A PARAMETRIC STUDY OF SINK MARKS IN INJECTION-MOLDED PLASTIC PARTS USING THE FINITE-ELEMENT METHOD

A numerical procedure to simulate the formation of a sink mark-near th e base of a iib in an injection-molded plastic part has been developed . This method uses two commercially available software packages, C-Mol d and Abaqus, to model the injection molding process. The C-Mold softw are uses a generalized Hele-Shaw formulation to simulate the mold fill ing, packing and cooling stages of injection molding. From this analys is, pressure and temperature histories in the rib area are derived The se are used to determine the initial conditions and boundary condition s for a sequentially-coupled thermal/structural finite element analysi s of a cross-section of the rib, using the Abaqus software. An elastic -plastic material model with temperature-dependent material properties is employed. The thermal/structural finite element analysis provides an accurate model of the two-dimensional cooling and shrinkage behavio r of the part during molding. To verify the accuracy of the method the dependence of sink mark depth on various geometric and molding parame ters has been analyzed. The predicted sink mark depth is found to be i n good agreement with experimental results from the literature.