Research On The Mechanism Of Closed Extruding Fine-blanking Process And Conditions Of Obtaining Smooth Surface

Because the limit of traditional V-ring fine-blanking, low plastic and large thickness materials are hard to form with it. A new fine-blanking method, closed-extruding fine-blanking is brought up and it has been acquired as patent.A special mold structure is employed in this process. The punch and vice-die are relatively locked in a specific location and move downward together at first. The billets are limited by the extruding, as result, the plastic of the material in outer-ring zone is attenuated and it is almost impossible to deform along the radial again. Then the punch make a further downward movement, coupled with the counterpunch force, the material in deformation zone is in great three–dimensional compressive stress and the plasticity is improved, then low plastic and large thickness materials can stamping well at this time.At first, the major elements of hydrostatic stress in material are analyzed by using slab method. A special parameter, outer-ring fill rate, is proposed. That is derived the larger outer-ring fill rate the heavier hydrostatic stress. Grid method is employed to analyze the material flow lows in closed-extruding fine-blanking process.The closed-extruding fine blanking process was simulated with DEFORM-2D software. The character of the stress and strain and the flow of material is described. The heavy hydrostatic stress is obtained in material. And the influence of oute-ring fill rate and counterpunch force to the hydrostatic stress is studied, and the low derived upon is verified. In addition, the fracture criterion is applied to analyze the generating and expanding of crack. Compeering with experiments, the crack of the material in the process could be forecasted.According to the simulation above, an experiment tool and billets were designed and manufactured and plenty of parts were finished. The relationship between outer-ring fill rate and the proportion of the smooth surface, thickening is studied. The Conditions of Obtaining Smooth Surface is proposed. According to the stamping of material with different plasticity, the influence of plastic to the quality of smooth cutting surface is studied. The major design factor of the size of cavity in mold and the billets is proposed at last.The study shows that the closed-extruding fine blanking is an effective way to blank low-plastic and thick materials. The roughness of cut surface on the part is 0.03μm and the roughness of hole in outer-ring is 0.1μm . In addition, the collapse corner of the part is very small, and there has no burrs occurred. In the experiments, the largest thickness of part is 14.26mm .