Casting is one of the foundational techniques in metalworking, and investment casting and die casting are two commonly used methods. Although both are used to form metal parts and find application in different or similar fields, these two casting methods have distinct differences in various aspects. This article will present a comprehensive discussion on the differences between investment casting and die casting, as well as how to choose the appropriate casting process.
Difference Between Die Casting and Investment Casting: Process
What is Investment Casting?
Investment casting, also known as precision casting or lost-wax casting, mainly employs a meltable model, typically a wax model, to form a ceramic shell. The model is melted and removed, followed by the pouring of metal into the ceramic mold. Below is a simple overview of the investment casting process:
- Model Making: Initially, a model matching the final product’s geometry is made from meltable material (usually wax or plastic).
- Casting the Model: The model is attached to a tree-like structure and then immersed in ceramic sand or other refractory slurry to form a coating.
- Hardening and Baking: Once the coating has hardened, it’s placed in a baking oven to improve its strength and dry it out.
- Melting the Model and Casting: The internal meltable model (usually wax) is melted at high temperatures, and molten metal is poured into the hollow ceramic mold.
- Cooling and Demolding: The metal is allowed to cool and solidify in the mold, then the ceramic mold is broken to extract the casting.
What is Die Casting?
Die casting is a high-speed, high-pressure casting method that produces engineered metal parts by forcing molten metal under high pressure into a reusable steel mold. Below is a simple overview of the die casting process:
- Mold Preparation: High-quality metal molds are used, typically consisting of two parts, the fixed mold and the moving mold.
- Locking and Injection: The mold is closed and sealed, then molten metal is rapidly injected into the mold cavity under high pressure.
- Cooling and Solidification: The metal cools in the mold, usually quickly, to maintain high production efficiency.
- Opening the Mold and Ejection: Once the metal has cooled and fully solidified, the mold is opened, and the casting is removed or ejected.
Difference Between Die Casting and Investment Casting: Mold
Both investment casting and die casting involve the use of molds in the casting process, but the molds they use differ significantly in material, design, manufacturing, and application. The table below provides a detailed comparison between the molds used in investment casting and die casting.
Criteria | Investment Casting Mold | Die Casting Mold |
Material | Typically made of high-temperature-resistant ceramics | Usually made of tool steel or other high-strength, wear-resistant metals |
Design | More intricate to accommodate complex geometry and details | Generally simpler, designed for easy use and high production efficiency; often a two-part mold (fixed and moving) |
Manufacturing | Single-use; each casting requires a new mold. Created through multiple dips in ceramic slurry and baking | Designed for multiple uses; a single mold can produce tens of thousands of castings |
Application | Suited for small-scale production and complex, high-precision parts | Commonly used in large-scale production, especially when the parts have a relatively simpler structure but require high strength and wear resistance |
Investment Casting vs Die Casting: Advantages
Advantages of Investment Casting
- Highly Accurate and Complex: Investment casting can create castings with extremely high precision and complex geometric shapes, which is difficult to achieve in other casting methods.
- Excellent Surface Quality: Products generated by investment casting usually have superb surface quality, reducing the need for post-processing or surface refinement.
- Highly Adaptable: This method is particularly suitable for small-batch production, or for manufacturing highly specialized, customized components.
- Material Flexibility: Due to the use of high-temperature refractory molds, investment casting is suitable for various metals and alloys, including high-temperature alloys, aluminum, steel, and other materials with very high melting points.
- Customizable Size Range: Investment casting can produce small to large castings, ranging from as light as 0.1 kg to as heavy as 100 kg.
Advantages of Die Casting
- High Production Efficiency: Die casting is a highly automated process capable of rapidly and continuously producing a large volume of castings, making it highly suitable for large-scale production.
- Economical: Since the mold can be reused and the production speed is high, die casting often has a lower unit cost.
- High Mechanical Properties: Due to the use of high pressure to inject the molten metal into the mold, die-cast parts usually have very high mechanical strength, dimensional accuracy, and excellent wear resistance.
- Capability to Manufacture Intricate Features: Die casting technology allows for more intricate design features in the casting, such as grooves, protrusions, or other tiny geometric structures.
Difference Between Die Casting and Investment Casting: Application
Investment Casting Application
- Aerospace: When manufacturing parts with high precision, complex shapes, and high wear resistance, investment casting is the preferred method in the aerospace industry. It can produce blades with intricate shapes and complex cooling systems.
- Medical Equipment: Investment casting is used for producing fine, high-precision medical devices such as joint replacements and surgical instruments.
- Precision Instruments: This process is often used to make key components for precision instruments and equipment, as it can achieve highly complex and accurate shapes.
- Oil and Natural Gas: The oil and natural gas sector uses this method to manufacture pressure relief and safety components for their equipment.
- Environment and Energy: Investment casting is used for producing various high-temperature and corrosion-resistant complex parts, commonly found in solar energy, nuclear power, and chemical industries.
Die Casting Application
Die casting is highly suitable for mass production of commercial, consumer, and industrial products, such as vehicles, building materials, gears, and heavy machinery. Its design flexibility and metal options, combined with its cost-effectiveness, make it a popular choice globally. Below are some common application areas for die casting.
- Automotive Manufacturing: Die casting is widely applied in the manufacturing of automotive parts due to its suitability for large-scale production and high mechanical performance.
- Home Appliances: Die casting is the primary manufacturing method for internal structural components of appliances like washing machines, air conditioners, and refrigerators.
- Communication Equipment: Die casting is used for making metal cases and internal structures for phones, computers, and other electronic devices.
- Industrial Machinery: Die casting is also used in the production of various industrial machinery and equipment, especially those requiring high strength and wear resistance.
Difference Between Die Casting and Investment Casting: Cost
Investment Casting Cost
- Mold Cost: The molds used in investment casting are primarily made of ceramic materials and are generally single-use. This means that each casting requires a new mold, thus increasing the cost.
- Production Complexity: Investment casting is capable of producing intricate and high-precision castings. As a result, the production process is usually more time-consuming and cumbersome, which elevates the cost.
- Material Wastage: This method is more prone to material wastage as the ceramic molds are not recyclable.
- Batch Size: Investment casting is more suited for small-scale production. In large-scale manufacturing, the unit cost is generally higher.
Die Casting Cost
- Mold Cost: Die casting molds are typically made of high-strength alloy steel. Although the initial cost is high, multiple usages reduce the unit cost over time.
- Automation Level: Die casting processes are usually highly automated, improving production efficiency and helping to reduce unit costs.
- Material Efficiency: Die casting is relatively more efficient and economical in terms of material use.
- Batch Size: Die casting is more suitable for large-scale production, where the unit cost significantly decreases with volume.
From the above information, it is evident that production volume plays a critical role when comparing the production costs of investment casting and die casting. Investment casting excels in producing intricate, high-precision castings but often at a higher cost. Die casting, on the other hand, exhibits clear cost advantages in large-scale production.
Difference Between Die Casting and Investment Casting: Finish
- In common casting processes, investment casting consistently offers the best surface finish. As a standard, it can achieve precise tolerances of IT5-6 and A 125 micro finishes.
- Die casting can also produce a good surface finish but requires additional machining to achieve the desired results. However, in actual production, secondary processes like surface treatment are often employed to enhance the surface finish for both investment and die cast parts, especially for products where surface finish is critical.
Die Casting vs Investment Casting: How to Choose?
Part Size
- Investment casting has certain limitations in the size of castings it can produce, ranging from 0.05 kg to 100 kg.
- Unlike investment casting, die casting can produce castings of any size. However, manufacturing larger parts through die casting will require larger molds and higher unit costs.
Product Complexity
- The geometric complexity of the casting product influences the choice of the correct process. Investment casting can produce complex shapes and effortlessly incorporate design features into the components. Thus, it is more suitable for products with complex structural shapes.
Material Choice
- Investment casting allows for the use of various alloys, including ferrous and non-ferrous metals, providing more material options than die casting.
- Die casting is more applicable for non-ferrous metals such as zinc, copper, aluminum, magnesium, lead, tin alloys, and tin-based alloys.
Production Volume
- Investment casting is more suitable for small-scale production, generally less than 8000 pieces.
- Compared to investment casting, die casting is quicker and can produce between 100 to 2000 parts per hour. Therefore, die casting is highly suitable for large-scale projects and production runs exceeding 8000 pieces. Additionally, die casting ensures excellent repeatability and consistency, making it the ideal choice for large-scale production.
Tolerance
- Both investment casting and die casting can produce products with good and strict tolerances.
- Generally, smaller parts have higher dimensional accuracy. For smaller components, investment casting can offer stricter tolerances.
- For larger castings, investment casting typically loses some dimensional accuracy. Unlike investment casting, die casting can provide better tolerances for larger castings.
Conclusion
Die casting and investment casting are mature technologies, and these two castings also have different advantages. The choice and appropriate casting method depends primarily on your specific needs. For example, die casting is best suited for rapid, high-volume production of castings. Investment casting is more suitable for smaller products with complex features.
From the perspective of casting materials, die casting is only suitable for non-ferrous metals, including aluminum, zinc, copper, etc. Investment casting is suitable for ferrous and non-ferrous metals such as stainless steel.
If you have any questions about the choice of casting process, you can consult our technical team.
