Re: gEDA-user: Would like to use geda tools to make .dxf file for pcb cnc milling.

[dfro@xxxxxxxxx]

Bert,

I do think a dxf exporter can attract thousands of people to geda tools. 
The cnczone.com site alone is huge. And cnc machines need a lot of 
pcb's. As an example, I have used gschem, gsch2pcb. pcb, and gerbv to 
make a 'signal opto-isolator board' and a 'photo-interrupter limit 
switch board' for my stepper controller box. I farmed out the pcb 
manufacture to a fabrication company, but in the future I would like to 
mill them myself.

> 
> FWIW, I want to do a DIY cnc router for pcb and front panels someday ...
> 
> My goal with the pcb-dxf-hid was/is to achieve some sort of 3D model in
> FOSS software that can read/parse DXF and do 3D presentation/modeling
> (Blender and brl-cad comes to mind).

I create and light cad scenes in blender. I then export the scene to 
luxrender, an unbiased photorealistic rendering program to render an 
image. The work people are doing with LuxRender is amazing. Blender 
imports and export dxf files, which is good news.

> Anyways, I have ample spare time to do serious coding on this one, maybe
> things will change after this summer, who knows ?
> 

I am excited that you are motivated to create a dxf exporter!

A full-featured, open-source cam program is a hole in the FOSS tool 
chain, so far. Gcam (http://gcam.js.cx/index.php/Main_Page) looks like 
it is making steady progress, but so far I have not been able to get it 
to work without freezing my computer. The cnc machinists that I know are 
using non-free cam-bam and sheetcam software to create their g-code. 
Lazycam also looks interesting.

People are milling pcb's with very fine traces - i.e. for SMD 
components. With a rigid and accurate machine, very fine work can be 
done. This company sells pcb milling machines packaged with their own 
pcb artwork software: http://www.lpkfusa.com/protomat/s-series.htm

I plan to maka a similar milling machine out of epoxy-granite. Epoxy 
granite is a relatively cheap way to cast in molds massive, rigid 
machines of any size. On cnczone.com there is a huge thread where some 
very dedicated people are doing research to create an open-source epoxy 
granite formula: http://www.cnczone.com/forums/showthread.php?t=30155

It is proving difficult to match the performance of the proprietary 
formulas. It is very hard to get the epoxy to wet out all of the 
aggregate and flow at 8% to 11% epoxy, which is what the pros are doing. 
For my purposes I think the e/g researchers are far enough along with 
the current formula for me to make some steel reinforced e/g machines. I 
get my e/g to flow on a vibration table at around 20% epoxy. At 20% 
epoxy there is a loss of strength. I plan to make up the loss of 
strength with some embedded steel rebar and some extra casting 
thickness. The mass and the vibration damping is the real advantage of 
e/g. Epoxy-granite has ten times the damping properties of cast iron. 
That means longer tool life and finer surface finish on parts, which is 
what you want if you are milling pcb's!

I hope you and others find this interesting.

Thanks,
Dave


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