What is Casting process | Advantages , Disadvantages and Application
Virtually nothing moves, turns, rolls, or flies without the benefit of cast metal products. The metal casting industry plays a key role in all the major sectors of our economy. There are castings in locomotives, cars trucks, aircraft, office buildings, factories, schools, and homes. Casting means pouring molten metal into a mould with a cavity of the shape to be made, and allowing it to solidify. When solidified, the desired metal object is taken out from the mould either by breaking the mould or taking the mould apart.
The solidified object is called the casting. By this process, intricate parts can be given strength and rigidity frequently not obtainable by any other manufacturing process. The mould, into which the metal is poured, is made of some heat resisting material. Sand is most often used as it resists the high temperature of the molten metal.
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Casting processes divide into two broad categories
- Expendable-mold casting (Sand Casting)
- Permanent-mold casting (Die Casting)
- One of the earliest metal shaping methods known to human being.
- It is the Process in which molten metal flows by gravity or other force into a mold where it solidifies in the shape of the mold cavity.
- Commonly, the term casting also applies to the part made in the process.
- The process can be applied on metals, ceramics and plastics.
- The term casting is commonly used for metals.The term molding is used for plastics.
- Examples of molds – cake-pan, an ice-cube-tray or the
- Types of castings – sand casting and die casting
- Sand casting – pouring molten metal into a sand mold, breaking up the mold to remove the casting. Sand casting requires a pattern – a full sized model of the part.
- Die casting is a permanent-mold-casting – molten metal is injected into the mold cavity under high pressure. Molds for die casting are named as dies.
- Casting is usually performed in a foundry.
Foundry: Factory equipped for making molds, melting and handling molten metal, performing the casting process, and cleaning the finished casting.
- Workers who perform casting are called foundrymen.
- Simple Steps in casting:
1. Prepare mould (using pattern) /die
2. Melting and pouring molten metal into a mould/die.
3. Let it solidify ( Solidification and cooling)
4. Removal, Cleaning, Finishing and Inspection processes
- Casting can be used to create complex part geometries, including both external and internal shapes.
- Some casting processes are capable of producing parts to net shape. (No further manufacturing operations are required to achieve the required geometry and dimensions of the parts.)
- Other casting processes are near net shape, for which some additional shape processing is required (usually machining) in order to achieve accurate dimensions and details.
- Casting can be used to produce very large parts. Castings weighing more than 100 tons have been made.
- The casting process can be performed on any metal that can be heated to the liquid state.
- Some casting methods are quite suited to mass production.
Different disadvantages for different casting methods.
- limitations on mechanical properties
- poor dimensional accuracy and surface finish for some casting processes,
- safety hazards to humans when processing hot molten metals,
- Environmental problems.
- Parts made by casting processes range in size from small components weighing only a few ounces up to very large products weighing tons.
- The list of parts includes dental crowns, jewelry, statues, wood-burning stoves, engine blocks and heads for automotive vehicles, machine frames, railway wheels, frying pans, pipes, and pump housings.
- All varieties of metals can be cast, ferrous and nonferrous.
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