My DIY BB-8: Problems, Solutions, Lessons Learned

Imagine trying to make a ball-shaped robot that rolls in any direction but with a head that stays on. When I saw the BB-8 droid doing just that in the first Star Wars: The Force Awakens trailer, it was an interesting engineering challenge that I couldn’t resist. All the details for how I made it would fill a book, so here are the highlights: the problems I ran into, how I solved them and what I learned.

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Tony the Pinball Wizard 3D Prints Full Sized Pinball Machine

[Tony] has designed and 3D printed a full-sized pinball machine and it’s absolutely incredible. And by 3D-printed, we mean 3D-printed! Even the spring for the plunger printed plastic.

The bumper design is particularly interesting. The magic happens with two rings of conductive filament. the bottom one is stationary while the top one is a multi material print with a flexible filament. When the ball runs into the bumper the top filament flexes and the lower rings contact. Awesome. Who wants to copy this over to a joystick or bump sensor for a robot first? Send us a tip!

The whole document can be read as a primer on pinball design. [Tony] starts by describing the history of pinball from the French courts to the modern day. He then works up from the play styles, rules, and common elements to the rationale for his design. It’s fascinating.

Then his guide gets to the technical details. The whole machine was designed in OpenSCAD. It took over 8.5 km of eighty different filaments fed through 1200+ hours of 3D printing time (not including failed prints) to complete. The electronics were hand laid out in a notebook, based around custom boards, parts, and two Arduinos that handle all the solenoids, scoring, and actuators. The theme is based around a favorite bowling alley and other landmarks.

It’s a labor of love for sure, and an inspiring build. You can catch a video of it in operation after the break.

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 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”