Pan E N, Sheu G L

Abstract: The mold-filling behavior of lost foam A356 alloy in a two-layer vertical gating system has been explored in this study. Influences of gating system parameters, including sprue height, sprue area and ingate area, and the pouring temperature, on the filling characteristics of this specific gating system were evaluated. The experimental results indicate that the melt tend to flow into the upper pattern layer first. The extent to which the melt fills the upper pattern layer in advance of the lower pattern layer is governed mainly by the resistance to the melt upon filling the lower portion of the gating system. As a result, a longer lower sprue and/or a bigger sprue cross-section promote the filling of the upper pattern layer. A higher pouring temperature has been found to promote the filling of the upper pattern layer. A regression equation was derived to correlate the amount of melt flowing into the upper pattern layer ahead of the lower pattern layer with the related gating and processing parameters. The filling modes of both the upper and lower pattern layers interact with one another, which can be clearly demonstrated by the detailed variations in the sectional mold filling velocities in both pattern layers. The phenomenon of an interruption in the heating stage of the temperature response curves takes place in the last-to-fill regions or, in some cases, near the ingate. Those regions tend to exhibit relatively low flow velocities.

Keywords: Aluminum alloy, Behavior, Lost foam, Mold filling, Vertical gating.