PRECISION FOUNDRY & INVESTMENT CASTING

Investment Casting Sprue, Runner & Ingate Hydraulics Vector Guide

Investment casting (lost-wax process) creates near-net-shape components in non-ferrous and ferrous alloys with fine surface finish ($\text{Ra} \le 3.2\,\mu\text{m}$). Designing the gating tree (sprue, runner, and ingates) is critical to ensure laminar metal flow without air entrapment, turbulence, or premature freeze-off porosity.

1. Choke Area ($A_c$) & Sprue Taper Design

To avoid air aspiration down the vertical sprue, the sprue must be parabolic or linearly tapered such that cross-sectional area decreases toward the bottom choke plane in accordance with Bernoulli's equation $A_1 \sqrt{h_1} = A_2 \sqrt{h_2}$.