What are the process steps involved in the production equipment of plastic recycling machines?

What are the process steps involved in the production equipment of plastic recycling machines?

The process flow of the plastic recycling machine equipment mainly includes six core steps: crushing, cleaning, dewatering, melt extrusion, pelletizing, and packaging. It converts waste plastics into reusable recycled particles through physical means.

1. Crushing/Milling: Feed the large pieces of recycled waste plastics (such as beverage bottles, plastic buckets, films, etc.) into a crusher and use high-speed rotating blades to cut them into small fragments of 10–30mm. This step facilitates subsequent cleaning and uniform melting. The blades are usually made of high-strength alloy steel, and the rotational speed is controlled at 300–600 rpm to ensure uniform particle size.

II. Cleaning and sorting: Broken plastic fragments contain impurities such as label adhesives, oil stains, and sediment, which need to be processed through a multi-stage cleaning system:

Hot water pre-washing (50–60°C): softens adhering substances; Friction cleaning: removes contaminants through the shear force between water flow and particles; Rinsing and flotation: separates different types of plastics using density differences (for example, polypropylene (PP) floats on the surface, while polyvinyl chloride (PVC) sinks to the bottom); Automatic sorting: some production lines are equipped with near-infrared spectroscopy (NIR) sorting equipment, which can identify and separate materials such as PET, HDPE, PP, with an accuracy rate of over 95%.

After undergoing three-stage treatment (including sedimentation, air flotation, and activated carbon adsorption), the cleaning wastewater is recycled. The water consumption per ton of water can be controlled within 1.2 tons.

III. The fragments, after undergoing dehydration and cleaning, have a relatively high moisture content. Before entering a hot-air dryer or a dehumidifying dryer to remove the internal moisture, a centrifugal dehydrator should be used to reduce the moisture content to ≤3%. Insufficient drying can lead to the formation of bubbles during the melting process, affecting the quality of the particles.

4. After melting, extrusion, plasticization, and drying, the plastic fragments are fed into the extruder and melted at a high temperature ranging from 180-280℃. The screw adopts a gradual compression ratio design (2.8:1 to 4.2:1) to ensure uniform heating of the material and avoid degradation. The melt passes through a metal detector (sensitivity Φ0.3mm) and a high-precision filter screen (20-60 microns) to filter out impurities.

5. Extrusion molding and granulation: Molten plastic is extruded through a mold into strips, or directly thermally cut on the mold surface

Thread granulation: After extrusion, the thread is cooled in a water tank and then cut into cylindrical particles by a granulator; Underwater granulation: When the melt is extruded from the die, it is instantly cut and cooled by rotating blades, resulting in more regular particles and improved efficiency.

The particle size tolerance is controlled at ±0.15 millimeters, and the fluctuation of the melt flow rate (MFR) does not exceed ±8% of the nominal value.

VI. Cooling and Packaging: The cut particles are screened through a vibrating screen to remove particles that are too long, stuck together, or contain impurities. Qualified products enter the cooling silo for further cooling, and are finally weighed and packaged into finished products in ton bags or small bags, which are sold as recycled raw materials.

Common thermoplastics in daily life, such as PET, HDPE, PP, PE, and PVC, are all recyclable. Among them, mineral water bottles (PET), personal care product bottles (HDPE), and microwave lunch boxes (PP) are the categories with the highest recycling rates.

Longjun Machinery produces various equipment such as plastic recycling machines, plastic granulators, granulation crushers, plastic granule machines, automatic feeding machines, forced feeding machines, dewatering and lifting machines, vibrating screens, pelletizers, stainless steel silos, ribbon mixers, vertical mixers, plastic granulator screw barrels, electromagnetic vacuum screen burners, flue gas treatment equipment, and more