Permanent layer shifts on Y-axis, no remedy working
 

Permanent layer shifts on Y-axis, no remedy working  

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Andy2232
(@andy2232)
New Member

My MK3S was running for monthis without any issue, but now i am facing layer shifts on Y-axis at most print jobs.
The layer shifts occur every 2-5 layers and always in the same direction (shifting towards printer backside).
I am printing currently with Prusament PETG using Prusaslicer 2.2

Here is a list of things i have already checked/tried:

- All axis are perfectly clean and freshly lubed
- No signs of jerk or restistance when moving the bed manually (Y-Axis)
- Even checked moving while pushing/pulling the bed slightly up/down
- Turned crash detection off: no change
- Changed to a new clean nozzle (to avoid blobs blocking the nozzle when moving)
- Did several new XYZ-calibrations and first layer calibrations
- Tried temp +/- 5/10/20 degrees
- Tried different filament brand/color
- Rotated print object 90 degrees
- Checked belts tension, nice high-pitch sound, belt values after running selfcheck: X 267, Y 286

Here some fotos of the layer shifts:

left one is from current print, others are from previous prints. Shifting occurs on different layers (seems random)

 

Printer details:
Printer Firmware 3.9.0
MK3S+MMU2S without any modifications
MMU2S currently turned off, Filament directly fed to extruder

This topic was modified 1 month ago 2 times by Andy2232
Posted : 13/08/2020 8:22 pm
Andy2232
(@andy2232)
New Member

Update:

now the layer shifts occur in both directions, Y and X.

I tightened the belts again (both values about 250), but no improvement.

Posted : 15/08/2020 1:23 pm
steven.c17
(@steven-c17)
Active Member

I'm afraid I'm not much help, but I've had similar issues recently.  Everything also looks good to me mechanically and I've done all the troubleshooting stuff you've listed.

It's still too early to tell for sure if this really "solved" it for me, but so far I'm having better luck after turning the acceleration way down in PrusaSlicer (I set everything to 400 as an initial test).  I'm not entirely sure where this leads us in terms of a proper fix if it does help, but it might be worth trying.

Posted : 23/08/2020 5:23 am
Neophyl
(@neophyl)
Noble Member

Small layer shift like that are usually caused by loose pulleys on the motors. There are 2 grub screws on each, they must be tightened in a specific order otherwise they can work loose over time. You first have to tighten the one against the flat of the motor shaft and then the second jam screw to lock it in place. If not done properly they loosen and wiggle side to side. 
Belt tension means nothing if the pulley is loose. 

Posted : 23/08/2020 10:24 am
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