Printing is shifting at random height, WHY?
 
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Printing is shifting at random height, WHY?  

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BID3D
(@bid3d)
Eminent Member
Printing is shifting at random height, WHY?

Print job is shifting at a random height. Print job has shifted to the rear of the platter. The print is a 3 legged object with smooth diameter legs, but the printer is performing a rearward shift during print operation. Print job was at ~25 hours into a 50 hour job.

When the defective printing was noted, print job was canceled. The object was strongly adhered to the bed, the print did not move, the printer shifted where is actively printing toward the rear of the platter.

Printer was in hardware specs before print job was stared. Printer passed all calibration tests prior to print. Printing from USB on a MK4, firmware version 5.1.2+13478

PrusaSlicer 2.7 1.

Prusament Black PETG on a textured print platter.

 

Posted : 21/03/2024 3:19 pm
fuchsr
(@fuchsr)
Famed Member
RE: Printing is shifting at random height, WHY?

The usual suspects:

  • belts not correctly tightened
  • grub screws on motor shafts not tight

Another common reason is the nozzle hitting an upward curling perimeter or infill. Most common with infill types such as grid in which lines intersect in every layer and can create pileups at the intersections. 

Posted : 21/03/2024 5:07 pm
lee.krasnow
(@lee-krasnow)
Active Member
RE: Printing is shifting at random height, WHY?

Here is a possibility I have encountered before which is that maybe when it is doing the auto-homing routine the Y-axis is hitting something squishy like a zip-tie or cable instead of something firm like the hard limit of the axis travel.  If for some reason during the print there is a power fluctuation or it thinks it detects a crash then it might try to rehome the XY axes before continuing the print.  If the home is squishy then it might result in problems like that.  I have had similar issues on the X-axis with my MK3 machines because I was not careful enough about how I "clocked" the zip ties  holding cables coming out of the back of the print head.

Posted : 21/03/2024 5:32 pm
BID3D
(@bid3d)
Eminent Member
Topic starter answered:
RE:

Me too. What material are you using ? What layer height are you using? What infill type/% are you using? What temperature.

I have seen positive Y axis failures at random heights Prusament PETG, .15 layer with a .25 nozzle, gyroid infill @ 40%, standard temps from MK4IS profile for PETG.

My MK4 kit has 100+ hours. Random failure as described, always positive Y axis failure.

My theory, is the that the shifting is due to a combination of settings; number of perimeters, layer height, along with high % of gyroid infill and alinged seams are the likely culprits along with a standard retraction height. Thinking that an infill glob is causing a nozzle crash. 

Experimenting on a solution:

I have lowered the # of perimeters, reduced the infill percentage, raise the retraction height and ramping on, increased the layer thickness from .15 to .2. Also changed seams to random.

MK4 using IS profile, .25 nozzle, Printed Solid PETG, default temps. MK4 belt tension is good, all machine fasteners and belts pulleys are in spec. XYZ calibration is good, 5.7.1 firmware, Using Prusaslicer, Wifi upload.

With increases to the retraction height, ramped the retraction, increased layer height to .2mm, no failure yet.

Belt tension is good, XYZ axis calibration is good. Using PrusaSlicer 2.7.1 MK4 firmware is 5.1.3

This post was modified 1 month ago 2 times by BID3D
Posted : 06/04/2024 2:13 pm
BID3D
(@bid3d)
Eminent Member
Topic starter answered:
RE: Printing is shifting at random height, WHY?

I changed to the NonIS profile and the layering failures quit.

MK4 on 5.1.2 firmare using PrusaSlicer 2.7.1 , a 0.25 nozzle, 0.2 layer height, 4 perimeters, 40% Gryoid infill, random seams, Prusament  or Jessie PETG.

MK4 passes all calibration tests, belt tension within specifications of belt tuner app.

I could never print successfully above ~100 mm Z height, irrespective of part geometry.

Y axis layer shifting to the rear at random Z levels was intermittent. 

I thought maybe the culprit was excessive globs left during infill printing but could not ever witness the layer shift failure.

 

Posted : 12/04/2024 5:11 pm
fuchsr
(@fuchsr)
Famed Member
RE: Printing is shifting at random height, WHY?

The truth is I've given up trying to use IS with PETG. I haven't been able to make it work reliably without running into issues. The few minutes saved are not worth it for me to spend more time trying to get it to work. 

Posted : 12/04/2024 5:38 pm
BID3D
(@bid3d)
Eminent Member
Topic starter answered:
RE: Printing is shifting at random height, WHY?

https://forum.prusa3d.com/forum/postid/669070/

after reading this post and the associated GitHub discussion., I think my layer shifting is rooted in the method used to transfer the file to the printer.

 

 

 

Posted : 20/04/2024 3:20 pm
Walter Layher
(@walter-layher)
Prominent Member
RE:

I observed these layer shifts when printing PETG with IS on the MK4 as well. And I am using OctoPrint and have never used PrusaLink or PrusaConnect. I don't even have the USB stick in the printer, except for firmware updates. I switched to the profile without IS and the layer shifts are gone. They did not occur every time, only sometimes and not at repeatable heights. So I am of the same opinion as @fuchsr, I think it is not worth the saved time when the result is not certain.

Posted : 20/04/2024 4:10 pm
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