1. Purposes of simulations

There are two purposes for conducting these simulations; (1) to determine the flow pattern and wave formations of liquid alloy in shot sleeves to reduce air entrapment, and (2) to predict the amount of externally solidified product (ESP) formed and carried into castings. Air entrapment in liquid alloy during the slow shot portion of the process increases the gas porosity of the die casting and thereby degrades its quality. The ESP also degrades the quality of die cast product. Coupled fluid flow and solidification models will provide insight to the preferred plunger displacement history which produce the desired wave dynamics and amount and distribution of solidified phases to minimize air entrapment and ESP in the die cast products.
 

2. Description of the cold chamber die casting process

Die casting is characterized by a source of hydraulic energy that imparts high velocity to molten metal to provide rapid filling of a metal die. After molten metal is introduced into shot sleeve, the plunger moves along the shot sleeve and pushes the liquid alloy through the shot sleeve and into the runner and casting cavity. During the first stage of the plunger motion, the plunger velocity is relatively low. After the plunger has moved a given distance, it is accelerated to a higher velocity for filling the runner and casting cavity. The first portion of the plunger history is called the slow shot, and the latter, the fast shot. Molten metal is injected into die cavity during the fast shot. The emphasis of the simulations in this program are for the shot sleeve filling period and the slow shot portion of the process, as these are the periods when wave and ESP formations are most prevalent.
 

Reference Related to Shot Sleeve Fluid Flow Phenomena:
The following references relating to fluid flow studies and phenomena are provided:

1. Marilyn Thome. and Jerald R. Brevick, "Optimal Slow Shot Velocity Profiles For Cold Chamber Die Casting", North American Die Casting Association, October 2-5, 1995, 53-59

2. Lester W. Garber, "Filling of the Cold Chamber during Slow-Shot Travel," Die Casting Engineer, July-August 1981, 36-38

3. Lester W. Garber, "Theoretical Analysis and Experimental Observation of Air Entrapment during Cold Chamber Filling," Die Casting Engineer, May-June 1982, 14-22

4. H.Y. Lu, W.B. Lee, "A Simplified Approach for the Simulation of Metal Flow in a cylindrical Sleeve Diecasting Cavity," Journal of Materials Processing Technology 91, 1999, 116-120

5. J.H. Jeong, and D.Y. Yang, "Finite Element Analysis of Transient Fluid Flow with Free Surface Using VOF (Volume-Of-Fluid) Method and Adaptive Grid," International Journal for Numerical Methods in Fluids, Vol. 29, 1999, 657-684

6. J. Lopez, J. Hernandez, F. Faura, G. Trapaga, "Shot Sleeve Wave Dynamics in the Slow Phase of Die Casting Injection," Journal of Fluids Engineering, Vol. 122, 2000, 349-356

7. Gerald Backer, Frank Sant: "Using Finite Element Simulation for the Development of Shot Sleeve Velocity Profiles," North American Die Casting Association, 1997, 17-20

8. F. Faura, J. Lopez, J. Hernandez, “On the Optimum Plunger Acceleration Law in the Slow Shot Phase of Pressure Die Casting Machines,"  International Journal of Machine Tools & Manufacture, Vol. 41, 2001, 173-191