Numerical and experimental investigation of non-Newtonian high viscosity flow field in multi materials extrusion process

The stresses induced in the rubber by pressure loss and unbalanced velocities at exit is the main factor that affect the swelling of rubber cross-section after exiting the die. In this research, the effect of velocity distribution at the die exit on the rubber dimensions is experimentally and numerically studied with the aid of finite volume method. Three-dimensional simulation of non-Newtonian high-viscosity flow was performed to predict the distribution of velocity and pressure in the die channels. This can eliminates the experimental trial and error procedure for modifying the shape of channels to achieve a uniform velocity distribution and reduction of pressure loss. According to the importance of recognition of the soft and hard materials boundaries in multi-material cross-sections, the two-phase VOF method is employed. A comparison between primary and modified dies shows more precise dimensions of the modified die. The results show that in the narrow portions of the profile in the vicinity of wide regions, because of the impossibility of achieving a uniform velocity distribution, the produced cross-section is smaller than the design value. By the employed numerical method reduces the pressure loss in the modified die by 40% in comparison with that of the primary designed die.