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.

Analysis of Mass Transfer Process in the Pore Free Technique

1995 ◽  
Vol 117 (2) ◽  
pp. 215-219 ◽  
Author(s):  
Genick Bar-Meir
Keyword(s):  
Mass Transfer ◽  
Dimensionless Parameter ◽  
Die Casting ◽  
Air Entrainment ◽  
Mass Transfer Process ◽  
Critical Value ◽  
First Case ◽  
Pressure Die Casting ◽  
The Relationship ◽  
Transfer Mechanisms

Air entrainment is one of the most significant problems in pressure die casting. A possible solution is to use the Pore Free technique. In this technique an oxygen is introduced into the die to react with the liquid metal. The vacuum created by the reaction reduces the porosity. The life span of the mold is augmented by the reduction of the pressure during the process. In some cases the Pore Free technique yields acceptable results, i.e., low porosity, while in other cases the results are not satisfactory. These differing results can be explained by an analysis of the mechanisms involved. A simple model is proposed based on conservation laws that describes the relationship between mass transfer mechanisms and pressure deviation. The model indicates that there is a critical dimensionless parameter above which the pressure is decreased and below which the pressure is increased. In the first case, when the parameter exceeds the critical value, the technique is useful. In the second case, when the parameter is less than the critical value, introducing oxygen does not greatly reduce the porosity. The analysis demonstrates that the Pore Free and vacuum venting techniques account for two different extremes. The first case is when the flow is orderly throughout the chamber in which vacuum venting can produce acceptable results. The second case is when the flow is turbulent and the Pore Free technique is the better choice.

Thermal Analysis of a Bi-Metallic Chill Vent for High Pressure Die Casting

2010 ◽  
Vol 654-656 ◽  
pp. 791-794 ◽  
Author(s):  
Mohammad Imran ◽  
Rajpreet Dhaliwal ◽  
Syed H. Masood
Keyword(s):  
Thermal Analysis ◽  
High Pressure ◽  
Automotive Industry ◽  
Die Casting ◽  
Internal Diameter ◽  
High Pressure Die Casting ◽  
Alloy Material ◽  
Transient Thermal ◽  
Pressure Die Casting ◽  
Residual Air

High pressure die casting (HPDC) is widely used for manufacturing aluminum parts in automotive industry. In high pressure die casting mold, chill vents are used to allow residual air and gases to exhaust out from the mold cavity. The objective of this paper is to design and develop a bi- metallic chill vent for high pressure die casting using copper alloy material having high thermal conductivity, coated with steel layer on the surface. Transient thermal analysis was carried out using ANSYS software, and temperature distribution was compared with bimetallic and tool steel chill vents. The results show a faster extraction of heat in bi-metallic chill vent than that with steel. This paper also presents the effect of varying internal diameter of cooling channel in chill vent cooling.

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.

Effect of Temperature on the Properties of High Pressure Die Casting

2010 ◽  
Vol 649 ◽  
pp. 473-479 ◽  
Author(s):  
Jenő Dúl ◽  
Richárd Szabó ◽  
Attila Simcsák
Keyword(s):  
High Pressure ◽  
Data Acquisition ◽  
Die Casting ◽  
Data Acquisition System ◽  
Effect Of Temperature ◽  
High Pressure Die Casting ◽  
Die Castings ◽  
Pressure Die Casting ◽  
The Relationship

Quality of high pressure die castings is influenced by a lot of factors. Among them, the most important ones are the melt-, and die temperatures. This paper shows a data acquisition system, developed for measuring the melt and die temperatures and the results of the temperature measurements obtained under variable conditions. Evaluation of the relationship between the interrelated temperatures and the casting properties is based on analyzing the structure of the castings.

Characterization of Magnesium Automotive Components Produced by Super-Vacuum Die Casting Process

2009 ◽  
Vol 618-619 ◽  
pp. 381-386 ◽  
Author(s):  
K. Sadayappan ◽  
W. Kasprzak ◽  
Zach Brown ◽  
L. Quimet ◽  
Alan A. Luo
Keyword(s):  
Die Casting ◽  
Casting Process ◽  
Air Entrainment ◽  
Automotive Components ◽  
Vacuum Die Casting ◽  
Heat Treated ◽  
Conventional Heat Treatment ◽  
Die Casting Process ◽  
Rapidly Solidified ◽  
Pressure Die Casting

Magnesium automotive components are currently produced by high pressure die casting. These castings cannot be heat-treated to improve the strength and ductility mainly due to the casting imperfections such as porosity and inclusions created by the air entrainment during the turbulent mold filing. These imperfections also prevent magnesium components to be used for highly stressed body components. Efforts were made to produce high integrity magnesium castings through a Super-Vacuum Die Casting process. The AZ91D castings were found to have very low porosity and can be heat-treated without blisters. The tensile properties of the castings were satisfactory. The mechanical properties and thermal analysis indicate that the conventional heat treatment procedure needs to be optimized for such thin sectioned and rapidly solidified castings which have very fine microstructures.

Process of Die Cavity Filling in Pressure Die-Casting Production

2012 ◽  
Vol 630 ◽  
pp. 41-44 ◽  
Author(s):  
Marcel Fedák ◽  
Pavol Semanco ◽  
Emil Ragan ◽  
Miroslav Rimár
Keyword(s):  
Differential Equations ◽  
Turbulent Flow ◽  
Die Casting ◽  
Laminar And Turbulent Flow ◽  
Cavity Filling ◽  
Pressure Die Casting ◽  
Casting Production

Process of die cavity filling in pressure die casting is described by relations for the laminar and turbulent flow and simulating in transparent die. It is shown at pressure die casting machines trough arrangement of the derived differential equations that the circuit of the process is stable aperiodical or damped oscillating favorable for control.

Numerical Simulation of Back Pressure Influenced Aluminum Component’s HPDC Process

2010 ◽  
Vol 139-141 ◽  
pp. 549-552 ◽  
Author(s):  
Wen Jiong Cao ◽  
Zhao Yao Zhou ◽  
Yi He ◽  
Yuan Biao Wu
Keyword(s):  
Molten Metal ◽  
Flow Behavior ◽  
Die Casting ◽  
Back Pressure ◽  
Filling Process ◽  
Porosity Defects ◽  
Simulation Results ◽  
Pressure Die Casting ◽  
Residual Air ◽  
Actual Part

Due to the flow behavior of molten metal is affected by the back pressure of mold residual air in high pressure die casting (HPDC) process, the back pressure conditions should be considered in order to simulate the HPDC process precisely. In this study, an aluminum colander of automobile’s filling process in HPDC was calculated by combining the back pressure conditions. The optimized schemes were given by considering the simulation results. Both initial and optimized schemes simulation results were compared with actual parts. The contribution of gas porosity between simulation and actual part were in agreement when back pressure conditions were applied. The local back pressure can be controlled by coordinating the position of the vents. Therefore the flow behavior of molten metal can be changed and the porosity defects can be fixed.

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.

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