1. Overview:

Title: Benchmarking aluminium die casting operations
Author: A. Tharumarajah
Year of Publication: 2008
Journal/Conference: Resources, Conservation and Recycling 52 (2008) 1185-1189
Keywords: Die casting, Aluminium, Benchmarking, Recycling, Environment

2. Research Background:

Increasing demand for aluminium die cast components in the global automotive market presents significant opportunities and challenges for the Australian industry, which is striving to position itself as a global player. To address these challenges, the industry is continuously seeking to improve overall resource efficiency to reduce costs and greenhouse gas (GHG) emissions. High-Pressure Die Casting (HPDC) processes, in particular, can be energy and water-intensive, with substantial losses of high-cost aluminium in the form of trim wastes.
Existing research has primarily focused on traditional determinants such as cost, delivery, and quality. However, growing concerns about environmental burdens from manufacturing, especially GHG emissions, have highlighted the need to reduce GHG emissions.
This necessitates research to benchmark resource flows and waste generation in the aluminium die casting industry and to evaluate the current status in terms of resource efficiency, cost, and GHG impact. A deeper analysis of in-house aluminium recycling flows, generally considered good practice, is required to uncover potential hidden inefficiencies and suggest improvements.

3. Research Purpose and Research Questions:

Research Purpose: This study aims to benchmark the usage of aluminium and key operating resources in a representative aluminium HPDC facility, accounting for approximately 10% of the Australian market. The goal is to evaluate the current status in terms of resource efficiency, cost, and GHG emissions and to identify areas for improvement. Specifically, it seeks to reveal hidden inefficiencies through an in-depth analysis of in-house aluminium recycling flows and propose improvement measures.
Core Research Questions:
- How are the flows of resources (aluminium, water, electricity, gas, die-lube) and waste generation structured in the aluminium HPDC process?
- What is the impact of in-house aluminium recycling flows on resource efficiency, cost, and GHG emissions?
- What are the technical and systemic improvement measures to enhance resource efficiency and environmental performance in the aluminium HPDC process?
Research Hypotheses: While the paper does not explicitly state research hypotheses, it implicitly aims to verify the following:
- In-house aluminium recycling, while seemingly improving resource efficiency, may actually hinder overall resource efficiency and increase costs and GHG emissions.
- Improving resource efficiency and environmental performance in aluminium HPDC processes requires not only technical improvements but also systemic improvements in areas such as training, maintenance, quality assurance, and shop-floor information and management systems.

4. Research Methodology:

Research Design: Case Study. A single representative aluminium HPDC facility in Australia was selected for in-depth analysis.
Data Collection Methods:
- Material Flow Analysis (MFA): Product, recycling, and waste flows in the HPDC process were modeled. Inputs and outputs of aluminium and key operating resources (water, electricity, gas, die-lube) were measured and estimated.
- Field Data Collection: Daily production data and design data from April 2006 to March 2007 were collected and used for analysis. Aluminium flows were tracked at the part level, and electricity consumption was categorized by process or equipment.
- Cost and GHG Impact Calculation: Data analysis was performed to calculate direct costs, added costs, and GHG impacts.
Analysis Methods:
- Resource Efficiency Indicator Calculation: Indicators such as 1st pass material efficiency, operational material efficiency, and resource cost efficiency were calculated to evaluate resource use efficiency.
- Cost Analysis: Costs related to aluminium waste were categorized into added cost of waste and cost of handling and transport of waste. The ratio of waste-related costs to manufacturing costs was calculated.
- GHG Impact Assessment: GHG emissions from aluminium production and operating resource usage were calculated, and the GHG emission contribution of each resource was analyzed.
Research Subjects and Scope:
- Research Subject: A representative aluminium HPDC facility in Australia (accounting for approximately 10% of the Australian market). The facility possesses various HPDC machines (800T x 5, 1250T x 4, 2250T x 2, 2500T x 2).
- Research Scope: The entire process from the input of aluminium (ADC12 alloy) and key operating resources (water, electricity, gas, die-lube) to product shipment in the HPDC process. In-house aluminium recycling flows were the primary focus of the analysis.

5. Key Research Findings:

Core Findings:
- In-house aluminium recycling, while commonly considered good practice, actually generates significant hidden aluminium losses, which can be a major cause of increased costs and GHG emissions.
- Although the 1st pass material efficiency was high at 93.87%, the operational material efficiency, including in-house recycling, significantly decreased to 47.7%, indicating substantial aluminium losses during the process.
- Various forms of aluminium losses occur, including melting losses, process losses (warm-ups, mis-runs, etc.), and yield losses (runners, biscuits, flashings, etc.). Yield losses account for the largest proportion of aluminium losses.
- Costs related to aluminium waste account for 44.1% of the total manufacturing cost. Yield loss-related costs are the highest at 29.5%, followed by process loss-related costs at 13.1%.
- Aluminium losses also significantly impact GHG emissions, accounting for approximately 49% of total GHG emissions.
- Among the major operating resources, electricity and water have high usage and GHG emission contributions. Electricity accounts for approximately 51% and water for approximately 37% of total GHG emissions.
Statistical/Qualitative Analysis Results:
- 1st pass material efficiency: 93.87%
- Operational material efficiency: 47.7%
- Cost related to aluminium waste: 44.1% of total manufacturing cost
  - Process losses: 13.1%
  - Yield losses: 29.5%
  - Waste sold: 0.25%
  - Cost of additional Al: 1.46%
- GHG emissions due to aluminium losses: Approximately 49% of total GHG emissions
- GHG emission contribution by operating resource:
  - Electricity: Approximately 51%
  - Water: Approximately 37%
  - Natural gas and die-lube: Negligible levels
- Resource usage intensity (per tonne of aluminium sold):
  - Electricity: 1.54 kWh/tonne
  - Natural gas: 0.02 MJ/tonne
  - Die-lube: 0.01 L/tonne
  - Water: 4.32 L/tonne
Data Interpretation:
- The high 1st pass material efficiency but low operational material efficiency indicates significant losses in the in-house recycling process, suggesting hidden inefficiencies.
- The fact that aluminium waste-related costs account for nearly half of the manufacturing cost emphasizes the importance of managing aluminium losses for cost reduction.
- GHG emission analysis results show that reducing aluminium losses and improving energy efficiency can significantly reduce environmental impact.
Figure Name List:
- Fig. 1. Flow of aluminium and others through HPDC process.
- Fig. 2. Electricity consumption by category of use.
- Fig. 3. Primary and secondary factors influencing part quality and shop-floor efficiency.

Fig. 2. Electricity consumption by category of use.

6. Conclusion and Discussion:

Summary of Key Results: This study benchmarked resource efficiency, cost, and GHG impact in aluminium HPDC processes, revealing hidden inefficiencies in in-house aluminium recycling. The findings confirmed that in-house aluminium recycling leads to significant aluminium losses, which can be a major cause of increased costs and GHG emissions. Yield losses and process losses are major sources of aluminium loss, and the usage of operating resources like electricity and water is highly dependent on aluminium production volume.
Academic Significance: This study utilized MFA techniques to analyze resource flows in aluminium HPDC processes in detail and quantitatively presented the hidden inefficiencies of in-house recycling, expanding the academic understanding of the efficiency evaluation of circular economy systems. It also presented a methodology for comprehensively evaluating the sustainability of manufacturing processes from multiple perspectives by integrating resource efficiency indicators, cost analysis, and GHG impact assessment.
Practical Implications:
- The aluminium HPDC industry should re-examine the efficiency of in-house aluminium recycling and strengthen efforts to reduce aluminium losses. In particular, technical and operational improvement measures to reduce yield losses and process losses should be explored.
- Cost reduction and GHG emission reduction effects can be simultaneously achieved by improving energy efficiency and reducing water consumption.
- Systemic improvement efforts, such as worker training, maintenance, strengthening quality assurance systems, and establishing shop-floor information management systems, are crucial, in addition to technical improvements.
Limitations of the Research:
- The single case study limits the generalizability of the research findings. Future research needs to expand the scope to include various HPDC facilities.
- The scope of resources studied was limited to aluminium and major operating resources. Future research needs to expand the scope to include various chemicals and other resources used in the die casting process.
- GHG emission assessment was limited to the operating resources considered in this study. Life Cycle Assessment (LCA) research, including GHG emissions from the entire aluminium production process and waste treatment process, is needed.

7. Future Research Directions:

Expand benchmarking research to various HPDC facilities of different scales and technology levels to understand the resource efficiency status of the industry as a whole and derive optimal improvement strategies for each facility type.
Evaluate the impact of new die casting technologies, such as ATM (Advanced Thixotropic Metallurgy), on resource efficiency and environmental performance, and conduct comparative analysis with existing HPDC processes to review the feasibility of technology adoption.
Quantitatively analyze the effect of systemic improvement measures, such as worker training, shop-floor information management systems, and quality assurance systems, on resource efficiency improvement, and conduct research to present optimal system construction plans.
Conduct LCA research on aluminium HPDC products to evaluate environmental impacts from a product lifecycle perspective and explore ways to improve sustainability.

8. References:

Brunner PH, Rechberger H. Practical handbook of material flow analysis. Boca Raton: Lewis Publishers; 2004.
Gunesegaram D, Givord M, O'Donnell RG, Finnin BR. ATM high pressure die casting and its benefits. In: Proceedings of the 111th NADCA metalcasting congress; 2007.
Ramakrishnan S, Tharumarajah A, Koltun P, Roberts MJ. Eco-efficient light-metals component manufacturing. In: Proceedings of the first international light metal technology conference; 2003. p. 125-30.
Sustainability Victoria, Resource efficiency measurement-guidance notes, http://www.sustainability.vic.gov.au/resources/documents/2-SV-Resource_Efficiency_guidance_notes1.doc, 21 January 2008.
Tharumarajah A, Koltun P, Ramakrishnan S, Roberts M. Improving the environmental performance of aluminium die casting production. In: 9th international conference on manufacturing excellence (ICME 2003); 2003.
Young K, Eisen P. New die casting technologies-markets and applications. In: Die casting 2000 conference; 2000.

9. Copyright:

This material is based on the paper by A. Tharumarajah: Benchmarking aluminium die casting operations.
Paper Source: doi:10.1016/j.resconrec.2008.06.007
This material is a summarized version of the above paper, and unauthorized use for commercial purposes is prohibited.
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