In an interview with K-MAG, Bianca Gubi explains how the new process works, the benefits for the climate and customers, and what to expect at the ENGEL booth at K 2022.
You have developed a new process for processing plastic waste. How does this work exactly? What is different from the conventional process?
Bianca Gubi: The special feature of the two-stage process is that plastic waste can be processed as flakes in injection molding directly after grinding. For this purpose, we have divided plasticizing and injection into two independent but coordinated process steps. In the first stage, the raw material, i.e. the plastic flakes that come from the yellow bag, for example, is melted in a conventional plasticizing screw. The melt is transferred to another screw for injection into the cavity in the second process stage. A melt filter and a degassing unit can be integrated in the transfer from the plasticizing screw to the injection screw. This enables high-quality products to be obtained even from contaminated plastic waste.
How is the corresponding production plant structured?
Gubi: Instead of a large plasticizing screw, which would normally be used in standard injection molding, there is a smaller plasticizing screw and a shorter injection screw. The two screws are arranged one above the other, which makes for a comparatively compact design of the system. The melt filter and the degassing unit are optional. They form the transition from the plasticizing screw to the injection screw. The degassing unit is a proprietary ENGEL development. Degassing is necessary because certain impurities, such as residual moisture as well as low-molecular compounds originating from material degradation or ink residues, can pass through the melt filter. If these impurities are not removed before the melt is injected, this can lead to pores in the interior and defects on the surface of the component and thus reduce its mechanical load-bearing capacity. The degassing unit thus makes a significant contribution to ensuring that recyclates can also be used for high-quality applications. The modular design makes the process very flexible.