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One of the most common material applications of plastics shredding is the processing of so-called plastic lumps, which are usually generated as a waste product during the extrusion of plastics. The economic potential of this "purge" is enormous. It is expensive to dispose of the unused purge lumps. Recycling offers the possibility of seamlessly reintegrating production scrap into the manufacturing process instead of using new resources.
Plastics, which accumulate as production waste at the beginning of the extrusion or injection molding process are known as plastic lumps, petrochemical lumps or extrusion lumps. It is also called "purge" in the US.
During injection molding production, there are often production waste and scrap. These occur primarily when molded parts do not meet the desired specifications, edge trims have to be made or injection molded parts are cast on. Moreover, plastic waste also occurs during production breaks, machine tests or in the start-up phases of the machines. If the waste material is pure, it can be returned to production on site. The recycling of start-up lumps reduces the amount of waste and thus effectively reduces the impact on the environment and on disposal costs.
Many companies worldwide rely on shredding technology from WEIMA when it comes to the first process step of recycling extrusion lumps, for example Rowad Plastic and Napco National . Plastics manufacturers, plastics processors and chemical companies must reduce the material to a homogeneous particle size for further processing. Usually this is done by using a single-shaft shredder and downstream granulator.
Thermoplastics are types of plastics that are easily deformable at a defined temperature. In contrast to thermosets and elastomers, however, forming can be repeated as often as required. The only restriction is the need to avoid overheating, which would otherwise lead to thermal decomposition of the material. Well-known thermoplastics include polypropylene (PP), polycarbonate (PC), polyamide (PA), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC) and acrylonitrile butadiene styrene (ABS).
Did you know?
The forefather of thermoplastics is celluloid. It has been known and produced the longest.
With a working width of 600 mm and a rotor diameter of 260 mm, the WLK 4 shredder is one of the most compact of its kind. It is perfectly suited for small and medium throughput rates and, thanks to its comparatively small footprint, requires very little floor space. Nevertheless it is as robust and versatile as larger model series.
Machines of the WLK series are ideally equipped for a wide range of plastics tasks. The machine design is characterized in particular by durability and robustness. Thanks to the conveyor belt cut-out, all machines can be seamlessly integrated into any production line. They also offer numerous options in terms of drive and cutting geometry.
With the W5 series, you can shred anything: from hard, large-volume injection molding waste to tear-resistant fibers and films. The innovative inspection flap guarantees maintenance-friendly access. The swing ram optimizes material feed and thus the shredding result.
With their extremely sturdy design and large rotor diameters of up to 700 mm, shredders of the S5 and 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.
Two-stage processing of plastic production waste
In order to optimally prepare plastic waste for extrusion lines, it must be shredded to the smallest possible particle size. Usually this is done in a two-stage process, consisting of a pre-shredder and a post-shredder, which are connected to each other with conveyor technology (conveyor belt or screw conveyor).
While the pre-shredder shreds the plastic to a size of approx. 20-60 mm, the granulator grinds the material to approx. 3-12 mm.
The V-rotor developed by WEIMA is universally applicable and made of solid material. Its aggressive material feed with up to two rows of knives guarantees a high throughput with low power requirements. It can be equipped with hardened steel cutting knives in the edge lengths 30 mm and 40 mm. These can be turned several times in case of wear, which drastically reduces maintenance costs.
WEIMA shredders for processing highly abrasive materials can be protected with various options to reduce wear and thus downtime and maintenance costs. The heavy wall thickness of the machine frame makes WEIMA shredders particularly robust. The rotor can be reinforced with Vautid, the screen with Creusabro. To protect the cutting knives against the impact of foreign objects, large knives with edge lengths of up to 130 mm x 130 mm can be selected. If the number of knives is small. Vautid can also protect knife holders.
To avoid increased wear of the rotor face plates, we recommend the installation of replaceable Creusabro wear plates on both sides. The cutting chamber can also be reinforced and optionally lined with exchangeable Creusabro plates. Wear protection does not stop at the screen, which defines the material size. For particularly high wear, we offer a screen reinforced with Creusabro with a wall thickness of approx. 20 mm.
What is Creusabro?
Creusabro is a high performance wear resistant steel. Compared to low alloy wear resistant steels, Creusabro has a higher heat resistance. WEIMA uses Creusabro with a hardness of 58 HRC.
What is Vautid?
Vautid is a buildup welding material that can be applied to components as a welding alloy. In WEIMA shredders, Vautid with 62 HRC is applied.
What is Hardox?
Hardox it an abrasion resistant steel and is mainly used as wear plate with a hardness of up to 600 HBW. Depending on the requirements, different degrees of hardness can be applied.
Select your preferred drive type
In most cases, single-shaft shredders are equipped with an electromechanical drive. The power is transmitted by means of a norm motor, the specially developed WEIMA WAP gear and a power belt. The speed is adjustable.
The high-torque, multi-pole synchronous motor from Baumüller is produced in Germany and is characterized by its insensitivity to foreign objects. Without gears, the drive resists shocks and vibrations and thus has a particularly long service life – even when shredding challenging material streams.
Hydraulic drives from Hägglunds / Bosch Rexroth have no gearbox and are therefore particularly insensitive to many impurities. Speed and torque can be adjusted without current peaks. The robust drive provides high torque at low kW power. The speed can be variably adjusted by means of a regulating pump.
Heavy-duty machine design
for solid plastic lumps and rigid plastics
Adjustable counter knives
for continuously sharp cuts
Large feed hopper
for voluminous parts, without material build-up
for minimized downtimes
Many drive options
for maximum throughput
for highest customer satisfaction
All from one source:
Machine, conveyor system, metal detection, support, spare and wear parts
The WEIMA show room is equipped with shredding and briquetting machines of all sizes and technologies. This enables us to simulate your application as realistically as possible. You have the possibility to send us your material or visit us directly in Ilsfeld. From our gallery you have the best view directly into the cutting chamber. So you can observe the shredding process live.
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