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MK3S getting clogs in filament sensor  

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gacky2k
(@gacky2k)
Active Member
MK3S getting clogs in filament sensor

Hey gang...I searched and couldn't seem to find a post on this so if it already was answered, I apologize in advance.  I've had my MK3S for about 6 months I guess, it gets pretty regular use, and I've had several clogs in the filament sensor.  They lead to the filament getting bound up tight in the channel the filament runs through making it impossible to remove the filament.  I always end up having to partially disassembling the front of the hotend to get to the chamber with the ball in it and find it clogged up with filament debris.  Not sure what is causing this.  Anyone have similar issues?  

At first I thought maybe it was too small and the filament was rubbing up against the channel walls and causing the buildup, but once I clean it out, filament seems to slide in and out pretty smoothly.  So, not convinced its that now.  I don't know what it could be.  I thought it also might be too loose or tight tension on the extruder's gears that was causing the debris, but not sure how that would get that far above gears and into that block with the ball, and eventually clog the channel that the filament runs through.  I'm using complete default settings in PrusaSlicer for retraction not doing anything custom at all.  I generally only change simple things like infill density and the number of perimeters.

Thanks in advance for any suggestions!

Posted : 20/11/2019 3:30 am
rmm200
(@rmm200)
Noble Member
RE: MK3S getting clogs in filament sensor

Likely candidate: The gear can't force the filament into the PTFE tube and is chewing it up.

If you hear the extruder "clicking", unload the filament and look at it. I suspect chewed up.

Next step - why can't the filament feed. Check the path between the gear and the PTFE tube and make sure it is straight.

Use cleaning filament or cold pulls until you are sure the nozzle is clean.

Look for any symptoms of heat creep.

Sacrifice a goat. Just kidding - I like goats. Try a politician.

 

Posted : 20/11/2019 4:00 am
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(@)
Illustrious Member
RE: MK3S getting clogs in filament sensor

The filament sensor is not a spot where filament binds up ... so I think the premise is in question.  A common malady is when the filament runs out and the sensor isn't enabled, the loose end travels down and gets snagged in the chamber the filament sensor is in. Filament can't be unloaded.

The fix is don't let the filament run out, or ensure the end of the spool has a clean cut rather than the 90 degree L many manufacturers place to fill the spool.

The other possibility is insanely dusty filament. But that'd be a stretch.  If it is dust, then use canned air to blow out the sensor area weekly.

This post was modified 2 years ago by --
Posted : 20/11/2019 4:30 am
gacky2k
(@gacky2k)
Active Member
Topic starter answered:
RE: MK3S getting clogs in filament sensor

Thanks for the suggestions.  It's very fine, like dust fine.  I've never had the sensor malfunction.  Usually...just before it seizes up and the filament gets stuck, the extruder does indeed make a lot of clicking noises.  That's how I know it's about to fail and seize up on me again.  It get's totally stuck too...I mean can't release the tension of the gears and pull it out by hand, can't unload it the normal way...it's froze in there solid.  I've done cold pulls and the tip comes out beautiful, it's definitely not something in the hotend or the PTF tubing.  It's happening ABOVE the gears...in the small black part that the filament runs through and the ball itself is in.  It's a simple fix, takes me about 10 minutes to disassemble, clean it out and reassemble...I've got the process down cold now   🙂   But still....I'd like to figure out why it happens and avoid it, if for no other reason than to avoid the inevitable failed print  🙂

I don't know...I guess I'll just try to make a new habit of once a month or so, doing a preventative disassembly and clean it out before it becomes problematic.  The only thing about that though is that the degree to which I've been having to disassemble it to do this, also requires me having to rerun my first layer calibration to get it dialed in perfectly again...seems to always mess my Z height up a tiny bit.  I'm just a bit too lazy to want to do all that as a preventative measure assuming I can't figure out the cause.  So I guess I'll either have to live with the clogs, figure it out, or make me self do the preventative cleaning and re-calibration periodically.

Next time it happens, I'll take pictures, maybe that will help someone spot what the culprit could be.

Posted : 20/11/2019 9:20 pm
rmm200
(@rmm200)
Noble Member
RE: MK3S getting clogs in filament sensor

If you don't touch the nozzle, or jar the PINDA - nothing you are doing should affect Z or require re-calibration.

Not that telling you that helps any...

Just to mention again - the clicking, along with chewing up the filament, means filament is not feeding successfully into the head.

Heat creep, contamination, something...

Posted : 20/11/2019 10:09 pm
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(@)
Illustrious Member
RE: MK3S getting clogs in filament sensor

Take a photo and mark where you think it's jamming.  The filament sensor simply has no way to collect dust like you describe.  So we'd need more to go on than a text description.

It also wouldn't hurt to post a photo of your spool holder, and any filament guides you've installed.  

Honestly, in the years I've owned my MK3, I have never had severe dust in the filament sensor except when I've had jamming problems and the Bondtech was chewing up filament by the yards.  Since I solved that issue I have never had to clean the sensor area.

This post was modified 2 years ago by --
Posted : 21/11/2019 12:19 am
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