Layers randomly shift in one direction  

RE: Layers randomly shift in one direction

I also tried a number of different PLA filament brands. I'm using Cura slicer with Octoprint, my settings I'd mostly consider default. I also tried using Prusa Slicer and printing without Octoprint. Same result.

RE: Layers randomly shift in one direction

The problem as seen in the first image is resolved now. This might have actually been due to the belt being too lose. I tightened it at least once. The print as seen in the first picture is already quite old. The problem might be unrelated. The shifting occurs (now and then) in the Y direction:

I didn't really look into what did end up fixing my first issue as it didn't affect functionality of any prints but where rather just minor inconveniences to me. But the problem I now encounter is far more problematic to me.

RE: Layers randomly shift in one direction

Thank you! I also checked the tension of the X and Y belts: Not perfect but pretty good, a little too loose, I tightened them the "perfect" amount now (according to: https://belt.connect.prusa3d.com/ ). It seems to have solved the problem, I didn't expect so much tension to be required and it still doesn't make complete sense to me that these random shifts only occured on the layers with e.g. holes (I kind of makes sense when I think about it though), anyway, I'm just going to keep printing in hopes that it'll work now but again, it seems to. 

Thanks a lot! Cheers

RE: Layers randomly shift in one direction

So, we pinned the problem down to: 
- not regular shifting in Y-direction. 
More people struggle with this. So I quote this from another thread I wrote in: 
I own a MK2.5 (very simular to the MK3) and had the same issue.
- The heatbed lays on a carriage laying with 3 bearings and hangs on the 2 Y axis. These should run parallel. 
what should be parallel. Because of Y-axis shifting, I measured my machine (6 years old or so) with a caliper (basic tool for 3d printing) and the axis where mounted about 0,1 mm more apart then the carriage. So only in the middle it was running OK, as soon it go to the end of the axis (front + back) there was tension, causing layer shifts and also caused the bearings to wear out to the sides.
- I adjusted all (keep measuring as you tighten the nuts, difference in tension on inside and outside gives a difference of about 0,1 to 0,2 mm). Using to big wrenches. Only work on 1 side, I choose the right side, because less cables there.
- Loosen the inside nut a bit, then use outside nut to move the axis inwards (just 1/4 or /13 turn). Measure (most easy here to set the inside distance of the axis at the carriage and using that as a reference). Repeat until satisfied. 
- When you loosen the belt (step motor screws, one out and loosen the other) the belt  is not hold by the stepmotor and the carriage can move freely and you feel exactly if there are obstructions. (this repair (I also exchanged the bearings for drylin)) solved my layer shifting problems). 
- mount the motor back. (pull it a bit with your hand so the screw goes in more easily. and check the belt tension. Just use the prusa app for that. If there is a belt tensioner it is easy to adjust it a bit. If no tensioner, then you have to work at the block where the belt is attached underneath the carriage. (loosen motor again, pull out the belt sidewards, shift one link, and push it back. ) 
NB: Tension of belt too low is more worse then too tight (tot tight wears the belt a bit more, over time the tension will lower by itself). So better a bit too tight then too low (do not trust the calibration of belts of the machine, seems that the tuner app is most accurate. And as soon you heard the correct intonation a couple of times you don't need the tuner any more, just do it by ear. 

RE: Layers randomly shift in one direction

1. Best to start with measuring and checking the belt tension. 
2. Loosen the Y-motor to check if the carriage runs freely. 
And go from there.