Casting and Molding Processes Manufacturing Chapter 9

Casting and Molding Casting is the word generally used when working in metal and ceramic materials. Casting is the word generally used when working in metal and ceramic materials. Molding is often used when working with plastics. Molding is often used when working with plastics.

What is Casting and Molding? An industrial material is first made into a liquid. An industrial material is first made into a liquid. The liquid is poured or forced into a prepared mold. The liquid is poured or forced into a prepared mold. The material is allowed or caused to solidify or harden. The material is allowed or caused to solidify or harden. The solid material is then removed from the mold. The solid material is then removed from the mold.

Steps in Casting There are five basic steps in casting. There are five basic steps in casting. A mold of proper shape is made. A mold of proper shape is made. The material is prepared for casting. The material is prepared for casting. The material is poured or forced into the mold. The material is poured or forced into the mold. The material is allowed to solidify. The material is allowed to solidify. The finished item is extracted from the mold. The finished item is extracted from the mold.

Molds The container for casting processes is called a mold. The container for casting processes is called a mold. The mold is simply a carefully prepared cavity. It must be the proper shape and size for casting to be successful. The mold is simply a carefully prepared cavity. It must be the proper shape and size for casting to be successful. There are two basic types of molds: expendable and permanent. There are two basic types of molds: expendable and permanent.

Expendable Molds Expendable molds are only used once. Expendable molds are only used once. They are broken down to remove the casting. They are broken down to remove the casting. Typically sand or plaster is used to make the molds. Typically sand or plaster is used to make the molds. This is an inexpensive way to cast. This is an inexpensive way to cast.

Permanent Molds Permanent molds can be used over and over again. Permanent molds can be used over and over again. They usually produce many castings before they wear out. They usually produce many castings before they wear out. The cavities in permanent molding are usually machined in which makes them more expensive to make. The cavities in permanent molding are usually machined in which makes them more expensive to make.

Permanent Molds Permanent molds are either gravity or pressure molds. Permanent molds are either gravity or pressure molds. Gravity molds are filled by pouring the material into the mold from the top. Gravity molds are filled by pouring the material into the mold from the top. Pressure molds must be built to allow the material to be forced into the cavity. Pressure molds must be built to allow the material to be forced into the cavity.

Preparing Material Casting requires a liquid or semi-liquid material. Casting requires a liquid or semi-liquid material. Most plastics and metal are heated to the molten or flowable state. Most plastics and metal are heated to the molten or flowable state. Some materials are suspended in a liquid. Some materials are suspended in a liquid.

Molding In die casting, nonferrous metals are melted in a pot then the molten metal is forced into the mold. In die casting, nonferrous metals are melted in a pot then the molten metal is forced into the mold. Injection molding is very similar, however melted plastic is being forced into the mold at this stage. Injection molding is very similar, however melted plastic is being forced into the mold at this stage.

Solidifying The material forced into a mold is solidified by cooling, drying, or a chemical reaction. The material forced into a mold is solidified by cooling, drying, or a chemical reaction. The solid part is then removed by destroying an expendable mold or opening a permanent mold. The solid part is then removed by destroying an expendable mold or opening a permanent mold.

In Summary Casting is the only process that directly converts an industrial material into a finished part in one major step. Casting is the only process that directly converts an industrial material into a finished part in one major step. It moves from a liquid to a sized and shaped part in a single process. It moves from a liquid to a sized and shaped part in a single process. Both metal and plastics may be molded by this process. Both metal and plastics may be molded by this process.

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