Single-screw and Twin-screw extruders with mixing elements are widely used as a continuous mixing and production equipment of polymeric materials such as polymer alloys, blends, composites, etc. Melt mixing is one of the most important regions to determine the final morphology of materials, where polymers are completely melted and channel between screws and barrel is fully filled with materials so as to promote the intensive mixing. Various types of mixing elements have been empirically developed for objective materials. In recent ten years, computer simulation has been using to design of novel mixing elements according to the mixing mechanism such as distributive mixing and dispersive mixing. However it is considerably difficult how we should evaluate the performance of actual mixing in industrial applications using the simulation results due to the restriction of simulation.
In this manuscript, I would like to explain the basic theory of melt mixing and outline of numerical simulation technique. Then I introduce the representative evaluation methods of mixing performance proposed in previous studies. I also present the examples of studies about polymer blend and composite.

Injection molding simulation for rubber and elastomer is no longer limited to predicting the cavity filling while designing the part, or to answering questions regarding balanced filling. Based on an accurate simulation of the curing reaction (vulcanization), it can be used for designing the mold, identifying process windows and troubleshooting during production.

Introduce the simulation technology of the latest of extrusion machine for the polymer processing. The Flow analysis network (FAN) method is possible to analyze the extruder entire region based on the two dimensional calculation. The latest technology of the FAN method is applied to three dimensional field by a 2D-3D coupling technique. FEM and FVM analyses apply to prediction of detail screw mixing behavior by three dimensional calculation. Particle method is newly technology for polymer processing (high viscosity non-Newtonian fluid). Recently, DEM-MPS coupling analyze technique is developed and it shows qualitative prediction for polymer plasticization in the twin screw extruder.

The injection molds consume costs and time for manufacture. Therefore, it is important to predict the molding method. The CAE technology can analyze the resin flow in designed injection molds. This method is useful for checking the validity of a design. However, this technology cannot make the indication or the automatic correction of a point that improve design variables, such as the runner diameter, and the amount of resin, when fault arises in initial setting. Therefore, a design change must be made by the trial and error of the engineer.
In this research, the genetic algorithm (GA) is improved so that the multi-cavity molding of an injection molding can be automatically determined using the GA, which is one of the discrete optimization method.

Because of the light weight properties, formability and cost saving, plastics are essential materials for industrial products. In the automotive industry, many plastic parts are substituted for metal parts. Particularly in crash analysis of vehicle structure, capturing material failure is becoming important. This paper shows some issues in traditional material modeling and approach to enhance accuracy of crash analysis for unfilled plastics and fiber-reinforced plastics. The approach for unfilled plastics taking a new constitutive equation that takes unique properties of plastic into account. For the fiber-reinforced plastics, manufacturing process is considered to describe more accurate anisotropic material properties.