Printed Circuits In The Palm Of Your Hand

If you’ve ever wanted to more fully integrate yourself with technology, you might have to thank a team of researchers — led by [Michael McAlpine] — at the University of Minnesota in the near future. They’ve developed a technique that allows circuits to be printed directly onto your skin, with the team arguing — once the low-cost printer is modified for compact portability — it would be ideal for ‘on-the-fly’ circuit needs.

“But the hand isn’t exactly a stable print bed,” you say. We hear you, and the team is actually one step ahead — the printer can compensate for subtle movements during the printing process by tracking markers placed on the hand. The ‘filament’ is made from silver flakes — akin to conductive ink — which prints and cures at room temperatures, and can be either peeled or washed off. We should hope so, as it’s meant to be layered on human skin.

Speaking of which, it can also print cells!

It’s only been tested on a mouse so far, but the same technology that allows the printer to accurately track the hand means that it could use bio-ink to directly add cells to a wound or some other epidermal affliction to help speed the healing process.

For the circuits, though, you’ll still need the other circuit components and a compact means to power them — to say nothing about the fact that if the circuit is water-soluble, then a little perspiration would cause the ink to run. We’re excited to see where this tech goes!

[Thanks for the tip, Qes!]

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Make 3D-Modeling Child’s Play With A Can Of Play-Doh

You need to replicate a small part on a 3-D printer, so you start getting your tools together. Calipers, rulers, and a sketch pad at a minimum, and if you’re extra fancy, maybe you pull out a 3D-scanner to make the job really easy. But would you raid your kid’s stash of Play-Doh too?

You might, if you want to follow [Vladimir Mariano]’s lead and use Play-Doh for accurately modeling surface features in the part to be replicated. Play-Doh is a modeling compound that kids and obsolete kids alike love to play with, especially a nice fresh can before it gets all dried out or mixed in with other colors or gets dog hair stuck in it.

For [Vladimir], the soft, smooth stuff was the perfect solution to the problem of measuring the spacing of small divots in the surface of a cylinder that he was asked to replicate. Rather than measuring the features directly on the curved surface, he simply rolled it across a flattened wad of Play-Doh. The goop picked up the impressions on the divots, which were then easy to measure and transfer to Fusion 360. The video below shows the Play-Doh trick up front, but stay tuned through the whole thing to get some great tips on using the sheet metal tool to wrap and unwrap cylinders, as well as learning how to import images and recalibrate them in Fusion 360.

Run into a modeling problem that Play-Doh can’t solve? Relax, we’ve got a rundown on the basics for you.

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3D Printed Tank Scores Suspension

Tanks are highly capable vehicles, with their tracks giving them the ability to traverse all manner of terrain at speed. An important part of a tank is its suspension setup, without which its treads are far less capable. When [Ivan]  began work on his 3D printed tank project, he couldn’t ignore the comments. His tank would need a suspension system.

The tank build itself is impressive, consisting almost entirely of 3D printed components held together with off-the-shelf bearings and threaded rod. [Ivan] retools the tank from the beginning to fit a pivoting suspension system which is surprisingly simple in its design, yet capable in operation. Particularly impressive are the 3D printed springs, which [Ivan] tunes the stiffness of to suit the weight of the vehicle.

It’s a build that shows just how far you can go when you master the basics of 3D printing and mechanical design. It doesn’t take a lot of advanced theory to design cool things, just a willingness to learn and experiment and the right set of tools behind you. [Ivan]’s tank treads are worth taking a look at, too. Video after the break.

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Smooth PLA Through The Fire And Flames

3D printing makes it easy to produce complex geometries, but the fused deposition methods generally create parts with poor surface finish, largely due to the layers being highly visible in the finished part. There are a wide variety of ways to deal with this, often involving sanding parts after production, or the use of fillers and paints. [XerotoLabs] has another solution. (YouTube, video below the break.)

To smooth the parts, a butane torch is pressed into service. The flame temperature is kept fairly low, and the torch is used almost like a brush to evenly apply heat to the surface of the part. As the PLA reaches its melting temperature, surface tension helps to smooth the part out. This is very similar to flame polishing which is commonly used in the fabrication of acrylic plastics.

It is a technique that requires some finesse – too much heat or focus on a single area, and you’re liable to end up with a molten plastic blob instead of a nice shiny finished part. Precautions must also be taken to avoid burning yourself or your workshop to the ground. But it’s a useful tool to have in your kit when you’re producing PLA parts that you want to look their best.

We’ve seen other techniques for smoothing PLA, too – the solvent method is particularly interesting. Continue reading “Smooth PLA Through The Fire And Flames”

3D Printering: Which Raspberry Pi Is Best At Slicing In Octoprint?

OctoPrint is arguably the ultimate tool for remote 3D printer control and monitoring. Whether you simply want a way to send G-Code to your printer without it being physically connected to your computer or you want to be able to monitor a print from your phone while at work, OctoPrint is what you’re looking for. The core software itself is fantastic, and the community that has sprung up around the development of OctoPrint plugins has done an incredible job expanding the basic functionality into some very impressive new territory.

RAMBo 3D controller with Pi Zero Integration

But all that is on the software side; you still need to run OctoPrint on something. Technically speaking, OctoPrint could run on more or less anything you have lying around the workshop. It’s cross platform and doesn’t need anything more exotic than a free USB port to connect to the printer, and people have run it on everything from disused Windows desktops to cheap Android smartphones. But for many, the true “home” of OctoPrint is the Raspberry Pi.

As I’ve covered previously, the Raspberry Pi does make an exceptional platform for OctoPrint. Given the small size and low energy requirements of the Pi, it’s easy to integrate into your printer. The new Prusa i3 MK3 even includes a header right on the control board where you can plug in a Raspberry Pi Zero.

But while the Raspberry Pi is more than capable of controlling a 3D printer in real-time, there has always been some debate about its suitability for slicing STL files. Even on a desktop computer, it can sometimes be a time consuming chore to take an STL file and process it down to the raw G-Code file that will command the printer’s movements.

In an effort to quantify the slicing performance on the Raspberry Pi, I thought it would be interesting to do a head-to-head slicing comparison between the Pi Zero, the ever popular Pi 3, and the newest Pi 3 B+.

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The Quest For The Reuleaux Triangle Bearing

[Angus Deveson] published a video on “solids of constant width” nearly a year ago. Following the release of the video, he had a deluge of requests asking if he could make a bearing from them. Since then, he’s tried a number of different approaches – none of which have worked. Until now…

What is a solid of constant width? A shape whose diameter is the same in all orientations, despite the fact that they aren’t circular. In particular, the Reuleaux Triangle is of interest; if you’ve heard of square drill bits, a Reuleaux Triangle is probably at play. Constructed from three circles, they make a neat geometrical study. When placed between two surfaces and rolled, the surfaces will stay parallel, despite the fact that the center of the triangle does not stay level.

In theory, this means they could be easily substituted for spheres in a classic roller bearing, but this turned out to be problematic – the first attempt determined how hard it was to get the shapes to roll instead of slide.

[Angus] finally arrived at a working bearing after a ton of suggestions from the community, and trying a number of attempts until he was able to achieve what he set out to do. The trick was to create a flexible insert (3D printed as well) for the center of the triangle edge, which grips the surfaces the triangle comes into contact with. A frame is also made to hold the bearings in place and allows their centers to move up and down as necessary.

If the thrill seeker within you still isn’t satisfied, maybe you should try the Reuleaux Coaster

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Hard Drive Gives Its Life To Cool 3D Prints

[Mark Rehorst] has been on the hunt for the perfect 3D printer cooling fan and his latest take is a really interesting design. He’s printed an impeller and housing, completing the fan using a hard drive motor to make it spin.

We should take a step back to see where this all began. Many 3D printers us a cooling fan right at the tip of the extruder because the faster you faster you cool the extruded filament, the fewer problems you’ll have with drooping and warping. Often this is done with a small brushless fan mounted right on the print head. But that adds mass to the moving head, contributing to problems like overshoot and oscillation, especially on larger format printers that have longer gantries. [Mark] just happens to have an enormous printer we covered back in January and that’s the machine this fan targets.

CPAP fan and duct tubing

Make sure you give [Mark’s] Mother of all print cooling fans article a look. His plan is to move the fan off of the print head and route a flexible tube instead. He tried a couple of fans, settling on one he pulled from a CPAP machine (yes the thing you wear at night to combat sleep apnea) found in the parts bin at Milwaukee Makerspace. It works great, moving quite a bit more air than necessary. The problem is these CPAP parts aren’t necessarily easy to source.

You know what is easy to source? Old hard drives. [Mark] mentions you likely have one sitting around and if not, your friends do. We have to agree with him. Assuming you already have a 3D printer (why else do you want to print this fan?), the only rare part in this mix is the ESC to make the motor spin. Turns out we just saw a BLDC driver build that would do the trick. But in [Mark’s] case he found a rather affordable driver that suits his needs which is used in the video demo below.

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