Avoiding the Cold Shut Defect by Introducing the Shape Factor Modifying Chvorinov’s Rule in Aluminum Gravity Die Casting

To avoid the so-called cold-shutCold shut defectDefects, the relationships among the proposed factors, such as shape factorShape factor, mold constantMold constant, and critical flow rate, were built up to construct the designing rules for the bottom ingate. An aluminumAluminum knuckle casting was cast in various initial mold temperaturesTemperature to obtain the critical filling flow rate controlled by the cross-sectional area of the bottom ingates with a constant velocity. Using the computational fluid dynamic package, the various magnifying sizes with the same shape as the knuckle castings were modeled, and the maximum critical filling time could be found. Based on the proposed shape factorShape factor modifying Chvorinov’s ruleChvorinov’s rule, the so-called critical mold constantMold constant (Bcold) and the shape factorShape factor (Spcold) were introduced in this study. From the proposed relationship, the rule of designing the critical bottom ingate size with the minimizing flow rate could be achieved to avoid cold-shutCold shut defectsDefects.