UV Sensitive Filament As A Persistent Display

Some of the hacks we feature are modifications of existing devices, others are ground-up builds of entirely new ones. And then there are the experiments, things that have to be worth trying because they just might work. In this final category we have [Matt]’s work with  UV sensitive plastic to form the basis of a simple persistent display, which has created something best described as a proof-of-concept that shows promise, and definitely proves that he had an idea very much worth trying.

The idea makes use of a plastic that changes colour from white to purple when exposed to UV light. He 3D printed a waffle-like structure to locate over a 3×3 grid of UV LEDs, which he could then illuminate under the control of an Arduino Mini Pro. A short illumination changes the colour of the plastic above it, creating a “pixel” that persists for several seconds. In this he has created a working proof of concept for a very simple 3×3 matrix display, albeit rather an unwieldy one. The advantage the idea offers is that a relatively long time of display can be achieved for a relatively short LED illumination, giving a potential for power saving.

The proof-of-concept itself isn’t particularly useful, but from this idea it’s possible a larger display could be practically made. An array of surface-mount LEDs could perhaps illuminate a larger array of plastic to a greater resolution, it’s definitely an idea that was worth trying, and which shows promise for further pursuit. If you’d like to see it in action he’s posted a video, which we’ve placed below the break.

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Fluid Simulations In The Kitchen Sink

In an age of ultra-powerful GPUs and cheap processors, computational techniques which were once only available to those with a government-sized R&D budgets are now available to the everyday hacker. An example of industry buzzword turned desktop software is the field of “computational fluid dynamics”, which put simply allow modeling how gasses or liquids will behave when moving through a cavity under specific conditions. Extensive utilization of these fluid simulations are often cited as one of breakthrough techniques which allowed SpaceX to develop their engine technology so rapidly when compared to Apollo and Shuttle era methods.

But just because anyone with a decent computer has access to the technology used for developing rocket engines doesn’t mean they have to use it. What if you prefer to do things the old-fashioned way? Or what if, let’s me honest, you just can’t figure out how to use software like Autodesk CFD and OpenFOAM? That’s exactly where [Desi Quintans] found himself when developing GUST, his cooling duct for i3-type 3D printers.

[Desi] tried to get the big name fluid simulation projects working with his prototype designs for an improved cooling duct, but had no end of trouble. Either the learning curve was too steep, or the simulation wasn’t accurate enough to give him any useful data. But remembering that air is itself a fluid, [Desi] took his simulation from the computer to the sink in order to better visualize what his cooling duct was doing to the airflow.

[Desi] printed up a box with a hole in the bottom that would connect up to his nozzles under test. As the volume of water in the box would be a constant between tests, he reasoned that this would allow him to evaluate the different nozzles at the same pressure. Sure enough, he found that the original nozzle design he was using caused chaotic water flow, which backed up what he was seeing in his experiments when mounted onto the printer.

After several iterations he was able to tame the flow of water by using internal baffles and fins, which when tested in water created something of a laminar flow effect. When he tried this version on the printer, he saw a clear improvement in part cooling, verifying that the behavior of the air and water was close enough for his purposes.

We’ve seen other projects that successfully used fluid simulations in their design before, but the quick and dirty test procedure [Desi] came up with certainly has its charms.

IceSL Is A Cool Slicer

The mechanical and electronic parts of a 3D printer are critical for success, but so is the slicing software. Slic3r and Cura are arguably the most popular, and how they command your printer has a lot to do with the results you can get. There are lots of other slicers out there both free and paid, but it is hard to really dig into each one of them to see if they are really better than whatever you are using today. If you are interested in the performance of IceSL — a free slicer for Windows and Linux — [DIY3DTECH] has a video review that can help you decide if you want to try it. You can see the video below.

IceSL has several modules and can actually do OpenSCAD-like modeling in Lua so you could — in theory — do everything in this one tool. The review, though, focuses only on the slicing aspect. In addition to the desktop client versions, you can use some features online (although on our Linux machine it didn’t work with the latest Chrome beta even with no add ons; Firefox worked great, though).

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Heat-Set Insert Jig Grants Threads To 3D Prints

FDM 3D prints might be coming home this holiday as seasonal ornaments, but with a few tweaks, they may even stand up to the tests of the real world as functional prototypes. Heat-Set inserts are one such tweak that we can drop into a print, and [Kurt] spares no expense at laying down a guide to get us comfortable with these parts. Here, he’s created a drill press adapter and modified his soldering iron to form an insert jig to start melting these parts into his next project.

Heat-set inserts grant us proper screw threads in any thermoplastic. Simply heat them up, stake them into your part, let cool, and: voila–a screw thread that’s firmly embedded into our part. We can load these inserts with clumsy hand tools, but why fumble and bumble with a hot soldering iron when we can adapt our drill press to do most of the tricky fixturing for us? That’s exactly what [Kurt] did here. With a 3D-printed adaptor, he’s letting his drill press (turned off!) hold the soldering iron so that he can use the lever to slowly stake the part into the 3D print. Finally, for no additional charge, [Kurt] turned down his soldering tip to mate cleanly into the insert for a cleaner removal.

We’ve seen adapters like this one before, but it’s never too often to get a reminder of the structural bonus that these parts can add to our 3D prints.

What Would Sherlock Print, If Sherlock Printed In SLA Resin?

Resin printing — or more appropriately, stereolithography apparatus printing — is a costly but cool 3D printing process. [Evan] from [Model3D] wondered if it was possible to produce a proper magnifying glass using SLA printing and — well — take a gander at the result.

A quick modeling session in Fusion 360 with the help of his friend, [SPANNERHANDS 3D Printing] and it was off to the printer. Unfortunately, [Evan] learned a little late that his export settings could have been set to a higher poly count — the resultant print looked a little rough — but the lens would have needed to be sanded anyway. Lucky coincidence! After an eight hour print on his Peopoly Moai using clear SLA resin, [Evan] set to work sanding.

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Printed Parts Make DIY Electric Longboard Possible

Appalled by expensive electric longboards, [Conor Patrick] still wanted one, and wanted it now. So — naturally — he converted an existing board into a sprightly electric version at a fraction of the cost.

[Patrick] is using a capable 380KV Propdrive motor, capable of pushing him up to 30mp/h! A waterproof 120A speed controller and 6000mAh, 22.2V LiPo battery slim enough to fit under the board give the motor the needed juice. He ended up buying the cheapest RF receiver and remote combo to control the board, but it fit the all-important “want electric long board now” criterion.

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Google’s Inception Sees This Turtle As A Gun; Image Recognition Camouflage

The good people at MIT’s Computer Science and Artificial Intelligence Laboratory [CSAIL] have found a way of tricking Google’s InceptionV3 image classifier into seeing a rifle where there actually is a turtle. This is achieved by presenting the classifier with what is called ‘adversary examples’.

Adversary examples are a proven concept for 2D stills. In 2014 [Goodfellow], [Shlens] and [Szegedy] added imperceptible noise to the image of a panda that from then on was classified as gibbon. This method relies on the image being undisturbed and can be overcome by zooming, blurring or rotating the image.

The applicability for real world shenanigans has been seriously limited but this changes everything. This weaponized turtle is a color 3D print that is reliably misclassified by the algorithm from any point of view. To achieve this, some knowledge about the classifier is required to generate misleading input. The image transformations, such as rotation, scaling and skewing but also color corrections and even print errors are added to the input and the result is then optimized to reliably mislead the algorithm. The whole process is documented in [CSAIL]’s paper on the method.

What this amounts to is camouflage from machine vision. Assuming that the method also works the other way around, the possibility of disguising guns (or anything else) as turtles has serious implications for automated security systems.

As this turtle targets the Inception algorithm, it should be able to fool the DIY image recognition talkbox that Hackaday’s own [Steven Dufresne] built.

Thanks to [Adam] for the tip.