高大、复杂、质量要求较高的铸件(如机床床身等),工艺设计时多采用阶梯式浇注系统(多为两层),以实现逐层浇注。但按生产上通用的封闭—开放式原则设计,虽可保证层浇,即先底层,后上层,但在上层内浇口进铁水时底层内浇口仍有大量金属液涌入。这样底层进入金属液过多,无法实现“上层浇注时,底 High, complex, high quality requirements of the casting (such as machine bed, etc.), process design more ladder-type casting system (mostly two), in order to achieve layer by layer casting. However, according to the common closed-open principle design in production, though the layer pouring can be guaranteed, the first bottom layer and the back upper layer can be ensured. However, there is still a large amount of molten metal poured into the bottom gate when the upper layer gate enters the hot metal. This bottom into the liquid metal too much, can not be achieved "when the upper pouring, the end