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The Dreaded Filament Drive Clicking Sound...

Posted: Wed Dec 19, 2018 4:31 pm
by Gwhite
I switched from red eSun PETG to some white HatchBox PETG, and after purging the extruder for a while and starting a small print job, I started getting clicking (actually, more of a clunking...) from the printer. The part was long & skinny in the Y directions, and it was most noticeable when it was running back & forth in that direction. Initially, I thought it was something mechanical in that drive system until I noticed I wasn't getting any filament extruded.

I shut it all down and tore the filament drive apart. As best I can tell, the filament had stuck in the extruder somewhere. The filament drive gear had shaved/melted enough filament to scoop out a section of the filament so the gear could now spin freely, but I had a blob of filament in the drive below the gear that prevented pulling the drive housing off. The wasn't enough room between the extruder and the drive to easily cut the filament there, so it took some surgery to get it all apart. I eventually managed to reduce the blob inside the drive to the point where I could get a small cutter between the drive housing and the extruder and snip the filament.

I wasn't sure if I had stripped the pinion in the drive gearbox, so I installed a spare drive motor. I had been using a PETG filament drive housing I had modified to use a grooved bearing sleeve (see viewtopic.php?f=7&t=6724&p=37246#p36959. I had been printing just fine for quite a while with this, but I've been a bit nervous about running PETG through a PETG housing, so I also switched back to a factory ABS drive housing.

I took the nozzle off the cold extruder, and it came off just fine, and had a nice clean hole. I installed that on a spare extruder and put it all back together. It seems to work fine now.

Now that the printer is running again, I have a pile of "dead" parts and many questions to ask. The filament drive housing appears to be fine. I took the gearbox apart on the motor, and although there is possibly a bit of wear on the pinion, it also looks OK. The extruder now has white PETG jammed in it, with no nozzle. So, my questions:

Drive motor: Is the clunking for a while likely to have done any damage to the motor? How much wear is OK on the drive motor pinion? At this point, the teeth just look a little asymmetrical. Should I just replace the pinion, and if so, how? I seem to recall it's a press fit. Do I need a tiny gear puller to get it off? If so, any recommendations?

Drive Housing: Any reason to worry about running PETG through a PETG housing? The problem seemed to start when I switched to the HatchBox filament, which is what the housing is made of, but the jam in the drive appeared to be the result of something downstream, and not the drive/housing itself. Once everything cooled down and I carved the blob off the filament, that piece came out just fine.

The extruder: What's the best way to clear out the extruder? I have some nylon, and could try to do a "cold pull" for the first time. I'm a bit baffled as to what jammed and where. Given that the nozzle came off OK with a clean hole, whatever it was is presumably still in the extruder somewhere. I could also put a larger nozzle, and try pushing some cleaning filament through it.

Thanks for any ideas, comments & suggestions!

Re: The Dreaded Filament Drive Clicking Sound...

Posted: Wed Dec 19, 2018 9:08 pm
by Phil
The drive motor and gear are much harder/tougher than the plastic filament, so I do not think you can hurt them in that way. I have often heard the 'clunking' and have found it to be from the filament sticking in the extruder, the gear cuts a divot from the filament, and the compression and sudden release of the filament against the drive gear makes the sound.
To clean the extruder, try extruding with the nozzle off. Pinch off the plastic, then retract the filament a little before re-attaching the nozzle. That should clean out anything in the extruder.
I have printed with steel filaments. Some are very brittle and fracture in the housing, causing jams. BIG PITA when using these filaments. I have performed corrections more times than I like to count.

Re: The Dreaded Filament Drive Clicking Sound...

Posted: Thu Dec 20, 2018 12:27 am
by airscapes
For the clogged hot end, I had that happen once and just removed it from the mount, took the fiberglass sleeve off and "Gently" locked it in a small pair of vicegrips. Then fired up the hot end and pushed some plastic though by hand quickly removing it when it was cleared.
I replied to you PM, sorry I was so late responding!

Re: The Dreaded Filament Drive Clicking Sound...

Posted: Thu Dec 20, 2018 1:56 am
by Gwhite
Thanks for the comments!

I'll have to check the notes I have on doing a cold-pull, which I believe you do with the extruder unmounted. I've been thinking about machining a "handle" that would clamp onto the extruder the way the normal mount does. I'd prefer not to chew up the mounting surface with pliers or vise grips...