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First layer problems, no solution from support  

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Extrutim
(@extrutim)
Eminent Member
First layer problems, no solution from support

Hey,
I have a bed leveling problem with my Mini+ which has existed from the beginning and I am not satisfied with the support's proposed solution.

The problem is that the first layer is always too low on the left and too high on the right. This is not unusual, Prusa provides instructions on how to align the printer correctly. So I aligned the printer and when I move the extruder from right to left by hand or with the printer control, the distance from nozzle to bed is the same everywhere (checked with a feeler gauge).
However, the problem still exists. The Pinda probe thinks that the distance to the bed is greater on the left and therefore moves the Z-axis down. I have no idea why this is the case.

The solution from support is to set the X-axis at an angle so that the first layer is somehow good despite the Z-axis moving down. At this point I had already been writing to support for over 3 hours, taking videos and photos, and now I no longer wanted to deal with this issue.

I can't really explain where the problem comes from. Is the Pinda causing it? But why is this incorrect value constantly measured and only in the X axis? Of course I also rotated the print bed and the chat support had no solution except to alleviate the symptoms.
Of course, the printer was able to print, even if the first layer still had this problem. Anyway, I didn't have the time or the leisure to deal with it and as the printer is barely used and has only accumulated about 15 printing hours in the last year, I would now like to sell it to a friend. Before I do this I would like to find out if there is a decent solution to this problem.

Posted : 28/02/2024 3:34 pm
Eef
 Eef
(@eef)
Trusted Member
RE: First layer problems, no solution from support

Seems a tricky problem. I do not have a mini so do not exactly what it is capable of. I suppose the automatic Z calibration procedure is the same  on mini as on MK2.5 etc? 
If so then in first round of calibration, the pinda checks all magnets (turning around to find the best spot) and does to find all 9 magnets. 
In next round it measures height on 36 points and makes a kind of map of all points (in octoprint possible this as a kind of landscape. ) 
This is used to know the exact zero Z point all over the plate. You say the issue is only in X=direction.
In fact the nozzle is on a good height, but the software "thinks" it is not. 
- Thinking aloud: 
If this would be a firmware/software issue, then it would not fit that the problem is only on one side (the calibration procedure goes zig-zagging. If there would be an issue, you would likely see more random problems)
- Funny idea: "Of course I also rotated the print bed " If (since last Z-calibration) the bed + magnets was mounted turned 180 degrees. Then a very light angle between left and right will be also turned around giving the double angle. If so, then re-calibrating should solve this. 

No more ideas for now. In fact the more I think about it, if there is a mechanical issue, a new Z-calibration should solve this. 

I will follow the thread, very curious how this can be explained and solved. 

Regards, Eef 

Posted : 28/02/2024 3:50 pm
Extrutim
(@extrutim)
Eminent Member
Topic starter answered:
RE: First layer problems, no solution from support

The self-test on the Mini does not include the search for measuring points as on the i3. This could possibly solve this problem.

Posted : 28/02/2024 4:22 pm
Diem
 Diem
(@diem)
Illustrious Member

Your gantry is sagging. Either there is something loose in the mount or, more likely, er, someone or something has pressed down on the end and distorted it.

It *might* be possible to correct the sag by tightening the mount, by adding shims on the under side, or, instead to adjust the bed to mirror the alignment.

Cheerio,

Posted : 28/02/2024 4:48 pm
Extrutim
(@extrutim)
Eminent Member
Topic starter answered:
RE: First layer problems, no solution from support

Your gantry is sagging. Either there is something loose in the mount or, more likely, er, someone or something has pressed down on the end and distorted it.

It *might* be possible to correct the sag by tightening the mount, by adding shims on the under side, or, instead to adjust the bed to mirror the alignment.

But mechanically everything is fine. Without automatic bed leveling, the first layer would be good. The Pinda sensor causes a bad first layer because it thinks the bed is lower on the left than on the right and therefore the Z-axis moves down on the left.

Posted : 28/02/2024 5:26 pm
Eef
 Eef
(@eef)
Trusted Member
RE: First layer problems, no solution from support

 

Posted by: @extrutim

The self-test on the Mini does not include the search for measuring points as on the i3. 

https://help.prusa3d.com/article/mesh-bed-leveling_112163 gives part of the oppertunities of the MK3 etc. 
Should either compensate for differences or give errorsignal. As I understand. 

Posted by: @extrutim

Your gantry is sagging. Either there is something loose in the mount or, more likely, er, someone or something has pressed down on the end and distorted it.

It *might* be possible to correct the sag by tightening the mount, by adding shims on the under side, or, instead to adjust the bed to mirror the alignment.

But mechanically everything is fine. Without automatic bed leveling, the first layer would be good. The Pinda sensor causes a bad first layer because it thinks the bed is lower on the left than on the right and therefore the Z-axis moves down on the left.

 

Posted : 28/02/2024 6:33 pm
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