Casting Process| Exploring the 7 Types of Die Casting

Casting Process| Exploring the 7 Types of Die Casting

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The rising industrial demands and applications have increased the requirement for sophisticated and top-notch products. Thankfully, there exist numerous casting methods capable of producing intricate and precise products to cater to diverse user needs and applications.

To ensure the selection of the most suitable casting method for one's manufacturing requirements, it is crucial to comprehend the advantages and disadvantages of different types of casting. This article provides a concise summary of various casting methods and their respective pros and cons.

Brief Introduction to the Casting Process 

The casting process is a manufacturing technique that creates metal parts of desired shapes by pouring molten metal into a mold and allowing it to solidify and cool to room temperature. This method is capable of producing intricate and complex parts, regardless of their size.

Casting enables the production of isotropic metal parts in large quantities, making it ideal for mass production. Moreover, various casting types exist, utilizing different materials and molds, to cater to specific user requirements.

Categories of Casting Manufacturing Process

A variety of casting processes exist, providing versatile options for creating metal parts of different shapes and sizes. For casting type, each technique offers distinct characteristics to cater to specific industrial needs and material requirements.

Sand Casting Process

Sand casting, a type of casting process, finds extensive use in industrial units for mass-producing automotive metal casting parts like engine blocks, cylinder heads, and crankshafts. This method involves a mold composed of silica-based materials, such as naturally-bonded or synthetic sand, which creates a smooth mold surface. The mold comprises two sections: the cope (upper half) and drag (lower half). Molten metal is poured into the pattern via a pouring cup, and left to harden into the desired shape. The final step involves removing excess metal to achieve the finished metal-casting product.

The sand casting process finds extensive application in various industries for producing metal components with a wide range of shapes and sizes, including automotive engine blocks, aerospace turbine blades, and heavy machinery parts. It is also commonly used in the production of architectural elements like ornamental fixtures and sculptures

Investment Casting Process

Investment casting, or lost-wax casting, is a precise manufacturing process used to create intricate metal components. It involves creating a wax or plastic pattern, assembling it with gating systems, and coating it with a ceramic shell mold. The pattern is then melted and removed, leaving behind a cavity. The shell mold is preheated and filled with molten metal, which is allowed to cool and solidify. Finally, the shell is removed, revealing the final cast product.

The advantages and disadvantages of investment casting can be summarized as follows:

Investment casting is applied in industries including aerospace, automotive, jewelry, and medical manufacturing for producing complex and detailed metal components.

Pressure Die Casting Process

There are two types of pressure die casting based on the pressure applied: high-pressure die casting and low-pressure die casting. High-pressure die casting is commonly used for mass production of intricately shaped components that require high precision. On the other hand, low-pressure die casting is preferred for the production of larger and simpler components.

In both types of die casting, nonferrous metals and alloys like zinc, tin, copper, and aluminum are injected at high pressure into a reusable mold coated with a lubricant. The goal is to prevent the metal from solidifying during the rapid injection process, which is why high pressure is maintained. After the casting process is complete, extraction and finishing are carried out to remove any remaining material.

It is important to note that pressure die casting differs from gravity die casting, as pressure die casting involves the injection of molten metal into a metal mold under high pressure. The molten metal quickly solidifies to achieve the desired outcome.

Pressure die casting is applied in industries such as automotive manufacturing for engine components, aerospace for lightweight components, and consumer electronics for mass production of intricate parts.

Plaster Casting Process

Plaster casting shares similarities with sand casting, but instead of sand, it uses a mixture of gypsum, a strengthening agent, and water. An anti-adhesive coating is usually applied to the plaster pattern to prevent it from sticking to the mold. Plaster can fill gaps in the mold effectively. However, once the part is cast, the plaster material commonly develops cracks or defects, necessitating replacement with fresh material.

Plaster casting finds application in various industries including art and sculpture, architecture and construction, prototyping and design, ceramics and pottery, dental and medical, education and crafts, and restoration and replication.

Centrifugal Casting Process

Centrifugal casting, also referred to as roto casting, is one of the types of cast iron used for manufacturing cylindrical parts by utilizing centrifugal forces. In this method, a heated rotating die is employed to pour molten metal, which is then distributed within the die under high pressure due to the centrifugal forces.

There are three variations of centrifugal casting: true centrifugal casting, semi-centrifugal casting, and vertical centrifugal casting. Semi-centrifugal casting differs from true centrifugal casting in that the mold is filled using a sprue. In true centrifugal casting, the continuous rotation causes the molten metal to adhere to the sides. Meanwhile, vertical centrifugal casting follows the same process as true centrifugal casting but involves directional molding.

Centrifugal casting is typically used to produce rotational shapes such as cylinders. It is commonly employed for manufacturing parts like bush bearings, clutch plates, piston rings, and cylinder liners. Pouring the metal in the center of the mold helps minimize defects such as blow holes, shrinkage, and gas pockets. However, it may not be suitable for all types of metal alloys.

Initially employed for casting pipes, centrifugal casting has now become widely utilized in various industries such as metallurgy, mining, transportation, irrigation machinery, aviation, national defense, and automotive. This technique is utilized to produce steel, iron, and non-ferrous carbon alloy castings. Common applications include the production of centrifugally cast iron pipes, cylinder liners for internal combustion engines, and shaft sleeves.

Lost-Foam Casting Process

The lost-foam casting method is an alternative to investment casting where a foam pattern is used instead of a wax pattern. Once the foam pattern is created, it is coated with a refractory ceramic material through dipping, spraying, or brushing. The molten metal is then poured into the mold, which vaporizes the foam and fills the void to create the desired product.

This casting process can be applied to a wide range of materials, including alloy steel, carbon steel, alloy cast iron, and ferrous alloys. It is commonly used for producing products such as pump housings, fire hydrants, valves, and fittings.

Shell Molding Process

Shell molding is a type of casting process that falls under the category of expendable mold casting. It shares similarities with sand casting, however, the primary difference lies in the mold cavity formation. Instead of using a traditional sand flask, a hardened shell composed of fine sand is employed to create the mold cavity. This sand is of a finer grain size compared to that used in sand casting, and it is mixed with a resin. The resin allows for heat treatment, enabling the sand to be thermally processed and solidified into the shell surrounding the desired pattern.

Shell molding finds application in the production of various industrial items like gearbox housing, connecting rods, small-sized boats, vehicle hoods, cylindrical heads, camshafts, and valve bodies.