Foundry processes — identifying the permanent mould casting method Select the description that correctly corresponds to the permanent mould (gravity die) casting process used in manufacturing.

Introduction / Context:
Permanent mould casting, often called gravity die casting, is a key manufacturing process where a reusable metal mould is used and molten metal is poured by gravity. This question tests your ability to distinguish permanent mould casting from related processes such as slush casting, centrifugal casting, and pressure die casting.

Given Data / Assumptions:

• A permanent mould is metallic and reusable.
• Metal is poured by gravity (no high external pressure, and no mould rotation).
• The distractors describe other well-known processes.

Concept / Approach:
Match each description to its process definition. Permanent mould (gravity die) casting is simply pouring metal into a heated metal mould and allowing it to solidify completely under gravity, then opening the mould to remove the solid casting. No inversion to drain liquid core, no high-pressure injection, and no mould rotation are involved.

Step-by-Step Solution:
Identify option (a): draining the liquid core after a skin forms is the hallmark of slush casting used for thin hollow decorative parts.Identify option (b): solidification during mould rotation is centrifugal casting, typically for pipes, bushings, or rings.Identify option (c): forcing metal under high pressure is pressure die casting (hot- or cold-chamber machines).Permanent mould (gravity die) casting involves none of the above additional actions; therefore, among listed choices, the correct response is 'None of the above.'

Verification / Alternative check:
Process selection charts list gravity die casting as a medium-to-high rate process with reusable metallic dies and gravity feed, distinct from pressure die casting (pressure fed), centrifugal casting (rotating), and slush casting (drain-out technique).

Why Other Options Are Wrong:
(a) Describes slush casting, not gravity die casting.
(b) Describes centrifugal casting, not gravity die casting.
(c) Describes pressure die casting with high injection pressures, unlike gravity feed.
(e) Describes a nonstandard method and not the accepted definition of permanent mould casting.

Common Pitfalls:
Confusing the term 'die' to mean only high-pressure die casting; believing all metal mould processes are identical; overlooking that gravity die casting solidifies fully inside the die without draining or rotation.

Final Answer:
None of the above.