Giant moldings brought down to size


Water conservation seems certain to become an ever-more important topic, which must make Graf Plastics GmbH feel pleased. The German processor, using one of the largest injection molding machines in the world, has since late 2006 processed its massive Carat-brand underground tanks for rainwater collection at its Teningen facility.

Sized to hold up to 6500 liters of rainwater, which then is used in toilets, washing machines, or garden irrigation, the tanks are processed on a 5500-tonne twin-platen press from Engel that can inject up to 150 kg of material with each shot. The two halves of the tanks are moulded with this machine and welded together.

Clearly, controlling a 150-kg shot is no easy feat, and just as clearly you cannot afford to throw out any mistakes. Because Graf offers a 25-year guarantee on the tanks, it checks each tank for the correct dimensions, wall thicknesses, and weight. Any scrap, surplus or tanks that don’t pass muster are shredded in a single step with a WLK 30 “Super-Jumbo” single-shaft shredder, which the molder acquired from size-reduction machinery specialist Weima (Ilsfeld, also Germany). This shredder is fitted with a completely closable hopper above the machine housing. On one side, two doors enable opening of the machine and, thereby, access to the rotor. Feeding of the material (as complete tanks or a number of clamshell halves) is done via forklift through this opening. The machine only runs when the doors and hopper access are closed.

The shredded material is delivered through a screen with 10-mm perforations located underneath the rotor. Ground material with low dust content and a particle size of approximately 8-10 mm is realized. [email protected]

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