Homing Error (GRBL ERROR 9)

Hey gents -
I’ve successfully run two projects and today when I turned the machine on and went through the homing operation, the router just vibrates along ‘z’ axis. I’ve turned the machine off, disconnected from power and restarted but get the same issue.

Thanks in advance.

Hey Mike,
Your Z switch isn’t being registered. What you’re hearing/seeing is the Z stepper skipping as it keeps trying to raise.
Can you check your switch and the connection at the board?


We have an official page on troubleshooting the homing switches here:

As @neilferreri noted, Grbl error 9 is:

9 G-code lock G-code commands are locked out during alarm or jog state.

It might be that the machine is starting up on a switch, or a switch is (hopefully temporarily) stuck closed, or faulty. Let us know what you find out and if you need anything, contact us at support@carbide3d.com

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Thanks guys. Neil, you were spot on.

I learned that the stop wasn’t being activated on the Z-axis. Upon closer inspection, I noticed the left top wheel was loose which made the whole router back plate lean forward slightly - enough that the micro-switch wouldn’t make contact. After some disassembly, tightening and reassembly, she’s working again.

On a side note, after running a simple sign job for my daughter, Motion stopped at 73% and would not move. I had to close the program, re-open and try to re-centre my bit / run the job again. I was close but there’s a slight ‘step’ I had to chisel out.

In future:

  1. Any idea why CM would just stop?
  2. Is there a way to get back to the exact coordinates if a job has to be repeated?


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1 - the community has some notes on CM stopping at: https://www.shapeoko.com/wiki/index.php/Electronics#Recommendations

2 - re-homing should be quite precise / accurate if you use homing switches, so long as nothing was changed / adjusted. It may be though that the belts and belt anchors are settling in — some users have reported that.

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As @WillAdams said, when you home you should be able to get back to the exact same spot. No need to re-zero.

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Neil -
Does this apply to jogging to the same start position on a project? I should have been more clear as that is what I’m referring to.

I.e. - job stops; shutdown / restart programs; try to resume (redo) project from the exact same start point.

I depends on how work zero is set. It’s been a while since I used Carbide Motion, so I can’t say for sure how it’s done there. Assuming it’s set with a G10 L20, your work zero will persist across resets and power cycles. You can just home and start the carve.

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So, as has been said, you can just restart everything (the pc, restart the sender, the whole deal - the GRBL keeps the zero you already set. DON’T MOVE THE PART, but after homing, everything should be fine. Just reload and go.

Resuming from the exact point is harder, but you can also just restart the job, it’ll “air cut” up to the point you were at, but that just absorbs time, for the most part. If you’re really driven to skip it, you will see a “header” at the top of the gcode that’s different than the rest. Keep that. It has all the setup for the job. You can usually then read through the gcode to about the point you were at, with a little experience, and clip out a big chunk of it. I really wounldn’t recommend trying this hte first time on something you care about.

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