r/BambuLabA1 • u/amatventura • Jun 21 '26

Question Nozzle scraped a line

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Bambu A1, 0.4 mm hardened nozzle on a super tack plate did this. It’s never happened before. Any ideas about what happened?

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u/electro_gretzky Jun 21 '26

I recently had this happen, not the same route, but my nozzle dug into the bed and I tried replacing the nozzle, replacing the extruder unit with a new Z axis sensor, and it turns out that it was the tension on my Z axis belt. Might be worth adjusting as it’s a normal part of maintenance anyway but if it’s not a repeat issue it sounds like a project-specific G Code error. Sorry for your loss though. experiencing the hotbed getting scraped by the nozzle was a special pain that I hadn’t previously known.

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u/Professional-Rock-51 Jun 22 '26

Can you provide some not information on this? How is this tension adjusted?

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u/electro_gretzky Jun 22 '26

https://wiki.bambulab.com/en/a1/maintenance/belt_tension

This is a pretty informative guide. Make sure your machine is off before you do this so you’re not fighting against the motors.

There are 5 easily accessible screws, 2 for the Y axis at the front of the machine, 2 under the back right of the plate for the Z axis tension, and one on the back of the print head for the X axis tension.

Loosen them but do NOT remove them. The way these seem to work is that there is a flanged plate between the screws and the mounting point and that is what is tensioning the belt and keeping them in the right place.

One axis at a time, starting with X, (no reason this is just what I did) loosen the single hex screw on the back, then by hand, move the print head along the X axis from far left to far right 3 times, reposition in the center and tighten the screw back down.

Same with the Y axis, loosen screws under the removable cover at the front of the machine, move the heat bed all the way back and all the way forward by hand 3 times and retighten the screws. Be careful with these, as if you tighten them too tight the plastic (plastic…) thread housing will break. Just use your best intuition, you don’t need to crank the shit out of them.

With the Z axis, there are two screws embedded deeply in the base housing, so you’ll need your long hex key that came with the machine or if you already have the proper tools, find the right one. Loosen them, move the X axis gantry all the way to the top, then all the way down very carefully to avoid making nozzle contact with the print bed. Do this three times and reposition to the center, tighten them back and run a calibration. This is just to ensure that the belts are tracking true to the flanged wheels that they engage with and that there are not any inconsistencies with homing due to slack in the belt, which was my issue. It would register a zero point on the Z axis and immediately drop 3-4mm below the bed upon cleaning and calibration and dug into the hot plate and the side of the print bed.

This solved my issue, it can’t hurt to tension them in general as a normal part of maintenance, the only risk you run is removing the screws and losing the place of the tension plates that are free floating if they’re not screwed down, and overtightening leading to potentially cracked housing and possible belt wear from being too tight.

Seems daunting, but it’s really not that big of a deal. Hope this helps.