| Injection molding is an important molding method in plastic processing. However there are always many defects in the molding producing process. Specially, the major defects for the large-scale plastics such as automobile, instrument panel with the characteristic of long strip and large curved face are warp, sink mark and weld lines. How to reduce the defects is must be faced problem for engineers. These defects are solved only relying on experience, skills and trials on the factory practice. The injection mould CAE can analyze and simulate the molding process in computer and forecast the disadvantages of the design before the injection moulds are made. This changes the traditional way that depends on experience and intuition to test and modify mould over and over.Aiming at the sink marks problem of an automobile bumper, based on summary of the cause and control methods of sink marks, this paper create the finite element model by Moldflow software, and carry through the simulation of injection molding procedures. According to the result of numerical simulation, improved running system is proposed. Through comparing the important simulating results about the weld lines, warpage deformation, sink marks, the best gating is received.Then the impacts of different processing parameters on sink marks are researched using Taguchi experiment design and numerical simulation. The result show that melt temperature, mold temperature, injection time, packing pressure, cool time have the most significant effect on sink marks. The non-liner relationship between main processing parameters and sink marks is set up by response surface technology. The optimization of processing parameters is achieved by genetic algorithm optimized.Finally, practice experience is carried out using this paper gained gating system and processing parameters. The product has no sink mark, which proved CAE analysis and optimization feasible and reasonable.
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