Outline "tabs" with KiCad and pcb2gcode

Hi
I've just started using KiCAD and then processing the gerber files it produces using pcb2gcode (I use Debian Squeeze). This all seems to work brilliantly, except for one small problem that I still haven't solved....
Using the PCB_Edges layer of KiCAD, I can draw the edge of my PCB. I can Plot this and get a gerber file. I can then convert this to a gcode file using pcb2gcode, and the gcode produced would correctly cut the PCB out. BUT, I would really like to leave a few small support breakout tabs around the perimeter of the PCB so that it does not completely come away from the rest of the PCB whilst milling.
Does anyone know how to do this, other than by manually editing the gcode?

I posted a set of scripts I use a while back:
http://www.cnczone.com/forums/pcb_mi...ml#post1088593
I draw the outline leaving gaps and then convert the outline gerber using a different gerber to gcode tool. (I think it was from the linux cnc wiki)

I have not used them in a while, and I think there was a few bugs I have since fixed. Since there didn't seem to be any responses to the post, I never uploaded a new version. If you want to give it a try I can find my working version, clean it up, and re-post it. The one posted works, I think I just had some default settings reversed (+ depth instead of -, etc. that could be confusing)

My scripts also did some basic optimizing and smoothing of the paths. I wrote it for my own particular way I use it, but the settings can be tweeked for other uses. It is basically a front end for all the tools.

Thanks very much Iwill.
There were some issues with metric/imperial, but after a little tinkering, I've now got a gcode file out of 'gerber2emc2cl.py' based on the tool path that I drew into the comments layer.
That's exactly what I needed to cut out the PCB, but leave in the break out tabs.
Many thanks.

Glad it worked for you and that all that code I wrote is helping some one else!
I didn't test metric well since I work in inch.
Like I said, there were a few bugs. Next time I use it I will try to upload an update.
Got board and engraving work coming up soon.
If you find a bug let me know and I will try to fix it too (if I haven't already) for the future.

Hi
I've just learned that if you increase the 'offset' parameter for pcb2gcode to something way too large (like 20mm), then it will generate voronoi toopaths instead. it will give you a warning that it couldn't correctly use the offset you specified, but it will also generate the .png file so you can manually check if what it has produced is correct.
Although they don't look as pretty, they require less engraving time, need less accuracy, and can carry higher currents.

I've found that if I engrave the file produce by pcb2gcode, then load the drill file that was produced by the same software, that the drill holes don't line up with the engraved tracks and I have to re-align the x/y original by a few mm to get it to work correctly.
I don't understand why they are not aligned, and therefore I don't know if they are unaligned by a distance that I could calculate or automate, rather than doing it 'by eye' on LinuxCNC.
The input files to pcb2gcode were both produced by KiCad.
Can anyone help with this please?

I found the answer to my own question.....
If you run pcb2gcode twice, as two separate commands, specifying --drill on one of them, and --back on the other, then the offsets will be different and the drill holes won't line up.
If you run pcb2gcode and specify both --drill and --back to the same command, then the offsets WILL line up and you can just engrave, change bit and drill with no messing about.

Another possibility is use a board outline and use back and outline, and drill and out line if you just want to regenerate only drill or only back.
I THINK it takes its origin from the smallest x-y it finds, so if you use an outline together, it will find the same corner each time. If you do drill by itself, it will use the hole find the origin, not the edge of the track.

I stopped buying Dell computers a long time ago. I always buy HP, have and have had several laptops and desktops and I am very happy with them. Just be careful when you buy one, don't buy any PC with Windows 10 Home S version.
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