The Research On Vacuum Adjustable-pressure Casting Integrated Control System Based On PLC

Currently the foundry industry in China has made a spurt of progress ofdevelopment，and the vacuum adjustable-pressure casting technology has a wideapplication prospect in ordnance, shipping, automotive and defense industry fields.Vacuum adjustable-pressure casting process is the ideal way to produce qualityprecision castings, it also has been paid close attention by foundry industry. Thecastings’ quality depends on the control precision casting control system and itsresponse speed. As to the traditional casting control system has a low degree ofautomation, low casting precision and low integration degree, this paper, designs avacuum adjustable-pressure casting integrated control system based on PLC whichcombined the vacuum adjustable-pressure casting technology and PLC control system.Firstly, this paper focus on the design of vacuum adjustable-pressure field controlsystem. Based on the analysis of the existing casting equipment’s principle andprocess，the equipment can accurately produce needed castings depend on the differentprocess parameters by using high precision digital combination valve and pneumaticball valve. The field control system takes the Siemens S7-200series PLC as the controlcore. And the peripheral interface circuit includes: analog/digital input circuitry,digital output circuits，DC power supply, temperature acquisition circuit ect. The Fieldcontrol station programs with STEP7-Micro/WIN software, Using the ladder diagrm(LAD) programming language to complete the on-site sampling, data processing, dataupload, and the control based on the technological requirement.In the PC software design, using VC++prepared monitoring and managementsoftware, periodically download from PLC data make the system accurately controlaccording to each process section. And timely delivery while include pressure data,the data of valve and process to the operator as dynamic graphs, rolling data table,dynamic display of casting process. Finally the system can record those data to thedatabase.Finally, the lag pressure closed-loop control circuit is designed based on thevacuum adjustable-pressure casting process showing nonlinear, time-varyingcharacteristics. The system achieve the process control of the vacuumadjustable-pressure casting by using conventional PID and fuzzy control.The vacuum adjustable-pressure casting integrated control system based on PLC which designed in this paper makes PLC technology, VC++software development，classical PID control technology, fuzzy control technology, database technology,distributed control technology and vacuum adjustable-pressure casting technologymerged. Meanwhile, it makes the control software interface more flexible, the systemstructure more rational, casting historical data management analysis more convenienceand it realizes accurate control to the vacuum adjustable-pressure casting industrialprocesses. Thus, it is a great significance to the extension of the vacuumadjustable-pressure casting technology and further research.