The Plastic Extrusion Process

Apr 29, 2021

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The Plastic Extrusion Process

Plastic extrusion profile is the process of converting plastic materials from solid to liquid and recombining them into finished products. First, the plastic particles are fed from the hopper to the jacketed screw by gravity. As the screw rotates around its axis, it transports, melts and pressurizes the plastic. From there, the molten material is forced through a mold to form a specific cross section, producing parts that may have a wide range of lengths. In the extrusion process, the plastic changes from solid to liquid and then back, without sacrificing its unique properties. Therefore, the waste parts can be ground and re extruded to minimize degradation, which makes extrusion a popular method to reduce or recycle plastic waste.

Extrusion Dies

The final design of the plastic extrusion profile is carried out in the mold. The plastic enters the front flange of the die from the metering part, and the front flange is fixed at the end of the extruder barrel with bolts. It flows around a metal separation tool, or “mandrel,” suspended in the center of the channel. At the back of the mandrel, there is a pin and a ground for sizing the product. The pins and rings are detachable, making it relatively easy to reconfigure the mold or replace worn parts.

Pressurized air is introduced into a bracket of the mandrel and discharged from the die pin. This airflow prevents the product from collapsing as it leaves the mold. After that, the component performs post-processing.

Cooling and Sizing Equipment

As the plastic extrusion profile product leaves the mold, it enters a vacuum chamber where it is pulled through the sizing ring. The combination of vacuum stretching and air pressure forces the plastic to conform to the shape of the ring. If the sizing ring is worn, longitudinal scratches will be left on the product. The vacuum chamber is filled with water to cool the plastic into a hard solid. The cooled product is pulled by a slide with a drive belt, and is cut into a certain length or rolled into a spool.