Analysis of the Flow in a High-Pressure Die Casting Injection Chamber

2003 ◽  
Vol 125 (2) ◽  
pp. 315-324 ◽  
Author(s):  
J. Herna´ndez ◽  
J. Lo´pez ◽  
F. Faura ◽  
P. Go´mez
Keyword(s):  
Shallow Water ◽  
Die Casting ◽  
Operating Conditions ◽  
Water Model ◽  
Accurate Estimation ◽  
Viscous Effects ◽  
Filling Fraction ◽  
Filling Time ◽  
Entrapped Air ◽  
Pressure Die Casting

The flow in the injection chamber of pressure die casting machines is analyzed using a model based on the shallow-water approximation which takes into account the effects of wave reflection against the end wall of the chamber. The governing equations are solved numerically using the method of characteristics and a finite difference grid based on the inverse marching method. The results of the model for wave profiles, volume of air remaining in the injection chamber at the instant at which the molten metal reaches the gate to the die cavity, and optimum values of the parameters characterizing the law of plunger motion, are compared with the numerical results obtained from a finite element code, which solves the two-dimensional momentum and mass conservation equations, taking into account nonhydrostatic and viscous effects. We found that, although the shallow-water model does not provide a very accurate estimation of the mass of entrapped air in the injection chamber for certain ranges of working conditions, it does describe reasonably well the influence of the acceleration parameters and the initial filling fraction on the entrapped air mass, and can be of help in selecting operating conditions that reduce air entrapment while keeping the injection chamber filling time as low as possible.

Shot Sleeve Wave Dynamics in the Slow Phase of Die Casting Injection

2000 ◽  
Vol 122 (2) ◽  
pp. 349-356 ◽  
Author(s):  
J. Lo´pez ◽  
J. Herna´ndez ◽  
F. Faura ◽  
G. Trapaga
Keyword(s):  
Die Casting ◽  
Wave Theory ◽  
Finite Amplitude ◽  
Slow Phase ◽  
Shot Sleeve ◽  
Viscous Effects ◽  
Filling Fraction ◽  
Wave Dynamics ◽  
Injection Process ◽  
Filling Time

An analysis is carried out on the wave formed during the slow phase of die casting injection processes. Viscous effects are assumed to be negligible and the problem is treated two-dimensionally using finite amplitude wave theory. Two commonly used types of plunger movements are considered, for which all the possible wave profiles are analyzed in depth as a function of the parameters which characterize the law of acceleration applied to the plunger, the initial shot sleeve filling fraction, and the geometrical characteristics of the problem. Different relationships between the relevant dimensionless parameters of the system are proposed, which make it possible to optimize the injection process, and so reduce the entrapment of air which leads to porosity. The validity of such relationships is analyzed in detail for different ranges of parameters. Some of the results obtained for the optimum acceleration are compared with those of other authors and experimental measurements. Finally, a law of plunger acceleration which would completely eliminate the air from the shot sleeve at the end of the slow phase of injection and minimizes the filling time is derived. [S0098-2202(00)02002-2]

Influence of Unsteady Effects on Air Venting in Pressure Die Casting

2001 ◽  
Vol 123 (4) ◽  
pp. 884-892 ◽  
Author(s):  
J. Herna´ndez ◽  
J. Lo´pez ◽  
F. Faura
Keyword(s):  
Method Of Characteristics ◽  
Die Casting ◽  
Operating Conditions ◽  
Filling Process ◽  
Air Mass ◽  
One Dimensional ◽  
Trapped Air ◽  
Unsteady Effects ◽  
Pressure Die Casting ◽  
Selection Of

The influence of unsteady effects on the evacuation of air through vents in pressure die casting processes is analyzed. A model is proposed which considers the air flow as one-dimensional and adiabatic, and which retains friction effects. Venting conditions for wide ranges of the relevant dimensionless parameters are analyzed for both atmospheric and vacuum venting systems. The model is solved numerically using the method of characteristics and its results are compared with those obtained for quasi-steady models. It is shown that wide ranges of operating conditions can exist in practical situations, for which unsteady effects, neglected in previous models, are important and must be taken into account to determine the air mass entrapped at the end of the filling process. The selection of parameters which will reduce the amount of trapped air and thus porosity in manufactured parts is also discussed.

scholarly journals Towards a new friction model for shallow water equations through an interactive viscous layer

2019 ◽  
Vol 53 (1) ◽  
pp. 269-299 ◽  
Author(s):  
François James ◽  
Pierre-Yves Lagrée ◽  
Minh H. Le ◽  
Mathilde Legrand
Keyword(s):  
Shallow Water ◽  
Stokes Equations ◽  
Water Model ◽  
Finite Volume Scheme ◽  
Inviscid Fluid ◽  
Phase Lag ◽  
Viscous Layer ◽  
Viscous Effects ◽  
Shallow Water Models ◽  
Water Models

The derivation of shallow water models from Navier–Stokes equations is revisited yielding a class of two-layer shallow water models. An improved velocity profile is proposed, based on the superposition of an inviscid fluid and a viscous layer inspired by the Interactive Boundary Layer interaction used in aeronautics. This leads to a new friction law which depends not only on velocity and depth but also on the variations of velocity and thickness of the viscous layer. The resulting system is an extended shallow water model consisting of three depth-integrated equations: the first two are mass and momentum conservation in which a slight correction on hydrostatic pressure has been made; the third one, known as von Kármán equation, describes the evolution of the viscous layer. This coupled model is shown to be conditionally hyperbolic, and a Godunov-type finite volume scheme is also proposed. Several numerical examples are provided and compared to the Multi-Layer Saint-Venant model. They emphasize the ability of the model to deal with unsteady viscous effects. They illustrate also the phase-lag between friction and topography, and even recover possible reverse flows.

Pressure Die Casting: A Model of Vacuum Pumping

1996 ◽  
Vol 118 (2) ◽  
pp. 259-265 ◽  
Author(s):  
G. Bar-Meir ◽  
E. R. G. Eckert ◽  
R. J. Goldstein
Keyword(s):  
Elastic Moduli ◽  
Die Casting ◽  
Total Porosity ◽  
Air Entrainment ◽  
Pressure Variation ◽  
Filling Time ◽  
Cavity Filling ◽  
Pressure Die Casting ◽  
The Relationship ◽  
Residual Air

Multifunctional characteristics of die casting parts are significantly compromised by the presence of voids, which can result in a substantial decrease in the elastic moduli and thermal conductivity. Gas/air porosity constitutes a large part of the total porosity. To reduce the porosity due to the gas/air entrainment, a vacuum can be applied to remove the residual air in the die. In some cases vacuum castings have low porosity, while in other cases the results are not satisfactory. These differing results can be explained in some instances by an analysis of the vent area. A simple model is proposed based on conservation laws which describes the relationship between vent area and pressure variation in the die. The analysis of vacuum venting indicates that there is a critical/optimum vent area below which the ventilation is poor and above which the resistance to the air flow is minimal. The model yields a simple equation to select the optimum area which is a function of the duct resistance, the evacuated volume, and the filling time. This result should be useful to the design engineer. The result also provides a tool to “measure” the vent size for numerical simulations of the cavity filling, taking into account the compressibility of the gas.

Modelling the pressure die casting process with the boundary element method: Die deformation model for flash prevention

1998 ◽  
Vol 212 (3) ◽  
pp. 197-215 ◽  
Author(s):  
J Milroy ◽  
S Hinduja ◽  
K Davey
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Die Casting ◽  
Injection Pressure ◽  
Casting Process ◽  
Operating Conditions ◽  
Deformation Model ◽  
The Individual ◽  
Pressure Die Casting ◽  
Element Method

In pressure die casting, the thermal loads, injection pressure and clamping forces cause the individual blocks of a die to deform. This deformation results in gaps between the interface surfaces which, if big enough and in the vicinity of the cavity, permit material to seep into the gaps, causing flash. This paper describes a thermoelastic model to predict the deformation of the die so that it can be machined to prevent flash. The model is based on the boundary element method and allows the use of linear isoparametric or quadratic subparametric elements. Each die block is analysed as a separate problem. To avoid the occurrence of flash, the model suggests the amounts that should be machined from each die block. The predicted deformation has been experimentally verified by measuring the profile of a test die using displacement transducers and die impressions. It is shown that there is good agreement between the predicted and experimental results for different operating conditions. By machining the amounts suggested by the model, the test die was run without flash at operating conditions that had previously resulted in flash.

On the Critical Plunger Speed and Three-Dimensional Effects in High-Pressure Die Casting Injection Chambers

2003 ◽  
Vol 125 (3) ◽  
pp. 529-537 ◽  
Author(s):  
J. Lo´pez ◽  
F. Faura ◽  
J. Herna´ndez ◽  
P. Go´mez
Keyword(s):  
Molten Metal ◽  
Cross Section ◽  
Die Casting ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Water Model ◽  
Two Dimensional ◽  
Shallow Water Model ◽  
One Dimensional ◽  
Pressure Die Casting

During the initial slow stage of the injection process in high-pressure die casting machines with horizontal cold chamber, a plunger pushes the molten metal which partially fills the injection chamber, causing the formation of a gravity wave. The evolution of the wave surface profile, which depends on the plunger acceleration law, may trap air in the molten metal, causing porosity when the metal solidifies. In this work, a one-dimensional shallow-water model, which is solved numerically using the method of characteristics, and a three-dimensional numerical model, based on a finite element formulation and the volume of fluid (VOF) method for treating the free surface, are used to analyze the flow of molten metal in an injection chamber of circular cross section. The results for the evolution of the free surface obtained from both models for different plunger motion laws and initial filling fractions of the injection chamber were in good agreement for broad ranges of operating conditions. The existence of a critical plunger speed, above which the reflection of the wave of molten metal against the chamber ceiling might appreciably increase air entrapment effects, is investigated. The results for the wave profiles in chambers of circular cross section are compared with those obtained in an equivalent two-dimensional configuration of the injection chamber, for which the shallow-water model is solved analytically. It is shown how the results obtained by applying the one-dimensional model to a two-dimensional chamber configuration can be used to reproduce, with an acceptable degree of accuracy, the salient characteristics of the flow of molten metal in a real injection chamber of circular cross section.

Experimental Investigation of Porosity Formation During the Slow Injection Phase in High-Pressure Die-Casting Processes

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
R. Zamora ◽  
J. J. Hernandez-Ortega ◽  
F. Faura ◽  
J. Lopez ◽  
J. Hernandez
Keyword(s):  
High Pressure ◽  
Die Casting ◽  
Three Dimensional ◽  
Casting Machine ◽  
Operating Conditions ◽  
Slow Phase ◽  
Air Entrapment ◽  
High Pressure Die Casting ◽  
Numerical Predictions ◽  
Pressure Die Casting

The air entrapment mechanisms in die-casting injection chambers that may produce porosity in manufactured parts are analyzed in this work using visualization techniques of the flow in a transparent injection chamber model, using water as working fluid. In particular, results for the free-surface profile evolution and for the volume of air remaining in the chamber at the instant at which the water begins to flow through the runner are analyzed for different maximum plunger speeds and initial filling fractions. A comparison between these visualizations and the numerical results of Zamora et al. (2007, “Experimental Verification of Numerical Predictions for the Optimum Plunger Speed in the Slow-Phase of a High-Pressure Die Casting Machine,” Int. J. Adv. Manuf. Technol., 33, pp. 266–276) which were obtained using a three-dimensional numerical model, shows a good degree of agreement. After discussing the air entrapment mechanisms that may produce porosity in manufactured parts, different experiments, which were carried out under real operating conditions using an aluminum alloy in a high-pressure die-casting machine with horizontal cold chamber, will be presented. The die-cavity geometry used in the experiments was appropriately modified to isolate the slow shot phase from the rest of the injection process, and the porosity levels in the manufactured parts were measured using a gravimetric technique. The optimum values of the maximum plunger speed that minimizes porosity in the manufactured parts have been determined. These values are very close to the previous numerical predictions of López et al. (2003, “On the Critical Plunger Speed and Three-Dimensional Effects in High-Pressure Die Casting Injection Chambers,” ASME J. Manuf. Sci. Eng., 125, pp. 529–537)

ANALYSIS OF SOME SHALLOW WATER PROBLEMS WITH RIGID-LID HYPOTHESIS

2001 ◽  
Vol 11 (06) ◽  
pp. 979-999 ◽  
Author(s):  
B. DI MARTINO ◽  
C. GIACOMONI ◽  
P. ORENGA
Keyword(s):  
Shallow Water ◽  
Water Model ◽  
Shallow Water Model ◽  
Viscous Effects ◽  
Weak Formulation ◽  
Mean Velocity ◽  
Numerical Resolution ◽  
Comparative Results ◽  
Geophysical Flow ◽  
Water Problems

We present in this paper the analysis and the comparison of two two-dimensional geophysical flow problems using a rigid-lid approximation (i.e. we do not take into account the variation of surface elevation ζ). A first rigid-lid shallow water model (noted SWRL) is obtained by neglecting the variation of the surface in a weak formulation of a usual viscous shallow water model in depth-mean velocity formulation (noted SWFS for shallow water with free surface). We establish some existence results for this model and we propose a numerical resolution method. The second model we consider is an adaptation of the lake equations proposed by Levermore, Oliver and Titi,4 in which we take into account the viscous effects, in order to compare the two approaches. For the numerical resolution, we apply the curl operator on these equations and we propose a numerical algorithm to solve this problem, that we note SWLV (shallow water for the lake with viscosity). We present finally some comparative results in an idealized configuration between the SWRL, SWLV and SWFS models (in the case where the rigid-lid approximation seems to be reasonable).

Optimum Runner Design for Die Casting Using CFD Simulations and Verification With Water-Model Experiments

2014 ◽  
Author(s):  
Ken’ichi Kanazawa ◽  
Ken’ichi Yano ◽  
Jun’ichi Ogura ◽  
Yasunori Nemoto
Keyword(s):  
Molten Metal ◽  
Die Casting ◽  
Air Entrainment ◽  
Optimization Method ◽  
Water Model ◽  
Cfd Simulations ◽  
Mathematical Functions ◽  
Model Experiments ◽  
Runner Design ◽  
Pressure Die Casting

This study aimed to optimize the design of a runner for high-pressure die casting (HPDC) using computational fluid dynamics (CFD) simulations, and to verify the effectiveness of the runner with water-model experiments. A runner is a part of the flow path through which molten metal enters a product part. As a design problem, we sought to optimize the shape of the runner to minimize air entrainment in the runner and align the flow of molten metal after it passed through the runner. The problem was solved using our proposed nonparametric shape optimization method. The method is based on a genetic algorithm (GA), and directly treats a geometric shape that is comprised of several curves as an individual of a GA in the form of a set of mathematical functions. In addition, the crossover, which is one of the genetic operations, is defined as a weighted summation of two parent curves. Thus, the optimization method can generate optimized shapes with a lot of flexibility. The effectiveness of the optimized shape of the runner was demonstrated with both CFD simulations and water-model experiments using a visualization device for HPDC.

A Development of Virtual Manufacturing System for Magnesium High Pressure Die Casting Processes

Materials ◽  
2003 ◽  
Author(s):  
Weilong Chen
Keyword(s):  
High Pressure ◽  
Magnesium Alloys ◽  
Die Casting ◽  
Virtual Manufacturing ◽  
Mold Design ◽  
High Pressure Die Casting ◽  
Molten Magnesium ◽  
Pressure Die Casting ◽  
Soft And Hardware ◽  
Free Magnesium

In recent years, high-pressure die-casting magnesium components have been gaining currency worldwide because of the excellent properties that magnesium alloys can offer to meet new product requirements. With the increasing application of magnesium parts worldwide, many research and development projects have been carried out to advance HPDC technology. However, truly optimized mold design and production of defect free castings remains a challenge for die casters. For many HPDC magnesium products, especially those specified for porosity-free and high cosmetic requirement, the challenge not only comes form a lack of a deeper understanding of how molten magnesium alloys fill the mold cavity and form defects, but also from improper preliminary part design. This study proposes a virtual prototyping system that integrates several effective soft and hardware tools for both the part and mold-design engineer to evaluate part manufacturability. Also, investigated in this study are the major causes of those defects that are the predominant cause of rejection of thin walled, leak-free magnesium parts requiring highly cosmetic finishes.

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