We are all aware that welded surfaces on high pressure casting die inserts prematurely heat check. Heat check is not something that we want on machining datum surfaces. In the pictured transfer case casting the part rests on three ears in the machining fixture. I have colored the datum surface on one ear red. The dimensional accuracy of this surface will determine whether sufficient machining stock is provided on the rest of the casting.

One of the most effective methods of reducing exposed porosity is to reduce machining stock thickness. This is because the skin of a high pressure aluminum die casting is porosity free due to rapid solidification. As we reduce the provided stock thickness shrinkage and warp of the casting becomes a factor in reliably achieving machining clean up

Skilled die cast shops have discovered that a more accurate casting shape can be achieved if the die shape is biased to correct for warp. This is accomplished by adjusting the die shape using a first sample casting. Certain area on the mold are initially created with ..25 mm extra mold steel. This is where we get the term “steel safe” The pictured datum surface is a prime example. It is unacceptable to bias a mold shape to compensate for warp by welding datum surfaces. Adding extra steel makes weld free correction possible.