February 12, 2025
Business

How Plastic Extrusion Works

  • September 26, 2024
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How Plastic Extrusion Works

Plastic extrusion involves the high-volume manufacturing of plastic films and sheets. Extruded parts are fabricated from different plastics to produce large or small solid-cored profiles. Here is how plastic extrusion works:

Tubing Extrusion

The tubing extrusion process produces pipes and long tubes. Extrusion equipment heats and melts plastic and pushes it into a die. The die shapes the molten plastic to form a square, round, or rectangular shape. Tubing produced from the process has uniform thickness and a consistent surface finish. Depending on its purpose, it can be flexible or rigid. Fabricators make rigid tubing from Polyvinyl chloride, polyethylene, and polycarbonate, while flexible tubing contains materials like silicone, polyurethane, and latex. 

Blow Film Extrusion

Professionals use blow film extrusion to create liners and plastic bags, which involve pushing molten polymer through a circular die. Different polyethylene grades serve as raw materials. During the initial process, the material cools before leaving the die but does not solidify completely. It goes through an additional expansion process by adjusting the tube’s height while filling it with air. The tube cools, and the material solidifies to create a bubble. Air volume and bubble size control the width and thickness of the film. A collapsing frame drops the film into a lay-flat form, and a machine winds the flattened film into reels, ready for cutting, printing, and finishing. 

Sheet Film Extrusion

This process produces sheets that are too thick for blowing. It uses single-type or blended plastic materials like PVC and polyethylene. Prepped materials go through a heating chamber and an extruder before the plastic is forced through a sheet die for shaping.

When sheets exit the die, they are cooled and rolled by structures that deliver the needed texture and sheet thickness. Experts use co-extrusion to achieve properties like UV absorption, soft touch, or grip. Along with an extruder and sheet die, a polishing stack supports the extrusion unit via sheet cooling and calibration calendars. Draw-rolls and the conveyor are located behind the polishing stack. Once the sheet reaches the conveyor, workers cut and store it. 

Over Jacket Extrusion

Over jacket type of plastic extrusion creates insulators for covering wires and other items. Raw materials used during the process include thermoplastic elastomers and polyethylene. During over jacket extrusion, the raw materials are combined and melted, and then the wire to be insulated is put through the center of the die. Experts use pressure tooling to create adhesion between the coating and wire, where molten plastic covers the wire and is pressurized when exiting the die. 

For cases that do not need adhesion, professionals use jacketing tooling. With jacketing tooling, the bare wire contacts the molten polymer after it leaves the die. In pressure tooling, the extruder is fitted with a retracted pin. The polymer contacts the retracted pin crosshead at a higher pressure for insulation.

Professional Plastic Extrusion

Plastic extrusion manufactures high-volume items like weather stripping, window frames, and thermoplastic coatings. The primary stages involve melting raw plastic materials, cooling, cutting, and winding. Contact a reputable rubber and plastics manufacturing company to learn about their services.

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