# 43.33:1 Compound Planetary Gearset, NEMA 17 Mount, No Hardware

Feb 4, 2017

### Thing Apps Enabled

Hi I'm new to this type of gear. If I wanted to print this using only 2 of the sections. Would it still work it just fall apart on me? I understand some of the parts like the sun gear are full length but I can tweak that in mesh mixer. For my application backlash really isn't an issue. But I do need torque. So maybe using all 3 sections would be wiser. Just some input would be appreciated. Thanks.

Any tips for assembling this?

I am designing something similar that uses compound planetary gears and I have a question. I realize the planets are locked and rotate in unison. My question is are the sun gears also locked and rotating in unison or do they rotate independently and at different speeds?

The sun gears need to rotate at different speeds

Thank you. That is what I thought (and experienced) but wanted confirmation. I think there might be a ratio of gears that allows for synchronization. Will go through the math eventually...

I've done just that (http://www.thingiverse.com/thing:3511382 ), some time later. If you want the sun gears to rotate in unison, it means they must have the same number of teeth as the planets (or be some multiple thereof) ie. S1=nP1, S2=nP2, but this is incompatible with R=S+2P constraint and you won't find any valid combinations which also satisfy the even spacing constraint.

However, if we relax this constraint by allowing a few teeth to drop from the ring gear and adjust the profile accordingly, we can stretch it to mesh. Take for example S1=P1=13, S2=P2=15, R1=38, R2=45 - this almost satisfies R=S+2P but R1 has 1 tooth fewer. S+R still divides by 3 planets for even spacing. This gives a ratio of 153:1 with a common sun gear all the way through. I've also made a rough spreadsheet calculate possible combinations from 10-20 and 30-60 teeth, filtered on how many teeth we need to lose.

Solid Core Compound Planetary Gearbox (customizable)
by tmackay

I'm getting non-manifold errors with Slic3r Ver 0.9.9 on the four planet gears and the three sun gears. Print them anyway?

I don’t know what to say. I use cura and I never got that kind of error.

how can I get the ring to be at 22.6:1, then the second would be 512:1 and the third 260,800:1?

can this be put in the middle of a direct drive extruder ? if so, wich tweaks will be necessary?

it will be nice see this design as a stackable reductor for improving direct drive extruders found in most printers

Should work, I wouldn't suggest using this version of it though, the one for the robotic arm project has much less backlash.

Might be a little bulky too but you could possibly scale it down

If you build this make sure to scale the outer ring gears to 102.3%, and the retaining rings to 103%. I printed it the first time and it was way too tight. I'm pretty sure it's not my printer because the gears were actually slightly under extruded.

I printed it without scaling from PLA and have opposite problem, I'd welcome a tighter fit.

Keep in mind that if you scale it, it won't fit in the mount

On a side note, keep in mind that print speed and your jerk settings can cause the printer to make the gears bigger than they should be.