Research on structure dynamic optimization design of NC grinder

Abstract

Dynamic optimization design is the key issue to improve machining precision of the machine tool. The accurate finite element model (FEM) of the original numerical control (NC) grinder including dynamic model of combined surface was established based on the results via compared actually dynamic test with theoretical analysis. The method of sensitivity analysis was applied to optimize the layout and parameters of the strengthening ribs of parts. The technique of modal frequency separation was applied to keep frequency separation of the main parts one another, and the structure of the main parts was optimized. The result of dynamic optimization design shows that the first order natural frequency of the new grinder raises 17% compared with the original one, while the relative vibration displacement between head of the grinder and the work piece reduces 10% correspondingly. The grinding chatter marks are eliminated and the machining accuracy is greatly raised. Dynamic optimization design is the key issue to improve machining precision of the machine tool. At present the machine tool manufacture enterprise tend to use the methods with experience, analogy and static design while developing new machine tools. Simple mechanics calculation is the main method to optimize structure parts about intensity, rigidity and vibration stability. The advanced dynamic design technologies and dynamic optimization software are hardly employed. So it is difficult to obtain light weight design and high precision. Especially the high speed machine tools are more difficult to enhance machining precision because of the all kinds of effects about vibration stability and hot deforming of spindle system. The paper used computer modeling and analyzing, and studied the dynamic optimization method of machine tools retrofit design. Firstly the finite element model (FEM) has been established. Dynamic test results have been used to modify theoretical FEM to enhance the modeling precision. Secondly the method of sensitivity analysis was applied to optimize the layout and parameters of the strengthening bars of components. Thirdly The technique of mode frequency separation was applied to keep frequency separation of the main components one another, the increasing of amplitude of machine tool structure vibration has been avoided, and the structure of the main components was optimized. Finally the destination of dynamic optimization of the entire machine tool is reached.