Mini-Molder: Blow Molder Scratch-Built by Single Hacker

 

We caught up with [James Durand] at Maker Faire. He was one of the rare Makers (no mention of selling or future crowd funding) that had a booth at Maker Faire — he was exhibiting a blow molding machine that he built from scratch.

The fabrication process is 100% [James]. Every custom part was designed and milled by him. All of the assembly techniques were his to learn along the way. And we didn’t see anything that isn’t production ready. We’re both impressed and envious.

About three years ago he got the itch to build the mini-molder after learning about the Mold-A-Rama machine — a blow-molding vending machine that was popular a half century ago. A bit of his journey is documented as a molding category on his blog. For the most part it sounds like 1.5 years spent on the CAD design really paid off. He did share one element that required redesign. The initial prototype had a problem with the molds being pushed up when they came together. He tweaked the mechanism to close with a downward motion by flipping the hinge design. This seems to hold everything in place while the drinking fountain chiller and water pump cool the mold and the plastic model within.

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.



		

Retrotechtacular: The 10-year anniversary of plastic

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This footage called Industry on Parade is a unique look back at the golden age of plastics. We also value the footage as a look at America’s manufacturing sector at its height.

We remember a middle-school teacher recalling his father — who was a research scientist working at Dow — bringing home a pair of discs for him to play with. His first ever encounter with plastic. Here we see a snapshot ten years after plastic manufacturing went mainstream. It starts off with a tour of an injection-molding factory. The screenshot seen above is from the second vignette which tours a production line for naval ship models which will be used to train Navy personnel and as props for strategic planning maps. The film wraps up with the production of plastic fabrics starting with raw materials and ending with synthetic bug screen.

Just to prove it’s an authentic blast from the past, hang in there for the last two minutes when you get an anti-communism PSA. Classic.

[Read more...]

Using nichrome wire to repair broken plastic parts

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It’s a real bummer when injection molded plastic parts break. We’ve never found a gluing technique that works for a part which is exposed to force like the clamp on this camera tripod. But [Matthias Wandel] may be on to something. Here he’s using nichrome wire to reinforce the broken plastic part.

The repair process is demonstrated in full in the video after the break. He scavenged the wire from the heating element of broken hair driers. the idea is to wrap the wire across the broken piece, then apply power from a bench supply. This heats the wire, which can then be pulled beneath the surface of the plastic. [Matthias] likens it to using rebar in concrete.

His implementation could be improved just a bit. Getting the wire to embed evenly is a problem, but using a pair of pliers instead of just alligator clips may yield better results.

[Read more...]

Laminated wooden case brings a dropped coffee grinder back from the junk heap

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Instead of giving it up for dead, [Suprise Pink Mist] fabricated a replacement case for the motor and blade of his broken coffee grinder. The original enclosure was made of plastic, which didn’t survive being dropped. There isn’t an image of what those plastic parts looked like, but we have to think they were nowhere near as neat as the replacement.

The first step was to cut a set of plywood discs to the approximate outside dimensions. Since the base of the motor has several different diameters each disc had a void cut out of its center to match. The image to the right shows the motor sitting upside down next to the stacked plywood. The black electrical tape seals around the mason jar ring which was a perfect friction fit with the original bowl of the grinder. Once everything was glued together the outside edges were flattened on a belt sander and the mason jar was screwed in place to house the beans during grinding.

[via Reddit]

Make your own plastic friction welder

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[Fran] shows us how to build a plastic friction welder. It’s a method of connecting plastic pieces. While it’s new to us, apparently this type of tool was given to kids about forty years ago to use with craft project (when plastic was all the craze).

The tip of the friction welder is a styrene rod. If it’s spun fast enough the friction will cause the material to heat to the melting point, depositing a bead of styrene into the joint. The tool seen here is a cheap DC rotary tool acquired from Harbor Freight. It really did a horrible job, but [Fran] discovered that it was the power supply that was under-rated. When she replace the wire that feeds it and used her bench supply it spit out 16,000 rpm without any trouble. The welding rods can be found at the craft store and fit the chuck of the tool quite nicely. You can see her demo in the video after the break. The seam she’s working on comes out very strong, surviving a slew of violent whacks on the workbench.

We’ve seen a few other methods of welding plastic. One used a tool much like a soldering iron, the other depends on ultrasonic waves and clamping pressure.

[Read more...]

Science fair project sorts recyclables

This crew of high schoolers built a sorting robot for the Smart Young Mindz challenge. We got pretty excited when hearing that it sorts plastic by its recycling code, but unfortunately this isn’t quite what it’s made out to be. The device uses an RFID code on each product to figure out where it goes. Their thinking is that at some point every product sold will have an embedded tag in it. For now this will not revolutionize the recycling industry, but the build is still impressive. We’re sure they learned a ton from all of the mechanical engineering that went into the project.

You can see the three laundry baskets that serve as the sorting bins. The white box above the bin on the right is the hopper in which a plastic container is placed. The box can then revolve around a central axis to position itself over the correct basket. The floor of the box is then retracted, dropping the refuse in the bin. Check out the video after the break for the satisfying cry of the servo motors at work.

We like seeing recycling robots, but so far most of what we’ve seen are aluminum can crushers.

[Read more...]

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