Extruder motor skipping  

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piotr.k3
(@piotr-k3)
Active Member

Hi guys,

Having a big issue with my prusa recently. It worked fine for couple of years (bought MK2 originally, upgraded to 2.5 and 2.5S). Recently I started having issues with extruder motor not being able to push the filament, just keeps 'clicking' and the print fails.

I did a reading about this but nothing seems to work. Increased the temp to 280C for few minutes to get rid of any plastic in the nozzle. Set the temp to 150C and pushed a white filament to see if there's anything stuck, came out (partially melted so I know it reached the end of nozzle) perfectly clean, not a single bit of black colour (I use mainly black pla in it).

It works fine for the first layer, but with default printing speeds from second layer the skipping starts. I tried to raise the temp up to 220C (normally printing @ 210C) but nothing changed. Slowing it down to like 50% seems to work, but still getting occasional errors. 

I have the latest  fw etc.

Do I need to replace my nozzle? I really need my printer to work well asap so would appreciate any suggestions.

Thanks!

Posted : 01/12/2019 5:15 pm
heinzk
(@heinzk)
Active Member

Out of curiousity, did you very recently upgrade the extruder? I am asking because I noticed a sudden drop in temperature as soon as fan kicked in after the first layer. So starting from 215°C it was supposed to drop to 210°C but in fact dropped down to ~197°C and recovered only after quite a long time. Apparently the latest extruder design causes the hotend to be cooled and not just the printed object. I followed the advice in other threads here in the forum and got myself a silicone sock for the E3D V6 hotend - not problems anymore after that.

Furthermore, did you try pinching through the nozzle with the acupuncture needle that the MK2 was shipped with?

And last but not least (i.e. if the ideas above don't help) during one of my extruder upgrades I was rather careless about the PTFE tube that goes into the heat spreader, in the sense that I did not ensure that it was firmly inserted and stayed there when fixing it with the "ring" (however this ring is really called). That had given me a lot of trouble with a clicking extruder, missing layers and prints failing.

Hope it helps ...

(edit) fixed some typos ...

This post was modified 2 weeks ago 2 times by heinzk
Posted : 01/12/2019 5:45 pm
piotr.k3
(@piotr-k3)
Active Member

@heinzk

Hi, thanks for your suggestions, I do have the temp problem but the thing is I assembled mk2.5s upgrade because of the the extruder skipping issue hoping that after cleaning it etc things will get better. The problem appeared out of nowhere in the middle of 8h print.

I've been using my mk2.5 literally non stop for the last 2mths (taking print out from bed and starting next one) until the skipping problems started 2 days ago. The only thing I didn't do is to take the hotend apart, which seems like I'll have to do... 

This post was modified 2 weeks ago by piotr.k3
Posted : 01/12/2019 6:06 pm
piotr.k3
(@piotr-k3)
Active Member

For some reason can't see an option to edit my post but... 

I will probably buy a replacement e3d hotend just to get it working, I know I need 12v version but is the original bowden or direct? (I'll be buying from amazon uk https://www.amazon.co.uk/dp/B079H32Y6M/ref=cm_sw_r_cp_apa_i_eKa5DbR3RJQ67)  

Posted : 01/12/2019 6:41 pm
joan.t
(@joantabb)
Veteran Member Moderator

I would look at this version... 
https://e3d-online.com/prusahotend

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 01/12/2019 10:46 pm
joan.t
(@joantabb)
Veteran Member Moderator

@piotr-k3

Editing is only available for a short while...  then the option dissapears, this is due to spammers changing the messages after they have been authorised

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 01/12/2019 11:35 pm
piotr.k3
(@piotr-k3)
Active Member

Ok so the problem is solved, here's what I did (for future reference):

Bought E3D V6 Direct 12V hotend directly from E3D. Removed the old hotend and took it apart. I kept the thermistor and heater cartridge cause I didn't want to bother with replacing all the cables etc (also because I got blue 30W version instead of red 40W that's originally in Prusa MK2). After removing heatsink I noticed the thermal compound is not in great shape anymore, additionally the thread between heatbreak and heaterblock looked like corroded  or smt, and lastly my whole heaterblock was covered in plastic (after few failed prints).

Removing the heater cartridge was a bit of a pain, first of all the screw was covered in pla so there was no way to remove it using hex screwdriver, I solved it by filing opposite sides of the screw and when I got it flat enough (took a good 15 min or so to get there) I grabbed it strongly with pliers and managed to loosen the screw.

Next the heater cartridge was stuck 🙂 Tried to remove it while cold but that proved to be impossible, so I heated it to 150C and it went out easily (held it under the fan for 5 min afterwards to cool it down so it doesn't get damaged or smt).

After mounting the new E3D hotend all works perfectly, it also has silicone sock so no problems with MK2.5S fan cooling the heaterblock. Managed to easily print with 150% of default speed with 0.35mm layer height without a single problem.

So what was the problem? I have literally no idea, maybe the whole unit needed just a good clean and new thermal paste. There was no leftover filament inside, so my gut feel is that the heat transition wasn't good enough after being used frequently for almost 2.5 years.

Anyways I'm super happy cause after almost a week of panic I have my dear prusa working again 🙂 Hope my painful experience helps the others solve similar problems.

Happy printing! 

Posted : 03/12/2019 12:35 am
joan.t
(@joantabb)
Veteran Member Moderator

@piotr-k3

Good news, 
did you do a PID calibration?

clean up the bits you have left, add hew ptfe & a sock and block kit from E3d, and you will have a second hot end, ready for the future... 

regards Joan

p.s.   I believe one of the moderators on here (PJR) extolls the virtues of the 30watt heater, saying it gives better control of the melt zone temperature...   

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 03/12/2019 1:20 am
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