[Resolved] Problems on the Small CNC

Today I experienced two problems on the small CNC. I’m not sure if they are related but it seems likely.

About 7 minutes into a cut it just stopped. The Z axis retracted as if had executed the END command of my gcode but it wasn’t even close to done.

I wasn’t sure where it had left off so I just restarted it from the beginning. After 7 minutes it got to where it had left off and continued on just fine thus telling me that my gcode file was fine. I let it keep running it proceeded normally for another few minutes and then all of the sudden it retracted the z axis and continued cutting on a z plane that was way too high. I sanity checked my gcode and I can see that my gcode does not contain any strange z value nor any sort of odd G code instruction to reset z.

I stopped it and drove the axis around manually and saw that the z axis was now off by exactly the height of the puck. It was as if for no reason in the middle of a cut it had reset z by the height of the puck. Maybe that height was a coincidence but there was no command in my gcode that should have reset or moved the z origin.


I’ve run three short files (all under 5 minutes) without any issues. I don’t think I’ll be running anything that hits the seven minute mark. The controller asked if I wanted to resume the last job when I started it up, which I assume was your last job.

Just a guess but maybe when you set the z height with the puck you accidentally used the manual z height setting method…?

Thanks for the reply; I’m not sure I understand your idea however. Is there some failure mode where the Z changes in the middle of a run without human intervention that would have been caused by manual vs automatic z setting? The weird thing was how in the middle of the run the z just “lost its mind” and all of the sudden was moving the cutter around about an inch above the work.

Ah. Yes, if the z changed in the middle of the cut only then what I was thinking wouldn’t apply. As long as the material didn’t shift at all during the cut then I don’t know how the z-axis could have changed. I did notice, however, during one of my cuts on the iQ that the z-axis didn’t seem to be set appropriately. This was in spite of the fact I was pretty sure I set it correctly. In my case I saw the issue at the beginning of the cut so I didn’t have a shifting z-axis throughout the cut. I reset my z-axis and the problem resolved itself.

This probably isn’t the best advice but I’ve used the Swift machine and never had an issue with z-axis. Maybe try that one out.

The small cnc is operational again. One blown fuse has been replaced.