Building A UV Curing Station For Resin Prints

September 5, 2020 by Lewin Day 10 Comments

Resin printers have a lot going for them – particularly in regards to quality surface finishes and excellent reproduction of fine details. However, the vast majority rely on UV light to cure prints. [douwe1230] had been using a resin printer for a while, and grew tired of having to wait for sunny days to cure parts outside. Thus, it was time to build a compact UV curing station to get the job done.

The build consists of a series of laser-cut panels, assembled into a box one would presume is large enough to match the build volume of [douwe1230’s] printer. UV LED strips are installed in the corners to provide plenty of light, and acrylic mirrors are placed on all the walls. The use of mirrors is key to evenly lighting the parts, helping to reduce the likelihood of any shadows or dead spots stopping part of the print from curing completely. In the base, a motor is installed with a turntable to slowly spin the part during curing.

[Douwe1230] notes that parts take around about 10 minutes to cure with this setup, and recommends a flip halfway through to make sure the part is cured nice and evenly. We’ve seen other similar DIY builds too, like this one created out of a device aimed at nail salons. If you’re struggling with curing outside, with the weather starting to turn, this might just be the time to get building!

A 3D Printed Paint Mixer

August 31, 2020 by Danie Conradie 9 Comments

To get the perfect mix for your paint, you need a good shake that is as random as possible. [Mark Rhodes] wanted to automate the process of mixing paint, so he built a 3D printed shaker to thoroughly shake small paint bottles. Using only a single motor, it shakes the bottle along three axes of rotation and one axis of translation.

A cylindrical container is attached to a U-shaped bracket on each end, which in turn is attached to a rotating shaft. Only one of these shafts are powered, the other is effectively an idler. When turned on, it rotates the cylinder partially around the pitch and yaw axis, 360 degrees around the roll axis, and reciprocates it back and forth. The design appears to be based on an industrial mixer known as a “Turbula“. Another interesting feature is how it holds the paint bottle in the cylinder. Several bands are stretched along the inside of the cylinder, and by rotating one of the rings at the end, it creates an hourglass-shaped web that can tightly hold the paint bottle.

The mechanism is mounted on a 3d printed frame that can be quickly clamped to a table. The Twitter post embedded below is a preview for a video [Mark] is working for his Youtube channel, along with which he will also release the 3D files.

Mixing machines come in all shapes and sizes, and we’ve seen a number of 3D printed versions, including a static mixer and a magnetic stirrer.

Continue reading “A 3D Printed Paint Mixer” →

100% Printed Flashlight: Conductive Filament And Melted-in Leads

August 31, 2020 by Donald Papp 28 Comments

Conductive filament isn’t an ideal electrical conductor, but it’s a 3D-printable one and that’s what makes [Hercemer]’s 3D-printed flashlight using conductive filament work. Every part of the flashlight is printed except for the 9 volt battery and LEDs. Electrically speaking, the flashlight is a small number of LEDs connected in parallel to the terminals of the battery, and turning it on or off is done by twisting or loosening a cap to make or break the connection.

The main part of the build is a 3D-printed conductive cylinder surrounded by a printed conductive ring with an insulator between them. This disk- or pad-shaped assembly forms not only the electrical connection between the LEDs and battery terminals, but also physically holds the LEDs. To attach them, [Hercemer] simply melts them right in. He uses a soldering iron to heat up the leads, and presses them into the 3D-printed conductive block while hot. The 9 V battery’s terminals contact the bottom when the end cap is twisted, and when they touch the conductive assembly the flashlight turns on.

Anode of each LED goes to the center, cathodes to the outside ring.

LED leads are melted-in with a soldering iron.

9 V battery pressed to the bottom of the conductive block lights up the LEDs.

Anticipating everyone’s curiosity, [Hercemer] measured the resistance of his conductive block and measured roughly 350 ohms when printed at 90% infill; lower infills result in more resistance. You can see a video of the assembly and watch the flashlight in action in the video, embedded below.

Continue reading “100% Printed Flashlight: Conductive Filament And Melted-in Leads” →

Impossibilities And 3D Printing

August 29, 2020 by Elliot Williams 43 Comments

This week our own [Donald Papp] wrote a thought-provoking piece on buying and selling 3D-printer models. His basic point: if you don’t know what you’re getting until you’ve purchased it, and there’s no refund policy, how can you tell if your money is being well spent? It’s a serious problem for these nascent markets, because when customers aren’t satisfied they won’t come back.

It got me thinking about my own experience, albeit with all of the free 3D models out there. They are a supremely mixed bag, and even though you’re not paying for the model, you’re paying in printing time, filament, and effort. It pays to be choosy, and all of [Donald]’s suggestions hold in the “free” market as well.

Only download models that have been printed at least once, have decent documentation about things like layer height, filament type, and support, and to the best of your abilities, be critical about the ability to fabricate the part at all. Fused-deposition printers can only print on top of previous layers, and have a distinct grain, so you need to watch out for overhangs and print orientation. With resin printers, you need to be careful about trapped volumes of uncured resin. You want to be sure that the modeler at least took these considerations into account.

But when your parts have strength requirements, fits, and tolerances, it gets even worse. There’s almost no way a designer can know if you’re overextruding on your first layers or not. Different slicers handle corners differently, making inner surfaces shrink to varying degrees. How can the designer work around your particular situation?

My personal answer is open-source. Whenever possible, I prefer models in OpenSCAD. If you download an STL with ten M8 bolt holes, you could widen them all in a modeling program, but if you’ve got the source code, it’s as easy as changing a single variable. Using the source plays to the customizability of 3D printing, which is perhaps its strongest suit, in my mind. Nobody knows exactly how thick your desk is but you, after all. Making a headphone hook that’s customizable is key.

So even if the markets for 3D prints can solve the reliability problems, through customer reviews or requirements of extensive documentation, they’ll never be able to solve the one-size-fits-nobody issue. Open source fixes this easily. Sell me the source, not the STL!

Print-in-Place Engine Aims To Be The Next Benchy

August 27, 2020 by Dan Maloney 19 Comments

While there are many in the 3D-printing community who loudly and proudly proclaim never to have stooped to printing a 3DBenchy, there are far more who have turned a new printer loose on the venerable test model, just to see what it can do. But Benchy is getting a little long in the tooth, and with 3D-printers getting better and better, perhaps a better benchmarking model is in order.

Knocking Benchy off its perch is the idea behind this print-in-place engine benchmark, at least according to [SunShine]. And we have to say that he’s come up with an impressive model. It’s a cutaway of a three-cylinder reciprocating engine, complete with crankshaft, connecting rods, pistons, and engine block. It’s designed to print all in one go, with only a little cleanup needed after printing before the model is ready to go. The print-in-place aspect seems to be the main test of a printer — if you can get this engine to actually spin, you’re probably set up pretty well. [SunShine] shares a few tips to get your printer dialed in, and shows a few examples of what can happen when things go wrong. In addition to the complexities of the print-in-place mechanism, the model has a few Easter eggs to really challenge your printer, like the tiny oil channel running the length of the crankshaft.

Whether this model supplants Benchy is up for debate, but even if it doesn’t, it’s still a cool design that would be fun to play with. Either way, as [SunShine] points out, you’ll need a really flat bed to print this one; luckily, he recently came up with a compliant mechanism dial indicator to help with that job.

Continue reading “Print-in-Place Engine Aims To Be The Next Benchy” →

3D Printering: The World Of Non-Free 3D Models Is Buyer Beware

August 26, 2020 by Donald Papp 32 Comments

There are more free 3D models online than one can shake a stick at, but what about paid models? Hosting models somewhere and putting a buy button in front of the download is certainly a solved problem, but after spending some time buying and printing a variety of non-free 3D models online, it’s clear that there are shortcomings in the current system.

What the problems are and how to address them depends a little on the different ways models get sold, but one thing is clear: poorly-designed 3D models are bad for consumers, and bad for the future of pay-to-download in general. Continue reading “3D Printering: The World Of Non-Free 3D Models Is Buyer Beware” →

Stealing Keys From The Sound Of The Lock

August 22, 2020 by Al Williams 27 Comments

If you are smart, you wouldn’t hand your house key over to a stranger for a few minutes, right? But every time you use your key to unlock your door, you are probably broadcasting everything an attacker needs to make their own copy. Turns out it’s all in the sound of the key going into the lock.

Researchers in Singapore reported that analyzing metallic clicks as the key slides past the pins gives them the data they need to 3D print a working key. The journal published research is behind a paywall, but there is a copy on co-author [Soundarya Ramesh’s] website which outlines the algorithm used to decode the clicks of key teeth on lock pins into usable data.

The attack didn’t require special hardware. The team used audio capture from common smartphones. While pushing your phone close to the lock while the victim inserts a key might be problematic, it isn’t hard to imagine a hacked phone or smart doorbell picking up the audio for an attacker. Long-range mikes or hidden bugs are also possible.

There are practical concerns, of course. Some keys have a plateau that causes some clicks to skip, so the algorithm has to deal with that. It sounds like the final result be a small number of key possibilities and not just converge on one single key, but even if you had to carry three or four keys with you to get in, it is still a very viable vulnerability.

The next step is to find a suitable defense. We’ve heard that softening the pins might reduce the click, but we wondered if it would be as well to put something in that deliberately makes loud clicks as you insert the key to mask the softer clicks of the pins.

While a sound recording is good, sometimes a picture is even better. Of course, if you want to go old school, you can 3D print your lockpicks.

Continue reading “Stealing Keys From The Sound Of The Lock” →