MK3 Extruder Skipping  

Re: MK3 Extruder Skipping

Hi,

I am having the same issue. Tried almost everything you mentioned but nothing helped. The extruder starts skipping and the print fails.
What I noticed is that if the printer is turned off, so everything is nice and cool, then the print goes without skipping for some time but eventually, the skipping occurs. I fix the skipping by unloading and reloading the filament and start the print again, but now the skipping reoccurs much faster, sometimes almost immediately. The extruder motor gets very hot. Can be this somehow connected to the skipping?

If you find any solution or if you contact Prusa support post their response/solution.

Thanks

Re: MK3 Extruder Skipping

Wow, thank you for posting this. This seems like the same issue I am experiencing. Sometimes the skipping resolves itself quickly and doesn't ruin the print, but I have had several long prints fail because of this. I have seen this happen early on in a long print and the resolve itself and then happen worse later in the same print. I did not see this issue with the Prusament filament they sent with my MK3, but am seeing it with the Makerbot filament (True black) that was brand new sealed when I opened it. I was thinking the clicking was the motor being unable to move filament, so it seemed like a jam, but I didn't think it could recover from a jam. I have also watched the extruder motor not move at for long periods of time during this issue. This has all been PLA, printing at 215/65 first layer then 210/65. Pausing, unloading and loading gets filament flowing again, but usually it has skipped too many layers to recover the print.

Re: MK3 Extruder Skipping

I have been experimenting with two changes, aimed at reducing the temperature both at the top and the bottom of the extruder.

The temperature at the top, the motor itself, reached over 55C for me. Some have reported that there motors never get hot to the touch. Others, like me, experience temperatures that are painful to prolonged touch.

At the bottom, the nozzle/throat/heatsink assembly, if the fan can't keep the throat cool then heat rises up the throat and can cause the filament to soften and bulge inside the PTFE tube.

So filament is being assaulted by heat creeping in from both ends inside the extruder assembly, and I think this is the cause of most of my problems. I have addressed both individually, but until this week, never together. This week I made two modifications simultaneously:

1) I placed M911 and M912 commands in the gcode to reduce motor current. I'll include details below.
2) Fitted a much more powerful 12V 40x40x20mm fan in place of the tiny 5V one cooling the extruder throat. I had to design and print an adapter to fit the larger fan. I'll provide the STL if anyone's interested.

The results are promising, but I wouldn't say just yet whether my problems are solved. For 90% of my PLA filaments, problems seem to have gone. I've made several many-hour prints without failure, except for Prusa white PLA. That's right, I can't make Prusa's own filament work in this accursed machine. Prusa black, silver, orange, blue PLA etc all seem fine, but white jams almost immediately - 3 brand new spools, all failing quickly. Maybe there was a bad batch of white. Other brands of white PLA - eSun and Sunlu, work just fine now.

The gcode I have tried in my prolog is:
M911 E24; Extruder motor holding current
M912 E24; Extruder motor running current

The default setting (if I have interpreted the source code for v3.4.1 correctly) is E30. I don't know what 30 or 24 mean in terms of actual current in the windings, but new values of 24 have worked just fine, and the motor is much cooler to the touch. The reduced torque doesn't seem to have caused any trouble.

Neither of these changes on their own made any significant improvement for me, but together they are letting me finally get some large prints done. It seems to me that heat management in the MK3 is causing problems, but I can't explain why some people are having no problems, while others are tearing their hair out with this.

As a final note, that the white Prusa PLA can be used in my other Tronxy printer without jamming, but the print quality is terrible - I'm sure I just got a bad batch.

Re: MK3 Extruder Skipping

I converted my 2S to a 2.5 and no problem until a few days ago. I noted that although the printer kept going, the filament stopped extruding and the motor was doing clicks (indicator showed it was not moving - slight forward with immediate click back). If I paused print and unloaded filament then reload filament it starts working OK again. May or may not repeat problem before print is finished. If I leave it alone it will finally start extruding again. I have used the same filament(s) multiple times with no problem. I changed out the nozzle, adjusted the screws to the extruder, tried printing at 125%, changed nozzle temp for PLA down to 200 degrees, all to no avail. When I unload the filament the gear marks are OK (don't show grinding), the end show a small (.5mm) bulge for about 3mm length but it un http://shop.prusa3d.com/forum#_ga=2.234379415.889601021.1544488802-1840356923.1544488802loads OK. looks like it just sat there under heat ad bulged (still has gear marks). I will say I am doing 9 hour prints but this starts at various times as soon as the second layer and as late as 4th layer, or not at all. I was trying to print some gifts for my Christmas cards but am at all stop until I can resolve this problem.

I would add that since I did the firmware and software updates this summer, my printer does the first PLA layer at 215/215 degrees but then the temp goes 200/210 degrees for different amount of layers. The tech support said reduce the fan speed and that usually works but a person should not have to do that. Actually printing PLA at 200 degrees is not a problem but not the right answer. I don't think the two problems are related.

Re: MK3 Extruder Skipping

Add my brand new MK3 that worked perfectly for awhile to the list of machines having this extruder skipping issue.

I built mine from the kit and it worked perfectly for about the first 15 hours until it suffered the same issues described on this thread. I turned off the filament sensor hoping that was the culprit but it made no difference. For me this is completely repeatable using this print https://www.thingiverse.com/thing:3280630 .

This model was sliced using Slic3rPE, default MK3 settings (except bed temp is 50, not 60) and using PRUSAMENT red filament. From my perspective it doesn't seem like a gear drive or temperature issue because the test strip it first puts down, which uses two extruder speeds, is perfect. It seems like the issue is it's being commanded incorrectly (which is why I tried turning the filament sensor off). Perhaps the slicer has some issues? Or printer firmware?

After the test strip it proceeds to the skirt and there the extruder skips/clicks and for a short length nothing is extruded, making the skirt incomplete. Where there is a line it's "blobby", not smooth and linear. As it goes to do the outside perimeter of the model the filament is flowing but it's "blobby" again. Subsequently the fill looks "okay" but not as smooth and linear as expected. After this first layer it goes on to print just fine - no more skipping and the quality is as expected. The rest of the print is perfect.

I might add, although I can't conceive of this being a factor, that all this started exactly when I switch to printing on my new SMOOTH removable plate. Up until now I have been printing on the TEXTURED plate. Just an observation.

Some of these threads are from awhile ago - has anyone cracked the code on this issue?

Re: MK3 Extruder Skipping

Have you tried changing the nozzle. I had the same issue , tried everything you´d mentioned before. I changed the nozzle as a last resource, and it worked for me. With the time , nozzles gets dirty inside and make difficult to extrude well, needing more power from the motor to inject the filament.
I hope this solve your problem.
Regards,

Re: MK3 Extruder Skipping

I have not tried that yet but certainly will. However even if that's it - it's still an issue. I haven't more than 15 hours of printing on this MK3; in comparison I have hundreds of hours on my MK2 and I've never done anything to it. Something isn't working right if you have to change the nozzle every 15 hours!

Thanks for the tip tho, when I get around to trying it I'll post.

Re: MK3 Extruder Skipping

I have had this problem on my new MK3 with the “silver” Prusa PLA filament multiple times, but not on the Inland PLA filament. It is intermittant on long (several hour) prints. According to the Prusa manual, it is supposed to detect stuck/non moving filament. Is this setting automatic, or do we have to “enable” it?

I print PLA at 200F on my Lulzbot. Maybe we are printing at too high a temp.

Re: MK3 Extruder Skipping

I have not tried that yet but certainly will. However even if that's it - it's still an issue. I haven't more than 15 hours of printing on this MK3; in comparison I have hundreds of hours on my MK2 and I've never done anything to it. Something isn't working right if you have to change the nozzle every 15 hours!

Thanks for the tip tho, when I get around to trying it I'll post.

Then , I think that it is not because the nozzle, you are rigth, but test does not come bad. Maybe you had bad lucky.
Also, did you greased (a little) all the gears in the idler box? And try tightening considerably both of the screws of the idler box, this helped me too.

Re: MK3 Extruder Skipping

I have had this problem on my new MK3 with the “silver” Prusa PLA filament multiple times, but not on the Inland PLA filament. It is intermittant on long (several hour) prints. According to the Prusa manual, it is supposed to detect stuck/non moving filament. Is this setting automatic, or do we have to “enable” it?

I print PLA at 200F on my Lulzbot. Maybe we are printing at too high a temp.

That option would be enable, but if not, you can check it in the LCD menu going to "Settings" and "Fil. sensor"
But are you printing in 200°Farenheit or Celsius? There is a big difference

Re: MK3 Extruder Skipping

Hey all, no more extruder skipping and my printer is working again after doing 2 things:

1) Replacing the 0.4 nozzle with a brand new one.
2) Recalibrating the printer with the flat steel sheet.

I suspect it was #2 that solved the issue. When I assembled the printer I originally had calibrated it to the textured sheet. My printer printed beautifully until I swapped out the textured sheet for the smooth steel sheet, which is when I immediately started having extruder skip issues. I never read anywhere that it needed to be recalibrated so I never considered that might be the issue.

My theory in replacing the nozzle (#1) was that I had printed PETG previously, which prints at a higher temperature than PLA. When I loaded PLA I heated the nozzle to PLA temps to do the filament change. I thought maybe there was still some PETG residue in the nozzle that was not melting and clearing out and possibly causing a jam. I don't think this is the case as the test strip (before every print) prints perfectly, and after the first layer the print was perfect however I'll be able to verify it by placing the original nozzle back on.

So I'm guessing the printer needs to be calibrated when changing the type of steel sheet? Did I miss that in the manual somewhere? Has anyone swapped steel sheet types without calibrating and printed successfully?

Re: MK3 Extruder Skipping

Also had the same issue: filament jamming just below the extruder motor gears, probably because it was heated by the hot extruder motor. Lowered the current with the M911/912 settings to 24, and raised the nozzle temperature to 230°C (PLA). That solved the issue, at least so far!
Thanks for the tips!

NB. Maybe it is worth mentioning that the issue was more common with a white PLA (eryone) than with a silver PLA (prusa).
I would be interested in having some insight as to if and why the color may make a difference.

Re: MK3 Extruder Skipping

Hey all, no more extruder skipping and my printer is working again after doing 2 things:

1) Replacing the 0.4 nozzle with a brand new one.
2) Recalibrating the printer with the flat steel sheet.

I suspect it was #2 that solved the issue. When I assembled the printer I originally had calibrated it to the textured sheet. My printer printed beautifully until I swapped out the textured sheet for the smooth steel sheet, which is when I immediately started having extruder skip issues. I never read anywhere that it needed to be recalibrated so I never considered that might be the issue.

My theory in replacing the nozzle (#1) was that I had printed PETG previously, which prints at a higher temperature than PLA. When I loaded PLA I heated the nozzle to PLA temps to do the filament change. I thought maybe there was still some PETG residue in the nozzle that was not melting and clearing out and possibly causing a jam. I don't think this is the case as the test strip (before every print) prints perfectly, and after the first layer the print was perfect however I'll be able to verify it by placing the original nozzle back on.

So I'm guessing the printer needs to be calibrated when changing the type of steel sheet? Did I miss that in the manual somewhere? Has anyone swapped steel sheet types without calibrating and printed successfully?

Recalibrating the printer with a different steel sheet wouldn´t solve the problem, maybe it helped. Changing the nozzle indeed solved the problem. As i told you, i did the same thing and it solved it too. Mark the topic as answered.
Regards,

Re: MK3 Extruder Skipping

I'm having this issue now. I recently purchased a second MK3 and when I got it up and running I printed the extruder and fan upgrade with the intention of upgrading my previous MK3 (which was printing fine but I figured the better cooling would help me with a tiny issue I was having with "hairy prints".)

I pull the the extruder apart, cleaned everything up, greased the bondtech gears as the idler was coming back together, replaced the PTFE tube on the hot end and replaced the nozzle then reassembled and calibrated it.The XYZ calibration passed muster but when I set the first layer calibration going.... it ran the purge line fine but when it started the portion of printing a line it started skipping and no plastic was extruded. I've tried a cold pull, tinkered with the idler tension for several hours. it now skips when loading the filament and will not extrude plastic for first layer calibration. Before I pull teh extruder back apart I figured id ask here for suggestions I may not have tried yet.

Thoughts?

Re: MK3 Extruder Skipping

Ashley,

It wasn't clear when or how your skipping started; was it printing correctly after you assembled it? If so, what (if anything) triggered the change to the extruder skipping? Also, did you print different filament types - specifically higher temp filaments and did you happen to change the steel sheet type from textured to smooth or vice versa?

As mentioned above I did 2 things at once (nozzle replacement and re-calibration) and the problem was solved. (My skipping extruder issue began with changing the type of bed plate from the textured to the smooth). Alejo suggests it was the nozzle change that fixed it - if you have a spare nozzle lying around I would replace it with a new one (remember to do that while heated) and re-calibrate.

Regarding "hairy" or stingy prints one thing worth repeating is to make sure you are printing at the right temperature. I've know people printing Hatchbox PLA at 215 (default temp) when the filament calls for 180-210. It's easy enough to experiment with varying temperatures during a print.

Re: MK3 Extruder Skipping

The extruder skipping began when I upgraded the extruder to the current version with the improved cooling config. I printed the new parts in Prusa Black PET on my new MK3 and used them to upgrade the extruder on my older MK3. so ..when I finished assembling the extruder upgrade on the older MK3, I calibrated it...and went on to do a first layer height configuration after I loaded the PLA. It skipped a little when I loaded the filament....it printed the purge line and when it started to print the layer height line the skipping was constant and it would no longer extrude material at all. I have not printed anything higher temp than PLA just before or after the extruder upgrade although I have printed PET and ABS on it before (maybe 2 months ago).....it was printing fine (with a bit of hair) prior to the upgrade however.

I do use Hatchbox PLA a lot but usually print the first layer at 205 and the rest at 200. The hairy prints began out of the blue about 3 weeks ago. I did a print that was fine... and the next print looked like a chia pet and have been hairy ever since. ive played with the retraction settings and it got a little better it never went away. Since the extruder upgrade Ive not been able to get pass the layer height calibration due to the skipping issue so I cant say if the upgrade made any differance.

Re: MK3 Extruder Skipping

If changing the nozzle didn´t work for you, i would try over thightening both screws of the idler box and see if that helps a little.

Re: MK3 Extruder Skipping

Over tightening the idler tension screws did not help. The skipping continues. This thing was printing fine prior to the extruder upgrade so its obviously being caused by something I've done...ill be pulling the extruder apart today to triple check everything.

Re: MK3 Extruder Skipping

[...] I printed the new parts in Prusa Black PET on my new MK3 and used them to upgrade the extruder on my older MK3. so ..when I finished assembling the extruder upgrade on the older MK3, I calibrated it...and went on to do a first layer height configuration after I loaded the PLA.

If you are switching directly from a high temp material (PET) to a low temp material (PLA), there's a good chance some of the high temp material is left in the nozzle and/or hotend. When you load the new low temp material, the hotend doesn't get hot enough to force the leftover crud out, so you get skips and jams.

When going from high temp to low temp, I always do the following:

The beauty of the cleaning filament (I use eSun's) is that it will melt and extrude at a very wide range of temps, so if any is left in the hotend after doing a cold pull, it will melt out at PLA temps, unlike PETG, ABS etc.

Only after I've fully purged the higher-temp material do I bother trying to print with lower temps. It sounds like you'd really benefit from doing cold pulls. If you previously replaced a nozzle, try reinstalling the old nozzle and doing a cold pull to see if it's restored.

Starting out, I had a couple of nozzles that seemed hopelessly clogged, so I set them aside. A few months later, having gained some experience, I re-mounted them and did some cold pulls and they're fine now. Nozzles aren't expensive, so a premature swap is not a big deal, but you don't need to toss one every time you have jam.