An extruder gearbox drives a screw or auger. This screw – in turn – is used to convey plastic. As the plastic is moved through the process it arrives at a heated section, which takes the plastic from its solid state, into a molten liquid, and onto a die.A gearbox in a plastic extruder serves multiple crucial functions: Speed Regulation: Plastic extrusion processes often require precise control over the rate at which the plastic material is pushed through the extruder. Gearboxes allow for speed regulation by adjusting the rotational speed of the extruder's screw.