MK3s Constant Jams/Layer Skips Almost 100% fail rate
Hello,
About a week after assembling my mk3s while printing miniatures at 0.05mm layer heights a severe jam formed and the filament snapped at the PTFE tube rendering it unreachable. After extensive work to remove the jam the PTFE tube was left heavily deformed and damaged. During the next attempt to print a file I found that the printer was still jammed and when I dissembled the hotend I found a large plug stuck in the heatbreak. After this jam was removed the printer has constantly jammed or in rare cases skipped several layers then started extruding again. None of the solutions I have tried have made a significant difference to the jamming. Several of the solutions caused the first print after applying the solution to be completed successfully but that success could not be replicated.
The symptoms of the jam involve the printer continuing to move but not extruding, the extruder does not make any grinding noise when it jams but sometimes a clicking can be heard. In most circumstance I can fix the jam simply by unloading and inserting a new section of filament in. Because of this I am fairly certain that the jam is not caused by a blockage but to be sure I cleaned the nozzle. When the filament was removed before I swapped the heatbreak it had a diameter of 2.2mm at the plug.
The solutions I have tried
-decreasing and increasing the temperature
-decreasing and increasing retraction
-Printing at different layer heights ( this originally worked but only for around two prints)
-Using different filaments
-Printing the included g-code from the SD card to make sure a badly sliced model wasn't a problem
-Swapping the Prusa heatbreak for a standard E3d heatbreak ( This changed the length of the filament plugs, I haven't measured the diameter yet.
-Applying thermal paste (this got one successful print but all after have failed
-Moving the printer to an air-conditioned room as texas summers get crazy hot
-Disassembling and re-assembling the hotend
-Cleaning the filament drive gears
-Changing the tension of the filament idler ( this got two successful prints but none have worked afterwards and the success couldn't be replicated.
-Cold pulls
As of right now the printer has a standard E3d heatbreak installed but other than that it is unmodded. I do not use a MMU
My print settings are standard purse slicer settings except for the nozzle temperature which I have at 230 for PLA. This should be to hot for PLA but it worked much better and got more consistent extrusion than lower temperature.
Picture1- The jams currently being pulled out of the printer, it is hard to see because my camera wouldn't focus but the jam is squished off to one side so much that there is a 90 degree turn
Picture2- The jams pulled out before the heatbreak swap, it is hard to see the plugs but they are 2.2mm in diameter
Picture3- The initial jam and heatbreak plug
I appreciate any help with this, I have been attempting to fix it for two months to no avail. I have never seen anything like this.
Thanks
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
Just to confirm: You did replace the damaged PTFE tubing, correct?
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RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
As above, first thing that comes to mind. You said the PTFE was badly damaged, but no mention that you actually replaced it.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
Yes I did replace the PTFE tube
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
You seem to have fairly exhaustively done what you can with the stock extruder. At 0.05mm layer thickness, the extruder is being asked to work against quite a bit more back pressure than most of encounter doing 0.15 or 0.20 mm layers.
That is probably keeping your extruder motor under heavy load and heating it up, possible to the point of the motor shaft getting warm enough to soften PLA.
Also, among factors working against success with elevated back pressures is the Prusa filament path alignment which adds a bit more resistance on top of things. Prusa places the motor shaft Bondtech a bit further into the filament path than many of use prefer. With print to print variations, your motor Bondtech may even intrude so far into the path that it can move filament without the idler Bondtech.
What you can do...
1. Cool the extruder motor with a heatsink. This may help keep it from from softening your PLA filament at the Bondtechs.
2. Reprint the stock extruder and hopefully end up with a specimen that is less mis-aligned.
3. Change to a geared motor box to avoid transferring heat from motor to Bondtech and also boost torque
4. Change to a geared extruder with a corrected filament path.
It's that 0.05 mm layer thickness that elevates the challenge. That back pressure increase is also why you find an elevated temperature helped. More liquidity at higher temperature let the extruder push the filament more easily.
PS. I am assuming you have the PTFE all the way down and a collet lock installed to keep it fully seated.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
Thank you for the advice. I did some quick tests based off of it to try to narrow down the problem. I was not using a collet clip but I was able to print one as they do not take much time to print. I installed it but it did nothing to prevent jams. For the collet test I printed a model at 0.2mm speed standard prusa slicer settings. It failed in what appears to be the 8th or 9th layers and took less than five minutes to fail. I also checked on the motor temp and it was not yet hot. I also included a picture of the failed part, it was designed by me but I believe bad files aren't the problem
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
If you're still jamming at 0.2 mm layers and motor is not getting hot, then your issue is a mechanical blockage of filament movement or a high retraction setting.
Check in Printer tab of PrusaSlicer that retraction value is 0.8 to 1 mm (you can go up higher, but let's start with very safe baseline for E3D V6).
If that is okay, you must find where the blockage is happening by manual inspection....
Raise Z so you have a some inches free under the nozzle.
Heat nozzle to printing temperature
Undo tensioning bolt and open the idler door.
Manually feed in filament and feel how moves as you push down with finger pressure.
Does it get hung up at top of PTFE?
Does it perfectly align with Bondtech filament groove?
Is Bondtech idler gear well supported on both ends of its axle and free enough to self-align?
Leaving idler door open, manually push in filament.
You should be able to extrude the filament in a nice strand with just finger grip and pushing down. Should steadily give like pushing a knife into a cold peanut butter jar.
If the filament is really hard to advance, remove both filament and nozzle.
Reach up into hot heat block with q-tip and spin q-tip out to remove debris that has accumulated.
At this point you have a wide open and hot filament path. Pushing filament through should encounter practically zero resistance. However after doing that be sure to throughly re-clean inside the heat block with q-tip before re-installing nozzle.
If you have resistance with nozzle out, there is something wrong within your PTFE tube.
Install fresh nozzle and feel again. If resistance to flow is now reduced, you know the old nozzle was partially clogged.
Don't forget to final tighten nozzle at 285C for full seal. Personally, I do NOT follow the Prusa 45 degree heat block twist, but just keep it steady with wrench.
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Could we get a pict of your nozzle and heat block. I'd like to verify it is at full tightening before reaching heat block. If nozzle hex is flush with heat block we know the heat break is not far enough into heat block.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
One more thought. You did chamfer the bottom end of the PTFE to form the correct angle, right?
Don't mean to insult you, but sometimes have to check the obvious stuff too.
The bottom end cannot be a 90 degree cut or you will form a clog just beyond the PTFE end. For that matter, both ends of the PTFE are chamfered. Bottom end gets external chamfer and top end needs internal chamfer.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
No insult taken, I understand the need to check all possibilities. The PTFE tube spares that were included were already chamfered and cut to length so I did not modify them. Sorry for the orientation of the picture didn't realize they only display landscape pictures correctly. Upon inspection of the nozzle I realize the heatbreak could possibly be too far in the heater block.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
Yes, it looks about 1/2 turn too deep for the heat break, but I doubt that is enough to cause your clogging issue.
I would go through the process I described for ruling out obstructions in the system.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
Sorry for the long wait its been crazy busy, I have not yet had time to disassemble yet but its on my list but I came to bring new information. The printer will not jam when its set to 245. I don't know if this because the extra heat makes the pla more fluid so it can overcome obstacle or because the temp is off either way it is weird.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
I don't know - my opinion is the nozzle position is fine. But the filament stubs looks like the typical heat break jam.
Sinking the heat break in another 1/4 to 1/2 turn might help. But nozzle temps will suffer a bit. If not using an MMU, I'd just replace the heat break.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
I’ve already replaced the heartbreak with a stock e3d heartbreak. The only difference it made was temporarily changing the shape of the plug. It is now the same shape as it originally was. I don’t know how that would happen but it is
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
If those images above were with the "new" heat break, E3D didn't send you the right one.
There is no 2.2 mm section in the stock E3D-V6 heat break.
RE: MK3s Constant Jams/Layer Skips Almost 100% fail rate
To clarify, the pictures of the jams I posted were of the original jams before I swapped heartbreaks.. I have yet to measure the new jams but they still have a plug at the end. When possible I will send pictures of the new filament plugs.