Based On The PLC Machining Center Tool Change Control System Improvement And Optimization

Machining Center(MC)is a kind of CNC machine tool with automatic knife exchange function.It has high efficiency and high precision.It is the most widely used integrated CNC machine tool in the world.The machining center has an automatic tool changer(ATC),which can concentrate on many kinds of machining processes,which is3 times higher than that of the ordinary machine tool.The automatic tool replacement device uses the manipulator as the complement of the tool changing mechanism.It can automatically complete the tool exchange between the spindle and the knife library,so it can automatically finish the milling,boring,and expansion in the processing process.But the automatic tool changing system of machining center is compared with traditional pure mechanical equipment or machine oriented processing equipment.The speed and accuracy of control system still have room for improvement and improvement.Based on the above considerations,this paper studied the related research and application of automatic tool changer at home and abroad.This paper analyzes the stability of the mechanical and electrical connection structure,the automatic tool changing process and the automatic tool changing control system in the automatic tool changer at present.It put forward the main shortcomings of the current automatic tool changer.First,because of the poor feedback of the control system,the speed of automatic tool changing is difficult to improve.Second,the wear that the machining center is difficult to avoid during the use process will cause some deviation in the mechanical structure and lose control accuracy.Three,the automatic tool changer system has caused interference to the control system due to the influence of the number of tools.On this basis,this paper mainly studies and analyzes the types of tool magazine and automatic tool changer.This paper chooses chain tool magazine and dual arm rotary manipulator as basic objects.Use SIEMENS S7-200 series programmable logic controller(PLC)as the controller of automatic tool changer and use S7-200 PLC PID wizard and PID self tuning function module,and also use the grating scale displacement sensor to feedback the displacement error in real time.Fuzzy PID control is proposed and compared with traditional PID control.This paper presents an improved and optimized automatic knife exchange system.This paper designs automatic knife exchange control system.According to the requirements of analog tool changing,the specific action process and program flow chart are given for feasibility analysis.Understand and master the principle of S7-200PLC and operation method,design hardware circuit connection and automatic tool change control idea,use S7-200 PLC PID function module to introduce PID control to the system.In S7-200 PLC development environment,PLC ladder diagram is designed in Step7 Microwin4.0 Sp9,and automatic tool changing system is realized for driving three phase stepper motor.In this paper,the hardware platform of a complete automatic tool change device is built,and the simulation of PID control is carried out in Step7Microwin4.0 Sp9.After debugging and simulation,we can see that the fuzzy PID control can modify the 3 parameters K_P,K_I and K_D of PID algorithm online,and the control effect is good.The system can achieve high speed and high precision control.