Why the Layer Distortion in a print?

[Lawzy 0]

Hi and I’m hoping someone in the community can assist me with a printing defect that occurs during some prints, but consistently when it appears on a design (object). The one I’m sharing here is a case that has a filleted grove along the middle of the top edge. I am using:

• Printer: Ender 3 pro
• Material: Creality ST-PLA
• Print Speed: 50mm/s
• Slicer: Cura 4.6.0

 

As can be seen in the attached images of the case, there is a layer distortion aligning with the start of the filleted section and is very pronounced on the corner. In addition to this distortion, the final layer prints wider than the width of the underling layers. I’m not sure whether they are related to two separate issues.

 

The wall thickness design is consistent from top to bottom. The only change is the filleted grove within the wall thickness.

 

I’d be interested in any suggestions I can try that may help me resolve the issue. I have also attached the profile I used to help isolate any config issues.

 

Thanks in advance.

0.16 Profile for review.curaprofile

[gr5 2,172]

The gap is some kind of underextrusion and because you show the "crowded" layers above the gap that tells me a lot!

 

Most likely the bed kind of "fell" suddenly (is it a printer where the bed moves?  Or the nozzle?  what kind of printer is it?) which is why you got that gap - an underextruded layer.  Then the bed to nozzle distance moves too small an amount for several layers and you get overextruding (what you called "crowding") for a few layers until things are caught up or back to normal.

 

If you have some kind of Z screw (or screws) moving the bed up and down then that would make sense for this error.  Try cleaning the Z screw.  Usually they are triple helix so get all the threads.  Concentrate on the height where this happened.

[gr5 2,172]

You could try putting a brick or something on the bed so that it moves down more consistently (again I'm guessing this printer moves the bed up and down and not the nozzle).  But usually the proper fix is to clean the z screw.

[Lawzy 0]

Thanks gr5.

 

The printer is an Ender 3 and the Z axis moves in one progressive direction, up. The nozzle is then moving on the X and Y axis.

 

Just to clarify the image 2340 is a profile picture (of the vertical) where the slot or grove ends openly. But, it does show the crowding or over extrusion very well.

 

I will check the Z axis and clean the screw, but my take from your observation is that there is likely an over extrusion problem I need to address. Is that correct? If you have any suggestions where to start the process of elimination in the Cura profile, that would be fantastic.

[gr5 2,172]

Are the two problems near each other?  I think the Z movement is causing both problems.  If it moves too far you get the gap, if it moves too small you get the overextrusion.

 

Overextrusion is the most rare of issues in 3d printing.  Not much can cause that.

 

Wait - I looked at a photo of the ender 3 and the nozzle is moving up and down in Z - not the bed.  Z is vertical.  Maybe you thought I meant Y.

 

So I don't understand.  How could the nozzle move too far upwards suddenly?  Maybe dirt could do this on the Z screw?

 

Is this PLA?  I've seen layers that get this gap but only in higher temp materials like ABS, PETG, Nylon, PC.  Never in PLA.

 

[Lawzy 0]

Sorry gr5. The Z axis moves the nozzle up, the Y axis moved the bed horizontally and the X axis move the nozzle horizontally. And, it is PLA.

 

So you are thinking a good clean and reset of the Z axis screw is the best place to start?

[gr5 2,172]

I'd do a quick clean with a paper towel.  Have one person slide the cross bar up and down and the other stick the paper towel into each thread (remember triple helix).  Use a long thumbnail or something to get the paper towel in there.

 

However I think the issue is probably something else.  Maybe there was a filament tangle.  But then wasn't the overextrusion on the very next layers?  If so then it's probably Z.

[Lawzy 0]

Thanks gr5. I'll give that a go over the next few days and then print that section again. I'll update with a post once done.

[Lawzy 0]

I cleaned the Z screw and tried various layer heights. The issue only occurred with the 0.16 height, not 0.12 or 0.20. I could see ‘squashed’ layers in the 0.12 Cura views. It wasn’t in the others. I’ve no idea why that would be?

 

I did note another small surface artifact this time. Does anyone know of a likely cause? See the diagonal pattern, it’s on all faces. 

[gr5 2,172]

That diagonal pattern can have a few causes. 

 

1) First to check is print through from infill.  Look at the part in Cura and see if those lines are over where the infill joins the part.

2) Second to check is stepper issues but those wouldn't be diagonal unless your wall on that cube wasn't vertical.  Is it possible the wall tilted out a bit?  And was the cube rotated on the bed a little bit also?  If so then we can talk about how to fix this.

 

I'm betting it's #1.

 

[gr5 2,172]

Oh - to fix #1 you can print the walls *before* the infill.  Or you can probably just print the outer wall first.  Both are possible to do in Cura settings.