Since the current trend of the industry is to satisfy customer product requirements through blending and reactive compatibilization, the demand for mixing performance during the process has expanded. Currently, the material path for production of the engineering plastics in the polymer industry encompasses three steps: 1) Basic Resin Synthesis-Produces the base versions of a polymer (homopolymer), whether a commodity or an engineering polymer. The process is characterized, often by the large-scale mass production of the polymer and is usually done by major petrochemical companies like Exxon, Shell, Monsanto, etc. 2) Extrusion-Production of specific polymer with particular morphology and properties for final process (addition of fillers, colorants, and other minor components for specific applications). PVC, for example, requires up to 15 different additives to be blended into the basic polymer to produce the desired properties. Since this step requires extensive mixing and compounding, a machine like a co-rotating twin screw extruder would be used. An extrusion line with a 57 mm machine, with a capacity of 300 lb./hr., would cost over $500,000. 3) Injection Molding--The pellets are purchased from the compounder and then processed into the final part. Most of the technical emergencies a scientist working for a resin producer solves is for an injection molder, when their final product is not to specification.

This is an important concern for the injection molding industry due to the space restrictions and design limitations caused by the large size of the existing machines. The standard length to diameter ratio of the screw, L/D, for an injection molding machine is around 24. Our design can perform the same job in half of this length. One reason is the melting mechanism in the twin screw extruder typically occurs in half 1-2L/D (versus 6L/D for a twin screw extruder) and the mixing lengths can be less.What is required is a drive system that will turn both screws with sufficient torque to perform the various machine processes (like an extruder) and yet ram one of the screws to get the injection motion and the necessary pressures (like an injection molding machine). Traditionally, there are two main requirements that have to be satisfied in designing the gear box for a twin screw extrusion machine. The first issue is related to the limited distance between the two driving shafts, which restricts the diameters of the gears and in turn limits the amount of power that can be transferred to the screws.