Continously Extruding 3D Printed Tubes With Compressed Air

August 9, 2026 by 2 Comments

[Jan] of [Roetz 4.0] has a unique approach to multi-material 3D printing: he’s designed an extruder which takes two different materials and extrudes one as a shell around the other. This opens up some interesting possibilities, such as a conductive filament surrounded by an insulating shell; [Jan], however, didn’t have an immediate use for the process, so he moved on to a related technique: extruding plastic tubes with a compressed-air core.

The extruder he used for this was a variation on the dual-material extruder; it takes in two strands of filament, melts them, and extrudes them as a shell around the outlet of a compressed-air line, which was controlled by a high-precision pressure regulator. During testing with PLA, it seemed capable of extruding airtight tubes of filament, though it had a tendency to blow bubbles and form tubes with inconsistent diameters. The low thermal conductivity of the stainless steel extruder also proved problematic; coupled with the cooling effect of the compressed air, filament sometimes solidified inside the extruder.

[Jan] found it almost impossible to get consistent results using only pressure-based control; as the layer of molten plastic around the air gets thinner, it provides less resistance to further ballooning, leading to continuous expansion until the bubble bursts. Controlling the volume of air extruded provided much more consistent results, and in a second video, he built a peristaltic pump to do just that. He also switched to using TPU filament, which greatly improved layer adhesion. When inflated with compressed air, the finished TPU structures expanded slightly, though there were still air leaks. The results look promising, and TU Darmstadt has already carried out some research in this area.

In a separate research project, we’ve seen a similar multi-material co-extrusion approach used to print pneumatic channels. For more on the history of [Jan]’s multi-filament extruder, check out his Minuteman printer. Continue reading “Continously Extruding 3D Printed Tubes With Compressed Air” →

Whatever Happened To The Computer Of Tomorrow, Anyway? The Xerox Alto Story

August 9, 2026 by 10 Comments

You’ve almost certainly heard of the Xerox Alto, the machine that pioneered the desktop-mouse-keyboard interface and inspired Steve Jobs to produce the Apple Lisa and Macintosh computers. It wasn’t just having a desktop, though– so much of our modern computing paradigm was invented on these machines. Given that, why aren’t we all using Xerox clones instead of Apples or PCs descended from the IBM compatibles? [Ctrl+Alt+Fail] has a video that answers the question: whatever happened to the computer of tomorrow, anyway?

It goes through the whole story of the Alto, from its introduction at Xerox PARC in the 1970s to its demise. At the introduction, the engineers showed of the What You See Is What You Get word processor, networked the machines together to show off e-mail and that anyone could use the office laser printer. It all seems very familiar now, but at the time, it was a revolution. An expensive one. The monitor sitting on the desk wasn’t the computer, after all: that was a large filing-cabinet sized desk sitting underneath. Only about 2000 were ever built, so what happened?

It wasn’t just that the first units cost twelve grand USD to build in 1973 money– about 90 large today by CPI, or for the gold bugs that’s 96 oz or 2.7 kg. It wasn’t worth its weight in gold, but it was close. Still, that wasn’t the problem: later models would be cheaper. The problem was that Xerox refused to sell the thing in the 70s. They saw the potential of a paperless office, and it scared them. Sure, they could sell a computer, once. They wouldn’t get a monthly service fee, nor the cost of the toner, drums and other consumables the Alto wouldn’t need. So they sat on it, and let others like Steve Jobs who didn’t have an existing business empire to lose take their ideas and run with them.

It seems shortsighted, but Xerox had already lost millions on big iron computing around the same time the Alto came along, and every business decision after that was carefully weighed on its projected revenue. Compared to a copier that printed money for Xerox as surely as it printed paper, the Alto just didn’t look like it could pay for itself. It looked likely to lose them a lot of money, which, in fact the adoption of the personal computer ultimately did. Hindsight is 20/20 and it’s easy to play Monday Morning Quarterback and say these developments were inevitable and Xerox should have run out in front, but [Ctrl+Alt+Fail] does a good job of explaining the logic from the Xerox boards’ point of view, which makes the video very much worth a watch.

If you can’t get enough Alto, we can also point you to what it takes to restore one, what almost killed one, and why you shouldn’t mine bitcoin with one.

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Tracking Bees With A Stereo Camera

August 8, 2026 by 4 Comments

For whatever reason, [Jeremy] wants to photograph bees in flight. This is one of those things that doesn’t seem that hard until you try to do it. He’s got the mechanical part that can move the camera as fast as the bee flies. But you still have to point the camera correctly. He considered quite a few methods of acquiring and tracking the bee, but he finally settled on a stereo camera. His requirements also made the camera design challenging. In particular, the bees move fast enough that things like USB transmission times become significant. You can see his solution in the video below.

[Jeremy] does a great job explaining all the tradeoffs between frame rate, resolution, focal length, and other optical issues. Of course, he also wanted a global shutter sensor. Rolling shutter cameras scan row-by-row, creating the well-known “jello effect”. Global shutters capture all pixels at once. That also removes any uncertainty as to “when” the shutter fired.

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High-Density Parchment Paper Papertronics With Laser-Carved Hydrophilic Channels

August 8, 2026 by 4 Comments

Paper as a substrate for electronic circuits is not very common, but promising for flexible circuits with low cost and easy recyclability. That said, paper is not an easy material to work with when printing traces, as the cellulose material is both absorbent and irregular, limiting the resolution and accuracy of so-called papertronics. Even when using higher-quality paper with wax-based masks this resulted in poor resolution issues, so [Zahra Rafiee] et al. opted to approach the problem from the other direction, by using hydrophobic parchment paper as the base combined with a laser.

The nice thing about the inks used with papertronics that they aren’t just traces, but can also be functional elements like resistors, which is also demonstrated in the paper. The channels for the inks are created using a 50 Watt CO2 laser, which etches away the silicone coating on the parchment paper. The achieved resolution in the article is around 250 µm for line widths and 300 µm line spacing, which is much better than that for wax-based alternatives.

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Track Bird Visitors With A Raspberry Pi And A USB Mic

August 8, 2026 by 16 Comments

Avian Visitors is a lovely project by [Teddy Warner] that uses a Raspberry Pi and microphone to keep track of which birds have been visiting your home, and creates a colorful illustration of recent visitors on top of it all.

It reports on a web interface of its own making, but what really takes things to a new level is an optional, stylish E-Ink panel that shows the last 24 hours’ worth of visitors at a glance in a collage.

The key to identification is BirdNET (GitHub here), a deep learning classifier from Cornell that can reliably identify and classify more than 11,000 species worldwide based on sound alone.

Based on that information, the system pulls bird images from a reference set for the region and creates a collage representing the breadth and frequency of visitors in a single image. The larger the image of a bird, the more frequently it was heard.

That’s a cool project, but [Teddy] took things one step further by setting up a color E-Ink display to show a running summary of all the avian visitors the system identifies. [Teddy] has a knack for leveraging projects into wall-mounted art, as we saw with his generative art wall plotter. Continue reading “Track Bird Visitors With A Raspberry Pi And A USB Mic” →

Grading Tomatoes With An ESP32 And ML

August 8, 2026 by 6 Comments

If you’ve ever worked with produce, you might know about grading. In addition to deciding if, say, a strawberry is good or not, they also have to sort them by color. Turns out, you don’t care if one package of berries is a bit redder than another, but you do care if one package has too much color variation. [Pmalfa31] applied an ESP32 and machine learning to grading tomatoes.

The system knows in advance if you are processing standard tomatoes or cherry tomatoes and uses two different sets of learned data depending on which you select. The program receives raw data from an optical sensor and then processes it to remove empty belt images, compute statistical information, and group readings for a single fruit together.

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Robotic Screw And Bolt Sorter Seeks A New Challenge

August 8, 2026 by 16 Comments

As someone who disassembles and repairs hardware, [Aad] eventually ended up with a huge collection of mixed bolts and screws. This led to creating the automatic bolt and screw sorting system you see here, although in a way it is just a proof of concept. Bolts and screws happen to be a useful application for now, but the system is capable of sorting just about any small objects.

A bit of machine vision detects the size and shape of each object. Weight can also be measured.

Mixed pieces go onto a large conveyor belt, shown on the right. This feeds a few screws at a time down a chute, where they roll onto an illuminated platform.

Above the lit platform is a camera, and machine vision is used to detect the size and shape and orientation of each screw. A robotic gripper on a gantry picks the screws up one by one — separating them first if they happened to clump together — and places each in a drop-off cart. The cart drops the object into a receptacle with its brethren, making sure similar ones are grouped together. Watch it in action in the video, embedded below the page break.

It’s a great build that shows fancy components aren’t necessary for good results. Servos and steppers are controlled with an ESP32-WROOM board, and a piezo sensor detects screws falling off the conveyor. Some of you may have noticed a repurposed Ultimaker 3D printer serving as the bulk of the system, its hot end having been replaced with a gripper that can raise and lower. The overhead camera is an ESP32-CAM adapted to accept M12 lenses so it can focus on the platform.

There’s one more feature worth mentioning — the system also has the ability to measure the weight of a picked object by placing it onto a moveable inspection platform, which can optionally put it under a USB microscope for a closer look. Everything is controlled by a nearby PC, so there’s a lot of flexibility built into the system.

We suppose that once all the screws and bolts in a shop are sorted, it only makes sense to sort all the nuts. Are there other objects besides screws and bolts that would be useful to sort with a system like this? If you have any ideas, don’t keep them to yourself! [Aad] would love to hear your comments and ideas, so share them below.

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