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Plastic crusher - Pellet extruder for MK3S — zdjęcie 1

Plastic crusher - Pellet extruder for MK3S

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Make3D Company Limited

Make3D Company Limited

@Make3D

This prototype extruder is designed as a simple pellet extruder for the Original Prusa MK3S printer.

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Prusa Parts & Upgrades
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Plastic Crusher - experimental pellet extruder designed for Original Prusa i3 MK3S 3D printer

Author of the design: Silvestr Tkáč, Make3D Company Limited

This prototype extruder is designed as a simple pellet extruder for the Original Prusa MK3S printer. The goal was to minimize the number of custom made parts in order to make this technology accessible to common users who wish to experiment with pellet extrusion and especially to test the workflow of plastic recycling.

The development of this experimental extruder was possible due to funding from Royal Academy of Engineering Alumni Grant 2022/2023.

Many thanks to PrusaLab team (www.prusalab.cz) for technical consultations and troubleshooting guidance.

At the moment the extruder is able to print simple coarse objects and requires further development especially when it comes to software.

This workflow is for experienced users only. You can easily irreversibly damage your printer or cause other damage or harm. Proceed with caution. This extruder is not a final product yet, do not expect a continuous extrusion without problems. Make3D Company Limited is not responsible for any damages caused by using this product.

Version: 1.0 (November 2022)

Project to-do list:

  • To conduct testing on multiple printers
  • Improve the extrusion quality tweaking the software settings
  • Compile a custom firmware to improve the extruder performance, allow calibration, mesh bed leveling and enhance user experience when using the slicer.
  • Create a workflow for products printable on this extruder
  • Link to the local plastic waste treatment facilities to provide the pellets from waste plastic or developing affordable grinder.
  • Getting proper feedback from the users and community
  • Scaling up 
  • Automatic pellet refilling system

Material needed to assemble the extruder

3D printable parts that are printed with PETG (3 perimeters 15% infill, 0.2 mm layer height). For our project we used Prusament Recycled PETG (https://www.prusa3d.com/product/prusament-petg-recycled-2kg/) 

  • X carriage front
  • X carriage rear
  • Stepper holder
  • Funnel
  • PINDA holder
  • Print fan holder
  • 2x Z axis holders (L and R)
  • Stepper fan shroud
  • Bearing attachment ring
  • Distributor
  • Distributor holder
  • Z axis top holders

3D printable parts that are printed with PA11 Carbon Fiber or Polycarbonate Carbon Fiber (3 perimeters, 15% infill, 0.2 mm layer height). For our project we used Prusament PA11 Carbon Fiber (https://www.prusa3d.com/product/prusament-pa11-carbon-fiber-black-800g/ or https://www.prusa3d.com/product/prusament-pc-blend-carbon-fiber-black-800g-2/)  

  • Chamber front
  • Chamber rear
  • Hotend holder
  • Fan holder - fan side
  • Fan holder - PINDA side
  • Fan holder - rear
  • Fan shroud

Purchased parts:

Optional distributor to improve flow of pellets to the feeder:

Custom made parts

  • Aluminum heater block, 1pc (see the drawing)

Bolts and nuts

  • M3x60, 3 pcs
  • M3x55, 2 pcs
  • M3x35, 2 pcs
  • M3x30, 1 pc
  • M3x25, 3 pcs
  • M3x20, 4 pcs
  • M3x18, 3 pcs
  • M3x16, 4 pcs
  • M3x15, 2 pcs
  • M3x10, 10 pcs
  • M3x8, 4 pcs
  • About 35 pcs of M3 hex nuts, some of them self-tightening
  • About 15 pcs of M3 square nuts

Instructions for assembling

  • X carriage assembling
    • Insert the nuts into the holes. Do not forget the top hex nut.
    • Using M3x25 bolts attach the rear chamber to the front carriage and tighten carefully
    • Attach the front carrier to the linear bearings on the x axis rods so the bearings will fit into the grooves
    • Make sure the x axis stepper motor is loose before attaching the belt.
    • Insert both ends of the belt into the toothed grooves and tighten using the stepper tensioning mechanism.
    • Attach the rear part of the X carriage and secure it with one M3x20 bolt on the top.
    • Attach the stepper holder and fasten it with the M3x30 bolt.
    • Insert  two hex nuts in the hotend holder and attach it to the front of the X carriage
    • Insert two M3x35 bolts through the stepper holder, x carriage and hotend holder and tighten them. Ensure that the X carriage is sliding freely on the smooth rods. Try releasing the bolts if there is too much pressure.
  • Hotend assembling
    • Before you begin assembling, file the hotend chamber flat on the back side of third rib and make a hole for the bolt from the left. These grooves are created to prevent rotation of the hotend while extruding.
  • Make the tip of the screw.
  • Insert the hotend chamber to the heater block, align the bottom edge. 
  • Insert the thermistor and fix it carefully in place with M2 screw
  • Tighten the heater block with M3 screw
  • Insert the heater cartridge and fix it in place using the M3 screw
  • File the screw to create a flat face on the side
  • Attach the GT2 60T pulley on the screw - tighten the grub screw against the flat filed surface
  • Insert screw into the chamber
  • Pellet chamber completion
    • Insert the hotend to the grooves so the flat filed section faces back.
  • Insert the front part of the chamber and tighten with two M3x55 screws.
  • Put the belt over the pulley
  • Insert 4 hex nuts into the prepared holes in the chamber parts
  • Insert the self tightening nut to the top cover part and fix with one M3x20 bolt. Do not tighten completely, just enough to hold the nut.
  • Attach the bearing adapter on the pulley and insert the bearing
  • Attach the top cover to the chamber and tighten it using four M3x16 bolts.
  • Check if the pulley rotates freely.
  • Attaching the stepper motor
    • Attach the Noctua fan to the stepper holder using an M3x10 bolt
    • Place the stepper motor into the stepper holder. The motor cable needs to face back. Attach the motor to the stepper holder using four M3x10 bolts, but do not tighten them fully yet
    • Prepare two tensioning bolts M3x18, thread the square nuts on them.
    • Attach the GT16 pulley to the stepper rod and tighten the grub screw
      against the flat part of the motor.
    • Gently put the belt over the pulley
    • Use two tensioning bolts M3x18 to achieve the required belt tension.
  • Tighten well the four M3x10 bolts holding the stepper motor.
  • Attaching the print fan
    • Carefully insert the print fan into the fan shroud and secure it with one M3x25 bolt.
    • Attach the print fan holder to the front chamber with one M3x15 bolt
    • Insert the fan with the shroud into the fan holder and secure it with the bolt.
  • Adding the side covers, hotend fan and PINDA
    • Attach the hotend fan to the left side using two bottom M3x20 bolts.
    • Attach the PINDA holder to the right side using two bolts: M3x10 and M3x20. Do not tighten the longer bolt fully yet. We will need to calibrate the distance of PINDA probe from the print bed surface.
    • Insert the M3x15 bolt  in the right side cover, preventing the hotend from rotating. Do not tighten fully, just halfway.
    • Insert the PINDA probe to the PINDA holder and gently tighten the bolt.
    • Attach both sides to the extruder and secure it with two M3x60 bolts. Insertion of the rear bolt might be tricky. Make sure the hotend is oriented properly. 
  • Cable management
    • Insert the nylon guiding filament inside the hole in the stepper fan shroud
    • Guide the cables through the prepared grooves and the hole in the shroud.
    • Attach the shroud to the stepper using one M3x60 and one M3x18 bolt.
    • Use zip ties to attach the cables to the prepared grooves. 
    • Make sure not to pinch the cables
    • Check if there is no tension from fans and hotend.
    • Use the sleeve to guide the cables to the board
  • Replace Z axis top holder
  • Assemble the funnel
    • Attach the IR sensor using one M3x10 bolt
    • Attach the distributor stepper to the distributor stepper holder by four M3x8 bolts
    • Insert and glue the distributor on the stepper shaft
    • Insert the distributor sub-assembly in the funnel and attach it using two M3x10 bolts.
    • Connect the IR sensor and stepper into the board. You will be able to control it using Arduino and attached code.

First extrusion

  • Connect printer to a computer using the USB cable. Open Pronterface and access the printer.
  • Heat the hotend to 100°C and wait for a couple minutes, continue heating to 200°C and 250°C and observe if the temperature growth is continuous and stable
  • Conduct the PID calibration for 250°C.
  • Use G-codes G92 E0 and G1 E250 F800 to check if the screw is rotating freely.
  • Insert the pellets into the chamber. We recommend PET or PETG pellets of the particle size of 2 mm max in any direction.
  • Repeat the above G-codes until there the material is dripping from the nozzle.
  • Regulate the tension on the top of the screw to achieve continuous extrusion

Slicer settings

It is necessary to significantly increase the flow, remove mesh bed leveling, switch off retractions and slow down the print speed. Find the current configuration file attached. The first layer calibration is not yet implemented, therefore at the beginning of each print it is necessary to recalibrate manually. 

Sample print profile with the object (flowerpot) is attached.

Common errors based on our testing

  • Not extruding at all
    • Check if there are enough pellets in the chamber
    • Check if the screw is rotating in the right direction
    • Check the temperature
    • Increase the grooves on the top part of the extruder
  • Thermal runaway
    • Decrease or switch off the part cooling
    • Check if the heater cartridge is attached properly in the heater block
    • Check the integrity of thermistor cable
  • Clicking in the extruder
    • Tighten the belt
    • Increase the nozzle temperature
    • Decrease the flow
    • Sometimes the screw might be locked inside the chamber and needs to be manually rotated with assistance of the stepper.
    • Experiment with the stepper current, we have set the stepper current to 750 mA by adding M907 E750 G-code extrusion. Watch the stepper for overheating.
    • If it does not help it is possible that an unwanted object (metal) got into the chamber, in this case it is necessary to clean the chamber and nozzle before further printing. 

We will be glad for the feedback of the international 3D printing community.

Attached documents:

  • 3mf files for test prints
  • Drawings - heater block, extruder assembly

Links and inspirations:

Tagi

prusaextrudermk3prusai3mk3pellet