The Investigation Of Counter-Gravity Casting Control Technology

Counter-gravity casting technology is an ideal method of producing large-size high-quality aluminum parts. The pressurizing control system of the counter-gravity casting is the core of the counter-gravity casting equipment, and is the key of obtaining good castings. But some problems exist in present control systems. For example, the system is not related to the technology closely, and the system only can complete one function. Focusing on the questions, the control technology of counter-gravity casting is researched and the multifunctional counter-gravity casting control system is designed in this paper.Firstly, the pressurizing pattern of counter-gravity casting is analyzed. The filling process and solidification process is defined from control side, input pattern parameters realizing process control are determined, the effect of key parameters on the casting quality is analyzed, and different pressurizing patterns in different condition are researched, which is the foundation of the realization of the filling process control of counter-gravity casting.Secondly, the control project of counter-gravity casting is researched. After the mathematics model of the control object of the counter-gravity casting process is analyzed, PID controller is designed, and the PID parameters are determined by MATLAB simulation. To solve the time-delay of system, Dalin algorithm and Smith prediction algorithm are separately used to design system. The result curve of MATLAB simulation indicates that these two algorithms can both improve system's dynamic property and stability obviously.Thirdly, the pneumatic adjustment unit of the control system is designed. Based on the analysis of the pneumatic structure of the counter-gravity casting equipment, the gas-in, pressure-adjusted and gas-out systems of low-pressure casting, counter-pressure casting and vacuum-assisted pressure casting are designed individually. An assembled valve (responding time is only 80ms) is developed, whichimproves system's responding speed.At last, the multifunctional counter-gravity casting control system is designed. Fuzzy algorithm is combined to PID algorithm, which improves the filling linearity, reduces the surface fluctuation, and improves system's control precision. The assembled valve is adopted to design the pneumatic system, and the system can realize several functions such as low-pressure casting, counter-pressure casting and vacuum-assisted pressure casting. The control software compiled with Delphi has good man-machine interface and is easy to operate and maintain.Production and practice indicates that the multifunctional counter-gravity casting control system researched in this paper has following advantages: convenient to operate, works reliably, track effect is good and control precision is high. Castings produced by counter-gravity casting equipment with this control system have good metallurgy quality.