Failed prints (retraction issue)

[Mattw924 0]

Hi all, 

 

For the last week or so we've been trying to resolve an issue affecting all prints on two of our UM3's wth PLA. The prints end up very weak & under extruded, when inspecting the filament it is ground down in multiple places. 

 

The only setting i've changed that resolves the issue it turning retractions off. Whilst this does produce the required print, it is very stringy I guess due to dribble from the filament not being partially retracted. 

I have tried changing retraction settings to improve the print, but with no success. Images below show default retraction settings (Max retraction count = 25) and what I had changed to (Max retract count = 4) prior to turning retraction off entirely. Also included are images of the filament, failed print and a completed print with retraction off.

 

Cura SW has last updated January, printer Firmware was done at the same time. 

 

Any advise on how we can resolve this whilst keeping retractions would be massively appreciated. 

 

If I have missed any crucial info, please let me know. Thanks!

 

 

[Smithy 1,145]

What about your feeder tension, is the marker in the middle position?

[Mattw924 0]

@Smithy Feeder tension is in the middle on both machines. We've tested on a looser tension with no change.

[Smithy 1,145]

Thanks, middle position is ok for most materials, so that's not the reason.

 

Can you upload the Cura project (File - Save project) and upload it here, then we have the model and the settings to check it deeply.

[Mattw924 0]

Attached, Cheers.

UM3_AHU mount 2_2 v2.3mf

[Smithy 1,145]

Thanks!

The model slices without problems but there is something wrong with the model.

 

 

When checking in X-ray view, there is some geometry error.

 

I am not sure if this is causing the problem with too many retractions but it was the first issue I found.

 

So I would first try to repair the STL file or get a correct export from your CAD and try it again.

[Mattw924 0]

We've printed this STL multiple times before without issue, so i'm confident that despite the geo error, that is not the root cause. It is something i'll try and get resolved however.

[Smithy 1,145]

Ok, another idea, have you tried a different print core for PLA?

I don't think you have to adjust the retraction settings, I should work out of the box, the model is not very complex so there must be something else.

 

So I am thinking in the direction that the extruder cannot move the filament as it should be. This could be a partly clogged print core, an old Bowden tube or a problem with your middle fan in the print head which cools down the upper part of the hot end.

 

So check first if the middle fan is working when you heat up the print core. It starts automatically when the core is over 50°C. And then try another print core and print it again.

 

Also check your feeder and clean it. 

 

I believe it is more a hardware issue than a software/setting issue, but step by step.....

[Mattw924 0]

Morning @Smithy

 

Not on the machine that's currently getting our attention - but the one the first started displaying this issue had a print core swap which did not resolve the concern. 

 

We're checking over what you've mentioned above today and will get back to you with what we find - the fan is the only thing so far that we haven't looked at, but will be fully removing and stripping feeder to ensure that's spot on & hot/cold pulling the core. 

[Mattw924 0]

We've been rather snowed under since & haven't had a huge amount of time to investigate what's been mentioned, however today we managed to confirm centre fan does operate, engaged at around 45 degrees C.