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 is built from open plans, steel and a geared-down motor.
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
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COMPAREE VERDICT
This is one of the few open-source projects where the output genuinely changes what you can do: waste plastic that would go to landfill becomes clean flakes you can wash, store, sell or feed into the extruder, injection moulder or sheet press. The shredder is the backbone of the Precious Plastic system. The documentation includes drawings, a download kit with schematics and an official build video. The build is real metalwork: the academy lists a lathe, a drill press, a welder and a belt sander, and intermediate welding, machining, assembly and electronics skills. The drive is a motor of about 2.2 kW geared down to around 70 rpm, with at least 300 Nm of torque, and the reference spec runs on 380 V, so check your power supply before buying a motor. The blades and plates are cut from 5 and 6 mm steel to the supplied drawings. The academy prices the build at roughly 500 euros plus the motor with new material, or 400 euros plus the motor with scrap material (Netherlands). The single biggest trap is skimping on the motor and gearbox: without enough torque the machine simply stalls. If you have the tools, the space and the metalworking confidence, this is a genuinely useful machine; if not, the learning curve is steep.
IN THE REPO
GOOD TO KNOW
- —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 academy estimates about 500 euros plus the motor with new material, or about 400 euros plus the motor with scrap material (Netherlands prices); actual cost varies by country.
- —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.
Parts to buy
7 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
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.
Videos
Precious Plastic - Build the shredder (part 3.1)
One Army's official build video for the shredder: the shredding box, power supply, frame and hopper, step by step.
More builds like this
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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 blade and plate drawings are in the download kit; find a cutting service that can cut them accurately in the specified steel before you buy anything else.)
- 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 and other plate parts come from the drawings in the download kit (5 and 6 mm blade plates). Check the specified steel and decide early how you will get them cut accurately — most builders use a local laser-cutting service.
- The drive must deliver at least 300 Nm at around 70 rpm. A motor without the reduction gearbox will not have the torque to cut plastic; the gearbox is part of the design, not an optional upgrade.
- The project estimate is about 500 euros plus the motor with new material, or about 400 euros plus the motor if you use scrap steel (Netherlands prices). Laser-cutting the blades and buying a geared motor can push it higher, so price both locally before you start.
- This is a mains-powered machine: the reference spec is a 380 V motor drawing 5.8 A. Check what supply you have before buying a motor, and if you are not confident wiring mains safely, pay an electrician.
- 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?
The blade and plate drawings are in the download kit; most builders have them laser cut by a local service from the steel specified in the kit. Cost varies widely by country.
Can I use a different motor?
Only if it meets the spec: at least 1.5 kW and 300 Nm of torque at around 70 rpm output (the academy suggests about 2.2 kW geared down to 70 rpm). The slow, high-torque drive is what lets the blades cut plastic; a fast motor without reduction will simply stall.
Is the project still active?
The documentation is complete and stable, and One Army continues to host the academy and the community site, where builders ask questions and share their workspaces.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
The academy prices the shredder at roughly 400 to 500 euros plus a motor. If you built one, which machine would you add next — the extruder, the injection machine, 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.
CompareeTEAM2mo agoedited
Practical notes from our verification: the official build documentation lives in the Precious Plastic Academy on community.preciousplastic.com, and One Army has published an official build video (Build the shredder, part 3.1) that the academy page also embeds with chapters. The academy's own price estimate is roughly 500 euros plus the motor if you buy new material in the Netherlands, or roughly 400 euros plus the motor with scrap material — so the motor is a separate line you have to price yourself, and it is easy to forget when you compare this to a commercial shredder. The community site also has a questions section where builders ask for help. Read the academy page end to end before you order laser-cut parts, and decide on your motor first, because everything else is sized around it. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.