Car Precision Plastic Gear Injection Molding Process Parameters Optimization

As a deeper development of plastic, which is as an engineering material, metal gear has being replaced by plastic one in application of all standard gear, such as in the field of household equipment, industrial machinery, computer and electrical medical equipment, especially automotive. Compared with metal gear, plastic gear has advantages of lower costs, lighter weight and more flexible design. As a research object of typical injection molding product of precision gear—precision small module gear of PA66, and an evaluation index of fill rate and beat deviation, this paper studied on the impact of process parameters on complex thin-wall gear, obtained optimized scheme to improve the quality and provided a new way for process parameters of gear's injection molding. The main work is as follows:Firstly, fundamental equations of melt filling process, flow process and packing process were constructed based on injection mold flow simulation theory. The model was simplified by reasonable assumption with given boundary conditions. Those were solid theoretical foundations for numerically analyzing and solving.Secondly, simulation research of increasing gear fill rate, which was seemed as quality standard, was constructed to optimize process parameters by requirements of precision small module gear meshing and theory analysis of injection molding. Precision gear filling process of flow trend was simulated and orthogonal experiments of injection molding filling simulation were done by mold flow analysis software of Moldflow MPI6.1. The results of simulation, which predicted the impact of mold temperature, melt temperature, injection rate, holding pressure and time on product fill rate, was analyzed using the methods of S/N and target value. Then, the best process parameter combination of product filling was obtained and it's confirmed that the influence of holding pressure and melt temperature on product fill rate were the biggest.Finally, injection molding of precision small module gear of PA66 was studied under different process parameters and product fill rate was analyzed. Experimental results show that holding pressure and melt temperature have the greatest influence on gear molding quality, which would increase with them adding, but later the tendency of increase tends to be gentle. Through filling simulation study on precision small gear of PA66, combining with experimental study on injection molding, the best of optimized process parameters were obtained. The analysis of gear meshing experimental measure showed that the gear, which was molded under the best process parameter, had characteristics of smooth meshing, reliable quality and accuracy between level 7 and level 8.