CAE simulation of HPDC Process with Automobile part (Oil · PDF fileCAE simulation of HPDC Process with Automobile part (Oil Pan) ... Computer Aided Engineering ... The result is used

CAE simulation of HPDC Process with Automobile part (Oil Pan)

1 Hong-Kyu Kwon, 2Kwang-Kyu Seo

1, First Author Namseoul University, [email protected] *2,Corresponding Author Sangmyung University, [email protected]

Abstract

In this research, Computer Aided Engineering (CAE) simulation was performed by using the simulation software (AnyCasting) in order to optimize casting design of an automobile part (Oil Pan_DX2E) which is well known and complicated to achieve a good casting layout. The simulation results were analyzed and compared with experimental results. During the filling process, internal porosities caused by air entrap were predicted and reduced remarkably by the modification of the gate system and the configuration of overflow. With the solidification analysis, internal porosities caused by the solidification shrinkage were predicted and reduced by the modification of the gate system. For making better permanent High Pressure Die Casting (HPDC) mold, cooling systems on several thick areas are proposed in order to reduce internal porosities caused by the solidification shrinkage.

Keywords: CAE simulation, HPDC, Solidification, Casting design, Flow Front Temperature

1. Introduction

The method of HPDC (High Pressure Die Casting) is one of the most important techniques for manufacturing automobile parts and electronic parts, and one of the economical casting techniques that can manufacture complex shapes at one time. When manufacturing HPDC mold, generally, the casting layout design should be considered based on the relation among injection system, casting condition, gate system, and cooling system. In current casting industries, the design and development of a casting layout is a trial-and-error method based on heuristic know-how. The solution achieved in such a way lacks scientific calculation and analysis [1][2].

Computer-aided engineering (CAE) simulation technology helps practitioners generate, verify, validate and optimize the design solutions. In an aspect of product quality and defect prediction perspective, CAE simulation is a most technologically efficient and cost effective technology for analysis, prediction and evaluation of casting product quality and defects [3][4].

Figure 1. Image for the engine module with Oil Pan

CAE simulation of HPDC Process with Automobile part (Oil Pan) Hong-Kyu Kwon, Kwang-Kyu Seo

International Journal of Digital Content Technology and its Applications(JDCTA) Volume7, Number13, Sep 2013

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In this research, Computer Aided Engineering (CAE) was performed by using the simulation software (AnyCasting) in order to optimize casting design of an automobile part (Oil Pan on figure 1). Generally, the casting layout shown on figure 2 had been applied into Oil Pan. Oil Pan is assembled on the below of the crank case and its purpose is to collect oil after lubrication action conducted by oil pumper. The simulation results were analyzed and compared carefully in order to apply them into the production die-casting mold. During the mold filling, internal porosities caused by air entrap were predicted and reduced remarkably by the modification of the gate system and the configuration of flow junction zone. With the solidification analysis, internal porosities caused by the solidification shrinkage were predicted and reduced by the modification of the gate system.

Figure 2. Image for the general casting design of Oil Pan

2. Numerical Simulation

In this research, the commercial package (AnyCasting) was used to optimize a casting design

before fabricating a production HPDC mold. The software had been developed by AnyCasting Co., LTD. and employed a hybrid method mixing a PM (Porous Media) Method and a Cut-Cell Method that complements a drawback of the conventional FDM (finite difference method) rectangular mesh. The mold filling and solidification analysis are to be improved more accurate, and also calculation speed is improved more than 50% by decreasing mesh number [5]. Compared with several other commercial packages, AnyCasting has the ability to develop user friendly routines to describe dependent boundary conditions.

2.1. Modeling of the casting process

The action (flow of the melted metal) in the HPDC process is the high pressure generated by the fast

movement of plunge in the chamber. AnyCasting employed SOLA-VOF method to analyze the flow of the melted metal. The SOLA-VOF method had been designed for analyze three-dimensional fluid flow with the free surface and boundary [6][7]. The flow of the melted metal is considered any non-Newtonian and non-linear rheological properties. Making the modeling of the filling process, there are three phenomena (such as melt momentum balance, mass balance and energy balance) to be represented and modeled. The phenomena can be described by the following governing equations: Continuity equation:


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0)(

jj

Uxt

………………………..………….…………………………………...…….(1)

Momentum equation (Navier-stokes):

ij

i

jiij

ji g

x

U

xxUU

xU

t

)()()( ………………..…………………(2)

Energy equation:

Qx

T

xTUC

xTC

t jjjp

jp

)()()( ………..……..………………..…….….(3)

Volume of Fluid (VOF):

10,0

Fx

FU

t

F

jj

……..……..……………..…………………………………...…...(4)

where t is time, x is space, p is density, u is viscosity, g is gravity, Cp is heat capacity, λ is conductivity, F is volume, U is velocity, T is temperature, Ts is solid temperature, and Q is heat source.

3. Description of CAE simulation

The commercial package (AnyCasting) was used to optimize the casting design. In this case study,

the casting design on figure 3 for HPDC are created in Unigraphics (a commercial CAD/CAM package for product design and development), and converted into STL format. AnyCasting imports directly the generated STL models for filling and solidification simulation. Comparing with the casting design on figure 2, the casting design on figure 3 has the runner tails on the both side of the runner, which purpose is to contain the entrapped gas on the runner.

Figure 3. Casting design of Oil Pan: (A) Case 1; (B) Case 2

3.1. Pre-processing and simulation condition

The condition for CAE simulation is described on Table. ADC12 (AlSi9Cu3) was used for the cast

material and SKD 61 was for the die material. Initial and casting temperatures of the cast material were 6300C and 6000C, respectively. Initial and casting temperatures of the mold were 1800C and 2800C, respectively

The velocity of melt flow on Table 1 and 2 is an important parameter as it significantly affects the filling behavior and casting quality. The size and volume of the part on figure 3 were 328*444*174mm and 1,551,310mm3, respectively. With AnyCasting, the casting parts on figure 3 were meshed into


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10.6million elements. The model 1 on figure 3 has five runner ingates and seven overflow ingets. But the model 2 on figure 3 has six runner ingates and thirteen overflow ingets.

3.2. CAE simulation and post-process

With AnyCasting, casting simulation of each model had been conducted based on the given condition. On the filling of the casting process, the melted material flows along the runner and enters into the cavity. After the cavity is filled up, the extra melt, dirty metal and the air in the melt go into the overflow portion.

Figure 4 presents the filling process and shows simultaneously the Flow Front Temperature (FFT) and Melt Front Advancement (MFA) during the filling process. FFT shows the mid-stream temperature when the flow front reaches each point. Ideal result shows a uniform temperature distribution. MFA describes the movement status of the melt flow and the arrival sequence in the filling process. It also shows the melt position with the given percentage of the filling [8].

Figure 4. Simulation result of each case on the filling process

Table 1. Condition for CAE simulation

Part

Material ADC12

Liquidus Line 580℃

Solidus Line 515℃

Initial Temperature 630℃

Weight 4.35Kg

Mold Material SKD12

Initial Temperature 180℃

Plunger

Diameter 126mm

Slow Velocity 0.25 m/s

High Velocity 3 m/s

Table 2. Condition of Ingate on CAE simulation

Area Velocity

Case1 556,01 mm2 67.24m/s

Case2 476,85 mm2 78.41m/s


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With MFA, the flow phenomenon and porosity defect can be revealed and identified. Figure 4(A) shows the flow line that describes the change from slow velocity to high velocity. Figure 4(B) shows the flow direction and figure 4(C and D) show the areas that are the last area to be filled up and flow junction zone. In addition, the last area to be filled up and flow junction zone are usually the location of overflow which is the container of dirty melt and air [4][6]. Case 2 has better flow direction and uniform flow as shown on figure 4(B) and also has fewer areas for the entrapped air as shown on figure 4(C and D).

In the point of FFT, the flow temperature of case 2 has a better distribution as shown on figure 4(D). In each case, there seems to be no defects such as misrun and cold shut, etc. Figure 5 shows the flow tracking of each gate and also shows a filling portion of each gate with the different color. Case 2 with six gates has also better and uniform flow of each gate.

Figure 5. Simulation result for the flow tracking of each gate

Figure 6. Simulation result for the solidification of each case

The solidification is conducted after finishing the filling process. Figure 6 shows the simulation

result of solidification. The result is used to identify and determine areas of excessive shear heating in thick areas or excessive cooling in thin areas. Usually, the thick area contains a lot of heat and presents the hottest areas which are the last solidification area. Due to the solidification shrinkage, defects might be occurred on those areas [4][6]. Case 2 on figure 6 shows a uniform distribution according to the solidification results.

4. Result & Discussion

By comparing the simulation results in the points of the filling process and solidification, the casting

design with case 2 produces much better results. But there are some improvements existed on case 2 according to the simulation results. As shown on figure 7(a) with a red cycle, there are non balanced


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flow front advance and irregularities founded on the filling process. And also there are some flow returns and reversals as shown on figure 7(a) with yellow cycles. In order to solve those problems, a kind of the central pivot has to be added on the runner as shown on figure 7(b).

Figure 7. (A) Simulation result of the filling process for case 1; (B) Example for adding central pivot

Figure 8. Final casting design of oil pan

Based on the above discussion, new casting design for Oil Pan is created as shown on figure 8.

Comparing with the previous casting design on figure 3, the final casting design has long tails on the both side of the runner and central pivot on the middle of the runner shown on figure 8.

Simulation results with the final casting design had been conducted as shown on figure 9. According to the filling process on figure 9, some problems (such as flow balance, flow reversal, etc.) are improved a lot by adding the central pivot on the middle of the runner. The final casting design has a better flow direction and also better uniform flow comparing with the simulation results of case 2 shown on figure 4. In order to fabricate a production HPDC mold, the final casting design is applied into the mold layout for producing a better quality parts.

Figure 9. Simulation result of the final casting design on the filling process


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5. Conclusion

The automobile part (oil pan) is well known and complicated to achieve a good casting design.

Using CAE simulation with AnyCasting, the following results had been achieved: Comparing with the general casting design on figure 2, the long tails on both side of the runner are useful concept to absorb airs generated on the runner and also do not enter the airs into the cavity through the ingates. So, they reduce the porosity issues on the casted part. As shown on figure 8, the central pivot is useful concept to solve problems for flow balance and reversal. By adding it, flow direction is much better and also uniform flow is achieved comparing with other casting design. By applying the final casting design on figure 8 into a production HPDC mold, the simulation results on figure 9 has to be verified.

6. Acknowledgement

The authors greatly appreciate SAMWOO DIECAST CO., LTD. for the experimental

supports and implementations. And also thanks to JA mold & Technology CO. for the experimental supports.

7. References [1] Kwang-Kyu Seo, Hong-Kyu Kwon, “Simulation Study and Application on HPDC Process with

Automobile Part”, Advanced Material Research, TTP (Trans Tech Publications), vol.658, no.2013, pp.281-286, 2013.

[2] Hong-Kyu Kwon, Moo-Kyung Jang, “Case Study for Casting Design of Automobile Part (Gear Box) using CAE”, Journal of Society of Korea Industrial and Systems Engineering, Society of Korea Industrial and Systems Engineering, vol.35, no.4, pp.179-185, 2012.

[3] Liqiang Zhang, Luoxing Li, Biwu Zhu, “Simulation Study on the LPDC Process for Thin-Walled Aluminum Alloy Casting”, Materials and Manufacturing Processes, Taylor & Francis Group, vol.24, pp.1349-1353, 2009.

[4] Jin-Young Park, Eok-Soo Kim, Yong-Ho Park, Ik-Min Park, “Optimization of Casting Design for Automobile Transmission Gear Housing by 3D Filling and Solidification Simulation in Local Squeeze Diecasting Process”, Korean Journal of Materials Research, Korean Society of Materials Research, vol.16, no.11, pp.668-675, 2006.

[5] Information on http://anycastsoftware.com/en/software/fluid.php, 2013. [6] In-Sung Cho, Chun-Pyo Hong, “Numerical Modeling of Melt Flow in the Investment Mold by

SOLA-VOF”, Journal of the Korea Foundrymen’s Society, Korea Foundrymen’s Society, vol.12, no.5, pp.378-389, 1992.

[7] M. W. Fu, M. S. Young, “Simulation-enabled casting product defect prediction in die casting process”, International Journal of Production Research, Taylor & Francis, vol.47, no.18, pp.5203-5216, 2009.

[8] Information on http://www.ptonline.com/kc/articles/moldflow-and-simulation/flow-analysis, 2012.


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CAE simulation of HPDC Process with Automobile part (Oil · PDF fileCAE simulation of HPDC Process with Automobile part (Oil Pan) ... Computer Aided Engineering ... The result is used