Top Selling two color household mold Traders:Injection molding is the first to add plastic to the heating cylinder of the injection molding machine, and then heat the plastic to melt. The injection mold is driven by the screw or plunger of the injection machine and injected into the mold cavity through the nozzle and injection molding system. Due to physical and chemical effects, injection molds harden and shape. Injection molding is a cyclic process consisting of injection molding, pressure retention (cooling) and plastic release processes.