This device recycles plastic water bottles into 3D printing filament (and it’s open source)


Here is a prototype of the Polyformer.

Image: Reiten Cheng

Plastics have gotten a pretty bad reputation from an ecological point of view over the years, often for good reason.

The nonprofit ocean conservation organization Oceana reports that: Every minute two garbage trucks of plastic enter the world’s oceans† That’s 33 billion pounds of plastic that ends up in the oceans every year. Map service Arcgis has map data showing that there are five large pieces of plastic-covered ocean covering an area of ​​20 million square kilometers (7.72 million square miles). That’s enough plastic to cover Alaska, Texas, California, Montana, and New Mexico (15 of the United States). largest states by area

The United States Environmental Protection Agency reports that: the US produced 35.7 million tons (about the weight of 17.8 million Tesla Model 3 vehicles) worth of plastic. In total, only 8.7% of the plastic produced is recycled, but that percentage differs per type of plastic because different types of plastic have very different chemical properties.

PLA, or polylactic acid, is the most common type of plastic used in 3D printing† It is a very user-friendly material, it adheres well to the print bed and is fairly robust for many applications. It deteriorates in the sun and can be brittle, but the vast majority of items I’ve made have been printed with PLA as it works well in extrusion 3D printers.

PLA also has environmental benefits. It is not made from fossil fuels, but made from renewable resources such as corn, cassava, sugar cane or sugar beet pulp. PLA is also biodegradable, although there are some clear footnotes to that statement† It doesn’t compost well. About half of the material decays over time, but the rest can stay for hundreds or even thousands of years. For the same reason, you don’t want to dump PLA in landfills. But PLA burns quite nicelyleaves no residue or toxic fumes.

When it comes to recycling, PET (or polyethylene terephthalate) is a winner. According to the EPA, almost 30% of all PET is recycled† This is extremely important because PET is the material used to make plastic water bottles and jars. According to the University of Southern Indiana, Americans use 2.5 million plastic bottles every hourmost of which are discarded after use.

A modified variant of PET known as PETG (Polyethylene Terephthalate Glycol Modified) is also quite popular in 3D printing. PETG replaces the ethylene glycol in PET with cyclohexanedimethanol, which adds six additional carbon atoms. This makes the molecular structure less rigid and allows the plastic to melt at a lower temperature.

PETG will melt at about 230°C. In contrast, PET (the water bottle plastic) will melt, but at temperatures closer to 280°C. That’s near the top of the temperature range for most hobby level 3D-level extruders. printer.

The fact that PET can technically be 3D printed raises a simple question: how can we convert plastic water bottles into 3D printable filament?

Reiten Cheng, an industrial designer who just graduated from the ArtCenter College of Design in Pasadena this spring, seems to have an answer. And his open source† He calls it the Polyformer


Polyformer Heated Extrusion Mechanism

Image: Reiten Cheng

The idea for the Polyformer is simple. Use scissors to cut the bottom of a water bottle. Place the bottle in the Polyformer. The device cuts the bottle into strips. An extruder heats the strips and pushes the plastic filament out. From used bottle to ready-to-use filament, it’s an idea with potential.


Image: Reiten Cheng

Although filament comes in larger and smaller quantities, most filament is sold on 1 kilogram spools. When I talked to Cheng about his Polyformer Discord Channelhe told me that about 33 bottles would yield a kilo of spool of filament.


Image: Reiten Cheng

I see this as a great community or makerspace project. A school or makerspace could collect the bottles and turn them into filament spools.


3D printed parts and additional components that make up the Polyformer . consists

Image: Reiten Cheng

As I mentioned above, PET is a bit of a challenge for 3D printing, especially with how stringy it gets and how difficult it is to enter the temperature settings. But once that’s figured out, a school or makerspace can have a virtually infinite (and free) supply of this very robust 3D printing material.


I was especially curious about how the bottles are cut. Discord user @Alextrical told me that: “It’s the bearings that cut the bottle, slide the edges together and shear the plastic off, akin to scissors.” So this would be safe in a community setting and there are no issues with sharpening or replacing blades.

It should be noted that Cheng is not the first to build a PET plastic to filament recycling device. He cites Joshua Taylor as inspiration on:, which has plans and parts lists for a similar device. Taylor’s approach is to convert a Reality Ender 3 3D printer into a “Plastic Bottle Pultrusion Unit”.

It’s an interesting approach — upcycling a 3D printer to make a device that recycles plastic bottles to use as filament for a 3D printer.

So what about you? Do you think you will build such a device? Do you want to contribute to the recycling of plastic bottles by turning them into 3D printing filament? Let us know in the comments below.

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