Extruder too tight?

I printed my first (really screwed up) calibration cube this evening! However, as it fed filament in it would make a loud clicking noise and I could see the small extruder gear almost bouncing while it rotated through its cycle.

In the build instructions you say to make sure the hobbed bolt and large gear spin freely. I hand tightened the bottom nut initially and when I went to look at it it had spun completely off the bolt. I think ratcheted it down fairly tight, but I could still manage to turn the gear by hand. The large gear is now right up against the bottom of the main extruder assembly and the motor is still having trouble turning it. Would a washer between the gear and bearing help with what appears to be binding?

I'm hoping the problem here isn't that the motors just aren't strong enough, but I'm afraid that's what it is :/

I used a lock nut against the gear/nut.

A washer may help but could result in the hobbed bolt being pulled tight from top to bottom and cause even more friction. If you are having a hard time getting the large extruder gear in the correct spot you could put some locktite on the nut and let it dry before tightening the jam nut against. This should allow you to tighten the jam nut without worrying about the gear threading on further and causing a jam. Also you may want to have a small piece of filament in the extruder while doing the lower gear to make sure the hobbing is aligned with the inlet and outlet hole.

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Sublime Wrote:
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> A washer may help but could result in the hobbed
> bolt being pulled tight from top to bottom and
> cause even more friction. If you are having a hard
> time getting the large extruder gear in the
> correct spot you could put some locktite on the
> nut and let it dry before tightening the jam nut
> against. This should allow you to tighten the jam
> nut without worrying about the gear threading on
> further and causing a jam. Also you may want to
> have a small piece of filament in the extruder
> while doing the lower gear to make sure the
> hobbing is aligned with the inlet and outlet hole.


So putting locktite on the gear's nut and letting it dry before securing the jam nut? That seems like it should work. By design the gear needs to be up against the bearing doesn't it? Otherwise if there are exposed threads it's just going to walk up them before having enough friction to move the bolt itself?

SkyArcher Wrote:
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> I used a lock nut against the gear/nut.


A lock nut as the bottom jam nut? Or between the bearing and the gear's nut?

maik Wrote:
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> SkyArcher Wrote:
> --------------------------------------------------
> -----
> > I used a lock nut against the gear/nut.
>
>
> A lock nut as the bottom jam nut? Or between the
> bearing and the gear's nut?


Trap the gear between the two nuts and tighten. Loctite is a good idea.

No the gear does not need to be against the bearing. The filament will keep the bolt aligned with the entrance and exit holes. You almost want a small space between the gear and the bearing once the filament is aligning the bolt. I would say 0.5 to 0.75mm.

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Sublime Wrote:
-------------------------------------------------------
> No the gear does not need to be against the
> bearing. The filament will keep the bolt aligned
> with the entrance and exit holes. You almost want
> a small space between the gear and the bearing
> once the filament is aligning the bolt. I would
> say 0.5 to 0.75mm.


Ok. I bought some metal lock nuts over lunch as well as some locktite. I set up the locktite with the regular nuts and left about that size of a gap (possibly larger) between the gear and the housing. Can't play with it again until probably 9pm PST so hopefully I'll have some good things to report this evening.

I sorted this about a week ago. Turns out I was an idiot and skipped over the E axis calibration step. Reversed 55mm when I asked for 50mm. Made the changes in the firmware and cleared it right up.

Edited 1 time(s). Last edit at 08/16/2013 06:39PM by maik.

I'm having a similar problem. My large gear is getting pulled up against the extruder body. Is there a way to fix this short of locktite? Seems like the gear is always going to be pushed in the direction that will break the nut lock... Something on the bearing side of the gear perhaps?

Edited 2 time(s). Last edit at 01/30/2014 11:39AM by AGStumps8807.

I just have mine really really tight. But if that does not work you can put a small drop of CA glue on the exposed threads and between the gear and that same nut. This will lock the nut to the bolt and the gear to the nut. If you have to remove it ever you can just use some acetone to dissolve the glue (at least with PLA parts, ABS will melt)

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Thanks Sublime. I think I've probably been leaving it a little too loose. Hopefully first print tonight!