Question

Problem 2 (a): A mold has a downsprue of length = 6.0 in. The cross-sectional area at the bottom of the sprue is 0.5 in? The sprue leads into a horizontal runner that feeds the mold cavity, whose volume = 75 in'. Determine (a) the velocity of the molten metal flowing through the base of the downsprue, (b) the volume rate of flow and (c) the time required to fill the mold cavity.

Answer 1

Considering the casting system as given below.

6.0 in 0.5 in2 75 in 3

a)

Height of sprue h_t = 0.6 in = 0.6 X 0.0254m = 0.01524m

Velocity of the molten metal at the base of the sprue V=
/2gh
t = $\sqrt{2X9.81X0.01524}$ = 0.547 m/s

b)

Volume rate of flow at the base of the sprue = Area X Velocity

Area A = 0.5 in² = 0.5 X 0.0254 X 0.0254 = 0.0003226 m².

Volume flow rate = 0.0003226 X 0.547 m³/s = 0.000176 m³/s

c)

TIme required to fill the cavity = Volume of the cavity / Volume flow rate at the base of the sprue

Time, t = 75 X 0.0254³ m³ / 0.000176 m³/s = 6.965 s