Die Designing and Molten Metal Flow Analysis for Intermediate Flange

Eliminating Porosity Defects in HPDC: A Flow Analysis Case Study for Intermediate Flanges

This technical summary is based on the academic paper "DIE DESIGNING AND MOLTEN METAL FLOW ANALYSIS FOR INTERMEDIATE FLANGE" by K Maheswari and G Sureshkumar, published in the International Journal of Mechanical Engineering and Robotics Research (2013).

Keywords

Primary Keyword: Die Casting Defect Analysis
Secondary Keywords: Molten metal flow analysis, die design, intermediate flange, porosity defects, Magma software, Pro/E, casting simulation

Executive Summary

The Challenge: High-volume die castings for geometrically complex components, such as automotive intermediate flanges, are frequently rejected due to difficult-to-define defects like porosity and flow lines.
The Method: Researchers developed a complete 3D die assembly for an intermediate flange using Pro/E and then employed Magma simulation software to perform a detailed molten metal flow analysis.
The Key Breakthrough: The analysis revealed a direct correlation between molten metal velocity and casting integrity, identifying a specific velocity window (>11,000 cm/s and < 19,000 cm/s) that eliminates porosity and hot spot defects.
The Bottom Line: Proactively optimizing molten metal velocity through simulation is a critical and highly effective strategy for producing defect-free, high-quality die cast components and reducing scrap rates.

The Challenge: Why This Research Matters for HPDC Professionals

In the competitive world of high pressure die casting (HPDC), particularly in the automotive sector, quality and production rates are paramount. However, for complex parts like an intermediate flange, die casters often face a significant challenge: high rejection rates. These rejections are frequently caused by a range of defects including porosity, cold laps, flow lines, and mechanical cracks that may only become apparent after costly machining operations.

The core problem this research addresses is the ambiguity in diagnosing the root cause of these defects. Without a clear understanding of the fluid dynamics inside the die during the fractions of a second it takes to fill, process adjustments are often based on trial and error. This study was initiated to move beyond guesswork and establish a scientific, simulation-driven approach to designing a robust casting process that eliminates defects from the outset.

The Approach: Unpacking the Methodology

The researchers employed a two-stage digital engineering approach to design the die and optimize the casting process, ensuring a repeatable and high-quality outcome.

Method 1: 3D Die Design in Pro/E
Starting with a 2D customer drawing of the intermediate flange, the team used Pro/E software (now Creo) to develop a complete 3D model of the part. Subsequently, a full die assembly was designed, including all critical components that guide, shape, and eject the final casting. This assembly included the:
- Cavity and Core holders
- Runner and gate system
- Ejector plates and pins
- Guide pillars and bushes
- Sprue bush

Method 2: Molten Metal Flow Analysis with Magma Software
With the digital die assembly complete, the model was imported into Magma software for a comprehensive flow analysis. This simulation mimicked the real-world hot chamber die casting process. Key variables and materials were defined for the simulation:
- Casting Material: AlSi9Cu3 (a common aluminum alloy)
- Die Material: H13 tool steel
- Nitrogen Pressure: 80 bar
- Cooling Time: 9 seconds

The simulation analyzed how the molten aluminum filled the cavity, tracking its temperature and velocity to predict the formation of defects.

The Breakthrough: Key Findings & Data

The simulation was run under two different sets of process parameters, leading to a critical discovery about the impact of injection velocity on part quality.

Finding 1: Low-Velocity Injection Leads to Porosity Defects

The initial simulation was run with a set of standard parameters, including a fast shot velocity of 1.25 m/s, which resulted in an ingate velocity of 8,617 cm/s. The analysis showed that at this velocity, the molten metal did not fill the cavity correctly. As shown in the simulation results (referenced as Figure 13 in the paper), this incomplete and turbulent filling led directly to the formation of porosity defects during solidification. Furthermore, the simulation identified a hot spot (Figure 15), a localized area that cools much slower than the rest of the casting, which is a primary cause of shrinkage porosity.

Finding 2: The Optimal Velocity Window for a Defect-Free Casting

The researchers then adjusted the process parameters, most notably increasing the fast shot velocity to 2.8 m/s. This change significantly altered the filling dynamics. The study's conclusion established a clear, defect-free processing window:
- A molten metal velocity between >11,000 cm/s and < 19,000 cm/s is required to produce a defect-free part.

As illustrated in the paper's simulation results for the optimized process (Figure 17), the die cavity fills completely and uniformly within this velocity range. This eliminates the conditions that cause porosity and hot spots, resulting in a sound, high-quality casting. The final molten metal temperature at the end of the fill was 680 °C, ensuring sufficient fluidity to prevent cold laps.

Practical Implications for R&D and Operations

For Process Engineers: This study suggests that adjusting the shot profile, specifically the fast shot velocity, is a primary tool for controlling ingate velocity. Targeting a velocity greater than 11,000 cm/s may be a crucial step in resolving persistent porosity issues in similar complex components.
For Quality Control Teams: The data in the paper's Figure 13 (Porosity Defect) and Figure 17 (Defectless Die) provides a clear visual correlation between process parameters and casting defects. This can inform root cause analysis and help validate process improvements.
For Design Engineers: The findings underscore the critical importance of runner and gate design. These features are not just pathways for metal but are essential tools for controlling fill velocity and direction. Using flow simulation software during the die design phase is essential to engineer a process that avoids defects.

Paper Details

DIE DESIGNING AND MOLTEN METAL FLOW ANALYSIS FOR INTERMEDIATE FLANGE

1. Overview:

Title: DIE DESIGNING AND MOLTEN METAL FLOW ANALYSIS FOR INTERMEDIATE FLANGE
Author: K Maheswari and G Sureshkumar
Year of publication: 2013
Journal/academic society of publication: International Journal of Mechanical Engineering and Robotics Research (Vol. 2, No. 4, October 2013)
Keywords: Die design, Metal flow analysis, Hot chamber die pressure casting

2. Abstract:

The die casting process is an effective near net shape manufacturing process for producing geometrically complex components which require a high production rate and an excellent surface finish. However, one problem area has been indicated that die castings are often rejected by die casters as a result of being machined, and the defects for causing the rejections are frequently not clearly defined. And also the common defects found in these defective castings were categorized as follows: porosity, cold laps, flow lines, aluminum oxide inclusions, lubricant or mold coating inclusions, and mechanical cracks. To develop 3-D of intermediate flange as per the customer requirement using 2-D drawing in Pro/E. To Develop Die for intermediate flange {core, cavity, runner and gate, etc.}, using Pro/E software. Make molten metal flow analysis for this Die using Magma software.

3. Introduction:

Casting is a manufacturing process where a liquid material is poured into a mold with a hollow cavity of a desired shape and allowed to solidify. Die casting is a specific type of casting that produces complex metal parts using reusable molds, called dies. The process involves melting a non-ferrous alloy (e.g., aluminum, zinc) and injecting it under high pressure into the die. There are two primary machine types: hot chamber and cold chamber. The process is economical for large quantities of complex, high-tolerance parts, making it vital for industries like automotive. However, any unwanted deviation in the cast product results in a defect. Major defects likely to occur include hot tearing, blow holes, porosity, pouring metal defects, and pin holes.

4. Summary of the study:

Background of the research topic:

The research addresses a persistent problem in the die casting industry: the rejection of complex components due to casting defects that are often not clearly defined. These defects, such as porosity, cold laps, and flow lines, compromise the structural integrity and surface finish of the final product.

Status of previous research:

The paper does not provide a detailed literature review but grounds its work in established knowledge of die casting principles and common defects as defined by sources such as Allsop and Kennedy (1983). The study applies modern computational tools to solve these well-known industrial problems.

Purpose of the study:

The primary objectives of the study were twofold:
1. To design a complete 3D model of an intermediate flange and its corresponding die assembly (including core, cavity, runner, and gate) using Pro/E software.
2. To perform a molten metal flow analysis on the designed die using Magma software to understand the filling dynamics and optimize the process to eliminate casting defects.

Core study:

The core of the study is a design and simulation case study for an intermediate flange component. It involves the creation of a digital twin of the die and the casting process. The study systematically compares two different sets of process parameters to analyze the effect of molten metal velocity on the formation of defects like porosity and hot spots. The goal is to identify an optimal processing window that yields a defect-free casting.

5. Research Methodology

Research Design:

The study follows a computational design and analysis methodology. It begins with the geometric design of the component and die using CAD software and proceeds to a simulation phase using specialized casting analysis software to model the physical process of die filling and solidification.

Data Collection and Analysis Methods:

Pro/E Software: Used for the 3D modeling of the intermediate flange and all components of the die assembly, such as the cavity holder, core holder, ejector pins, guide pillars, and sprue bush.
Magma Software: Used to conduct the molten metal flow analysis. The software simulates the injection of molten AlSi9Cu3 alloy into the H13 steel die, predicting outcomes such as filling pattern, velocity distribution, temperature variation, and the location of potential defects like porosity and hot spots.

Research Topics and Scope:

The research is focused specifically on the die design and process optimization for a single part: an automotive intermediate flange. The scope is limited to a hot chamber die casting process using AlSi9Cu3 alloy. The analysis centers on the relationship between injection process parameters (primarily shot velocity) and the resulting casting quality, with a focus on eliminating porosity and hot spot defects.

6. Key Results:

Key Results:

An initial simulation using parameters from Table 1 (plunger diameter 80 mm, fast shot velocity 1.25 m/s) resulted in an ingate velocity of 86.17 m/s (8617 cm/s). This condition led to porosity defects (Figure 13) and the formation of a hot spot during solidification (Figure 15). The minimum metal temperature at the end of mould filling was 644 °C.
A second simulation was performed with modified parameters from Table 2 (plunger diameter 70 mm, fast shot velocity 2.8 m/s).
The study concludes that porosity defects occur in the velocity range of 700 cm/s to 10,000 cm/s.
A defect-free die casting is achieved when the molten metal velocity is within the range of >11,000 cm/s and < 19,000 cm/s.
For the defect-free process, the maximum molten metal temperature at the end of mould filling is 680 °C.

Figure Name List:

Figure 1: Intermediate Flange
Figure 2: Extrude Feature
Figure 3: Rib Feature
Figure 4: Cavity Holder
Figure 5: Flange Cavity
Figure 6: Sprue Bush
Figure 7: Side Core
Figure 8: Ejector Pins
Figure 9: Guide Pillers
Figure 10: Assembly of Flange Die
Fgure 11: Varying Metal Temparatures
Figure 12: Pouring Rate
Figure 13: Porosity Defect
Figure 14: Poring Rate
Figure 15: Hot Spot Defect
Figure 16: Pouring Rate
Figure 17: Defectless Die

7. Conclusion:

The maximum molten metal temperature at the end of the mould filling is 680 °C. In the die casting process the die will maintain at 150 °C. The porosity defect occurs at a velocity range between 700 cm/s to 10000 cm/s. The die is defectless when the velocity ranges between >11000 cm/s and < 19000 cm/s.

8. References:

Allsop D F and Kennedy D (1983), “Pressure Die Casting, Part 2: The Technology of the Casting and the Die", Pergamon Press, Oxford.
Colbourn Charles J and Dinitz Jeffrey H (2007), Handbook of Combinatorial Designs, 2nd Edition, Chapman & Hall/CRC, Boca Raton, ISBN 1-58488-506-8.
Detroit M (1955), Die Design Handbook, ASMTE.
Ghosh and Mallik (2010), Manufacturing Science, 2nd Edition, EWP Press.
Hernandez J, Lopez J, Faura F and Trapaga G (2000), “Shot Sleeve Wave Dynamics in the Slow Phase of Die Casting Injection”, ASME, Fluid Eng., Vol. 122, pp. 349-356.
John L Jorstad (September 2006), "Aluminum Future Technology in Die Casting", Die Casting Engineering, pp. 18-25, Archived from the Original on 11-12-2010.
Kosec B, Kosec L and Kopaè J (2001), "Analysis of Casting Die Failures”, Engineering Failure Analysis, Vol. 8, pp. 355-359.
Liu Wen-Hai (2009-10-08), “The Progress and Trends of Die Casting Process and Application”, Archived from the Original on 2010-10-19, Retrieved 2010-10-19.

Expert Q&A: Your Top Questions Answered

Q1: What were the key process parameters changed between the defective and defect-free simulations?

A1: The paper presents two tables of input parameters. The most significant changes were decreasing the plunger diameter from 80 mm to 70 mm and increasing the fast shot velocity from 1.25 m/s to 2.8 m/s. These adjustments were made to increase the molten metal's velocity as it entered the cavity through the ingate, which proved to be the critical factor in eliminating defects.

Q2: Why were AlSi9Cu3 alloy and H13 tool steel chosen for this study?

A2: The paper specifies AlSi9Cu3 as the casting material and H13 as the die material. While the paper doesn't explicitly state the reasons for this choice, these are standard, widely-used materials in the HPDC industry, especially for automotive components. AlSi9Cu3 offers a good combination of fluidity, strength, and pressure tightness, while H13 is a hot-work tool steel known for its excellent resistance to thermal fatigue, making it ideal for die casting dies.

Q3: The paper mentions both "porosity" and "hot spot" defects. How are they related?

A3: The Magma software used in the study simulates both the filling and solidification phases. Porosity was identified in the filling analysis (Figure 13) as voids caused by trapped air or incomplete filling. The hot spot (Figure 15) was identified in the solidification analysis. A hot spot is a region that remains liquid much longer than its surroundings, and as it finally cools and shrinks, it can create a vacuum or void known as shrinkage porosity if not properly fed with molten metal.

Q4: What is the practical significance of defining a velocity "window" (e.g., >11,000 and <19,000 cm/s)?

A4: Defining a process window is crucial for robust manufacturing. A velocity that is too low (<10,000 cm/s) leads to premature solidification, flow lines, and porosity. Conversely, an excessively high velocity (though not explicitly shown as defective in this study, it's a known industry issue) can cause die erosion and excessive turbulence. The identified window provides process engineers with a clear target range to ensure consistent, high-quality production.

Q5: How does the die design itself influence the final molten metal velocity?

A5: The die design, particularly the runner and ingate system, is fundamentally responsible for controlling the metal velocity. The cross-sectional area of the ingate (the narrow entry point into the cavity) acts like a nozzle. For a given shot velocity from the machine, a smaller ingate area will result in a higher metal velocity entering the cavity. Therefore, die designers must use simulation to engineer the runner and gate to achieve the target velocity identified in this study.

Conclusion: Paving the Way for Higher Quality and Productivity

This research provides a clear and actionable framework for overcoming common challenges in high pressure die casting. By moving from a reactive, trial-and-error approach to a proactive, simulation-driven one, die casters can effectively solve complex quality issues. The study demonstrates that a thorough Die Casting Defect Analysis using modern software can pinpoint the root cause of defects like porosity and identify a precise process window for their elimination. The key takeaway is that controlling molten metal velocity is not just a theoretical concept but a practical lever for dramatically improving part quality and reducing scrap.

At CASTMAN, we are committed to applying the latest industry research to help our customers achieve higher productivity and quality. If the challenges discussed in this paper align with your operational goals, contact our engineering team to explore how these principles can be implemented in your components.

Copyright Information

This content is a summary and analysis based on the paper "DIE DESIGNING AND MOLTEN METAL FLOW ANALYSIS FOR INTERMEDIATE FLANGE" by "K Maheswari and G Sureshkumar".

Source: The paper was published in the International Journal of Mechanical Engineering and Robotics Research, Vol. 2, No. 4, October 2013. A direct link is not provided in the document, but it can be found via the journal's archives at www.ijmerr.com.

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Tags: CAD; , Die casting; , High pressure die casting; , High pressure die casting (HPDC); , Quality Control; , Review; , STEP; , aluminum alloy