loosing small herringbone gear

So here’s my problem -
the small screw shown in the image gets loosened after a while. So, naturally the filament stops coming out because the whole transmission faults

This second image shows bite marks, as you can see. Those are made by the little screw, because I try to screw it on as tight as it can. It get’s loosened somehow. Any suggestions?
Maybe I push the filament too hard from the other side… and then applied pressure transfers… I dunno…

Is an M3 nut inserted into the base of the small gear? It gets pressed into the base of the small gear, into the rectagular slot. You can also use blue thread locking compound (not red) and that should keep the set screw from loosening.

Well the M3 is inside of course, where it should be. I think the problem is in contact between the set screw and the stepper motor rod. Can that blue thing make a more firm connection between?

The blue thread lock won’t make better contact with the stepper shaft, but it will keep the set screw from potentially loosening. How much play is on the small gear when it’s on the stepper shaft? When installed, even without the set screw, it shouldn’t have a lot of wiggle. Did you drill out or clean the small pulley?
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I know this is an old thread, but it seemed like the best one to resurrect / post in. Just wanted to say that i designed a small herringbone gear mod to help prevent this little gear from slipping. Some people may or may not find it to be useful. For those that do decide to use it you may or may not want to grind a second flat side onto your stepper motor shaft for the set screw to hold on better. But in theory (even without locktight) this design should help prevent this little bugger from coming loose.

Do you have a link handy to the file?