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Y-Z Axis Skew Correction?  

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FergyMcFerguson
(@fergymcferguson)
Active Member
Y-Z Axis Skew Correction?

Hello everyone,

I have recently been printing the Prusacaster on my MK3S and noticed that I have a pretty significant skew on the Y – Z axis. As the model prints, the subsequent layers will slowly move towards the back of the bed on the Y axis. I have not noticed this before, because I am not taking any large parts that require dimensional accuracy. I have run the XYZ calibration multiple times, I have made sure that all the screws in the frame, stepper motors, pulley mounting brackets, basically every screw I can get to is tight.  I also removed the smooth rods on the Y axis to make sure nothing was caught between the rod and its mounting bracket and re-zip tied them.  After this I printed a 60x60mm cube and the problem persists.  My belts are all adequately tight and I can’t perceive anything slipping.  It almost seems as if the upright frame isn’t square to the extruded bars.  I’ve triple checked that all the screws on the extruded bars are tight (not over-tightened or stripped). Also the plates at the front and back or the y axis are tight to the extruded bars and there is no play in them.  None of my smooth rods are bent or warped. I’m not sure how else to go about fixing this short of re-building the frame. Is there any kind of manual skew compensation in the firmware or PrusaSlicer? 

Other notes: happens on any filament and is not specific to a brand, firmware is up to date to latest, using PrusaSlicer 2.6 alpha 5, but I’m pretty sure this is hardware and not software related. 

Thank you in advance for any help you can provide! 

Posted : 18/03/2023 11:37 pm
FergyMcFerguson
(@fergymcferguson)
Active Member
Topic starter answered:
RE: Y-Z Axis Skew Correction?

Upon further investigation, my entire upright frame seems to be leaning back towards the back of the printer. When I put my square on the print bed, the edge of the square will only touch the bottom rod of the X axis and as I move the X axis up the Z axis towards the top of the printer, the bar gets further away from the square.  Not sure how to fix this. Any help is appreciated.  

 

Posted : 19/03/2023 5:45 pm
trudslev
(@trudslev)
New Member
RE: Y-Z Axis Skew Correction?

Did you try what he's doing in this video?

Posted : 19/03/2023 6:42 pm
FergyMcFerguson
(@fergymcferguson)
Active Member
Topic starter answered:
RE: Y-Z Axis Skew Correction?

yep! Unfortunately, I fail the third measurement and there is no way to adjust for that manually that I’m aware of. I have completely disassembled the printer and my frame is bent. I took it out into the garage and hammered it as flat as I could get it with a rubber mallet and re-assembled it, re-ran the xyz cal which now says I’m 0.01° skewed which was exciting to see. Unfortunately the y-Z skew is still present but significantly improved so it appears the xyz calibration tool can’t compensate for it and it’s still not accurate enough to re-print the Prusacaster parts yet. I may add some shims to the Z axis caps temporarily to compensate the skew but ultimately I will have to either buy a new frame or consider the bear upgrade. Not sure how I’m going to proceed for a permanent fix yet. I have no idea how the frame would have become bent unless hanging two 1kg rolls of filament from the filament holder would have done it.  I spoke with Prusa Support via chat and they said there is no other software compensation for it like klipper can do. Sadface.emoji

Posted : 20/03/2023 7:33 pm
Philip
(@philip-6)
Member
RE:

I was able to fix this by printing as tall a rectangle as I could print and register with my square tool, then I measured the height and offset. Using a linear relationship I calculated how thick a spacer I would need at the top z axis bracket using the height from the bottom of the rod to the top (~12.375"). I ended up needing a ~0.184" spacer and that brought it as perfectly into square as I could identify. I wouldn't be surprised if this issue is more prevalent and people making small parts or not assembling parts just never noticed.i only noticed because I was making interlocking cylinders that had obvious gaps from actually being parallelograms.

This post was modified 4 months ago by Philip
Posted : 17/12/2023 7:48 am
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