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Review These 7 Different Types of Casting Processes to Help You Select the Right Method for Your Project

With many different types of casting processes available, choosing the right method for a part’s intended use is essential to ensure efficient, high-quality production.

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To select the optimal casting method for your manufacturing requirements, it’s helpful to understand the advantages and disadvantages of the different casting processes. Below, we outline some of the most common types of casting processes used today in manufacturing, along with their pros and cons and ideal part types. Each process utilizes unique tools and techniques and is optimized for different materials and part types. Our goal is to help you choose the metal casting process that best suits your project.

For more detailed information, click the links and articles on this page to get free resources that dive deeper into specific topics and the casting capabilities of the Eagle Group. If you have any questions, feel free to contact us to speak with one of our experts.

What is Casting?

Casting is a manufacturing process that involves pouring molten metal into a mold cavity shaped like the desired part. As the metal cools, it hardens into the final shape, often requiring minimal secondary processing before final delivery. Nearly any type of metal can be used for casting, and this versatility makes casting applicable across various industries.

How Do You Determine the Best Casting Process for Your Needs?

Various casting manufacturing processes can meet a wide range of demands, producing precise parts for diverse applications. Each casting method has unique strengths depending on the intended use of the cast part.

Types of Casting Processes

1. Shell Mold Casting

Shell mold casting, also called shell molding, is an expendable mold casting process. This process applies fine-grained, resin-coated sand to the surface of a pre-heated pattern, usually made of cast iron or steel. The resin melts when heat is applied, bonding the sand grains. This resin-coated, heat-bonded sand becomes the “shell” of the mold. The “shell” is lifted from the pattern in halves, which are glued together with the help of precise locating features to prevent shifting. At Eagle Alloy, we can achieve shell molding within tolerances of +/- .030” on dimensions 6” or less and a surface finish of approximately 150–300 RMS. Click here for a complete description of available tolerances, radii, fillets and other design considerations.

Advantages: casting of thin and complex parts; good casting detail; nice finish; excellent repeatability; very productive; less machine stock required than in greensand or no-bake processes; competitive pound-prices; very short production lead times

Disadvantages: tooling prices higher than some other processes; limitations on size and weight; not ideal for small scale production

Learn More About Shell Mold Casting:

• Eagle Group Shell Molding Process (ebook)
• Introduction to Shell Mold Casting (blog series)
• Animation of the Shell Molding Process (video)
• Shell Molding Tolerances, Capabilities and Design Recommendations at Eagle Alloy, Inc. (reference guide)

2. Investment Casting

Investment casting, also known as lost wax casting, involves injecting wax into a die to create a wax “pattern”. These wax patterns are then assembled onto a “tree,” which is repeatedly dipped in a ceramic slurry. Once dried, the slurry hardens into a mold. The wax is then melted out, the mold is preheated, and molten metal is poured in. The resulting casting has an excellent surface finish of around 125 RMS, crisp lettering and minimal machine stock. This process is perfect for highly visible parts or replacing machining with cast features. Tolerances can typically be held to +/- .005”. Eagle Precision Cast Parts uses this process exclusively.

Advantages: excellent overall appearance; reduced or eliminated post-casting machining; ability to cast very thin walls; suitable for producing complex parts with high surface finishes; can cast hard-to-melt alloys (such as stainless steel); ideal for prototypes, economical tooling costs

Disadvantages: higher pound-prices compared to sand casting; not ideal for high-volume runs

Learn More About Investment Casting:

• Introduction to Investment Casting (ebook)
• Investment Casting Capabilities at Eagle Precision Cast Parts, Inc. (reference guide)
• Investment Casting: From Clunky Fabrication to Sleek Casting (case study)

Sand casting is broad term for a versatile metalcasting technique that uses a mixture of sand, water and additives to create a mold. Sand casting techniques have relatively low tooling costs, as they involve creating a single-use mold cavity made from a tightly packed sand mixture. Among its methods, greensand casting and the airset method differ in mold preparation and composition, with each having its own benefits and being suited to different manufacturing needs.

3. Greensand Casting

Greensand casting is a specific type of sand casting, with variations of the technique tracing back to ancient cultures in China and Egypt. In this process moist, clay-bonded sand is compacted around a pattern to form a mold. The resulting molds are suitable to cast nearly any metal alloy, both ferrous or non-ferrous, and most of the sand used for molding can be reclaimed and recycled.

Advantages: allows casting of large and thin-walled parts; can work with nearly any ferrous or non-ferrous alloy; lower tooling costs compared to other processes; cost-effective for smaller runs; recycling

Disadvantages: lower degree of accuracy compared to other processes; yields products with a rough surface finish; not ideal to use for products with strict dimensional tolerances

Learn More About Greensand Casting:

• Introduction to Greensand Casting (blog post)
• Greensand Casting Tolerances, Capabilities and Design Recommendations (reference guide)

4. Airset Casting

Another variation of sand casting, airset casting – also known as no-bake casting – utilizes chemically bonded sand that solidifies at room temperature. Unlike greensand, which uses clay and water, airset casting allows for finer sand grains and more consistent results with fewer surface defects. Tooling is inexpensive and this process can produce parts with excellent dimensional accuracy and surface finish.

Advantages: tight dimensional tolerances; lower machining costs; suitable for casting a wide range of ferrous and non-ferrous metals; lower tooling costs compared to shell mold casting

Disadvantages: higher initial costs; preparing the molds can take more time compared to greensand casting; lower reusability of sand

Learn More About Airset Casting:

• Getting Started with Airset Casting (blog post)
• Airset Casting Capabilities at Eagle Alloy, Inc. (reference guide)

5. 3D Printed Mold Casting

3D printed mold casting is an innovative process that blends 3D printing with traditional casting methods. The process starts with a digital 3D model of the part. Specialized machines then build molds and cores layer by layer, adding droplets of binder and depositing sand on top. Once the build is done, the mold is cleaned and sent to the foundry for assembly, pouring and finishing. Unlike conventional manufacturing, 3D printed molding requires no tooling, and can create intricate designs and prototypes with little to no scrap. However, this casting method is more time consuming than shell molding or investment casting and best suited for low-volume jobs. The Eagle Group uses 3D modeling software to design cast products and 3D models, partnering with Humtown Additive to manufacture high-quality 3D printed sand cores and molds.

Advantages: a 3D model is all that’s needed to print parts, making design changes quick and easy; no tooling required; no assembly needed, reduces production complexity; shorter lead times than machined metal molds, reduces product development and prototyping cycle times

Disadvantages: the 3D printing process is time-consuming and best for low-volume jobs; not cost-effective for mass production; mold size is restricted by the build volume of the 3D printer; molds are limited to specific sand and binder combinations; final surface finish depends on the 3D printing technology, printer quality and build material used

Learn More About 3D Printed Mold Casting and 3D Modeling

• Designing Cast Products: 3D Modeling and Solidification Simulation Software (blog post)
• State-of-the-Art 3D Scanning for Cast Products (bog post)
• 3D Printed Sand Cores & Molds (Humtown Additive website)

Other Casting Methods

The Eagle Group specializes in shell mold, investment, greensand, airset and 3D printed mold casting. While we do not perform permanent mold or die casting, these are widely used industry-standard casting methods that may be the right choice depending on your part’s requirements.

6. Permanent Mold Casting

Permanent mold casting is named for its reusable mold cavity, typically made of steel or cast iron instead of sand or refractory materials. Tooling can be complicated to produce, and since the molds are made of metal, their melting points limit the types of alloys that can be used. Permanent mold casting is often used with aluminum or other non-ferrous alloys that have lower melting points. Permanent molding is ideal for high-volume production, where it achieves low per-part costs, but for low- or medium-volume runs, the high cost of tooling can be prohibitive. Typical tolerances for this process are +/- .010”.

Advantages: reusable mold so initial tooling costs can easily be recouped with high-volume runs; high dimensional accuracy if an accurately machined mold is used; high repeatability; little preparation needs to be made between castings

Disadvantages: “permanent” molds don’t last forever and may need to be replaced midway through a large run; inflexible molds can lead to defects if castings are not removed promptly; limited options in terms of alloys cast

Learn More About Permanent Mold Casting:

• Getting Started with Permanent Mold Casting (blog post)
• Permanent Mold Cast Aluminum Fan Blades (case study)
• Permanent Mold Casting Tolerances, Capabilities and Design Recommendations (reference guide)

7. Die Casting

Die casting, similar to permanent mold casting, utilizes reusable steel molds and is a popular choice for non-ferrous alloys with relatively low melting points, like aluminum and zinc. The process involves injecting molten metal into the mold cavity at high pressure and speed to fill the mold cavity quickly and completely. Die casting can provide excellent casting parameters, but its high startup costs generally make it suitable for large-volume production runs.

Advantages: repeatability; high dimensional accuracy; ideal use for high-volume runs

Disadvantages: setup costs can be expensive; molds may need to be replaced midway through a large run; inflexible molds can lead to defects if castings are not removed promptly; limited options in terms of alloys cast

Learn More About Die Casting:

• What Is the Die Casting Process? (video)

CNC Machining

CNC machining is the final step in nearly any manufacturing process, and casting is no exception. Different metalcasting methods like those described above are ideal for different applications, and CNC machining is often the final finishing process in due to its high accuracy and precision.

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Eagle CNC Technologies uses highly sophisticated machining equipment and has extensive experience machining all types of casting and wrought materials. Our advanced milling and turning equipment can achieve tolerances within one ten thousandth of an inch (.”). Eagle CNC provides bespoke machining plans for Eagle Group foundries as well as a variety of job shops and OEM companies.

Advantages: high production scalability; extremely smooth surface finishes and high precision; time-efficient

Disadvantages: not well-suited for parts with highly organic or irregular shapes; size limitations; can be costly to machine complete from stock

Learn More About Eagle CNC’s Machining Capabilities:

• CNC Machining Tolerances, Capabilities and Equipment List at Eagle CNC Technologies, Inc. (reference guide)

The Eagle Group: Your Partner from Concept to Completion

At the Eagle Group, we offer a full suite of casting and machining solutions, ensuring that your project receives the attention and expertise it deserves every step of the way. Our team includes Eagle Alloy, Eagle Precision Cast Parts and Eagle CNC. Each company specializes in specific processes, allowing you to get what you need all from one source.

In the ever-evolving realm of manufacturing and production, industries are continually pushed to innovate and exceed expectations. The demand for advanced, quality products has never been higher. In such a competitive landscape, Worthy Hardware emerges as a leader, specializing in the development of complex, finely-detailed components through a variety of casting process types.

Choosing the right casting process can significantly influence the quality, cost, and production efficiency of the final product. Every method comes with its unique set of benefits and drawbacks, making the selection process crucial to success.

Understanding the Casting Process

What is casting process?

The casting process is an age-old manufacturing technique, where molten metal is poured into a mold to create a desired shape. From automotive parts to delicate jewelry, casting allows for a myriad of complex shapes and designs that would be difficult or impossible with other manufacturing methods.

Advantages of Casting Process

One of the significant advantages of casting is its ability to produce complex and detailed components. Even intricate geometric patterns can be created with utmost precision. Casting provides unparalleled flexibility, making it an indispensable part of our equipment at Worthy Hardware.

Along with complexity and precision, the casting process can easily adapt to large-scale production demands. Industries requiring mass production, such as automotive or home appliances, benefit greatly from this capability.

The Gravity Die Casting method, also known as Permanent Mold Casting, uses gravity to fill the mold with molten metal. The mold, typically made from iron or steel, is designed in two halves. First, the two halves of the mold are preheated to a suitable temperature. Then, the molten metal is poured into the mold without any force. Gravity alone causes the metal to fill the mold cavity. After the metal solidifies, the mold is opened to remove the casting.

Strengths of Gravity Die Casting:

1. Higher Quality Parts: This method creates parts that are stronger and more resistant to wear due to the slow cooling rate, which results in better mechanical properties. The resulting surface finish is excellent, often reducing or even eliminating the need for post-processing.
2. Reusability of Molds: The molds used in Gravity Die Casting are typically made from durable materials such as steel or iron, allowing them to withstand repeated use. This durability makes the method highly economical for large-scale production.
3. Efficient Production: Once the initial mold is made, the casting process can be repeated, enabling efficient mass production. The high repeatability ensures consistent quality across the product run.
4. Material Versatility: Gravity Die Casting can handle a wide variety of metals, including aluminum, zinc, and copper alloys. This versatility opens up a broad range of applications across different industries.

Limitations of Gravity Die Casting:

1. High Initial Costs: The creation of a reusable, robust mold can be costly, especially if the part design is complex. This expense makes Gravity Die Casting less attractive for small-scale production or prototyping.
2. Design Restrictions: While the method can produce complex shapes, it has limitations when it comes to very intricate or fine designs. The flow of metal relies on gravity, which may not fill extremely thin or delicate sections of a mold.
3. Longer Production Times: Compared to other casting methods like pressure die casting, Gravity Die Casting takes more time as the molten metal relies solely on gravity to fill the mold.
4. Part Size Limitations: The size of the parts that can be made using this process is limited due to constraints of the equipment and mold handling.

The Gravity Die Casting method has specific benefits that can make it an ideal choice depending on the project requirements. It's crucial to carefully consider these factors to determine if it's the most suitable casting process for a given application.

3.Casting through Pressure Die

Pressure Die Casting is a manufacturing process where molten metal is forced into a mold cavity under high pressure. The mold, often called a die, is created from steel and designed to form complex shapes with a high level of accuracy. The process begins with the two halves of the die being secured in the casting machine, following which the molten metal is injected. The high pressure ensures complete and quick filling of the mold. Once the metal solidifies, the mold is opened to remove the casting.

Strengths of Pressure Die Casting:

1. Speed of Production: Pressure die casting can produce parts at a very high speed, making it an excellent choice for high volume production runs.
2. Precision and Consistency: The process is capable of creating complex shapes with a high level of precision. It also offers excellent dimensional consistency across multiple production runs.
3. Smooth Finishes: Castings made from pressure die casting often require little to no machining due to the smooth finishes and precise dimensions the process provides.
4. Economical for Large Production Runs: Despite the high initial tooling cost, pressure die casting can be an economical choice for large production runs due to the high rate of production and minimal post-processing required.

Limitations of Pressure Die Casting:

1. High Initial Costs: The tooling cost for pressure die casting can be quite high, particularly for complex designs. It may not be economical for small production runs.
2. Porosity: The high pressure and fast cooling can lead to porosity in the casting, which may affect the strength and appearance of the final product.
3. Limited Material Choice: Pressure die casting is typically used with non-ferrous metals, such as aluminium, magnesium, and zinc alloys.
4. Design Complexity: While the process can handle complex shapes, the design of the part must take into account the need for the casting to be ejected from the die, which may limit design options.

Pressure Die Casting offers a good balance of speed, precision, and surface finish quality, making it a popular choice for many applications, particularly when large quantities are required. However, the benefits need to be weighed against its limitations, especially the high initial costs and potential issues with porosity.

4. Process of Investment Casting

Investment Casting, also known as lost-wax casting, is a precision casting process used to create objects from metal alloys that are too hard, complex, or delicate for more common manufacturing processes. The process starts with the creation of a wax pattern, which is essentially a replica of the desired part. This pattern is then coated in a refractory ceramic material. Once the ceramic material hardens, the wax is melted out, leaving a perfect mold. Molten metal is then poured into the mold to create the final product.

Strengths of Investment Casting:

1. Intricate Detail and High Precision: Investment casting allows for the creation of parts with intricate detail and high precision. The accuracy of this process is typically within 0.005 inches.
2. Precision and Consistency: The surface finish quality achieved with investment casting is excellent, often eliminating the need for further surface treatment or finishing operations.
3. Material Versatility: Investment casting can be used with a wide range of metal alloys, including those that are hard to machine or form using other casting processes.
4. Reduced Machining: Given the high degree of precision and quality surface finish, parts produced through investment casting often require little to no additional machining.

Limitations of Investment Casting:

1. Cost and Time-Consuming: The process of investment casting can be quite costly and time-consuming, particularly for complex parts. The creation of the wax pattern, ceramic shell, and final cast can all take considerable time and resources.
2. Size Limitations: While investment casting can produce highly detailed and complex parts, it is not as well suited to large parts due to the weight and handling difficulties of the ceramic shell
3. Not Ideal for High Production Volumes: Although it's excellent for complex parts and prototypes, the slow rate of production and high cost make it less than ideal for high-volume production runs.
4. Structural Limitations: While this method can produce intricate designs, it may not be suitable for parts that require internal structures or cores

Investment casting allows for the creation of highly detailed and precise components from a variety of metals, making it a preferred choice for industries that require precision parts such as aerospace, medical, and automotive. However, due to the high cost and time-consuming nature of this process, it's more suited to small-scale production or prototyping rather than high-volume manufacturing.

5. Plaster Casting Method

Plaster Casting is another important process in the casting family. This method uses a mixture of plaster of Paris and water to create the mold instead of sand. After creating a pattern of the desired part, the pattern is set into the plaster mixture. Once the plaster hardens, the pattern is removed, leaving a detailed impression. Molten metal is then poured into the plaster mold, and after the metal solidifies, the plaster mold is broken to reveal the final part.

Strengths of Plaster Casting:

1. Excellent Surface Finish: Plaster casting can produce parts with superior surface finishes and close dimensional tolerances, reducing the need for further finishing or machining.
2. Detailed and Complex Geometries: Like investment casting, plaster casting is capable of producing parts with intricate detail and complex geometries that might not be achievable with other casting methods.
3. Cost-Effective for Small Batches: Plaster casting can be a cost-effective method for small to medium production runs, as the cost of the plaster material is relatively low.

Limitations of Plaster Casting:

1. Time-Consuming Process: The plaster mold needs to be baked at a high temperature to remove moisture, and this process can take several hours or even days depending on the size of the part, making it a relatively slow method of casting.
2. Not Suitable for Large Parts: The plaster casting method is generally not suitable for large parts due to the long drying times and the difficulty in handling large plaster molds
3. Mold Can't be Reused: The plaster mold is destroyed when the part is removed, so a new mold must be made for each casting. This can add time and expense to the process, especially for large production runs.

Plaster casting is an excellent method for creating complex, high-quality parts, particularly when surface finish and detail are key considerations. However, the time-consuming nature of the process and the one-time use of the molds can make it less suitable for high-volume production or for casting of large parts.

6. Technique of Centrifugal Casting

A. Creation of Patterns
The process begins with the creation of patterns. The pattern is an essential part of the casting process, as it replicates the exact shape and size of the component to be produced. Materials like wood, plastic, metal, or even wax can be used to make patterns, depending on the complexity of the component and the type of casting process used.

B. Preparation of Molds
Once the pattern is ready, the next step is to prepare the mold. In sand casting, the pattern is pressed into the sand to create a cavity. For investment casting, the pattern is dipped into a ceramic slurry to create a shell. In die casting, a metal die is used instead of a pattern. The mold must be designed to allow for easy removal of the cast part and accommodate the shrinkage of the metal as it cools.

C. Selection of Metal Alloys
The next step in the casting process is the selection of the appropriate metal alloy. The choice of metal depends on the application of the final product, its required properties, and the casting process to be used. Common materials include aluminum, steel, iron, copper, and magnesium. Specialty alloys may also be used to meet specific performance requirements.

D. Melting and Casting of the Alloy
Once the mold is prepared and the metal alloy is chosen, the metal is melted in a furnace. The molten metal is then poured or forced into the mold. The method of introducing the metal into the mold depends on the casting process. For instance, in gravity die casting, the metal is poured, while in pressure die casting, it's injected under high pressure.

E. Final Touches
After the metal has cooled and solidified, the final cast part is removed from the mold. This could involve breaking the sand mold or opening the metal die. The part then goes through various finishing processes, such as cleaning, heat treatment, surface treatment, or machining, to achieve the desired dimensional accuracy and surface finish.

Conclusion

Choosing the right casting process is of the utmost importance in manufacturing. The process selected directly influences the quality, cost, and production speed of the final product. A method that is ideal for one part may not work as well for another due to differences in design complexity, material requirements, dimensional tolerance, or production volume.

Outsourcing casting requirements to a reliable and experienced casting provider, like Worthy Hardware, can be a strategic move for many businesses. It allows companies to leverage the casting provider's expertise and sophisticated equipment, ensuring that the final product is of high quality and meets all specifications.

Worthy Hardware has a wide range of capabilities, covering different casting processes such as sand casting, die casting, investment casting, and more. Their team of skilled professionals can guide you in choosing the most suitable casting method for your product, ensuring optimal performance and cost-efficiency. They can handle the entire production process, from pattern creation and mold preparation to final finishing, relieving you of these complex tasks.

By entrusting your casting needs to Worthy Hardware, you can focus on your core competencies, enhancing your productivity and competitiveness in the market. Their commitment to quality, timely delivery, and customer satisfaction makes them a trustworthy partner for your casting needs.

Contact us to discuss your requirements of Expendables Refractory(ja,es,it). Our experienced sales team can help you identify the options that best suit your needs.