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Nylon gear slipping along the shaft of new UM2+ feeder.

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I'm experiencing issues with the white nylon gear on the shaft of the new UM2+ feeder (upgrade kit) is slipping along the motor's shaft. It's happened to twice so far. The first time the gear slipped off the end of the shaft, and the second time it got pushed flush with the motor body. The gear doesn't show any sign of damage - it's just moving up and down the shaft under the force of extrusion/retraction.

Suggestions would be very, very welcome.

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I had the gear slip off the motor axel again.

In fumbling with it I noticed that some of the lube was on the shaft as well.

I suspected that's half the issue, so I pulled out an alcohol swap, cleaned off the small gear (especially inside the hole) and the motor axel. Then I put a spot of superglue on the shaft for good measure before replacing the gear. I couldn't make it budge after that, so with luck that's the trick.

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I have this problem also. There is not a lot of diagnostic information about it yet, so I thought I'd share the symptoms I found:


  • Despite a clean bowden and extruder assembly, under extrusion persists
  • You may hear occasional loud pops and see the filament shudder (this is the gears slipping out of engagement)
  • During printing, the movement of the filament will become stuttered and anemic, but the motor will not skip back (because pressure is not building at the extruder)
  • Eventually the filament may stop moving at all
  • Low scraping or clicking sounds from the feeder


Here is a visual of the feeder while this is happening:


If you watch the slotted bearing (which is the end of the knurled wheel), you can see it moving very poorly, then stopping and sometimes skipping back slightly. If this happens to you it is wise to remove the plastic housing and check the position of the nylon gear on the shaft. It should be flush with the end of the shaft.

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Shouldn't the two circles be perfectly aligned? The circle of the metal plate and the circle of the white frame.

There is some slack in the design. Perhaps it is enough to cause the gears to slip over time. I corrected that also before I put the feeder housing back on by loosening the plate and holding it up while I tightened the screws.

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The super glue should hold it in place. I've seen this in a few instances. I think it may be the tolerances between the gear and the post, or green grease slipping between the two parts. So far, the printer I experimented with using the superglue seems to be holding. I think the gear slippage tends to be a wear and tear issue, though there could also be a slight variance in the gear size. I don't believe I've seen the issue occur more than once on the same machine, so it should only be related to the gear, rather than the feeder, as I will generally replace the gear if it it slips.

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Is there an official part replacement for this issue? The upgrade kit wasn't cheap and it seems inevitable it will happen to everyone.  Super glue and hope doesn't sit well with me.


It looks like you're in the US. It shouldn't be an problem to get a replacement gear out to you. Contact support@fbrc8.com as your local support.

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