To solve the casting shrinkage hole especially hot spot away from riser shrinkage

it is an effective way to design riser subsidies.However

the riser subsidies not only increases the metal liquid weight but also decrease mechanical properties.In addition

removal of riser subsidies can deteriorate casting surface quality and waste a lot of time as well as difficult to design riser subsidies on some parts.Through experiment

rockwool subsidies instead of riser subsidies for shell of nut exhibits acceptable effects

which decreased keyhole rejects from 100% to 4% and the shrinkage rate of waste from 28% to 0.