Recycling PET Plastic to Filament

This project was developed within the Orange Digital Center Morocco , a space dedicated to fostering innovation, creativity, and rapid prototyping. At the FabLab, individuals and teams have access to state-of-the-art tools, including 3D printers, laser cutters, and a variety of electronic and mechanical resources. The center provides a collaborative environment where innovators, entrepreneurs, and students can transform their ideas into tangible products. By focusing on sustainable and impactful solutions .

One of the biggest problems on the planet is pollution. Most of it is plastic trash, specifically PET plastic bottles. One of the ways to fight this problem is by recycling. A way to reuse PET plastic is by turning it into filament for 3D printing. My project involves fabricating a filament machine that is recycling PET plastic and also helps reduce the cost of 3D printing.

Prepared by Aadil Agoussal.

I started by 3D modeling the design in Fusion 360. I designed all of the 3D-printable components and modeled some of the main bought-out elements to get the general shape and design right. I also laser-cut some parts in plexiglass as a method to reduce the cost of certain parts of the machine.

You can download the CAD Files if you'd like to make your own same Recycling machine.

Note For the next steps : For an esey assembeling process i made sure that most of the part used for assembely are M4 and M5 nuts and bolts .

There is one main 3D-printed part for the cutter, along with a cutter blade that wil be secured with an M4 nut and bolt. Also we need a gearing to ensure a smooth cutting process of the PET bottel.

The nozzle is originally a standard 0.4mm size, but we need to enlarge it to match the filament diameter. Our target is 1.75mm, though the filament tends to expand slightly after leaving the hotend. To accommodate this, we'll use a 1/17" drill bit, which measures just under 1.7mm, to drill out the nozzle.

We can then mount the heat block i nto the holder. I used an M3 screw through a metal part to hold the hot end at the desired height. I secured the metal part to the wood plate with two M4 screws for stability.

This assembly required multiple 3D-printed models (gears and mounts) , along with various laser-cut plexiglass holders for the spool and the stepper motor.

The winder mechanism has interchangeable spools, so we don't need to 3D print a special spool. The interchangeable spool mechanism works by screwing a 3D-printed screw into the middle of the spool to hold it, as shown in the pictures.

To ensure the winder has enough torque to pull the filament, I designed a gear system with a 1:8 ratio using three gears.One with 8 teeth on the stepper motor and two with 32 teeth.I also ensured that the gears can handle the torque by using herringbone gears for two of the main gears, as they are stable and heavy-duty.

There is the CAD Files.

I used a prototype PCB to solder all the electronic components, securing the connections.

I made a circut with arduino nano to control and automate different part of the machinasem and i laser cut a specal box for the electronics and lcd, there is the pins connections :

Arduino Nano (Blue Board):

1. Pin D2: Connected to the DIR (direction) pin of the stepper motor driver.
2. Pin D3: Connected to the STEP (step) pin of the stepper motor driver.
3. Pin A0: Connected to a potentiometer (used to control motor speed or temperature).
4. Pin A2: Connected to the thermistor (for temperature reading).
5. Pin D6: Connected to PWM output (for controlling a heater or fan via the mosfet).
6. Pin D10: Connected to a switch (position1).
7. Pin D11: Connected to a switch (position2).

Stepper Motor Driver (Red Board):

1. DIR Pin: Connected to Arduino D2.
2. STEP Pin: Connected to Arduino D3.
3. Power and Ground Pins: Connected to the power supply and ground rails of the perfboard.

MOSFET Pinout:

1. Gate:
2. Connected to Arduino pin D6 (PWM output).
3. Drain:
4. Connected to the negative terminal of the heater (or the load you're controlling).
5. Source:
6. Connected to GND (ground).

Thermistor:

1. One side: Connected to 5V.
2. Other side: Connected to Arduino A2 via a resistor (probably the 10kΩ series resistor Rb in the circuit).

LCD Display (I2C):

1. SDA Pin: Connected to A4 on Arduino Nano.
2. SCL Pin: Connected to A5 on Arduino Nano.
3. Power: Connected to 5V and GND rails on the board.

Power Connections:

1. Power Supply: It is providing VCC (12V) and GND for the entire circuit by the 12v power supply

Potentiometer:

1. Center pin: Connected to A0 of the Arduino Nano for analog readings.
2. Other pins: Likely connected to 5V and GND.

Heater(PWM controlled):

1. PWM Pin: Connected to the mosfet connected to D6 of the Arduino Nano to modulate power.

The box assembely is strate foward shownd in the picture .I used a gluw to secure the box and some M3 bolts to secure the lcd and for the potonsiometer i printed a nubs for esy control.

the Wiring start with :

1. Slide the thermocontroller into the faceplate.
2. Slide the PWM potentiometer through the faceplate from behind and attach the plastic knob. Use hot glue to secure it to the faceplate if necessary.
3. Push the switch through the remaining opening in the faceplate. 

For the programing part i use to programme the arduino the Arduino IDE softwar .The programme contain:

1. Library Inclusions: It begins by including necessary libraries such as AccelStepper for motor control, Wire for I2C communication, and LiquidCrystal_I2C for managing the LCD display.
2. Pin Definitions: Specific pins are defined for the stepper motor, PWM output, and input buttons, allowing for organized control of hardware components.
3. Variable Initialization: Various variables are initialized to handle user inputs, temperature readings, motor settings, and PID control parameters.
4. Setup Function: In the setup() function, the LCD is initialized, and pin modes are set. The initial display message informs the user about the configuration stage.
5. Loop Function: The loop() function continuously reads inputs, adjusts motor speed or temperature based on user interactions, and updates the display. It also implements the PID control algorithm to maintain the desired temperature by adjusting the PWM output.
6. Thermistor Function: A dedicated function calculates the temperature from the thermistor readings using the Steinhart-Hart equation.
7. Display Update Function: A function to periodically refresh the LCD with the current temperature and motor speed, ensuring that the user has real-time information about the system's status.

Preparing the PET bottel (Heating&cuting):

To prepare a bottle, we first need to remove the label and residue as well as any date markings. I found that acetone works well for this.

The cutter works best with a smooth surface and most bottles are rippled in some way. You can smooth them out over some heat with a drop or two of water inside the bottle to pressurise it slightly - Be very careful not to heat the bottle up too much and wear gloves when opening it up so that the hot steam does not burn you.

Feeding the pet in to the hot-end :

Once the PET bottle is prepared and cut into small pieces, carefully feed the shredded PET into the hot-end of the extrusion system. Make sure the pieces are uniform in size to ensure consistent melting and flow. Gradually introduce the PET to avoid jams, and monitor the feed rate to ensure it aligns with the heating capacity of the hot-end. Use a funnel if necessary to guide the PET into the chamber, and maintain a safe distance to avoid burns from any escaping heat.

Configuring the temperature and speed :

To achieve optimal melting and extrusion of the PET, set the temperature of the hot-end according to the material's specifications—typically around 240°C to 260°C. Use the PID control in your Arduino setup to maintain this temperature accurately. Adjust the setpoint on the interface and monitor the temperature readings closely. The speed at which the PET is fed into the hot-end should be fine-tuned to match the melting rate, ensuring a smooth flow without causing blockages.

Configuring the speed of the Stepper Motor :

The stepper motor’s speed is crucial for controlling the extrusion process. Begin by setting a moderate speed, usually around 50-100 RPM, and adjust based on the desired output rate of the filament. Use the potentiometer to fine-tune the motor speed in real-time while observing the extrusion consistency. Ensure that the motor speed matches the melting and feeding rates of the PET to avoid over-extrusion or under-extrusion, which can affect the quality of the filament produced. Regularly check the system for any signs of strain or blockage during operation.

PRINT SETTINGS:(1.0mm Nozzle)

Layer Height .3mm

Wall Thickness .8mm

Nozzle Temperature 260°c

Build Plate Temperature 85°c

Standby Temperature 150°c

Retraction Distance 4.5mm

Retraction Speed 40mm/s

Flow 130%

Initial Layer Flow 140%

Print Speed 50mm

Brim Width 10mm