Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify.
The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process.
Advantages of casting process:
- Molten metal flows into ant small section in molten cavity, hence any complex shape can be easily produced.
- Practically any type of material can be casted.
- Due to small cooling rate from all directions, the properties of casting are same in all directions.
- Any size of casting can be produced like up to 200 tonnes.
- Heavy equipment like machine leads, ship’s propeller etc. can be cast easily in the required size rather than fabricating them by joining several small pieces.
- Transport : Automobile, aerospace, railways and shipping
- Heavy Equipment : Construction, farming and mining
- Machine Tools : Machining, casting, plastics molding, forging, extrusion and forming
- Plant Machinery : Chemical, petroleum, paper, sugar, textile, steel and thermal plants
- Defense : Vehicles, artillery, munitions, storage and supporting equipment
- Electrical Equipment Machines : Motors, generators, pumps and compressors
- Household : Appliances, kitchen and gardening equipment, furniture and fittings
- Pattern is defined as a model or replica of an object to be cast
- The type of pattern to be used for a particular casting depends upon many factors like design of casting, complexity of shape, number of casting required [bulk of casting], mould process, surface finish and accuracy.
Functions of the Pattern
- A pattern prepares a mold cavity for the purpose of making a casting.
- A pattern may contain projections known as core prints if the casting requires a core and need to be made hollow.
- Runner, gates, and risers used for feeding molten metal in the mold cavity may form a part of the pattern.
- Patterns properly made and having finished and smooth surfaces reduce casting defects.
- A properly constructed pattern minimizes the overall cost of the castings.
Features of the Pattern material
- Easily worked, shaped and joined
- Light in weight
- Strong, hard and durable
- Resistant to wear and abrasion
- Resistant to corrosion, and to chemical reactions
- Dimensionally stable and unaffected by variations in temperature and humidity
- Available at low cost
Cheap, easily available, light, easiness in surfacing, preserving (by shellac coating), workable, ease in joining, fabrication
- Moisture effects, wear by sand abrasion, warp during forming, not for rough use.
- Must be properly dried/ seasoned, free from knots, straight grained
Egs. Burma teak, pine wood, mahogany, Sal, Deodar, Shisham, Walnut, Apple tree