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Consistent heat break jams - PLA  

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liam.t4
(@liam-t4)
Active Member
Consistent heat break jams - PLA

Hi all,

I purchased and built my Prusa i3 Mk3 a couple months ago and have since gone through the entire provided silver PLA roll with great success. I have had very mixed results with all other filaments, with prints failing due to jams regularly. This problem now occurs on all prints, approximately 1 hour into the print.

There is no clear blockages or debris surrounding the bondtech gears, nor is there any blockage in the nozzle. This jam appears to be consistently occurring around the heat break (heat creep?). I have confirmed both fans are operational and correctly orientated. All jams are completely removed before attempting another print.

If anyone has any suggestions on how to fix this, I would greatly appreciate it. Print quality has been superb right up until each jam. My print specs are listed below. I have not attempted any prints with ABS or other plastics yet.

Slicer: Prusa Slic3r editions
Firmware: 3.3.1
Temperatures: 215, 210, 205, 200 (With all other settings remaining as default on Prusa Slic3r edition).
Ambient temperature: 14 degrees celcius
Enclosure: Prints have been completed both with and without an IKEA Lack enclosure
Filament: Kiwi 3D (1.75mm +/- 0.02mm). I have been unable to confirm the accuracy of this, my calipers are only accurate to 1dp.
Layer heights: 0.2mm, 0.15mm, 0.10mm (Default Prusa setups).

Posted : 19/08/2018 7:27 am
Gato
 Gato
(@gato)
Reputable Member
Re: Consistent heat break jams - PLA

It does sounds like heat creep. Many people run into this due to different reasons. What's the temp of the extruder motor? Sometimes it gets too hot and that heat gets transferred to the PLA path softening the filament and producing a jam. Or could be tension of bondtech screws is too high. Or could be some clog in the hotend that increases the resistance and raises the temp. The newly released R3 version improved cooling of the heatsink and solves heat creep from the extruder motor.

Posted : 19/08/2018 11:32 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
Re: Consistent heat break jams - PLA

The Teflon tube is wrongly mounted and is too high up. This can cause problems in Hotend.
Look at this post, it's the same problem as you have.

https://shop.prusa3d.com/forum/general-discussion-announcements-and-releases-f61/extruder-squeaking-caused-by-ptfe-tube--t23811.html#p102758

Bear MK3 with Bondtech extruder

Posted : 20/08/2018 2:06 pm
liam.t4
(@liam-t4)
Active Member
Topic starter answered:
Re: Consistent heat break jams - PLA

I printed the R3 extruder and trialed a print on that but the issue persists.

I've been careful to not overtighten the bondtech gears, but I haven't checked the extruder motor temperature.

Could you explain how the PTFE tube is too high up? The extruder comes pre assembled. I've tried to reseat the PTFE tube but can't seem to seat it any lower.

Posted : 23/08/2018 12:36 pm
MrLogston
(@mrlogston)
New Member
Re: Consistent heat break jams - PLA

I have the same problem, does anyone know a fix? my extruder gets really hot also, seem to have tried everything and I am at a dead end. I am thinking about just reverting back to the MK2 setup so I can actually print something.

Posted : 04/09/2018 3:53 am
liam.t4
(@liam-t4)
Active Member
Topic starter answered:
Re: Consistent heat break jams - PLA

There's no fix for the problem from Prusa as of yet. If you want to keep printing in the meantime, try placing a large desktop fan facing your extruder during prints. The extra airflow is enough to keep the extruder cool and prevent jams during prints.

I saw this 'solution' in another thread, and can confirm it works. Far from ideal, but it's the best solution till the issue is resolved.

Posted : 04/09/2018 5:21 am
Nikolai
(@nikolai)
Noble Member
Re: Consistent heat break jams - PLA

It's easy to blame some generic issue. Since R3 parts I'm printing on my MK3 and MK2.5 without any issues. Environment temps around 30C and Makergeeks PLA with 235C. I don't see any generic issues on my printers.

I had a lot of jams with my first printer MK2. It took me some time to understand why it's happening and what need to be tuned in the slicer and printer in order to print problematic filaments/objects.

My advise is to find an object where you can replicate the jam/clog. Adjust the slicer settings/printer settings one by one and see how it affects the print.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram

Posted : 04/09/2018 5:41 am
Olef
 Olef
(@olef)
Prominent Member
Re: Consistent heat break jams - PLA

I do not believe this is a generic issue. I have been printing PLA on two Mk3's constantly for the last week and a half with no sign of heat creep jams.

There are probably over ten thousand of these printers running now. Just because a dozen people report a problem does not mean all of the printers are affected.

It is very easy to blame Prusa and say "it's an issue with the printer itself and Prusa have not fixed it". Over the last year I have lost count of how many times I have read that on an issue that a few users have - issues I have seen no sign of.

If it is any help my extruder motors are running fairly hot, 45 - 50 degrees C. and as I say I am seeing no sign of heat creep issues.

Posted : 04/09/2018 8:32 am
liam.t4
(@liam-t4)
Active Member
Topic starter answered:
Re: Consistent heat break jams - PLA

I'm not suggesting there is a generic issue with all printers that Prusa needs to fix.

I'm currently working through the issue with Prusa support, so I'm hoping they're able to come up with a solution that myself and the other people with this issue have overlooked.

Posted : 04/09/2018 11:44 am
MrLogston
(@mrlogston)
New Member
Re: Consistent heat break jams - PLA

I have the same problem with jamming. My extruder motor gets as high as 65 C using a heat gun to read the temp, the hot end temps seem fine and the print seems fine until it jams an hour into every print. I have owned an MK2 for 2 years and have had no issues with it other than wear and tear.

I have tried:

changing nozzles and maintaining a slight gap between the nozzle head and the heat block,
slowing down print speeds 50% and it still jams about an hour to two hours into all prints.
all reasonable heat settings for the hotend 190-230 C,
updated firmware,
Prusa supplied gcode, gcode from PrusaControl, Sli3r, and Cura
different filaments, and filaments that work on my MK2
nozzles pulled from my MK2 that is sitting right next to it printing fine as well as new nozzles.
triple checked all fan directions and extruder alignment,
tried all possible tension settings on the idler; too loose to too tight and everywhere between on the extruder springs
I cannot get the MK3 to finish a 5 hour print with out jamming.

All I can think of is that my hotend is defective or the extruder motor is defective and overheats prematurely somehow. Thousands of these machines are running fine and mine wont work after 4 months of owning it. Now I am printing the updated extuder assembly at my own cost using my MK2 so that I can rebuild hoping that it is just a defective printed part causing the issues somehow. But I bought this MK3 printer to save printing time over my MK2... 🙁 The grass is not always greener on the other side.

Posted : 09/09/2018 2:28 am
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