Experimental Study On Dynamic Characteristics And Branching Of C-shaped Gantry Parallel Machine Tool

Dynamic characteristic is an important index to evaluate the performance of machine tools.By studying on the dynamic characteristic of machine tool,in order to analyze the weak link of machine tools and provide the reference for the design and optimization of the structure of machine tools.Therefore,the research of dynamic characteristics occupies an important position in the research of parallel machine tools.1)The structure layout and parameters of the machine tool are introduced,the inverse solution of the mechanism is established,the Jacobi matrix of the mechanism is derived.By using the limit boundary searching method,in order to determine the machine working space.And combined with the comprehensive dexterity index,the main selection range of parallel machine tool during machining is determined;in the condition of three typical operating conditions,the force of each branch of the parallel machine tool is analyzed.2)On the basis of considering the stiffness of the major component of the single chain.The stiffness of each single chain is calculated,and by using the relation of stiffness of the single chain,the axial stiffness of the single chain is established.3)By the first-order influence coefficient matrix,the stiffness model of the parallel machine tool is established.The stiffness distribution of the parallel machine tool in the working space is simulated,and the optimal direction of the milling force is determined.4)The vibration system of multiple-degree-of-freedom system is briefly introduced.The differential equation of motion is established,and the dynamic characteristics of the single chain and the frame are analyzed.5)Based on the motion differential equations of the single chain,using Newton-Euler equation to establish the vibration model of parallel machine tool.The natural frequency and the main formation of the machine tool are analyzed.The relationship with the dynamic characteristics and the stiffness distribution are researched.6)The stiffness of the single branch test experiment is designed,the correctness of the theoretical model is verified by the experimental results,and the reason of the error is analyzed.