Ductile iron of what kind of measures to address process and prevent Shrinkage , the current consensus is , the mold must have sufficient rigidity and strength , chemical composition close to the eutectic composition, and strengthening of the ball to generate sufficient inoculation Graphitized expansion. But there is controversy on design principles specific processes : equilibrium solidification theory that graphitization expansion of ductile iron can be offset solidification shrinkage , measures should be taken on the process , the contraction and expansion unit time, contraction and feeding were proportionally , by the expansion and Dynamic shrinkage is superimposed to achieve the purpose of feeding the casting. The concept of using the riser is limited feeding . The riser does not have to be solidified later than the casting  . The role of cold iron is to balance the difference in wall thickness of the casting , eliminate hot joints , and can To advance part of the graphitization ; but there are also documents  that object to this , thinking that the shrinkage of ductile iron is greater than the expansion , there must be external feeding , and the riser cannot be solidified later than the casting . The function of cold iron is to first shrink the molten iron. advance and accelerate , more conducive to timely feeding earlier .