Plastic granulator machine is a crucial equipment in the plastic recycling and modification industry. The core working principle of plastic granulation machine can be summarized as: transforming plastic raw materials (virgin or recycled) into uniformly sized pellets through a continuous process involving heating, melting, homogenization, extrusion, cooling, and cutting.

Core Working Principle: Melting – Extrusion – Pelletizing

1. Feeding and Conveying

Plastic raw materials (which may be in the form of powder, flakes, recycled films, or scraps) enter the barrel through the hopper.

A rotating screw, acting like an auger, conveys these solid materials forward into the heating zone.

2. Heating and Melting

External Heating: Heating bands (electric heating) around the barrel externally heat the plastic.

Internal Shear Heat: More critically, as the screw rotates and the depth of the screw channels varies, the plastic material undergoes intense compression, shearing, and friction, generating significant internal frictional heat (viscous dissipation). These two heat sources work together to rapidly raise the temperature of the plastic to its melting point, gradually transforming it from a solid into a viscous molten state.

3. Compression, Homogenization, and Venting

Compression: The design of the screw compresses the volume of the molten plastic, gradually increasing the pressure to ensure the material is dense and can be extruded smoothly.

Mixing and Homogenization: In the mixing section of the screw, the melt is thoroughly blended and sheared to achieve uniform distribution of temperature, viscosity, and additives (such as color masterbatch or modifiers).

Venting (Optional): For materials containing moisture or volatiles (such as certain recycled plastics), the machine may include a venting section. Here, the barrel has openings connected to a vacuum pump. Under the combined action of the screw’s rapid agitation and the vacuum, moisture and gases within the melt are extracted to prevent bubbles from forming in the pellets.

4. Extrusion and Shaping

The fully plasticized, homogenized, and pressurized melt is continuously pushed forward by the screw through a multi-hole die at the end of the barrel. The die contains numerous small circular holes of uniform size. The melt is extruded through these holes, forming multiple continuous, elongated cylindrical plastic strands.

5. Cooling and Solidification

The extruded high-temperature plastic strands immediately enter a cooling system. The most common method is water cooling, where the strands pass through a water bath or are cooled by water spray. The purpose of cooling is to rapidly solidify and set the strands, maintaining their cylindrical shape for subsequent cutting.

6. Cutting and Collection

The solidified plastic strands are evenly drawn into the pelletizer (cutter head) by a haul-off unit. High-speed rotating blades cut the strands into pellets of predetermined length. The primary pelletizing methods include:

• Underwater Strand Pelletizing: Both cooling and cutting occur underwater. This method offers low noise and produces pellets with excellent shape.

• Air-Cooled Die-Face Hot Cutting: The melt is cut by rotating blades immediately upon exiting the die, and the pellets are then conveyed and cooled by air. This method is suitable for • thermoplastic pelletizing.

• Water-Ring Die-Face Hot Cutting: The cut pellets fall directly into a water ring for cooling. This method is well-suited for materials with lower viscosity.

The cut pellets then undergo dewatering and vibratory screening. Finally, dry and uniform plastic pellets are obtained, ready for packaging and storage.

Applications of Plastic Granulator:

1. Plastic Recycling and Regeneration: Reprocessing cleaned waste plastics (such as PET bottles, PE films, PP woven bags) into pellets to produce recycled plastic raw materials.

2. Plastic Modification: Adding fillers, toughening agents, flame retardants, etc., to virgin or recycled plastics, and thoroughly mixing and pelletizing them using a pelletizing machine to produce modified plastics.

3. Virgin Material Pelletizing: Synthetic resins (in powder or viscous form) produced by petrochemical plants need to be pelletized into granules. This facilitates transportation and subsequent processing (such as injection molding, blow molding).

Why Choose Purui Machinery:

With over 25+ years of expertise and a footprint in over 100 countries, Purui Machinery continues to lead the way in plastic regeneration.

Purui Machinery is a high-tech enterprise specializing in the R&D and manufacturing of plastic recycling machinery. Its product portfolio includes plastic pelletizing lines, washing lines, and crushing equipment. Purui is dedicated to providing global customers with the most efficient, reliable, and intelligent plastic regeneration systems.

Contact Us to Get Your Customized Recycling Solution:

E-mail: [email protected]

Tel / Whatsapp: +8617701563079

Partner with Purui Machinery - Turn your plastic waste into premium-grade sustainable profits.