Repairing A Home Injection Molding Machine

When [Michael] over at the Teaching Tech YouTube channel bought a hobby injection molding machine a long time ago, one of the plans he had with it was to use it for grinding up waste bits of PLA filament for injection molding. Since the machine was bought from a US shop and [Michael] is based in Australia it required some modifications to adapt it to the local 220+ VAC mains, followed by adding a PID temperature controller and a small compressor to provide the compressed air rather than from a large shop compressor.

Although [Michael] had discussed using the machine for PLA with the seller to confirm that this would work, a user error meant that the now defective unit had been sitting idly for many years, until recently.

Since the machine had been gathering dust and rust in the garage, fixing the machine up took a complete teardown to remove corrosion and resolve other issues. After this the original fault was identified, which turned out to be a shorted wire near the heater which had been turned up to a too high temperature, leading to the release of magic smoke and banishment of the machine to the Pit of Despair, AKA the shadowy depths of one’s garage.

In this first installment, [Michael] cleaned up the machine and restored it to a working state. In the next part injection molding will be attempted again, which should give some idea of the feasibility of turning scraps of PLA and failed 3D prints into smooth injection molded parts, assuming you have the CNC machine or patience to carve out the requisite molds, of course.

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Arctos Robotics: Build A Robot Arm Out Of 3D Printer Spares?

ARCTOS is a 6-DOF robot arm based upon 3D printed mechanics running a modified version of GRBL firmware. Let’s get this straight now, the firmware is open source, but the hardware plans are a paid download, but for less than forty euros, we reckon the investment would be well worth it, judging from the quality of the build instructions and the software support already in place. Continue reading “Arctos Robotics: Build A Robot Arm Out Of 3D Printer Spares?”

DIY Self-Assembling 4D Printing

A 4D printed object is like a 3D printed object, but it changes shape or self-assembles when its environment changes. [Teaching Tech] has been reading about this technology and decided to try to replicate it using his conventional 3D printer.

His attempts to make a joint that changes when submerged in the water looked at several options: material that can absorb water, material that expands with temperature, and — the selected option — a dissolvable locking mechanism. Essentially, a hinge is held open by a water-soluble lock. When water dissolves the lock, the hinge can spring to its natural position.

Like most experiments, this one had a few false starts. But you always learn something each time. The final design had a TPU hinge and spring with PLA structural beams. The TPU required flat printing, so various pieces have to be rotatable so they can be placed in their final orientation after printing.

Usually, multi-material setups are for printing different colors of the same kind of plastic, it’s possible to use different plastics, but it can be tricky. As a compromise, [Teaching Tech] did one print using PLA and TPU, but printed the PVA locks in a separate pass and installed them on the print at the end. The first finished 4D print wasn’t entirely successful. The hot water slowly dissolved the PVA, but it also deformed the PLA. A redesign of the lock made a big difference.

We aren’t sure this is practical yet, but we are sure someone has a need for this technique and it could be made very practical with a little work. The last time we saw 4D printing, there were magnets involved. We think this is an exciting time where people aren’t just trying to get conventional printing to work well, but are pushing the envelope with new techniques like conical slicing, for example.

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3D Printed Strain-Wave Gearbox Turns Up The Torque

3D printers are good for a lot of things, but making parts for power transmission doesn’t seem to be one of them. Oh sure, some light-duty gears and timing belt sprockets will work just fine when printed, but oftentimes squooshed plastic parts are just too compliant for serious power transmission use.

But that’s not a hard and fast rule. In fact, this 3D-printed strain-wave transmission relies on the flexibility of printed parts to work its torque amplification magic. In case you haven’t been briefed, strain-wave gearing uses a flexible externally toothed spline nested inside an internally toothed stationary gear. Inside the flexible spline is a wave generator, which is just a symmetrical cam that deforms the spline so that it engages with the outside gear. The result is a high ratio gear train that really beefs up the torque applied to the wave generator.

It took a couple of prototypes for [Brian Bocken] to dial in his version of the strain-wave drive. The PLA he used for the flexible spline worked, but wasn’t going to be good for the long haul. A second version using TPU proved better, but improvements to the motor mount were needed. The final version proved to pack a punch in the torque department, enough to move a car. Check it out in the video below.

Strain-wave gears have a lot of applications, especially in robotic arms and legs — very compact versions with the motor built right in would be great here. If you’re having trouble visualizing how they work, maybe a Lego version will clear things up.

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Hackaday Links: April 3, 2022

It’s that time of year again — the 2022 Hackaday Prize has officially launched, and we’re excited to see what it turns out. This year’s theme is “Sustainability, Resilience, and Circularity,” and just in time, too; if the last couple of years has taught us anything, it’s that we’ve got a lot of failure points built into the systems that run our world. As broken as things are, it’s tempting to just curl up in a ball and pretend everything’s fine, but that’s not how hackers respond to adversity. We need to control what we can control, and there’s plenty of work to be done. From sustainable energy ideas to ways to reduce the amount of stuff we throw away, from breathing new life into old equipment to building communities that can take care of themselves, there’s plenty of work to be done. So get over to the Hackaday Prize page, check out the launch summit video if you need some inspiration, and get hacking. And hurry up — things are only going to get better if people like us make it happen.

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Machine Extrudes Filament

We’ve seen a lot of homebrew filament extruders, but [Stefan] at CNC Kitchen shows off a commercial desktop filament extruder in his latest video, which you can see below. The 3DEVO extruder is pretty slick but at around $7,000-$8,000 we probably won’t rush out and buy one. We might, though, get some ideas from it for our next attempt to build something similar.

In concept, any machine that creates filament is pretty straightforward. Melt pellets and push them out of a nozzle. Cool the filament and wind it up. Easy, right? But, of course, the problems are all in the details. Die swell, for example, means you can’t just assume the nozzle’s hole size will give you the right size filament. Continue reading “Machine Extrudes Filament”

3D Printing A Centrifugal Water Pump

Once upon a time, 3D printing was about churning out tiny Yodas and Pikachus, but these days, useful things are regularly 3D printed too. A great example is this centrifugal water pump that can really deliver the juice, courtesy of  [Connor].

The pump’s housings and impeller are all 3D printed in PLA, as well as the inlet which is designed for a 2L soda bottle to screw into. Gaskets are printed in pliable TPU to help seal the housings. There are a few ball bearings inside to allow the impeller to spin nicely, too, with hex head fasteners used to hold everything together and a long bolt used as the main impeller shaft. Notably, no shaft seal is included, so the pump does leak a bit, but it’s not a major concern assuming you’re just pumping water and don’t mind spilling a bit of excess. Turned with a drill at 1800 rpm, the pump is able to achieve a flow rate of 13 litres per minute, or a maximum head of 1.2 meters. The design is on Onshape, for the curious.

It’s a great example of how 3D printing can allow the creation of machines with complex geometry without the need for advanced machining skills. Instead, all the hard work is done on the CAD side of things. We’ve seen 3D printed pumps put to real work before, too, like this fertilizer dispenser. Video after the break.

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