JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III FABRICATION PROCESSES Previous Question Paper (November/December - 2020 - R16)

In casting, the runner is the primary channel that distributes molten metal from the sprue to the various gates or branches of the mold cavity. It acts as a transportation network within the gating system to ensure uniform flow.

The gate is the final, narrow entry point where the molten metal actually enters the mold cavity from the runner. It is typically designed with a smaller cross-sectional area than the runner to allow for easy removal of the casting after solidification and to control the flow rate and direction of the metal into the cavity.

Centrifugal casting is a process where molten metal is poured into a rotating mold, utilizing centrifugal force to distribute the metal against the mold walls. This results in a dense, high-quality casting with minimal impurities, as lighter inclusions are forced toward the center.

The process is categorized into three types:

• True Centrifugal Casting: The mold rotates about its own axis to produce cylindrical parts like pipes and tubes. No core is required for the inner diameter, as the centrifugal force shapes the inner surface.
• Semi-Centrifugal Casting: Used for parts with rotational symmetry like wheels or pulleys. The mold is rotated, but a core is typically used to define the internal shape.
• Centrifuging: Multiple mold cavities are placed at a distance from the axis of rotation. The molten metal is poured into a central sprue and forced into the cavities by centrifugal pressure.

Key advantages include superior mechanical properties, absence of risers, and high material utilization. The primary limitation is that it is restricted to rotationally symmetric parts or specific mold arrangements.