Mk8 Extruder - filament jams in the throat.

buzmal
Posts: 46
Joined: Wed Feb 11, 2015 8:20 pm

Mk8 Extruder - filament jams in the throat.

Post by buzmal » Tue Sep 22, 2015 6:06 pm

ok so the extruder works.

however the extruder jams and the filament jams in the throat. the motor starts clicking randomly during printing. If i pause the print i can force the filament pass the jam and then the pla flows freely, however the filament will eventually jam again. If i am reverse the extruder 2-3mm it make pushing the filament pas the jam easier.

Has anyone else had this problem and found a fix.

jaitas
Posts: 11
Joined: Mon Aug 24, 2015 12:05 am

Re: Mk8 Extruder - filament jams in the throat.

Post by jaitas » Fri Sep 25, 2015 3:34 pm

Hello

Posting a reply because I have just the same problem with my prusa i3 pro C dual extruder version (I believe that's also Mk8, even though I only have one fan and website lists that extruder with two fans)

So basically extruder randomly jams (probably in the throat section) and starts to either "click" or "shred" the filament.

I can manually release the extruder motor and push a bit past and then it continues normally so there's some sort of clogging in the throat section.

Are there assembly / unassembly instructions for picking the extruder apart and cleaning it.

also it seems that printing nylon isn't so problematic, my initial tests show that nylon doesn't jam to the extruder throat.

Tips & Tricks would be appreciated, at this condition that extruder is unusable :)

Mark
Posts: 1553
Joined: Thu Aug 06, 2015 9:19 am

Re: Mk8 Extruder - filament jams in the throat.

Post by Mark » Mon Sep 28, 2015 1:53 pm

How about slow down the feedrate? Maybe decrease it to 50. Sometimes the nozzle moving fast in a very short distance frequently will cause the problem.

Sherry
Posts: 362
Joined: Wed Jul 01, 2015 12:52 pm

Re: Mk8 Extruder - filament jams in the throat.

Post by Sherry » Thu Oct 01, 2015 7:05 pm

hi,buzmal. how much temperature you set up for extruder?the temperature for pla is 190°-210°.and the gap from nozzle tip to print bed surface is the thickness of an A4 paper.in addition,please see if the filament is place in correct position.it should be along with the groove of the philip screw.

buzmal
Posts: 46
Joined: Wed Feb 11, 2015 8:20 pm

Re: Mk8 Extruder - filament jams in the throat.

Post by buzmal » Thu Oct 01, 2015 8:57 pm

I have done all that. Multiple times. The system works until the filament jams in the throat. The guides are aligned.

osem
Posts: 11
Joined: Sat Apr 25, 2015 11:02 am

Re: Mk8 Extruder - filament jams in the throat.

Post by osem » Sat Oct 10, 2015 10:16 pm

this is very big problem for pla. i had same problem i fixed it now. the geeetechs mk8 nozzle is very bad. change the nozzle with jhead. you need good cooling. other solution is, work with abs.

Bogoframe
Posts: 2
Joined: Tue Jan 19, 2016 6:03 pm

Re: Mk8 Extruder - filament jams in the throat.

Post by Bogoframe » Tue Apr 19, 2016 10:56 pm

I also have this issue, but it only occured after quite a while, and quite some meters of filament.

I replaced the nozzle with different makes and models, both brass and copper, both 0,3mm and 0,4mm
I replaced the FTFE-tube inside the throat
I experimented with different heat settings, extruder speeds, cooling the throat with a fan...

None of this works for a prolonged period of time.

When I consider the EVD Mk6, I see that the throat is colled by this huge cooling cylinder, with a fan direcetly attached to it. So that seems to be a good idea.

If that isn't the issue, the only thing I can think of is that there is an issue with a small gap between the rear end of the nozzle and the front end of the the throat, allowing molten filament to collect there and then thicken the end of the solid part of the Filament, causing the blockage.

Any ideas on that, anyone?

snowman
Posts: 5
Joined: Fri Mar 25, 2016 11:02 pm

Re: Mk8 Extruder - filament jams in the throat.

Post by snowman » Mon Apr 25, 2016 8:23 am

I found that by disassembling mine, and turning the bolt with the teflon liner end for end, so the end with teflon flush at the end mated to extruder tip, there was no cavity for filament to deform. Also made for reloading easier, as steps were smaller that the filament encountered while being pushed into tip. Not sure how the teflon is going to hold up over very long ABS prints, but OK so far with 4 and 5 hour prints.

asemeco
Posts: 1
Joined: Tue May 03, 2016 6:57 am

Re: Mk8 Extruder - filament jams in the throat.

Post by asemeco » Tue May 03, 2016 7:05 am

The transition from the nylon tube on top to the nozzle at the bottom has one piece with a diameter or 3.2 mm. Everything else in the filament path is 2 mm in diameter.

The filament gets snagged in the transition from 3.2 to 2 mm. See picture below:

https://goo.gl/photos/bgAXyHyze3bWo59u5

This a defect in the MK8 extruder. I think they mixed up parts from different nozzle sizes.

benedetto.luca
Posts: 24
Joined: Wed Apr 08, 2015 12:50 am

Re: Mk8 Extruder - filament jams in the throat.

Post by benedetto.luca » Tue May 24, 2016 3:25 am

Hi,
after have upgrade my MK8 from original one to new one, with teh 38mm barrel, I start to have hte jams in throat!!!
Finally I've found that new barrel is more "temperature sensible" then the ond 30mm one... with old one I was able to PLA print at 205°with 5mm retract, with a retract speed at 150mm/sec, when with new barrel I can print at same temperature, but with just 1mm retract and retract speed at only 40mm/sec.
With these new parameters I'm able to print without issuefor lot and lot hour!!

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