Prepared material for additive manufacturing: Post-consumer waste is processed into filaments for 3D printing.
The Fraunhofer Institute is transforming millions of metric tons of household plastic waste into high-quality 3-D printed products to meet the growing demand for recycled materials in manufacturing.
In Germany, the plastic waste problem reached unparalleled heights in 2023: 5.6 million. Less than a third of that amount can be recycled; most single-use products are consumed at home. The Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) has developed a system of turning the waste into filaments for 3D printing.
According to Dr. Dirk Godlinski, a project manager in the Composite Technology working group at Fraunhofer IFAM, meeting the “stringent requirements” posed challenges for the company. The material had to meet purity, shape, and size standards.
The company sought assistance from Dr. Silke Eckhardt, a professor at Hochschule Bremen—City University of Applied Sciences (HSB), who focuses on sustainable energy systems and resource efficiency.
In a press release, she explained the difficulties in recycling “post-consumer waste” compared to “plastic residue left over from industrial production.” Not only are the materials highly heterogeneous, but also dirty.
Packaging waste, in particular, has significantly contributed to the increase in plastic waste in households in Germany. Most of these are single-use products. However, Eckhardt’s team took on the task of recycling these “tough-to-handle plastics” for additive manufacturing.
To tackle the challenge, Eckhardt and her team processed the sorting plant output at the university’s laboratories for Circular Economy. They ground up the plastic, washed it, and separated undesired material from the mainstream using a float-sink separation, as per the press release. They identified and removed foreign plastics using near-infrared technology. Lastly, they ground up the plastic to the appropriate grain size and succeeded in reaching a 99.8% purity level.
Turning plastic waste into 3D printing thread
After returning the material to Fraunhofer IFAM, they went to work to produce “homogeneous polypropylene from the prepared waste,” Godlinkski said. “This is a versatile form of plastic that is durable, resistant to breaking, and relatively flexible.”
Once the material had been purified, they processed the flakes of recycled polypropylene in an industrial extruder at Fraunhofer IFAM. Combining the materials, using different extruder screw geometries, they melted it at 392 degrees Fahrenheit.
“The expertise consists in precisely adjusting the various mechanical screws, temperatures, pressures, and speeds along the production process so the final product is homogeneous polypropylene,” Godlinski explained. For the plastic to be useable for 3D printing, they had to produce a strand with a round shape, a diameter of .002 inches, and a smooth surface. With it, the team successfully printed their first components, including caps and the press release notes.
Researchers are now optimizing the production process. Godlinski said the plastics can be further refined by introducing additives such as glass fibers during compounding, which will enable them to manufacture components for aviation and automotive.
“Increasing the demand for recycled materials is important,” Eckardt concluded in the press release. “Especially with regard to climate change, we need to think about resource efficiency. The circular economy is becoming more and more important.” Godlinski agreed: “The more waste we reuse and recycle, the more energy and resources we can conserve.
