The PVC pelletizing process involves raw material preparation, metered feeding, extrusion, melt filtration, die-face cutting, cooling, screening, and pellet collection. Each stage contributes to consistent pellet quality and stable production.
The equipment configuration described here includes a 200 L high-speed mixer, a 500-type screw feeder, a twin-screw metering feeder, a 65 model twin-screw extruder, a φ150 single-screw extruder, a hydraulic plate-type automatic screen changer, an air-cooled die-face hot-cut pelletizing unit, cyclone separators, an air-cooled vibrating screen, and an air-conveying storage silo.
Raw Material Preparation and Initial Mixing
Raw materials and additives are weighed and proportioned according to the formulation. The prepared ingredients are then gradually fed into a 200 L high-speed mixer for initial blending.
Uniform mixing helps distribute the PVC resin and additives before extrusion. The formulation may include processing aids, stabilizers, lubricants, fillers, and other ingredients, depending on the intended application.
For PVC compounds, the formulation and processing conditions must be selected to maintain thermal stability during subsequent extrusion.
Material Conveying and Metered Feeding
After initial mixing, the blended material is conveyed by a 500-type screw feeder to the twin-screw metering feeder.
The metering feeder controls the material feed rate to the extruder. A consistent feed helps maintain stable throughput and reduces fluctuations in the extrusion process.
The conveying and feeding systems should be configured to handle the material's flow characteristics and the required production rate.
Plasticization and Extrusion
The prepared mixture enters the 65 model twin-screw extruder, where the screws convey, mix, and plasticize the material under controlled heating conditions.
The screw configuration and barrel temperature profile affect material conveying, plasticization, and melt uniformity. Because PVC is sensitive to excessive heat and prolonged residence time, the temperature settings and screw speed must be matched to the formulation.
Stable processing conditions help reduce the risk of material degradation and support consistent output.
Melt Filtration
According to the specified line configuration, the processed material is transferred through a φ150 single-screw extruder and then passes through an integrated hydraulic plate-type automatic screen changer.
The screen changer removes solid contaminants and other retained particles from the material stream. As the filter screen accumulates contaminants, the pressure drop across the screen may increase. The automatic screen-changing mechanism allows a contaminated screen to be replaced according to the equipment design, helping reduce production interruptions.
The actual connection between the twin-screw extruder, the φ150 single-screw extruder, and the screen changer should be confirmed against the manufacturer's process flow diagram. This arrangement is specific to the described line rather than a standard requirement for every PVC pelletizing system.
Air-Cooled Die-Face Hot-Cut Pelletizing
After filtration, the material passes through the die and is cut by rotating blades at the die face. This process produces pellets directly at the die outlet.
The air-cooled die-face hot-cut pelletizing unit helps cool the newly formed pellets as they are conveyed away from the cutting area. Pellet size and shape depend on the die openings, cutting speed, melt flow, and operating conditions.
Stable extrusion and consistent cutting conditions help maintain uniform pellet dimensions.
Primary Cyclone Separation
The pellets are conveyed to the primary cyclone separator, where the pellet stream is separated from the conveying air.
Depending on the system design, the cyclone may also collect entrained fines. It should not be treated as a substitute for a vibrating screen when the objective is to classify pellets by size or remove oversized particles.
Effective separation helps transfer the pellets to the next stage while managing the conveying airflow.
Secondary Screening and Separation
The pellets pass through an air-cooled vibrating screen for further classification. The screen separates particles according to size and can remove undersized fines and oversized or irregular pellets.
The screening specifications should match the required pellet dimensions and product quality standards.
After screening, the pellets enter the secondary cyclone separator for the next separation and collection stage. The precise function of this unit depends on the downstream conveying arrangement and the design of the separation system.
Pneumatic Conveying and Storage
After separation and screening, conforming pellets are conveyed by an air-blowing system into the storage silo.
The silo provides temporary storage before subsequent packaging or transfer. The conveying system should be configured to limit pellet damage and excessive dust generation during transport.
Finished pellet quality depends on the performance of the entire line, including raw material preparation, extrusion stability, filtration, cutting, cooling, screening, and collection.
Custom Machining for Industrial Equipment
Beyond plastic pelletizing equipment, Hansheng Automation provides custom precision machining for non-standard industrial components according to customer-supplied drawings. Our services also cover parts for filling machinery and tobacco packaging equipment, precision components for yacht equipment, and parts for remote control racing cars. Each component is manufactured according to the specified dimensions, structural requirements, and drawing details.
