Reduction of sink marks in wire insert molded parts

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Phadke, Gauri
Engineering Mechanics
thesis / dissertation description
Integrating the huge wiring harness network with the plastic trim components found in the car is an attractive way to reduce the vehicle weight. When any foreign object is inserted in an injection molded part, the change in polymer cross section leads to sink marks which are aesthetic defects and are not acceptable for plastic trim components. In this thesis, a method to minimize or eliminate sink marks for wire insert molded component using injection molding process is presented. L9 Taguchi DOE experimental framework has been employed to study the effect of process parameters, part rib geometry, and the presence of wire itself on the sink mark formation. Sink depth is defined as the excess deflection in the surface profile which can be felt to hand. A descriptive simulation study is presented where process parameters namely, the mold temperature, the melt temperature, and the pack time are varied on different sets of rib geometry to observe the depth of a sink mark. The simulation results indicate that high mold temperature effectively minimizes the sink depth for all the rib geometries whereas the influence of melt temperature and pack time depends on the particular rib geometry. The results also testify that a proper combination of rib geometry and process parameters eliminates the sink mark.