Plastic Recycling

Shredder and Extruder Recycling Project

Introduction

During my junior year of high school, I took a class called RidgeWRX. This was a new type of class at my school that taught through experiences rather than in a classroom. Instead of sitting through a standard government or finance class, we attended city council meetings and created project budgets like the one seen above. RidgeWRX met all day, 3 days a week, and gave us the opportunity to explore all sorts of different paths. The problem my group was trying to fix was reducing waste in our tech department. Fossil Ridge High School had a lot of classes that involved learning to 3D print. This leads to a lot of plastic usage, and therefore a lot of plastics being thrown out. Our solution was building a system that broke down these prints before melting them back into 3D printer filament.

Budget

Plastic Recycling Budget

Design

My primary role for this project was creating the CAD model for the plastic shredder. This involved designing the blades, housing, and gears from scratch and generating animations and renders for our proposals and reports. The files were then exported as .dxf's so that all of the parts could be cut out on the plasma cutter.

This was being built for the Fossil Ridge High School Tech Department. One of the teachers, Jesse Oswald, was consulted about proposed designs and potential improvements.

The final design included a housing with two 1/4" faceplates, box tubing along each long edge, with thin sheet metal creating each face. This reduced both weight and size from the original design, which used 1/4" sheets on each side.

The blades consisted of 3 designs, the only difference being a rotation of the hex hole in the middle by 20 degrees. They were arranged along each hex rod so that the cutting faces would travel from the front to the back of the box.

The right hex rod would be driven by a motor, which was stepped down by a 100:1 worm gear box.

Fabrication - Shredder

Here is where I can talk about failure, this project had a lot of it. Rather than letting them stop us, though, we learned! There was a considerable emphasis on recycling for this project, which was in line with the design of a system that gives new life to failed 3D prints. Allow me to walk you through our build process, all of the problems we encountered, and how we decided to solve each one:

These failures began when we decided we wanted to repurpose the motor from a dryer that had been thrown out.

After finally extracting the motor, we came to the conclusion that we would not use the 240V motor. Our shop only had 2 240V sockets, which already had 3 machines fighting to use them.

We then found an old motor that surely hadn't worked for years.

We began taking it apart, but quickly realized none of us had the experience needed to repair it ourselves.

After a few phone calls and a trip to the motor repair shop, we learned that our motor was not able to be repaired. Just another thing to go wrong.

The shop then informed us that they had another motor with very similar dimensions that we promptly bought and wired to the on/off switch we had.

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It works!

During this time, all of the parts we ordered arrived, including this gearbox from China!

It would be a shame if the input shaft didn't measure to what we had ordered... another setback!

We were able to use the CNC mill to make the motor crankshaft fit into the gearbox. Get ready, this is not the only time we needed the CNC.

The next step was to begin cutting the metal for our shredder. This began with learning how to use the plasma cutter.

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We ran a trial cut on our first blade to make sure the sheet metal was positioned correctly.

bladeCut.mp4

And finally, we can turn on the PLASMA!

(wear eye protection, everyone)

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You may have noticed in the video above that our plasma table is nothing more than a handheld plasma cutter bolted to a CNC table. While the cuts we made were far more accurate than anything that could have been done by hand, they were less than ideal for our applications. Here is where we see the return of the CNC mill, which we used to cut down the hex holes to the dimensions we wanted. We also used slag hammers and angle grinders to make sure the blades had smooth faces that would fit together nicely.

For the shredder portion of the project, this is where our involvement stops. We had all of the parts ordered, everything cut out, and were excited to see everything come together. Unfortunately, we would not be coming back to school after March of 2020. The good news is: there was a lot more to this project. I was sent a video from the next year's students who used my design as a guide to fully assemble and troubleshoot the shredder! They were able to finish this part of the project and run it successfully.

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Assembly - Extruder

We were able to admit very early on that no one in our group had the knowledge to assemble something that could heat plastic to up to 200 degrees C and extrude it precisely enough to be reused in a 3D print. At the same time, we did not have the budget to purchase something that was fully assembled. We discovered a company that sold extruder kits that just needed to be put together. Who doesn't love some big kid Legos with augers and heating elements?

With all of our parts accounted for and instructions in hand we began assembling everything.

Front plate with PID

Pipe, auger, and motor all connected

Wiring for heating, motor, and temperature sensors

Almost all assembled! The casing just needs to be bolted shut.

DYOH: Drill Your Own Holes

Incredible! Assembled and running as it should be! For this part of the project, it was a relief to have everything go so smoothly. We followed the instructions very closely and the final product worked as it should.

Presentation - CSU Sustainability Expo

For the final part of this project, we were invited to present at a Sustainability Expo put on by CSU. After completing the extruder and making good progress on the shredder, we wanted our theme to be plastic pollution. Our team grew and we began assembling a diorama that would show how plastic can travel to the ocean. We explained at the expo how much plastic reaches the ocean every year, and how that can be prevented with recycling and reuse, like with the system we were assembling for our school.

We went to a local hardware store to see if we could, yet again, recycle some supplies. We were given piles of cardboard and some plastic wrap that would have been thrown out.

We cut out and layered each sheet of carboard to create the scene we wanted.

The goal was a some small hills and a river, which started in the "city" and ended in the "ocean".

Once we were happy with the shape, we glued the plastic sheet to the cardboard and began painting over it.

While we waited for everything to dry, we took a trip to Hobby Lobby for some model train decorations.

Our river worked! The "ocean" was a small fish tank, which had a pump that brought water back to the top. We had small wooden balls that we used to illustrate plastic travelling in the water.

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Expo night!

It was incredible to see everything we had been working on for the year combined into one presentation. I really enjoyed being able to explain everything we had learned to the people who came by our booth, as well as seeing what else was being done for the environment in Fort Collins. Throughout the whole project I learned a lot about the design process and turning the product into something that can be displayed to other people. It has to be one of the most rewarding things I have been a part of.

Here's a slideshow from the expo:

Project Report

Shredder_ Remastered.pdf

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