OpenSCAD Spur Gears

by catarina, published

OpenSCAD Spur Gears by catarina Nov 23, 2009
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Even though there are lots of great gears on thingiverse, I couldn't resist the urge to model some too :)

The combinations of parameters are too many to upload an STL for each, so I just picked a few.

I also made a version for helical gears: http://www.thingiverse.com/thing:1339


The openSCAD file accepts parameters for height, pitch diameter, shaft diameter, teeth (number of teeth, addendum, dedendum, tooth width), shape (solid, star, circles), extrude in and out (diameter, height), rome (pitch diameter, gear height, number of teeth, addendum, dedendum, tooth width, rotation).

There is also an option to involute based on pressure angle, but it's not the real thing - I'm waiting for the rest of the http://openscad.org documentation to apply the proper geometry formula here.

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Just taking a look at your very nice OpenSCAD script for gears, and was wondering where the term 'Rome' comes from when applied to gears. Apparently a 'RomeGear' is a co-axially mounted auxiliary gear that is permanently 'welded' to the main gear? I did a number of web searches for 'RomeGear' but didn't get anything useful. Any background information you could provide would be welcome ;-).

Hi Paynterf. Good question! When I did these ( a long time ago) I was also learning about gears. At the time, I found that term used to describe a double gear, but now I can't find the source anymore.

Thanks! I just did some searches for 'double gear' but didn't find anything informative for that either (although I did find some images showing what you termed 'Rome Gears'



Very nice.

One slight snag, though, is how can you print these when you can only save out one STL file with all the cogs? My UP! prints both cogs great, but they are welded together, and the orientation on the bevel gears is not great for the one at right angles.

Normally I can split the STL file neatly int
o parts, but a cog is intermeshed...

Top tip: If you want to make the printed cogs (or any part) far stronger, flood them with cheap superglue and allow to dry. :)

Ok, I found how to split the two cogs so they can be printed easily.

In "module bevel_gear_pair"
look for the line
and change it to something like
and re-render it. Your two bevel gears will now be on the same plane some distance apart.

10 lines before that, you may also want to comment out
ate([0,0,90])" so both gears are on the same axis for printing.


This is an awesome example of 3D Printing technology. :)

This inspired me to look at involutes. I came up with this: http://www.thingiverse.com/thing:3534http://www.thingiverse.com/thi...

Parametric Involute Gear

Hi Catarina,
I was working on a true involute gear OpenSCAD script based on yours and many other gear plugins but I seem to have gotten stuck in getting a true involute curve (using OpenSCAD polygons). If you or anyone else here could help verify my math it would be very appreciated!

my involute gear script: http://github.com/TheOtherRob/MCAD/blob/master/gears.scadhttp://github.com/TheOtherRob/...
(my Gear script is on github but I'll post it here as well once it's working)

Would be nice to specify the inner diameter, or if the shaft are not circular but flat at one side, then that too.

Also there is one more case, when you "fix" the gear to a motor shaft using a nut and a screw in it.

Those are great suggestions, thanks!

oops, the inner diameter is possible. The others are still valid though.

Catarina ! Wow , good work.

You beat me I was going to work on gear sets this weekend , but now I don't have to !


If you're in a mood to model gears, I'm sure there's a lot of work still to be done here :) The involute comes to mind, but there are probably many other things that can be improved and added.

Thanks, gears are fun :) I kept finding and fixing bugs as I generated the models for the prints, but I didn't do any other tests. If you use the openSCAD code let me know about any problems you run into or suggestions you might have. I'd love to get this right as I plan on using gears for a few things.

I totally love this!! congrats Catarina! nice work ;)

Thanks! I tried working out some openSCAD gears myself, but kept running into problems

Those Ikea coasters make a great background too.

i really need to modify thingiverse. there's no 'i love it' option.... ;)

wow wow wow, I am impressed! very nice work!