Question

In a gating system, the ratio of 1:2:4 represents:

• A. Sprue Base Area: Runner Area: Ingate Area
• B. Pouring Basin Area: Ingate Area: Runner Area
• C. Sprue Base Area: Ingate Area: Casting Area
• D. Runner Area: Ingate Area: Casting Area

Hint:

Remember that non-pressurized gating systems typically have increasing areas along the flow path (Sprue Base<Runner<Ingate), while pressurized systems have decreasing areas (Sprue Base>Runner>Ingate).

Answer 1

The Correct Option is A

Step 1: Understand the components of a gating system in casting.
A gating system is a network of channels that delivers molten metal from the pouring basin to the mold cavity. The typical components in sequence are:
Pouring Basin: A reservoir at the top to receive molten metal.
Sprue: A vertical channel through which molten metal flows downwards. It has a tapered shape, with the larger end at the top (receiving molten metal from the pouring basin) and the smaller end at the bottom (sprue base).
Sprue Base: The bottom end of the sprue where the molten metal exits. Runner: Horizontal channels connected to the sprue base that distribute the molten metal to different parts of the mold cavity.
Ingates: Small channels that connect the runner to the mold cavity, through which the molten metal enters the cavity.
Step 2: Understand the concept of area ratios in gating systems.
Area ratios in gating systems are designed to control the flow rate and pressure of the molten metal as it moves through the system to ensure proper filling of the mold cavity without turbulence, aspiration, or other defects. Common gating system designs include pressurized, non-pressurized, and mixed gating systems, each with different area relationships between the sprue base, runner, and ingates. Step 3: Analyze the given ratio 1:2:4.
The ratio 1:2:4 implies that the area increases progressively from the first component to the last component in the sequence represented. Step 4: Consider the typical area progression in a non-pressurized gating system.
In a non-pressurized gating system (also known as an open gating system), the total area of the ingates is usually larger than the area of the runner, which in turn is larger than the area at the base of the sprue. This design aims to maintain a positive pressure throughout the gating system, minimizing aspiration (drawing in of air or gases). A typical area ratio for a non-pressurized system is Sprue Base Area : Runner Area : Total Ingate Area = 1 : (1.5 to 2.5) : (2 to 4). The given ratio 1:2:4 fits this pattern. Step 5: Consider the area progression in a pressurized gating system.
In a pressurized gating system, the total area of the ingates is smaller than the area of the runner, which is smaller than the area at the base of the sprue. This design ensures that the gating system is always full of molten metal, leading to higher metal velocity in the ingates and promoting directional solidification. A typical area ratio for a pressurized system is Sprue Base Area : Runner Area : Total Ingate Area = 3 : 2 : 1 or similar. The given ratio 1:2:4 does not fit this pattern. Step 6: Evaluate the options based on the typical area ratios.
The ratio 1:2:4, with progressively increasing area, corresponds to a non-pressurized gating system where the sequence is Sprue Base Area : Runner Area : Ingate Area. Step 7: Select the correct answer.
The ratio of 1:2:4 in a gating system represents Sprue Base Area : Runner Area : Ingate Area.