Among the process parameters related to the casting geometry, the value of the machining allowance should refer to the maximum profile size and the corresponding size range of the machined castings. In sand casting, the machining allowance grade of castings is related to the molding method and casting materials, for example, the machining allowance grade of gray cast iron castings with machine molding is Epigg. In order to save the amount of metal and reduce the casting process, the casting holes and grooves in castings are usually formed by direct casting, but the holes and grooves with small size and complex structure can also be formed by machining.

However, for the casting pore diameter under the specific casting wall thickness, it is necessary to study the critical value considering the processability and economy. In addition, the selection of process parameters such as mold slope and reverse deformation are based on casting size, structure, wall thickness difference and material concession, combined with casting manual and related standards (JB/T 5105-1991).