Filament jamming hours into print  

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john.h78
(@john-h78)
New Member

I have the same problem on my MK3 and my new MK3S. Hours into the prints, the filament becomes jammed and stops extruding. I use default print config from PrusaSlicer. 

This seems like a hardware issue, and if so how is this still and issue with the MK3S?

Posted : 17/05/2020 3:47 am
stephan.l6
(@stephan-l6)
New Member

I have the same/similar issue. 

My extruder motor gets very hot (bearly able to touch and hold for more than a sec.)  Is it the same for you? 

Posted : 13/06/2020 2:02 am
macgasking
(@macgasking)
New Member

I had a similar problem yesterday  The printer stopped extruding 6 hours into a 7 hour print.  Initially I thought it may have been a spool problem or possibly a hard portion of PLA.  I restarted the job and extrusion failed about 20 mins into the job, twice in the same place.  There was no sign of a spooling restriction. I have restarted the job this morning and so far - so good.  I noticed that when the temperature reduces after the intitial first layer it overshoots quite considerably before very slowly recovering. I have seen this before and now watch carefully and immediately manually reset the required temperature from within Pronterface.  The hotend responds immediately.  Indicated temperatures on the Prusa controller display appear to be accurate and because the hotend reacts quickly to a Pronterface temperature adjustment, I see no reason to suspect a connection problem. As the hotend follows the required temperature instructions issued by Pronterface I am not seeking to recalibrate the PID ..... yet!

 

PS I noticed that during the 6 hour print a crash was reported several times with no obvious reason.  Inspection of the print showed a very occasional (two or three)  slight delaminations  of the 0.15mm layers, possibly due to an extrusion problem but I thought not sufficient to cause contact with print head.  The ambient temperature was probably above 30 in the workshop; maybe related?  The PLA was just out of the box and therefore assumed to be dry.

Posted : 25/06/2020 7:00 am
Neophyl
(@neophyl)
Noble Member

When it gets warmer we always have this increase of 'extruder clicking', 'filament jamming' posts.

The V6 hotend is AIR COOLED.  Its maximum rated temperature is supposed to be 40 degrees, and I suppose it is if all you are doing is feeding filament through it at a reasonable rate as the filament its printing will carry heat away from the system.  However when you have retractions, are printing slower due to small parts or complex shapes etc then you aren't carrying that heat away as fast and it will get warmer further up the heat transition area.  You then add to that the extruder stepper can get hot and pre soften materials like PLA which is adding more heat into the system and you get, well exactly the issues that people report. You also get people running their printers in enclosures.

You need to do everything you can to cool things down without introducing drafts towards your printing part.  I have seen all sorts of methods used.

For hot extruder motors then the simple addition of adding 2-3 heatsinks can drop the temperature by over 10 degrees.  Another option is to print one of the cooler shrouds with extra fan that are available on thingiverse.  There are ones specifically designed for the Mk3 setup.

For cooling the hotend I have seen people modify them with lightweight tubes to draw air in for external away from the printer that connect to the area of the hotend fan.  Designs also available on thingiverse.  Others set up normal room fans to circulate air around, although you have to be careful due to drafts.  Another thing I have seen is people replacing the stock hotend fan with a bigger one that can move more air.  These require printed vent ducts as you can make the fan bigger/thicker without it hitting the left side of the printer but it is possible.  Once again a google search/thingiverse is your friend.

Posted : 25/06/2020 7:36 am
macgasking
(@macgasking)
New Member

@neophyl

Thankyou for the prompt reply.  Air conditioning is now on and a heat sink on top of the motor.  Two hours into the print ........

Posted : 25/06/2020 8:07 am
john.h78
(@john-h78)
New Member

@neophyl

Yes you are right, makes a lot of sense and is what Prusa has told me. My prints are highly detailed and therefore a lot of retractions, so so many. 

My MK3 is actually printing most of these models successfully, but my new MK3S jams within 10 to 30 minutes and has been since I got it in May when I posted  about it, and it is gathering dust while the other one is printing.

I'll follow your suggestions and post results.

Thank you for your detailed response.

This post was modified 1 month ago by john.h78
Posted : 25/06/2020 12:55 pm
macgasking
(@macgasking)
New Member

The print completed successfully.  Aircon and fans were on.  Subsequent jobs in the afternoon all failed but by then the ambient temperature was about 36C.  I was printing PLA.  I am confident that there is not much to be easily done in that environment and, as it happens so rarely, I will live with it.  If it is a problem with the PLA at that temperature being too soft for the gears, or being too elastic to extrude, it would have been interesting to try PETG or ABS, or even Nylon, to see if they are more resilient to a higher ambient.

 

Reference you comment about multiple retractions affecting the cooling, I was vase printing so little retraction;  however it would appear that the problem is more susceptable to lower build heights; smaller surface area?

 

FYI the top of the V6 heat sink was about 50C and the motor was comforably down low 40s.

 

 

 

This post was modified 1 month ago by macgasking
Posted : 26/06/2020 9:41 am
Neophyl
(@neophyl)
Noble Member

Not entirely sure about the lower layer height but given that lower layer heights are usually used for better quality and therefore slower prints it sort of makes sense that the filament throughput would be lower too.  One thing you could check is on your sliced model in the slice preview you can select different options for data.  If you select 'volumetric' you can get a good idea of how much plastic is extruding in different areas.  Speed is also handy sometimes but it tends to closely match the volumetric in practice.

 

Posted : 26/06/2020 10:06 am
macgasking
(@macgasking)
New Member

Turned out to be slack in the PTFE tubing.  Removed and replaced holding the Bowden connector in tension.  No problems since.  Retraction was causing the tube to lift and form a bead of filament in the gap.

Posted : 02/08/2020 4:09 pm
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