Plastic is extruded by melting polymeric compounds, forced through a die opening, at the front end of the extruder, by way of a melt and transfer screw conveyance system.
The process begins by adding a specific raw material compound, as dictated by the job specifications, into a hopper located above the screw opening at the rear of the extruder. The screw, and barrel that contains the screw, are heated, and melt the polymer in a gradual staging process, as the screw moves the material forward toward the front of the extruder.
At the front of the extruder, the melted polymer is forced through an opening in the shape of the part that is designated to be produced. It could be a profile shape, a rod, or a tube. Once it exits the face of the machine, the melted material is guided into a tool designed to set the material up into the shape of the finished part. The sizing tooling then forms the part into the shape and size required by the part specifications.
Since the extrusion is a fluid melt process, the size and shape of the part being extruded, is controlled by both the tooling, and extruder operator, who must oversee the heat temperatures and control parameters. The operator must control conditions for both the melt, as well as the cooling in the downstream portion of the process. A takeoff unit is required at the end of each extrusion line. The takeoff pulls tension on the extrudate as it exits the extruder, and essentially is what controls the line speed and to some degree, the part size, as it pulls tension on the part and maintains stability during the course of the run.
At the end of the extrusion line, the parts are then either cut to a specific length, or coiled or put up on spools, depending on the length of the part requirement, and the flexibility or rigidity of the material.
The finished parts are then packaged up into the appropriate packaging containers as specified for the product. These include boxes, bundles, or bulk put ups, which are then shipped to the customer once complete.