On the optimum plunger acceleration law in the slow shot phase of pressuredie casting machines

The objective of this pager is to analyse a plunger acceleration law that i s expected to minimize air entrapment in the slow shot phase of pressure di e casting in horizontal cold chambers, and thus to reduce porosity in manuf actured parts. The study is carried out using results from an analytical mo del of the flow of molten metal in the shot sleeve, which is based on the s hallow-water approximation, and whose predicted optimum acceleration parame ters are in good agreement with available experimental results. The results for the surface profiles of the wave formed during plunger movement using plunger acceleration laws which are typically used in pressure die casting are compared with those corresponding to the proposed law. Some analytical predictions for the wave profiles and for the mass of trapped air are compa red with numerical results obtained from a finite-element code, which solve s momentum and mass conservation equations. The limiting values of the init ial filling fraction required for appropriate operating conditions are dete rmined for wide ranges of acceleration parameters and pouring hole location s. (C) 2000 Elsevier Science Ltd. All rights reserved.