Mark Setrakian and Adam Savage investigate a massive prop hand

17 Year Old Hellboy II Prop Still Amazes

May 30, 2025 by Heidi Ulrich 7 Comments

The AI effects we know these days were once preceded by CGI, and those were once preceded by true hand-built physical props. If that makes you think of Muppets, this video will change your mind. In a behind-the-scenes look with [Adam Savage], effects designer [Mark Setrakian] reveals the full animatronic glory of Mr. Wink’s mechanical fist from Hellboy II: The Golden Army (2008) – and this beast still flexes.

Most of this arm was actually made in 2003, when 3D printing was very different than what we think of today. Printed on a Stratasys Titan – think: large refrigerator-sized machine, expensive as sin – the parts were then hand-textured with a Dremel for that war-scarred, brutalist feel. This wasn’t just basic animatronics for set dressing. This was a fully actuated prop with servo-driven finger joints, a retractable chain weapon, and bevel-geared mechanisms that scream mechanical craftsmanship.

Each finger is individually designed. The chain reel: powered by a DeWalt drill motor and custom bevel gear assembly. Every department: sculptors, CAD modelers, machinists, contributed to this hybrid of analog and digital magic. Props like this are becoming unicorns.

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3D Filament lizards show decomposable joints

Sustainable 3D Prints With Decomposable Filaments

May 30, 2025 by Heidi Ulrich 24 Comments

What if you could design your 3D print to fall apart on purpose? That’s the curious promise of a new paper from CHI 2025, which brings a serious hacker vibe to the sustainability problem of multi-material 3D printing. Titled Enabling Recycling of Multi-Material 3D Printed Objects through Computational Design and Disassembly by Dissolution, it proposes a technique that lets complex prints disassemble themselves via water-soluble seams. Just a bit of H₂O is needed, no drills or pliers.

At its core, this method builds dissolvable interfaces between materials like PLA and TPU using water-soluble PVA. Their algorithm auto-generates jointed seams (think shrink-wrap meets mushroom pegs) that don’t interfere with the part’s function. Once printed, the object behaves like any ordinary 3D creation. But at end-of-life, a water bath breaks it down into clean, separable materials, ready for recycling. That gives 90% material recovery, and over 50% reduction in carbon emissions.

This is the research – call it a very, very well documented hack – we need more of. It’s climate-conscious and machine-savvy. If you’re into computational fabrication or environmental tinkering, it’s worth your time. Hats off to [Wen, Bae, and Rivera] for turning what might otherwise be considered a failure into a feature.

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You Can 3D Print These Assistive Typing Tools

May 22, 2025 by Lewin Day 8 Comments

Typing can be difficult to learn at the best of times. Until you get the muscle memory down, it can be quite challenging. However, if you’ve had one or more fingers amputated, it can be even more difficult. Just reaching the keys properly can be a challenge. To help in this regard, [Roei Weiman] built some assistive typing tools for those looking for a little aid at the keyboard.

The devices were built for [Yoni], who works in tech and has two amputated fingers. [Roei] worked on many revisions to create a viable brace and extension device that would help [Yoni] type with greater accuracy and speed.

While [Roei] designed the parts for SLS 3D printing, it’s not mandatory—these can easily be produced on an FDM printer, too. For SLS users, nylon is recommended, while FDM printers will probably find best results with PETG. It may also be desirable to perform a silicone casting to add a grippier surface to some of the parts, a process we’ve explored previously.

The great thing about 3D printing is that it enables just about anyone to have a go at producing their own simple assistive aids like these. Files are on Instructables for the curious. Video after the break.

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Wire-frame image of gearbox, setup as a differential

Roller Gearbox Allows For New Angles In Robotics

May 22, 2025 by Ian Bos 17 Comments

DIY mechatronics always has some unique challenges when relying on simple tools. 3D printing enables some great abilities but high precision gearboxes are still a difficult problem for many. Answering this problem, [Sergei Mishin] has developed a very interesting gearbox solution based on a research paper looking into simple rollers instead of traditional gears. The unique attributes of the design come from the ability to have a compact angled gearbox similar to a bevel gearbox.

Multiple rollers rest on a simple shaft allowing each roller to have independent rotation. This is important because having a circular crown gear for angled transmission creates different rotation speeds. In [Sergei]’s testing, he found that his example gearbox could withstand 9 Nm with the actual adapter breaking before the gearbox showing decent strength.

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Picture of self landing drone satellite with orange and black body. Propellors are extended.

FPV Drone Takes Off From A Rocketing Start

May 15, 2025 by Ian Bos 24 Comments

Launching rockets into the sky can be a thrill, but why not make the fall just as interesting? That is exactly what [I Build Stuff] thought when attempting to build a self-landing payload. The idea is to release a can sized “satellite” from a rocket at an altitude upwards of 1 km, which will then fly back down to the launch point.

The device itself is a first-person view (FPV) drone running the popular Betaflight firmware. With arms that swing out with some of the smallest brushless motors you’ve ever seen (albeit not the smallest motor), the satellite is surprisingly capable. Unfortunately due to concerns over the legality of an autonomous payload, the drone is human controlled on the descent.

Using collaborated efforts, a successful launch was flown with the satellite making it to the ground unharmed, at least for the most part. While the device did show capabilities of being able to fly back, human error led to a manual recovery. Of course, this is far from the only rocketry hack we have seen here at Hackaday. If you are more into making the flight itself interesting, here is a record breaking one from USC students.

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Best Practices For FDM Printing

May 10, 2025 by Al Williams 37 Comments

If you’ve been designing parts for 3D printing, you probably have some tricks and standards for your designs. [Rahix] decided to write out a well-thought-out set of design rules for FDM prints, and we can all benefit.

One of the things we liked about the list is that it’s written in a way that explains everything. Every so often, there’s a box with a summarized rule for that topic. At the end, there’s a list of all the rules. The rules are also in categories, including part strength, tolerance, optimization, integration, machine elements, appearance, and vase mode.

For example, section two deals with tolerance and finish. So, rule R2.8 says, “Do not use circular holes for interference fits. Use hexagon or square holes instead.”

We also appreciate that [Rahix] touched on some of the counter-intuitive aspects of designing for FDM printing. For example, you might think adding voids in your part will reduce the filament and time required to print it, but in many cases it can have the opposite effect.

Some of these — maybe even most of these — won’t surprise you, but you still might take away a tidbit or two. But having it all down in a checklist and then the ability to scroll up and find the rationale for the rule is great.

Do you have any rules you’d add? Or change? Let us know. Meanwhile, we were eyeing our favorites about adding machine elements to prints.

Scan Your Caliper For Physical Part Copies

May 9, 2025 by Al Williams 60 Comments

We’ve certainly seen people take a photo of a part, bring it into CAD, and then scale it until some dimension on the screen is the same as a known dimension of the part. We like what [Scale Addition] shows in the video below. In addition to a picture of the part, he also takes a picture of a vernier caliper gripping the part. Now your scale is built into the picture, and you can edit out the caliper later.

He uses SketchUp, but this would work on any software that can import an image. Given the image with the correct scale, it is usually trivial to sketch over the image or even use an automatic tracing function. You still need some measurements, of course. The part in question has a vertical portion that doesn’t show up in a flat photograph. We’ve had good luck using a flatbed scanner before, and there’s no reason you couldn’t scan a part with a caliper for scale.

This is one case where a digital caliper probably isn’t as handy as an old-school one. But it would be possible to do the same trick with any measurement device. You could even take your picture on a grid of known dimensions. This would also allow you to check that the distances at the top and bottom are the same as the distances on the right and left.

Of course, you can get 3D scanners, but they have their own challenges.

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