THIS DEVICE RECYCLES PLASTIC WATER BOTTLES INTO 3D PRINTING FILAMENT (AND IT'S OPEN SOURCE)
About 33 empty water bottles become one kilogram of 3D printer filament, and the cutting head has no blades to sharpen.
by Reiten Cheng
WorkshopOpen-hardware
- difficulty
- ●●●●○
- time
- a long weekend
- license
- GPL-3.0
- repo
- repo ACTIVE1,153 stars
●●●●○ · a long weekend · GPL-3.0 · 1,153 stars · repo ACTIVE
WHAT YOU’LL NEED
- 3D printer + filament — printable parts — files are in the repo
- Electronic parts — full list with part numbers in the repo BOM
- Dev board / microcontroller — runs the project firmware
Partner
COMPAREE VERDICT
The Polyformer shears a PET water bottle into a continuous strip and extrudes it as printable filament. The cutting head uses two bearings whose edges slide over each other like scissors, so there is nothing to sharpen or swap out. That design choice is also what makes the machine viable in a school or makerspace. The creator, Reiten Cheng, stopped supporting the project in late 2025, but the files, part list, and community are all still open. Two things will catch you early: PET melts closer to 280°C than the 230°C of PETG, so the printer you use to make the parts must handle over 260°C and must not be PTFE-lined, and the build involves high voltage components plus moderate VOC fumes during extrusion. The project explicitly says to get help from a maker or electrician for the electronics if you are not confident. The single most common mistake is buying a heater barrel from an unverified supplier and finding it does not fit the mounting holes. If you print a lot and you have access to a workshop where mains voltage and fumes are not a problem, this is one of the most honest open recycling projects available. If you expected a kit or a plug-and-play device, this is not that.
IN THE REPO
NOT IN THE REPO
- —All STLs, electronics list, and assembly instructions are in the repository.
- —The firmware is Arduino-based and the code is provided.
- —The project carries a CC BY-NC-SA 4.0 licence — you may build and modify it but not sell the machine commercially.
- —The creator stopped supporting the project in late 2025 after three years.
- —The repository does not include a tested source for the heater barrel or the specific motor driver board shown in early builds.
- —You must own or borrow a 3D printer that can print above 260°C and is not PTFE-lined to make the parts.
Can I build this?
This build involves mains voltage — for adults comfortable with electrical work only.
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Partner · KickstarterHeyGears G1: 10M+ colors and transparent parts in one print, plus UV printing on flat objects. Figures, parts and labels — no painting.
Videos
Community walkthrough video linked from the repository. Not produced by the creator.
Gallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Check your printer can print above 260°C and is not PTFE-lined(If your hotend is PTFE-lined, the PTFE will degrade at the temperatures needed to print the Polyformer parts. An all-metal hotend is required.)
- 2.Read the full BOM in the repository and verify you can source the heater barrel (The heater barrel is the part most builders struggle to source. Verify the mounting dimensions before ordering.)
- 3.Print the structural parts and assemble the frame before ordering electronics(This lets you test fit and catch dimensional issues before committing to the full electronics order.)
- 4.Get help from a maker or electrician for the mains wiring if you are not confident(The project explicitly recommends this. Mains voltage mistakes are not recoverable.)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- Buying a heater barrel from an unverified supplier and finding it does not match the mounting holes in the printed parts. Verify dimensions before ordering.
- Using a PTFE-lined hotend to print the parts. PTFE degrades above 260°C; you must have an all-metal hotend to print the frame safely.
- Underestimating the fume output during extrusion. PET produces noticeable VOC when melted. Work in a ventilated space or outdoors, not in a closed bedroom.
- Skipping the test cuts and going straight to full extrusion. The bearing shear mechanism needs tuning; if the gap is too wide the strip tears, if it is too tight the motor stalls.
- Expecting the filament to match commercial PETG. This is recycled PET, and it behaves differently. Print temperatures and retraction settings will need experimentation.
- Assuming the project is still actively supported. The creator stopped updating the repository in late 2025. The community Discord is your primary support channel now.
Can I sell the machines I build?
No. The project uses a CC BY-NC-SA 4.0 licence, which prohibits commercial use. You may build and modify it, but not sell it.
Does the filament print like commercial PETG?
Not exactly. This is recycled PET, and it melts at a higher temperature (closer to 280°C) than commercial PETG (around 230°C). Expect to tune your print settings and retraction.
How long does it take to process 33 bottles?
The cutting and extrusion are not the bottleneck — collecting, cleaning, and drying 33 bottles is. Budget a few hours for the full process once you have the bottles ready.
Is the creator still supporting the project?
No. Reiten Cheng stopped supporting the project in late 2025 after three years. The files and community are still open, but there are no further updates planned.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
About 33 bottles make one kilogram of filament, and the shear mechanism uses bearing edges instead of blades. What would stop you from building one this weekend?
Reiten Cheng
Reiten Cheng is an industrial designer who built the Polyformer as a graduating project at ArtCenter College of Design in Pasadena. The machine was designed to work in schools and makerspaces, which is why the shear mechanism uses bearings instead of blades. Cheng stopped supporting the project in late 2025 after three years, but the repository and community remain open.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM28d agoedited
Practical notes from our verification: the repository is complete but the creator stopped supporting the project in late 2025, so the community Discord is now the primary support channel. The single biggest trap is the heater barrel — builders report that unverified suppliers often ship barrels that do not match the mounting holes in the printed parts, so verify dimensions before ordering. The ZDNET article and the repository both emphasise that your printer must handle over 260°C and must not be PTFE-lined, which rules out many stock Ender 3s and Prusa Minis. If you meet those requirements and you have a workspace rated for mains voltage, this is one of the most honest open recycling builds available.