Numerical simulation of cavity roughness effects on melt filling in microinjection molding

In microinjection molding, when dimensions of molded parts, and thus the cavity are small, cavity roughness may become significant for the filling of polymer melt. In this paper, cavity roughness effects on filling polymer melt flow into a thin circular cavity were investigated numerically with the aid of a newly developed inlet‐velocity iterative procedure. The roughness effects for different mold and melt temperatures, cavity thicknesses, and injection rates were investigated. The trends predicted by the numerical simulation are in good agreement with those obtained from the experiment. When the surface roughness approaches a significant portion (e.g., 10%) of the cavity thickness, the effect of surface roughness becomes extremely pronounced especially at lower mold temperatures and injection velocities.