| The clamping system is an important part of an injection molding machine, and whether its performance is good or not will directly affect the quality of molded products.Therefore, how to effectively improve the performance of clamping mechanism becomes a major issue to be solved by the research workers of injection molding machines. For a long time, however, manufacturers of injection molding machines in China generally adopt experience analogy design method in the design of clamping mechanisms, as it is difficult to meet the design requirements. Yet, the advanced optimization-design theory and computer technology open up good prospects for the development and design of high-performance clamping mechanism.This paper conducted research with the using performances of the five-point double-toggle clamping mechanism as objectives. The NSGAⅡ based on MATLAB programming was mainly applied to carry out a multi-objective optimization design with the ratio of force amplification and the stability of moving-platen speed of the clamping mechanism as the optimization objectives. And considering the friction of hinge holes, the Torelance Model Method was used to conduct robust-optimization design for the ratio of force amplification. The paper includes the following aspects:(1) Accoding a detailed analysis of the domestic and international optimization research on clamping mechanisms of injection molding machines, proposed the research direction of this topic.(2) After researching on the working principle and working condition of the clamping mechanism, its kinematic schematic diagram was depicted, the geometry and kinematics theory was applied to analyze the diagram to get the mathematical relations between the design parameters (dimentional parameters and positional parameters) and its motion characteristics and clamping characteristics.(3) Establishing PROE3D solid model of the clamping mechanism, united ADAMS to carry out kinematic simulation analysis and built a simplified parametric model with ADAMS, finilly, this parametric model was used to analyze the reliability of the mathematical equations of the clamping mechanism. (4) Taking the ratio of force amplification and the smoothness of the moving-platen speed of the clamping mechanism as optimization objectives, through sensitivity analysis method to determine significant factors from various parameters affecting the objective functions as design variables, considering various constraints in the mold opening and closing process, the mathematical model of the clamping system was established. Then programming by MATLAB with the NSGAⅡ to optimize, obtained the Pareto front of optimization goals, and selected an appropriate solution from the Pareto front as the optimal solution, finally, through the comparison of the optimization results between MATLAB and ADAMS showed that the ratio of force amplification had increased, and the smoothness of motion of the moving platen improved well, which provided a theoretical guidance for rational design of the clamping mechanism.(5) In the case of considering friction factors of instability, the Torelance Model Method was applied to transform the robust-optimization problem of the ratio of force amplification into a multi-objective optimization problem, that was not only maximizing the ratio of force amplification, but also minimizing the fluctuation of it, then the NSGAⅡ was adopted to optimize, and the optimization results were compared with GECM. The results showed that the NSGA Ⅱ could be easily and effectively used to solve multi-objective optimization problem with constraints, this conclusion provided an important reference method for robust optimization design. |
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