[JanTec Engineering] was fascinated by the idea of using a 3D printer’s hot end to inject voids and channels in the infill with molten plastic, leading to stronger prints without the need to insert hardware or anything else. Inspiration came from two similar ideas: z-pinning which creates hollow vertical channels that act as reinforcements when filled with molten plastic by the hot end, and VoxelFill (patented by AIM3D) which does the same, but with cavities that are not uniform for better strength in different directions. Craving details? You can read the paper on z-pinning, and watch VoxelFill in (simulated) action or browse the VoxelFill patent.

With a prominent disclaimer that his independent experiments are not a copy of VoxelFill nor are they performing or implying patent infringement, [JanTec] goes on to use a lot of custom G-code (and suffers many messy failures) to perform some experiments and share what he learned.

One big finding is that one can’t simply have an empty cylinder inside the print and expect to fill it all up in one go. Molten plastic begins to cool immediately after leaving a 3D printer’s nozzle, and won’t make it very far down a deep hole before it cools and hardens. One needs to fill a cavity periodically rather than all in one go. And it’s better to fill it from the bottom-up rather than from the top-down.

He got better performance by modifying his 3D printer’s hot end with an airbrush nozzle, which gave about 4 mm of extra length to work with. This extra long nozzle could reach down further into cavities, and fill them from the bottom-up for better results. Performing the infill injection at higher temperatures helped fill the cavities more fully, as well.

Another thing learned is that dumping a lot of molten plastic into a 3D print risks deforming the print because the injected infill brings a lot of heat with it. This can be mitigated by printing the object with more perimeters and a denser infill so that there’s more mass to deal with the added heat, but it’s still a bit of a trouble point.

[JanTec] put his testing hardware to use and found that parts with infill injection were noticeably more impact resistant than without. But when it came to stiffness, an infill injected part resisted bending only a little better than a part without, probably because the test part is very short and the filled cavities can’t really shine in that configuration.

These are just preliminary results, but got him thinking there are maybe there are possibilities with injecting materials other than the one being used to print the object itself. Would a part resist bending more if it were infill injected with carbon-fibre filament? We hope he does some follow-up experiments; we’d love to see the results.

Not that it’s the kind of thing that pops into your head often, but if you ever do think of a cyanotype print, it probably doesn’t conjure up thoughts of modern technology. For good reason — the monochromatic technique was introduced in the 1840s, and was always something of a niche technology compared to more traditional photographic methods.

The original method is simple enough: put an object or negative between the sun and a UV-sensitive medium, and the exposed areas will turn blue and produce a print. This modernized concept created by [Gabe] works the same way, except both the sun and the negative have been replaced by a lightly modified resin 3D printer.

A good chunk of the effort here is in the software, as [Gabe] had to write some code that would take an image and turn it into something the printer would understand. His proof of concept was a clever bit of Python code that produced an OpenSCAD script, which ultimately converted each grayscale picture to a rectangular “pixel” of variable height. The resulting STL files could be run through the slicer to produce the necessary files to load into the printer. This was eventually replaced with a new Python script capable of converting images to native printer files through UVtools.

On the hardware side, all [Gabe] had to do was remove the vat that would usually hold the resin, and replace that with a wooden lid to both hold the UV-sensitized paper in place and protect the user’s eyes. [Gabe] says there’s still some room for improvement, but you wouldn’t know it by looking at some of the gorgeous prints he’s produced already.

No word yet on whether or not future versions of the project will support direct-to-potato imaging.

Most Christmas ornaments just hang there and look pretty. [Sean Hodgins] decided to whip up something altogether fancier and more mechanical. It’s a real working marble machine that hangs from the tree!

The build is simple enough, beginning with a translucent Christmas ornament shell readily available from most craft stores. Inside, a small motor spins a pinion, which turns a larger gear inside the body. As the larger gear spins, magnets embedded inside pick up steel balls from the base of the ornament and lift them up to the top. As they reach their zenith, they’re plucked off by a scoop, and then they roll down a spiral inside. As for power, [Sean] simply handled that with a couple of wires feeding the motor from a USB power bank. Just about any small battery pack would do fine.

The build is beautiful to watch and to listen to, with a gentle clacking as the balls circulate around. Files are on MakerWorld for the curious. We’ve featured some great Christmas decorations before, too. Video after the break.

One can 3D print with conductive filament, and therefore plausibly create passive components like resistors. But what about active components, which typically require semiconductors? Researchers at MIT demonstrate working concepts for a resettable fuse and logic gates, completely 3D printed and semiconductor-free.

Now just to be absolutely clear — these are still just proofs of concept. To say they are big and perform poorly compared to their semiconductor equivalents would be an understatement. But they do work, and they are 100% 3D printed active electronic components, using commercially-available filament.

How does one make a working resettable fuse and transistor out of such stuff? By harnessing thermal expansion, essentially.

The conductive filament the researchers used is Electrifi by Multi3D, which is PLA combined with copper micro-particles. A segment printed in this filament is normally very conductive due to the densely-packed particles, but as temperature increases (beginning around 40° C) the polymer begins to soften and undergoes thermal expansion. This expansion separates the copper particles, causing a dramatic increase in electrical resistance as electrical pathways are disrupted. That’s pretty neat, but what really ties it together is that this behavior is self-resetting, and reversible. As long as the PLA isn’t straight up melted (that is to say, avoids going over about 150° C) then as the material cools it contracts and restores the conductive pathways to their original low-resistance state. Neat!

So where does the heat required come from? Simply passing enough current through the junction will do the job. By carefully controlling the size and shape of traces (something even hobbyist filament-based 3D printers are very good at) this effect can be made predictable and repeatable.

The simpler of the two test components uses the resistance spike as a self-resetting fuse. The printed component is designed such that current above a threshold triggers a surge in resistance, preventing damage to some theoretical circuitry downstream. As long as the component is not destroyed by heating it to the point that it melts, it self-resets as it cools.

The transistor is a bit more interesting. By designing two paths so that they intersect each other, one can be used as a control path and the other as a signal path. Applying a voltage to the control path electrically controls the resistance of the signal path, effectively acting as a transistor. Researchers combined these basic transistors into NOT, AND, and OR gates. One is shown here.

This whole system is scalable, low-cost, and highly accessible to just about anyone with some basic equipment. Of course, it has some drawbacks. The switching speed is slow (seconds rather than nanoseconds) and being thermally-driven means power consumption is high. Still, it’s pretty nifty stuff. Check out the research paper for all the nitty-gritty details.

We’ve seen 3D printed triboelectric generators so it’s pretty exciting to now see printed active electronic components. Maybe someday they can be combined?

Vacuum forming is perhaps one of the less popular tools in the modern maker arsenal, something which surprises us a bit because it offers many possibilities. We’ve created our own vacuum forms on 3D printed moulds for ages, so it’s interesting to see [Pisces Printing] following the same path. But what you might not realize at first is that the vacuum forming sheets themselves are also 3D printed.

The full video is below the break, and in it he details making a mould from PETG, and in particular designing it for easy release. The part he’s making is a belt guard for a table top lathe, and the PETG sheet he’s forming it from is also 3D printed. He makes the point that it’s by no means perfect, for example he shows us a bit of layer separation, but it seems promising enough for further experimentation.  His vacuum forming setup seems particularly small, which looks as though it makes the job of making a sheet somewhat simpler.

The cost of a vacuum forming sheet of whichever polymer is hardly high, so we can’t see this technique making sense for everyday use. But as we’ve seen in previous experiments, the printed sheets so make it easy to add color and texture to the final product, which obviously adds some value to the technique.

Thanks [Tomas Harvie Mudrunka] for the tip.

Good news for everyone who cannot get enough from improbably shaped boats that get referred to as a bench: the current owner (NTI Group) of the copyright has announced that 3DBenchy has been released into the public domain. This comes not too long after Prusa’s Printables website had begun to purge all derived models to adhere to the ‘no derivatives’ license. According to NTI, the removal of these derived models was not requested by NTI, but by a third-party report, unbeknownst to NTI or the original creator of the model. Recognizing its importance to the community, 3DBenchy can now be downloaded & modified freely.

NTI worked together with the original creator [Daniel Norée] and former Creative Tools CEO [Paulo Kiefe] to transition 3DBenchy and the associated website to the public domain, with the latter two having control over the website and associated social media accounts. Hopefully this means that the purged models on Printables can be restored soon, even if some may prefer to print alternate (literal) benches.

The unfortunate part is that much of this mess began courtesy of the original 3DBenchy license being ignored. If that point had been addressed many years ago instead of being swept under the rug by all parties involved, there would have been no need for any of this kerfuffle.

If you’re taking any medication, you probably need to take it in a certain dose on a certain schedule. It can quickly become difficult to keep track of when you’re taking multiple medications. To that end, [Mellow_Labs] built an automated pill dispenser to deliver the right pills on time, every time.

The pill dispenser is constructed out of 3D printed components. As shown, it has two main bins for handling two types of pills, controlled with N20 gear motors. The bins spin until a pill drops through a slot into the bottom of the unit, with the drop detected by a piezo sensor. It uses a Beetle ESP32 as the brains of the operation, which is hooked up with a DS1307 real-time clock to ensure it’s dosing out pills at the right time. It’s also wired up with a DRV8833 motor driver to allow it to run the gear motors. The DRV8833 can run up to four motors in unidirectional operation, so you can easily expand the pill dispenser up to four bins if so desired.

We particularly like how the pill dispenser is actually controlled — [Mellow_Labs] used the ESP32 to host a simple web interface which is used for setting the schedule on which each type of pill should be dispensed.

We’ve featured some other pill dispenser builds before, too.

Thanks to [Prankhouz] for the tip!