Numerical study of surface tension and gravitational effects on mold filling.

The filling process of injection molding in various planar gaps and center-gated disks are analyzed numerically. Comprehensive mathematical models are developed for flows in planar gaps and center-gated disks. An incompressible Newtonian fluid with creeping velocity is assumed in the present study. Also assumed is that the fluid viscosity is a function of temperature only.Because the fountain flow effect plays an important role on the molecular orientation, the related effects of gravitational force, surface tension, and non-isothermal conditions on the fountain flow are systematically analyzed for flow injection through various mold geometries and orientations. Additionally, in order to seek a complete and general understanding of the flow fields involved, all the variables presented are non-dimensionalized. The results of negligible surface tension and gravitational effects are compared with previous studies and have well agreement.The transient development of flow front, required injection pressure in the inlet and velocity and temperature distributions have been obtained for different molding conditions. These results provide the important information for the design of the new molding process, such as the construction of mold, exit gate design, choice of material, heat transfer design and so on