Explain the three stages involved when performing sand casting. Sketch and label in section the completed mould assembly ready for pouring the molten metal when performing sand casting.

Here are the components of a completed sand mould assembly ready for pouring:

1. Cope and Drag: These are the top (cope) and bottom (drag) halves of the moulding flask, which contain the sand mould.
2. Mould Cavity: This is the impression created in the sand, which will form the external shape of the desired casting.
3. Core: If the casting requires internal features or hollow sections, a pre-formed core (often made of sand) is placed within the mould cavity.
4. Gating System: This network of channels guides the molten metal into the mould cavity. It includes:
   • Pouring Basin/Cup: The funnel-shaped opening where molten metal is initially poured.
   • Sprue: A vertical channel leading from the pouring basin downwards.
   • Runner: A horizontal channel connecting the sprue to the gates.
   • Gates: The entry points through which molten metal flows from the runner into the mould cavity.
5. Riser: A vertical reservoir of molten metal connected to the mould cavity. It feeds additional molten metal to the casting as it solidifies and shrinks, preventing defects.
6. Vents: Small passages or holes in the mould that allow gases (steam, air, combustion products) to escape from the mould cavity as the molten metal fills it, preventing gas defects.