PCB-Gcode - ground plane with 1 pass per path

[Tester]

I'm using Eagle + PCB-Gcode and I'm trying to create a ground plane where CNC would make only 1 pass for every path that needs to be separated from the plane. So in 1 pass it would actually create the path itself and separate it from the ground plane at the same time. Is this possible?
Currently I'm experimenting with DRC settings for clearance but I'm always getting 2 passes per path which is double work for my fairly slow CNC . If clearance is set too low the path doesn't get cut at all.

Thanks in advance for your suggestions and tips.

[Jay C]

What are your setup values in PCB-GCode? How big is your tool diameter, what is the max isolation you set?

Jay

[epineh]

I did this today and I was getting three or four passes, as you say it takes time.

I managed to get it to work by putting 0.2mm in all three boxes (default, maximum, step size) in the board section of the generation options tab. I don't know if this is the correct method but it got me going. You could change the value to suit you cutter/isolation distance.

I also left the generate milling box unchecked.

Cheers.

Russell.

[Jay C]

The milling box is only is you want it to generate a mill file to cut out your board. It has no affect on the isolation or number of paths that the system generates based on your tool size divided by maximum isolation value.

http://www.millpcbs.com/index.php?page=pcb-gcode-setup

[Tester]

What are your setup values in PCB-GCode? How big is your tool diameter, what is the max isolation you set?

Jay

Here is one of my standard settings:
Isolation default = 0.1 mm, maximum 0.1 mm, step size = 0.1 mm (0.1 mm ~ 0.004 inch)
Tool diameter: 0.2 mm (~ 0.008 inch)

In Eagle I set clearance for wire-wire to 25 mil, and for the pad-wire to 16 mil

@epineh
What tool diameter did you use? I tried with 0.2 mm in all three boxes but couldn't get the right results.

[Tester]

I just realized that perhaps I wasn't clear enough in my first post and that there is a small misunderstanding.

I attached some screenshots to this post that will hopefully clarify my question. First two pictures are screenshots of the same board from Eagle where the first one has the ground plane but the second one doesn't.
Second pair of screenshots shows the gcode view of these two boards. It's quite clear that on the board with the ground plane some paths have two passes and some have just one (remarkably a lot of paths in this particular example have just one pass, usually all of them have at least 2 passes), as opposed to the standard board where all paths are milled with one pass.

So my question is: how to set Eagle and PCB-Gcode where all the paths (on a board WITH the ground plane) would be milled in one pass.

I hope that "the story of one pass" is a bit more clear now.

[Jay C]

I see no problem. One pass is for the trace, the other for the pour. PCB-Gcode takes the output geometries from Eagle and draws a line to the outside of them. The pour is one geometry, the signal path is another.

[epineh]

Ah I see what you mean, I had two passes as you show it, I thought you meant more passes to make a larger gap between, which is what I started with, and it took a long time. I only got it down to the two, as Jay C mentions the passes are for different area's.

I guess if you make it without the ground plane then you will have to manually bridge the ground tracks to the rest of the pour, which isn't ideal. I will ask a friend and see if he knows.

I was using a 60 deg V cutter btw

Cheers.

Russell.

[Tester]

Hm yes, you're probably right. Double passes in this examples are used to separate ground plane from areas that don't use it (signals in these areas are not connected to GND). But if I'm not mistaken they are also redundant and the board would work just fine without them.

[Jay C]

Correct. Are you clever enough to find where this is the case and remove them? Keep in mind, you are going to be processing an array of lines from Eagle in the order they were drawn. However, did you run your output through the optimizer I helped write to get rid of a lot of wasted air time? Most of my files end up with 80% optimization.

FWIW,
Jay