Direct Granules Extruder Uses Plastic Waste as Filament
Norbert Heinz's project is meant to be a drop-in replacement for existing desktop filament extruders with no additional electronics needed.
By using off-the-shelf components and open source hardware, Norbert Heinz developed an inexpensive Direct Granules Extruder for desktop 3D printers. It relies on a traditional wood screw as an auger to drive the granules from the cold zone. The whole concept behind this project is straightforward: break down plastic waste into pellets, melt them, and extrude them in a modified 3D printer. However, it still has some issues that need to be solved. Heinz is currently working on those and has produced some pretty crafty prints. It’s also capable of printing sugar!
Not only that, but he also found a way to use raw material as granule, which prints out various materials too soft or brittle to be processed as filament. He produces the raw material by grinding up old plastic bottles in a blender. The extruder also operates with a Zonestar QR2 printer mechanism, a weak stepper motor, and a heating cartridge.
It consists of a coldend and hotend, made of a 16x16mm square bar. A piece of glass separates both zones to minimize heat flow from the hot to the cold side. A 10mm Teflon tube runs from the coldend to hotend, ensuring less friction on the walls. The screw conveyor features a 5mm wooden screw with a 25mm wire soldered to the top. Heinz expanded the brass nozzle, allowing the plastic to move through without much resistance. Both the heating cartridge and temperature sensor are positioned to provide sufficient distance from the central hole. The screw connection between the hotend and coldend is made using two long pieces of 3mm threaded rods to provide a low heat transfer. Lastly, the granules move through the coldend to the hotend along with a Teflon tube.
With this setup, he printed both a gear and a rocket. The gear, measuring 25x25x10mm with a 0.2mm layer thickness, was printed from sugar, which changes to a brownish color through the nozzle due to a caramelization reaction occurring at temperatures higher than 140° C. However, the surface isn’t very smooth because the surface tension interacts with the lower viscosity of the melted sugar. The rocket, made of PLA material, was printed for the 2021 Hackaday prize, placing fifth overall. The rocket didn’t print properly at the top because a cooling fan wasn’t present.