Shredding & Recycling Plastic Purge Lumps from Injection Molding & Extrusion

Machines in the WLK series are ideally equipped for a wide range of plastics tasks. The machine design is characterized in particular by its durability and robustness. Thanks to the conveyor belt cut-out, all machines can be seamlessly integrated into any production line. They also offer a wide range of options in terms of drive and cutting geometry.

With rotor lengths of 1,400 to 2,200 mm, the shredders in the W5 series shred large-volume plastic tanks and plastic garbage cans with ease. The hydraulically upward pivoting screen basket and the inspection flap allow foreign objects to be removed quickly and facilitate maintenance. Large quantities of plastic flakes can be transported via the wide conveyor belt cut-out.

With their extremely sturdy design and large rotor diameters of up to 700 mm, shredders of the S7 series offer almost unlimited possibilities for the shredding of plastic waste. They are up to any challenge and can be equipped with a powerful hydraulic drive.

In plastics processing, especially during extrusion and injection molding, material waste is generated at the start of production. These solid plastic residues are known by many names: purge lumps, purge cakes, start-up scrap, sprues, butzen, rejects, or simply purge waste. But no matter the name, they all refer to the same issue: bulky, hard-to-recycle plastic waste that takes up space and should be handled efficiently.

In injection molding processes, plastic waste and production scrap occur regularly, especially when parts are out of spec, edge trims are needed, or sprues and start-up purges form. Such purge waste is also created during machine trials, production breaks, or when restarting equipment. If the scrap is mono-material, it is considered high-quality and can ideally be regranulated and reintroduced into the production cycle.

Large, voluminous, and difficult to handle – that’s what purge lumps typically look like in the plastics industry. But anyone who considers them worthless underestimates their potential. Around the world, companies like Rowad Plastic and Napco National rely on WEIMA shredding technology to handle the first step of plastic purge recycling. Whether you're a plastics manufacturer, processor, or chemical company, the challenge is always the same: reduce start-up lumps to a uniform particle size suitable for further processing or reuse. In practice, single-shaft shredders, often combined with downstream granulators, are proven solutions for reliably processing even the largest purge blocks.