Dave began developing a series of low-tech machines to move plastic recycling from expensive, large, industrial-scale factories, and into the hands of enthusiastic makers looking for new, more environmentally friendly materials to work with. The resulting set of open-source, easy-to-build machines enables almost anyone, anywhere, to contribute to plastic recycling, while opening up new opportunities for economic development and job creation. Since launching the Precious Plastic project in 2013, over 200 plastic recycling workspaces have been set up, and new ones are opening up around the world every week.
The complete kit consists of four main machines constructed from sheet metal and scrap parts: a shredder for creating waste plastic flake, an extrusion machine for processing the plastic flake into 3D printer filament and granulated plastic, an injection moulding machine for the production of very precise objects, and finally a compression oven for making large and durable objects. Dave’s website, preciousplastic.com, acts as the central hub from which his community of over 100 000 participants organise and educate themselves. The page for each machine includes all the details you need to build one yourself. There’s also information on how to use the recycled plastic to make everything from building materials and household items, to phone cases and even cheap and cheerful jewellery.
Finally, the site’s global online marketplace, known as the ‘Bazar’, helps community members to generate income through their plastic recycling activities, by selling recycled products and machine parts. One example is Koun (which in Arabic translates as ‘either’), a social enterprise based in Morocco which employs young people to collect and transform plastic waste into products, which are sold through the online Bazar and their bricks-and-mortar store in Casablanca.
Create new products
Koun collects raw material from local schools, businesses, and the streets of Casablanca’s Medina itself, which is then cleaned and processed before being sent to one of three workshops to make furniture, clothing, or stationery.
“What makes Koun special is their ability to merge Precious Plastic with traditional Moroccan crafts, by combining plastic with metal, wood, and textiles in unique ways,” says Dave.
So far, Koun estimates that around 22 000 kilograms of waste material has been recycled into new products. “Even though they’re still far from fully covering their expenses with sales, we believe they’re on the right path to make the project financially sustainable in the near future.”
On 26 May 2018, the FAMAE Foundation awarded 300 000 euros to the Precious Plastic project, to further develop their machines. The plan for Precious Plastic Version 4, as Dave describes it, includes the development of semi-industrial systems that are capable of recycling plastic in much larger quantities than is currently achievable with the existing open-source machines. Dave also plans to welcome 45 volunteers from around the world to work on the project from his new warehouse in the centre of Eindhoven. Let’s take a look at the machines.
Dave Hakkens's Shredder Machine
The industrial process to reclaim waste plastic typically starts with manually dividing the collected material by type and colour. The most common waste plastic laying around your home is probably PET (polyethylene terephthalate) used for drinks bottles, and HDPE (high-density polyethylene) used to produce household detergent and shampoo bottles.
Once divided by type and colour, the waste plastic is passed through a slow-moving shredder to produce chips of various irregular sizes. The resulting chips are washed thoroughly to remove contaminants, such as chemical residue, food and labels, and then passed through a second machine called a granulator. The granulator runs at a higher speed than the shredder, and is designed to produce flake feedstock of a specific size for recycling into new products. According to Dave, the going rate for cleaned flake feedstock is eight to ten times higher than unshredded plastic, and 10 kg of clear PET flake typically sells for around £70 on the community Bazar.
Although the Precious Plastic Shredder machine is capable of producing flake feedstock directly from unprocessed plastic waste without the need for a separate granulator, Dave suggests breaking up bigger plastic objects into smaller chunks with hand tools as a precautionary measure, to prevent the machine from jamming.
The bill of materials cost for the Shredder machine sits at around £200, depending on your location, which is remarkably good when compared to prefabricated models of a similar specification. Commercial shredders typically start at around £2000 if you’re willing to have one shipped directly from China, and cost significantly more if purchased from Europe or the United States.
Shred that plastic!
While exploring the documentation, you may notice that although detailed CAD drawings are provided for the cutting blade design, only a loose framework is suggested for the machine’s overall construction. There is a good reason for this. The Shredder’s loose design can be adapted for any motor with a power of +/- 2 kW and output speed of +/- 70 rpm, which means the size and shape of the motor selected may vary wildly from one build to the next.
The output size of the flakes can be changed by altering the size of the sieve placed within the machine to act as a filter. “Different sizes of flakes will give a different pattern; smaller flakes melt easier, but take longer to shred,” explains Dave.
When you finish working with the shredder, make sure to store away the shredded plastic or the next person using the shredder won’t know what plastic type is in the bucket. Now you’re ready to start producing new products!
Dave Hakkens's Extrusion Machine
he Extrusion machine is used to process flake feedstock into a continuous plastic thread which, in turn, can be used to make new raw materials, such as granulated plastic and 3D printer filament, or even spun around moulds to form unique products. “Technically, if you have enough plastic and a well-streamlined process, you could be recycling 24/7,” explains Dave.
Overall, the process is very straightforward and easy to understand, which makes it great for educational and demonstration purposes. Flake feedstock is inserted into the hopper and then pushed along a narrow steel barrel by an extrusion screw, which moves the material towards band heaters, positioned uniformly along the length of the barrel. Once the flake feedstock reaches 130 to 170°C, the molten plastic is pushed through an extrusion nozzle to form a single continuous thread.
Sell your recycled products
If working with steel moulds, the molten thread emerging from the nozzle is repeatedly wrapped around the mould until the desired effect is achieved and the new product is formed. Dave says that an important point to keep in mind when using this technique is always to design moulds with convex walls, as this makes it much easier to release the plastic product from the mould without damaging it. Mastering this process generally requires a bit of patience and practice, but anyone should be able to make unique and interesting objects after a few attempts.
The latest documentation suggests using a wood auger to transport flake feedstock down the barrel, but commercial extrusion machines use purpose-built reciprocating screws. Theoretically, the mechanical energy generated by these screws rotating inside of the barrel reduces the amount of electrical energy consumed by the band heaters to melt the plastic, resulting in a more energy-efficient system. However, the added friction requires a more powerful (and likely more expensive) motor, which is why the use of an industrial extrusion screw is mentioned as an optional upgrade, rather than a base design.
Similar to the Shredder, the total bill of materials cost for the machine sits at around £200, depending on your location. “We used a 100 rpm 12 V DC motor, digital speed controller, and 12 V DC power supply designed for high wattage LED installations,” explains Simon Clark, who travelled to Haiti in 2016 to help his cousin Sarah set up a community-based Precious Plastic workshop. “For the body of the extruder, we started with a stainless pipe, cut out the hopper hole, and welded on plates for the hopper to attach to,” he says. “The extruder build was completed on the second last day of the trip.”
Dave Hakkens's Injection Machine
Injection moulding is one of the most commonly used methods to mass-produce plastic products. It is very similar to extrusion moulding, with the main difference being the way the molten plastic is distributed into the mould. The industrial process typically involves melting granulated plastic inside the barrel of an injection machine, which is then pushed into a temperature-controlled split mould at high pressure by an internal reciprocating screw. This process is the most common modern method of manufacturing plastic parts, and can be used to make everything from small kitchen items and bathroom appliances to outdoor cabinets, sheds, and large playground items for children.
In comparison, Dave’s Injection machine is designed to produce small batches of very precise, detailed objects, such as phone cases or desktop toys. First, flake feedstock is fed into the barrel and then heated for 15–20 minutes. Once the plastic in the barrel reaches a molten state, pressure is applied using a steel plunger, operated by a hand-powered lever.
Once the plunger has forced the molten plastic into the mould, the mould can be carefully removed and cooled before opening. “The process in itself is tightly connected with moulds and mould-making. If you have a precise mould, you can create beautiful products in a matter of minutes and start a little local production,” says Dave. However, unlike the Extrusion machine, which uses a reciprocating screw to mix the flake feedstock in the barrel, the Injection machine cannot homogeneously blend different coloured plastics. “The output colour is often unpredictable when mixing colours in the barrel, allowing for surprising patterns that can add to the beauty of your products,” Dave explains. Complex moulds can be made using a CNC mill or aluminium foundry and a bit of welding.
A precious material
At around £120 (depending on your location), the total bill of materials cost for the Injection machine is around 40% less than the Shredder or Extrusion machine. This is mostly thanks to the system’s manual operation, which does not require a motor. It is worth noting, however, that this does not include the cost of fabricating or purchasing a mould.
Optional upgrades include insulating the barrel using ceramic wool, and a perforated steel sheet to reduce heat transfer with the surrounding air, improving the energy efficiency of the entire system. “To create an efficient process, it is advisable to run the machine for a few hours once it is started. Don’t start and stop the machine too often as the process will be very inefficient,” says Dave.
Dave Hakkens's Compression Machine
ompression moulding is one of the original processing methods for manufacturing plastic parts, and was widely used in the bakery industry before plastic materials even existed. Today, compression moulding is commonly used to manufacture car parts and household appliances. Polymer feedstock is directly placed into a heated mould cavity, and pressure (usually ranging from 800 to 2000 psi) is applied by a hydraulically driven press, until the material has conformed to the shape of the mould. Throughout this process, heat and pressure are maintained until the polymer feedstock has been cured. While most commercial applications use only thermoset polymers, Dave’s machine is designed to use recyclable thermoplastics, including HDPE.
Dave’s Compression machine uses an electric kitchen oven to heat flake feedstock for 30 to 40 minutes, before a car jack applies pressure to the molten material by pushing the mould against the ceiling of the oven. After a couple of minutes of applying pressure, the car jack can be released and the mould can be removed for cooling in air or water. Once the mould has cooled, it can be safely opened, enabling you to inspect your new product. If mixing different-coloured plastic flake, the Compression machine gives a mottled, flake-like look to plastic. This process is generally slower than extruding or injecting, but it allows for more ambitious products to be created. “This machine can also be used to create new raw materials, like big sheets of plastic,” says Dave.
Overall, the Compression machine is simple to understand and very powerful, when properly mastered. It can be operated by a single person and can be used to easily create beautiful products, provided you have the right mould and materials. The bill of materials cost is comparable to the Injection machine (around £120, depending on your location).
If you want to speed up your rate of production, an optional upgrade is to move the compression area to the underside of the machine so the oven can be used to heat up another mould while the first is being compressed and another cooled. This way, the machine can run continuously.
“Besides being more productive and efficient, this upgrade makes the machine easier to build as you don’t need to install the compression mechanism inside the oven,” reveals Dave.
Precious Plastic isn’t going to solve the problem of waste plastic by itself, but, as Dave said above, “Precious Plastic is, above all, a cultural tool to change the way society perceives plastic”, and it’s well on its way to achieving this goal. It’s enabling makers not only to take plastic out of the waste system, but show just how beautiful waste products can become when they’re treated with care and an artist’s eye.
Don’t forget that you can find out more, and apply to join Precious Plastic as a volunteer, by paying a visit to their site at next.preciousplastic.com.
