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Special Casting Methods
Special casting methods are typically used to create intricate parts with complex geometries. These casting methods offer greater design flexibility than many traditional methods and require specialized techniques, tools and materials which must be considered when selecting a casting method.
Investment Casting
This method is often referred to as the lost wax process. Investment casting is ideally suited for detailed, intricate parts that must hold close dimensional tolerances. The investment casting process involves the making of a wax or plastic pattern of an object from an engineered CAD design. This pattern is then placed in a ceramic mold where it is coated with additional ceramic material. The mold is then heated to melt away the wax or plastic, creating a void in the center of the ceramic mold. Molten metal alloy is then poured into the void and allowed to cool, forming the metal part.
Die Casting
Die casting is a metal casting process that involves injecting molten metal under high pressure into a die cavity. It is often used for parts with integrated moving components, such as automotive and electronics parts. The general method includes producing a die from a hardened steel tool, placing it in a die-casting machine, melting the metal alloy in a furnace and injecting it into the die. After the die is filled, the part is cooled and ejected from the die.
Permanent Mold Casting
This method is good for making multiple identical parts. It involves the use of an iron or steel mold along with a gravity feed system, ensuring that the molten metal will flow evenly into the mold. It is then allowed to cool, solidifying the metal into the desired shape. Permanent mold casting can be used to produce small, low-volume runs of parts, such as those used in the aerospace industry.
Vacuum Casting
Vacuum casting is a method used to create parts with intricate, complex details. It involves the use of a vacuum-controlled environment to reduce gas pockets and other defects in the casting. This process requires that ceramic mold is placed in a vacuum chamber and is then filled with a liquid resin material which is then heated and cured. The resulting part retains all of the details of the original model.
Low Pressure Casting
Low pressure casting is similar to the die casting process, however it involves the use of atmospheric or higher pressure than in die casting to force molten metal into a cavity. This method is often used for making automotive, aerospace and medical components as it can create parts with tighter tolerances than die casting.
Centrifugal Casting
Centrifugal casting is used for the production of parts with internal features and complex external features. This process involves the use of centrifugal force to place the molten metal into a specially-designed mold that is rotated at high speeds. This process yields parts with a smooth, uniform external surface and a strong internal core structure.
Heat Treating and Plating
Heat treating and plating are processes used to improve both the aesthetic and functional qualities of cast parts. Heat treating is often used to improve the strength and wear-resistance of metals, while plating can be used to provide increased corrosion resistance. These processes can also be used to create parts with highly polished surfaces.
Conclusion
When selecting a casting method, it is important to consider the design, strength, tolerances and material requirements of the parts that need to be produced. Each casting method offers certain advantages and should be carefully evaluated together with the application requirements in order to choose the best casting method for the job. Understanding these special casting methods and their associated processes can help to ensure that the desired parts are produced in the most efficient manner.
