Struggling Robot Made With DIY Soft Limbs

[Jonathan Grizou] is experimenting with robot designs, and recently stumbled upon a neat method for making soft robots. While his first prototype, a starfish like robot, doesn’t exactly “whelm” a person with it’s grace and agility, it proves the concept. Video after the break.

In this robot the frame is soft and the motor provides most of the rigidity for the structure. The soft parts of the frame have hardpoints embedded into them for mounting the motors or joining sections together. The sections are made with 3D printed molds. The molds hold the 3D printed hard points in place. Silicone is poured into the mold and left to cure overnight. The part is then demolded and is ready for use.

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Fail Of The Week: How NOT To Smooth A 3D Print

Many of the Fail Of The Week stories we feature here are pretty minor in the grand scheme of things. At worse, gears are ground, bits are broken, or the Magic Blue Smoke is released. This attempt to smooth a 3D print released far more than a puff of blue smoke, and was nearly a disaster of insurance adjuster or medical examiner proportions.

Luckily, [Maxloader] and his wife escaped serious injury, and their house came out mostly unscathed. The misadventure started with a 3D printed Mario statue. [Maxloader] had read acetone vapor can smooth a 3D print, and that warming the acetone speeds the process. Fortunately, his wife saw the looming danger and wisely suggested keeping a fire blanket handy, because [Max] decided to speed the process even more by putting a lid on the pot. It’s not clear exactly what happened in the pot – did the trapped acetone vapors burp the lid off and find a path to the cooktop burner? Whatever it was, the results were pretty spectacular and were captured on a security camera. The action starts at 1:13 in the video below. The fire blanket came in handy, buying [Max] a few seconds to open the window and send the whole flaming mess outside. Crisis averted, except for nearly setting the yard on fire.

What are we to learn from [Maxloader]’s nearly epic fail? First, acetone and open flame do not mix. If you want to heat acetone, do it outside and use an electric heat source. Second, a fire extinguisher is standard household equipment. Every house needs at least one, and doubly so when there’s a 3D printer present. And third, it’s best to know your filaments – the dearly departed Mario print was in PLA, which is best smoothed with tetrahydrofuran, not acetone.

Anything else? Feel free to flame away in the comments.

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3D Printed Electric Unicycle

Actually riding around at 30 km/h on a 3D printed means of transportation is pretty gnarly, if not foolhardy. So we were actually pleased when we dug deeper and discovered that [E-Mat]’s unicycle build is actually just a very nice cover and battery holder.

We say “just”, but a 3D-printed design takes a couple of cheap parts (the wheel and pedals) from the Far East and turns them into a very finished-looking finished product. Custom bits like this fulfill the 3D printing dream — nobody’s making it, so you make it yourself. And make it look pro.

It turns out that other people have noticed this motor/controller/pedal combo as well. Here’s some documentation to get you started.

It’s funny. Just four years ago, self-balancing powered unicycles were the realm of the insane hacker. Then came some hacker improvements, and now we’re at the point where you can mail-order all the parts and 3D print yourself a fancy enclosure.

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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]

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

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!

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”

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 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 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 Prize Entry: ForEx Display is A Well Executed Hack

[Stefan] works in a place where knowing the exact state of the foreign-exchange market is important to the money making schemes of the operation. Checking an app or a website was too slow and broke him out of his workflow. OS desktop widgets have more or less departed this earth for the moment. The only solution then, was to build a widget for his actual desk.

The brains of the device is a ESP8266 board, some peripherals and a small backlit TFT display. The device can run off battery or from a wall wart. [Stefan] even added some nice features not typically found in hacks like this, such as a photocell that detects the light level and dims the screen accordingly.

The software uses an interesting approach to get the latest times and timezones. Rather than use a chart or service made for the task, he uses an open weather API to do the task. Pretty clever.

The case is 3D printed and sanded. To get the nice finish shown in the picture [Stefan] spray-painted the case afterwards. All put together the device looks great and gives him the desktop widget he desired.

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