3D Printed Rigid Chain Mechanism

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One of the major advantages of 3D printing is the ability to quickly test and then iterate on mechanical designs. [gzumwalt] does a lot of this, and has recently been working on various versions of a rigid chain mechanism. (Video, embedded below.)

A rigid-chain mechanism is one way of fitting a long beam into a small box. It works similar to a zipper, meshing two separate “chains” with specially teeth designed to form a rigid beam. Due to clearances between the teeth, the beam tends to be a bit floppy. [gzumwalt] made various sizes of the mechanism, and also reduced the clearances on later versions to reduce the flop. He also integrated it into a cool “snake in a basket” automaton (second video below) by adding a reversible gearbox and a binary snap-action switch.

One possible use for this type of mechanism is for autonomously assembling long structures in space, as one of the 2017 Hackaday Prize finalist projects, ZBeam, proposed.

[gzumwalt] has not made the files available for download yet, but you can keep and eye on his Instructables pages for updates. He got a number of fascinating 3D printed devices already available, like a domino laying machine or a WiFi controlled rover.

34 thoughts on “3D Printed Rigid Chain Mechanism”

    1. It’s rare for me to come across an entirely new type of mechanical construct as a type of device, I really thought I’d seen everything till I saw this. I’ve never seen anything like this before. This gives me some rather interesting new ideas.

      Granted, I’ve seen a zipper before, but never seen a rigid chain by design like this.

      Both the OP and your link are really cool

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        2. That’s really neat thought it makes me wonder how they can keep the band engaged with the teeth.
          It kind of reminds be of playing with rolled paper as a kid where I would try to tighten the roll but if done unevenly (forming a spiral), the roll would start to telescope out one end.

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          1. I worked with these for a while. The simple answer is that the band would have to stretch a lot to disengage – there is no realistic way for the teeth to leave the holes. The original version did not have teeth at all – just a groove on the top and bottom of the flat spiral for the side wall to slot into. They developed the tooth version to allow use in a horizontal application.

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      2. That’s right, they have to be laterally constrained by linear guides to prevent buckling. The same company does make a commercial version of the OP video called RigiBelt but it’s intended for much lower loads than the one in this video.

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    4. I don’t like the serapid version.
      They’re half lying. That mechanism simply has a chain that only bends in one direction and you need multiple of those units to get stable in all directions, and they obfuscate that in their movies.

      The same mechanism is used in small window openers where it works quite well.

      I do like the spiralift version. You have to watch a few movies to understand how the wide band interacts with the toothed spiral to form a stable column. Very nice mechanism with a long reach in a compact build form.

      I quite like the build of this article itself. It’s basically two of the “serapid” mechanisms combined with a zipper. There is still quite some slop in it though. Using steel rods for the hinge points would probably greatly increase the load bearing capabilities and make it easier to print with smaller tolerances. But still, nice build for a demonstrator.

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  6. Back in the 80’s I read an article about a prototype device for building long girders in orbit from material packed into a small space. It had four rolls of metal strip. Three were folded lengthwise to a 120 degree angle as they were unrolled while the fourth was spiraled around and attached somehow (spot welds?) to the outside of the three corners to make a rigid triangular girder as long as the rolls of metal.

    It was tested on the ground but whomever made it couldn’t get NASA interested in a test flight on a Shuttle.

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    1. There is a nasa lander somewhere using someting like that based on the mechanism of a roll measuring tape, but I am unable to find that specific extenable arm. It is he agonal and it flattens wjen rolled up.

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    1. In this video from that company https://www.youtube.com/watch?v=W7taCIgpaAI&feature=emb_logo @2:10, they show the prototype functioning at our shop. I saw it in our attic a couple years ago, but I’m not sure if it’s still there.

      The company that got the SBIR award somehow had our company button up the project and get the prototype working. There’s a video somewhere of the old company owner riding the prototype too, but I can’t find it.

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