Printer stops extruding mid print  

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timo.c
(@timo-c)
Active Member

Hi guys, I hope to find help here.

I recently got my i3 MK3S (already assembled, not the kit version) and the MMU2S.
As you might guess I did a Banshee and some other test print which came out fine (see picture 1).
After assembling the MMU I had some common problems but got most of them worked out.
A couple of more or less successfull prints later I ran into my current problem which is that the printer at some point in the print stops extruding and grinds away the fillament inside the extruder as well as making a clicking noise.
A little bit problematic for testing is the fact that I use the Banshee which came on the SD card but always fail 60+ minutes into the print (see picture 2) so maybe you know a better gcode file to debug my problem.
The material I use is the Silver PLA from Prusa which came with the printer and I got some spools of PETG from DasFilament which I didn't dare to test right now but I could if suggested.
Here is as list of things I tried to combat this problem:
-loading automaticaly and/or manualy results in a smooth stream of fillament extruding
-fastening and loosening the screw on the left side of the extruder which tightens the gear (because of the clicking noise)
-cleaning the above mentionend gears which filled with PLA powder because of grinding
-raising the temperature up to 240° or lowering to around 200°
-oozing the nozzle and cleaning it with the needle looked clear

I as well tried a cold pull and the result to me looks clean (see picture 3). For comparison I also added a picture of the filament which I pulled out of the extruder directly after canceling the failed print (see picture 4).
Another small problem I noticed is at the back of the Banshee which was already present in the very first print but got visually worse over time.
Probably it is just a little bit of underextrusion but I didn't try to fix it before my other problem is done but maybe you guys have a tip for me on that as well (see picture 5).

Since this is my first 3D printer I hope you can forgive any unclear descriptions, redundant or missing information I gave.
Thanks in advance for reading through all of this and hopefully you can help me fix my problem(s).

Regards,
Timo

First Banshee
Picture 1: First Banshee

 

Failed Banshee
Picture 2: Failed Banshee

 

Cold Pull
Picture 3: Cold pull end

 

Unloaded filament after failed print
Picture 4: Unloaded filament after failed print

 

Underextrusion maybe
Picture 5: Minor mistakes, maybe underextrucsion?

Posted : 07/06/2019 6:06 pm
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(@-2)
Illustrious Member

Cold pull looks normal, though the cone looks a bit sharp for a standard E3D-V6 nozzle.  Did you change the 0.4mm nozzle out for something else?   Also - do I understand the printer was completing prints when the MMU was NOT connected; but once connected prints started failing?

I have no MMU experience, so here are a couple common and generic causes of jams:

The jammed end looks suspiciously like what I saw when I was having jams related to the heat break.  If you have calipers, measure the bulged area diameter? 2.2 mm is a suspicious number.  Raising print temps can help this issue, but doesn't fix all situations.

I see you already tried printing a tad bit hotter... you might want to run a PID calibration, it can help nozzle temp stability.  

And you've also tried adjusting idler tension...  and it's a prebuild, so common misconnections are unlikely.

Hopefully someone with more MMU experience will chime in.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 08/06/2019 2:16 pm
timo.c
(@timo-c)
Active Member

Thanks for your suggestions.
The nozzle is stock and I haven't touched it.
Yeah the printer completed prints before the MMU was connected, but as well afterwards.
I managed to print a tolerance gauge, some heat towers and stringing test, as well as some Pokemon figurines (~1 hour print) and a larger one which took ~12 hours but had a simple geomtry. The first jams happend when I tried to print at 0.1mm layer hight for the first time and it got worse over time.

Going up in temperatures results in stringing, which isn't that bad but still not consistent enough to finish every print...
This morning I discovered that the IR sensor wasn't picking up every time and I fixed it so now I'm printing another banshee with skipping the MMU (directly feeding into the extruder).

Another interresting fact is that loading with the MMU results in a clicking noise at the extruder while manually feeding doesn't.
That kind of buggs me because the tension seems alright while manually feeding.

Sadly I got no calipers at hand but with a ruler it looks like 2mm or 2.1mm to me.

Posted : 08/06/2019 3:16 pm
timo.c
(@timo-c)
Active Member

Well i can't edit my latest post or I'm too dumb to find it...
Anyways the print already passed the critical area so whish me luck thats it.
I will keep you updated but so far it looks like checking the IR sensor has fixed my problem.

Posted : 08/06/2019 4:45 pm
timo.c
(@timo-c)
Active Member

PS another time not possible to edit..

Next I will hook up the MMU again and test another theorie of mine which is that maybe the MMU locks the filament in place which would result in filament grind inside the extruder.

Posted : 08/06/2019 4:52 pm
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(@-2)
Illustrious Member

Forum times out in about the precise time it takes for you to realize you need to edit. 

It is sounding like something in the MMU is adding friction when it shouldn't.  Might try pushing and pulling the strand that is hanging out when the MMU is disconnected. Or manually feed filament through the path and try pushing and pulling.  I'd think filament should move freely when the spool is selected. 

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 08/06/2019 5:32 pm
timo.c
(@timo-c)
Active Member

I just finished my second print successfully. The first one was without the MMU the second one with the MMU.
Looks like the IR sensor was the cause of all the problems..
Now there is a little bit more stringing involved in both prints then before all the jamming.
As well there still is this weird artifact at the back of the banshee that wasn't present in my very first banshee.
Any guess where it came from?

Finished with MMU
Stringing which wasn't present before, see opening post pictures.

Weird artifacts
Weird artifacts at the back of the banshee

Posted : 08/06/2019 7:23 pm
timo.c
(@timo-c)
Active Member

Damn why is there an edit countdown? I just finished editing and it didn't save...
I wanted to add that the mentioned problem in the last picture were already in my very first banshee but it wasn't that obvious.

Posted : 08/06/2019 7:37 pm
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(@-2)
Illustrious Member

You may need to play with retraction/z-lift settings to optimize for your specific MMU build.  Also, there are some seam adjustments in Plicer - they add or remove material when joining seams - and the stern defects of your Benchy is where seams are happening.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 08/06/2019 10:22 pm
timo.c
(@timo-c)
Active Member

You are right, retraction and z-lift settings are things to tinker with.

Do you mean the overlap setting for infill/contour which is at 25% standard?
If so why did the seam underextrusion became greater without me changing this value in the first place? Anyway I will try to experiment with that value, thanks in advance!

Posted : 09/06/2019 1:15 pm
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(@-2)
Illustrious Member

Can't say definitively why they changed: but I can guess the profile for the MK3S sans MMU is different than the one with MMU.  

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 09/06/2019 7:30 pm
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