Casting Process

Metal casting is the most common process used to manufacture and design variety of components and finished products. It can be used to manufacture variety of products ranging from nail and fasteners to large machines and engine block. Almost every type of metal can be casted into various shapes and sizes based on the requirement of the customers. Most popular and commonly used metal casting processes are sand casting, investment casting, precision metal casting, precision sand casting, centrifugal casting, die casting, lost foam casting, permanent mold casting etc. We have broadly categorized the casting process into two categories Hot Forming Process and Cold Forming Process.

Hot forming process is widely used to cast variety of industrial products and parts. In the process the metal is heated at high temperature to soften the piece. The metal may be available in the form of sheet, wire, tube or bar. The preheated metal is pressed, pounded or squeezed under external pressure to give it a desired shape. The hot-formed products have a relatively high tolerance and can be produced in variety of shapes.

The following casting processes can be categorized under Hot Forming Process:

• Centrifugal Casting - In centrifugal casting, a permanent mold is rotated at a high speed as the molten metal is poured. The molten metal is centrifugally thrown toward the inside of the wall where it solidifies after cooling. The castings have a very fine-grained outer diameter and are resistant to atmospheric corrosion. This process is widely used in manufacturing of pipe.
• Ceramic Mold Casting- This process is similar to plaster mold casting. The pattern used in ceramic mold casting is made of plaster, plastic, wood, metal or rubber. The slurry is poured over the pattern, which hardens rapidly. The pattern can be peeled and reassembled as mold.
• Extrusion- Extrusion is the manufacturing process used to produce long objects of a fixed cross-sectional profile. The shape of cross section can be solid round rectangular, T shapes, L shapes, Tubes etc.
• Forging- Forging is the process of shaping material by using localized compressive forces. It is used to produce parts with excellent properties and minimal wastage. In the process the metal is heated up by applying compressive force and given shape by plastic deformation. The compressive force is applied by hammer blows using a power hammer or a press.
• Investment Casting - Also known as lost wax method casting, investment casting is one of the oldest known metals forming techniques. The process is generally used for small castings complex shapes or airplane parts that can withstand high temperature. Metals, which are hard to machine or fabricate, can easily be casted using this process.
• Full Mold Casting- Full mold casting is very much similar to investment casting, but instead of wax as the expandable material, the polystyrene base is used as the mold. The foam pattern is coated with refractory crucible. As the metal is poured the foam vaporizes and metals takes it's place forming a permanent shape. It is one of the most convenient methods for casting complex shapes.
• Permanent Mold Cast- In this process typically cast iron or Meehanite (a dense cast iron) is used as the mold material. The cores are made from metal or sand. Cavity surface is sealed with a thin layer of heat resistant material such as clay or sodium silicate. The molds are pre-heated at a temperature upto 200ºC (392ºF) before the metal is poured into the cavity. Proper precaution is taken to ensure thermal balance. This process is used for casting common materials used are small and medium sized parts made of aluminum, magnesium and brass
• Plaster Mold Casting- Also known as Rubber Plastic Molding (RPM), Plaster Mold Casting is a method of producing aluminum or zinc castings by pouring liquid metal into plaster (gypsum) molds. The process provides casting with smooth surface, intricate details and greater dimensional accuracy.
• Powder Metallurgy- In the process the metal powders are injected into the mold and passed through the die to produce weakly cohesive structure. The metal powder is compressed in the presence of high temperature just below the melting point of the metal.
• Sand Casting- Sand casting is the most common and cost effective methods of producing complex shapes. This process is used to make large parts (typically Iron, but also Bronze, Brass, Aluminum. The molten metal is poured into a mold cavity formed out of sand. This mold cavity gives the molten lava the desired shape.
• Shell Mold Casting- This process of casting is similar to Sand Casting except that a mixture of sand and 3-6% resin holds the grains together. Shell mold casting offers better surface finish, high dimensional tolerances, and increased output due to reduced cycle times.