With a new process, ENGEL makes it possible to process plastic waste as flakes in injection molding directly after grinding. Since pelletizing as a separate process step is eliminated, the innovation significantly improves the energy and cost efficiency in plastics recycling. At K2022, ENGEL is presenting the new two-stage process for the first time as a live exhibit at a trade show. Logistics load carriers with rollers, also known as dolly pallets, are being produced at the ENGEL booth in the Circular Economy Forum.
The direct processing of plastic flakes
To be able to process flakes in injection molding, the recycling process breaks plasticizing and injection down into two coordinated, but independent, process steps. In the first stage, the raw material, for example plastic flakes originating from post-consumer or post-industrial collection, is melted in a conventional plasticizing screw. The melt is transferred to a second screw to inject it into the cavity. Depending on the material and application, a melt filter and a degassing unit can be integrated into the process between the plasticizing and injection units. This means that high-quality products can be created – even from contaminated plastic waste. Processing plastic flakes directly significantly improves the energy and CO2 footprint compared to processing regranulate.
After sorting and cleaning, plastics from post-consumer and post-industrial collection are typically ground, compounded, filtered and pelletized, and finally fed into the injection molding process as regranulate. This means the plastic has to be melted twice. Pelletizing the recycled material is an energy-intensive process which typically also involves logistics effort. This process step is eliminated in the two-stage process. Based on calculations by ENGEL, the required energy for manufacturing the product is reduced by 30%.
The new process is perfectly suited for large-volume molded parts, many of which, such as pallets, transport boxes and waste containers, are already made from recycled materials. Integrated degassing extends the usage to applications in the packaging and automotive industry.
New degassing unit improves product quality
ENGEL developers focused on the degassing unit in particular. Degassing is important to achieve high product quality. Residual moisture, and volatile substances originating from material degradation or ink residues, can pass through the melt filter. If these compounds are not removed before the melt is injected, this can lead to pores on the inside and defects on the surface of the part. This not only harms the visual appeal, but can also reduce the mechanical load bearing capacity of the part.
Another special feature of the ENGEL solution is that the first plasticizing unit in the two-stage process also has the task of buffering raw material. This guarantees a continuous process which supports the use of smaller screws to ensure further cost savings.
Conventional injection molding machines as the basis
ENGEL is demonstrating the new two-stage process at the K show with the production of dolly pallets. A blend of polyolefins from a post-industrial collection is being processed on an ENGEL duo 12060H/80Z/900 injection molding machine.
Production cells for processing recycling flakes in the new two-stage process consists of conventional injection molding machines. This also makes a contribution towards lowering the recycling costs and accelerating the establishment of a circular economy for plastics.
The project partners for the presentation at the show are AVK Plastics, which produces pallets on ENGEL duo injection molding machines in Balk, Netherlands, where some of these machines are already using the new two-stage process, and IPP, headquartered in Ennepetal, Germany, a specialist in logistics solutions for supply chains. The mold for this exhibit comes from Haidlmair (Nußbach, Austria) and the high-performance melt filter for effective removal of solid and elastomer contamination from ETTLINGER (Königsbrunn, Germany). R-Cycle is another partner.
Information transparency for high-quality recycling
The pallets are equipped with an RFID chip and a QR code, which is applied by in-mold labelling. Show visitors can use the QR code to retrieve information about the material and the recycling process from R-Cycle database in real time.
ENGEL joined the R-Cycle Community in spring 2022. The objective of this cross-company initiative is to introduce digital product passports for plastics products. Recycling relevant information is automatically recorded as early as the product manufacturing stage. Therefore, for example, waste sorting plants can identify recyclable plastics more accurately and deliver single grade elements for recycling. In this way, it is possible to stop the downcycling that has been prevalent so far and to recycle plastics equally or even with added value.
ENGEL at K 2022: Circular Economy Forum in the outdoor exhibition area