Quadrupeds. I’ve been dreaming about quadrupeds. I’ve been hunting for challenges to test my methods and improve the engineering on the whole “print and cast a soft robot” thing (I really need to come up with a name for this… “Borgatronics?”). I started with tentacles because they were easy to design, easy to test, and symmetrical.
I am now the happy owner of a fully functional robotic tentacle. I’m pleased. After a few iterations, some hair pulling, and some welcome help from programmer, hacker, and generally pleasant person: TQ, the Trefoil Tentacle is now waving around in disconcerting glory. You can find a whole set of high res images of it here.
Last week I headed up to Viridis3d for some more hacking. We got some beautiful results using some vaccuum casting with the trefoil design, parts printed for both the internals and outer shell of the quadruped, and schemes for tempting new mechanisms. All in all it’s been really exciting seeing the progress. Also, I have some updates on controlling the trefoil tentacle with an arduino powered set of air solenoids.
I’ve finally gathered my wits after a whirlwind tour of Europe, starting at CCC, giving some talks and connecting up with potential collaborators, to Berlin to meet hackers I hadn’t seen in years, to Brussels to play with some material science experiments in impact resisting plastics. While at CCC I gave three talks, two lightning talks on digital fabrication and the strange world of news advertisement, and a 15 minute talk on the methodology and philosophy behind my soft robots.
I have lots of updates to share. First, there’s a new video of the latest tentacle prototype in action below the fold. Second, We’ve made some excellent progress on the method of manufacture, reliability, and repeatability of the designs we’re producing. It’s almost at the point where we need to figure out a good real-world experiment to test our ideas against. I’m currently torn between creating a grasper and something that walks. Jim and I have been working out ways of getting a self contained power source inside of a soft robot, and it seems like we might be able to use a canister of compressed gas to do everything from timing movements to articulating valves. I’m working out ways of integrating peristaltic pumps and timing mechanisms that will be simple to prototype… which is a pretty tall order. However, I think a combo of laser cut bits and creative molding can have this one solved.
After only six actual work days, a few afternoons spent on CAD, and a lot of tweaking, I’ve got a working robotic tentacle prototype! I used the hand pump off of a sphygmomanometer and a lot of sil-poxy, but it’s working in a rough and ready way. There’s video after the jump below.
I had to cut this one open to fully remove all the core and then sealed it back up. I think the next version will evacuate the core cleanly due to the powder tweaks we made, though. It could also use some revisions to the way it interfaces with the air supply. In the future I’m going to have to run some tests on adhering silicone to various plastics to see what will make for the most solid fittings. The sil-poxy infosheet says polyurethanes are a good candidate, so I might start there.
I just arrived back from a second session of hacking and casting with Jim Bredt over at Viridis3D, and I have to say I’m pretty excited. The biggest result of the most recent round of mold making is a successful method for getting soluble cores into printed molds and casting silicone around them reliably and repeatably. I ended up doing a lot of revisions to the casting method and industrial design based on the results of last month’s experiments. The mold goes together in new ways with changes to accommodate pouring the mold, reusing the outer shell, aligning the cores, printing the cores, and how it will get hooked up to pneumatics once everything’s cast and functioning. I’m especially proud of the design behind the base of the soluble core, which is tapered so that it can align and center itself within the mold even if its dimensions shrink by a few percent. The little ears on this base are both to align it rotationally (which doesn’t matter much as far as the tentacle is concerned, but could matter in other more complex molds) and to prevent the core dropping down further into the mold and mucking up the wall thickness if it shrinks more than spec.
I’ve had an outrageous streak of luck, lately. Firstly, I got a lovely plug from BoingBong (via the additionally lovely Xeni Jardin) that introduced a whole slew of new people to my store. Secondly, an event I’ve been hosting over at my shop, Craft Night, has been drawing an incredible crowd of excellent makers. It’s starting to feel like I’ve got a genuine tribe here in the city. Thirdly, I’ve finally been able to experiment with a technology I’ve been talking about and sketching for years: soft robots.
My friend, the extraordinary jeweler, maker, and programmer Aaron Waychoff, introduced me to Jim Bredt. Jim is many things. He moonlights as the human spotlight at the Ignobel Awards. He’s a metal smithing, mold making, 3d printing, material scientist, MIT professor. He also won an award for being a major ball buster when he taught “Introduction to Solid State Chemistry”.