Shift occurs at same Z height on most prints
 
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Arrakis90
(@arrakis90)
Active Member
Shift occurs at same Z height on most prints

I've been troubleshooting this for many months now and while the problem occasionally will go away, I cannot get a true fix. I've had to resort to not using input shaping because the shifting becomes very bad compared to the slight shift during normal printing. I've checked my grub screws and tightened up screws on the X-axis motor to little avail. I've repeatedly run belt tuning via the web app and it says I'm in the green on both belts.

I use the MK4 for my business so getting it back to the quality I had is a rather critical need. I've attached a photo of a print that's in progress using non-input-shaping (the green ones) as I type this as well as one of some printed with input shaper turned on.

Posted : 31/08/2024 10:12 pm
Arrakis90
(@arrakis90)
Active Member
Topic starter answered:
RE: Shift occurs at same Z height on most prints

Bump. Just another point, this shift is always in the Y direction at these consistent heights.

Posted : 06/09/2024 4:35 am
Mike B
(@mike-b-3)
Trusted Member
RE: Shift occurs at same Z height on most prints

I saw a post earlier this year where print issues were being caused by loose screws on the heatbed itself.  I'm wondering if the higher accelerations used by input shaping is causing the bed itself to shift on the heated element?  It's pretty easy to just check the screws with the print plate removed.  Then there's the Y-axis belt anchor underneath the bed as well although if your tension is good it shouldn't be that.  Lastly, see if you can watch/witness the issue - set a timer (in Prusaslicer you can see the print duration to any specific layer by hovering over the vertical slider on the right) and show up in time to watch a few layers...

Posted by: @arrakis90

Bump. Just another point, this shift is always in the Y direction at these consistent heights.

 

Prusa MK4 since Jan 2024, Printables: @MikeB_1505898

Posted : 06/09/2024 7:07 pm
Arrakis90
(@arrakis90)
Active Member
Topic starter answered:
RE: Shift occurs at same Z height on most prints

 

Posted by: @mike-b-3

I saw a post earlier this year where print issues were being caused by loose screws on the heatbed itself.  I'm wondering if the higher accelerations used by input shaping is causing the bed itself to shift on the heated element?  It's pretty easy to just check the screws with the print plate removed.  Then there's the Y-axis belt anchor underneath the bed as well although if your tension is good it shouldn't be that.  Lastly, see if you can watch/witness the issue - set a timer (in Prusaslicer you can see the print duration to any specific layer by hovering over the vertical slider on the right) and show up in time to watch a few layers...

Posted by: @arrakis90

Bump. Just another point, this shift is always in the Y direction at these consistent heights.

 

Thanks, Mike. I checked the bed screws just now and didn't find any of them loose. I'll see if I can track down the moment to watch for in my next prints.

Posted : 06/09/2024 11:18 pm
derekp7
(@derekp7)
Member
RE: Shift occurs at same Z height on most prints

If this is happening at the exact same layer, I don't think it would be anything loose otherwise the shift would happen multiple times and at random spots.  Only thing I can think of is an issue with the Z-axis rods, bearings, or screws.  Use the Z-axis manual adjustment, lower the extruder all the way, then set a value higher than where the bad layer is, and observe is there is a jump (also, rest your finger on the front of the two carriage ends, sometimes they will feel something that your eyes don't catch).

Posted : 07/09/2024 1:33 am
RadekP
(@radekp)
Active Member
RE: Shift occurs at same Z height on most prints

Hi,

Try to enable printer/extruder "Steeper ramp before obstacles".

I reported it as feature request https://github.com/prusa3d/PrusaSlicer/issues/13235

 

Regards, RP

Posted : 07/09/2024 2:42 am
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