Recycling plastic to filament usually involves chopping it into tiny pieces and pushing it through a screw extruder. [JRT3D] goes a different way with PetBot, which cuts PET bottles into duct tape and then converts it into filament. Watch the videos after the break.
The cutting of the strip and the extrusion take place in two completely separate processes on the same machine. A PET bottle is prepared by cutting off the bottom and sliding the open edge between two bearings where a cutter cuts the bottle into a long strip while a powered reel rolls it up. The tape reel is then moved to the second stage of the machine, which pulls the tape through a hot end very similar to that of a 3D printer. While most conventional extruders use a screw to push the plastic through a nozzle, the PetBot only heats the tape slightly above its glass transition temperature, which allows the powered spool to pull it slowly through the nozzle without breaking. A fan cools the filament just before it goes onto the spool. The same stepper motor is used for both stages of the process.
We like the simplicity of this machine compared to a traditional screw extruder, but it is not without compromises. First, the limitation of filament length by the material in a single bottle. To get longer lengths, the ribbon has to be fused after cutting or the filament after extruding, which is not as easy as it may seem. The process would likely be limited to large soda bottles with smooth outer surfaces so that the thickness and width of the tape could be as uniform as possible. We are curious about the consistency of the filament shape and diameter and how sensitive it is to variations in the thickness and width of the ribbon. However, 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] also says that a crowdfunding campaign is in the works.
We have seen several DIY filament extrusion machines over the years, but if your main goal is to save filament costs, they may not be worth the effort. A 3D printer that can use plastic pellets is probably a better way to do it.
With my Petbot, PET Bottle Converter … produce the PET filament! Recycle! Ginger Ale Green 🙂 pic.twitter.com/5eyURrBjeJ
– Joshua R. Taylor – JRT3D (@joshuartaylor) June 26, 2021