Or, in other words, plastic resin granules are heated and melted, then mixed and formed into pipe. Pipe is not the only product produced by the extrusion process. Plastic tube, sheet, wire and profile shapes are all also manufactured by this process. In fact, the plastic resin granules or pellets used for injection molding are produced by extrusion. A long strand or filament of extruded plastic is chopped or cut into pellet-sized pieces to produce plastic injection molding materials.
Extrusion produces an inherently strong finished product.
More so than a molding process. This is one of the reasons that plastic pipe is rated at higher pressures than injection molded plastic fittings. 2 Injection Molding W hen people talk about molding, they're usually referring to injection molding. This is the manufacturing process that is used to produce the plastic parts that valves are manufactured from, as well as plastic pipe fittings. An injection molding machine uses heat to melt plastic pellets.