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.
Please read :
Basic Operation of the casting process
Pattern is the object used to make cavity in the mold. The molten metal is poured into this cavity.
Criteria for selecting a furnace for casting
Casting Defects
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.
Please read :
- Comparison of different casting processes.
- What is casting ? Main application of castings
- Basic Steps of Sand casting
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
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.
Pattern Materials
- Wood
- Cast Iron / Brass
- Aluminum or White metal
- Plastic gypsum
For a complete knowledge of pattern materials go to this link
Pattern Allowances
- 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)
For a complete knowledge about the allowances in patterns follow this link
Different Types of Patterns used in Casting
- Split piece pattern
- Match plate pattern
- cope and drag patterns
- sweep patterns
- draw backs
- Loose piece pattern
- Gated pattern
Follow : A complete guide to casting patterns
Preparing Mould for the Casting
While preparing mould one should be very careful . Different types of sands and binders are used in mould preparation. These are
Green sand mould: Natural sands , clay and water is used in making green sand mould. It is very cheap with acceptable errors.
Dry Sand Mould: It is natural sand mould with cereal and pitch used binders.
Other materials for mould preparation includes silica sand and binder with additives.
Please Read :
Different Properties of the moulding sand
These are the desired properties of the moulding sand
- Refractoriness
- Cohesiveness
- Permeability
- Co-efficient of expansion
- Adhesiveness
- Collapsibility
- Plasticity
For details of each of the properties follow this link :
Tests for the different moulding sands
- Moisture Content Test
- Fineness Test
- Testing Amount of Clay
- Permeability Test
- Mould hardness test
- Strength or cohesiveness test
Core Making
What is Core ?
It is a structure made of refractory material . It is prepared before pouring the molten metal on to the cavity. There is another term known as core print which is the projection on a pattern used to make spaces in the mould. It is also known as core seat.
Criteria for selecting a furnace for casting
- Capacity needed to hold the molten metal
- Melting rate
- Quality of the melt
- Temperature needed
- Method of pouring
Operation in Cupola Furnace
Cupola is the most popular furnace for casting non ferrous and ferrous materials . It is known as a shaft furnace. The shell of cupola furnace is made of steel of 8-10 mm thickness. The shell is supported by columns or legs. The inside of the furnace is lined with refractory material to save the furnace from over heating.
Different types of casting processes
- 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.
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