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Y axis skew, difficulty correcting.  

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phillip.gooch
(@phillip-gooch)
New Member
Y axis skew, difficulty correcting.

I got my mini a while back and everything was working great initially. After I became comfortable with it I tried printing something really tiny. At one point while experimenting with setting to reduce some stringing something went wrong, I heard a noise from, the other room and the printer had jumped, or been pushed, along the Y axis. While the effect was kinda neat I think thats what caused the skew.

 

Now I haven't been printing a lot of dimension specific things recently but I noticed things were off when I tried to print a case for a PCB, thats when it because clearer that there was some serious skew on my Y axis. just in a sub 100mm space in the middle it was around 1mm off. 

 

A cursory search revealed no software fix for this so I decided to print some shims to place at the back of the right (tower side) extrusion. Doing some math based on a skew check square I figured it was about 1.244mm off at the back right corner of the printing area. I whipped up a few shims and tried them out, the results were better but still not perfect.

 

That was all Friday I spend the weekend printing skew squares and shims. This has been less than smooth as I have to loosen the control box to get the shim back, and I feel inconsistencies in the prints and in how I tighten the hex screw that attaches the tower to the Y axis is going to make it effectively impossible to get it fully dialed in. 

 

For instance I have been printing these squares: https://www.thingiverse.com/thing:2563185 . The difference between A and C (thats the bottom left corner and the top right corner as it prints on the bed) minus the difference between B and D (the other corners) for a un-shimmed print is (I think, the one I am measure is unlabeled and might have thin shim in it already) is 140.62 - 141.8 = 1.18mm and the best I've come up with so far, 1.344 (or as close as can be printed to at .05mm layer height) is 141.4 - 140.6 = 0.8mm. All numbers measured with Vernier calipers.

 

My goal is to be able to measure the A/C size, lock my calipers to that size, pick up the square by the calipers (it holds in well) then without resizing the calibers pick it back up from the B/D corners. Does that seem like a reasonable expectation in terms of calibration?

 

I'm wondering if anybody else has had similar issues trying to sort out bed skew. Any tips to make this process simpler and the changing of the shims more consistent. 

Posted : 18/05/2020 9:16 pm
phillip.gooch
(@phillip-gooch)
New Member
Topic starter answered:
RE: Y axis skew, difficulty correcting.

I just finished another test and got it down to .2-.3mm which is probably fine but at this point I think I might keep going. Considering the design of the printer I'd kinda expect a software skew calibration on the Y.

Posted : 19/05/2020 4:42 am
3Dprintedgr
(@3dprintedgr)
Estimable Member
RE: Y axis skew, difficulty correcting.

Can you share the shims you used for your fix?

Original Prusa Mini + Smooth PEI
Prusa Slicer 2.2.0...
Posted : 19/05/2020 5:54 pm
phillip.gooch
(@phillip-gooch)
New Member
Topic starter answered:
RE: Y axis skew, difficulty correcting.

@geoper2

I never got it fully fixed, ands while working on the problem I ended up getting some PLA stuck in the hot end (no clue how, I printed tons with this filament and haven't had anything like that happen). It's stuck in there good leaving it at 260 for a few minutes it never seemed to loosen, I ended up breaking the filament trying to get it out, so now it's stuck and un-grabbable. I'm starting to think I'm done with this experiment, I've produced nothing useful with it and it's been a real pain in the ass most of the time. I've wasted most of a roll just calibrating it this time. I'm not sure I have the energy or motivation to rip the entire thing apart just to put it back together again, just for it to still have a skew problem.

At any rate I have an STL containing shims from +1.5 to +2.05. Your gonna want to flip them shim side down to take advantage of the better Z resolution. I need to wait 24hrs before uploading them to thingiverse, but I could put them somewhere else if you don't want to wait.

Posted : 19/05/2020 6:49 pm
phillip.gooch
(@phillip-gooch)
New Member
Topic starter answered:
RE: Y axis skew, difficulty correcting.

@geoper2

https://www.thingiverse.com/thing:4378040

I did clear the block, luckily it didn't require a full teardown, and I get mine squared better (good enough for now) using a 1.75mm shim.

Posted : 23/05/2020 2:23 am
3Dprintedgr
(@3dprintedgr)
Estimable Member
RE: Y axis skew, difficulty correcting.

Thank you i will try it

Original Prusa Mini + Smooth PEI
Prusa Slicer 2.2.0...
Posted : 03/06/2020 12:27 pm
Ameen
(@ameen)
Active Member
RE: Y axis skew, difficulty correcting.

I'm having the same issue, I talked to support they advised to re-assemble the XZ-axis assembly, I tried but ended up with same results.

I'm printing the shims you shared now, I hope one of them will fix the skew.

Posted : 05/09/2020 7:10 pm
Ameen
(@ameen)
Active Member
RE: Y axis skew, difficulty correcting.

I placed 1.5mm shim, that minimized the skew issues but I started getting inconsistency in extrusion, as soon as I removed the shim the printer started printing normally but off course I'm back to the skew issue. I don't understand why the shim caused an issue with extrusion!!

Posted : 06/09/2020 9:34 pm
Ameen
(@ameen)
Active Member
RE: Y axis skew, difficulty correcting.

Well, inconstant extrusion seems to be unrelated issue, it started to happen again.

Posted : 06/09/2020 10:37 pm
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