3D Printing A Harmonic Pin-Ring Gearing Drive

March 11, 2026 by Maya Posch 12 Comments

Cycloidal drives are a type of speed reducer that are significantly more compact than gearboxes, but they still come with a fair number of components. In comparison, the harmonic pin-ring drive that [Raph] recently came across as used in some TQ electric bicycles manages to significantly reduce the number of parts to just two discs. Naturally he had to 3D model his own version for printing a physical model to play with.

How exactly this pin-ring cycloidal drive works is explained well in the referenced [Pinkbike] article. Traditional cycloidal drives use load pins that help deal with the rather wobbly rotation from the eccentric input, but this makes for bulkier package that’s harder to shrink down. The change here is that the input force is transferred via two teethed discs that are 180° out of sync, thus not only cancelling out the wobble, but also being much more compact.

It appears to be a kind of strain wave gearing, which was first patented in 1957 by C.W. Musser and became famous under the Harmonic Drive name, seeing use by NASA in the Lunar Rover and beyond. Although not new technology by any means, having it get some more well-deserved attention is always worth it. If you want to play with the 3D model yourself, files are available both on GitHub and on MakerWorld.

The printer-based "pen" has a pistol form factor.

DIY 3D Pen Is Born To Weld

March 7, 2026 by Tyler August 10 Comments

Depending who you ask, 3D pens are silly toys or handy tools. Those who use them as tools find them handy to fill gaps in printed assemblies or to use them as a PLA or PETG-based hot glue gun for their prints. [half-baked-research] on YouTube is in the second category, but knows that welding is better than gluing — so he built himself a 3D pen designed for plastic welding.

You can weld with a regular 3D pen, and [half-baked] demonstrates that in the video. But thanks to the low-conductivity tips on commercial pens, it’s a slow, fiddly business. By using a normal 3D printer hot-end, with its conductive brass nozzle, [half-baked] is able to get a lot more heat where it’s needed. That means the plastic on either side of the weld melts for a good bond with the stuff coming out the nozzle. He’s also able to push plastic much faster with the modified extruder he’s squeezed into the hot-glue-gun looking contraption. Those two things together conspire to make the whole process go much faster than with a commercial 3D pen. He calls his build a 3D pen, but given the form factor it might be more accurate to call it a ‘plastic extrusion gun’.

Starting at around 13:38 in the video, he performs some strength tests, something we wish more YouTubers would do. He’s able to demonstrate a stronger bond with his welding pen than the normal 3D pen, and a much, much stronger join than the usual superglue. A traditional plastic weld with hot air is even stronger, but [half-baked] points out elsewhere in the video that on thin-walled prints (as opposed to the solid test articles) hot air welding can be a very dicey business. Pen-welding offers much greater control, so is an interesting technique to keep in mind.

Alas, [half-baked-research] apparently still considers this idea too half-baked to release the design. If you don’t have time to wait or reinvent this particular wheel, we featured a much simpler implementation of a similar idea years ago, using PLA in a hot glue gun. If that won’t work for you — maybe you aren’t a fan of PLA — perhaps you might try friction welding with filament.

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The Joys Of 3D Printing

February 28, 2026 by Elliot Williams 45 Comments

Al and I were talking on the podcast today about a sweet 3D printed wide-format camera build, and we got to musing on why we 3D-print.

For Al, it’s an opportunity to experiment with 3D printing itself: tweaking his machines to get the best performance out of them. Other people make small, functional objects that they need in their daily life, like bag clips or spare parts for broken appliances. Some folks go for the ornamental or the aesthetic. The kids in my son’s class all seem obsessed with sci-fi props and fidget toys. The initial RepRap ideal was to replace all commercial fabrication with machines owned by the individual, rather than by companies – it was going to be Marxist revolutionary.

But there’s another group of 3D printer enthusiasts that I think doesn’t get enough coverage, and I’m going to call them the hobbyist industrial designers. These are the people who design a custom dog-poop-bag holder that exactly fits their extra-wide dog leash, not because they couldn’t find one that fit in the pet store, but because it’s simply fun to design and fabricate things. (OK, that’s literally me.)

It’s fun to learn CAD tools, to learn about how things are designed, how they work, and how to manufacture them at least in quantity one. Dreaming, designing, fabricating, failing, and repeating until you get it right is a great joy. And then you get to use the poop-bag holder every day for a few years, until you decide to refine the design and incorporate the lessons learned on the tough streets of practical use.

Of course none of this is exclusive to 3D printing. There were always people who designed-and-built things in the metal machine shop, or made their creations out of wood. In that sense, the 3D printer is just another tool, and the real fun isn’t in using the 3D printer, but rather in the process of bringing things out of your mind and into the world. So maybe there is nothing new here, but the latitude that 3D printing affords the hobby designer is amazing, and that makes it all the more fun, and challenging.

So do you 3D print for necessity, to stick it to the man, to pimp your printer, for the mini-figs, or simply for the joy of the process of making things? It’s all good. 3D printing is a big tent.

Stop Ironing 3D Prints

February 25, 2026 by Al Williams 19 Comments

If you want smooth top surfaces on your 3D printed parts, a common technique is to turn on ironing in your slicer. This causes the head to drag through the top of the part, emitting a small amount of plastic to smooth the surface. [Make Wonderful Things] asserts that you don’t need to do this time-consuming step. Instead, he proposes using statistical analysis to identify the optimal settings to place the top layer correctly the first time, as shown in the video below.

The parameters he thinks make a difference are line width, flow ratio, and print speed. Picking reasonable step sizes suggested that there were 19,200 combinations of settings to test. Obviously, that’s too many, so he picked up techniques from famous mathematician [George E. P. Box] and also used Bayesian analysis to reduce the amount of printing required to converge on the perfect settings.

Did it work? Judging from the video, it appears to have done so. The best test pieces looked as good as the one that used traditional ironing. Compared to ironing, the non-ironed parts saved about 34% of print time. Not bad.

Of course, there are variations on traditional ironing, so your results may vary.

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Sub-Second Volumetric 3D Printing

February 25, 2026 by Ian Bos 20 Comments

One of the more promising 3D printing technologies that hasn’t quite yet had its spotlight is volumetric 3D printing. Researchers from the Department of Automation, Tsinghua University, have developed a new method that uses a high-speed periscope instead of rotating the printing volume — resulting in print times of less than one second.

Normal volumetric printing uses a rotating volume of photosensitive resin to print nearly any geometry desired. However, this method presents issues when printing at high speeds. If you rapidly rotate a liquid, it won’t exactly stay still. So why not rotate the projector itself? This change also allows the use of less viscous resins, which is particularly useful if you want to pump fluid around.

Why would you want to pump around liquid? Scalability of course! Printing in seconds while pumping the results into a collection vessel would allow for mass production more flexible than traditional ejection methods. The researchers manage to keep quality high with some fancy algorithmic correction, which allows for accuracy on the scale of μm.

While this technology still doesn’t find a common space among average hobbyists, this may soon change…especially with these mass manufacturing capabilities. For similar volumetric printing capabilities, check out xolography.

Thermoforming Printed Parts With Hot Water

February 19, 2026 by Maya Posch 14 Comments

Thermoforming is the process of softening a material enough so that it can be tweaked into a new shape, with the source of the thermal energy being not particularly relevant. Correspondingly, after [Zion Brock]’s recent video on his journey into thermoforming PLA with a mold and a heat gun, he got many comments suggesting that he should use hot water instead.

We covered his previous video as well, in which he goes through the design steps of making these grilles for a retro-styled, 3D printed radio. The thermoforming method enables him to shape the curvy grille with a heat gun and two-piece mold in a matter of minutes, rather than spending hours more time printing and removing many supports.

Theoretically using hot water instead of hot air would provide a more equal application of heat, but putting your hands into 70°C water does require some more precautions. There’s also the issue that PLA is very hygroscopic, so the part requires drying afterwards to prevent accelerated hydrolysis. Due to the more even heating, the edge of the PLA that clamped into the mold also softened significantly, causing it to pop out of the mold and requiring a small design modification to prevent this.

Basically, aqua-thermoforming like this has many advantages, as its slower and more consistent, but it’s less straightforward to use than hot air. This makes both a useful tool when you’re looking at doing thermoforming.

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3D Printed Jack Mixes Two Filaments For Great Performance

February 17, 2026 by Lewin Day 12 Comments

If you’re looking to jack up your car and you don’t have anything on hand, your 3D printer might not be the first tool you look towards. With that said, [Alan Reiner] had great success with a simple idea to create a surprisingly capable scissor jack with a multi-material print.

The design will look familiar if you’ve ever pulled the standard jack out of the back of your car. However, this one isn’t made fully out of steel. It relies on an M6 bolt and a rivet nut, but everything else is pure plastic. In this scissor jack design, rigid PETG arms are held in a scissor jack shape with a flexible TPU outer layer. Combined with the screw mechanism, it’s capable of delivering up to 400 pounds of force without failing. It’s an impressive figure for something made out of 80 grams of plastic. The idea came about because of [Alan’s] recent build of a RatRig VCore4 printer, which has independent dual extruders. This allowed the creation of single prints with both rigid and flexible filaments included.

[Alan] did test the jack by lifting up his vehicle, which it kind of achieved. The biggest problem was the short stroke length, which meant it could only raise the back of the car by a couple inches. Printing a larger version could make it a lot more practical for actual use… if you’re willing to trust a 3D-printed device in such use.

Files are on Printables if you wish to make your own. It’s worth paying attention to the warning upfront that [Alan] provides—”THIS CAN CREATE A LOT OF FORCE (400+ lbs!), WHICH MEANS IT CAN STORE A LOT OF ENERGY THAT MIGHT BE RELEASED SUDDENLY. Please be cautious using 3d-printed objects for high loads and wear appropriate safety equipment!”

Funnily enough, we’ve featured 3D printed jacks before, all the way back in 2015! Video after the break.

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