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Unusual Retraction Causing Under Extrusion  

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RLevy
(@rlevy)
Active Member
Unusual Retraction Causing Under Extrusion

I have searched high and low for someone with a similar issue and can't seem to find anything. I am printing a small and detailed part with a lot of retractions. The retractions work just fine until it's about 90% of the way through the print. At the same point each time the extruder makes a weird noise that sounds as if it's skipping steps. It does this twice within the span of about 5-10 seconds. It then takes about 30 seconds for filament to start extruding out of the nozzle again.

I have paused the print immediately after it happens and set the nozzle temp so I can manually extrude and it extrudes fine indicating it is not a clog. I have modified retraction distance, retraction speed, deretraction speed, and idler tension all to no avail. I have 3 Prusa Mini's, two of them with the stock extruder and Revo micro hotends, and one of them with a revo micro hotend and bondtech IFS extruder for the Mini. All 3 printers have the same issue. I've only had it happen one other time on a different print but it happens every time I try to print this specific part. Any insight would be greatly appreciated!

This topic was modified 3 months ago by RLevy
Posted : 17/02/2024 3:27 pm
RLevy
(@rlevy)
Active Member
Topic starter answered:
RE: Unusual Retraction Causing Under Extrusion

I'm still suffering from this issue if anyone is willing to take a stab at it. Any assistance would be greatly appreciated!

Posted : 23/03/2024 11:26 pm
_KaszpiR_
(@_kaszpir_)
Honorable Member
RE: Unusual Retraction Causing Under Extrusion

Can you share the gcode without breaking NDA contract, or share he model or project (.3mf) ? If yes then you could zip it and attach to the forums, and others could look at it.

See my GitHub and printables.com for some 3d stuff that you may like.

Posted : 24/03/2024 7:53 am
RLevy
(@rlevy)
Active Member
Topic starter answered:
RE: Unusual Retraction Causing Under Extrusion

Thanks for the recommendation! I have attached the file as a .3mf

ProblematicPart_PrusaMini

Posted : 24/03/2024 4:01 pm
mark
 mark
(@mark-3)
Reputable Member
RE: Unusual Retraction Causing Under Extrusion

Did you see all the error messages Prusa Slicer gives about the part being unstable? There is no flat part on the bed, and lots of tiny features, smaller than it can extrude. There are lots of overhangs and you don't have supports. The overhangs are circular so the bottom will be one line in thin air with nothing to support it. An FDM printer cannot print in thin air. It needs a decent amount on the bed, and support for overhangs. For tiny features, there is not much you can do except use a smaller nozzle. I don't know if the printing in thin air is causing your issue. Do you see filament globbing on the hot end?

Basically, that looks unprintable on an FDM printer. Can you cut it in pieces so there are flat parts on the bed and glue it together? That is what I do for parts with features on all sides.

Regards,

Mark

Posted : 25/03/2024 1:11 am
RLevy
(@rlevy)
Active Member
Topic starter answered:
RE: Unusual Retraction Causing Under Extrusion

Hey Mark, thanks for taking a look at it! I believe I misunderstood which .3mf file I was supposed to upload and exported the actual CAD file as a .3mf not the prusa slicer project file. 

I’m printing it with a .25mm nozzle and have it situated flat on the bed with plenty of support. The issues I’ve been having are with retraction at the top of the part. I will upload the correct .3mf when I get home from work today. My apologies for the misunderstanding. 

Thanks again!

Posted : 25/03/2024 11:32 am
mark
 mark
(@mark-3)
Reputable Member
RE: Unusual Retraction Causing Under Extrusion

Yes, we need the project file to see how it is on the bed, and what settings were used.

I have never been able to get good results messing with retractions. It either gets stringy, fuzzy or has a terrible surface finish. There is no right setting as far as I can tell, just a compromise that they have already baked into the default settings.

The adjustments resulting in nice parts for me have been z height, extruder tension, extrusion multiplier and the linear advance calibration as described in this thread:

https://forum.prusa3d.com/forum/input-shaper-mini/under-extrusion-or-gaps-at-seams-with-input-shaper-settings-and-5-x-firmware/

Regards,

Mark

Posted : 25/03/2024 9:38 pm
AstigmaticEye
(@astigmaticeye)
Member
RE: Unusual Retraction Causing Under Extrusion

Hi,

I am having the same issue, last PRUSA support agent said he couldn't hear anything wrong while that same sound was happening and one before him sent me some useless tests that test for resistances of heatbed and so on.

Anyway did you manage to fix your problem?

Posted : 20/04/2024 2:04 pm
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