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KindlyDragon
(@kindlydragon)
Active Member
Extruder skipping

I am having an issue printing with a spool of black Prusament, and I am not completely sure what the problem is.

After some time of printing, the extruder motor begins to make audible clunks and plastic extrusion becomes unreliable enough that the resulting print will be a flimsy and brittle mess that falls apart at the seams.

 

I am not totally certain what is causing this. I've tried changing the tension on the idler screw and increasing temperatures as high as 240°C without any change in behavior.

The odd part is that this does not happen during raft printing (this particular 3D model needs it due to dimensions and support design, I have it set to three layers which have all come out flawlessly so far) or anywhere else except when the actual print begins. I have my suspicions that my problem is with the retraction motion, but I also wonder if maybe the motor is failing and begins to skip after it has reached operating temperatures.

How best to troubleshoot this? Is there a way I can command the extruder motor to spin continuously for a period of time, in either direction, to watch how it behaves and narrow down my problem? Reaching the gears enough to spin it manually is difficult and I don't aim to take it apart just to discover that the motor isn't my problem...so any ideas?

Info: 

Printer: MK3S

Firmware version: unavailable at the moment but can retrieve at any time

Material: Prusament black, print attempts at temperatures between 210-240°C

 

Best Answer by KindlyDragon:

Okay! Sorry for the delay, but I think I figured it out. It looks like I was experiencing a combination of PLA crystallization and thus clogging printing primarily at 215 degrees on the 0.07mm profile. I initially didn't catch this fast enough, so before long I had a complete and full clog that wouldn't move no matter what temperature I placed the nozzle at.

I've since cleared the clog, restarted my print, and, when the noise of the extruder skipping began to return I simply increased my temperature to 240 degrees before the problem was too far gone like before. As soon as the temperature increased past around 230 my printing returned to being smooth as ever. I can probably get away with 230 degrees but this particular print has been so troublesome I don't want to risk it.

Keep this in mind when printing slow speeds with PLA everyone! Some plastics of this type will change properties if kept at a temperature point just below melting for too long(Like the environment in the extruder assembly just before the plastic hits the nozzle, it is pretty warm in there), thus "baking" a crystalline structure into it that sometimes can vastly increase its resistance to melting and thus increase the temperature necessary to print smoothly. ProtoPasta's HTPLA is particularly severely affected by this property, it being one of the first PLA/PLA-like plastics I encountered this on. 

This topic was modified 2 years ago 2 times by KindlyDragon
Posted : 11/01/2020 9:48 am
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Extruder skipping

You can control this via the LCD menu. The firmware version can also be seen there. The best thing to do is to take a look at the Prusa manual, as a lot is described very precisely:

https://www.prusa3d.com/downloads/manual/prusa3d_manual_mk3_en.pdf

 

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 11/01/2020 10:03 pm
KindlyDragon
(@kindlydragon)
Active Member
Topic starter answered:
RE: Extruder skipping

Okay! Sorry for the delay, but I think I figured it out. It looks like I was experiencing a combination of PLA crystallization and thus clogging printing primarily at 215 degrees on the 0.07mm profile. I initially didn't catch this fast enough, so before long I had a complete and full clog that wouldn't move no matter what temperature I placed the nozzle at.

I've since cleared the clog, restarted my print, and, when the noise of the extruder skipping began to return I simply increased my temperature to 240 degrees before the problem was too far gone like before. As soon as the temperature increased past around 230 my printing returned to being smooth as ever. I can probably get away with 230 degrees but this particular print has been so troublesome I don't want to risk it.

Keep this in mind when printing slow speeds with PLA everyone! Some plastics of this type will change properties if kept at a temperature point just below melting for too long(Like the environment in the extruder assembly just before the plastic hits the nozzle, it is pretty warm in there), thus "baking" a crystalline structure into it that sometimes can vastly increase its resistance to melting and thus increase the temperature necessary to print smoothly. ProtoPasta's HTPLA is particularly severely affected by this property, it being one of the first PLA/PLA-like plastics I encountered this on. 

This post was modified 2 years ago 2 times by KindlyDragon
Posted : 20/01/2020 10:18 pm
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