3D Printing Compressed Air Tanks

Using PVC pipe as a pressure vessel for compressed air can be a fun and enjoyable hobby. It’s safe, too: while there are are reports of PVC pipe being the cause of accidents, these accidents include a black powder potato gun[1], and welding too close to a PVC pipe containing compressed air[2]. Compressed air stored in a PVC pipe is never a proximal cause in any accident, and the OSHA’s Fatality and Catastrophe Investigation Summaries bear this out; there was no industrial or occupational accident recorded in these summaries where a pressure vessel made out of PVC was the cause of any injury or death[3].

Although PVC pipe can be a perfectly safe, effective, and cheap pressure vessel for hobby applications, it’s not always the best choice. A group of students in Renens, Switzerland are building autonomous robots for the Eurobot competition, and this year’s robot uses pneumatics. That means compressed air, and that means a pressure vessel. Since just about everything else on this robot is 3D printed, they asked the obvious question. Is it possible to 3D print a tank for compressed air?

The tank for this robot would only be used up to about 4 bar (400kPa), and after a few quick calculations, the team discovered the wall thickness – even in a pressure vessel with corners – would be pretty low. The first prototype, a 40mm cube with 20% infill and a hole drilled in the side, held 6.5 bar (650kPa) for an hour. This success didn’t last, though: he second prototype, a 65x40x80mm rectangular prism printed without as much infill, exploded at 5.5bar (550kPa).

The third time’s the charm, and with filleted ribs inside the tank, the third prototype was able to hold pressure up to 6.5 bar. Of course no 3D print is perfect, and the third prototype did leak, but a bit of acrylic spray paint applied to the outer surfaces held the air in.

While it’s not as fun, easy, cheap, rewarding, or safe as using PVC pipe as a pressure vessel, the team did manage to build a 3D printed pressure vessel with a custom shape. You can’t do that very easily with round pipe. And 3D printing opens up all manner of internal structure to experiment with. We’d like to see this developed even further!

Sources: [1], [2], [3]

Motorized Music Box Cranks Out Stairway to Heaven

[Bokononestly] found a lil’ music box that plays Stairway to Heaven and decided those were just the kinds of dulcet tones he’d like to wake up to every morning. To each his own; I once woke up to Blind Melon’s “No Rain” every day for about six months. [Bokononestly] is still in the middle of this alarm clock project right now. One day soon, it will use a *duino to keep track of the music box’s revolutions and limit the alarm sound to one cycle of the melody.

stairway-musicbox-alarm-clock[Bokononestly] decided to drive the crank of the music box with a geared DC motor from an electric screwdriver. After making some nice engineering drawings of the dimensions of both and mocking them up in CAD, he designed and printed a base plate to mount them on. A pair of custom pulleys mounted to the motor shaft and the crank arm transfer motion using the exact right rubber band for the job. You can’t discount the need for a big bag ‘o rubber bands.
In order to count the revolutions, he put a wire in the path of the metal music box crank and used the body of the box as a switch. Check out the build video after the break and watch him prove it with the continuity function of a multimeter. A clever function that should at some point be substituted out for a leaf switch.

We’ve covered a lot of cool clock builds over the years, including one or two that run Linux. And say what you will about Stairway; it’s better than waking up to repeated slaps in the face.

Continue reading “Motorized Music Box Cranks Out Stairway to Heaven”

Hacklet 109 – Complex 3D Printed Projects

If you can’t tell, we’re on a roll with 3D printers and printed projects this month. So far, we’ve covered printers, and simple functional 3D prints. This week we’re taking a look at some of the awesome complex 3D printed projects on Hackaday.io.

Complex 3D printed projects are things like robots, quadcopters, satellite tracking systems, and more. So let’s jump in and look at some of the best complex 3D printed projects on Hackaday.io!

dtto2We start with [Alberto] and Dtto v1.0 Modular Robot. Dtto is [Alberto’s] entry in the 2016 Hackaday Prize. Inspired by Bruce Lee’s famous water quote, Dtto is a modular snake-like robot. Each section of Dtto is a double hinged joint. When two sections come together, magnets help them align. A servo controlled latch solidly docks the sections, which then work in unison. Dtto can connect and separate segments autonomously – no human required. [Alberto] sees applications for a robot like [Dtto] in search and rescue and space operations. Continue reading “Hacklet 109 – Complex 3D Printed Projects”

Sweet 3D Printer

Dylan’s Candy Bar is an upscale sweet shop in Manhattan. In a stunning proof that 3D printing has become buzzword-worthy, they’ve announced a deal with Katjes Magic Candy Factory to bring four 3D gummy printers to the US (specifically, to New York, Chicago, Los Angeles, and Miami).

The device looks a bit like a classic 3D printer, but it extrudes eight different gummis in a variety of flavors. The store offers twenty designs but you can also print text or your own drawings (including, apparently, your face).

Each creation costs about $20. Time will tell if this is just a stunt, or if we are going to see food printers cropping up at a mall near you. You can see a video they posted to Twitter below along with a video from the product roll out of the printer in question.

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3D Printing Metal in Mid Air

Published only 3 days before our article on how it is high time for direct metal 3D printers, the folks at Harvard have mastered 3D metal printing in midair with no support (as well as time travel apparently). Because it hardens so quickly, support isn’t necessary, and curves, sharp angles, and sophisticated shapes are possible.

The material is silver nanoparticles extruded out of a nozzle, and shortly after leaving it is blasted with a carefully programmed laser that solidifies the material. The trick is that the laser can’t focus on the tip of the nozzle or else heat transfer would solidify the ink inside the nozzle and clog it. In the video you can see the flash from the laser following slightly behind. The extrusion diameter is thinner than a hair, so don’t expect to be building large structures with this yet.

If you want big metal 3D printing, you should probably stick to the welders attached to robotic arms.

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3D Print It Or Fix It?

[Tim Trzepacz] is working on a pretty cool MIDI controller project over on Hackaday.io. It involves, naturally, a bunch of knobs and buttons. And it’s one of these nice arcade-style buttons that broke when he slammed on his car brakes and it went flying.

He tried gluing the plastic bits back together, but we all know how that works — temporarily. Next, he thought that maybe he could 3D-print a model of the arcade button’s housing. Besides being a lot of work, [Tim] didn’t have a reliable printer on hand. But he did have filament and a soldering iron.

The rest of the story is a slightly ugly mess, but it looks like it’ll work. (And it’s on the inside of the case, after all.) A working part is a good part.

The irony here is that the original choice of 3 mm ABS filament as a printing material is that it’s cheap and available because it’s commonly used in plastic welding. And there are more elegant ways to melt the plastic than with a soldering iron. And more ways to get it melted than direct heating, like ultrasonic welding and friction welding, for instance.

But we still like to see the occasional quickly hacked together effort, at least one per day. What’s your craziest plastic welding success or failure?

Hacklet 108 – Simple Functional 3D Prints

We featured 3D printer projects on last week’s Hacklet. This week, we’re looking at a few awesome projects created with those printers. Trying to pick great 3D printed projects on Hackaday.io is a bit like staring at the sun. There are just way too many to choose from. To make things a bit easier, I’ve broken things down into categories. There are artistic prints, complex mechanical or electronic prints, and then there are simple functional prints, which is the topic we’re featuring today. Simple functional prints are designs which perform some function in the world. By simple, I mean they have only a few moving parts or electronic components. Let’s get right to it!

cornersWe start with [Scott] and L Extrusion Endcaps. Every Home Depot, Lowes, or hardware store has a selection of extruded aluminum. Typically there are a few flat bars, and some L brackets. L brackets are great, but they can be a pain to work with. Most of us don’t have the skills or the tools to weld aluminum, so nuts and bolts are the only way to go. [Scott’s] given us another option. He’s designed a set of 3D printable brackets that slip onto the ends of the brackets. The brackets make quick work of building boxes, racks, or anything with 90° or 45° angles.


earbudNext up is [Joe M] with 3D Printed Molds: Custom Silicone Earbuds. [Joe] had a set of Bluetooth earbuds he enjoyed, but the rubber tips left a bit to be desired. Not a problem when you have a 3D printer on hand. [Joe] measured the plastic part of his earbuds and the rubber tips from a different set he liked. A bit of CAD magic later, and he had a model for the perfect earbud tip. While he could have directly printed the tip in a flexible filament like NinjaFlex, [Joe] opted for a pure silicone tip. He printed molds, then mixed silicone caulk with cornstarch (as a catalyst). The resulting earbuds sound and feel great!

coil2Next we have [Jetty] with Highly Configurable 3D Printed Helmholtz Coil. Helmholtz coils are used to create uniform magnetic fields. Why would you want to do that? It could be anything from measuring magnets to cancelling out the effect of the earth’s magnetic field on a device being tested. [Jetty’s] wrote an OpenScad program which allows the user to enter parameters for their coil. [Jetty’s] program then calculates the coil’s magnetic properties, and outputs a printable .stl file. Building the coil is as simple as printing it and wrapping some copper wire. [Jetty] found that his coil was within 60nT (nanoTesla) of the expected value. Not bad for a bit of plastic and wire!


scope1Finally we have StickScope,  [SUF’s] entry in the 2016 Hackaday Prize. Like many of us, [SUF] loves his StickVise. Sometimes you need a bit of magnification to see those tiny 0201 resistors though. [SUF] had a cheap USB microscope on hand, so he designed StickScope, a USB microscope mount designed especially for the StickVise. Two 6mm steel rods are the backbone of the design. 3D printed clamps hold the system together like a miniature boom microscope. This is actually the third revision of the design. [SUF] found that the original design couldn’t be used with parts close to the bar which holds the microscope. A small jaw extender was the perfect tweak.


If you want to see more simple functional 3D printed projects, check out our new simple functional 3D prints list! If I missed your project, don’t be shy, just drop me a message on Hackaday.io. That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!