Ask Hackaday: Are You Wearing 3D Printed Shoes?

July 10, 2025 by 35 Comments

We love 3D printing. We’ll print brackets, brackets for brackets, and brackets to hold other brackets in place. Perhaps even a guilty-pleasure Benchy. But 3D printed shoes? That’s where we start to have questions.

Every few months, someone announces a new line of 3D-printed footwear. Do you really want your next pair of sneakers to come out of a nozzle? Most of the shoes are either limited editions or fail to become very popular.

First World Problem

You might be thinking, “Really? Is this a problem that 3D printing is uniquely situated to solve?” You might assume that this is just some funny designs on some of the 3D model download sites. But no. Adidas, Nike, and Puma have shoes that are at least partially 3D printed. We have to ask why.

We are pretty happy with our shoes just the way that they are. But we will admit, if you insist on getting a perfect fitting shoe, maybe having a scan of your foot and a custom or semi-custom shoe printed is a good idea. Zellerfield lets you scan your feet with your phone, for example. [Stefan] at CNC Kitchen had a look at those in a recent video. The company is also in many partnerships, so when you hear that Hugo Boss, Mallet London, and Sean Watherspoon have a 3D-printed shoe, it might actually be their design from Zellerfield.

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Screenshot of "Frame of Preference"

An Emulated Stroll Down Macintosh Memory Lane

July 10, 2025 by 6 Comments

If you’re into Macs, you’ll always remember your first. Maybe it was the revolutionary classic of 1984 fame, perhaps it was the adorable G3 iMac in 1998, or even a shiny OS X machine in the 21st century. Whichever it is, you’ll find it emulated in [Marcin Wichary]’s essay “Frame of preference: A history of Mac settings, 1984–2004” — an exploration of the control panel and its history.

Image of PowerBook showing the MacOS 8.0 desktop.
That’s not a photograph, it’s an emulator. (At least on the page. Here, it’s a screenshot.)

[Marcin] is a UI designer as well as an engineer and tech historian, and his UI chops come out in full force, commenting and critiquing Curputino’s coercions. The writing is excellent, as you’d expect from the man who wrote the book on keyboards, and it provides a fascinating look at the world of retrocomputing through the eyes of a designer. That design-focused outlook is very apropos for Apple in particular. (And NeXT, of course, because you can’t tell the story of Apple without it.)

There are ten emulators on the page, provided by [Mihai Parparita] of Infinite Mac. It’s like a virtual museum with a particularly knowledgeable tour guide — and it’s a blast, getting to feel hands-on, the design changes being discussed. There’s a certain amount of gamification, with each system having suggested tasks and a completion score when you finish reading. There are even Easter eggs.

This is everything we wish the modern web was like: the passionate deep-dives of personal sites on the Old Web, but enhanced and enabled by modern technology. If you’re missing those vintage Mac days and don’t want to explore them in browser, you can 3D print your own full-size replica, or a doll-sized picoMac.

 

Generatively-Designed Aerospike Test Fired

July 10, 2025 by 20 Comments

The aerospike engine holds great promise for spaceflight, but for various reasons, has remained slightly out of reach for decades. But thanks to Leap 71, the technology has moved one step closer to a spacecraft near you with the test fire of their generatively-designed, 3D printed aerospike.

We reported on the original design process of the engine, but at the time it hadn’t been given a chance to burn its liquid oxygen and kerosene fuel. The special sauce was the application of a computational physics model to tackle the complex issue of keeping the engine components cool enough to function while directing 3,500˚C exhaust around the eponymous spike.

Printed via a powder bed process out of CuCrZr, cleaned, heat treated, and then prepped by the University of Sheffield’s Race 2 Space Team, the rocket produced 5,000 Newtons (1,100 lbf) of thrust during its test fire. For comparison, VentureStar, the ill-fated aerospike single stage to orbit project from the 1990s, was projected to produce more than 1,917 kilonewtons (431,000 lbf) from each of its seven RS-2200 engines. Leap 71 obviously has some scaling up to do before this can propel any crewed spacecraft.

If you want to build your own aerospike or 3D printed rocket nozzles we encourage you to read, understand, and follow all relevant safety guidelines when handling your rockets. It is rocket science, after all!

fume extractor

Solder Smarts: Hands-Free Fume Extractor Hack

July 9, 2025 by 7 Comments

[Ryan] purchased a large fume extractor designed to sit on the floor below the work area and pull solder fumes down into its filtering elements. The only drawback to this new filter was that its controls were located near his feet. Rather than kicking at his new equipment, he devised a way to automate it.

By adding a Wemos D1 Mini microcontroller running ESPHome, a relay board, and a small AC-to-DC transformer, [Ryan] can now control the single push button used to cycle through speed settings wirelessly. Including the small transformer inside was a clever touch, as it allows the unit to require only a single power cable while keeping all the newfound smarts hidden inside.

The relay controls the button in parallel, so the physical button still works. Now that the extractor is integrated with Home Assistant, he can automate it. The fan can be controlled via his phone, but even better, he automated it to turn on by monitoring the power draw on the smart outlet his soldering iron is plugged into. When he turns on his iron, the fume extractor automatically kicks in.

Check out some other great automations we’ve featured that take over mundane tasks.

Volume Controller Rejects Skeumorphism, Embraces The Physical

July 9, 2025 by 33 Comments

The volume slider on our virtual desktops is a skeuomorphic callback to the volume sliders on professional audio equipment on actual, physical desktops. [Maker Vibe] decided that this skeuomorphism was so last century, and made himself a physical audio control box for his PC.

Since he has three audio outputs he needs to consider, the peripheral he creates could conceivably be called a fader. It certainly has that look, anyway: each output is controlled by a volume slider — connected to a linear potentiometer — and a mute button. Seeing a linear potentiometer used for volume control threw us for a second, until we remembered this was for the computer’s volume control, not an actual volume control circuit. The computer’s volume slider already does the logarithmic conversion. A Seeed Studio Xiao ESP32S3 lives at the heart of this thing, emulating a Bluetooth gamepad using a library by LemmingDev. A trio of LEDs round out the electronics to provide an indicator for which audio channels are muted or active.

Those Bluetooth signals are interpreted by a Python script feeding a software called Voicmeeter Banana, because [Maker Vibe] uses Windows, and Redmond’s finest operating system doesn’t expose audio controls in an easily-accessible way. Voicmeeter Banana (and its attendant Python script) takes care of telling Windows what to do. 

The whole setup lives on [Maker Vibe]’s desk in a handsome 3D printed box. He used a Circuit vinyl cutter to cut out masks so he could airbrush different colours onto the print after sanding down the layer lines. That’s another one for the archive of how to make front panels.

If volume sliders aren’t doing it for you, perhaps you’d prefer to control your audio with a conductor’s baton. 

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How To Train A New Voice For Piper With Only A Single Phrase

July 9, 2025 by 6 Comments

[Cal Bryant] hacked together a home automation system years ago, which more recently utilizes Piper TTS (text-to-speech) voices for various undisclosed purposes. Not satisfied with the robotic-sounding standard voices available, [Cal] set about an experiment to fine-tune the Piper TTS AI voice model using a clone of a single phrase created by a commercial TTS voice as a starting point.

Before the release of Piper TTS in 2023, existing free-to-use TTS systems such as espeak and Festival sounded robotic and flat. Piper delivered much more natural-sounding output, without requiring massive resources to run. To change the voice style, the Piper AI model can be either retrained from scratch or fine-tuned with less effort. In the latter case, the problem to be solved first was how to generate the necessary volume of training phrases to run the fine-tuning of Piper’s AI model. This was solved using a heavyweight AI model, ChatterBox, which is capable of so-called zero-shot training. Check out the Chatterbox demo here.

As the loss function gets smaller, the model’s accuracy gets better

Training began with a corpus of test phrases in text format to ensure decent coverage of everyday English. [Cal] used ChatterBox to clone audio from a single test phrase generated by a ‘mystery TTS system’ and created 1,300 test phrases from this new voice. This audio set served as training data to fine-tune the Piper AI model on the lashed-up GPU rig.

To verify accuracy, [Cal] used OpenAI’s Whisper software to transcribe the audio back to text, in order to compare with the original text corpus. To overcome issues with punctuation and differences between US and UK English, the text was converted into phonemes using espeak-ng, resulting in a 98% phrase matching accuracy.

After down-sampling the training set using SoX, it was ready for the Piper TTS training system. Despite all the preparation, running the software felt anticlimactic. A few inconsistencies in the dataset necessitated the removal of some data points. After five days of training parked outside in the shade due to concerns about heat, TensorBoard indicated that the model’s loss function was converging. That’s AI-speak for: the model was tuned and ready for action! We think it sounds pretty slick.

If all this new-fangled AI speech synthesis is too complex and, well, a bit creepy for you, may we offer a more 1980s solution to making stuff talk? Finally, most people take the ability to speak for granted, until they can no longer do so. Here’s a team using cutting-edge AI to give people back that ability.

No Tension For Tensors?

July 9, 2025 by 11 Comments

We always enjoy [FloatHeadPhysics] explaining any math or physics topic. We don’t know if he’s acting or not, but he seems genuinely excited about every topic he covers, and it is infectious. He also has entertaining imaginary conversations with people like Feynman and Einstein. His recent video on tensors begins by showing the vector form of Ohm’s law, making it even more interesting. Check out the video below.

If you ever thought you could use fewer numbers for many tensor calculations, [FloatHeadPhysics] had the same idea. Luckily, imaginary Feynman explains why this isn’t right, and the answer shows the basic nature of why people use tensors.

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