Layer shifting (Y Axis)  

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MG
 MG
(@mg-2)
Active Member

Hello everyone!

Out of nowhere start getting layer shifting in my print... I already print 50+ of this model.. no issues until the last 2... I followed this article: https://help.prusa3d.com/en/article/layer-shifting_2020 and everything looks fine to me.

Any ideas?

Posted : 08/04/2021 3:01 pm
Dan Rogers
(@dan-rogers)
Honorable Member

No pictures, no ideas.

Posted : 08/04/2021 8:08 pm
MG
 MG
(@mg-2)
Active Member

My apologies!!! Picture didnt get attached!

Here is now.

Posted : 08/04/2021 8:58 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member

I know you have looked at the document but I would suspect either.

Motor pulley screws loose, or not tightened onto the flat?

Belt tension?

This post was modified 1 month ago by Clarmrrsn
Tank you very much!...
Posted : 08/04/2021 9:44 pm
Dan Rogers
(@dan-rogers)
Honorable Member

Looks like the fast acceleration speeds at the top of your print caused the belt to slip a cog during the print.  Download and print the belt tension meter GCODE file from Prusa, dial in the range.  Lower the max acceleraton value on the speed tabl

Posted : 08/04/2021 9:57 pm
MG
 MG
(@mg-2)
Active Member

@dan-rogers

Thanks, I only found 1, and its PET, I only have PLA... would i be able to print the GCODE using PLA?

Posted : 09/04/2021 12:49 am
MG
 MG
(@mg-2)
Active Member

ok, tried to print the PET on PLA...came out just fine.

I test both belts, they look good to me, its right on the min mark. unless i am reading it incorretly!

Posted : 09/04/2021 2:24 am
MG
 MG
(@mg-2)
Active Member

adding 2nd image...

Posted : 09/04/2021 3:35 am
Dan Rogers
(@dan-rogers)
Honorable Member

Do advise to read the print instructions with the tool.  PETG and PLA don't have the same stiffness - so there is no way I can speak to whether your PLA version is just a pretty imitation or usable.    Either way, go to the middle of the range.  Minimum is why you're skipping teeth on high acceleration.

 

Posted : 09/04/2021 7:22 am
MG
 MG
(@mg-2)
Active Member

@don-rogers

I printed again in PETG and test. Look at the pictures below. They both look good, right? I didnt do anything to the belts...just printed in PET and test.

 

Posted : 09/04/2021 6:34 pm
Dan Rogers
(@dan-rogers)
Honorable Member

Great.  Passable belt tension (don't be afraid to take them to the higher side of middle - your belts are new and will encounter some stretch over time.  

The issue in your print is likely caused by a high acceleration as the print head moves between posts - you can hear the high speed movement - and there are settings in Prusa Slicer that let you control how fast the print motors will try and drive the head.  When it changes from slow speed to high speed, the print head inertia plays a role in the reaction where the belt rides on the pully on the X and Y motors.  If it tries to get up to high speed too quickly, the belt tension (yours still are on the low side for my own comfort zone for fast printing) allows the belt to develop a wave shape and that wave skips a tooth on the cogs on the pulley.  After that happens, your printer doesn't know it skipped a tooth, so it now has a very different, slightly shifted coordinate system and keeps on printing where it thinks the previous layer was - which is now a full tooth over.

So you can set the max acceleration (rate of change) and the max speed for high speed moves as a way to tune out issues from time to time in a print like this one that is prone to layer shifting due to belt tension or pulley tigtness (pulleys can wiggle, but that doesn't cause layer shift)

 

Posted : 09/04/2021 6:41 pm
MG
 MG
(@mg-2)
Active Member

Ok... worked on the tension and move them close to high...clean everything and still getting the same shifting problem.

 

@dan-rogers

to make the changes I need to run it thru the slicer again  right? If so, do you know why the speed changed? I'm using the same gcode that I uploaded on my octoprint and have been using it to print, no changes, just select and print.  I did at least 30 pieces and no issues until now.



Posted : 14/04/2021 3:27 am
Clarmrrsn
(@clarmrrsn)
Honorable Member

@MG-2

You coudd try just turning down the speed with the control knob once the large surface is complete.

Or use this method to change speed at layer X https://forum.prusaprinters.org/forum/prusaslicer/speed-control-in-prusaslicer/

Are you sure the grub screws on the Y motor pulley are tightened cirrectly?  

 

Tank you very much!...
Posted : 14/04/2021 8:24 am
MG
 MG
(@mg-2)
Active Member

 

Ok, now seems that Y needs to be less tight as the shifting is on the opposite direction, right?

I will also check the screws on the Y motor, just to make sure are tight. 

Posted : 15/04/2021 1:45 am
Dan Rogers
(@dan-rogers)
Honorable Member

There is a proper order to tighten the pulley screws. If done in reverse order, they will loosen.

To be clear, tightness is not causing opposite layer shifting.  Something is wiggling around - either the belt is loose, or the pulley is loose as a starting point.  Or ... advanced setting - slow down your acceleration to half what it currently is, and try printing.   If it eliminates the problem, it's the belt slipping a cog.

 

Posted : 15/04/2021 2:27 am
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