Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Compact Planetary Gearbox

by raldrich Apr 6, 2012
Download All Files

Thing Apps Enabled

Please Login to Comment

looks great thanks for sharing.

Can you post the design for just the bottom part?

The vitamins list on the Instructions were difficult to read so here they are reformatted for legibility.

3 M3x12 Socket Head Cap Screw
4 M3 Nut
1 M3x6 Set Screw
4 M3x35 Socket Head Cap Screw
1 M8 Hex Head Cap Screw or 1 M6 Hex Head Cap Screw
2 608ZZ (8x22x7) or 126ZZ (6x12x4) Ball bearing.
1 M8 or M6 Nylok Nut

Are you sure the gear ration computation in your files are fine?

Gear Ratio are supposed to work like that vs your

your 4.44 ratio:
drive gear teeth (9)
small gear (11)
ring teeth (31)

Ratio should give 31 / 9 = 3.44
Overall ratio: 11/9(1.222) * 31/11(2.81) = 3.44

your 4.2 ratio:
drive gear teeth (10)
small gear (11)
ring teeth (32)

Ratio should give 32 / 10(drive gear) = 3.2
Overall ratio: 11/10(1.1) * 32/11(2.91) = 3.2

your 4.0 ratio:
drive gear teeth (10)
small gear (10)
ring teeth (30)

Ratio should give 30 / 10(drive gear) = 3.0
Overall ratio: 10/10(1) * 30/10(3) = 3

your 3.8 ratio:
drive gear teeth (10)
small gear (9)
ring teeth (28)

Ratio should give 28 / 10(drive gear) =2.8.
Overall ratio: 9/10(0.9) * 28/9(3.11) = 2.8

your 3.66 ratio:
drive gear teeth (12)
small gear (10)
ring teeth (32)

Ratio should give 32 / 12(drive gear) =2.66
Overall ratio: 10/12(0.83) * 32/10(3.2) = 2.66

Unless they are something I don't understand, it's like you are offset by 1 :)

Thank you for clarifying this!

The formula for computing the gear ratio of this sort of planetary gearbox is (R+S)/S, where R is the number of teeth in the ring gear, and S is the number of teeth in the sun (drive) gear, so (9+31) to 9, or 40 to 9, or 4.444 to 1.

Ok thank I just started to read about it and the formula is different from a standard gearbox lol

Yeah, it's because the output is taken from the planet gears, rather than from the ring gear.

I've put a newer design up on youmagine - https://www.youmagine.com/designs/differential-planetary-gearbox

The math for it's gearing is even more complicated ;-p

Looks fantastic, I updated some stuffs related to ball bearing, a little bug that I found and added few thing like with_extruder = false :)

I still have question about your new design related to bolt hole that seam to be fuckup, like the hole is not really an hole from openscad and on the other side its like an inverse hole, so basically no screw can pass on it, few object have this like carriers and top cover, what is that exactly?

UPDATED: it seam to be related to support = 1, what does this option?

UPDATE AGAIN: I think I understand now, its for like make bridge on the bolt head section since no slope to it, maybe with a little slope (cylinder with 2 radius) can handle this, but the bolt head will not touch on a flat surface...

When making a recess for a bolt head (or a nut trap) on the underside of an object, you need to give a way for the extruder to bridge the point where the hole narrows. In older designs, I would have used a thin sheet there, but I've found that actually putting a post up the middle gives better results.

You just break the post out, and it leaves a clean hole for the bolt head or nut.

Great, I will take a look, why you switched over youimagine?

I've switched to youmagine because of Makerbot's attempts to patent public domain inventions, and because the terms of use for thingiverse assign rights to MakerBot outside of the license chosen for the design. google "makerbot patent controversy" and "occupy thingiverse".

plz make a extruder with it PLZZZZZZ

Hi! I like your design, but when I try to recompile using Openscad and the m5_bolt_output all the holes vanish....
Any Idea? or better yet, could you compile an stl with M5 output bolt?

i would love to see this as well.

Hi whenever I try to re export from OpenScad I get this message
Current top level object is not a 3D object.
any ideas?

I just tried rendering it using OpenSCAD version 2013.06 on a Mac. It worked, but it also showed a bunch of warnings of the form

"WARNING: Duplicate vertices and/or intersecting lines found during DXF Tesselation."
"WARNING: Modify the polygon to be a Simple Polygon. Render is incomplete."

These warnings are probably appearing when it generates the gear teeth, and didn't appear in older versions of OpenSCAD.

I didn't get the "Current top level object is not a 3D object." error, and the resulting STL appears to be correct.

Could you make one with mounting holes for the standard planetary setup? (Like holes that line up with http://www.thingiverse.com/thing:38069)http://www.thingiverse.com/thi.... Then you could use it with existing planetary geared extruders.

Appears to be a 20mmx20mm square. Not sure how you'd do nut traps on the opposite side though.

Airtripper Variant for Planetary Gear Stepper, 8mm MK7 pulley and M5 PushFit

Actually, 21mm square. The problem is that the drive shaft on this design needs to be supported at the end, with a bearing and a nut, so using it on an existing extruder design wouldn't work.

The way to approach it is with an extruder head that replaces the cover. I had one working, for a day or so, but after breaking the sun gear twice, I decided that I'd do better to buy a motor with a metal gearbox.

I printed it and it works as my extruder for quite while now no cleaning at all nozzle J head 0.35mm sliced in kisslicer printed in PLA on prusa mendel, extruder is using YRU hobbed bolt type, right now I'm working on my own planetary gearbox because this one is too long and a bit to fragile while i can use box like 60x60mm it has to be shorter. Overall great design

I would love to see some devices and extruders that incorporate your planetary gearbox :)

Slic3r 9.7's ability to fill narrow areas makes me think this could be printed and made strong sometime in the near future :)

hey i just built my own 3d printer, and even with a .35mm hot end, the sliced profile comes out with the planets only being 1 perimeter thick. is there any way you can seperate the pieces, so i can experiment, with different slicing profiles for the planets?

raldrich_planetary.zip includes complete openscad source code, which you can modify to tweak and output individual parts.

Also, slic3r has the ability to separate the components of a plate.

wow learn new things about this stuff everyday, all it said was spl in slic3r, instead of split, anyways what settings should i use to slice it?

ok i tried to split it, but it appears there is some sort of error, like maybe a hole in the mesh somewhere, i get this error 

11:25:12.343 : <slic3r> Use of uninitialized value in array element at C:/PROGRA~1/Repetier-Host/Slic3r/lib/std/Slic3r/GUI/http://Plater.pmPlater.pm line 1024.</slic3r>

I guess you'll have to fall back to editing the .scad file in OpenSCAD

could you please just upload the parts seperately, i have no idea how to use openscad other than adjusting some of the settings. i would really appreciate it.


Did you finally build a complete extruder based on this design? I would be interested...


I found that the motor's shaft tended to make the sun gear too weak to drive an extruder, at least with the state of slic3r at the time.  After shattering the sun gear twice, I finally ended up buying a surplus motor that had a planetary gearbox built in to it.

Ok, I see. Thanks.

I printed it and it worked perfectly straight away with no cleanup.

I have one currently on the extruder of my 3d printer and it has performed flawlessly. I printed it out of ABS .

It completed a 13 hour print with no problems.

Best and most practicle thing I have ever found on thingiverse.

Thank you for designing such a great thing!!!!! Awesome

Printed this last wkd. Looks and works great. I print with a larger 3D printer and printed this in Nylon 6/6 because it's very slippery and will require no lube.


I hate to be the only idiot to ask this, but... how do the printed pieces actually go together? I have some theories, but i would hate to assemble it wrong and break something in the process (it was a solid 8 hour print... seems to have worked fine on the first go though).

Install the output bolt into the top of the planet frame. install the planets into the bottom of planet frame. Attach the bottom of the planet frame to the top frame using M3x12 screws and nuts.

Install the bearing into the cover. Run the output bolt through the cover. Insert the planet frame into the annulus (ring) gear, aligning the teeth of the gears.

Attach the sun gear to the motor.

Attach the gearbox to the motor using M3x35 screws, making sure that the teeth on the sun gear are
aligned to the planets, and that the sun gear has adequate clearance.

Thanks, i was being stupid. I did eventually figure it out (though wasn't sure about hte bearings)

However i was playing around with the openscad, and was trying to print out a sun gear with a smaller bore for the motor input. However it just doesn't want to print the sun gear's gearing! Always comes out smooth. It will work fine if i increase the number of teeth to 11 or higher... but of cours
e that screws up the size and ratios. Have you notice this problem before (seems to be something openscad doesn't like, i cant even import your already rendered sun gear stl)?

You might want to check to see that you're using the latest version of OpenSCAD.

Wow that is spectacular. I have been chewing over ideas for this sort of thing for a long time. Principlay for a revised extruder. An here you have done it. You are truly a star. 8-)

News on the planetary extruder front:

The prototype finished a 6 hour print last night, but managed to break the sun gear today.

I may have to increase the housing size to 50mm in order to beef up the gears.

More news:

I've been able to produce a stronger sun gear, by tweaking the diametral pitch of the gears so that the inner and outer extrusions between the gear teeth and the bore are touching.

Unfortunately, with the current version of slic3r, this ends up making the model be very slicing settings dependen
t, and I suspect that a .5 nozzle version with the same gear ratio may be impossible.

I printed a set with a 0.5mm nozzle and ABS, using Cura slicer. It gives very good precision on small stuff.
I used 0.28mm layers. Next time I will select 0.24mm layers. Slic3r doesn't seem to handle small accurate detail as well as Cura.
You need the settings so that it has at least 3mm walls so that all the gears teeth are fully formed.
I am using Repetier for the printing. Never tried anything else.
I intend to make a sun gear in nylon, or even a full set of parts. Pretty weed eater cord.
With ABS make sure you lubricate the spigots on the planet carrier else they can seize.

Cutting it up into component parts? Open stl with solidworks and delete the parts you you don't want and save individually.

Hmm, don't believe its possible to print this using slic3r and a 0.5mm nozzle.

Reason being no matter how i slice it, the planet gears are only 1 wall thick, as theres insufficient space for 2 walls. As such it doesnt really work since theres a huge gap in between the wheel hub wall and the sprockets.

Problem fix with

planet_shaft_diameter = 5;

instead of 6.

I had picked 6mm simply because in one design I had 3mm bolts running up the insides of the planetary shafts. 5mm should work just fine.

Printed it. Because it was cool. No other reason.

This printed out great for me on my TOM mk6. I will mount it on a stepper today and upload a photo.

Thanks for this thing!

I'm a little confused by the bearing that is supposed to go inside the case, there doesn't seem to be room for one.

If you look at m8_output.stl, you can see a 608ZZ sized divot in the inside of the cover - note that the cover is printed upside down.

m6_output.stl has the original divot, for a 126ZZ bearing.

Very awesome! I printed mine all in one go. I had to clear out the insides of the small gears with a 6.5mm drillbit, but the rest went together smoothy. I didn't have the M6 bolt, or MR-126 bearing, so I couldn't construct the output side, but everything else moves smoothly. Nice job!