1379:1 Compound Planetary Gearbox

by Gear_Down_For_What Apr 2, 2017
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what resolution and infill did you use?

We just finished printing a set of these. Can you show your math on the gear ratio? We are trying to verify it but can't seem to come up with it.

Something like this

 FinalRatio = 1 / ((((TR2 -((TR1/TP1) *TP2))/TR2) * (TS1/(TR1+TS1))))

Just printed one and it turned out great after I scaled down the sun gear to 85%. To be honest, it's still a little tight and I might scale down the planet gears by a bit as well. Props for the design!

Can you explain how you calculated the 1379:1 gear ratio? It's not very apparent. Thanks!

Have you done any testing on how much backlash you get? Specifically: How much/far can you wiggle the output arm before it "locks"? Just wondering if it would be usable for a SCARA bot of some kind. Either series or parallel.

The output generally has a couple of degrees of play once you wear in the gearbox. This gearbox isn't really designed for torque, but I have a 160:1 that has amazing torque capabilities and almost 0 backlash.

I may be wrong, but I think the #2 gear file is missing. This is the gear that goes between the 3 planet gears before the output ring gear goes on.

Your right! I have no idea where my files keep going to but this has happened before... I unloaded it from my phone so just make sure it looks okay, I can't check it from a computer right now.

Got it! Thanks again.

I'm printing the gearbox to use as a display in my office. Are there any build instructions available. I'm not able to see the whole model from the pictures you provided. TIA.

Yeah I did assembly in the video where it says 2 in series.

Thanks for the fast reply. I'll check out the video tonight.

I just created this, but it didnt worked. It was very hard to add everything together.
Even when I complete the puzzle it was so tight that impossible to move.
Can you check the files?

Did you have any first layer squash? That's usually the issue I have that causes problems.

I checked for twice it seems there are no problems. I tried to scale down sun gears to 0.85 that created some relaxation, but it didnt fixed still it is very hard to turn.

Did you scale them down in two directions only?

If you make change the scaling in the Z direction it will make them shorter and the teeth won't line up

I scale down in all coordinates. I am printing in 0.2mm resolution. Can it be the problem?

Yeah you can't scale it down in all directions. Your actually making the gear shorter and increasing the helix angle if you do that.

Scale the planet gears or the sun gear down in only the X and Y directions.
And printing at lower layer heights can also help.

Your real problem is likely to be a horizontal expansion setting or flow setting.

Hello I check that if I just scale down in X and Y directions the helix angle increases.
I think I should do that in all directions (X,Y,Z) to have same helix angle?

I will try to focus on those:
And printing at lower layer heights can also help.

Your real problem is likely to be a horizontal expansion setting or flow setting.

Yes I know theres something wrong with my scaling logic there. I don't quite get it either but I have had more luck scaling in only the x and y directions than I have scaling in all directions

Thank you so much! I will try and let you know if it works :)