6 Types of Casting Processes for Manufacturing

An Overview of Casting

Casting has been a manufacturing process for centuries. It is a vital part of the evolution of human civilization. Pouring liquid (usually molten steel) into a mold to solidify the component. This is a basic technique used in the modern manufacturing industry. It allows for complex parts to be created with accuracy, reliability and efficiency.

CFS Foundry is a leading metal-casting manufacturer in China. We use a range of casting techniques to produce a wide variety of intricate designs.

The Basic Steps in Casting Process

1. Pattern Making: This is one of the first steps and the most critical in the casting procedure. A pattern is the exact copy of an exterior casting. It’s typically made of wax or wood, and should take into consideration the final casting shape as well as the shrinking, solidification, and hardening of the casting material. The pattern can be broken down into several parts to allow it to easily be removed.

2. Mold Preparation: The next step in the production process is to prepare the mold. This is basically a cavity, into which molten steel will be poured. Sand is then pressed into place around the moulding pattern. The sand is bound together using clay, chemical binders or other binding agents. Once the sand was tightly packed, the pattern could be removed. It will leave a cavity of sand in the shape of that pattern. The cores of the mold are used to form internal features.

3. Pouring: Pouring involves heating up the metal until the melts. It is then carefully poured into a mold. Pouring should be done carefully to avoid any defects. The molten steel should be held at the right temperature. This will ensure that it stays liquid until filling the mold. Pouring metals must be free of any impurities. It should also be done so as to prevent turbulence. This could lead to air being trapped in the cast or an incomplete filling.

4. Solidification: Solidification begins after the metal cools down. During the solidification process, metals undergo a phase transition from a state of liquid to one of solid. This phase involves shrinkage. To compensate this, risers can be used to add more molten steel into the casting. It is important to consider the cooling rate, as it affects the microstructure and mechanical properties of a casting.

5. Ejection: After the metal solidifies, the sand-mold can be broken to remove the casting. This step may be challenging in some cases, such as when the casting is intricate and sand can become stuck in the passageways. Often, the sand left behind after removing the casting can be recycled and used in future molds.

6. Cleaning and Inspection: Even after the casting is ejected the surface may still be covered by sand or have metal fragments attached. Cleaning involves removing the impurities from the surface and trimming off any excess metal. After the casting has been cleaned, it should be checked to ensure that it complies with all specifications. Inspection includes a variety of techniques, such as visual inspections, dimension checks, and nondestructive testing methods ( ultrasonic tests or radiographic examinations).

Each of these stages requires careful control as well as an understanding of material properties. Casting, when performed correctly, can be used to create complex parts made of a wide variety or alloys. This allows for flexibility and adaptation in the rapidly changing world of manufacturing.

6 Different Types of Casting Processes

Investment Casting

Investment casting is one of the main casting type at CFS Foundry. This technique is commonly referred to as precision casting or lost-wax casting, dates back thousands of years. It is known for its great precision, repeatability, and integrity.

Investment casting process starts from creating a wax pattern of the desired shape, then coating it with a ceramic shell that hardens and forms a mold. Once this mold is ready, wax can be melted away from its cavity. Next, pouring molten metal into the mold. After the metal cools and solidifies, the ceramic mold can be broken away to achieve the final cast product.

Investment casting is often selected when components require intricate detail, complex geometries or require a smooth surface finish. This type of casting process must approve strict quality inspection, and can be used to produce both precision metal parts in both small or large production runs.

Pros and Cons of Investment Casting:

Pros Cons
High Precision and Accuracy: Producing parts with excellent surface finish quality and dimensional accuracy, reduces the need for secondary machining operations Higher Cost: Due to materials and labor costs involved in creating wax patterns and ceramic molds, investment casting costs more than other casting types.
Complex Geometry: Enables creation of parts with intricate details and complex geometries which may otherwise be challenging or impossible using other casting methods. Longer Lead Time: As this process involves multiple steps, its lead time may extend more significantly compared to other casting processes.
Versatile Material Options: Ideal for producing various metals and high-performance alloys, such as stainless steel casting, other steel casting, and nickel based alloy casting. Size Limitations: This technique tends to work best with smaller parts; larger components can prove challenging and costly when made using this method.
Smooth Surface Finish: Smooth finishes require minimal surface finishing, saving both time and costs in post-processing. Wax Pattern Creation: Each casting requires its own wax pattern which adds time and cost.
Reduced Material Waste: Due to its precision, this process ensures minimal material wastage, making it more eco-friendly. Limited Capacity: More suitable for small to medium production runs.

Lost Foam Casting

Lost Foam Casting

Lost foam casting (also referred to as evaporative pattern casting) is an innovative casting method with unparalleled accuracy and surface finish. To begin the lost foam casting process, typically made out of polystyrene foam patterns are created for each part and coated with refractory material to form an outer shell of thin shell casting material. It’s then embedded in a flask filled with unbounded sand, and the molten metal is poured directly onto the foam, causing it to vaporize and create a cavity for the metal.

This casting method is suitable for producing complex parts, especially those that would require cores in traditional sand casting. The process virtually eliminates the need for parting lines or draft angles, which means that no flash is formed, reducing the need for cleaning and finishing.

Pros & Cons of Lost Foam Casting:

Pros Cons
Complex Geometries: Foam patterns allow for the creation of complex geometric designs not possible with other casting processes, often unfeasible when cast. Pattern Cost: Foam patterns may cost more to create compared with other types of patterns used for casting processes.
Excellent Surface Finish: Producing an outstanding surface finish reduces post-processing requirements significantly. Porosity Issues: However, casting parts could result in porosity issues which compromise their structural integrity.
No Parting Lines or Cores Needed: Lost foam casting makes design simpler by eliminating parting lines or cores, which helps reduce defects. Limited Material Choice: Not all metals are suitable for lost foam casting, limiting the choice of materials compared to other casting methods.
Reduced Waste and Minimal Scrap: This method generates minimal waste and scrap, contributing to its eco-friendliness and cost-effectivenes. Size Limitations: Larger castings may present challenges due to limitations associated with foam pattern creation and handling.
Reduced Machining Requirements: Due to its accuracy, additive manufacturing processes typically eliminate the need for secondary machining operations. Consistency Challenges: Producing consistent results may prove challenging when applied to complex or large parts.

Sand Casting

Sand Casting

Sand casting is one of the oldest and most reliable type of casting, dating back centuries. With its long history, this method still remains versatile enough for manufacturing metal parts efficiently and affordably. The process involves pressing an exact replica of your desired part into a mold made out of sand mixture before pouring molten metal into its cavity to solidify in turn and breaking away from its mold once solidification occurs.

Sand casting is an economical method of producing large or heavy parts in short run productions, especially at higher volumes. Although its details and surface finishes do not match other casting methods, advances in molding materials and techniques have increased accuracy and surface finish of sand-casted parts significantly.

Pros & Cons of Sand Casting:

Pros Cons
Cost Effective for Small Batches: It is ideal for low-to-medium volume production as it is relatively cheap compared to the other casting types. Lower Dimensional Precision: Parts have lower dimensional precision and a rougher surface finish than other casting types. This often requires additional machining.
Flexible Design Option: Can produce a variety of shapes and sizes, from very small parts to large components. Greater Material Waste: Because sand molds can’t be reused, they result in a higher waste of material compared to other casting methods.
Material Versatility: Casts nearly any metal alloy. Porosity Risks: Castings are at higher risk for porosity, which can impact the mechanical properties.
Easy Setup and Equipment: Does not require as much equipment and is less expensive than other casting techniques, making it more accessible to small-scale operations. Post Processing Requirements: May require extensive finishing, such as grinding and machining to achieve the desired finish.
Ideal Castings for Large Parts: Especially suited to create large parts which would be difficult or costly to produce with other casting methods. Lengthening of Cycle Time: The production cycle can be extended if the process is slower, particularly in the preparation and drying of molds.

Die Casting

Die Casting

Die casting is widely used to creat light metal parts due to its ability to produce components with precise dimensions and efficiency. Die casting works by injecting molten metal at high pressure into steel dies comprising multiple sections. According to pressure used, die casting may be divided into high pressure die casting or low pressure die casting processes.

High-pressure die casting is well suited to mass producing complex shapes with thinner walls and tighter tolerances, while low-pressure die casting should be utilized when surface appearance and soundness of casting is of primary concern. Gravity die casting, another die casting type available today, works similarly – wherein liquid metal is poured directly into a die without external force being necessary.

Pros & Cons of Die Casting:

Pros Cons
High Productivity: Ideal for large-scale productions with short cycle times. High Initial Cost: Die casting machines and molds are expensive, so they are not economical for small production runs.
High Dimensional Accuracy Produces high-precision and consistent parts, often reducing or eliminating the need for extra machining. Limited Material Options: Mainly for non-ferrous materials like aluminum, magnesium, and zinc. Due to their high melting points, ferrous metals are used less often.
Good Surface Finish: Most parts have a smooth, rounded surface that may only require minor finishing. Air Pockets and Structural Integrity: Parts can have small air pockets (porosity) which can impact surface finish.
Complex Parts Design: allows for the creation and manufacture of intricate shapes, complex shapes, and complex details. Die Casting is Limited to Parts with Thinner Walls Although capable of producing parts with complex shapes, it is not generally suitable for parts that have very thick walls.
Automated Process: Can reduce labor costs, increase consistency and repeatability and can be highly automated. Thermal Fatigue on Dies: The repeated heating and cooling can cause thermal fatigue. This could reduce the life of the dies.
Minimal Waste: Effective use of materials, with the possibility to recycle excess or scrap material. Size Restrictions: Is best suited to smaller and medium-sized components. Larger parts are more difficult to manufacture, as well as more expensive.

Vacuum Casting

Vacuum Casting

Vacuum casting, as its name suggests, refers to casting under vacuum pressure of 100 bar or less to remove gasses from the mold cavity, and expel bubbles and air pockets from molten metal being poured into its mold cavity in a vacuum chamber during production. Vacuum evacuation reduces gas trapping during metal injection by decreasing air pockets within its structure during injection process; finally the metal is cured in a heating chamber and removed from its mold.

The vacuum die casting process has become widely utilized across industries such as automobiles, aerospace, electronics, marine and telecommunication. Some components produced via this casting type include structural chassis components and automobile body parts.

Vacuum casting is suitable for parts where internal soundness is important. It helps to eliminate inclusions and defects that can compromise the structural integrity of the casting. While it is a slower and more expensive process, the high-quality, defect-free parts it produces make it worthwhile for many critical applications.

Pros & Cons of Vacuum Casting:

Pros Cons
High Quality Surface Finish: Produces high-quality parts that closely resemble final production parts. Limited material choices: In general, the only materials available are polyurethanes or similar materials. These may not be suitable for all applications.
For Small to Medium Volumes: Vacuum casting is a cost-effective casting type for small to medium production runs. Durability and Strength: Cast parts may not be as durable or strong as those manufactured by other manufacturing processes, such as injection molding.
Rapid prototyping: Enables rapid turnaround of prototypes. This allows for faster design iterations. Size limitations: Typically used to produce smaller components; large components are more difficult and inefficient to manufacture.
Material Versatility: Can simulate different materials with different transparency, hardness and colors. Mold Wear: Silicone moulds can wear out after repeated use, affecting the consistency of parts produced.
Lower initial costs: In comparison to injection molding, tooling costs are much lower. This makes it ideal for small runs and prototypes. Not Suitable For Large-scale Production: This process is inefficient and expensive for high-volume manufacturing.
Capability to Produce Complex Geometries: Capable creating detailed and complex components without the need of expensive tooling. Manual Process: This process is labor intensive and requires technicians with specialized skills, which can result in variations in the quality of the parts.

Centrifugal Casting

Centrifugal Casting

Centrifugal casting is a casting method that uses centrifugal forces to produce castings. This process involves pouring molten metal into a rotating mould. The centrifugal forces push the metal against the walls of the mold.

It is particularly suitable for casting symmetrical components, such as rings or cylinders, because the rotational symmetry of the part can be used to achieve uniformity. Centrifugal casting does not require cores for the interior shape as the centrifugal forces ensure that the inner diameter conforms to the mold.

There are three types of centrifugal cast: true centrifugal, semi-centrifugal, and centrifuging. True centrifugal casts are primarily used to produce hollow cylindrical parts. Semi-centrifugal casts are used to produce parts that are symmetrical about the axis rotation. Centrifuging, on the other hand, is used to create parts with contours or projections at the top surface.

Due to the lack of inclusions and gas porosity, this process produces parts that are larger in diameter and have superior mechanical properties. Centrifugal casts are a good method to produce complex parts in high volumes, even though they require specific equipment.

These casting methods have remained popular in manufacturing because of their versatility and effectiveness. CFS Foundry’s expertise has helped CFS Foundry to master these casting methods. It is important to choose the casting method that will produce optimal results for your project. Each process has its own benefits and considerations. CFS Foundry can help any project reach its potential with the expertise and guidance provided.

Pros & Cons of Centrifugal Casting:

Pros Cons
High Material Pureness: Centrifugal forces drive impurities towards the inner surface of castings, resulting in higher-purity castings that have fewer defects. Shape Complexity Limited: Best for cylindrical shapes. Comparatively, complex geometries can be difficult to achieve with other casting methods.
Good Mechanical Properties: High-density cast parts have superior mechanical properties. Size Limitations: More efficient for small and medium-sized parts. Large castings are more difficult and costlier.
Reduced Secondary operations: Requires less machining and finishing than other methods because the surface finish and dimension accuracy are generally good. Equipment Cost: Need for centrifugal cast machinery that is specialized can result in higher initial investment costs.
Material-efficient Use: This method is material-efficient because it allows precise control of the thickness of the casting. Operational Skills Required: This requires skilled operators to control speed and temperature precisely, which adds operational complexity.
Material Versatility: Can work with a variety of metals and alloys. This allows for greater material flexibility. Safety Concerns: High-speed rotating molds present safety risks and require stringent safety equipment.

How to Choose A Right Casting Process?

How you select an ideal casting process depends on a number of factors, including material being cast, size and complexity of part to be cast, precision required, quantity needed as well as cost considerations. Here is a general guide that should help you select an effective process:

Material
Different casting processes are best suited to different materials. Die casting, for instance, is typically utilized when working with low melting point metals such as aluminum and zinc while sand casting offers versatile casting processes suitable for casting iron and steel alloys.

Size and Complexity
For large parts with relatively straightforward shapes, sand casting might be the right solution due to its scaleability and versatility. But for intricate forms with intricate details such as investment casting or die casting may provide better solutions.

Precision and Quality
For those in search of high precision and quality casting processes, investment casting offers superior surface finish quality as well as accurate dimensions. Die casting also delivers good dimensional accuracy with smooth surfaces finishes.

Production Volume
If your part production requirements require large-volume parts, die casting is often the most economical choice due to its rapid production cycle. For lower to medium volumes, other methods like sand or investment casting might prove more cost effective.

Tooling Costs and Lead Times
Die casting has higher tooling costs and longer lead times, yet lower per-unit costs for large volumes. Sand casting offers lower tooling costs with greater design flexibility.

Mechanical Properties
Take into consideration the mechanical properties needed in the final part. Certain casting processes can increase strength, ductility or other desired qualities in castings.

Economic Considerations
Budget should also be kept in mind. Although high upfront costs for tooling and setup might make sense for large production runs, for smaller batches or prototypes cheaper processes such as sand casting may be better suited.

Always bear in mind that these guidelines are just general in nature and that your project’s specific requirements will determine which casting process works best. Consultation with a casting expert or foundry can offer more detailed advice based on individual requirements.

Work with CFS Foundry for Your Casting Project

Casting is an art as much as it is a science, and it requires a balance of both to achieve perfection. CFS Foundry has been striking that balance for years, offering our clients a wide variety of casting methods to meet their unique manufacturing needs.

CFS Foundry has a reputation for maintaining high standards of quality, precision, and consistency. Our team is equipped with extensive experience and technical know-how, ensuring that every casting process is meticulously executed to match the customer’s specifications.

Whether you require the intricate precision of investment casting, the versatility of sand casting, or the speed and accuracy of die casting, CFS Foundry has the capability and expertise to make your project a success.

When you choose to work with CFS Foundry, you’re not just choosing a service. You’re choosing a partnership dedicated to bringing your vision to life, with the assurance of quality, efficiency, and a superior end product.

In the ever-evolving landscape of manufacturing, casting remains a steadfast and reliable method for producing a wide range of parts. With the right guidance and expertise from CFS Foundry, the possibilities of what can be achieved are limitless. Any source of a reliable casting company, contact CFS Foundry for a full solution today!

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