Plastic resin can be converted into any shape with engineering skills and technical knowledge. Plastic comes in different shapes, colors and designs, and its application is widespread in homes and different industries. Plastic extruder machines have unique features and they widely used by industries for shaping products using plastic extrusion process. Plastic extrusion is a manufacturing process wherein large volume of raw plastics are melted and shaped into a continuous profile, producing fencing, plastic sheeting, wire insulation, thermoplastic coatings, plastic films, pipe or tubing, deck railings, weather-stripping, and many more.
The process of plastic extrusion begins by feeding plastic materials such as powders, pellets, granules or flakes from a hopper into the extruder machine’s barrel. It is gradually melted using mechanical energy that is generated by heaters arranged across the barrel and turning screws, and the molten polymer is forced into the die, that shapes the polymer into pipes hardening during cooling. Plastic extruder machines consist of barrel, feed screw and temperature controller, and the design and features depend on several factors such as the type of material to be extruded and the product design. A plastic extruder machine has thermoplastic screws namely the feed, melting, metering, decompression and second metering zones. The feed zone is also known as the solids conveying zone wherein the resin is fed into the extruder, with the same channel depth all throughout the zone. Melting, transition or compression zone has progressively smaller channel depth where the plastic polymer is melted. The metering or melt conveying zone of an extruder machine has a constant channel depth and it is the zone melting the last particles, mixed to a uniform composition and temperature. Decompression zone where the channels gets suddenly deeper, relieving pressure and allowing trapped gases to be drawn out by vacuum. Second serves to repressurize the molten polymer to get it through the screen and die resistance, and metering zone is similar to first metering zone, with greater channel depth.
Die types include blown film extrusion, sheet film extrusion, tubing extrusion, overjacketing extrusion, coextrusion and extrusion coating. Plastic films like shopping bags use blown film that involves annular, spider and spiral plastic extrusion processes. Sheet or film extrusion involves extruding plastics that are too thick to be blown using either T-shaped or coat hanger. Tubing extrusion is used for manufacturing PVC pipes wherein positive pressure is applied in the internal cavities using a pin, and negative pressure is applied using a vacuum sizer outside the diameter to make sure the final dimensions are correct. For more information check out our website.On Plastics: My Thoughts Explained