Active Ball Joint Uses Spherical Gear

A common CAD operation is to take a 2D shape and extrude it into a 3D shape. But what happens if you take a gear and replicate it along a sphere and then rotate it and do it again? As you can see in the video below, you wind up with a porcupine-like ball that you can transfer power to at nearly any angle. There’s a paper describing this spherical gear as part of an active ball joint mechanism and even if you aren’t mechanically inclined, it is something to see.

The spherical gear — technically a cross spherical gear — is made from PEEK and doesn’t look like it would be that difficult to fabricate. There’s also a simpler version known as a monopole gear in the drive system that provides three degrees of freedom.

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Dainty Delta Is About As Small As A Robot Can Be

There’s something mesmerizing about delta robots. Whether they are used at a stately pace for a 3D-printer or going so fast you can barely see them move in a pick and place machine, the way that three rotary actuators can work together to produce motion in three axes is always a treat to watch. Especially with a delta robot as small as this one.

[KarelK16] says this is one of those “just because I can” projects with no real application. And he appears to have been working on it for a while; the video below is from eight years ago. Regardless, the post is new, and it’s pretty interesting stuff. The tiny ball joints used in the arms are made from jewelry parts; small copper crank arms connect the three upper arms to micro-servos. The manipulator [KarelK16] attached is very clever, too – rather than load down the end of the arms with something heavy, a fourth servo opens an closes a flexible plastic grasper through a Bowden cable. It’s surprisingly nimble, and grasps small objects firmly.

There are certainly bigger deltas – much bigger – and more useful ones, too, but we really like this build. And who knows – perhaps model robotics will join model railroading as a hobby someday. If it does, [KarelK16]’s diminutive delta might be the shape of things to come.

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