A reclassification of the die-filling stages in pressure die-casting processes

Traditionally, the die-filling process in pressure die-casting is divided into three stages. This paper initiates the concept of a 'five-stage' process for one-shot pressure die-casting processes. The concept of a 'five-stage' process retains the familiar first and second stages, breaks down the third stage into two and adds a fifth 'residual stage'. It is shown that the maximum metal pressure developed at the end of the fourth stage represents the compressibility of the molten metal and the hydraulic oil. Equations for the dynamic pressures during the fourth stage are derived. There is still a lack of information on the bulk modulus of various molten metals. From the equations derived, an experimental method for the determination of the bulk modulus of molten metal is suggested. The analysis of the five stages, which links the metal feed system with the fluid-power main circuit of the die-casting machine, gives a set of mathematical models for tackling the problem in question.