Abstract
Over these years， the programmable logic controller (PLC) have realized the some developements when plc has beed produced. It turned the logical connection to the storage logical connection， and its function from weak to strong， and the result is realizing the progress of the logic control to digital control. it applicats in some airas， from small to big. it realizes the using of simple equipment in achieving a single control to do motion control， process control and distributed control across a variety of tasks. Today， PLC has been in dealing with analog and digital computing， human-machine interfaces and network capabilities ，and has became the mainstream of the field of industrial controls and control equipment. Overall， it has play an increasingly important role in all walks of life .
This article describes the presedent status of the PLC， as well as with other What is the difference between control system， how to PLC， servo， etc. Designed the automatic welding systemsthe which composed by Mitsubishi FX2N-32MR-based as well as ancillary Mitsubishi FX2N-1PG positioning module. This System can be designed with different requirements， such as change in experimental parameters so as to achieving different purposes. The design also uses a touch screen as a man-machine interface through the touch-screen operation parameters， which can be set up to achieve the control of various functions， but also through the touch screen display the test results and the status of currently running on the system for real-time monitoring.
