Bed levelling causes this damage to the PEI sheet
 
Notifications
Clear all

Bed levelling causes this damage to the PEI sheet  

  RSS
tdk408
(@tdk408)
Estimable Member
Bed levelling causes this damage to the PEI sheet

Before printing, the printer nozzle pecks at the PEI spring steel sheet a dozen times. Each place is now damaged. It seems the hot nozzle is damaging the PEI in those specific places. Each mark is a donut the dimensions of the nozzle tip. In the photo, the white material in the row of marks is the PEI coming off.

I understood that a load cell was supposed to stop the vertical motion when the nozzle touches the bed.  But then why this?

Prusa support wants me to check the nozzle position, the firmware and the spool position. I don't see how any of these could cause this damage, particularly if the load cell is working.

Any ideas?

This topic was modified 3 weeks ago by tdk408
Posted : 16/01/2025 8:33 pm
ManelTo
(@manelto)
Estimable Member
RE: Bed levelling causes this damage to the PEI sheet

The same thing happened to me last week. I had to remove the nozzle and reattach it and it started working properly again. But the PEI is damaged. 😥 

Sorry for my poor English. I try to do my best.

Posted : 16/01/2025 8:57 pm
JP Guitars
(@jp-guitars)
Reputable Member
RE: Bed levelling causes this damage to the PEI sheet

I can see that happening if the nozzle is loose as it will continue pressing until the slack is taken up but cannot see how the firmware or spool position would make a difference.  My gut reaction though, is a faulty/mis-calibrated load cell.

Posted : 16/01/2025 9:07 pm
tdk408
(@tdk408)
Estimable Member
Topic starter answered:
RE: Bed levelling causes this damage to the PEI sheet

I don't understand. If the load cell works, it doesn't matter if the nozzle is loose. 

Lets say there is 10mm of play. the z axis will continue to descend until the slack is taken up. At this point, the load cell still triggers once the nozzle touches. Even so, no damage.

Am I not seeing this right?

Posted : 18/01/2025 1:58 am
Mike B
(@mike-b-3)
Trusted Member
RE:

When you start printing, the nozzle will be 0.2 mm (whatever your layer height is) too low (i.e. touching the bed instead of one layer above it) but going horizontal instead of vertical.  Dragging the hot nozzle across the plate will cause damage.

Prusa MK4 since Jan 2024, Printables: @MikeB_1505898

Posted : 19/01/2025 10:02 pm
tdk408
(@tdk408)
Estimable Member
Topic starter answered:
Damage caused by bed calibration
Posted by: @mike-b-3

ragging the hot nozzle across the plate will cause damage.

I didn't know that, Mike. Thanks. But it doesn't address my concern.

I am describing a grid of spots which are clearly evident on prints. (See the attached image.)

This damage in exactly the places where the nozzle touches during the calibration process. When I put the sheet under my microscope, I see the PEI coating has been mashed away in the clear shape of the tip of a 0.6mm nozzle.

Check your smooth sheet and tell me if I am alone.

Cheers, Tom

Posted : 24/01/2025 3:48 pm
Mike B
(@mike-b-3)
Trusted Member
RE: Bed levelling causes this damage to the PEI sheet

 

Posted by: @tdk408
Posted by: @mike-b-3

ragging the hot nozzle across the plate will cause damage.

I didn't know that, Mike. Thanks. But it doesn't address my concern.

I am describing a grid of spots which are clearly evident on prints. (See the attached image.)

This damage in exactly the places where the nozzle touches during the calibration process. When I put the sheet under my microscope, I see the PEI coating has been mashed away in the clear shape of the tip of a 0.6mm nozzle.

Check your smooth sheet and tell me if I am alone.

Cheers, Tom

Unfortunately I rarely use the smooth sheet - I've been using the satin sheet almost exclusively for PLA, PETG, and PC.  My PEI sheet has no marks like this but it could be something that develops over time...

Does it seem like the nozzle is being pushed too hard into the bed during the levelling process?  Perhaps the calibration of the load cell is to blame - putting too much pressure on it?  Just trying to come up with some ideas...

Prusa MK4 since Jan 2024, Printables: @MikeB_1505898

Posted : 25/01/2025 7:12 am
Share: