We know that casting is the process of pouring molten metal in a desired shaped cavity and allowing it to solidify. After the solidification we get the desired shaped object.
Basic Operation of the casting process
- First we have to make a pattern
- Then the we have to melt the metal by applying heat
- pouring the metal into the mold and confirming that the metal gets the desired shape.
What is Pattern in Casting Process
Pattern is the object used to make cavity in the mold. The molten metal is poured into this cavity.
Why a good Pattern is required in casting ?
- To obtain the desired shape and size.
- It is easy to design and manufacture.
- making a pattern is not expensive.
- It is of high strength.
- Cast Iron / Brass
- Aluminum or White metal
- Plastic gypsum
- Shrinkage allowance (due to cooling)
- Machining allowance (due to machining)
- Shaking allowances (due to rapping)
- Draft allowance (follow the link)
- Distortion allowance (due to irregular shape)
- Split piece pattern
- Match plate pattern
- cope and drag patterns
- sweep patterns
- draw backs
- Loose piece pattern
- Gated pattern
Preparing Mould for the Casting
Different Properties of the moulding sand
- Co-efficient of expansion
- Moisture Content Test
- Fineness Test
- Testing Amount of Clay
- Permeability Test
- Mould hardness test
- Strength or cohesiveness test
- Capacity needed to hold the molten metal
- Melting rate
- Quality of the melt
- Temperature needed
- Method of pouring
- Sand Casting
- Shell Mold Casting
- Expandable Mold Casting
- Plaster Mold
- Ceramic Mold
- Investment Mold or Lost Wax Casting
- Permanent Mold
- Die Casting
- Centrifugal casting
And lastly comes the casting defects. These defects can occur for different reasons like air trapping in the sand mold, low quality sands, improper ramming , defecting sand mold etc. Go through this link for detailed knowledge of casting defects.
- Different types of casting defects