Plastics are used in a wide variety of products due to their relatively low manufacturing costs and flexibility of use. A popular method of plastic manufacturing is plastic extrusion. Plastic extrusion transforms raw plastic pieces or pellets into finished plastic sheets or molded shapes. The Society of Plastics Engineers (SPE) is a group of more than 20,000 plastic engineers. They have a specific division for Extrusion specialists and maintain a database of plastic-related information.
Plastic Pellets
The first step in the plastic extrusion process is the addition of unrefined plastic pellets into the extrusion machine. This is typically done with a conical holding device called a hopper that acts as a funnel for the plastic pellets. As more are needed, the pellets drain from the bottom of the hopper into the extrusion cylinder.
Melting & Mixing
As pellets are fed in from the hopper, they enter a horizontal cylinder. A screw-like shaft within the cylinder guides the pellets along the length of the cylinder. Heat is applied to the length of the cylinder, melting the plastic pellets into liquid form and mixing them together as they are moved down the cylinder.
Extrusion
Once the pellets have been thermally melted and mixed, the liquid plastic exits the cylinder and either enters a mold for shaping the melted plastic, or passes through a cooled dye to shape and solidify the finalized plastic. A die is a flat metal piece with a cutout of the intended shape for extrusion. Dies are commonly used for extruding pipes or other long pieces with a continuous shape.
Benefits
Plastic extrusion provides continuous creation for high-volume manufacturing. Extruded lengths of plastic can be cut down to specified lengths and dies can create intricate or custom shapes. Material thickness can accurately controlled by modifying die size, and finished products have little need for additional refinement or tooling.
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