Plastic Shredder & Extruder System
May 20th 2021
The Goal
To eliminate plastic filament for rapid prototyping by extruding recycled plastic directly onto the prototyping surface.
Meet the Capstone team
The systems
The Shredder
The system is inspired by the Precious plastic system. It shreds the plastic waste by passing through the hopper to the rotating blades. The plastic continuously rotates through the blades until it is the desired size via the mesh at the bottom of the blades.
The Transport System
The system transports all the pellets from the shredder to the extruder, using a rotating auger moving at a constant speed
The Extruder
The system is inpired by rapid manufacturing systems. It transports the plastic downward along with the teeth of a screw while melting the plastic at around 250°C with the external heating elements. The extruded plastic passes through the nozzle of 1mm.
Design Features
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The shredder blades are aligned in a scattered orientation in order to shred the recycled plastic more efficiently and meet the pellet size criteria of 4mm.
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The hopper above the shredder includes a plunger in the design in order to help the user properly feed the plastic into the shredder in a safe and efficient manner.
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Inspired by a traditional agricultural system, the transport system uses an auger screw to move the pellets from the shredder to the extruder system at a constant speed.
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The auger screw is rotated using a NEMA 17 stepper motor and a herringbone gear design, with a gear ratio of 1:3. The auger screw is in a barrel annd transports the pellets downward to the nozzle and if heated by the external heating elements.
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Similar to a 3D printer, there are three external heating elements that heat the barrel and auger screw and thus, the plastic pellets.
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