Cleaning hobbed bolt?


Happy owner of a mini! Thinking I need to clean the Hobbed Bolt after some 40 prints. I’m starting to get a ticking sound as the filament is fed through.

The instructions say to use the included dental pick and wire brush… I’m just not sure on the details of that process. Am I supposed to remove the filament, then stick the brush / pick down the feed hole?

Thought I’d ask before doing any serious damage :slight_smile:

Appreciate any guidance.

If you release the idler clamp you can see the hobbed bolt looking down from above. I just turned the power off, then used the pick to poke out the little chips of filament that were loaded up in the teeth. You can only reach a few teeth at a time, then spin the large herringbone gear and clean a few more.

I’m not sure that a dirty hobbed bolt would make a ticking sound, however.

I just pulled a dumb move and extruded (or tried to extrude) some material while the head was cooling down. Sure enough I packed the hobbed bolt grooves with a nice amount of plastic…
I flipped open the feeder tensioner and looked down on top of the hobbed bolt. I used the little wire brush they give you, and used some compressed air in my shop to blow away the pieces. I rotated the big feed gear and blew out the pieces while working them loose with the wire brush.
It may not have changed much, but I feel better having done it.

Thanks for the reply.

So, the hobbled bolt is silver? Sits above and to the side of the feed hole? If so, I don’t see any build up there.

The click I’m referring to can be heard in this video at ~3 seconds and again ~19 seconds in. I thought it was coming from the bolt as I only hear the tick when it and the herringbone gear are moving. No click when the printer is self leveling or cleaning.

Watch the lower left Z motor coupler at the instant the tick happens. I think you’ll find that your coupler setscrews are loose or missing in the top or bottom section of that coupler. make sure to tighten both setscrews on either end of the coupler.

Picked away at the bolt and tightened everything I could find. I’ll run a print tomorrow and post up results.

Thanks for the help!

An alternative to brushing is using a vacuum with the crevice tool. My printer’s indoor’s so no luxury of brushing filament filings to the floor. :slight_smile:

The sound is like the hobbed bolt popping its knuckles. A little is fine, but if it does it a lot then the bolt needs cleaned and idler pressure adjusted.

How tight are the idler springs? Can you post a pic of them?

It may just be the angle, but looking at the video it appears the idler is VERY tight (screen capture attached below).

Try adjusting the idler tension knobs such that the silver washers on either side of the spring are about 7-8mm apart.

I think the idler spring spacing is recommended at 8mm, but could be wrong. There’s also a jig which LB has started recommending.

Yes! Thank you all!!! The Idler spring were too tight. Loosened, and printing again like new. The clicking is gone.

Happy printing, everyone!

I found I had to tighten my adjustment to about 7mm to prevent slipping. The 8mm space that the jig provides was just too loose (I was printing with PLA at the time).

Live and learn… Been a relatively trouble free experience however. Love this printer.

I’m suddenly also experiencing clicking sounds from the feeder. I have printed the 8mm jig, but I’ve read different posts on how to use the jig. Some posts suggest that the jig needs to be in between the metal washers (thus the length of the spring itself) and some suggest that it should sit between the face of the idler and the edge of the ridged section of the idler tension screws.
Does anybody knows the correct answer?

Technically either of those positions will do the same thing. But it’s intended to go over the springs when setting the distance.

Thanks! I have loosened the screws, so now it fits over the springs only. I still hear a click once in a while, but it seems to work better. Currently printing a model, so let’s see if it is working again. Had a lot of issues lately. Especially models with a lot of Z-hops, causing the feeder to ‘eat’ the filament…

The clicking sound can sometimes be retraction. If it is skipping still, you may want to check the small gear to see if it still has sufficient tooth profile to engage the big one, and check that the hobbed bolt nut is tight enough to prevent bolt movement in the shaft, but not too tight to prevent rotation. That nut can work itself slightly loose over time.

We just posted a short video about hobbed bolt cleaning