Objective:

Design and build a device for extruding 3mm 3D printer filament from recycled ABS pellets and colorant.

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Skills and Tools Used:

• System Design

• Iterative Prototyping

• Design Reuse

• AC Wiring

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Notable Features:

• Single band heater with PID controller

• 12V geared motor with controllable speed

• 5/8" auger as an extrusion screw

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Details:

This was my high school senior capstone project. I had already built a 3D printer, but wanted a way to make my own filament. Filament was more expensive at the time, and the idea of being able to start with pellets to end up with a 3D printed object was something I found especially intriguing.

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With a budget of about $150 and no access to any sort of machine shop, I knew this project was going to be all about designing a system with off-the-shelf hardware and prebuilt modules where possible.

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A 12v windshield wiper motor is coupled to a 5/8" auger drill bit to push plastic pellets down a heated pipe, then through a mesh filter and brass die. Getting everything to flow properly took some careful tuning of the temperature setpoints and motor speed. I had to learn the basics of PID control for this project, but the PID controller with a digital readout made temperature control much easier. 

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Large scale extruders are usually closed loop systems that actively monitor the diameter of the output filament to tune the speed at which the filament is pulled through the die. 

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My design relied solely on temperature and wiper motor speed to control diameter, but in the end I had some usable ABS filament!