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Back to PLA and Back to Layer Shifts  

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rudye.m
(@rudye-m)
Active Member
Back to PLA and Back to Layer Shifts

Hi Everyone,

The last couple of months, I've been printing with PETG and having really good results.  I got it dialed in, and printed a couple of sets of facemask parts and 7 different trays for organizing screws and such.

Today, I switched back to PLA to print some gears for a friend.  I had some initial difficulties. It seemed to be going faster than the plastic flowed, so I took the speed down to 75%.  And I had an adhesion issue.  So I took off the bed and washed it with dish soap.  Both of those seemed to fix the starting issues, and I let it run.

After a couple of layers, it shifted. Layer shifting in x plagues my printing. Before I tuned to PETG and was printing with it, I was commonly having this problem.  I've tried tightening the belt, and I've tried relaxing the belt.  The bed moves smoothly.  I just don't know why this is happening and happens so sporadically.

Could there be some difference between the PETG printing and the PLA printing to account f0r this?  The PLA printing runs faster, I guess.  The stuff I was printing in PETG had little to no infill. But this shift happened in the starting layers before it got to the infill.

I do still have drylin bearings on the x-axis.  I originally installed them all around, but recently removed them on the other axes when I did the MK3S conversion a couple of months ago. I've been suspicious of them, but like I said, I've been having really good results lately and the only thing changed is moving to PLA.

I appreciate any insight the community has about this layer shifting.

Posted : 11/10/2020 8:59 pm
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(@)
Illustrious Member
RE: Back to PLA and Back to Layer Shifts

That type of shift is usually ungreased bearings, a loose drive pulley, or adhesion that let the part lift and jam the exptruder.

Posted : 11/10/2020 9:14 pm
rudye.m
(@rudye-m)
Active Member
Topic starter answered:
RE: Back to PLA and Back to Layer Shifts

OK, I did a few things and got the print to complete without any problems.

First, I changed the volumetric flow rate in the slicers. This was the main difference I new about between the settings for PETG vs PLA.  PLA defaults much higher, 15 vs 8 for PETG. (sorry, I'm not sure of the units and don't have it in front of me right now.) So, I resliced at 8.  But on my next try it still shifted.

I realized, though, that it was shifting when it was moving between the two models.  Having multiple models was also different from the prints that have been completing successfully.  Those were all one at a time.  So, I halved the speed for movements when not printing.

But, I also put some grease on the rails before the next attempt.  The next one worked without a hitch so it seems that either reducing the non-printing movement speed, or the grease, allowed it to work.  It was probably the grease.

Posted : 12/10/2020 8:20 pm
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