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      Shredding and recycling of plastic lumps and purgings

      Information on proper recycling

      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.


      Call it what you want, we make it small.

      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.

      Contaminated start-up lump

      Massive plastic lump

      WEIMA WLK 10 shredder for plastic lumps in production line

      Compact WLK 10 lumps shredder


      How are plastic lumps formed?

      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.

      Various plastics

      Mixed petrochemical lumps

      Various plastic lumps

      Stack start-up lumps before shredding

      Stacked extrusion lumps

      Production waste from plastic barrel production

      Plastic bin production waste


      Large, voluminous, heavy and bulky – by no means worthless

      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.

      Giant white start-up lumps on a pile

      Storage of petrochemical lumps


      What are thermoplastics?

      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).

      Source: Ruge, Wohlfahrt (2013) Technologie der Werkstoffe


      Did you know?
      The forefather of thermoplastics is celluloid. It has been known and produced the longest.

      Source: Ruge, Wohlfahrt (2013) Technologie der Werkstoffe

      Applications from industrial plastics production


      WLK 4: The entry to plastics recycling

      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.

      To the WLK 4

      WEIMA single-shaft WLK 4 for plastic waste

      WEIMA WLK 4


      WLK series: High throughput plastic shredders

      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.

      To WEIMA WLK 1500

      x-ray image of the WEIMA WLK 1500 single-shaft shredder

      WEIMA WLK 1500 interior view


      WEIMA WLK 800 shreds PE injection moulding waste


      WKS series: Maintenance-friendly all-rounders with swing ram

      With the WKS 1400-2200 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.

      To WKS 1800

      x-ray view of the WEIMA WKS single-shaft shredder

      WEIMA WKS shredder interior view


      WEIMA WKS 1800 single-shaft shredder with Hägglunds hydraulic drive shreds petrochemical lumps


      WLK Super Jumbo series: For extreme throughput requirements

      With their extremely sturdy design and large rotor diameters of up to 700 mm, shredders of the WLK Jumbo and Super Jumbo 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.

      To the WLK Super Jumbo

      WEIMA WLK 25 Super Jumbo single-shaft shredder

      WLK 25 Super Jumbo


      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.

      Two-stage plastic shredding with shredder and granulator

      Two-stage plastic shredding with shredder and granulator


      Precise cut at high throughput with profiled V-rotor

      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.

      Profiled V-Rotor from WEIMA

      Profiled V-Rotor with counter knives


      Heavy duty machine design

      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.

      PreCut shredder rotor vautid protection

      Vautid rotor protection

      Vautid wear ptrotection

      Vautid weld-on for shredder rotor

      Vautid shell on PowerLine rotor

      Vautid rotor wear protection

      Vautid rotor shell

      Vautid rotor coating

      ANti-wear ptotection with vautid coating

      WEIMA WKS rotor vautid shell

      Wear protection vautid rotor shell

      Vautid coating for pre-shredder


      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


      Electromechanical drive

      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.

      Power belt drive with WEIMA gearbox

      Electromechanical drive with WEIMA WAP gear

      Power belt drive with WEIMA gearbox

      Electromechanical drive with WEIMA WAP gear

      Power belt drive with WEIMA gearbox

      Electromechanical drive with WEIMA WAP gear

      Shredder with power belt drive

      WLK Jumbo with electromechanical drive


      High-torque drive

      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.

      High-torque drive from Baumüller

      High-torque drive from Baumüller

      Hägglunds hydraulic drive on a WEIMA single-shaft shredder

      Hägglunds hydraulic drive in action

      Hägglunds hydraulic drive on WEIMA FineCut

      Hägglunds hydraulic drive on WEIMA FineCut

      Hägglunds Hydraulic Drive System on WEIMA PreCut shredder

      Powerful hydraulic drive from Hägglunds on a WEIMA PreCut Shredder

      Opened inspection flap on the back of the WEIMA PowerLine shredder next to the Hägglunds Bosch Rexroth hydraulic drive

      Inspection flap of a WEIMA PowerLine shredder

      Hägglunds hydraulic drive on WEIMA PowerLine 3000

      Hägglunds hydraulic drive on WEIMA PowerLine 3000


      Hydraulic drive

      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.


      Only at WEIMA

      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

      Easy maintenance
      for minimized downtimes

      Many drive options
      for maximum throughput

      Fast service
      for highest customer satisfaction

      All from one source:
      Machine, conveyor system, metal detection, support, spare and wear parts


      See for yourself

      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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      Granulate of laminate from the cutting mill

      Material test plastic granulate