (if : you want to be able to use them for more than 15 days) . . . .
Actually, the gEDA Gerber view gerbv is open-source and no-cost. If you're building your own PCB milling machine, you might be interested in hacking the code to drive your machine. It's not a complete solution, but it might be a good starting point.
Actually there are a number of free Gerber viewers (without restrictions), however the problem is that you don't want a Gerber viewer as a viewer simply views files as the name suggests.
Gerber format on it's own is not adequate. As mentioned it gives your route movement and width. However it overlaps those routes at junctions which would cut your traces at any corner. Secondly, what you actually want is not the width but an offset of 1/2 the width plus 1/2 the width of your bit from the center line of the Gerber aperture. So Gerber on it's own is completely inadequate except as a starting point for manipulation/generation/analysis of your actual route path.
The existing commercial applications of this nature use Gerber as their preferred input format. They then calculate and generate the actual router paths and output these in a proprietary format.
One route worth investigating would be output the HPGL as you'll probably end up with the outlines of the tracks there. Next get a hold of HPGL2CAD from GuthCAD in Australia to convert the HPGL to DWG/DXF. You can then load the DXF file into a cheap CAD package, or AutoCAD, generate some lines which are offset from the existing ones then save these for milling.
Another route would be to get a CAM editor (like GC-CAM) and use the Gerber files. Import the gerber files in to the CAM editor, copy the original layers, change the copied layers to a different aperture table and increase the apertures of this table, then create a new layer for output being a composite of the new enlarged layers, plus the original layers as a negative over the top, therefore leaving you with the outlines. You might be able to get some output from this that's useable and easily convertable for your needs.
The long-winded way, if all else fails, of using this output may be to plot it out, re-scan it in and use some vectorisation software, like CorelTrace, Scan2CAD, Adobe Illustrator etc. to get back to a vector form.
Anyway, some ideas to start with.
"Douglas Simmonds" wrote in message news:dc8nql$52p$ email@example.com...
Thank you very much for the input. It seems surprising that if you want to mill a pcb you will need the contour outlines yet none of the hobby level PCB CAD tools seem to export this. Maybe it is time for me to put on my programmer's hat and pull out a copy of the Gerber specification !
The command-line tool hp2xx will convert HPGL files to a variety of formats, both vector- and raster-oriented. One of these may be more convenient for you to deal with.
Windows version at
However, it is not clear why Gerber format would not be suitable. Your primary task would seem to be to get the originating application to produce the Gerber files with a constrained set of apertures (i.e. corresponding to the milling tools you have).
Exactly ! Generating the photoplots using Gerber I understand completely. But I need the inverse of the pattern to run a *milling machine* because I need to mill out the Copper around the plottted tracks !
I agree; Gerber is better in that it specifies aperture size/shape which can be interpreted as what cutting tool to use. And this business about "outline" is extremely puzzling. Any cutting tool other than a lazer will cut "beyond" that line by one-half of its diameter and so cut beyond the desired pattern as expressed in the "outline" interpretation of a Gerber file.
NOW we have the required info! That is a color of a different horse! And you *still* do not want or desire "outline". What you want is the *edge* of the cutting tool to follow the outline. So, if the cutting tool is not a lazer beam then you want to cut where a "fill" with a given relief would otherwise go. That relief would be half the cutter diameter. That means the inner corners would be rounded. Write the conversion program in PostScript...
You can generate an outline-only trace for each routing layer from Vutrax once you have a finished artwork. The feature is contained in a groundplane generating facility selected using [Outline Etch] from (Tools > Routing > Groundplanes >
Build Rules > Outline Etch) and can be found in the manual by searching for 'outline etch'.
Once you have the outlines you can output them in any Vutrax PLOT format which includes HPGL (with controlled pen size), Various Gerber formats (including ability to work with a single aperture which would suit milling), various milling specific formats, bit maps, Postscript etc.
You can download all the stuff you need for Linux or Windows from
(Main UK site)
(Central Europe Mirror) Free for evaluation and DIY size projects up to 256 pin with no time limits, no required internet access, or other tricks. The download includes a full tutorial for schematic through routing and PCB layout and output.
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