Strange toolpath taken at end of cut

I spent several hours cutting parts for a speaker cabinet today with my Shapeoko 3 xl and all went well except for the final cut. The machine took a strange path at the end of its cut. It cut this strange path outside of the piece of plywood it was cutting. I highlighted the strange path with the red and blue arrow and you cab see the path it took by the cut it took into the white surface of my new waste board. The depth it took was accurate but it was not suppose to do that cut! It broke through the edge of the plywood and pushed over a black aluminum work holder to complete this path!

When all was done i wanted to see what happened to my x y location and so I had carbide motion move the machine to its current XY and it went to the machines extreme bottom left location and made a noise like it wanted to push further but it had reached the limit of its travel space and couldn’t go further. So somehow the XY got changed too.
What could have caused this?
I uploaded my carbide creates file used to complete this cut.

BlockingScaled.c2d (52 KB)

This almost always happens because during the cut, you lost steps. Things to check:

  • Belts, tightness and look for failed (stretched out) portions.
  • Pulleys. Make sure the grub screws on the stepper pulleys are tight.
  • Work-holding. Some part of the gantry / spindle / dust collection may have run into work-holding, and thrown things off.

If you want to investigate more, you could try an ‘air job’. Set up your material as before, and re-run the job, EXCEPT

  • remove the bit after setting your Z Zero.
  • turn off the router.
    If you have a bitsetter, disable that too.

You can speed things up in CM to go faster. If you run into something, you should be able to hear it.

1 Like

Thank for the quick reply Michael! I actually let this job run unattended I had spent several hours with the machine today and my ears needed a break LOL.

Its funny you mentioned the dust collection since my swiftly got lossened and slightly cut into by my endmill. I am using a new vacuum as well and the hose may have been not able to reach as easily while the router moved.

I will do a an air job tomorrow


I agree with @mhotchin . You lost steps. i have a Shapeoko 3XXL with HDZ and I have had the drag chain fall off the back before and cause this. Vacuum hoses and dust collection boot can also get hung up and the machine loses steps. So address what Michael suggested and get your dust collection straightened out. There are always start up issues that have to be addressed.

Hi Guy! Yes funny you mentioned the drag chain in the back. It gets stuck for me a lot. It slips off the black clip in the back of the machine and then the chain gets stuck and the machine wont move and I need to shut down in the middle of a job. I need to make that clip wider so the chain doesn’t slip off.


Here’s how I fixed the drag chain getting stuck in the mounts:

Still have some, happy to send a set of you DM me and cover the shipping.

Thanks Dan! I sent you a DM


Here is the fix on my SO3 for the drag chain falling off. I had been using double sided tape for a board but eventually it would fall off. So I had some angle iron in the shop so I cut it to size and drilled some holes. I marked the gantry and drilled and taped them for some machine screws. I left the glued board on until it falls off. If you look closely at the right of the angle iron you can see remnants of former taping jobs.

Thanks for the info and the images Guy. This is very helpful!