Optimizing the Aluminum Alloy Die Casting Process for Complex Automotive Gearbox Housings
This technical summary is based on the academic paper "铝合金变速箱外壳压铸模设计及工艺分析 (Die Casting Die Design and Process Analysis of Aluminum Alloy Gearbox Housing)" by 周 倩 (ZHOU Qian), 任 浩 (REN Hao), 王 俊有 (WANG Jun-you), 黄 明宇 (HUANG Ming-yu), published in 压力铸造 (FOUNDRY) (2021).
Keywords
- Primary Keyword: Aluminum Alloy Die Casting Process
- Secondary Keywords: HPDC, Gearbox Housing, Die Casting Defects, Process Parameters, Die Design, Porosity Reduction, Gating System Design
Executive Summary
- The Challenge: Complex aluminum alloy castings, such as automotive gearbox housings, frequently suffer from defects like porosity, shrinkage, and cold shuts during the die-casting filling process, compromising quality and increasing costs.
- The Method: The study conducted a comprehensive analysis of a gearbox housing, designing a specialized die-casting die with optimized gating, cooling, and core-pulling systems, followed by systematic testing to determine the ideal process parameters.
- The Key Breakthrough: A specific set of optimized process parameters was identified, resulting in superior casting quality, including a fixed die temperature of 200°C, a moving die temperature of 220°C, a fast injection speed of 4.5 m/s, and an inner gate speed of 48 m/s.
- The Bottom Line: A well-designed die combined with precisely controlled process parameters can significantly improve production efficiency, increase the yield of qualified parts, and reduce overall manufacturing costs for complex aluminum alloy components.
The Challenge: Why This Research Matters for HPDC Professionals
In the high-stakes world of automotive manufacturing, the demand for lightweight, high-performance components is relentless. Aluminum alloys are a primary choice, but their die casting presents significant challenges, especially for intricate parts like gearbox housings. These components are characterized by complex geometries, varying wall thicknesses, and numerous oil passages, making them highly susceptible to defects such as porosity, shrinkage, cold shuts, and cracks.
These defects not only lead to high scrap rates but also compromise the structural integrity and performance of the final product, failing critical pressure leak tests. The industry needs a reliable, systematic approach to overcome these issues. This research addresses this critical need by providing a detailed methodology for designing the die and optimizing the process to produce high-quality, defect-free gearbox housings consistently.
The Approach: Unpacking the Methodology
The researchers took a multi-faceted approach, focusing on both die design and process parameter optimization to solve the casting defect problem.
Method 1: Comprehensive Die Design
The foundation of the study was a meticulous die design tailored to the complex geometry of the gearbox housing.
* Material: The casting material was AlSi9Cu3, an aluminum alloy with a 0.6% shrinkage rate.
* Parting Line & Core Pulling: Due to the component's complex internal and external features, a multi-directional parting line strategy was established using upper, lower, and right-side slides (core pullers) to form features not aligned with the primary die opening direction (as shown in Figure 3). Hydraulic cylinders were integrated into the moving die for this purpose.
* Gating and Runner System: The design of the gating system was crucial for ensuring smooth metal flow and preventing turbulence. The cross-sectional area of the inner gate was calculated to be 1,441 mm² to achieve a target fill time of 0.07 seconds. The runner system was designed to progressively decrease in cross-section to maintain pressure and velocity.
* Cooling System: An intricate cooling system was designed for both the fixed and moving dies (Figure 4). It included standard water cooling channels and targeted high-pressure spot cooling in areas with longer solidification times to achieve a balanced thermal state within the die.
Method 2: Systematic Process Parameter Optimization
With the die designed, the team conducted a series of experiments to identify the optimal process parameters using a 3200T Bühler die-casting machine.
* Key Variables: The primary variables tested were die preheating temperature, molten aluminum pouring temperature, and injection speeds (slow and fast).
* Orthogonal Testing: Multiple trials were conducted by varying one parameter at a time to isolate its effect on casting quality. For example, die preheating temperatures were tested at 140, 160, 180, 200, and 220°C, while pouring temperatures were tested from 650°C to 700°C.
The Breakthrough: Key Findings & Data
The systematic testing yielded a precise set of process parameters that produced consistently high-quality castings, free from common defects and meeting strict technical requirements.
Finding 1: Optimal Thermal Management is Critical for Defect Prevention
The study confirmed that controlling the temperature of both the die and the molten aluminum is paramount.
* Die Temperature: The optimal die preheating temperature was found to be 200°C for the fixed die and 220°C for the moving die. Temperatures below this range led to increased shrinkage stress and cracking, while higher temperatures unnecessarily prolonged the cycle time.
* Pouring Temperature: The ideal pouring temperature for the AlSi9Cu3 alloy was determined to be 670°C. Lower temperatures resulted in incomplete filling and cold shuts, whereas higher temperatures caused excessive shrinkage, gas porosity, and coarse grain structures.
Finding 2: Precise Injection Speed Control Defines Casting Integrity
The velocity of the molten metal during filling directly impacts the final quality. The research identified a specific two-stage injection profile for superior results.
* Slow Injection Speed: The optimal slow injection speed was 0.18 m/s. This initial phase ensures that air is smoothly pushed out of the shot sleeve and runner system without being trapped in the metal.
* Fast Injection Speed: The optimal fast injection speed was 4.5 m/s. This high speed ensures the cavity is filled rapidly before solidification begins, preventing cold shuts. Based on this, the inner gate velocity was calculated to be 48 m/s, ensuring high-density filling of the complex geometry.
* Dwell Time: A die-closed dwell time of 30 seconds was established to allow for complete solidification before ejection.
Practical Implications for R&D and Operations
- For Process Engineers: This study provides a validated set of starting parameters (die temperature, pouring temperature, injection speeds) for complex AlSi9Cu3 gearbox housings. It suggests that a balanced thermal profile, achieved through targeted cooling and precise preheating, is key to reducing defects like cracks and shrinkage.
- For Quality Control Teams: The data in the paper demonstrates a direct link between specific process parameters and final part quality. The finding that an inner gate velocity of 48 m/s produces sound castings can inform simulation validation and new quality inspection criteria for porosity, which was required to be under 5% with no single pore larger than 3 mm.
- For Design Engineers: The findings on the necessity of a multi-slide core-pulling system (Figure 3) and targeted spot cooling highlight the importance of considering manufacturability early in the design phase. The design of the gating and venting system, which should have a vent area at least 50% of the gate area, is a critical takeaway for ensuring gas can escape the cavity effectively.
Paper Details
铝合金变速箱外壳压铸模设计及工艺分析 (Die Casting Die Design and Process Analysis of Aluminum Alloy Gearbox Housing)
1. Overview:
- Title: 铝合金变速箱外壳压铸模设计及工艺分析 (Die Casting Die Design and Process Analysis of Aluminum Alloy Gearbox Housing)
- Author: 周 倩 (ZHOU Qian), 任 浩 (REN Hao), 王 俊有 (WANG Jun-you), 黄 明宇 (HUANG Ming-yu)
- Year of publication: 2021
- Journal/academic society of publication: 压力铸造 (FOUNDRY), Vol. 70, No. 3
- Keywords: 铝合金 (aluminum alloy); 压铸模具 (die casting die); 工艺分析 (process analysis); 压铸生产 (die casting production)
2. Abstract:
In response to the common defects of porosity, shrinkage, and cold shuts that occur during the die-casting filling process of aluminum alloy castings, this paper takes an automotive aluminum alloy gearbox housing as an example. It analyzes the structural characteristics of the gearbox housing and designs its gating system, cooling system, and core-pulling structure. The optimal process parameters were determined through experiments and analysis. Finally, the rationality of the process plan was verified through actual die-casting production. The results show that when the fixed die temperature is 200°C, the moving die temperature is 220°C, the aluminum pouring temperature is 670°C, the slow injection speed is 0.18 m/s, the fast injection speed is 4.5 m/s, the inner gate injection speed is 48 m/s, and the die opening time is 30 s, the casting quality is superior. A reasonable die-casting process design not only improves production efficiency and product qualification rate but also simplifies the die design and manufacturing process, reducing die development costs.
3. Introduction:
Aluminum alloys possess advantages such as low density, high strength, corrosion resistance, wear resistance, good thermal conductivity, ease of processing, and aesthetic appearance, making them widely used in automotive, aerospace, machinery, and communication fields. Die casting is a primary forming method for aluminum alloys, accounting for 49% of all aluminum alloy products. Die casting offers benefits like good product quality, high dimensional accuracy, and suitability for mass production. However, during production, physical changes like thermal expansion and contraction inevitably lead to defects such as porosity, shrinkage, cold shuts, and cracks, which significantly impact the qualification rate of aluminum alloy castings. As the automotive industry's requirements for aluminum alloy products become increasingly stringent, the casting industry must continuously optimize the die-casting process to meet performance demands.
4. Summary of the study:
Background of the research topic:
The research addresses the persistent issue of casting defects in the high-pressure die casting of complex aluminum alloy components for the automotive sector.
Status of previous research:
Previous research has established die casting as a dominant method for producing aluminum alloy parts. However, managing defects like porosity and shrinkage remains a significant challenge, especially for parts with complex geometries and strict performance requirements like leak-tightness.
Purpose of the study:
The study aims to develop a systematic approach to die design and process optimization for a new, complex automotive aluminum alloy gearbox housing to eliminate common casting defects and ensure the final product meets stringent quality standards.
Core study:
The core of the study involves a detailed analysis of the gearbox housing's structure. Based on this analysis, a complete die-casting die was designed, including the parting line, gating system, venting system, cooling system, and core-pulling mechanisms. Subsequently, a series of experiments were conducted to determine the optimal process parameters for die temperature, pouring temperature, and injection speeds to achieve defect-free castings.
5. Research Methodology
Research Design:
The research followed a sequential design-and-test methodology. First, a detailed product structure analysis was performed on the AlSi9Cu3 gearbox housing. Second, a complete die-casting mold was designed to accommodate the part's complexity. Third, an experimental phase was conducted using a 3200T die-casting machine to systematically test and optimize key process parameters. Finally, the optimized process was validated through production runs.
Data Collection and Analysis Methods:
Data was collected through a series of controlled experiments (orthogonal testing) where process parameters were varied. The resulting castings were analyzed for defects and quality. The optimal parameters were determined by comparing the outcomes of these trials. Calculations were used to determine the required inner gate area, runner design, and clamping force.
Research Topics and Scope:
The research focuses on a single component: a newly developed automotive aluminum alloy gearbox housing. The scope includes:
- Product structural analysis.
- Die design, including parting line determination, gating and runner system, cooling system, and hydraulic core-pulling mechanisms.
- Selection of a suitable die-casting machine (clamping force calculation).
- Optimization of process parameters: die preheating temperature, pouring temperature, slow and fast injection speeds, and dwell time.
6. Key Results:
Key Results:
- Optimal Die Temperature: Fixed die at 200°C, Moving die at 220°C.
- Optimal Pouring Temperature: 670°C.
- Optimal Injection Speeds: Slow injection at 0.18 m/s, Fast injection at 4.5 m/s.
- Resulting Inner Gate Speed: 48 m/s.
- Optimal Dwell Time: 30 s.
- Casting Quality: The process yielded castings with good surface finish, free of cracks, porosity, and cold shuts, which passed subsequent high and low-pressure leak tests after machining.
Figure Name List:
- 图1 产品结构图
- 图2 产品壁厚分析图
- 图3 分型面图
- 图4 动定模冷却水路图
- 图5 含冷却系统的产品浇注系统图
- 图6 铸件外观结构图
- 图7 压铸模具平面布置图
- 图8 铝合金变速箱外壳压铸件
7. Conclusion:
The study reached three main conclusions:
1. Based on the structural characteristics of the aluminum alloy gearbox housing, a comprehensive die design was developed, including the determination of the parting line, and the design of the gating, cooling, and core-pulling systems. The structure of the die-casting mold has a significant impact on the forming quality of the casting.
2. Through multiple experiments, the optimal process parameters were determined to be: fixed die temperature of 200°C, moving die temperature of 220°C; molten aluminum pouring temperature of 670°C; slow injection speed of 0.18 m/s, fast injection speed of 4.5 m/s; inner gate injection speed of 48 m/s; and a dwell time of 30 s. Under these conditions, the casting quality was superior and met technical requirements.
3. By optimizing the die-casting process for issues like porosity, cold shuts, and leakage in aluminum alloy castings, it is possible to significantly reduce production costs, shorten the production cycle, and increase economic benefits.
8. References:
- [1] 李荣德, 于海朋, 袁晓光. 压铸技术及压铸合金的发展与应用[J]. 机械工程学报, 2003 (11): 68-73.
- [2] 樊振中, 袁文全, 王端志, 等. 压铸铝合金研究现状与未来发展趋势[J]. 铸造, 2020, 69 (2): 159-166.
- [3] 倪红军, 陈科, 张福豹, 等. 压铸铝合金研究现状及展望[J]. 轻金属, 2019 (3): 51-55.
- [4] 张正来, 夏天, 冯光明, 等. 多级涡轮增压器壳体压铸模具设计[J]. 铸造, 2018, 67 (9): 787-789.
- [5] MEHTEDIME, MANCIA T, BUONADONNA P, et al. Design optimization of gate system on high pressure die casting of AlSi13Fe alloy by means of finite element simulations [J]. Procedia CIRP, 2020, 88: 509-514.
- [6] 潘宪曾. 压铸模设计手册 [M]. 3版. 北京: 机械工业出版社, 2006.
- [7] ZYSKA A, KONOPKA Z, GIEWKA, M, et al. Porosity of castings produced by the vacuum assisted pressure die casting method [J]. Archives of Foundry Engineering, 2015, 15 (1): 125-130.
- [8] 张国强, 赵占西, 勾健, 等. 壳体压铸工艺设计及优化[J]. 铸造, 2020, 69 (5): 501-505.
- [9] 李建宇, 管胜敏, 吴树森, 等. 大型复杂离合器壳体高致密化压铸[J]. 铸造, 2020, 69 (11): 1198-1202.
- [10] 万晓萌, 张笑, 王晔, 等. 大型复杂铝合金变速箱壳体压铸模设计[J]. 特种铸造及有色合金, 2020, 40 (8): 854-856.
- [11] 陈位铭, 金胜灿. 铝合金压铸工艺的数值模拟及应用[J]. 汽车技术, 2005 (6): 32-35.
- [12] 崔黎明. 铝合金压铸件缺陷分析及成型工艺优化[D]. 武汉: 武汉理工大学, 2007.
Expert Q&A: Your Top Questions Answered
Q1: Why was a differential die temperature (200°C fixed, 220°C moving) chosen?
A1: The paper states that the general preheating temperature should be above 180°C, especially for complex or thin-walled parts. The choice of a slightly higher temperature for the moving die (220°C) is a common practice to ensure the casting remains on the moving half upon die opening, which facilitates ejection. This differential helps control solidification and ensures a smooth production cycle.
Q2: The paper mentions a fast injection speed of 4.5 m/s. How was this specific value determined to be optimal?
A2: The paper states that this value was determined through multiple experiments. A fast injection speed is necessary to fill the cavity before the molten aluminum begins to solidify, which prevents defects like cold shuts and flow marks. Speeds that are too low result in poor filling, while the optimal speed of 4.5 m/s was found to provide the best balance for complete filling and good surface quality for this specific part geometry.
Q3: What was the rationale for using hydraulic core pullers on the moving die?
A3: The gearbox housing has several undercuts and side features, specifically the two boxed areas in Figure 6, that are not in the line of draw of the main die opening. To form these features, side-action cores (slides) are necessary. Placing these hydraulic core-pulling mechanisms on the moving die half simplifies the die structure and allows for a clear sequence of operations: the die opens, the cores retract, and then the part is ejected.
Q4: The paper emphasizes the importance of the venting system. What specific design principle was followed?
A4: The paper provides a key design guideline for the venting system. It states that in an ideal state, the cross-sectional area of the vents (排气槽) should be at least 50% of the cross-sectional area of the inner gate (内浇道). This ensures that the air and initial cold metal front trapped in the cavity have an adequate path to escape, which is critical for preventing gas porosity.
Q5: How was the required clamping force and the 3200T machine size determined?
A5: The paper outlines the calculation for clamping force. It depends on the projected area of the casting, runner, and overflows on the parting line, multiplied by the specific injection pressure (chosen as 90 MPa for this high-integrity part). An additional calculation was made for the force on the angled faces of the side cores. A safety factor of 1.2 was then applied to the total calculated force, leading to the selection of a 3200T machine to ensure the die remains securely closed during injection.
Conclusion: Paving the Way for Higher Quality and Productivity
The challenge of producing defect-free, complex aluminum castings is a constant battle against porosity, shrinkage, and incomplete filling. This research demonstrates that a successful outcome hinges on a holistic approach that integrates intelligent die design with a precisely optimized Aluminum Alloy Die Casting Process. By establishing the ideal parameters for temperature, speed, and pressure, the study provides a clear roadmap for transforming a challenging component into a high-quality, reliable product. The principles of balanced thermal management, controlled metal flow, and robust die mechanics are key takeaways for any team looking to elevate their casting capabilities.
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 "铝合金变速箱外壳压铸模设计及工艺分析 (Die Casting Die Design and Process Analysis of Aluminum Alloy Gearbox Housing)" by "周 倩 (ZHOU Qian), et al.".
Source: The paper was published in 压力铸造 (FOUNDRY), 2021, 70(3): 301-305.
This material is for informational purposes only. Unauthorized commercial use is prohibited.
Copyright © 2025 CASTMAN. All rights reserved.