Structural Topology Optimization Of Ram Component In Gantry Machining Center

The technology of high-end numerical control machinery and robotics is one of the key sectors in the "Made in China 2025".In order to further improve the performance of machine tools,innovative design methods must be adopted in the design of structural parts.As one of the most promising frontier technologies for computer aided optimization,topology optimization can greatly improve the efficiency and quality of structural design.In this paper,topology optimization technology was used to design the machine tool components innovatively.With the development of CNC machine tools moving toward high precision and high speed,new requirements are placed on the stiffness and quality of moving parts of machine tools.The gantry machining center is an important type of CNC machine tool,whose ram directly affects the performance of the whole machine.In terms of structure,the stiffness of the ram affects the cutting ability,efficiency and machining accuracy of the machine.In the numerical control motion,the quality of the ram has a great influence on the accuracy of the trajectory control,especially in high-speed cutting,where the concept of acceleration design requires continuous reduction of the quality of moving parts.Based on analyzing and summarizing relevant domestic and overseas researches,computer aided optimization technology in this thesis is taken as a way with the core of analysis,optimization,synthesis,quantification and dynamics to reduce the quality of the ram and improve its stiffness and low natural frequency based on the topology optimization theory of continuum structure.In addition,a composite optimization design method for machine tool structure was proposed,which is multi-objective size design after comprehensive objective topology optimization.The main works are as follows:(1)The structural topology optimization method and the structural design based on response surface method were introduced.The mathematical model,topology optimization of continuum structure based on SIMP,was discussed.The method of optimization problem in the paper was clarified.(2)The static and dynamic performance analysis was carried out to obtain the performance parameters under the condition of extreme processing position and the condition of typical machining position after building the finite element model of the ram component.(3)A topology optimization model of ram component based on finite element model is built.Compromise programming method was adopted to define objectives of multi-stiffness topology optimization.Mean frequency method was adopted to settle eigenfrequencies of free vibration optimization.The volume fraction constraints was defined by target mass of the ram.The topology optimization of objective maximization was performed respectively.Based on former mentioned methods,the comprehensive objective topology optimization function was defined.The optimal constraint value was selected by comparing the parameters of the topology results under different volume fraction constraints to obtain the topology structure that simultaneously satisfies the static and dynamic performance objectives.According to the results above,the ram model of typical shape ribs based on topological features was obtained by using the method of reverse-engineering reconstruction.(4)The key dimensions,affecting a lot on the performance of parametric reconfiguration model,were selected from the design principles of typical hazardous working conditions.HyperStudy was used to solve Pareto optimal solution of critical dimensions by multi-objective genetic algorithm based on the response surface method.In the end,the new design modeling,static and dynamic performance analysis were completed.By means of comprehensive objective topology optimization and multi-objective dimension design based on response surface,the mass of the optimized ram decreased by 16.46%,and the static stiffness and low-order inherent frequencies were increased by 24.37% and 16.78% respectively.Evaluate by specific stiffness structural efficiency(SSSE),The numeric value of the static SSSE of the optimized ram is increased by 96.70%,and the numeric value of the dynamic one is increased by 37.79%.As a good result,it provides a theoretical reference and relevant basis for the structural optimization design of other machine tool moving parts and supporting elements.