Entire laser head horizontal arm is 'bucking' or skipping

Try a different material with same settings. If it works fine, then it’s the material your using.
If it still has the issue, the try slower speed with higher power. If it’s still and issue, then it’s the machine itself and not material or settings.
Process of elimination.


Might also want to check the tension on the belt underneath the laser arm…might as well check all 3 while you’re at it.

Yeah it’s not the material. Tried oil board for a stencil and same problem. Lower speeds still have that bucking or clunking sound and are bumping the machine enough that I can feel it. Are the two wheels on the right rails supposed to be loose? If I pick up the arm a millimeter, I can wiggle the wheels left and right about an 1/8”. Both. Left side is tight.

If anyone can open their GF and wiggle the whole arm/tube/head thing just a little bit, like you’re moving bicycle handle bars, I’d like to know if yours is loose too.

No. Mine has no play in it whatsoever, before the belts themselves move on the motors/idler.

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That’s what I was afraid of. The entire arm seems loose to me. Like bicycle handle bars that I can turn right or left just a little bit. Doesn’t take much pressure.

Maybe that is causing the whole thing to bind a little bit at a time and the whole arm twists.

When it happens, my design gets cut but with a new angle, like the image has rotated clockwise a couple degrees each time. With three passes, it’s ruined.

In my opinion, it has to be mechanical.

I have done some really intricate cuts at full speed (on paper), the machine keeps up with it just fine.

Each moving part has a plate that the wheels mount on (one on each side for the gantry, and the carriage plate for the head). Grab them securely and see if you can get any play in the belts that they are attached to. Also try moving the gantry in relation to each side plate - hold each one securely against the side rail, and try wiggling the gantry to see if there’s any play there.

I get the most play in the whole arm, it can move like bicycle handlebars turning left/right. Not much, but seems wrong. Pulleys have been removed and tightened. Belts seem fine tension wise. The two top track wheels on the right of the arm can move side to side on their bolt. Shouldn’t they be tight but free spinning?

Yes. There should be no play in any of the wheels or between them and plates they attach to, or the gantry.

Oh no! I’m so sorry you’ve hit a snag. Would it be possible to get some photos of the prints experiencing bucking or skipping you’ve described?

Additionally, I’d like you to perform a standardized print for us to review. Seeing the print results will allow us to suggest the best next steps. At your earliest convenience, please perform the following:

  • Print the Gift of Good Measure on Proofgrade material, using Proofgrade settings.

  • When the print finishes, leave the lid closed and wait until the fans stop and the picture updates.

  • Send us a photo of the finished print

hey Jeremyh,
thanks! But I think I’ve figured out the issue. I know troubleshooting always starts at step one, but I’m beyond that and in a hurry. Can you tell me if the small plastic wheels attached to the arm and that run on the top of the side rails should have any play in them? The screws that hold them in are tight BUT the wheels can move in and out on the bolt/shaft that they spin on. Are there bearings in there that could go bad?

Interesting…I started having the exact same problem yesterday. Could be coincidence, but then again if the left and right belts are controlled independently, it could be software.

Myself, I was blaming the belts, but I will try to check their tension.


Check my previous post. Same problem you have???

Hi @TypicalAdamo! Thank you for the reply. My apologies about the delay in getting back to you. Typically the wheels on the laser arm are not a source of trouble unless one is cracked or visibly damaged. Based on your description, that seems unlikely to be the source of the issue here. I’ll need some more information before I can advise about the next steps.

Could you please tell me more about the trouble you’ve been experiencing? If possible, please post a short video of what you are seeing.

Could you please also let me know, have you had any prints that didn’t turn out as expected?

So can anyone with a working GF tell me if their laser head arm can wiggle on the tracks? Meaning, can the left side or right side move independently up or down the track even just a little?

I believe this might be my problem. My laser head arm has too much play, like a bicycle handlebar that turns right and left just a little bit.

This topic seems really close to my problem. Thumping sound, possible belt or pulley issue. But my belts aren’t loose or damaged.

I addressed this a week ago, above.

There is no play at all in my gantry. You can only lift it if you overcome the spring tension on the lower wheels, just like with the rear wheels on the carriage plate. Otherwise, it is solid.

It doesn’t take much pressure to rock each side forwards and backwards with the power off, so it can be easily “twisted”, but the belts and stepper motors move in unison and when powered on, it is held solid (unless commanded to move, of course.) There is no play at all there.

In case you didn’t notice, a support team member (@chelsea) asked you for some information above. The sooner you reply to her the sooner they can troubleshoot your issue for you and find the cause. :slight_smile:

Since it’s been a while since we’ve heard from you, I’m going to close this post.

If you are still having trouble, please start a new post with the information I requested above or email it to us at support@glowforge.com and we’ll continue to investigate.