The importance of plastic granulators in plastic processing industry cannot be emphasized enough. They are used to break down plastic products such as crates, drums, plastic bottles into “regrinds” or “flakes” (small uniform pieces). These grinds are then sorted, separated, washed and pelletized before reprocessing.
A granulator has cutting knives mounted on a rotor, which spins at high speed and is powered by an electric motor. This rotor is positioned in a cutting chamber where stationary knives are affixed. When plastic scrap comes in contact with the stationary knives, they get shredded to small pieces. Users can adjust the size of the holes to achieve the desired cut shreds.
Most plastic granulators work on the same basic concept but manufacturers offer plastic granulators in different chamber designs and knife arrangements. Featured below are three types of granulators that are widely used in the plastic processing industry.
- Double Scissor Cut or Double Angle Cut:
This type of granulator includes straight rotor knives which are arranged in parallel with the slight angle. The degree of angle can vary from being slightly slanted to completely horizontal. The stationary knives are also aligned in parallel but in the direction opposite to the rotor blades. Manufacturers prefer using Double Scissor Cut as its open design provide “true scissor” cuts with greater precision.
- V-type Rotor or Chevron:
In Chevron granulators, knives are arranged in V-shape and mounted in parallel to one another. The cutting edge is on the inside of the V-shape while stationary knives are mostly straight or in the V shape. This help cut the plastic along two edges starting from the outside to the inside. Chevron granulators are long-lasting and suited for injection or extrusion of plastic scrap.
- Helical Rotor
In the Helical Rotor, knives are aligned in a spiral or helical design. This type of granulator is robust, durable and can withstand higher impact load. They are perfect for shredding thick cross-components.
Though granulators are built to last long, it is essential to keep them well-maintained to avoid costly repairs in the future. Rotor knives and stationary knives should be routinely sharpened to ensure maximum granulation efficiency. The granulator screen should be inspected to check if they are not clogged. Also, the jammed motor should be fixed in time otherwise it can cause the electric motor to burn up.