Scratch-Fabricated Plastic Gobbling Shredder Brings Recycling Home

[Jason Knight], an intern at FabLab RUC, has worked hard for 9 months to make a sheet plastics shredder for HDPE and LDPE from things like plastic bags, bubble wrap and air cushion packaging with the goal of recycling the shredded plastic. Why shred these things? When broken down to smaller pieces they can be melted in a consumer grade oven (like where you cook your frozen pizzas) then molded into new objects or extruded into 3D printing filament.

We especially like his big homemade 1.1 inch (30mm) thick wooden gears, for transferring the rotation from the motor to the cutting shafts while giving a step up in torque. As you can see in the video below, the gears definitely add an extra look of power to the machine.

The blades are the shape you most often see in shredders, gear-like disks side-by-side with teeth cut from them that pull the plastic in while shredding it (in contrast to this lower-throughput experimental DIY shredder made with two steel pipes). [Jason’s] multiple teeth are a bit of work to fabricate — not only were all the teeth milled from sheet metal but they then had to be individually sanded to remove burrs from the edges. It was worth it, as this has no problem chewing waste plastics to pieces.

Shredders can be dangerous machines for wandering fingers so [Jason] added a few safety features. Those include a drawer that you open to insert your plastic into the shredding area and a guard that completely surrounds the gears. And both features include transparent plastic areas so that you can still watch the impressive working parts in action.

10 thoughts on “Scratch-Fabricated Plastic Gobbling Shredder Brings Recycling Home

    1. It’s exactly what I need too!
      The entire past two weeks I’ve been mulling over designs for a HDPE shredder, being somewhat underwhelmed with the designs I’ve come across so far. This is the perfect mix of power & size for me.

    1. That leads to an interesting thought. A liquid nitrogen plastic shredder? Make a pass through the liquid nitrogen bath and then between the chompers. :)

      1. There would be a few trade-off to calculate, how cold do you really need to get the plastic to minimise the size and power of the shredder module keeping in mind that the cold also embrittles metals. Perhaps even the tooth design can be different as no gripping or tearing is required. Even a non-contact option such as an industrial ultrasonic transducer is worth considering. I’d start from scratch and assume nothing about the design if I used super-cooling. Then again there is the small issue of the cost to fabricate and run it….

          1. Not very efficient, only used where compressed air is already available in abundance. Ironically the most efficient way to cool waste plastic may be to first heat it enough to compress it into rough ingots, then cool those and grind them down from one end when they are brittle. With a heat pump you would have both a source of heat and cold, as you get with a vortex tube, but thermoacoustic heat engines will give you up to 30% overall efficiency, which is much better, and they are still something a “hacker” can build in a simple workshop.

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