Sand casting is a process in which the material is heated to molten state, then poured into a mould with the desired cavity and allowed to solidify. Casting is the pattern that we get after solidification. When the process is finished, the casting is removed from the mould. Metals are the most common materials used in casting.
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Sand for casting
Sand casting process uses sand for the preparation of mould. Sand casting uses synthetic sand(lake sand) or natural sand which is usually a refractory material called silica (SiO2).
The sand grains must be sufficiently small in order that it can be packed densely; however, the grains must be large enough to permit gasses formed during the metal pouring to escape through the pores.
Green sand (a mixture of sand, water, and clay) is commonly used in larger moulds. Sand is often re-used, and excess metal poured is trimmed or cut-off and re-used also.
Sand Casting Mould | Sand Casting Equipment
Sand casting mold typically have the following parts:
Cope and Drag: The mold is made of two parts, the top half of the mould is called the cope, and bottom part is called the drag.
The liquid pours into the mould cavity, which is the space between the two pieces. A wooden object called the pattern is used to create the cavity’s geometry. The patterns have a shape that is (nearly) identical to the part we need to create.
Pouring Cup and Sprue: The liquid metal is poured into the pouring cup and flows down the sprue; the top of the funnel is the pouring cup; the pipe-shaped neck of the funnel is the sprue.
Runners: The runners are the horizontal hollow channels that connect rock bottom of the sprue to the mould cavity.
Gate: The region where any runner joins with the cavity is named the gate.
Risers: Some extra cavities are made connecting to the highest/top surface of the mold. Excess metal poured into the mould collects in these spaces/cavity, which are referred to as risers. They act as reservoirs; because the metal solidifies inside the cavity, it shrinks, and therefore the extra metal from the risers flows backtrack to avoid holes within the cast part.
Vent: Vents are narrow/small holes connecting the cavity to the atmosphere to permit gasses and the air within the cavity to escape. .
Cores: Many cast items feature interior holes (hollow portions) or other cavities that aren’t accessible from either component/piece of the mould. Such interior surfaces are formed by inserts that called cores.
Cores are made by baking sand with some binder in order that they will retain their shape when handled. The mould is put together by inserting the core into the drag’s cavity, then placing the cope over top and securing/locking the mould. After the casting is completed , the sand is shaken off, and therefore the core is pulled away and typically broken off.
Sand Casting Plant
Sand casting plant typically consists of the following section/areas:
- Pattern plate making section
- Core making section
- Sand Preparation section
- Sand moulding section
- Melting section
- Metal pouring line
- Casting shakeout or Degating section
- Fettling and Grinding section
Sand Casting Process
The sand casting process steps include:
- a) Getting mechanical drawing of the part.
- b) Preparation of Cope pattern, and
- c) Preparation of Drag pattern plate as per drawing.
- d) Making of core boxes.
- e) Core halves pasted together.
- f) Cope mould readiness for sand.
- g) Cope mould ramming with sand and removal of pattern, sprue, and risers.
- h) Drag mould readiness for sand.
- i) Drag mould ramming and Pattern removal.
- j) Core set placing on Drag.
- k) Cope and drag assembly readiness for metal pouring.
- l) Removal of casting from the mould for cleaning and heat treatment.
- m) Casting finishing process like grinding and shot blasting if applicable.
- n) Casting dispatch to the customer.
Sand Casting products | Uses
Sand Casting is a method of producing complex machine parts and widely used at various sectors/areas as mentioned below:
- It is used to make various parts in the automobile industry, aeroplanes, trains, and shipping.
- It’s used to make motors, generators, pumps, and compressors, among other things.
- It is also used to make various hardware products like plumbing pipes, couplings, fittings, valves, and so on.
Sand casting advantages
- Sand Casting is a very old method of moulding any material into the desired shape.
- Complex machine parts can be produced easily with the desired quality.
- Casting is used to create intricate structures that are difficult to manufacture commercially using other methods.
