Cycloidal gear profile

[maximumcoolbeans]

I'm designing a bi-cycloidal drive like the one shown here:

(mesmerizing eh?) Bi-cycloidal drives like this include both a male cycloidal gear and a female cycloidal gear. The male cycloidal gear can be considered the sun gear, where the pins are radially outside of the cycloidal gear, and the female cycloidal gear can be considered a ring gear, where the pins are radially inside of the cycloidal gear (the pins are integrated into the eccentric gear in the bi-cycloidal drive above). The tooth profile equations for male cycloidal gears are provided at these two sources (https://stepbystep-robotics.com/hp/robots/cycloidal-drive/ and https://uwaterloo.atlassian.net/wik...427/Cycloidal+Drive+-+Rev+1+Prototype+Journal). Do any of you know where I can find the tooth profile equations for a female cycloidal gear? Any help is appreciated, thanks.

 

[mfgenggear]

Here are some books that may be relevant to cycloidal gear profiles:

• Handbook of Practical Gear Design
  A detailed guide to gear technology that covers the design of all types of gears, from small mechanisms to large industrial applications.
  
  
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• Asymmetric Gearing
  A book by Dr. Alex Kapelevich that summarizes his knowledge on asymmetric gear drives.
  
  
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• Elements of Mechanism
  A book by V. L. Doughtie, P. Schwamb, A. L. Merrill, and W. H. James that includes information on cycloidal gears.
  
  
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• Analytical Mechanics of Gears
  A book by E. Buckingham that includes information on cycloidal gears.
  
  
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Cycloidal gears are often preferred in horology because they can be designed to have only one or two points of contact, which reduces friction. They are also stronger than involute gears for the same pitch, and they are less likely to wear out.

 

[mfgenggear]

OP
The issue with cycloidal gears is all the gear shops are tooled for involute gears. How are you planning to manufacture them. Prototype or production.

 

[maximumcoolbeans]

@mfgenggear Thanks for the recommendations. I downloaded the "Handbook of Practical Gear Design" and went through all the control+F results for "cycloid" and didn't find what I was after. Let me know if you have other suggestions.

About manufaturing, CNC milling seems like an option for prototyping and manufacturing. There are no sharp corners at the root of the teeth, unlike conventional involute gears.

 

[mfgenggear]

OP
Wire cnc would be more precise

Cycloidal Gear Calculator

 

[Doug Hunter]

How many units are involved in prototype and production? If you need > 100, then Powder Metallurgy becomes a good option to consider, as you'll be near the breakeven point for tooling cost. Wire EDM is also a process to consider in low volume (perhaps that's what Mfgenggear meant by 'wire CNC').

 

[maximumcoolbeans]

Thanks for the suggestions!

@mfgenggear That calculator appears to be for pairs of cycloidal gears but the type of gear that I'm interested in is a bit different: https://en.wikipedia.org/wiki/Cycloidal_drive.

 

[mfgenggear]

In 30 years plus I never in countered cycloidal gears for gear box application, and never seen it used in automotive and motorcycle applications. Don't know.
But conventional involute gears work for high torque. And rpm aerospace application with very high horse power. Just saying.

 

[maximumcoolbeans]

I suggest you do a bit of reading about cycloidal drives if you're unfamiliar with them (see the wiki link above).

 

[Doug Hunter]

Cycloidal drive: very interesting... I did not know about these.

 

[mfgenggear]

OP
I am sure cycloidal gearing has its use.
Just like harmonic drives . And is an other bag of tools for the designer. What meant to add, and suggest it's not as common. As involute gearing.

 

[Doug Hunter]

I'm likewise sure that involute gearing is much more widely used. The Cycloidal Drive appears to have the advantage of large gear reductions with lower gear count and space. I think that traditional involute gearing would require a couple stages of planetary systems to get this kind of reduction. I'm also wondering now if there's a way to implement the same orbiting principle as the Cycloidal Drive except with involute gears instread of cycloidal?

 

[mfgenggear]

Harmonic drives also have a high reduction and are used in robotics. Very low back lash and precise movement and are as well very good. Except at low rpm.
Cycloidal gear to my knowledge have the same issues. Very good at low RPM with high reduction.

 

[maximumcoolbeans]

@Doug Hunter This video touches on that topic of involute vs cycloidal teeth in a cycloidal drive:

From this paper: "In an ideal cycloidal drive, all roller pins contact the cycloidal gear, and about half the roller pins bear the load." I'm not sure if this distributed load bearing is possible with involute teeth. It seems like cycloidal teeth are important for acheiving the low backlash, low noise, and high impact resistance of cycloidal drives. But I would like to learn more about this topic and about other possible tooth profiles in cycloidal drives.

 

[mfgenggear]

These are results for why are cycloid gear so expensive

Cycloid gears are expensive primarily due to their complex design and precise manufacturing requirements, which necessitate specialized tooling and machining processes to achieve their key advantages like extremely low backlash, high torque capacity, and compact size, making them more costly to produce compared to standard gear types.
Key factors contributing to the high cost of cycloid gears:
Complex geometry:
The cycloid tooth profile is not a simple shape, requiring intricate machining techniques to accurately create the necessary curves and contact points.
High precision needed:
To maintain the low backlash characteristic, tolerances in manufacturing must be very tight, which adds complexity and cost.
Specialized materials:
Some cycloid gear designs may require high-quality materials with specific properties to withstand high loads and wear resistance.
Multi-stage assembly:
Cycloid gearboxes often involve multiple components and precise alignment, adding to the assembly time and cost.
Limited market demand:
Due to their niche applications where extreme precision and low backlash are critical, the production volume of cycloid gears is often smaller, leading to higher per-unit cost.
Benefits of cycloid gears despite the cost:
Minimal backlash:
Cycloid gears can achieve virtually zero backlash, crucial in applications requiring high precision positioning.
High torque capacity:
Due to their unique design, cycloid gears can transmit significant torque in a compact package.
Long lifespan:
The high contact area and low wear characteristics contribute to a longer service life.
What makes cycloidal gearboxes so amazing? - YouTube
Jul 31, 2023 — so a cyclical gear set could have two gear ratios in one another cool thing about cyclotal drives is they can't be back driven. ... another benefit ...


lifetime. Higher rigidity. More compact design. Lower weight. Higher overload prote...

Wikipedia
(PDF) Design and Development of Cycloidal Gear Box - ResearchGate
Jun 26, 2024 — Advantages of the cycloidal gear over normal gear are as follows: * • More robust construction. * • Virtually backlash-free for the whole lifetime ...

ResearchGate
Planetary VS Cycloid White Papers - Nabtesco Motion Control
Cycloidal Gears work at higher ratio's allowing them to be driven with less power. Planetary Gears are good if positioning accuracy and lost motion are not a co...

Nabtesco Motion Control
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Reddit · r/robotics
20+ comments · 4 years ago
[Q] Are harmonic or cycloidal gearboxes better for a desktop robotic arm? What are ...
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Harmonic drives aren't complicated, per se - in fact, they are remarkably simple if you ...
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What are the disadvantages of cycloidal gears?

Disadvantages. Due to the eccentric nature of the drive, if the cycloidal disk is not balanced by a second disk or a counterweight, it will generate vibrations which propagate through the driven shafts and the body. This increases wear on the exterior teeth of the cycloidal disk and the component bearings.
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Engineering Stack Exchange
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Worm drive vs Cycloidal Drive
Oct 31, 2023 — In robotics, I've seen quite a few people make use of cycloidal drives. They seem robust, compact and have a relatively simple design, while still achieving ...
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Wikipedia
https://en.wikipedia.org › wiki › C...
Cycloidal drive
A cycloidal drive or cycloidal speed reducer is a mechanism for reducing the speed of an input shaft by a certain ratio.

Chief Delphi
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Cycloidal Gearboxes, a game changer? - Technical Discussion
Jun 10, 2015 — I kind of love cycloidal Gearboxes, they're a similar concept to a harmonic drive but without having to worry about the flexible spline.
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YouTube · 3D Printer Academy
78.9K+ views · 1 year ago
What makes cycloidal gearboxes so amazing?
4:33
... high tech 3D printer: https://amzn.to/44LESTx - Browse files ... A cycloidal gear drive CAN be back driven. Yours was just not smooth ...
4 key moments in this video
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What is the major reason for using involute gears over cycloidal gears?
What is the major reason for using involute gears over cycloidal gears?
The major reason for using involute gears over cycloidal gears is the ease of manufacturing ...
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An involute gear is great at transmitting power, with a very high efficiency. It can be ...
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1 vote
Better performance comes from the fact that there is always rolling contact between ...
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Involute tooth profile is almost used generally everywhere and given preference over cycloidal ...
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Involute Gear Profile: • Pressure angle remains same throughout the operation. • Teeths ...
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Nabtesco Precision Europe GmbH
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Cycloidal gears versus planetary gears
Cycloidal gears deliver better performance in every respect. They have a more robust design than planetary gears, which means they also last longer.
Missing: so ‎| Show results with: so

Transcyko
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Planetary vs Cycloidal Gearboxes
Mar 8, 2023 — Although a cycloidal gearbox is more durable and can resist very high torque loadings, it is not able to transmit as much torque as a planetary ...

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Nov 13, 2020 — I also suspect that due to my ring and cycloid gear both being plastic, there is a good amount of deformation between the two when put under ...
Images
What makes cycloidal gearboxes so amazing?
What makes cycloidal gearboxes so amazing?

YouTube
Harmonic vs Cycloidal Drive - Torque, Backlash and Wear Test
Harmonic vs Cycloidal Drive - Torque, Backlash and Wear Test

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Cycloidal Gearbox Explained - How does it work?
Cycloidal Gearbox Explained - How does it work?

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How does a cycloidal gearbox work? | Structure and function simply explained | parametric equation
How does a cycloidal gearbox work? | Structure and function simply explained | parametric equation

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