With the rapid development of the automobile industry and the continually increasing of requirement of integrated assembly automation, automotive manufacturing is developing from simple inter-assembly automation into parts, vehicle assembly automation gradually. Automatic assembly technology has become the important area of development of volume-production of the automobile industry in the 21st century. This thesis introduces the design of the chip unit automatic assembly machine′s control system based on S7-300, which can complete the chip unit of disc oil cooler automatic assembling and weighing.The assembly leak-proof quality of the chip unit directly affect disc oil cooler's operational performance, so it is of greatly practical significance.
The chip unit of disc oil cooler includes 6 parts, and this design of the chip unit automatic assembly machine ought to be able to complete 6 parts of following assembly assignments: superimposed in sequence, lamination, packaging, weighing, counting, etc. In addition, to increase the productivity of the production line, this automatic assembly machine should have self-checking and warning function; in order to meet different users′ requirements of production, this automatic assembly machine should be able to act according to the production efficiency when the user needs to adjust the assembly speed correspondingly. Meanwhile, this machine ought to be able to satisfy the man-machine friendly need, make user debug system and understand system operation situation conveniently through the human machine interface. The assembly control system is the core of the chip unit automatic assembly machine, which determines the assembly machine's operational performance. This graduation project is started under the above background and control requirements, and the chip unit automatic assembly machine′s control system based on S7-300 mainly includes: a S7-300 Siemens PLC, 4 S7-200 Siemens PLC, HMI (using WinCC software to configurate), 6 stepping motors, 1 servo motor, 7 asynchronous motors and MM420. Moreover, this control system mainly uses the software which called STEP7V5.4 when it needs hardware configuration, programming. This assembly control system takes S7-300 PLC as a master station, through PROFIBUS-DP connect with 4 S7-200 PLC as slave stations, and simultaneously S7-300 PLC must communicate with the human machine interface as well as MM420 through PROFIBUS. PROFIBUS is an international, open, have been widely used worldwide fieldbus. The equipments produced by different manufacturers of the equipment can be communicated without special handling and transformation when using PROFIBUS in the system. Therefore, this design selects the PROFIBUS to be practical, and decrease design cost as well. A S7-200 PLC controls the servo motor, thus by the servo motor control cam gear, so finally satisfies on various manipulators of the automatic assembly machine to act the changing movement. Other 3 S7-200 PLC control 6 stepping motors, thus control the up and down of the assembly machine's six material poles. In addition, S7-300 PLC connects through PROFIBUS with MM420 by the RS-485 interface, to control the start and speed of the large asynchronous motor, which finally makes the automatic assembly machine main dividing plate start, stop and speed. And the other 6 asynchronous motors which used in controlling the six storehouses are controlled directly by S7-300 to start and stop.
Before this design, firstly we need to understand the automatic assembly machine's concrete control details, for example: Various manipulators' decomposition movement (bracket stretches out, drop, sucker inspiration and so on), then determine the servo motor′s correspondingly concrete control requirements. Secondly, we must make certain the input signal quantity that the system needs, and determine how to assign a good system for the S7-300 PLC input and output signal addresses correspondingly. Thirdly, according to the systems control specific requirements and the allocation, we should coordinate the overall system and each control electrical machinery subsystem's logical relation, then plan flow chart according to the preliminary row good logical relation and the control requirements and use the STL writing program under the flow chart foundation. Fourthly, we need to install S7-300 programming software STEP7V5.4, then take the hardware configuration and software programming on STEP7V5.4 programming software. Finally, we can make the control system complete the chip unit six parts′ assembly requirements through program debugging, revision and consummation. This design focuses on realizing the correspondence between human machine interface and S7-300 PLC using PROFIBUS and WinCC configuration software; carring on the S7-300 station configuration in STEP7 software to realize S7-200 communicate separately with the S7-300; making hardware configuration in the STEP7 and setting parameters in MM420 to control the large asynchronous motor by S7-300 PLC.
