Gating System in Metal Casting

Gating System

• Gating system controls the flow of molten metal from the ladle to the mold cavity.
• Elements that are connected with the gating system include pouring basin, sprue, sprue-base well, runner, runner extension, in-gate, and riser.
• Pouring basin prevents mold erosion and allows for smooth flow of metal into the sprue.
• Pouring basin prevents slag from entering the mold cavity using skimmers or skim cores.

Sprue

• Sprue is a channel that guides molten metal to the parting plane, then to the runners and gates, and ultimately the mold cavity.
• Sprue is designed to taper to ensure consistent flow of metal to the bottom

Sprue-base Well

• Sprue-base well reduces the momentum of molten metal by creating a reservoir at the bottom of the sprue.

Runner

• Runner carries molten metal from the sprue to the casting.

In-gate

• In-gate is the final stage where molten metal flows from the runner to the mold cavity.

Riser

• Riser serves as a reservoir of extra metal to compensate for shrinkage that occurs during solidification.
• Riser must solidify after the main casting to effectively compensate for shrinkage.

Riser Design

• Chvorinov’s rule can be used to estimate the size of a riser required to meet solidification time specifications.

Solidification of Metals

• During solidification, a series of events occur as the metal cools from molten to room temperature.
• These events significantly influence the size, shape, uniformity, and chemical composition of the grains, which ultimately affect the overall properties of the casting.