There are two main classification methods of gating system: one is divided into closed type, semi closed type and open type according to the different proportion of sprue cross-sectional area of each part (or the different position of choke section). The automobile hub support belongs to small class a nodular cast iron, with a single weight of about 6.9 kg. In order to ensure the slag retaining effect and make the metal liquid filling more stable, the nodular cast iron adopts the transverse sprue with the largest cross-sectional area and the flow blocking section is located in the inner sprue. During the, the system is filled with a slow semi closed gating system. According to the actual production experience of the factory, It is determined that the section ratio of gating system is a straight: a transverse: a inner = 1.7:2.2:1.
Another classification of gating system is divided into top injection type, middle injection type, bottom injection type and layered injection type according to the different distribution positions of ingate in nodular cast iron. According to the characteristics of complex shape and uneven wall thickness of nodular cast iron, the injection mode of medium injection slow flow is selected, that is, the inner sprue is set in the middle of nodular cast iron to make the liquid metal rush into the cavity from the parting surface. At the same time, a two-stage inner sprue is set on the upper part of the parting surface, and a dark riser is set between the nodular cast iron and the inner sprue to increase the flow resistance of liquid metal, make the mold filling more stable and improve the feeding capacity of the riser.