Gantry moving unevenly

Hey guys! Just received and setup. We noticed the right side is outrunning the left side in start up and starts to derail. Appreciate any help!

Welcome to the forum.
Check the rails and belts for debris. With the machine off, slide the carriage arm forward and back. Do you feel any resistance?


Thanks for the reply! We squared it and tightened the belt. Still feeling a slight resistance on the left side. Every time it runs, the right side outruns the left. I printed a square and the left side printed uneven.

Seems to me you should not have to adjust any belt tension with a newly delivered machine.

I suggest you remove the honeycomb tray, open the front door and inspect the machine closely as you move the arm forward and back and the printhead left to right. Can you see anything that the arm could be “catching” on? Any wire hanging down?


We’ve inspected the rails numerous times and there’s nothing there. Can’t see anything that would catch.

When the machine turns on and the gantry and laser move towards the center, the right side always moves further forward. The machine seems to adjust, but once it goes back to the start position, the left side catches and there’s a loud noise and the gantry stops lopsided.

Check if the tension on the left and right side belts are the same. If one is too loose or too tight, that may explain it getting pulled to one side and getting stuck on the other when the motors try to move things.

There’s a guide and a little animated GIF here showing how tight each belt should be:


We have read and performed all troubleshooting problems concerned with the belt tension and squaring.

I know staff is probably overwhelmed, but I’m going close to 3 days with no response now. Not sure where to go from here.

Hello @mark.a.robison.jr First and foremost I humbly apologize for the long delay. I will do my best to get this issue resolved for you. Could you please confirm the serial number of the printer having the issue for me? The serial number can be found on the back of the Glowforge, printed on a sticker near the AC adapter on the right-hand side. It will look something like ABC-123-4.

Once I have the serial number I will be able to get a better look at the trouble you are seeing with the laser arm. I also have a few steps for you to try to get the Laser Arm back on just in case you haven’t tried these steps:

Could you please do the following for me?

  1. Turn off your Glowforge
  2. Try gently sliding the laser arm towards you a bit, perhaps moving one side, then the other. Whether or not that works, continue to the next step.
  3. Placing one hand in front and one in back, gently lift up the laser arm on the right side, near where it shows that it’s off the track. Make sure your hands grip the metal bar, not the tube itself.
  4. While lifting upwards, roll the the gantry towards you, then farther away a few times. Your goal is to straighten it out, so that it’s parallel to the front door. It will pop back onto the track where it belongs.
  5. Once it’s on the track, place one hand on each side of the laser arm (left and right now, rather than front and back) and roll it to the center of your Glowforge. Then roll it back about three inches, forward to center and then 3 more inches towards you, and then do that a few more times.
  6. Move the Printer Head to the approximate center of the laser arm.
  7. Turn your Glowforge back on and continue printing.

Would you let us know how it goes?

Thank you for your response.

Serial number: KFT-842-4

The arm slides smoothly once on the track. No bumps or kinks when moved manually.

*it rolls smoothly when turned off and manually pushed

I turned it back on and it did the same thing

In your original post, you said the right side outran the left. This looks like the left moved and the right didn’t? Is that correct.

From facing the machine, the right side is racing to the back while the left side is moving slow and lagging behind, which makes it come off the track. The left side also prints abnormally, I’ll post my calibration. On startup, it also lags and is never straight.

This picture is when it was in the middle going backward, not coming forward

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I’m thinking bad stepper motor?

Still no response back from staff on this??

Hi @mark.a.robison.jr I apologize for this delayed response. I am reaching out in this thread to confirm that you have received my email sent earlier. It appears that this is an issue that will most likely need to have the printer replaced. Since this can require confirmation of your private information, I wanted to keep this thread open to make sure my email has been received. I’ll look forward to your response. Thank you!

Received and replying. Thank you!

Thank you! I just followed up with you through the email ticket, and I’ll go ahead and close this thread now.