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Analysed problems with MINDA probe  

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marcel.mayer
(@marcel-mayer)
Active Member
Analysed problems with MINDA probe

Hello Community,

I would like to share my results of an analysis of my Prusa Mini.

Problem description
The bed leveling was fine and I startet a print (PLA 215/60°), which was sucessfull. Then I started a second print, and the first layer was more than 1mm too high. Fixed that with live adjustment. So far so good.
One day later I changed to ASA (260/100°) and the nozzle scratched my steel sheet and destroyed it.

That was driving me crazy and I made so many first level calibrations to fix it, bot nothing helps. For me the probe seems to be fine checked with this manual:
https://help.prusa3d.com/de/article/minda-testing_134024 --> All fine!

Then I went to a friend with a working Prusa Mini to do some tests... Our test setup was an RPI with octoprint and bed level plugin.

Results

First run with my Mini (cold state)
Recv: Bilinear Leveling Grid:
Recv: 0 1 2 3
Recv: 0 +0.093 +0.179 +0.075 -0.075
Recv: 1 +0.041 +0.186 +0.114 +0.028
Recv: 2 -0.062 +0.078 +0.127 +0.118
Recv: 3 -0.104 +0.059 +0.132 +0.108

Second run with my Mini (preheated from first run)
Recv: Bilinear Leveling Grid:
Recv: 0 1 2 3
Recv: 0 +0.141 +0.187 +0.077 -0.059
Recv: 1 +0.059 +0.197 +0.141 +0.090
Recv: 2 +0.057 +0.193 +0.210 +0.203
Recv: 3 +0.040 +0.179 +0.252 +0.267

Third run with bed temp 100°
Recv: Bilinear Leveling Grid:
Recv: 0 1 2 3
Recv: 0 +0.102 +0.190 +0.085 -0.072
Recv: 1 +0.076 +0.259 +0.212 +0.151
Recv: 2 +0.108 +0.283 +0.307 +0.273
Recv: 3 +0.076 +0.243 +0.315 +0.323


First run with another Mini (cold state)
Recv: Bilinear Leveling Grid:
Recv: 0 1 2 3
Recv: 0 +0.725 +0.488 +0.221 -0.032
Recv: 1 +0.811 +0.613 +0.366 +0.058
Recv: 2 +0.813 +0.582 +0.373 +0.112
Recv: 3 +0.799 +0.544 +0.375 +0.107

Second run with the other Mini (preheated from first run)
Recv: Bilinear Leveling Grid:
Recv: 0 1 2 3
Recv: 0 +0.746 +0.467 +0.201 -0.015
Recv: 1 +0.776 +0.554 +0.305 +0.031
Recv: 2 +0.781 +0.524 +0.319 +0.093
Recv: 3 +0.803 +0.531 +0.352 +0.126

Third run with bed temp 100°
Recv: Bilinear Leveling Grid:
Recv: 0 1 2 3
Recv: 0 +0.679 +0.454 +0.208 -0.042
Recv: 1 +0.790 +0.598 +0.368 +0.066
Recv: 2 +0.781 +0.564 +0.368 +0.116
Recv: 3 +0.761 +0.518 +0.351 +0.101

 

Reason and solution
As you can see, my MINDA probe seems to be more and more confused, then warmer it gets. So it is faulty. My replacement is one it's way for free by Prusa.
This seems to be a problem in general with this sensor and it is definitly not a work around to heat it up before as recommended by many in here.
It's just damaged and needs to be changed by Prusa ...

Posted : 21/09/2020 7:05 pm
marcel.mayer
(@marcel-mayer)
Active Member
Topic starter answered:
RE: Analysed problems with MINDA probe

Status update: New MINDA arrived, problems gone!

Posted : 22/09/2020 3:26 pm
Dimonstar
(@dimonstar)
Active Member
RE: Analysed problems with MINDA probe

Great, thanks for reporting back!
I’m waiting for replacement MINDA now as well. Hoping new one will be working correctly.

Posted : 27/10/2020 6:13 am
spajkej
(@spajkej)
New Member
RE: Analysed problems with MINDA probe

Hello, anyone tried this? Piece of paper glued used hot glue. Im still testing but 10 test prints and success. Z offset perfect all time.

 

This post was modified 2 years ago by spajkej
Posted : 25/11/2020 7:16 pm
toz liked
toz
 toz
(@toz)
Eminent Member
RE: Analysed problems with MINDA probe

Paper against heat - or magnetic interference?

may i give it a try...hmmm

Posted : 02/01/2021 12:51 pm
spajkej
(@spajkej)
New Member
RE: Analysed problems with MINDA probe

@toz

Well, after 2 months printing almost everyday.... it works. Z offset set to -0.905 since tests started

Posted : 02/01/2021 5:39 pm
toz liked
bobstro
(@bobstro)
Illustrious Member
RE: Analysed problems with MINDA probe
Posted by: @spajkej

[...] Well, after 2 months printing almost everyday.... it works. Z offset set to -0.905 since tests started

I don't have a Mini to test with, but I love the simplicity of your approach. If heat is the problem, insulate against the heat. It seems SuperPINDA is Prusa's long-term fix, but you've got a possible answer for those who can't or won't upgrade. Now I'm wondering if a reverse approach would have worked for PINDAv1 (which I do have). Build up a little heat mini enclosure around the PINDA to contain the heat. 

This feels a bit like finally finding an elegant solution to problems I had on my Apple II computer. Late, but still good to know about.

 

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 02/01/2021 8:08 pm
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