The Filament Pelletizer For Fused Granular Fabrication

The ABS and PLA that goes into your 3D printer is sold in two forms. The first, naturally, is filament. The second is plastic granules, the raw material for your filament, and costs an order of magnitude less than the filament itself. For years we’ve been seeing machines that either print directly with plastic granules or are converted into filament with fancy filament-extruding machines. Now we can do it the other way. [Aubrey Woern] and [Joshua Pearce] of Michigan Tech have been working on a polymer pelletizer chopper that takes plastic filament and turns it into pellets.

The system uses a large corded drill motor to drive a Forstner drill bit. Filament is then threaded into the top of this spinning drill bit with the help of a small DC motor and grippy wheel printed out of Ninjaflex. The system works, and the authors of the paper were able to vary the size of the chopped filament by feeding it into the Forstner bit faster or slower.

While turning an expensive product (filament) back into its raw material (pellets) may not seem like a great idea, there have been a significant number of advancements in the state of manufacturing filament on a desktop and printing directly from pellets in recent years. A machine that turns plastic back into its raw state is something that’s needed if you want to experiment with plastic recycling, and this machine is more than capable of chopping up a spool of filament in two hours or so.

3D Printer Warning: Heating Plastic To High Temps is Not Healthy

If you’ve ever tried to cut a piece of acrylic with a tool designed to cut wood or metal, you know that the plastic doesn’t cut in the same way that either of the other materials would. It melts at the cutting location, often gumming up the tool but always releasing a terrible smell that will encourage anyone who has tried this to get the proper plastic cutting tools instead of taking shortcuts. Other tools that heat up plastic also have this problem, as Gizmodo reported recently, and it turns out that the plastic particles aren’t just smelly, they’re toxic.

The report released recently in Aerosol Science and Technology (first part and second part) focuses on 3D printers which heat plastic of some form or other in order to make it malleable and form to the specifications of the print. Similar to cutting plastic with the wrong tool, this releases vaporized plastic particles into the air which are incredibly small and can cause health issues when inhaled. They are too small to be seen, and can enter the bloodstream through the lungs. The study found 200 different compounds that were emitted by the printers, some of which are known to be harmful, including several carcinogens. The worst of the emissions seem to be released when the prints are first initiated, but they are continuously released throuhgout the print session as well.

Perhaps it’s not surprising that aerosolized plastic is harmful to breathe, but the sheer magnitude of particles detected in this study is worth taking note of. If you don’t already, it might be good to run your 3D printer in the garage or at least in a room that isn’t used as living space. If that’s not possible, you might want to look at other options to keep your work area safe.

Thanks to [Michael] for the tip!

Living Hinges at the Next Level

First of all, a living hinge is not a biological entity nor does it move on its own. Think of the top of a Tic Tac container where the lid and the cover are a single piece, and the thin plastic holding them together flexes to allow you to reach the candies disguised as mints. [Xiaoyu “Rayne” Zheng] at Virginia Tech designed a method of multimaterial programmable additive manufacturing which is fancy-ese for printing with more than one type of material.

The process works under the premise of printing a 3D latticework, similar to the “FILL” function of a consumer printer. Each segment of material is determined by the software and mixed on the spot by the printer and cured before moving onto the next segment. Like building a bridge one beam at a time, if that bridge were meant for tardigrades and many beams were fabricated each minute. Mixing up each segment as needed means that a different recipe results in a different rigidity, so it is possible to make a robotic leg with stiff “bones” and flexible “joints.”

We love printing in different materials, even if it is only one medium at a time. Printing in metal is useful and could be consumer level soon, but you can print in chocolate right now.

Via Phys.org. Thank you again for the tip, [Qes].

PLA: The Plastic That Grows

If you’ve ever taken a coast-to-coast car trip across the United States, the one thing that’s sure to impress you is the mind-bogglingly immense amount of corn that we grow here. If you take the northern route — I’ve done it seven times, so I know it by heart — you’ll see almost nothing but corn from Ohio to Montana. The size of the fields is simply staggering, and you’re left wondering, “Do we really eat all this corn?”

The simple answer is no, we don’t. We grow way more corn than we can eat or, once turned into alcohol, drink. We do feed a lot to animals, many of which subsequently end up as burgers or pork chops. But even after all that, and after accounting for exports, we still have a heck of a lot of corn to put to work. There are lots of industrial uses for this surplus corn, though, and chances are pretty good you’ve got an ear or two worth coiled up next to your 3D-printer, in the form of polylactic acid, or PLA.

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Spot Welding …Plastic?

Plastic milk bottles, when your project or prototype needs an urgent source of plastic, they are often the first thing to hand. Convenient and flexible, but strong at the same time and usually free, they’re the ultimate source of material in a pinch. However, when it comes to actually manipulating the HDPE plastic they’re made from, there’s often a challenge. It’s easy to cut, but not so easy to join. Conventional glues can have a hard time, making it difficult to bond.

Enter [zimitt], and a spot welding solution for joining HDPE with ease. Ok, so ‘spot welding’ might be a little optimistic given the speed of this process, but it’s useful nonetheless. To heat the plastic, a cheap soldering iron is recommended. A low wattage, straight-to-the-wall one does well, especially as they commonly have the washer-style end shown in the picture. To protect the plastic from burning, a BBQ mat is used – they’re temperature resistant and usually made with a PTFE surface.

First, place the two sheets of plastic face to face and sandwich top and bottom with the BBQ mat. Apply some heat to the mat with the soldering iron then, after a few seconds, remove the iron and provide pressure with a flat object to bond the plastic. [zimitt] used an espresso tamper for this which was ideal.

The results are impressive, and [zimitt] experiments with different plastics as well. Of course, you should exercise caution when attempting anything like this, given the health risks present when heating up different types of plastic.

HDPE is easy to recycle at home, and we’ve seen a lot of great uses: a plastic joiner’s mallet, plastic tiles, and even a filament extruder for 3D printing.

Slipcasting Resin Prototypes

[Eric Strebel] doesn’t need an introduction anymore. If there is a picture of an elegantly designed part with a professional finish on our pages, there is a good chance he has a hand in it. This time he is sharing his method of making a part which looks like it is blow-molded but it is not. Blow-molded parts have a distinctive look, especially made with a transparent material and [Eric’s] method certainly passes for it. This could upgrade your prototyping game if you need a few custom parts that look like solidified soap bubbles.

Mold making is not covered in this video, which can also be seen below the break, but we can help you out with a tip or two. For demonstration’s sake, we see the creation of a medical part which has some irregular surfaces. Resin is mixed and degassed then rolled around inside the mold. Then, the big reveal, resin is allowed to drain from the mold. Repeat to achieve the desired thickness.

This is a technique adapted from ceramics called slipcasting. For the curious, an elegant ceramic slipcasting video demonstration can be seen below as well. For an added finishing touch, watch how a laquer logo is applied to the finished part; a touch that will move the look of your build beyond that of a slapdash prototype.

More education from this prolific maker can be seen in his video on painting with a professional-looking finish and his tips for working with foam-core.

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The Metabolizer Turns Trash into Treasure

The amount of stuff we humans throw away is too damn high, and a bunch of it harms the ecosystem. But what are you gonna do? [Sam Smith] thinks we can do better than shoving most of it in a landfill and waiting for it to break down. That’s why he’s building The Metabolizer. It’s a series of systems designed to turn household trash (including plastic!) into useful things like fuel, building materials, and 3D prints.

The idea is to mimic the metabolism of a living organism and design something that can break down garbage into both useful stuff and fuel for itself. [Sam] is confident that since humans figured out how to make plastic, we can figure out a system to metabolize it. His proof-of-concept plan is to break down waste into combustible, gaseous fuel and use that fuel to power a small engine. The engine will power an open-source plastic shredder and turn a generator that powers an open-source plastic pellet printer like the SeeMeCNC Part Daddy.

Shredding plastic for use as a biomass requires condensing out the tar and hydrocarbons. This process leaves carbon monoxide and hydrogen syngas, which is perfect for running a Briggs & Stratton from Craigslist that’s been modified to run on gaseous fuel. Condensation is a nasty process that we don’t advise trying unless you know what you’re doing. Be careful, [Sam], because we’re excited to watch this one progress. You can watch it chew up some plastic after the break.

If [Sam] ever runs out of garbage to feed The Metabolizer, maybe he could build a fleet of trash-collecting robots.

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