Consistent Layer Shift on Y-axis

[mcmuffin6o 3]

My Ender 3 Pro shifts on the y-axis only for certain prints in certain configurations, but when it shifts, it does so consistently, indicating that it is likely a software problem. Attached are pictures of three attempts to print an A and an L. I have laid them out as I printed them to show the effects of my rearrangement within the software. The last attempt I let run all the way until the stop at layer command I put in post-processing, but the other two I stopped as soon as they shifted. I am printing translucent red PETG on a 1 mm nozzle with the attached speed settings. I'd appreciate some help with this! Thank you all so much in advance. 

[GregValiant 1,251]

In Cura use "File | Save Project" and post the 3mf file here.  That will contain the model, the printer, and your settings.

You can post the problem gcode file as well.  Somebody will take a look to see what is going on.

[mcmuffin6o 3]

Thanks! I have attached the .gcode and .3mf files.

AL.3mf AL.gcode

Edited March 28, 2021 by mcmuffin6o
Information Update

[mcmuffin6o 3]

Got to upload these quicker than I thought :)

[GregValiant 1,251]

Your Print Speed (15), Accel (500) and Jerk (7) are really conservative so I don't see it being a belt skipping (even if it was really loose).

I read the gcode file into AutoCad (to take Cura out of the loop).  Everything looks good in the gcode.  All the speeds are right and everything lines up with no layer shift.

The models themselves are watertight.  Each consists of 3 sub-meshes.  That is repairable but that doesn't have anything to do with a layer shift because the resulting gcode is good.

 

I think that somehow someway it's in the printer.  I'll think on it but right now nothing is coming to mind.  Maybe @gr5 has a thought.  @Mari also has an E3Pro and might have seen something like this as well.

[mcmuffin6o 3]

Damn, that's really annoying. I appreciate you going through my files though, and my search is narrowed. Maybe I'll try updating the firmware again, I want to get rid of the primer line that marlin enables by default anyways, because it does not account for nozzle diameter and if I wanted to do finer prints I would prolly take a dookie on my extruder motor before it even got started.

 

Thanks again!!

[GregValiant 1,251]

The primer line is in the Cura start Gcode.  If you just put a semi-colon in front of the lines from "Move to start position" to "draw the second line" they will be treated as comments instead of commands.

 

Take a really close look at the mechanics of the printer again.  Make sure that nothing wobbles, there are no loose screws, the print head and the table just move back and forth nicely on the wheels with no weird movement, the glass is going to stay where it's put, that kind of thing.  Even the hot ends have been known to come loose on these.  It's in the printer and I highly doubt that it's the firmware that is responsible for the shift.

There is no feedback loop on these to tell the printer/processor "OK, I'm at X,Y,Z,E".  Instead, the processor knows how many steps were sent and where the axes locations are supposed to be.  It just keeps merrily translating gcode not knowing that something has changed position.

 

[mcmuffin6o 3]

I have videos to show you! We will see when I can get around to uploading them. Should I just zip them so that they can get through?

[mcmuffin6o 3]

Okay, here's a .zip containing three videos: one of the very sturdy, free moving bed, one of a strange periodic catching on the x-axis, and one "kachunk" noise that accompanies the layer shift. The sound happened after the last good layer and before the first bad layer. What is happening? Should I take another video with a better angle? Thanks so much in advance!

1503748680_Ender3ProDiagnosticVideos.zip

[GregValiant 1,251]

The bed looks good.  The belt appears to be adjusted correctly.

 

The Kachunk seems to be the nozzle hitting a blob someplace.  As I recall the layout of those parts a travel move shouldn't be hitting anything, but it can happen.  Enabling Z-hops at 1mm is the easy fix but can come with a downside regarding the final finish of a print.  As an aside, I wrote a post-processor for myself that goes through a gcode file and gets rid of Z-hops (because @gr5 here kept insisting they are a bad idea).  I just leave the ones that are in the layers where I know they are needed.  This also might relate to the catching of the X.

 

The periodic catching on the X may be a flat spot on a wheel.  I notice that it occurs when the mark on the left wheel in the video is about straight up every time it catches.  What we can't see is the bottom wheel and it's condition.  I vote that you wipe the dust and crud off the wheels and clean the tracks in the X-beam.  Then loosen the bottom wheel and adjust the cam (using the large hex).  When the wheels are adjusted correctly you should just be able to rotate them with your fingers.

 

When I received my Ender 3 Pro the Y wheels were really tight.  There was at least one flat spot since it had sat for a long time in warehouses prior to me getting it.  I adjusted them and after a while the flats went away (or rebounded back).  So now they are gone.  The 3 Pro is supposed to have superior wheels compared to the regular Ender 3.  That could just be more BS from Creality.  The wheels do develop a static charge and pick up dust that needs to be wiped away once in a while.

Edited April 5, 2021 by GregValiant

[mcmuffin6o 3]

Sweet! That's probably what was causing my layer shift then. It's also nice to know that it's probably smacking a blob or something because it probably won't do that when I go back to a typical nozzle size and deposition rate. Just gotta add some z-hops for this particular print and hopefully that'll fix it right up! I will update you once I've tried it. I will also try adjusting the wheels.

 

Thank you so much @GregValiant, I was beginning to lose hope!

[mcmuffin6o 3]

ayooooooo

It worked!!! I actually already had z-hop enabled but it didn't match my layer height so it didn't go high enough. Just adjusted it to be the same as my layer height and no more problems!!

 

Greg is good. Greg is #1. Greg for president.

Edited April 10, 2021 by mcmuffin6o

[GregValiant 1,251]

These stupid machines can drive ya nuts, but when something gets figured out and the thing starts working right again it's a beautiful thing.  Congrats.