Cool Harmonic Drive Animation

Came across this YouTube video today. Thought I would share it.

YouTube

gm

Interesting! Not sure what it would be used for, but interesting.

steve45 said:

.... Not sure what it would be used for, ...

Click to expand...

Robot joints, high precision A,B,C axis on your machine tool.
Bob

I saw a lot of those being used when I worked on control systems in the printing industry. Precise additive or subtractive rotational displacement made controlling possible in a compact and efficient way. The video didn’t show the effect of adding rotational motion into the outer cage. There were Epicyclic and others that used chains. I was more of an electronics guy but am fascinated by the engineering smarts that go into mechanical things. If I only was good at maths!...

Nice, thanks for the link, I've never understood those before

That was pretty cool. Thanks for sharing.

In printing it's used in the registration control. You need precice control when advancing or retarding a printing unit to align/register print to the previous printing unit.
Otherwise with slop in drivlines print drifts back and forth and colors dont stay in registration.

Seems like it would just be wobbly.

I came across it while researching ideas on building my own rotary indexer. Bob Warfield has this page (CNC 4th Axis Basics: How They Work - CNCCookbook: Be A Better CNC'er) on his site where he mentioned it. Guess I'm on the hunt for one now!

GregSY said:

Seems like it would just be wobbly.

Click to expand...

The elliptical center (driven) would have to stay concentric on a shaft bearing. the wobble is going on in the flex spline (center ring)
The inner and outer would be held concentric but rotate. I hope I'm saying and seeing that right.
I deleted a leadscrew brain fart idea I had.

So I'm taking it this setup is good for 6 RPM but not so hot for 6000RPM?

The input shaft and the output shaft or assembly run on their own bearings so it is not wobbly at all.
In fact it needs to be designed to be very stiff and runouts have to be held very, very tightly or the thing won't run at all.
There is a cyclical error that is both built in and dependent on mounting.
They come in varying low lash numbers and zero lash.
Gear reductions are high on the typical on the order of 1:100 to 1:300 so 6000 out would need a lot of speed on the input side.
Designing for adequate long life lube can be a problem.

These are expensive. You can find them on E-yuk new both packaged and open but the array is bewildering.
A alternative used more and more are things like megatorques or Direct Drive Rotaries which are very high pole count motors. These also have the same type speed limitations with somewhat higher top end.
Generally the harmonic has better dynamic stiffness but with much added complexity.

As noted used on printing presses for alignment but these are "timing units" and a tad different.
On a robot the outboard end may be 3 to 6 feet away from the rotation joint so you need huge reductions and stiffness to place that tip anywhere near the right spot.
On grinding workheads it is sort of the same deal.
Designing this drive system into a low profile rotary table would be a challenge.

A walking spring steel ring. Kind of slick.
Bob

These units seem to have wide range of applications including all of what Carbidebob talked about. It is a timing process keeping six printing units in registration.

Harmonic phasing device for printing press - Didde Graphic Systems Corporation
Abstract:

A dual harmonic gear phasing device forming a part of a web-forming printing tower or other web-handling station is disclosed which allows static or dynamic, 360° infinite phase alterations of web-contacting rollers for coarse and fine tuning of the registration of a multiple-station printing press. The phasing device comprises an enclosed, oil filled structure having a pair of tandem coupled harmonic drive gears respectively connected through gearing or the like to the press drive and to a desired roller for phase changing purposes. Each phasing device also includes a selectively operable stepper motor coupled to one of the harmonic gears for effecting phase alterations. The harmonic gears serve as a 1:1 gear ratio transmission during normal running operations. The phasing device can be used on hard impression or perfecting printing towers, and on other types of web-handling equipment where proper registration is important, such as numbering and punching units.

Harmonic drive is used on the power quill feed of the Bridgeport series II machine....Not for timing it seems but to give a gear reduction for the drive motor in a very small space.
Cheers Ross

We advanced or retarded the print unit by holding down a momentary button depending on how far the print needed to move. 1/16" 2 seconds. Longer shorter depending on how far the move. You just had to learn how long to hold the button. Now in reading i see its all laser read and the adjustment is made. They take all the fun out of running machinery. Humans are going to become less capable.
I'm sure its now quicker more accurate with less waste.

GregSY
I remember running 600feet per minute and down. We ran in feet per minute or impressions per minute. RPM's. ?