Cura bug? Extruder skip from infill going over and over itself multiple times

[rat_tech 0]

I'm running into an issue with my Ender 3 having extruder skipping.

 

I've had extruder skipping before but only on the first layer due to leveling the bed to close to the nozzle.

 

However I'm getting this issue later on in the print. A good few layers later, in the same place each time. So its not bed level related. 

In this example I'm printing something like a thread bobbin, like a cylinder. So nothing crazy.

 

And its only happening during certain parts of a certain print.

 

I was printing with this exact same setup just a few days, and have been printing this way for years with no issue. 

 

Petg 225'c

50mms (I turned down the speed mid print to 20% but it still skips, so not speed related)

It's not during the first layer, so bed spacing is fine.

Nozzle isn't clogged

Bowden is secure

Extruder gear is fine.

Filament is fine and not chewed up.

Spool rotates freely it's on a ball bearing mount

I tried turning down flow rate to 80% mid print on the parts its skipping on and it continues to skip but less frequently.

It does it on both cura 5.2 and 5.3.1

THE PROBLEM: As you can see from the G-code in cura / the video below. It prints the first 4 layers no issue. The skipping issue starts on layer 5, the outer walls and inner walls print fine, then there are these thin bits of infil which are spaced slightly inwards from the wall. And as you can see the nozzle goes over and over the same spot multiple times, and this is where the extruder starts skipping. Which is why I think its blocking the nozzle and causing extruder skipping. The issue then stops and prints the green/red lines fine, and then restarts again on layer 6 when it goes to the infill part again.

Heres the video, look at the orange lines (infil)

 The gcode is attached if you want to look at it yourself.

I've tried other infil patterns and a similar thing is happening, the inner infil goes over themselves multiple times.

Thoughts?

notfixedbobbin.gcode

[DivingDuck 104]

PETG with 225°C is quite low. No wonder that your extruder skips. Is this really the manufacturer recommendation?

PETG is usually in a range form 230 to 250 °C. Try the middle of what the manufacturer recommend, this is usually a good starting point.

[GregValiant 1,245]

I just saw this.

I don't know @DivingDuck, the nozzle should not be re-extruding where it's already been.  This looks like it might be a bug.

I don't understand the pattern though.  It's lightning infill but that outer area makes it look like concentric.

 

@rat_tech I know some time has passed but could you load that model, re-create your Cura settings, and then use the "File |Save Project" command and post the 3mf file here?  It may provide a clue as to what is going on.

[rat_tech 0]

On 6/1/2023 at 7:49 PM, GregValiant said:

I just saw this.

I don't know @DivingDuck, the nozzle should not be re-extruding where it's already been.  This looks like it might be a bug.

I don't understand the pattern though.  It's lightning infill but that outer area makes it look like concentric.

 

@rat_tech I know some time has passed but could you load that model, re-create your Cura settings, and then use the "File |Save Project" command and post the 3mf file here?  It may provide a clue as to what is going on.

Hi Thanks for replying. I've attached the 3mf file.

Also this happens on every infill pattern I've tried so far, lines, grid, triangles.

 

Also attached my infill settings

 

Model was created using fusion360 with medium refinement (Dont think thats relevant as I've never had any issues before)

  

CE3E3V2_belt sander dolly v3.3mf

[GregValiant 1,245]

This is an Edit.

I can duplicate this.  It looks like all of layer 5 is going down twice.  I'd call that a bug.

This is another Edit.

Now I can't get it to do it again.

 

I'm using 5.3.1 for the trial with your settings.  I'll keep playing with this to see if I can repeat the problem.

Edited June 2, 2023 by GregValiant

[rat_tech 0]

I've attached my cura profile if that helps

ratt bug profile.curaprofile

[GregValiant 1,245]

That was it.  It's in that profile.

This type of bug has come up a couple times recently in regards to "Remove Empty First Layers".

I have written a couple of post-processors and one of them adds the Cura settings to the gcode.  I used it and saw that "Infill Line Multiplier" was set to "2".  Just to check I went to change it and low and behold it wasn't visible because it is never visible when "Gradual Infill Steps" > 0.

So I set Gradual Infill Steps to 0, set the Infill Line Multiplier to 1, set the Gradual Infill Steps back to 10 and the problem went away.

So like the "Remove Empty First Layers" bug we have a hidden setting that is being referenced and used.

This is not an exact duplicate of the other reports but it is the same sort of behavior.  Github bug report #14989 has been closed as the Cura team worked on that bug.

 

@MariMakes I think this one is very similar.  Should the OP fill out a bug report on GitHub?

Edited June 3, 2023 by GregValiant

[rat_tech 0]

22 hours ago, GregValiant said:

That was it.  It's in that profile.

This type of bug has come up a couple times recently in regards to "Remove Empty First Layers".

I have written a couple of post-processors and one of them adds the Cura settings to the gcode.  I used it and saw that "Infill Line Multiplier" was set to "2".  Just to check I went to change it and low and behold it wasn't visible because it is never visible when "Gradual Infill Steps" > 0.

So I set Gradual Infill Steps to 0, set the Infill Line Multiplier to 1, set the Gradual Infill Steps back to 10 and the problem went away.

So like the "Remove Empty First Layers" bug we have a hidden setting that is being referenced and used.

This is not an exact duplicate of the other reports but it is the same sort of behavior.  Github bug report #14989 has been closed as the Cura team worked on that bug.

 

@MariMakes I think this one is very similar.  Should the OP fill out a bug report on GitHub?

Well spotted, I didnt realise that infill steps and infil line multiplier should normally be mutually exclusive.

For anyone reading; it appears this bug was allowing me to edit gradual infill steps AND infill line multiplier at the same time, when normally editing 1 of those settings would hide the other setting.

[GregValiant 1,245]

This is one of those things that's more like a "missed trick" in cards than a bug.  It's an omission.  Since the setting "Infill Line Multiplier" get hidden when "Gradual Infill Steps" > 0 then when a user makes a change in that - it should not just hide "Infill Line Multiplier" but set it to "1" as well.