| Ten meters large-sized NC thread grinder analyzed in this paper is the main research product, which is from the sub-topics of National Science and Technology Prejects:"Large, precision, high efficiency, CNC thread processing equipment" (2009ZX04001-171-02). Grinder bed is 12.8 meters. The whole structure is complex and special, and has large size and weight. In the past, scholars mostly studied and analyzed the regular grinding machine, and rarely involved this special grinder. Therefore, for this special grinder, it has actual engineering value to analyse and optimize static, dynamic, thermal characteristics of key parts and whole machine static and dynamic characteristics based on the joint surface.Grinder bed, carriage and head frame are the three key parts which affects the dynamic performance of the machining. The modal analysis of the key parts structure were made by ANSYS. Then, Weak points of the structure were identified, and structural optimization to improve the dynamic performance was finished using natural frequency as target. Structure optimization results show that:the first natural frequency of bed, carriage and head frame was increased 35.46%,13.71%,9.9% compared with the original, and the weight of bed was reduced 7.84%. This was proved to be efficient on dynamic performance improvement and ligh-weight design of key parts.Heat deformation of the head frame spindle system is one main reason which affects the accuracy of the machining. Considering contact heat resistance steady-state thermal analysis and thermal-structural coupled analysis was finished according to heat transfer theory. Results show that:Thermal deformation of the end spindle was the largest, Temperature basically evenly distributed, the static stiffness met the requirements.On the basis of the dynamic and thermal characteristics analysis of key parts, the contact problem of integrated part of machine tool was handled with spring-damping element. Masataka Yoshimura method was applied to determine the stiffness and damping value of each pair of the joint surface.The finete element model based on the joint surface of the whole grinder was established by ANSYS. Then, the static,dynamic and harmonic response characteristics analysis of the whole machine structure based on the improved key components were finished. The influence on dynamic characteristics of the whole machine based on the improved key components by changing the stiffness of each joint surface was studied.The joint surface that has much bigger influence on the whole machine was identified, and the stiffness of these joint surface was optimized, having improved the static and dynamicâ…¢ characteristics of the wholel machine.The results show that static stiffness in x, y,z directions was increased by 19%,22% and 6%.The natural frequency of the wholel grinder was all increased and the first natural frequency of the grinder was increased 27.8%.The resonance amplitude was reduced about 2/3, and the vibration of the grinder has got a very good suppression.Finally, the whole machine structure static and dynamic characteristics based on the improved key components static dynamic characteristics were effectively improved. This paper's results have been applied to the actual manufacture of grinder. |
