Aluminum casting & mold design services

Introduction

For Japanese manufacturers, selecting the right component manufacturing method is a critical business decision that significantly impacts product competitiveness. Aluminum alloys, with their excellent properties such as lightweight, strength, corrosion resistance, and recyclability, are seeing increasing demand across diverse sectors including automotive, aerospace, industrial machinery, and medical devices. According to the Ministry of Economy, Trade and Industry’s Current Survey of Production, non-ferrous metal product output reached approximately 6 million tons in 2022, with aluminum castings holding a significant position. However, there are multiple manufacturing options, each with different characteristics regarding cost, quality, lead time, and design flexibility, necessitating an optimal choice.

This article focuses on two prominent aluminum casting methods: “sand casting“ and “lost wax casting“, also known as investment casting,. We will provide a detailed comparison of their characteristics, advantages and disadvantages, cost structures, and appropriate application areas. Our aim is to provide practical information to Japanese manufacturing executives and procurement managers, enabling them to select the optimal manufacturing method that aligns with their product requirements. Furthermore, we will introduce the high-quality and cost-efficient solutions offered by Daiwa Aluminum Vietnam, hoping to assist in your overseas procurement strategies.

While sand casting is suitable for relatively low-cost, short-lead-time, and large-part manufacturing, it has limitations in dimensional accuracy and surface finish. In contrast, lost wax casting offers high dimensional accuracy, excellent surface finish, and the ability to create complex shapes, but tends to face challenges with cost and lead time. Understanding these characteristics and making an optimal choice with a view towards the entire product lifecycle is key to establishing a competitive advantage.

Characteristics and Application Areas of Sand Casting: Cost and Flexibility

Sand Casting Process and Basic Features

Sand casting is one of the oldest casting methods, dating back thousands of years, where molten metal is poured into a mold made of foundry sand, a mixture of sand and binder, allowed to cool and solidify to form a product. It is said to account for approximately 70% of the world’s casting production even today, Source: Japan Foundrymen’s Society,.

The process begins by creating a cavity, mold, in the foundry sand using a wooden or metal pattern. Molten aluminum alloy is then poured into this mold. After cooling, the sand mold is broken apart to retrieve the casting, and unwanted parts, gates, risers, etc., are removed, followed by finishing operations. The main characteristic of this method is the relative ease of mold production and its adaptability to various shapes.

Advantages: Low Cost, Short Lead Time, Suitability for Large Parts, Flexibility for Small-Batch, Multi-Variety Production

• Low Cost: Mold costs are relatively inexpensive. Wooden patterns can range from tens to hundreds of thousands of yen, and simple metal patterns from hundreds of thousands to several million yen. This helps keep initial investment low.
• Short Lead Time: Mold production time is short, allowing for relatively quick response from prototyping to mass production. For typical prototypes, it’s often possible within 2 weeks to 1 month, and mass production ramp-up is also swift.
• Suitability for Large Parts: The method is relatively flexible in terms of mold size, enabling the manufacture of large parts ranging from a few kilograms to hundreds of kilograms, and in some cases, several tons. Examples include automotive engine blocks, approx. 20-50 kg, and large industrial machinery housings.
• Flexibility for Small-Batch, Multi-Variety Production: Due to low mold production costs, it is economically viable for prototyping from a minimum lot size of 1 piece, or small-batch production of several hundred pieces. This offers high flexibility in markets requiring multi-variety, small-batch production.

Disadvantages: Limitations in Dimensional Accuracy, Surface Finish, and Design Freedom

• Dimensional Accuracy: Sand molds are flexible, so dimensional tolerances are generally around ±0.5mm to ±1.5mm, which is inferior compared to other casting methods. Accuracy can further decrease for complex shapes or thin-walled sections.
• Surface Finish: Since sand particles are transferred, the surface finish is rough, typically Ra25μm to Ra100μm. If a smooth surface is required, additional machining, cutting, grinding, etc., will be necessary, potentially increasing post-processing costs.
• Design Freedom Limitations: As the mold must be broken to remove the product, there are constraints on undercuts and complex internal shapes. Uniform wall thickness is also important, as abrupt changes can lead to defects.

Cost Structure: Balance of Pattern Cost, Material Cost, and Processing Cost

The total cost of sand casting primarily consists of the following elements:

• Pattern Cost: Wooden, resin, or metal patterns are chosen based on production volume and accuracy requirements, ranging from tens of thousands to several million yen. Wooden patterns are often chosen for small-batch production, resin patterns for medium-batch, and metal patterns for large-batch production.
• Material Cost: Determined by the type and quantity of aluminum alloy used. For example, common aluminum alloys like ADC12, JIS H 5302, can range from several hundred to a thousand yen per kilogram.
• Processing Cost: Includes costs for melting, pouring, cooling, mold breakdown, deburring, shot blasting, and necessary machining, cutting, drilling, tapping, etc.,. The presence or absence of post-processing significantly impacts the total cost.

Generally, as production volume increases, the pattern cost is relatively diluted, and the unit product price decreases. For medium-volume production of less than 1,000 units per year, sand casting tends to offer excellent cost performance.

Main Product Application Examples

Due to its characteristics, sand casting is widely applied to products such as:

• Automotive Parts: Engine blocks, transmission cases, intake manifolds, suspension components. These parts are often large and complex in shape, where cost and productivity may be prioritized over extreme precision.
• Industrial Machinery Parts: Pump housings, valve bodies, reducer cases, frame components. Durability and cost efficiency are required in this sector.
• Building Materials: Gates, fences, decorative items. Design and durability are important.
• Railway Vehicle Parts: Bogie frames, coupler components. Applied to large parts requiring strength.

Characteristics and Application Areas of Lost Wax Casting: High Precision and Complex Shapes

Lost Wax Casting Process and Basic Features

Lost wax casting, also known as investment casting, is a method where a wax pattern is created, coated with a ceramic shell, the wax is melted and removed, burned out, to create a cavity, and then molten metal is poured into this cavity. This method has existed since ancient Egyptian times and is now an indispensable technology for manufacturing high-precision parts in industries such as aerospace, Source: What is Lost Wax Precision Casting? Explaining its Advantages, Disadvantages, and Methods,.

The specific process involves first injection molding wax patterns using a die. Next, multiple wax patterns are assembled into a tree-like structure. This tree is then repeatedly dipped into a ceramic slurry and dried to form a thick ceramic shell. Subsequently, the shell is heated to melt out the wax, dewaxing, and then fired at high temperatures to increase its strength. Finally, molten metal is poured into the fired shell, and after cooling and solidification, the shell is broken to retrieve the casting.

Advantages: High Precision, Complex Shape Capability, Excellent Surface Finish, High Design Freedom

• High Precision: With precisely molded wax patterns and a rigid ceramic shell, very high dimensional accuracy of approximately ±0.05mm to ±0.2mm can be achieved. This is particularly valuable for small and precision parts.
• Complex Shape Capability: Since wax patterns are formed in a die, undercuts, complex internal shapes, and thin-walled sections, approx. 0.8mm to 1.5mm wall thickness, can be cast as a single piece. This eliminates the need to join multiple parts by welding or assembly, contributing to part count reduction.
• Excellent Surface Finish: The ceramic shell has a very smooth surface, allowing for an excellent as-cast surface finish of Ra3.2μm or less. This can significantly reduce or eliminate the need for post-processing, cutting, grinding, etc.,.
• High Design Freedom: The ability to cast complex shapes as a single piece allows designers greater freedom to pursue functionality and lightweighting in their part designs.

Disadvantages: High Cost, Long Lead Time, Unsuitability for Large Parts

• High Cost: In addition to die production costs, many steps are required, such as wax pattern injection molding, tree assembly, ceramic shell formation, multi-layer coating, dewaxing, and firing. This results in a higher unit product price compared to sand casting. Wax pattern costs commonly reach hundreds of thousands to several million yen.
• Long Lead Time: Due to the multi-stage process, manufacturing lead times are longer. It is not uncommon for several months to be required from prototyping to mass production ramp-up.
• Unsuitability for Large Parts: Due to constraints in ceramic shell formation and furnace size, it is generally suitable for manufacturing relatively small to medium-sized parts, typically ranging from a few kilograms to tens of kilograms. Manufacturing large parts exceeding several hundred kilograms is difficult.

Cost Structure: Balance of Wax Pattern Cost, Material Cost, and Processing Cost

The total cost of lost wax casting consists of the following elements:

• Wax Pattern Cost: The cost of the die for injection molding wax patterns, which tends to be high, ranging from hundreds of thousands to several million yen. This cost’s proportion to the unit price decreases as production volume increases.
• Material Cost: Determined by the type and quantity of aluminum alloy used.
• Processing Cost: Includes costs for wax pattern formation, tree assembly, shell formation, dewaxing, firing, pouring, shell breakdown, deburring, shot blasting, and necessary precision machining. Due to the many steps, processing costs account for a significant portion of the total cost.

Generally, for mass production exceeding several thousand units per year, lost wax casting can offer a total cost advantage by leveraging its high precision and complex shape capabilities, especially when the reduction in post-processing is significant.

Main Product Application Examples

Due to its high precision and complex shape capabilities, lost wax casting is used for precision parts such as:

• Medical Device Parts: Artificial joints, surgical instruments, endoscope components. Biocompatibility and high precision are required.
• Aerospace Parts: Turbine blades, engine components, structural parts. Lightweighting, high strength, and reliability are paramount.
• Precision Machinery Parts: Hydraulic and pneumatic equipment parts, robot parts, optical instrument parts. High dimensional accuracy and surface quality are demanded.
• Art and Craft Items: Sculptures and decorative items with intricate designs.
• Automotive Parts, High-Functionality,: Turbocharger components, fuel injection system parts, especially where high precision is required.

Optimal Solutions Provided by Daiwa Aluminum Vietnam

To succeed in global competition, Japanese manufacturers must achieve both cost competitiveness and high quality. Overseas procurement is an effective means to this end, but it also comes with challenges such as quality control, lead time adherence, and communication. Daiwa Aluminum Vietnam is committed to overcoming these challenges and providing optimal aluminum casting solutions to our customers.

Daiwa Aluminum Vietnam’s Technical Capabilities and Quality Management System

Daiwa Aluminum Vietnam has implemented Japanese technology and quality management know-how, cultivated over many years, at its production base in Vietnam to deliver high-quality aluminum casting products. Under a strict ISO 9001 certified quality management system, thorough inspections are conducted at each stage, from raw material acceptance to final product shipment. For example, a spectroscopic analyzer is used for material analysis to precisely control components. In the casting process, X-ray inspection and fluorescent penetrant inspection are employed to check for internal defects, aiming to keep the defect rate below 0.5%. Furthermore, a 3D measuring machine is utilized for dimensional inspection to achieve the high precision required by our customers.

Capabilities for Both Sand Casting and Lost Wax Casting

Our customers’ product requirements are diverse. Sand casting is suitable for needs such as cost reduction for small-batch, multi-variety production, or short-lead-time procurement of large parts. On the other hand, lost wax casting is optimal when complex shapes, high precision, and excellent surface finish are required. Daiwa Aluminum Vietnam has established a production system capable of flexibly handling both of these major aluminum casting methods.

• Sand Casting Line: Equipped with automatic molding machines, capable of mass production from several thousand to tens of thousands of units per month. By combining this with manual molding, we can also respond quickly to prototyping from 1 piece and small-batch production. By providing integrated services from pattern production to casting, machining, and surface treatment, we simplify our customers’ procurement processes.
• Lost Wax Casting Line: Achieves the manufacture of complex-shaped and high-precision parts through advanced wax pattern molding technology and precise shell formation processes. We actively propose design changes, such as thin-walled parts, approx. 1.0mm wall thickness, and integrating multiple parts, contributing to customer cost reduction and performance improvement.

Optimal Proposals Based on Customer Requirements, Quality, Cost, Lead Time, Quantity,

We meticulously analyze customer product drawings and specifications to propose the optimal combination of manufacturing method, material, and post-processing. For example, for parts with an annual production volume of around 500 units, we recommend sand casting to minimize initial costs and propose an approach where precision is ensured through post-processing. Conversely, for parts with an annual production volume exceeding 5,000 units and requiring high precision, we present the total cost benefits of lost wax casting through integrated molding and reduced post-processing.

We not only perform casting but also focus on VA/VE, Value Analysis/Value Engineering, proposals from the design stage. For instance, we contribute to the overall optimization of our customers’ products, such as lightweighting, strength improvement, and reduction of assembly man-hours. As a past achievement, for a certain industrial machinery part, switching from sand casting to lost wax casting resulted in reducing the number of parts from 3 to 1, cutting assembly man-hours by 20%, and lightweighting the product by 15%.

Measures to Reduce Quality and Lead Time Risks in Overseas Procurement

The biggest concerns in overseas procurement are quality issues and lead time delays. Daiwa Aluminum Vietnam has established a system to minimize these risks.

• On-site Management by Japanese Expatriates: Japanese engineers and managers are permanently stationed at our Vietnam factory to ensure thorough adherence to Japanese quality standards and production management methods. This prevents misunderstandings due to language barriers and ensures smooth communication with customers.
• Supply Chain Stabilization: Key raw materials are procured from reliable suppliers, and multiple sources are secured to diversify supply risks. Furthermore, increasing the procurement ratio within Vietnam reduces risks associated with fluctuations in international logistics.
• Strict Lead Time Management: From the production planning stage, customer delivery dates are prioritized, and progress is thoroughly managed. Our on-time delivery rate has consistently been over 98% for the past five years, earning customer trust.
• On-site Machining and Surface Treatment: In addition to casting, post-processes such as cutting, grinding, shot blasting, anodizing, and painting can also be handled consistently within our Vietnam factory. This reduces the hassle of ordering from multiple vendors, logistics costs, and lead time risks, while maintaining consistent quality.

Daiwa Aluminum Vietnam serves as a partner to solve our customers’ challenges, providing optimal aluminum casting solutions. Please feel free to contact us with any requirements.

Conclusion

In selecting an aluminum casting manufacturing method, sand casting and lost wax casting each possess distinct characteristics, and the choice heavily depends on the product’s specific requirements, quality, cost, lead time, quantity, design freedom,. Sand casting excels in low cost, short lead time, suitability for large parts, and flexibility for small-batch, multi-variety production, but has limitations in dimensional accuracy and surface finish. In contrast, lost wax casting achieves high precision, complex shape capability, excellent surface finish, and high design freedom, but tends to face challenges with cost and lead time.

To select the optimal manufacturing method, a multifaceted consideration of product functional requirements, annual production volume, budget, and lead time is essential. It is crucial to remember that this choice directly impacts product competitiveness.

Daiwa Aluminum Vietnam boasts technical capabilities to handle both sand casting and lost wax casting, coupled with a quality management system backed by years of experience. By deeply understanding our customers’ specific needs and providing comprehensive support from optimal manufacturing method proposals to design assistance, mass production, and post-processing, we contribute to our customers’ product development and business growth. If you are concerned about quality or lead time risks in overseas procurement, please do not hesitate to consult Daiwa Aluminum Vietnam. We promise to provide optimal solutions as a reliable partner to lead your business to success.