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Harmonic Drive

by Alphie, published

Harmonic Drive by Alphie Jul 11, 2014
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Harmonic Drive by Alphie is licensed under the Creative Commons - Attribution license.

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7093Views 1274Downloads Found in Robotics

Summary

My goal was to implement the principle of the harmonic drive into a sturdy solid module that can ultimately be used for making a robotic arm. This is my first prototype, and it works quite nicely.
http://youtu.be/D_neLbcW_BY
The circular spline has 84 teeth. The flex spline (80 teeth) has been printed with flexible PLA. All other parts were printed with regular PLA. The bearing balls are made of copper and are 3.2 mm in diameter in size.
The large bearing needs some work to get a good fit. It is currently too tight when 100% filled with bearing balls.
Print settings (ultimaker)
-0.1 mm @ 25-50mm/s
-nozzle (0.4 mm) temp 225 degC
-bed: 65 degC
-0.1 mm @ 25-90mm/s depending on structure (25 for gears)
Have Fun!

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Hi, your design is really amazing!

I need to design a robot arm, and it may include a harmonic drive. Do you have any suggestions that I can learn to design a good harmonic drive like you by myself?

Thank you very much!

Jun 21, 2016 - Modified Jun 21, 2016

Hi Alphie,

I think I found a "critical" error. Your circular spline got 83 teeth instead of 84 teeth. Could you correct this please?

However, great design! I am trying to print the flex spline in PETG at the moment to improve the torgue translation compared to flexible filaments. Works great so far, apart from the 83 teeth problem ;)

Thank you!

You have printed and tested one of these?

Any chance you would release the Autodesk source file here Alphie ?

What type of flexible PLA did you use? TPE?

Oct 31, 2015 - Modified Oct 31, 2015

Thank you for your comments! In regard to your questions:

Haywire: The bearing balls came from a dutch webshop and were sold as "magic vase cleaner". Unfortunately this product was discontinued. If you use bearing balls (look for a local bearing shop) with a diameter around 3.2 (e.g. 3.175mm) it should also be ok.

Jstaud: The reduction ratio is 1:20. Each rotation of the wave generator shifts the flexspline by 4 teeth.

joshuanapoli: I use Autodesk Inventor to generate the teeth profiles. I can highly recommend this tool!

Thanks again for your interest!

Where did you get the balls for the bearing from

What is your gear reduction ratio on this particular gearbox?

Can you suggest a reference on how to design the splines, clearances, etc.?

Good job! Will keep an eye on your work!

Thank you for your comments. I tried to adjust the bearings but 6mm diameter BBs are a bit too large for the smaller bearings,
I will keep this in mind so future designs have enough room to accommodate two sets of bearings, 3.2 and 6 mm.

Think you could release a modified version using 6mm BBs as bearings due to ease of availability?

Thank you for your comments. I tried to adjust the bearings but 6mm diameter BBs are a bit too large for the smaller bearings,
I will keep this in mind so future designs have enough room to accommodate two sets of bearings, 3.2 and 6 mm.

Nice job...
Also working on robotics joints.
Many thanks for sharing

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