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Yet and another Y axis layer shift post. Help please!  

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Oxnard111
(@oxnard111)
Active Member
Yet and another Y axis layer shift post. Help please!

So I'm pulling my hair out. I've been experiencing a Y-layer shift lately. Not every print, maybe every 3-5 prints. I can't diagnose it myself. 

Printer history:

  • The printer has a fair amount of hours on it. It's not plugged in, but I think it's around 180 days (I'll update the post when I plug it back in). 
  • I regularly do full maintenance every 200-300 hours, including cleaning and lubricating the smooth rods
  • I'm running the 3D Que AutoFarm on this printer. The problem is more pronounced when the kit is installed and angled but still exists when the printer is on a level surface. 

Symptoms:

  • Layer shift happens pretty consistently after the first 5-7 layers
  • The shift is always in the same direction (the print shifts closer to the back of the bed)
  • The distance of the shift is pretty consistent, about 1-2cm

Things I've inspected with the belt still attached:

  • Smooth rods are fine. No grooves. 
  • The smooth rods are not overly lubricated.
  • The U bolts for the bearings are not loose or overly tight
  • The bed slides smoothly with no binding spots. 

I removed the belt and inspected the following:

  • The Stepper motor spins freely
  • The idler spins freely
  • The belt has been visually inspected. It seems fine to me. 
  • The bed glides on the rails perfectly smooth.

Belt tension:

  • I've set the tension according to the Prusa assembly manual (grabbing the stepper motor with pliers and pushing on the plate; the belt does not flex) 
  • I've checked that tension against the GT2 Belt tension gauge, and it's smack dead in the middle. (Granted, I printed this gauge a long while ago, so time and humidity might have altered its effectiveness. 
  • Plucking the belt makes a nice tone

 

I seriously don't know what to do or try next. Maybe replacing the belt because it has a flaw that I can see/feel? 

This topic was modified 5 months ago 2 times by Oxnard111
Posted : 22/09/2023 4:32 am
Tim Weston
(@tim-weston)
Estimable Member
RE: Yet and another Y axis layer shift post. Help please!

The one thing that I do not see listed in your remediation attempts so far, is checking the screws on the Y-motor pulley. If they are loose, the pulley can have some rotational play on the shaft which will usually show up as layer shift. See step 28 of the Y-Axis Assembly instructions.

The same issue can appear on the X-axis too, so it is worth checking both of those during your routine maintenance.

I hope that helps.

Cheers,

Tim 

Posted : 24/09/2023 9:43 am
Oxnard111
(@oxnard111)
Active Member
Topic starter answered:
RE:

Thank you for the reply. 

I had missed that I checked the set screws on the motor pully. When the best was removed, I loosened both screws and tightened them in the proper order. 

I'll also check the X axis pully screws. 

I broke it all down again and cleaned and re-lubed the bearings. I found a tiny, nonlinear scar on one of the rods. I made sure to align that spot to not come in contact with the bearing surfaces. 

So far I've gotten 6 or 7 after the Y axis second breakdown and rebuild. So far so good. If anything print quality seems a bit better as well. 

Posted : 24/09/2023 10:45 am
Tim Weston
(@tim-weston)
Estimable Member
RE: Yet and another Y axis layer shift post. Help please!

Looks like that has sorted it!

Cheers,

Tim

Posted : 24/09/2023 11:20 am
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