Vicious Little Desktop Shredder Pulverizes Plastic Waste

We’ve all likely seen video of the enormous industrial shredders that eat engine blocks for lunch and spit out a stream of fine metal chips. The raw power of these metal-munching monsters is truly fearsome, and they appear to be the inspiration for SHREDII, the miniature plastic shredder for at-home recycling of plastic waste.

The fact that SHREDII isn’t all that large doesn’t make it any less dangerous, at least to things smaller and softer than engine blocks, like say fingers. The core of the shredder is a hexagonal axle carrying multiple laser-cut, sheet steel blades. The rotating blades are spaced out along the axle so they nest between a bed of stationary blades; rotating the common axle produces the shearing and cutting action needed to shred plastic.

On version one of the shredder, each blade had two hooked teeth, and the whole cutting head was made from relatively thick steel. When driven by a NEMA 34 stepper — an admittedly odd choice but it’s what they could get quickly — through a 50:1 planetary gearbox, the shredder certainly did the business. The shreds were a little too chunky, though, so version two used thinner steel for the blades and gave the rotary blades more teeth. The difference was substantial — much finer shreds that were suitable for INJEKTO, their homebrew direct-feed injection molding machine.

There’s a lot to be said for closing the loop on plastics used in desktop manufacturing processes, and the team of SHREDII and INJEKTO stands to help the home gamer effectively reuse plastic waste. And while that’s all to the good, let’s face it — the oddly satisfying experience of watching a shredder like this chew through plastic like it isn’t even there is plenty of reason to build something like this.

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Recycling Plastic Into Filament

Plastic is a remarkable material in many ways. Cheap, durable, and versatile, it is responsible for a large percentage of the modern world we live in. As we all know, though, it’s not without its downsides. Its persistence in the environment is quite troubling, so any opportunity we can take to reduce its use is welcome. This 3D printed machine, although made out of plastic, is made out of repurposed water bottles that have been turned into the filament for the 3D printer.

While there’s not too much information available on the site, what we gather is that the machine cuts a specific type of plastic water bottle made out of PET plastic into strips, and then feeds the strips into a heated forming tool. The tool transforms the strips into the filament shape and spools them so they are ready to feed back into a 3D printer. As a proof of concept, it seems as though this machine was made from repurposed plastic, but it could also be made using whatever filament you happen to have on hand.

As far as recycling goes, this is a great effort to keep at least some of it out of landfills and oceans. Unfortunately, plastic can’t be recycled endlessly like metal, as it will eventually break down. But something like this could additionally save on some filament costs for those with access to these types of bottles. Other options for creating your own filament also include old VHS tapes, but you will likely need a separate machine for that.

Stresses Revealed With A Polariscope

There are a lot of ways that stresses can show up, at least when discussing materials science. Cracks in concrete are a common enough example, but any catastrophic failure in a material is often attributable to some stress that couldn’t be withstood. If you’re interested in viewing those stresses before they result in damage to the underlying material, take a look at this DIY polariscope which can view internal stresses in glass and other clear objects.

The polariscope takes its name from the fact that it uses polarized light to view the internal structure of a transparent object such as glass. When the polarized light passes through glass in a certain way, the stresses show up as lighter areas thanks to the stressed glass bending the light back into view. This one is constructed with a polarizing filter placed in front of an LCD screen set to display a completely white image. When glass is placed between the screen and the filter no light is seen through the polariscope unless there are stresses in the glass. Even placing a force on an otherwise un-stressed glass tube can show this effect, and [Advanced Tinkering], this project’s creator, has several other creations which show this effect in striking detail.

The effect can also be observed as colored areas in other plastic materials as well. It’s an interesting tool which can help anyone who frequently works with glass, but it’s also interesting on its own to see clues left behind from the manufacturing process of various household items. We’ve seen some other investigative methods for determining how other household items are mass produced as well, like this project which breaks down the injection molding process.

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Great Computer Hacks Make Hackers Hacker Computers

In the year 1995, computers were, well… boring. The future wasn’t here yet, and computers were drab, chunky beige boxes. Sure, there were some cool-ish computers being sold, but the landscape was still relatively barren. But as you’ll see in the video below the break, it doesn’t have to be that way, and the [Hackers Curator] shows us the way by recreating Johnny Lee Miller’s computer from the 1995 movie Hackers.

Hackers wasn’t popular when it came out, but over the years it has gained quite a following. It portrayed computers and the people who loved them in completely new ways, representing a culture that has never existed. Even so, it inspired so many young hacker types. Among those inspired is the crew over at [Hackers Curator] and they have taken it upon themselves to, uh… curate… the props, costumes, and stories surrounding the movie.

Recreating Dade’s iconic camo “luggable” computer came with quite a lot of difficulty. It turns out that the original movie props were working custom computers that used hacked together customized cases and Mac Powerbook 180c internals. Dade’s (aka Zer0 Cool and Crash Override) was mashup of the a Compaq Portable 486c and the aforementioned Mac. [HackersCurator] have lovingly recreated this prop from two broken computers, but chose to run the internals with a Raspberry Pi.

The techniques used in the creation of this beastly cyberdeck are ones that can be used in building so many other projects, even if you’re not a Hackers hacker. Customizing the plastics and placing a trackball in the most awkward of spots was expertly done, and we’ll be referring to it in the future for guidance when doing similar projects.

Are movie replica hacks your thing? You’re in luck! It turns out that this isn’t [Hackers Curator]’s first build. In 2019 they tackled Lord Nikon’s laptop, and of course, we covered that one too!

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DIY Injection Molder Built From A Cheap Pneumatic Press

[Kurt Schaefer] was watching YouTube videos of people making molds for injection molding purposes using what he considered to be the toy 3018 CNC machines, and looking at the results, decided he needed a piece of the action. However, once you have molds, the next obvious issue to address is lack of access to an injection molding machine. But these things are expensive. As luck would have it, you can get a nice-looking pneumatic press for less than $350, and with a little more money spent, [Kurt] found he could convert it into a functional injection molding machine (video, embedded below), and get some half-decent results out of it.

After ordering the press on eBay, what eventually arrived was quite a mess, having clearly been inadequately packed for its weight, and had sustained some damage in transit. Despite this, it seemed the functional bits were fine, so [Kurt] decided to press on with the build. The first obvious change is the requirement of a heated chamber to deal with the feedstock material. Using an off-the-shelf injection molding chamber by buster beagle 3D, only a few standoffs and a support bracket needed machining in order to complete the mechanics. A common PID controller available from the usual suppliers, with some heat bands wrapped around the chamber, dealt with the injection temperature requirements, and some 3D printed enclosures wrapped it all up neatly.

After some initial wobbles, and a couple of hacks to the design, [Kurt] got some pretty good results out of this simple setup, and it appears to be pretty tune-able and repeatable, which will help maintain the quality of those results. In short, a neat hack of easy to get parts, and perhaps a welcome addition to a hackerspace near you?

3D printed parts are available on the Thingiverse page, as well as a Fusion360 CAD model. The shopping list for parts can be found in the video description, if you want to have a go at reproducing this.

We’ve seen a few DIY injection molding attempts over the years, like this slick plastic molding setup. Here’s one with 3D-printed molds, and if you just need something the right shape, you could just injection mold with a hot glue.

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Retrotechtacular: Understanding The Strength Of Structural Shapes

Strength. Rigidity. Dependability. The ability to bear weight without buckling. These are all things that we look for when we build a mechanical structure. And in today’s Retrotechtacular we take a closer look at the answer to a question: “What’s in A Shape?”

As it turns out, quite a lot. In a wonderful film by the prolific Jam Handy Organization in the 1940’s, we take a scientific look at how shape affects the load bearing capacity of a beam. A single sided piece of metal, angle iron, C-channel, and boxed tubing all made of the same thickness metal are compared to see not just just how much load they can take, but also how they fail.

The concepts are then given practical application in things that we still deal with on a daily basis: Bridges, cars, aircraft, and buildings. Aircraft spars, bridge beams, car frames, and building girders all benefit from the engineering discussed in this time capsule of film.

None of the concepts in this video are suddenly out of date, because while our understanding of engineering has certainly progressed since this film was made, these basic concepts remain the same. As such, they will apply to any structural or mechanical devices that we make, be it 3d printed, CNC routed, welded, glued, vacuum formed, zip tied, duct taped, bailing wired, or hot glued.

Keep your eyes open for a wonderful sights and sounds of a rare Boeing 314 Clipper landing on water and a 1920’s Buffalo Springfield Steam Roller demonstrating how wonderful the film’s sponsor, Chevrolet, makes their automobile frames.

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The Wanhao Duplicator CNC Heat Sealer

One custom, compliant heat exchanger, coming right up!

[Thane Hunt] needed to find a way to make a variety of different heat-seal patterns on a fluid heat exchanger made from polyolefin film, and didn’t want all the lead time and expense of a traditional sealing press machined from a steel plate. Pattern prototyping meant that the usual approach would not allow sufficient iteration speed and decided to take a CNC approach. Now, who can think of a common tool, capable of positioning in the X-Y plane, with a drivable Z axis and a controlled heat source? Of course, nowadays the answer is the common-or-garden FDM 3D printer. As luck would have it, [Thane] had an older machine to experiment with, so with a little bit of nozzle sanding, and a sheet of rubber on the bed, it was good to go!

Custom seal path made in Onshape

Now, heat sealing is usually done in a heated press, with a former tool, which holds the material in place and gives a flat, even seal. Obviously this CNC approach isn’t going to achieve perfect results, but for proof-of-concept, it is just fine. A sacrificial nozzle was located (but as [Thane] admits, a length of M6 would do, in a pinch) and sanded flat, and parallel to the bed, to give a 3mm diameter contact patch. A silicone rubber sheet was placed on the bed, and the polyolefin film on top. The silicone helped to hold the bottom sheet in place, and gives some Z-axis compliancy to prevent overloading the motor driver. Ideally, the printer would have been modified further to move this compliancy into the Z axis or the effector end, but that was more work. With some clever 3D modelling, Cura was manipulated to generate the desired g-code (a series of Z axis plunges along a path) and a custom heated indenter was born!

This isn’t the first such use of a 3D printer we’ve seen, here’s an earlier failure, and like everything, there’s more than one way to do it – here’s a method of making inflatable bladders with a defocused CO2 laser.

(warning! Two minutes of a 3D printer head-banging into the bed!)

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