Bambu AMS Helical Gear

I'm not sure how this happened, but the helical gear that meshes with the worm gear on the Bambu AMS first stage feeder stripped out. When trying to feed filament, the worm gear would just grind against the helical gear and made a big mess of things.

The material used on these yellow gears is pretty soft. Given that all of the rotational mass for a 1KG spool is placed right on this gear set, I'm surprised more people haven't experienced this.

Since this gear seems to have a lot of sheer stresses, print this with nylon carbon fiber, like PA-CF or PAHT-CF from Bambu. And since it's pretty tiny, I printed with the finest layer height, 0.08mm with 100% infill. Also include supports and print with the smallest hub facing down on the build plate. The two sides are different on this gear. If you have the front of the feeder facing you, the left side of the gear has a 2.5mm hub. You can also see 3 bumps on the yellow gear, indicating the left side. The right side has a 2.0mm hub, so you have to look very closely to spot the difference.

After printing the gear, disassemble the AMS and pull the bad feeder out. Then follow Bambu's guide to disassemble the top cover.

To remove the shaft with the cluster of gears:

• Take lots of pictures as you do this!
• Use a small flathead screwdriver to push the brass bushings out, just enough to pinch the other side with the flange with some vise grips and pull them out
• After the bushings are out, spread the plastic shaft mounts and pull the whole shaft with the 5 gears attached to it
• Find a small socket that fits around the shaft, but contacts the yellow gears
• Find a small screwdriver that is smaller than 3mm diameter
• Use the screwdriver, socket, and hammer to tap the gears off the shaft

Working backwards, install the new gear:

• Pick a side, tap on a gear set. (Either the left side that drives the spool, or the right side that drives the extruder) Use a socket to pound it on a little past the end of the shaft
• Tap on the new helical gear
• Tap on the other side's gear set.
• Place them back in the plastic shaft holder
• Add a little light machine lube to the brass bushings and tap them on
• CHECK THE TIGHTNESS. After I put the brass bushings on, the movement was very tight. I took them back off and used an 1/8" drill bit to open up the bushing bore a little bit more. It was so tight that the motor wouldn't even move, and I suspect that might have been the original problem that stripped the gear out.
• If you have a nice 3 - 6V DC power source, you can spin the motor up manually by applying some juice directly to the positive / negative terminals. That way you can test that the gears mesh and the tolerances aren't too tight.

It should look like what I have in the second photo. Reassemble everything else and test!