Design And Research Of Quick Die Change System For Skin Stretch Forming Machine

With the rapid development of Chinese aviation industry,there is an increasing demand for skin stretch forming machines and stretch forming technology.Undeniably,some considerable progress has been made in China for stretch forming technology and equipment in recent years.However,our investigation indicates that die changing technology of the skin stretch forming is backward in many domestic aircraft manufacturing enterprises.The manual die change work of skin stretch forming results in lower efficiency and poor accuracy.Moreover,the skin stretch forming machine is idle during quenching process of workpieces initially stretch formed,which leads to lower equipment utilization.Therefore,the research of quick die change systems for skin stretch forming machines becomes a main direction for improving the effeciency of skin stretch forming.Thus,six design objectives of the quick die change system and a new mode of stretch forming die change work based on “Double Operating Station” are proposed in this paper.The main work of this paper is as follows:Firstly,after weighing the advantages and disadvantages of sevaral schemes,a new type of quick die change system of skin stretch forming machine based on horizontal and vertical mobile working-platform is designed to meet the need of improving the working efficiency of skin stretch forming.Secondly,according to the proposed scheme,the quick die change system of skin stretch forming machine is detailedly designed based on modularity thought,including the design of the mobile working-platform,the track platform,the covering-platform,the cushion blocks,the overhead travelling crane and the system positioning device.Then,Solidworks is used modeling 3D model of each module and component.ANSYS/Workbench software is employed to examine the strength and stiffness of the mobile working-platform body and the track platform under the maximum stretching force.The simulation results show that the structure of the mobile working-platform body and the track platform can meet the strength requirements.Finite element analysis of the wheel-rail contact is carried out in Abaqus software.The simulation results indicate that the maximum stress of the wheel-rail contact locates at the wheel-rail contact surface,and the maximum value is lower than the yield strength of the material.ADAMS kinematics simulation software is used to simulate the move of mobile working-platform,and the results indicate that the moving of the mobile working-platform is smooth,which meets the feasibility and security requirements.Finally,the control system of the new die change system is designed,which includes the motion control of the mobile working-platform,the control of the hydraulic system and the positioning control of the new die change system.MATLAB/Simulink software is used to simulate the synchronized control of the motors and hydraulic system of the mobile working-platform.The control of the 4 motors of the mobile working-platform is based on the deviation coupling mode to achieve synchronized rotating.The control of the hydraulic system is based on cross-coupling and displacement master-slave phase mixing to achieve the synchronized lifting of multi-cylinder hydraulic system.The positioning system designed in this paper has the function of calling the storage information from a database.It is able to accurately store information of location,which could be used the next time.The control of positioning system mainly includes the motion control of the overhead travelling crane,laser ranging positioning of the mobile working-platform,and the accurate positioning of skin stretch forming die.This quick die change system has the advantages of high automation,simple operation,safety and efficiency.It greatly improves the utilization and working efficiency of the skin stretching forming machine.