Aiming at gas-entrapment

shrinkage porosity（holes）and cold shut easily occurred in the cylindrical structure of gearbox housing in the process of filling

a design that changing craft structure of the gearbox housing was presented

and two optimized designs were presented.Through improving the design of the gate

decreasing the wall-thickness of some parts and adding overflow slot

the optimal process was obtained by FEM.The castings with defects-free and qualified quality were produced by practical-trial production.