Common Feeding Methods in PVC Plastic Extrusion Production Lines

For PVC plastic extrusion production lines, the choice of feeding method is closely related to the material's form (powder or granules). PVC processing often uses powder, which is heat-sensitive and prone to agglomeration; therefore, the feeding method needs special consideration to prevent bridging and ensure stable conveying.

Common feeding methods include the following: 

1. Spring feeder 

The spring feeder mainly consists of an inlet, outlet, spring, PPR hose, motor, and hopper. It is an energy-saving, low-noise, and reliable automatic conveying machine for powders and granules.

· Working Principle: This machine uses a screw conveyor principle. A rotating steel wire spring transports plastic powder from the storage bin to the hopper of the plastic molding machine until it is full. A level sensor signals that feeding has stopped. Feeding resumes when the level drops to a certain position, and the level sensor signals to resume feeding. 

· Key Feature: Quick disassembly and cleaning. Extruders frequently require color and material changes. The spring feeder, with only one spring inside, can be disassembled and cleaned in 5 minutes, eliminating bearings and dead corners.

· Pain Points: If the extruder requires forced metering, the spring feeder can only fill the hopper, making it impossible to precisely control the flow rate to the main unit. Furthermore, for commonly used high-filler powders in extruders (e.g., calcium carbonate, talc), the high-speed rotation of the spring can easily disperse and compact the powder, resulting in weak conveying. 

Conclusion: Suitable for small and medium-sized extruders and frequent material and color changes, but poor adaptability to pure powder or high proportion of fillers.

2. Screw feeder 

The screw feeder mainly consists of a drive unit, head section, intermediate section, tail section, head and tail bearings, and infeed/discharge devices. It is suitable for feeding powders and granules, and is appropriate for equipment with certain height requirements in various industries.

· Working Principle: Raw materials are poured into the screw conveyor's hopper. The switch is turned on, and the motor drives the screw shaft to rotate, which in turn propels the material to rotate. Under the friction between the material and the inner wall of the casing, the screw continuously lifts the material from the bottom of the hopper to the discharge port. 

· Key Features: High flow rate, anti-bridging. Many screw conveyors are equipped with a stirring and anti-bridging device at the bottom, specifically designed for handling extrusion fillers with poor flowability, such as talc, calcium carbonate, and wood flour.

· Pain Points: Extruders often require continuous production. Once the screw shaft seal wears, powder can enter the bearings, causing jamming and shutdown. Furthermore, if the extruder formulation contains glass fiber or long fibers, the screw blades are easily entangled.

Conclusion: Suitable for high-volume, low-flowability filler-modified materials, but bearing sealing is required; not suitable for glass fiber reinforced materials.

3. Vacuum feeder 

A vacuum feeder is a dust-free, closed-loop conveying device that uses vacuum suction to transport granular and powdery materials. 

· Working Principle: A vacuum feeder is a device that uses negative pressure airflow to automatically and in a closed system transport powdery or granular materials. It creates a vacuum inside, using the pressure difference to draw material from one place to another.

· Key Advantages: No residue, no dust. The area above the extruder hopper is completely enclosed, and no white powder is visible in the workshop. Furthermore, due to the flexible hose connection, it is ideal for scenarios where the extruder platform moves frequently or where a mixture of powder and granules is being transported.

· Pain Points: When the extruder capacity is high (e.g., above 2000 kg/h), the conveying efficiency of the vacuum feeder may not keep up with the screw conveyor. Additionally, if the extruder has a high proportion of recycled material (film edges, material lumps) and its shape is irregular, it can easily clog the vacuum lines.

Conclusion: Suitable for high-end products (food packaging materials, medical tubing), explosion-proof workshops, and scenarios requiring the suction of powdered materials or crushed scraps.

Summary of Extrusion Lines: How to Choose? 

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About Ningbo Superior Machinery

Established in 1992, SUPERIOR MACHINERY has been engaged in the rubber and plastic molding machinery industry for over 30 years. With an increasing market share, it has established itself in the fields of high-quality fully hardened screws and bimetallic barrels that are highly resistant to wear, corrosion, high pressure, and high speed. The company has a strong technical team composed of industry elites and professional consultants.

Since 2000, we have launched the Complete Machine Production Line, Dehumidification and Drying series, Material Conveying series, Hot and Cold Temperature Control series, Crushing and Recycling series, Material Mixing series, Automation Equipment, Molds, Accessories, and other products. We remain competitive in the market.

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