During the trial production of an integrated exhaust manifold aluminum cylinder head

a serious shrinkage defect was observed the threaded hole position of the inlet and exhaust side on the large end face of the timing side

and the rejection rate reached up to 26%. The solidification process of the casting was simulated by the AnyCasting software

and the origination of the defect was analyzed. The simulated results indicate that the hot spot is formed due to local thickness of the shrinkage

and then shrinkage cracking occurs during solidification

which leads to shrinkage defect.Therefore

some improvement measures were taken including the adding water-cooled inserts into the mold at the porosity position and setting up a riser

and absence of shrinkage defect was found in the continuous production of 30 cylinder heads.