Does 3D-Printed Foam Make Good Custom Tires?

November 2, 2025 by Donald Papp 10 Comments

Wouldn’t it be nice to 3D print an entire custom tire for small robots? It sure would, so [Angus] of [Maker’s Muse] decided to investigate whether nifty new filaments like expanding TPU offer anything new in this area. He did more than just print out a variety of smooth tires; he tested each with a motorized platform attached to a load cell, driving on a dusty sheet of MDF to simulate the average shop floor, or ant weight combat robot arena.

Why bother making your own wheels? As [Angus] points out, when one is designing their own robots from scratch, it’s actually quite difficult to find something off the shelf that is just the right size. And even if one does find a wheel that is just right, there’s still the matter of fitting it to the shaft. Things would be so much easier if one could simply 3D print both wheel and tire in a material that performs well.

Here’s what he found: Siraya Tech’s TPU air filament (about 70A on the Shore hardness scale) performed the best. This is TPU plus a heat-activated additive that foams up during extrusion, resulting in a flexible print that looks and feels more like foam than usual TPU. It makes a promising tire that performs as well as it looks. Another expanding filament, PEBA air (also from Siraya Tech) didn’t look or perform as well, but was roughly in the same ballpark.

Both performed better than the classic DIY options of 3D-printed plain TPU, or laser-cut EVA foam. It’s certainly a lot less work than casting custom tires.

What about adding a tread pattern? [Angus] gave it a try. Perhaps unsurprisingly, a knobby tire has worse traction compared to a smooth tire on smooth MDF. But sometimes treads are appropriate, and as [Angus] points out, if one is 3D printing tires then adding treads comes at essentially zero cost. That’s a powerful ability.

Even if you are not interested in custom wheels, that foaming TPU filament looks pretty nifty. See for yourself in the video, embedded just below. If you find yourself finding a good use for it, be sure to drop us a tip!

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Automatically Serving Up Canned Cat Food

October 23, 2025 by Bryan Cockfield 18 Comments

If there’s any one benefit to having a cat as a pet instead of a dog, it’s that they’re a bit more independent and able to care for themselves for many days without human intervention. The only thing that’s really needed is a way to make sure they get food and water at regular intervals, but there are plenty of off-the-shelf options for these tasks. Assuming your cat can be fed dry food, that is. [Ben Heck]’s cat has a health problem that requires a special canned wet food, and since there aren’t automatic feeders for this he built his own cat-feeding robot.

Unlike dry food that can dispense a measured amount from a hopper full of food, the wet food needs to be opened and dispensed every day. To accomplish this, his robot has a mechanism that slowly slides a wedge under the pull tab on the can, punctures the can with it, and then pulls it back to remove the lid. From there the food is ejected from the feeder down a ramp to a waiting (and sometimes startled) cat. The cans are loaded into 3D-printed cartridges and then stacked into the machine on top of each other, so the machine can dispense food cans until it runs out. This design has space for six cans.

Although there are many benefits to having pets of any sort, one of the fun side quests of pet ownership is building fun things for them to enjoy or to make caring for them easier. We even had an entire Hackaday contest based on this premise. And, if biological life forms aren’t your cup of tea, there are always virtual pets to care for as well.

Thanks to [Michael C] for the tip!

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Robot Bartender Is The Life Of The Party

September 26, 2025 by Bryan Cockfield 9 Comments

As the old saying goes, when the only tool you have is a 6 DOF industrial robotic arm, every problem looks like an opportunity to make it serve up adult beverages. [benkokes] found himself in this familiar predicament and did what any of us would do, but his process wasn’t without a few party fouls as well as a few head-scratchers.

One of the common problems that people who suddenly find themselves with an old industrial robot have is that there’s usually no documentation or instructions. This was true here with the added hiccup of the robot’s UI being set to Chinese. Luckily no one had changed the root password, and eventually he was able to get the robot up and working.

Getting it to make drinks was a different matter altogether. [benkokes] needed a custom tool to hold the cup as well as shake it, and 3D printed a claw-style end effector with a lid. Out of his multi-colored pack of party cups, however, the orange cups were different enough in dimension to cause problems for the shaking lid which was discovered when the robot spilled a drink all over the table.

Eventually, though, the robot was successfully serving drinks at a party. One of [benkokes]’s friends happened to be a puppet maker and was able to outfit it with a tailored tuxedo for the party as well, and he also programmed it to dance in between serving drinks, completing the AI revolution we have all been hoping for. Perhaps unsurprisingly, this is a common project for people who suddenly come to posses a large general-purpose industrial robot, while others build robots specifically for this task alone.

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A Closer Look Inside A Robot’s Typewriter-Inspired Mouth

September 15, 2025 by Donald Papp 26 Comments

[Ancient] has a video showing off a fascinating piece of work: a lip-syncing robot whose animated electro-mechanical mouth works like an IBM Selectric typewriter. The mouth rapidly flips between different phonetic positions, creating the appearance of moving lips and mouth. This rapid and high-precision movement is the product of a carefully-planned and executed build. When we featured this project before, we wanted to see under the hood. Now we can.

Behind the face is a ball that, when moving quickly enough, gives the impression of animated mouth and lips. The new video gives a closer look at how it works.

[Ancient] dubs the concept Selectramatronics, because its action is reminiscent of the IBM Selectric typewriter. Instead of each key having a letter on a long arm that would swing up and stamp an ink ribbon, the Selectric used a roughly spherical unit – called a typeball – with letters sticking out of it like a spiky ball.

Hitting the ‘A’ key would rapidly turn the typeball so that the ‘A’ faced forward, then satisfyingly smack it into the ink ribbon at great speed. Here’s a look at how that system worked, by way of designing DIY typeballs from scratch. In this robot, the same concept is used to rapidly flip a ball bristling with lip positions.

We first saw this unusual and fascinating design when its creator showed videos of the end result on social media, pronouncing it complete. We’re delighted to see that there’s now an in-depth look at the internals in the form of a new video (the first link in this post, also embedded below just under the page break.)

The new video is wonderfully wordless, preferring to show rather than tell. It goes all the way from introducing the basic concept to showing off the final product, lip-syncing to audio from an embedded Raspberry Pi.

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Build Your Own Pip-Boy Styled Watch

September 2, 2025 by Donald Papp 6 Comments

[Arnov Sharma]’s latest PIP-WATCH version is an homage to Pip-Boys, the multi-function wrist-mounted personal computers of Fallout.

We like the magnetic clasp on the back end.

[Arnov] has created a really clean wearable design with great build instructions, so anyone who wants to make their own should have an easy time. Prefer to put your own spin on it, or feel inspired by the wrist-mounted enclosure? He’s thoughtfully provided the CAD files as well.

Inside the PIP-WATCH is a neat piece of hardware, the Lilygo T-Display-S3 Long. It’s an ESP32-based board with a wide, touch-enabled, color 180 x 640 display attached. That makes it a perfect fit for a project like this, at least in theory. In practice, [Arnov] found the documentation extremely lacking which made the hardware difficult to use, but he provides code and instructions so there’s no need to go through the same hassles he did.

In addition to the Hackaday.io project page, there’s an Instructables walkthrough.

If you put your own spin on a Pip-boy (whether just a project inspired by one, or a no-detail-spared build of dizzying detail) we want to hear about it, so be sure to drop us a tip!

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Watch Bondo Putty Get Sprayed Onto 3D Prints

August 31, 2025 by Donald Papp 18 Comments

3D prints destined for presentation need smooth surfaces, and that usually means sanding. [Uncle Jessy] came across an idea he decided to try out for himself: spraying Bondo spot putty onto a 3D print. Bondo spot putty comes from a tube, cures quickly, and sands smoothly. It’s commonly used to hide defects and give 3D prints a great finish. Could spraying liquified Bondo putty onto a 3D print save time, or act as a cheat code for hiding layer lines? [Uncle Jessy] decided to find out.

Gaps and larger flaws still need to be filled by hand, but spray application seems to be a big time saver if nothing else.

The first step is to turn the distinctive red putty into something that can be sprayed through a cheap, ten dollar airbrush. That part was as easy as squeezing putty into a cup and mixing in acetone in that-looks-about-right proportions. A little test spray showed everything working as expected, so [Uncle Jessy] used an iron man mask (smooth surfaces on the outside, textured inside) for a trial run.

Spraying the liquified Bondo putty looks about as easy as spraying paint. The distinctive red makes it easy to see coverage, and it cures very rapidly. It’s super easy to quickly give an object an even coating — even in textured and uneven spots — which is an advantage all on its own. To get a truly smooth surface one still needs to do some sanding, but the application itself looks super easy.

Is it worth doing? [Uncle Jessy] says it depends. First of all, aerosolizing Bondo requires attention to be paid to safety. There’s also a fair bit of setup involved (and a bit of mess) so it might not be worth the hassle for small pieces, but for larger objects it seems like a huge time saver. It certainly seems to cover layer lines nicely, but one is still left with a Bondo-coated object in the end that might require additional sanding, so it’s not necessarily a cheat code for a finished product.

If you think the procedure might be useful, check out the video (embedded below) for a walkthrough. Just remember to do it in a well-ventilated area and wear appropriate PPE.

An alternative to applying Bondo is brush application of UV resin, but we’ve also seen interesting results from non-planar ironing.

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Animatronic Eyes Are Watching You

August 28, 2025 by Tyler August 9 Comments

If you haven’t been following [Will Cogley]’s animatronic adventures on YouTube, you’re missing out. He’s got a good thing going, and the latest step is an adorable robot that tracks you with its own eyes.

Yes, the cameras are embedded inside the animatronic eyes.That was a lot easier than expected; rather than the redesign he was afraid of [Will] was able to route the camera cable through his existing animatronic mechanism, and only needed to hollow out the eyeball. The tiny camera’s aperture sits nigh-undetectable within the pupil.

On the software side, face tracking is provided by MediaPipe. It’s currently running on a laptop, but the plan is to embed a Raspberry Pi inside the robot at a later date. MediaPipe tracks any visible face and calculates the X and Y offset to direct the servos. With a dead zone at the center of the image and a little smoothing, the eye motion becomes uncannily natural. [Will] doesn’t say how he’s got it set up to handle more than one face; likely it will just stick with the first object identified.

Eyes aren’t much by themselves, so [Will] goes further by creating a little robot. The adorable head sits on a 3D-printed tapered roller bearing atop a very simple body. Another printed mechanism allows for pivot, and both axes are servo-controlled, bringing the total number of motors up to six. Tracking prefers eye motion, and the head pivots to follow to try and create a naturalistic motion. Judge for yourself how well it works in the video below. (Jump to 7:15 for the finished product.)

We’ve featured [Will]’s animatronic anatomy adventures before– everything from beating hearts, and full-motion bionic hands, to an earlier, camera-less iteration of the eyes in this project.

Don’t forget if you ever find yourself wading into the Uncanny Valley that you can tip us off to make sure everyone can share in the discomfort.

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