Die design for deep drawing with high-pressured water jet utilizing computer fluid dynamics based on Reynolds' equation

This paper proposes a new die design for deep drawing with high-pressured water jet. The authors had previously proposed a deep drawing method with high-pressured water jet. The water jet enables deep drawing without oil or other chemical lubricants, which might require some additional processes for lubricant removal and become a nuisance in the environment. One of the problems in the method using a prototype die with 8 nozzles in the hoop direction had been that the pump pressure had to be boosted significantly high for successful deep drawing, leading to scars on the surface of the deep drawn product. In the present paper, two new concepts of design were introduced with the help of computational fluid dynamics (CFD) for water film considering the blank deformation obtained by the finite element method (FEM). The first concept is that the number of nozzles should be increased from 8 to 16, and that the position of the added 8 nozzles should be positioned on the flange part of the die as a result of the CFD. The second concept is to shallowly engrave a looped ditch linking the nozzles. The CFD showed that while the die without the looped ditch generated an area of reduced pressure between the nozzles, the ditch-engraved die maintained the pressure, resulting in satisfactorily strong uplift force on the blank even at relatively low pump pressure. A series of experiments also verified the numerical results, and proved the excellence of the ditch-engraved die.