Nozzle gouge on heatbed - what other damage? And what happened?

Bambu Lab A Series Troubleshooting
1

Yesterday, through tiredness/stupidity, I managed to get a long gouge across my heatbed (and damaged the nozzle in the process). I’m new to the hobby, and this one is undoubtedly on me - but I want to understand why what happened, happened, and whether there may have been other damage I haven’t noticed yet.)

Bambu A1 plus AMS Lite. I’ve been printing stuff now successfully for about 3 months. Yesterday evening I did something stupid - stopped a print from the control panel, but somehow left the confirmation prompt up without replying to it, leaving the printer somewhat hanging. Then removed the heat plate to go wash it.

I thought the printer was safely stopped; the printer clearly disagreed. When I returned, there was a diagonal gouge across the bare heatbed, and the toolhead was sitting next to the purge wiper. Judging by the direction of the gouge, I must have walked away with it stopped in the middle at back.

I tried a new print, got horrible results and decided that the nozzle was likely also damaged (unsurprising). I replaced it with a spare and the machine SEEMS to be printing OK. If anyone is able to help advise a newcomer, though, I have multiple questions.

First, possible fallout. Enough force was going through the nozzle to gouge the hotbed. The same force would have been going through the toolhead and connected parts. Are there other less obvious forms of damage that might likely have happened, and how might they show up?

Second - understanding my printer. What happened? Clearly the printer decided that it needed to do something - but what? Any insights appreciated.

2

I can’t tell you for sure what the printer decided to do while it was hanging on that prompt, but on the fallout question: after a hit hard enough to gouge the bed, the thing I’d check is whether the hotend is still sitting tight in the toolhead.

On my A1 Mini (thousands of hours on it) I had a first layer that suddenly went bad and stayed bad through new filament, a new nozzle and recalibrating. What fixed it was mechanical: I took the hotend off (3 screws), tightened the 4 bolts at the back of it, put it back and ran the full calibration again. First layer was back to normal straight after. The A1 uses the same style of toolhead, and a crash puts exactly that kind of load on it.

So the symptom to watch for is a first layer that looks different from one side of the plate to the other, or one that a recalibration doesn’t fix. If that shows up, check those bolts before you start changing slicer settings. And since you swapped the nozzle, it’s worth running the full calibration from the printer menu once rather than just starting prints.

3

I’d also inspect that heatbed very carefully. Without the print plate on there, that gouge might be into the heating element if deep enough. If you can see metal you might want to get a new heater. Those heaters run at your mains voltage and might be a shock hazard.

That heat bed is a sandwich with the bed frame, the heater, and the magnetic sheet. The magnetic sheet probably protects the heating element but I don’t know the actual order or if there are other protects in there too. The Bambu wiki probably has instructions on replacing the heater element and if so, that could tell you if there is anything to worry about.

Got to say this may be all for nothing but you should verify that.

4

Thanks. Yes, I had the hot end seating in mind; I haven’t had time spare to check it yet, but I took a look at that anchor point once before when I was troubleshooting something or other, so I know the bolts you’re talking about. And I’ll ruin a recalibration ((edit: or maybe even run one, but the way I’m going, who knows? :grin:)). Much appreciated.

5

That’s an excellent point, and something I hadn’t though of.

OK - on close inspection it’s not actually as deep as my first impression - visually alarming, but wide and smooth, more than deep (just about deep enough to get below the irregularities in the heatbed surface milling, and leave an edge on the mark that can be felt with a light finger rubbing over it, but very little more). Scrape more than gouge. I’ve tried taking an impression of it, and with the assistance of thin paper and my calipers I’d say it’s in the area of 0.05 to 0.1 mm deep at the points where I can feel it. So I’ll certainly treat it with respect, and consider replacing it if I have any concerns, but I think I’m OK on that score.

But thanks VERY much for the highly relevant pointer. I’d never stopped to even consider how the heatbed works.

6

OK, so I’d tried a small number of prints since writing the above, and I noticed I was getting consistent first layer issues with the first few mm of print. Checked the hotend coupling plate, and, yes, all three front screws were a little loose, and one in particular of the rear screws needed tightening (the top one that the most force from the dragging across the plate would have likely gone through). Ran a recalibrate, and whilst it’s very early days, a quick Benchy print just now came out beautifully. So - I’m hopeful. Many thanks for the advice.

7

I used to experience nozzle dragging across build plates on bedslinger type machines — and even more alarming stuff like the printer head entering a violent jackhammer loop pounding the nozzle into the build plate with huge force.

This never seems to happen with core XY machines for me at least.

I entered your situation into Google AI and it returned excellent insights:

“Removing the build plate entirely while the machine is on or moving is the exact trigger for this specific disaster.

What happened to your friend is a direct consequence of how the Bambu Lab A1 tracks its physical position, combined with a crucial user error during the termination sequence.

What Triggered the Crash?

When a print job is terminated, the printer doesn’t just instantly freeze in place forever. The machine executes a mandatory “End G-Code” sequence. This script tells the toolhead to clean the nozzle, move the Z-axis, and return to its physical home position to safely park.

By ripping the magnetic build plate off the machine while the printer was actively trying to execute this automated parking sequence, the user broke the printer’s safety loops in two ways:

  1. Lost Z-Height Calibration: The Bambu Lab A1 measures its Z-offset by physically tapping the nozzle onto the build plate. Without the plate, the metal surface sits roughly 1mm to 2mm lower than the digital brain expects.
  2. Missing Sensor Baseline: When the toolhead moved to its home corner to park, it descended to search for the bed. Because the plate wasn’t there, the nozzle plunged past the digital “zero” line. The strain sensor failed to register a tap at the correct height, and the stepper motor kept driving the nozzle downward, dragging it sideways right across the bare magnetic heat bed sticker. [1]

Damage Assessment & Next Steps

Your friend needs to check for two types of damage immediately:

1. The Magnetic Heat Bed Sticker

  • Cosmetic vs. Structural: If the nozzle only left a silver scratch or a minor indent on the black magnetic sheet, the bed is still perfectly usable. They can just put the steel PEI plate back on top and keep printing.
  • Severe Gouges: If the nozzle physically tore, gouged, or plowed up a raised ridge of rubber/magnet material, the steel plate will no longer sit perfectly flat. A warped plate causes automatic bed leveling to fail. If the surface is uneven, they will need to purchase a replacement Bambu Lab A1 Heatbed Unit. [1]

2. The Toolhead Assembly (Hidden Damage)

A severe mechanical crash against the solid bed frame almost always bends components. Before printing again, they must check: [1]

  • The Nozzle: The quick-swap nozzle tip is likely bent or blunted from the friction against the bed. Tell them to swap in their spare nozzle immediately.
  • The Heater Screws: The massive force of the crash likely loosened the four small screws holding the internal heating block assembly. They must remove the front toolhead faceplate and tighten these screws, or the printer will continue to scrape future prints.
  • Full Calibration: Once everything is tightened and a new nozzle is installed, they must run a Full System Calibration from the A1 touchscreen menu before starting a new print. [1, 2, 3]

The Golden Rule for the A1: Never touch, remove, or clean the build plate until the toolhead has completely stopped moving, the screen reads “0% / Ready,” and the cooling fans turn off.

Did the nozzle tear through the black magnetic sticker, or is it just a superficial scratch? Let me know if they need help figuring out how to check the internal toolhead screws for damage!”

You can cut and paste the discussion above into Google A.I. and continue conversing with it on your situation and concerns, and I am certain it will help you immensely! Be well!

8

Great to hear, and thanks for coming back to report it. The top rear screw being the loosest makes sense, given that’s where the drag across the plate would have pulled hardest. Glad the Benchy came out clean — hope the next prints stay that way.

9

Before you decide that the only solution is a replacement, get a flat, fine cut, file. Remove the handle, so that it can lay down completely flat on the bed. Now you can smooth the high spots pretty easily by moving the file sideways across the bed. Wipe away the resulting swarf regularly with a damp cloth.

If this works correctly you’ve spent a few minutes and saved money. If not, then all you’ve lost is a few minutes.

BTW, I had to tramm my bed twice in the first month: A1 Bed Tramming | Bambu Lab Wiki. It looks like that might have been due to initial settling of the machine, because it’s been fine ever since.

10

Thanks for that. Yes, my bed definitely needs tramming too (probably after my blunder); I’ve a plate-independent low-adhesion zone at back left that I’m pretty sure is new, which again matches quite closely to where the nozzle and bed made contact. And a steel rule edge across the plate shows the heat bed low at that point. I’ll take another look, though, in the light of your post; I didn’t consider the possibility of the bed surface being raised around the scratch as well.

(I haven’t gotten around to tramming it yet, because mostly it’s not causing me issues with the sort of things I’m printing, but I will. And, yes, I’ve been somewhat putting it off… never done one; first printer… And I have a lifetime’s experience of too often getting DIY and similar stuff right at the second attempt…:laughing: So every new bit of maintenance, however simple, is slightly nerve-wracking and something to be faced only when I’m feeling wide awake!)

11

Sigh. Yup. Front heatbed locking screw was so tight that the hex has stripped, and so far I haven’t been able to get it loose. Managed to tram the back of the bed, but the front is now something of a disaster area. Ah well.

12

(Just for completeness - I cut a slot across the seized screw with a dremel-style tool, released the screw with a flat-bladed driver, trammed the bed, ran a complete calibrate, rebooted and things are more or less back to normal. A couple of minor first-layer issues, but I don’t think they’re specifically bed-related)