The Design And Analysis Of Hydraulic Support System Used For Mirror Milling Of Thin-walled Members

In the process of mirror milling on rocket fuel tank,it is easy to appear deformation and shimmy,because fuel tank is thin and rigidity is poor.These would seriously affect the machining accuracy.This paper takes the mirror milling of grid on rocket fuel tank as the research object.The key study is hydraulic support system.Firstly,in the light of the characteristics of mirror milling,the hydraulic support system is designed in this paper.It is composed of hydraulic actuator and follow-up support head.The structure of hydraulic actuator is pump control hydraulic differential cylinder,which is integrated form.It could effectively reduce weight of the system,improve the response speed in this structure.The follow-up support head haves rigid-flexible multi-point supporting.The flexible support could reduce the shimmy of the thin-walled member,the rigid support could locate the thin-walled member accurately.As the same time,multi-point supporting increases the support area,reduce the control difficulty.Then,according to the actual structure of the system,this paper established the mathematical model and simulation model of the hydraulic support system.The dynamic characteristics and the features of vibration suppression of hydraulic support system are analyzed,especially studied the influence of the spring stiffness on the vibration suppression.The results showed that: the tacking characteristic of hydraulic actuator to cutting force is well,it could respond to the cutting force quickly and accurately.And the spring stiffness coefficient of follow-up support head haves an enormous influence on the vibration suppression characteristics,so we should select appropriate spring stiffness coefficient to reach the effect of vibration suppression.Finally,we set up the experimental platform.The experimental platform is composed of hydraulic support system and electrical control system.The electric control system adopts the PC as a upper computer to complete the writing of the control program,setting and monitoring of variables.The electric control system adopts the SIEMENS S7-300 PLC as controller to complete the execution of the program.Then we had a test on the experimental platform.Through the analysis of data collected from test,we found that the test curve of the hydraulic cylinder piston rod displacement and the simulation curve are very close and running condition satisfies the requirement of control system,which had verified the correctness of the mathematical model and simulation model.