Zero-length planetary gear head for NEMA 14 extruder

Here's an ultra-compact planetary gear head I've been playing for a direct-drive extruder. The entire gear head fits within the length of the original motor shaft. The trick is that the output shaft, which is nothing more than the filament drive gear itself, rides right on the original motor shaft, eliminating the need for an extra set of bearings. The ring gear is pretty sketchy, formed from just a bunch of holes drilled into an 1/8th" plate and then with the center milled out. The pins for the planet gears are a little marginal too - just the threaded ends of 4-40 screws. However, the torque requirements and speeds are really low so I think it'll go for a long while before it wears out.

I'm using gears salvaged from an old Pittman spur gear head which gave me a 5.875:1 gear ratio. The NEMA 14 motor is 26mm long, and the overall weight for the motor and gear head comes to 160g vs 240g for a 34mm long NEMA 17 motor (about the smallest ungeared motor you can get away with for for an extruder). I need to remake the ring gear to fix some little problems and also need to get a higher torque NEMA 14 motor of the same length, so it'll be a while before I have any extrusion tests.

Cool

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LoboCNC
Here's an ultra-compact planetary gear head I've been playing for a direct-drive extruder. The entire gear head fits within the length of the original motor shaft. The trick is that the output shaft, which is nothing more than the filament drive gear itself, rides right on the original motor shaft, eliminating the need for an extra set of bearings. The ring gear is pretty sketchy, formed from just a bunch of holes drilled into an 1/8th" plate and then with the center milled out. The pins for the planet gears are a little marginal too - just the threaded ends of 4-40 screws. However, the torque requirements and speeds are really low so I think it'll go for a long while before it wears out.

I'm using gears salvaged from an old Pittman spur gear head which gave me a 5.875:1 gear ratio. The NEMA 14 motor is 26mm long, and the overall weight for the motor and gear head comes to 160g vs 240g for a 34mm long NEMA 17 motor (about the smallest ungeared motor you can get away with for for an extruder). I need to remake the ring gear to fix some little problems and also need to get a higher torque NEMA 14 motor of the same length, so it'll be a while before I have any extrusion tests.

Get me a pitch/tooth count etc on that internal gear, and I'll wire you one

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Koko76
Get me a pitch/tooth count etc on that internal gear, and I'll wire you one

Wow, that would be amazing. The internal gear is 78 tooth, 48 pitch, 20 deg. pressure angle. Backlash is not a concern, so having a few extra thousandths of tooth clearance would help compensate for the vagaries of machining abilities. Getting one cut out of 0.125" aluminum plate (at least 2" square) would be ideal, although steel would be fine too is that's what you've got your process tweaked for. PM me if you are really game to cut one and we can swap particulars.

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LoboCNC

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Koko76
Get me a pitch/tooth count etc on that internal gear, and I'll wire you one

Wow, that would be amazing. The internal gear is 78 tooth, 48 pitch, 20 deg. pressure angle. Backlash is not a concern, so having a few extra thousandths of tooth clearance would help compensate for the vagaries of machining abilities. Getting one cut out of 0.125" aluminum plate (at least 2" square) would be ideal, although steel would be fine too is that's what you've got your process tweaked for. PM me if you are really game to cut one and we can swap particulars.

Very little vagary on my end. I chase tenths on the wire all the time. I can thin out the tooth width a little bit though if you like, better than other options. Aluminum stock isn't an issue. I'll get you a pm soon when I'm not at work.