Inject direct: ENGEL processes waste as flakes

With a new process, ENGEL has the ability to process plastic waste as flakes in injection moulding directly after grinding. With the elimination of pelletising, the innovation significantly improves cost efficiency in plastics recycling.

At its live e-symposium 2021, ENGEL is presenting the new two-stage process to a trade audience for the first time. The process also offers benefits in the production of very large and thick-walled components with high shot weights.

The key to shortening the recycling process is breaking down plasticising and injection into two independent process steps. In the first stage, the raw material is melted in a conventional plasticising screw. In the second stage, the melt is transferred to a second screw for injection into the cavity. This process enables integration into a melt filter and degassing unit on the injection unit side of the injection moulding machine, so that products with a consistently high quality are obtained even from contaminated plastic flakes.

Pelletising recycled material is an energy-intensive process. The elimination of this step results in the reduction of a CO2 footprint, as well as an improved recycling cost.

As an alternative to an injection screw, the plasticising 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 160kg 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 plasticising and injection process.

ENGEL has developed a new piston design to eliminate the typical disadvantages of piston injection units when changing materials. The rheologically optimised piston tip supports uniform flushing around the piston, enabling fast material and colour changes.

Typical applications are containers, pallets or even large fittings. Starting at a shot weight of 20kg, processing efficiency increases significantly thanks to keeping the plasticising and injection processes separate.