BUILD THIS AND YOUR PLASTIC RUBBISH TURNS INTO NEW MATERIAL
A bin bag of bottles becomes a handful of clean flakes, and the machine that does it costs around two hundred pounds to build from open plans.
by One Army
WorkshopAutomation
- difficulty
- ●●●●○
- time
- a long weekend for the shredder, then more if you build the other machines
- license
- CC-BY-SA-4.0
- repo
- repo ACTIVE0 stars
●●●●○ · a long weekend for the shredder, then more if you build the other machines · CC-BY-SA-4.0 · 0 stars · repo ACTIVE
WHAT YOU’LL NEED
- 3D printer + filament — printable parts — files are in the repo
Partner
COMPAREE VERDICT
This is one of the few open-source projects where the output genuinely changes what you can do at home: a stream of waste plastic that would go to landfill becomes feedstock you can melt, mould and extrude. The shredder is the keystone — without it, you have no flakes, and without flakes the other three machines (extruder, injection moulder, sheet press) cannot run. The documentation is professional: exploded diagrams, dimensioned drawings, an itemised BOM with part numbers and sources. The build itself is not a weekend — you are fabricating a steel frame, aligning a shaft on bearings, mounting a 2.2 kW motor with a reduction gearbox, and installing a hopper over a stack of hardened steel blades that have to be laser-cut to tolerance. If you do not have access to a laser cutter or a local service that will cut hardened tool steel from your files, the blades alone will stop you. The project lists hundreds of community workspaces worldwide, which means the documentation has been tested in the field, but it also means this is aimed at makerspaces, not kitchen tables. The single biggest trap is assuming you can substitute a cheaper motor or skip the reduction gearing: the 70 rpm speed is not arbitrary, it is the difference between shredding and melting plastic onto the blades. If you have the tools, the space and the metalworking confidence, this is a genuinely useful machine. If you do not, the learning curve is steep and the margin for error is narrow.
IN THE REPO
NOT IN THE REPO
- —Complete build documentation for the shredder, extruder, injection moulder and sheet press published at community.preciousplastic.com/academy under Creative Commons Attribution-ShareAlike 4.0.
- —CAD files, bills of materials, assembly guides and technical drawings are all there. The shredder is the documented entry point.
- —No firmware involved — these are mechanical machines driven by mains-voltage motors.
- —The BOM estimate of around 200 pounds is from the project documentation and assumes access to laser-cutting services and scrap steel; actual cost varies by country and local pricing.
- —CC BY-SA 4.0 licence permits commercial use but requires you to release modifications under the same licence.
- —The project does not supply the blades pre-cut or the motors — you source and assemble everything yourself.
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
Precious Plastic shredder build and shredded flakes
No official video URL was provided. The community site may host walkthroughs; check the academy pages.
Gallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the full shredder build guide (Start here. The academy page has the complete BOM, CAD files, drawings and assembly sequence.)
- 2.Confirm you can source or cut the hardened steel blades(The blades are laser-cut from hardened tool steel to the drawings in the CAD pack. If you do not have a local service that will cut this material, the build stops here.)
- 3.Source the motor and reduction gearbox(The project specifies 2.2 kW with reduction to around 70 rpm. Do not substitute a faster motor — the slow speed is what prevents melting.)
- 4.Fabricate the frame and assemble the shaft(Follow the drawings for welding the steel frame and mounting the bearings. Shaft alignment is critical or the blades will bind.)
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
- The blades must be laser-cut from hardened steel to the supplied drawings. If you try to cut them yourself with an angle grinder or substitute mild steel, they will dull or deform immediately. Confirm you have access to a laser-cutting service that works with tool steel before you buy anything else.
- The 70 rpm speed is not negotiable. A faster motor without reduction will melt plastic onto the blades instead of shredding it. The reduction gearbox is part of the design, not an optional upgrade.
- The project BOM estimate of 200 pounds assumes you can source some steel as offcuts or scrap and have access to basic fabrication tools. If you are buying everything new and paying for laser cutting, expect closer to 300–350 pounds.
- This is a mains-powered machine with a 2.2 kW motor. If you are not confident wiring mains voltage safely, pay an electrician or do not build it.
- The shredder only handles certain plastics safely. PVC and some others release toxic fumes when heated or shredded. The project documentation lists safe types — read it before you feed the machine.
- The other three machines (extruder, injection moulder, sheet press) all depend on having shredded flakes as input. If you only build the shredder, you have flakes but no way to turn them into objects. Budget time and money for at least one downstream machine if you want usable output.
Can I build just the shredder, or do I need all four machines?
You can build just the shredder, and it is the documented starting point. But shredded flakes are only an intermediate material — to make anything useful, you need at least one of the other three machines (extruder, injection moulder or sheet press). Many community workspaces start with the shredder and add one other machine later.
What plastics can it shred?
The project documentation lists safe types, typically HDPE, LDPE, PP and PS. Do not shred PVC, polycarbonate with BPA, or anything you cannot identify — some release toxic fumes. The academy site has a detailed guide.
Where do I get the blades cut?
You need a laser-cutting service that works with hardened tool steel. The CAD files include the blade profiles. Many builders report using local industrial laser cutters or online services; cost varies widely by country.
Can I use a different motor?
Only if it delivers the same output speed of around 70 rpm at the shaft. The slow speed is the entire mechanical principle — faster and you melt plastic instead of tearing it. A 2.2 kW motor with reduction gearing is the reference design.
Is the project still active?
The documentation is complete and stable. One Army continues to host the academy and the community map shows hundreds of active workspaces, so the project is in use globally even if core development has slowed.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
Hundreds of these machines are already running worldwide, and the documentation has been tested in the field for years. If you built one, which of the four machines would you start with after the shredder — the extruder, the injection moulder, or the sheet press?
One Army
One Army is a collective that publishes open-source documentation for projects aimed at local production and sustainability. Precious Plastic is their flagship project, released in multiple versions since 2013, with a global community of builders running workspaces on every continent.
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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.
CompareeTEAM16d agoedited
Practical notes from our verification: the project documentation is hosted at community.preciousplastic.com and is unusually complete — exploded diagrams, dimensioned drawings, full BOM with part numbers. The cost estimate of around 200 pounds is realistic if you have access to scrap steel and a local laser cutter, but expect closer to 300–350 if you are buying everything new and paying for blade cutting. The single biggest non-obvious cost is the reduction gearbox — many builders report spending 100–150 pounds on the motor and gearbox alone. The blades must be hardened tool steel; we have seen multiple community posts from people who tried mild steel and regretted it within an hour. No official GitHub repository or video walkthrough was provided, but the academy site is the canonical source and the community forum has years of troubleshooting threads.