Introduction
Aluminum cast parts (aluminum castings) are about one-third the weight of iron castings yet possess high strength, making them useful in a wide range of fields such as automotive parts, building materials, and machinery. However, for those new to the field, there are many points that can be difficult to understand, such as wall thickness design specific to casting, dimensional tolerances, and the applicable scope of each manufacturing method. This article organizes typical technical, cost, and delivery questions received from the field and explains them in an easy-to-understand Q&A format. We will deliver practical knowledge that will be a reference for procurement and design work.
What is aluminum casting? What are its features?
Aluminum cast parts (hereafter, aluminum castings) are created using a technology where aluminum is heated to about 660°C or higher to melt it, then poured into a mold to be integrally formed. They exhibit high mechanical strength despite being about one-third the weight of iron castings and are used in a wide range of fields, including automotive parts, building materials, industrial machinery, and electronic equipment housings. Furthermore, because it is possible to create hollow shapes and complex curved surfaces in a single process, which is difficult with machining, it contributes to reducing the number of parts and improving cost efficiency.
Features and Advantages: Lightweight, Corrosion Resistance, Complex Shape Compatibility
- Lightweight: Specific gravity of about 2.7, which is about 1/3 that of iron. Contributes to weight reduction in vehicles and portable equipment.
- Corrosion Resistance: An oxide film that naturally forms on the surface acts as an anti-corrosion barrier, making it ideal for outdoor equipment and water-related parts.
- Complex Shape Compatibility: Allows for hollow structures, thin-wall molding, and integrated designs, reducing assembly steps and material loss.
- Thermal Conductivity: Has about three times the thermal conductivity of iron, making it suitable for heat sinks and heat dissipation components.
These characteristics enable weight reduction and functional integration in a single cast part, leading to the optimization of the production process.
Difference from Aluminum Die Casting
Aluminum die casting, which is often compared to aluminum casting, is a method where molten metal is injected into a mold under high pressure. The main differences are as follows:
| Item | Aluminum Casting (Sand/Gravity) | Aluminum Die Casting |
|---|---|---|
| Initial Cost | Low to Medium (¥300,000–¥800,000/mold) | High (¥1,000,000–¥3,000,000/mold) |
| Dimensional Accuracy | Moderate (±0.5–1.0mm) | High (±0.1–0.3mm) |
| Lot Size | Small to Medium (tens to tens of thousands) | Large (tens of thousands or more) |
| Design Freedom | High (wall thickness changes, simple modifications possible) | Restricted (thin walls, complex curves possible) |
If you prioritize flexibility for prototyping or high-mix, low-volume production, sand/gravity casting is suitable. For thin-walled, high-precision, mass production, die casting is appropriate.
Explanation of Typical Materials (like AC4C) by Application
Here are typical aluminum casting alloys specified by JIS standards and their main applications.
| Material | Features | Main Applications |
|---|---|---|
| AC4C | Excellent strength, corrosion resistance, and weldability | Construction machinery parts, valves, outdoor enclosures |
| AC2A | Good castability, low cost | General machinery parts, wheels |
| ADC12 | For die casting, high dimensional stability | Small automotive parts, motor housings |
AC4C, in particular, has a good balance of corrosion resistance and high strength, and its adoption rate in overseas factories is high, making it an essential item to check during procurement.
Frequently Asked Questions About Manufacturing and Design
Q1: Do you support small-lot prototyping for aluminum castings?
Yes. At Daiwa Keikinzoku Vietnam, we support small-lot prototyping with suppressed mold costs by utilizing sand casting and gravity casting. While typical mold costs range from ¥300,000 to ¥1,000,000 per mold, sand casting can reduce this by about 50% in some cases. The estimated lead time after design drawing confirmation is about 15-20 business days. We can also flexibly respond to design changes, making it ideal for projects that require a balance of cost and speed.
Q2: What dimensional tolerances can you accommodate for aluminum castings?
Dimensional tolerance varies depending on the casting method and finishing process.
- Sand Casting: ±0.5–1.0 mm
- Gravity Casting (using a metal mold) / Low-Pressure Casting: ±0.2–0.5 mm
- CNC Machining Finish (CNC: Computer Numerical Control cutting machine): Approx. ±0.01 mm
If strict tolerance specifications are required for critical areas, we recommend a design that allows for a machining allowance in advance, followed by fine-tuning with CNC machining after casting, using an “integrated casting + machining flow.”
Q3: What is the approximate cost of a casting mold?
The mold cost varies depending on the manufacturing method, alloy type, and complexity of the shape.
- Sand Casting: ¥300,000–¥500,000 / mold
- Gravity Casting (using a metal mold): ¥500,000–¥800,000 / mold
- High-Pressure Die Casting Mold: ¥1,000,000–¥3,000,000 / mold
While a metal mold has the effect of reducing the unit price in the long term, the initial cost is high, so the benefits are significant when mass production of 100,000 to 200,000 units or more is expected.
Q4: Which casting method (sand/metal mold/gravity) should I choose?
Please select a method based on the following four items.
- Lot Size and Cost
- Small lot (up to several hundred): Sand casting
- Medium lot (several thousand to tens of thousands): Gravity casting / Low-pressure casting
- Large lot (hundreds of thousands or more): High-pressure die casting
- Precision and Shape Complexity
- Hollow structures or complex shapes: Sand casting offers greater design freedom
- Thin-walled, high-precision: Die casting is advantageous
- Material and Mechanical Properties
- Emphasis on corrosion resistance and strength: Gravity casting using AC4C
- Emphasis on cost and machinability: Die casting with AC2A/ADC12
- Delivery Time and Flexibility for Changes
- Short delivery time: Simplify mold production with sand casting
- Specification changes: Redesign costs are low with sand casting, offering flexibility
By making a comprehensive judgment on these factors and deciding on the optimal casting method when creating the design drawings, you can achieve a balance of cost, quality, and delivery time.
FAQ About Machining and Finishing
Q5: Can you handle the entire process in-house, up to machining?
Yes. At Daiwa Keikinzoku Vietnam, we have established an in-house integrated system from aluminum casting to finishing.
- CNC Machining (CNC: Computer Numerical Control cutting machine) Utilizing 5-axis and 3-axis machining centers, we achieve high-precision finishing with a tolerance of ±0.01 mm.
- Lathe Machining We handle various shapes, including internal and external diameter machining of hollow parts and shafts.
- Tapping and Drilling We can perform threading work from about M2 to M16 and drilling.
By completing the process in-house, we shorten setup times and achieve both adherence to delivery deadlines and ensured traceability.
Q6: Is surface treatment like painting, polishing, or anodizing possible?
Yes, it is possible. We propose the following surface finishes according to the application, design, and weather resistance requirements.
- Anodizing
- Hard anodizing: Emphasis on wear resistance
- Colored anodizing: Improved aesthetic design
- Powder Coating / Solvent-based Painting
- Outdoor weather resistance (UV and salt damage resistance)
- For food equipment (FDA-compliant paints can be used)
- Polishing / Buffing Finish
- Various patterns like hairline and mirror finish
- Further enhanced corrosion resistance through surface smoothing
For all of these, we thoroughly perform pre-treatment (degreasing, pre-polishing) to maximize adhesion and durability.
Q7: What are the countermeasures for casting defects (porosity, shrinkage)?
Porosity (voids) and shrinkage (shrinkage cavities) affect casting quality. We minimize their occurrence with the following measures.
- Mold Design Optimization
- Even supply of molten metal through riser placement
- Control of local solidification speed with chills (cooling materials)
- Strict Management of Casting Conditions
- Reduce turbulence by optimizing molten metal temperature and flow rate
- Prevent gas entrapment with degassing treatment (vacuuming, nitrogen purge)
- In-line Inspection
- Internal defect detection by X-ray inspection
- Early identification of surface porosity with penetrant testing or water immersion tests
By combining these, we achieve reproducible, high-quality aluminum castings.
Q8: Can aluminum castings be welded or bonded?
It is possible, but selecting the method according to the alloy type and application is essential.
- Welding
- TIG welding: High-quality finish with aluminum wire suitable for AC4C, etc.
- MIG welding: Speed-focused on-site repair for thin to medium plates
- Thorough pre-treatment (oxide film removal) and post-treatment (flux removal)
- Bonding
- Epoxy-based structural adhesives: For parts emphasizing impact and heat resistance
- Acrylic/Silicone-based: For applications requiring waterproofing and airtightness
After welding or bonding, we perform stress relief heat treatment and reinforcement of edge parts to ensure strength and durability.
Questions About Procurement, Delivery, and Export
Q9: How long is the delivery time for aluminum castings?
The delivery time varies depending on the casting method, quantity, and processing details, but a general guideline is as follows:
- Sand Casting (small lot): Approx. 15–25 business days after design confirmation
- Gravity Casting (using a metal mold): Approx. 20–30 business days after design confirmation
- Die Casting (mass production): Approx. 30–45 business days after design confirmation
Adding CNC machining or surface treatment requires an additional 5-10 business days. Lead times may be extended during busy periods or if there are specification changes, so confirming drawings and quantities as early as possible will lead to a shorter delivery time.
Q10: Is it possible to export to Japan (with local support in Vietnam)?
Yes. Daiwa Keikinzoku Vietnam has extensive experience in exporting to Japan and has the following system in place.
- Export Permits and Customs Procedures: We have already obtained the necessary licenses in Vietnam.
- Inspection and Packaging: After inspection compliant with JIS standards and ISO9001, we perform packaging that can withstand both sea and air transport.
- Transport Mode: You can choose between sea freight (LCL/FCL) and air freight.
We handle an average of about 200 containers per year, and our dedicated team’s traceability management maintains a post-delivery claim rate of 0.5% or less.
Q11: What is the price range for aluminum castings? What factors affect the unit price?
The unit price varies greatly depending on the following factors:
- Lot Quantity: Disperses mold costs, reducing the unit price.
- Alloy Type: AC4C (¥1,200–¥1,800/kg), ADC12 (¥900–¥1,300/kg), etc.
- Shape and Wall Thickness: Complex shapes or thin-walled parts are more expensive due to increased processing steps.
- Finishing Level: An additional 10–30% with machining and surface treatment included.
For example, a medium-sized part (approx. 1kg) made by sand casting without machining can start from ¥2,000/piece, while mass-produced die-cast products can be in the ¥500 range.
Q12: Can you shorten lead times or handle urgent requests?
Yes, it is possible. The main measures for shortening are as follows:
- Parallel Processes: Proceed with design reviews and material procurement simultaneously with mold production.
- Use of Simple Molds/Jigs:先行試作を、量産型より省力化した簡易型で行う (Conduct advance prototyping with simplified molds that are less labor-intensive than mass-production molds).
- Reuse of Existing Molds: Start production immediately using existing molds of the same shape.
For urgent requests, we can shorten the construction period by up to 30%, assuming a premium fee. Please feel free to consult with us about urgent projects.
Learning from Common Mistakes and Success Stories
[Success Story] Hybrid Procurement with Japanese Design + Vietnamese Production
A Japanese company, Company A, verified a prototype of an aluminum cast part in Japan using a 3D printer, confirmed the shape and tolerances in advance, and then deployed the drawings to their Vietnam factory. Locally, they performed sand casting and CNC machining in parallel. As a result, they shortened the lead time from prototype to mass production by about 40% compared to conventional methods and also succeeded in reducing costs by about 20%. The key was to clarify the division of roles between the domestic design team and the local production team and to establish a close communication system from an early stage.
[Failure Story] Design Mistake Ignoring Casting Characteristics
Company B requested mold production for a thin-walled, complex-shaped aluminum cast part directly from the design stage. However, because they did not consider the allowable wall thickness for each casting method or cooling control, bubbles (porosity) and shrinkage cavities frequently occurred in the cast products. Although they tried to meet the tolerances with post-processing, rework increased, causing significant delivery delays and cost overruns. From this lesson, it became clear that it is essential to align on wall thickness guidelines from JIS standards and cooling rate management points with a casting expert during the design phase.
Data Box | Summary of Metrics Related to Casting FAQ
| Title | Data | Source (with link) |
|---|---|---|
| Average delivery time for aluminum castings | 15–30 days (depending on method) | Japan Foundry Society “Casting Production Statistics” https://www.jfs.or.jp/ |
| Guideline for mold production cost | ¥300,000–¥1,000,000 / mold | Japan Foundry Society “Casting Production Statistics” https://www.jfs.or.jp/ |
| Common materials | AC4C, AC2A, ADC12 (JIS standards) | Genspark “Types and Features of Aluminum Castings” https://genspark.jp/metal-casting/aluminum-casting-guide |
| Dimensional tolerance | ±0.5–1.0mm (sand), ±0.2mm (metal mold) | Genspark “Types and Features of Aluminum Castings” https://genspark.jp/metal-casting/aluminum-casting-guide |
| Number of companies supporting delivery from Vietnam to Japan | Approx. 120 (as of 2024) | JETRO “Vietnam’s Export System and Practices” https://www.jetro.go.jp/world/asia/vn/trade_01.html |
Summary
Aluminum cast parts are a processing method that combines lightness, high strength, and excellent corrosion resistance, enabling cost reduction through integrated molding of complex shapes and process simplification. On the other hand, specialized knowledge is essential, including dimensional tolerances for each casting method, wall thickness design, countermeasures for porosity and shrinkage, and control of initial mold costs. By utilizing the FAQ in this article and managing the entire system from prototyping and small lots to mass production, surface treatment, and even export to Japan, you can achieve the optimal balance of quality and cost. In particular, hybrid procurement combining domestic design with Vietnamese production and trouble prevention by optimizing casting conditions are key points in success stories. Please work closely with an experienced partner and build the optimal manufacturing flow based on accurate knowledge.
