Weird toolpath circles wherever the z axis changes

The toolpath is making these weird circles that seem to correspond to wherever the tool path has to lift up. I generated this gcode in Fusion360. The cmd I’m running Ground Control out of just has the message “G18 not supported” on repeat. The toolpath looks great in Fusion360, so I’m very confused. Anyone dealt with something like this before?

Are you using helical ramps in Fusion?

Did you try using the maslow or grbl post processor? If not, you might try each of those and see if that changes the view in groundcontrol. The G18 command if unsupported will not be included in the GRBL or the maslow post processor. It looks like your drawing needs the smaller side of the circle segment and ground control is drawing the larger portion instead.

I don’t think so. Is that a 2D contours option?

I don’t think it’s Fusion because as you can see the tool path looks pretty normal on F360. I’ve tried GroundControl on my Ubuntu machine and my Windows machine and I’m having the same issue.

This was exactly it. Thank you very much.

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No, I don’t think it is an option for contours. I admit that I did not look hard enough at the screen shot to tell that it was only contours. It was pretty busy with all the arcs.

Looking at your second image, it looks like you have a ton of tabs. That’s going to make for a long program and a lot of cleanup. On larger pieces, I’ve been able to get away with a tab every 6 inches, but sometimes a corner or curve interrupts the spacing so I have to put them closer or place them manually. Just trying to save you some frustration.

Thank you for the advice!

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I did. Changed it from 50mm to 200mm spacing and it turned out great. Thank you for saving me a lot of trouble!


No problem. How’d the pieces turn out?

Beautifully, except the ones I cut near the edges. There were some problems- one of my cuts near the bottom right edge tipped off, a cut near the bottom left was really inaccurate, and the z-axis kept slipping out of position.

To remedy these I’ve already ordered the upgraded zaxis (I know there are cheaper diy methods but I just wanted something that worked), I’m gonna build a frame around the cutting surface for the sled to glide on, and… not sure what to do about the inaccuracy near the edges… recalibrate? For now my plan is to do a bunch of test cuts to see where the accuracy breaks down and then just… not cut there lol

cutting near the top, bottom or sides usually causes some degree of inaccuracy . and if you need to cut near the edges a piece of offcut the same thickness added to the area to support the sled helps stop it tipping .

to fix the lower corner inaccuracies, the best thing you can do is get a 12’ beam and lift the beam to 30" from the workpiece, which will require chain extensions and recalibration. otherwise you would be best to confine your cuts to the inner 6’ of the system.