Recycling Plastic With Liquid Nitrogen

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Recycling 3D printer filament isn’t a new idea, and in fact there are quite a few devices out there that will take chunks ABS, PLA, or just about any other thermoplastic and turn them into printer filament. The problem comes when someone mentions recycling plastic parts and turning them into filament ready to be used again. Plastics can only be recycled so many times, and there’s also the problem of grinding up your octopodes and companion cubes into something a filament extruder will accept.

The solution, it appears, is to freeze the plastic parts to be recycled before grinding them up. Chopping up plastic parts at room temperature imparts a lot of energy into the plastic before breaking. Freezing the parts to below their brittle transition temperature means the resulting chips will have clean cuts, something much more amenable to the mechanics of filament extruders.

The setup for this experiment consisted of cooling PLA plastic with liquid nitrogen and putting the frozen parts in a cheap, As Seen On TV blender. The resulting chips were smaller than the plastic pellets found in injection molding manufacturing plants, but will feed into the extruder well enough.

Liquid nitrogen might be overkill in this case; the goal is to cool the plastic down below its brittle transition temperature, which for most plastics is about -40° (420° R). Dry ice will do the job just as well, and is also available at most Walmarts.



		

Successful 3D Printed Cranium Implant

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What an age we live in. If the image above looks like the entire top of a skull — it’s because it is. Surgeons successfully replaced a 22 year old woman’s cranium with this plastic copy.

We’ve seen small 3D printed transplants before, but nothing as big as this. A 22 year old woman suffered from a very rare disorder in which her skull never stopped growing. While normal skulls are about 1.5cm thick, hers was almost 5cm thick by the time of the surgery. If they left it any longer, the continued bone growth would have eventually killed her.

Until now this surgery has required a hand-made concrete-like implant to replace the removed bone. As you can imagine, it’s hardly an ideal solution. Thanks to continually advancing 3D printing technology, surgeons at the University of Utrecht UMC were able to create an exact copy in a durable and lightweight clear plastic, which also has a better rate of brain function recovery than the old way of doing it.

The 23 hour surgery took place last December and was a huge success with the patient making a full recovery — if you’re not too squeamish around exposed brains, check out the following video. Wow.

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3D Printering: Custom RC Camera Mount Takes To The Sky

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3D Printers are only good for printing trinkets and doodads, right?  Not really. Although, I do print the occasional useless object, most of my prints are used for projects I’m working on or to meet a need that I have. These needs are the project’s design requirements and I’d like to share the process and techniques I use when creating a functional 3D object.

My pal [Toshi] has RC Airplanes and flies often. I have an Action Camera that I never use. Why not combine the two and have some fun? The only thing standing in our way was a method to mount the camera to the airplane. 3D printing makes it easy. If you have a popular vehicle or application, there may be something already available on a 3D model repository like Thingiverse. Our situation was fairly unique I decided to design and print my own mount.

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The Mostly 3D Printed Violin

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While Thingiverse is filled with Ocarinas, there’s little in the way of printable instruments for more serious musicians. [David Perry] hopes to change this with the F-F-Fiddle, the mostly 3D printed full-size electric violin.

The F-F-Fiddle is an entry for the LulzBot March 3D Printing Challenge to make a functional, 3D printed musical instrument. Already there are a few very, very interesting submissions like this trombone, but [David]‘s project is by far the most mechanically complex; unlike the other wind and percussion instruments found in the contest, there are a log of stresses found in a violin, and printing a smooth, curved fingerboard is quite the challenge.

While there are a few non-printed parts, namely the strings, a drill rod used as a truss rod, some awesome looking tuners, and of course the piezo pickups – the majority of this violin, including the bridge, is 3D printed. It’s an amazing piece of work, and after listening to the video (below), sounds pretty good too.

You can grab all the files on Thingiverse and read up on the build at Openfab PDX.

 

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Who Wouldn’t Want 3D Printed Candles of Yourself on Your 70th Birthday?

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[Christian Lölkes] needed a unique gift for their CEO’s 70th birthday — We mean really, what do you get someone who probably has everything? Well… you 3D scan him and make candles in his likeness of course!

Since they have both a 3D scanner and 3D printer at work, this was the obvious choice. Instead of printing the mold out, they opted to print a high resolution figurine of their CEO, and then make a reusable silicone mold instead. When you’re designing a figurine for candle casting, it’s important to make a nice wide base, as this will make pouring the hot wax into the mold much easier.

There are lots of different ways to make molds, but to make theirs they decided to use a toilet paper roll for convenience. After taping up the mold with the figurine inside, it’s time to fill it with silicone. Unfortunately bubbles form in silicone so you need a way to force the bubbles to rise to the top and pop — vibrating the mold is a good solution, and setting it on top of a washing machine is an easy way to accomplish it.

Once the silicone is cast, you have to cut the mold in half carefully as to not damage your figurine. Then it’s just a matter of zip-tying the mold back together, inserting a wick and pouring wax in! Cool.

3D Printed… Measuring Tape?

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Here’s a new one to push the envelope… How about a 3D printed measuring tape?

This unique 3D printed tool was designed and printed in a single job.  [Angry Monk] has been challenging himself lately with these intricate designs, having recently finished a completely 3D printed set of dial calipers, which is impressive in its own right.

Looking for his latest challenge he pondered what it would take to make this 3D printed tape measure. As he continued to think about it he realized how complex it would actually be to pull off. After designing and printing a few of the basic parts to help him solidify his ideas, he set to work. This tape measure has 114 individual parts. It includes 52″ of tape links with 1″ divisions and markings down to the 1/8th of an inch. It even features a hand crank (sorry no spring return) to roll up the tape.

Now as you can imagine, a complex assembly like this is a bit out of the realm of possibility for regular hobby 3D printers — a UV resin printer might be able to do it, but [Angry Monk] used a commercial Objet Eden 3D printer. Still though — it’s an impressive display of design, check out the following video and see for yourself.

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Soft Robotics, Silicone Rubber, And Amazing Castings

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Most of the robotics projects we see around here are heavy, metallic machines that move with exacting precision with steppers, servos, motors, and electronics. [Matthew] is another breed of roboticist, and created a quadruped robot with no hard moving parts.

[Matthew] calls his creation the Glaucus, after the blue sea slug Glaucus atlanticus. Inside this silicone rubber blob are a series of voids, allowing compressed air to expand the legs, gently inching Glaucus across a table under manual or automatic control.

Even though no one seems to do it, making a few molds for casting on a 3D printer is actually pretty easy. [Matthew] is taking this technique to an extreme, though: First, a mold for the interior pressure bladders are printed, then a positive of this print made in silicone rubber. These silicone molds – four of them, for the left, right, top and bottom – are then filled with wax, and the wax parts reassembled inside the final ‘body’ mold. It’s an amazing amount of work to make just one of these soft robots, but once the molds and masters are made, [Matthew] can pop out a soft robot every few hours or so.

There’s a lot more info on Glaucus over on the official site for the build, and a somewhat simpler ‘compressed air and silicone rubber’ tentacle [Matthew] built showing off the mechanics. Video below.

 

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