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Request to check warped bed diagnosis and next steps  

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jweob
(@jweob)
Member
Request to check warped bed diagnosis and next steps

TL;DR Looking for some help to confirm the diagnosis of a warped bed (or suggest alternatives) and advice on next steps

 

I have had a Prusa MK3S with MMU2S for several years. The MK3S has been very reliable, the MMU2S less so. Last weekend I upgraded to the Mk3S+ and MMU3, and also replaced the hotend at the same time. Perhaps somewhat foolishly I did the Mk3S+ y axis upgrade as well as the extruder upgrade, even though I didn't strictly need to. I now have problems with my first layer with apparently large differences in z offset across the bed. See image for latest failed print - you can see that the layers are too squished at the corners and not squished enough in the middle. I think that poor adhesion due to insufficient squishing caused some of the filament to come loose. I also considered that maybe this was caused by a blob escaping from the hotend, but when I inspected the hotend it was very clean so I don't think this

was the cause

Print failure

This was on a satin sheet, PLA, sliced in PrusaSlicer. I redid xyz calibration (and thermal model, PID) after doing the upgrade with "slightly skewed" result. I have 7x7 mesh bed leveling switched on with 5 points per location and the default magnet setting. I have printed this same print successfully before doing the upgrade. I have tried the print multiple times including with a smooth sheet.

My suspicion is that I have warped the bed somehow during the upgrade. This seems to be confirmed by G80/G81 results which show a high spot in the front right and lower spots at all the other corners. The bed level calibration test print also seems to imply warping, but it is difficult for me to compare this to the G81 results because the bed level calibration is applying mesh bed leveling. I don't see any obvious warping with a visual inspection. 

 

>>> G81
SENDING:G81
Num X,Y: 7,7
Z search height: 5.00
Measured points:
0.12800  0.12100  0.13050  0.16700  0.22250  0.07100  0.01250
0.15900  0.17500  0.18850  0.28100  0.29650  0.19350  0.09250
0.16100  0.20850  0.23550  0.26188  0.29150  0.24600  0.16050
0.13450  0.16750  0.14950  0.23950  0.26500  0.24850  0.18350
0.15600  0.17800  0.17950  0.23325  0.28050  0.30800  0.24500
0.14050  0.18300  0.21050  0.23350  0.36150  0.39300  0.29450
0.16250  0.19550  0.24450  0.26500  0.35800  0.37750  0.36600

Things I have tried:

  • Loosening heat bed screws and retightening both in Prusa assembly instructions order and in the "center last" order
  • Adding a -50µm adjustment in bed calibration to right and front sides
  • Swearing

My next step is going to be to dismantle the y axis and reasssemble with great care. I will see if I can use the torque wrench I bought for extruder assembly to put uniform tension on all the bolts.

My questions:

1. Am I right that this is bed warping or could something else be causing the issue?

2. Any other suggestions on next steps?

Thanks!

 

Posted : 13/02/2024 10:21 pm
jweob
(@jweob)
Member
Topic starter answered:
RE: Request to check warped bed diagnosis and next steps

I can't work out why the images won't render in the main post  - hopefully this works

 

Posted : 13/02/2024 10:25 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE:

I don't know how you tried to attach the images n the first post, 

But you got some formatting information associated with the pictures and this stopped the image   displaying...

Can you say what you did differently in the first attempt to add images Please?

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 14/02/2024 9:14 am
Robin
(@robin)
Noble Member
RE:

That mesurements should be well inside the capabilities of mesh bed leveling. Look, this is my mesh:

It has a variance of 0,59 and I do not have any problems printing large parts and all over the bed. Perhaps you have some old offsets saved in bed level correction from before the upgrade. Did you perform a factory reset after the upgrade? 

This post was modified 9 months ago by Robin

If at first you don't succeed, skydiving is not for you.
Find out why this is pinned in the general section!

Posted : 14/02/2024 4:37 pm
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