Abstract
A mathematical model has been developed to simulate the flow pattern of molten metal and to predict the liquid-gas interface shape in the shot sleeve of a cold chamber die casting machine during the injection stage. The flow pattern in the shot sleeve is known to be closely related to the extent of gas entrapment of molten metal in the sleeve during the injection operation. In this study, a Variable Spacing Even Mesh (VSEM) method is proposed to incorporate with a computational fluid dynamics technique, named SOLA-MAC, to simulate the flow pattern in the shot sleeve. SOLA-MAC can deal with free surface flow problems while the VSEM method is used to handle the problem where the space in the shot sleeve keeps decreasing as the plunger moves to push the molten metal. The model is then tested on the shot sleeve of a cold chamber die casting machine. Four plunger speeds are tested to demonstrate the effects on the flow pattern of molten metal in the shot sleeve. The critical speed found in this study is 38 cm/s and it is close to the reported critical speed under the conditions that the space between the plunger and the sleeve end is 5 cm in diameter and 30 cm in length, and the fill ratio is 50%. As the plunger speed is slower than the critical speed, the wave front propagates along the sleeve faster than the plunger and reflects against the end wall of the sleeve. The remaining air in the shot sleeve is entrained as the wave front enters to the gate. As the plunger speed is higher than the suggested critical speed, the melt is immediately pushed higher in front of the plunger and forms a surge. The surge traps air in the early stage of the injection process.
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Acknowledgments
The authors would like to express their gratitude to the Metal Industries Research and Development Center in Taiwan, R.O.C., for their financial support of this study.
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Han, TH., Kuo, JH. & Hwang, WS. Numerical Simulation of the Liquid-Gas Interface Shape in the Shot Sleeve of Cold Chamber Die Casting Machine. J. of Materi Eng and Perform 16, 521–526 (2007). https://doi.org/10.1007/s11665-007-9093-4
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DOI: https://doi.org/10.1007/s11665-007-9093-4