Working principle and process of waste plastic granulator

The waste plastic granulator converts waste plastic into reusable particles through processes such as crushing, melting, extrusion, and cutting. The core is to use screws to plasticize and homogenize the plastic under high temperature and pressure.

This type of equipment uses an extruder as the main machine, combined with auxiliary systems to complete the entire process from waste to regenerated particles. The entire process not only achieves resource recycling, but also has the characteristics of high automation, low energy consumption, and strong adaptability. It is widely used in the recycling and regeneration of various waste plastics such as PE, PP, PVC, PET, etc.

1、 Core working principles and processes

Raw material pretreatment (crushing and cleaning)

Waste plastics such as films, woven bags, bottles, etc. need to be crushed into small pieces by a crusher and cleaned to remove impurities such as mud, labels, and oil stains. After cleaning, it can directly enter the granulation process without complete drying, achieving "wet dry dual-use".

Automatic feeding and conveying

The crushed material is fed into the extruder hopper through a screw feeder or belt conveyor system, achieving continuous and automated feeding and reducing manual intervention.

Heating, melting, and plasticizing

After entering the extruder, the material moves forward under the push of the screw. At the same time, the external heating coil and internal frictional heat work together to gradually heat up the plastic and undergo a transition from glassy state to high elastic state to viscous flow state, ultimately melting completely.

Heating method: Electric heating is the main method, and some large units use thermal oil or steam heating;

Temperature control: Partition PID temperature control, with an accuracy of ± 1 ℃, ensuring uniform melting.

High pressure extrusion and filtration purification

Molten plastic is pushed under high pressure by a screw through a porous filter plate and a screen changer to filter out unmelted impurities, carbides, and metal particles. The exhaust extruder can also discharge moisture and volatile gases through the vacuum port to prevent the generation of bubble particles.

Forming and cutting

The molten material is extruded from the die into strips (granulation by pulling) or filaments (water ring/underwater cutting), and after cooling, it is cut into uniform particles by a high-speed rotating cutter:

Strip cold cutting: suitable for small and medium-sized units, low cost;

Underwater hot cutting: fast cooling, round particles, suitable for PE/PP and other easily adhesive materials.

Cooling and collection

After being air-cooled or centrifugally dehydrated, the cut particles are transported by a conveyor belt to the storage bin, completing the entire granulation process.