Gearbox for mechanism or appendage

[Paul Copioli]

This gearbox is known in the industrial robotics industry as an epicyclic gearbox and is very common in robots that require low backlash and high gear reduction.

A couple of business and technical points:

1. There are MANY patents on this design. Several of them have expired but a few key ones still exist so do a patent search before selling this.

2. This design looks to only have one stage going in a single direction. This will induce severe oscillations that cause torque ripple which are detrimental to high load arm applications. There are ways to solve this but it adds significant cost.

3. In order to get acceptable efficiency the oscillating gear must have a very smooth surface finish. Grinding that surface is a must or I would not use it. Plastic gearing for this will severely limit the load carrying capability.

That's all I can think of now.

Paul

[Andrew Duerner]

Michael, I torqued the gearbox unpowered with some lever arms until it broke apart. I would estimate that it reached around 50 ft-lbs.

Adam, I built a website, I'm a mechanical engineer so no making fun of it looking like its from 2004, I need to go through the rules on mentioning trademarked names or just delete them, after I do that I'll post the website address and they can be purchased through the Paypal payment system with a credit card.

Paul, I did some patent searching, I couldn't find anything that the design violated, If you know something in particular that may be a problem I would welcome any information. I haven't experienced oscillations besides having to counterweight the input cam/oscillator. Plastic gears do have their limits, obviously I wouldn't recommend this for an industrial robot, but for FRC robot that needs to run for limited amount of time, I believe it can work.

-Andrew

[Nate Laverdure]

Cool project! Very cool that you'll be able to sell them.


It seems like whenever I talk about 3D printing at work (that's all the time), someone always suggests that I use printed parts to make my own metal castings. It seems easiest to do something like lost-ABS investment casting, taking advantage of ABS's low melting point.

Seems like this would be the perfect project to try this out. Where you have mating surfaces, you could add additional thickness and clean them up in a mill to get closer to the requisite surface finish.

[ajlapp]

These drives are very cool...I've been working to create a useful one for about three years.

I haven't released a unit for FRC because of the immense challenges.

I won't detail them here, but I will tell you that we have a "large" box of failed iterations.

I've attached a picture of a 400:1 unit with a 2.5" OD and an 8mm CIM input.

Here is a video....these are from May 2013.

http://youtu.be/tJoWlCDmaLg

[ajlapp]

I'm in the sharing mood....table of previous design iterations. I've been working on these for a long time.

[Oblarg]

Originally Posted by ajlapp

These drives are very cool...I've been working to create a useful one for about three years.

I haven't released a unit for FRC because of the immense challenges.

I won't detail them here, but I will tell you that we have a "large" box of failed iterations.

I've attached a picture of a 400:1 unit with a 2.5" OD and an 8mm CIM input.

Here is a video....these are from May 2013.

http://youtu.be/tJoWlCDmaLg

Very cool. If these ever came on the market, I'd definitely be interested. Way more compact than a planetary.

[Lil' Lavery]

I've been toying with the idea of a cycloidal gearbox for FRC manipulator applications for a while, but haven't had the time or resources to really get very far. It's exciting to see other people running with the idea, and that they have managed to get a lot further.

[Andrew Duerner]

Sorry I haven't responded this past week, I decided to write a provisional patent for the gearbox in case there was something worth protecting. It took a lot more work than I thought to get it all written out. Interesting learning experience, I would recommend students interested in design to write a mock or real patent. With a provisional being only $65 to submit, it's really not very expensive.

I also got the website updated. You can find a little bit more info but the really important things aren't nailed down yet, max torque, weight, etc. Check it out at www.armabot.com.

That is an awesome video ajlapp. Such a small form factor for a 400:1. Are you going to keep working on it?

[s_forbes]

Very cool stuff! I've been reading papers about these things and playing with designs for the past few days, I really want an excuse to build one.

Originally Posted by ajlapp

I won't detail them here, but I will tell you that we have a "large" box of failed iterations.

Great looking gearbox. I'd love to hear more details on what kind of failures you ran into when going through different designs. I suspect that you need pretty tight tolerances on all of the parts so you land somewhere between "too tight to assemble" and "tore itself apart".

For the ABS approach, I like the idea of cheap printable parts that can be remade when they wear out. We've seen the need for high reduction/low load gearboxes in the past where something like this would work. If we don't need to replace it every few matches, then it might be worth it (entirely depends on what it's being used for).

[Paul Copioli]

All,

You want to learn about the kings of the industry for this technology? Go to this site:

http://www.nabtescomotioncontrol.com/engineering.php

They absolutely dominate the industrial robotics market. FANUC, ABB, and Motoman all use this gearbox for their main arm joints. I have first hand knowledge that there are at least three of these bad boys (RC-E or RV-C depending upon the need) on each general purpose FANUC robots.

They have cool videos and detailed cross sections of these products.

Why would they do this? They have pretty much all of the patents on this stuff. Many of them are expired, but some of them are still very active.

Anyway, this is the place to go to learn about the best use of Cycloidal gearboxes.

Paul