H2C: Scratching Noise and Black Rubber Dust on Rear Left Pulley

Bambu Lab H2 Series Bambu Lab H2C
1

Hello everyone, I am experiencing a recurring issue with my BambuLab H2C related to the rear left pulley and would like to ask if others have seen similar behavior.

Issue description: During printing, scratching / rubbing noises occur

  • The rear left pulley quickly accumulates a black residue / rubber dust
  • The dust appears to be belt material
  • After cleaning the pulley with a Q-tip and isopropyl alcohol, the noise disappears completely
  • After a short period of use, the black residue builds up again and the noise returns
  • Only the rear left pulley is affected

Additional information:

  • Pulley cleaning was performed strictly according to BambuLab’s official maintenance guidelines
  • Print quality is still excellent As long as the pulley is clean, the printer operates quietly
  • Based on this behavior, I suspect a possible pulley misalignment, pulley surface defect, or bearing issue causing belt abrasion. Unfortunately, I don’t have a current photo of the black dust, but the appearance matches well-known images from similar cases shared on Reddit.

Questions to the community: Has anyone experienced the same issue? Was the pulley or belt replaced in your case? Is this a known issue or related to a specific batch?
Thanks in advance for your feedback and insights!

2

Change the angle of the tensioner so that the belt runs in the middle of the pulley. There is a video on youtube with this problem on a P2S.

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3

I checked them and they seem all aligned. It is still making noises, but i will upload a video.

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6

This is pretty normal. I had this on every single CoreXY from Bambu.

Do a belt tension adjustment and move the belt with a finger in center position on the motor gear. Tight the 4 tension screws again.

The black rubber dust is just from the cutting edge of the belt, absolutly normal and this causes no wear to your belt. Align and center your belts on the black motor gear and all is good. Due the closed backpart, its not possible to align the angle of that belt-tension portion, so you correct this angle by aligning the belt inside of the printing chamber with your finger (needs a little force and move the toolhead in power off mode to do this). No worries, your printer is absolutly fine!

7

Its easy to remove the back cover to get access to the tensioner.

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8

I would prefer the simple way first. That works anyway

9

Yes, you are right , i just wanted to show that its easy with the rear panel. I had this problem on my H2S and solved it with a new adjustment from the tensioner

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Yes, this is a very common problem. I had this time to time on my X1C and H2D. The good news, it can be fixed within 5 minutes. The sound comes from the belt edge rubbing on the pulleys inner corner and oh wonder, this rubbing produces the fine black particels underneith this area

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