Recycling filament plastic typically involves cutting it into small pieces and pushing them through a screw extruder. [JRT3D] is taking a different approach with PetBot, which cuts PET bottles into tape and then turns them into filaments. See the videos after the jump.
Tape cutting and extrusion occur in two completely separate processes on the same machine. A PET bottle is prepared by cutting off the bottom, and the open edge is pushed between a pair of bearings, where a cutter cuts the bottle into a long strip, while a powered reel winds it up. The tape reel then moves to the second stage of the machine, which pulls the tape through a hot end much like a 3D printer. While most conventional extruders push the plastic through a die with a screw, the PetBot only heats the tape slightly above its glass transition temperature, allowing the driven spool to slowly pull it through the extruder. nozzle without breaking. A fan cools the filament just before it enters the spool. The same stepper motor is used for both stages of the process.
We like the simplicity of this machine compared to a conventional screw extruder, but it’s not without its trade-offs. First, there is the limitation of the length of the filament by the material in a single bottle. Getting longer lengths would involve fusing the tape after cutting or the filament after extrusion, which is not as simple as it sounds. The process will likely be limited to a large soda bottle with smooth outer surfaces to allow the thickness and width of the tape to be as consistent as possible. We are curious to see the consistency of the shape and diameter of the filaments, and how sensitive it is to variations in the thickness and width of the ribbon. That said, as long as you understand the limitations of the machine, we have no doubt that it can be useful.
It doesn’t look like PetBot is open source right now, but if you don’t want to figure out how to build it yourself, you can buy one for $400. [JRT3D] it also says that there is a crowdfunding campaign in the works.
We’ve seen a number of DIY filament extrusion machines over the years, but if saving filament costs is your primary goal, it may not be worth it. A 3D printer that can use plastic pellets is probably a better way to go.
Using my Petbot PET bottle converter…making that PET filament! Recycle! Ginger Green Ale 🙂 pic.twitter.com/5eyURrBjeJ
— Joshua R. Taylor – JRT3D (@joshuartaylor) June 26, 2021