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ENGEL Develops New Two-stage Process for Cost-effective Plastic Waste Recycling

With a new process, ENGEL is able to process plastic waste as flakes in injection molding directly after grinding. Since a complete process step, pelletizing, is eliminated, the innovation significantly improves cost efficiency in plastics recycling. ENGEL presented the new two-stage process to a trade audience for the first time and demonstrated its great potential at its live e-symposium 2021. The new process also offers benefits in the production of very large and thick-walled components with high shot weights.
Key to Low-cost Plastic Recycling
The key to shortening the recycling process is breaking down plasticizing and injection into two independent process steps that are very well tuned with each other. In the first stage, the raw material, for example plastic flakes originating from post-consumer collection, is melted in a conventional plasticizing screw.
In the second stage of the process the melt is transferred to a second screw for injection into the cavity. The two-stage process makes it possible to integrate a melt filter and a degassing unit on the injection unit side of the injection molding machine, so that products with a consistently high quality are obtained even from contaminated plastic flakes.
This innovation sees ENGEL make a further contribution to the establishment of a circular economy for plastics. Pelletizing the recycled material is an energy-intensive process which typically also involves logistics overhead. If this step can be eliminated, the CO2 footprint is improved and recycling costs are also significantly reduced.
Efficient System for Very Large Parts
As an alternative to an injection screw, the plasticizing screw used for creating the melt can be combined with a piston unit. This variant of the two-stage process is also very efficient for processing very large shot weights of up to 160 kg with a comparatively low injection pressure requirement. The two-stage process enables a more compact system design and a lower unit cost than is possible with a conventional single-stage plasticizing and injection process.
ENGEL has developed a new piston design to eliminate the typical disadvantages of piston injection units when changing materials. The rheologically optimized piston tip supports uniform flushing around the piston, enabling fast material and color changes.
Typical applications are containers, pallets or even large fittings. Starting at a shot weight of 20 kg, processing efficiency increases significantly thanks to keeping the plasticizing and injection processes separate.

Publication date: 01/07/2021

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Last update: 2022-01-31