Ball and socket joints are useful, but making a part slide over the surface of a sphere, held by magnets, requires a lot of fiddling to get right. We admire persistence and nailing all the details. [Matthew Finlay] has been doing just that with his ball and socket robot. He’s on version six, a testament to his desire to do the idea justice. Luckily for us, he’s documented each version as he went.
Version one, made from a DIY Christmas ornament ball, had no stability around the radial axis, and oscillated badly. Version two demonstrated the problem of centering the mechanism in the ball. Version 3 fixed this problem (it’s covered in the same video). Then version four fixed many of the assembly issues and replaced the servo controllers with an Arduino, but the ‘arm’ piece was too small and mechanically iffy.
Version five used a fabricated bearing. Matthew used airsoft rounds as the balls. Not a good idea. And assembly was a nightmare. So all this progress up to version six shows his improving technique. Artists say ‘work on your process, not on your pieces’. He’s become much more analytic about what’s needed. He’s started measuring the strength of the robot, and handled issues like adding limit switches so it doesn’t crash at the limits of travel.
The wonders of 3D printing don’t stop coming. Whether it’s printing tools on the International Space Station, printing houses out of concrete, or just making spare parts for a child’s toy, there’s virtually nothing you can’t get done with the right 3D printer, including spicing up your Halloween decorations.
Not only is this pumpkin a great-looking decoration for the season on its own, but it can also transform into a rather unsettling spider as well for a little bit of traditional Halloween surprise. The print is seven parts, which all snap into place and fold together with a set of ball-and-socket joints. While it doesn’t have any automatic opening and closing from a set of servos, perhaps we will see someone come up with a motion-activated pumpkin spider transformer that will shock all the trick-or-treaters at the end of this month.
It’s not too late to get one for yourself, either. The files are available on Thingiverse or through the project site. And we’ve seen plenty of other Halloween hacks and projects throughout the years too if you’re looking for other ideas, like the recent candy machine game, a rather surprising flying human head, or this terrifying robot.
One reason is to take advantage of standardized, open source creativity. Anyone can share a model of their design for all to use as is, or to modify for their needs. A case in point is the ball and socket model which I downloaded for a helping hand. I then drew up and printed a magnifying glass holder with a matching socket, made a variation of the ball and socket joint, and came up with a magnetic holder with matching ball. Let’s takea look at what worked well and what didn’t.
Is this a case of a good design gone wrong in the build phase? Or is this DIY prosthetic arm a poor design from the get-go? Either way, [Will Donaldson] needs some feedback, and Hackaday is just the right place for that.
Up front, we’ll say kudos to [Will] for having the guts to post a build that’s less than successful. And we’ll stipulate that when it comes to fully articulated prosthetic hands, it’s easy to fail. His design is ambitious, with an opposable thumb, fingers with three phalanges each, a ball and socket wrist, and internal servos driving everything. It’s also aesthetically pleasing, with a little bit of an I, Robot meets Stormtrooper look.
But [Will]’s build was plagued with print problems from the start, possibly due to the complex nature of the bosses and guides within the palm for all the finger servos. Bad prints led to creaky joints and broken servos. The servos themselves were a source of consternation, modified as they were for continuous rotation and broken apart for remotely mounting their pots in the hand’s knuckles. The video below relates the tale of woe.