Hardware mold blanking clearance on the quality of the stampings

The concept of blanking clearance blanking clearance: refers to the blade clearance between punch and die on the. Clearance on the quality of the cross section, 1) Normal: crack up and down, shining with big, flat Angle, burr, small taper, smooth; （ 2) Too: upper and lower crack don't overlap, tear break, section thick, with small, flat light, taper Angle; （ 3) Too small: upper and lower crack don't overlap, secondary shear, formed the second euphotic zone, burr. （ 4) Inequality: one side of the small gap appears small cross section quality characteristics, one side of the big gap in large clearance section quality characteristics. Gap's influence on the dimensional accuracy because of elastic deformation, the elastic recovery appears after the end of the blanking, size and the convex concave die cutting edge dimension size deviation, and the size of the elastic deformation and blanking clearance has a direct relationship. When punching blanking, ( 1) Gap enlargement: metal by the inward pull degree increase, elastic recovery make workpiece size increases, Hole size) , the tensile strength of the metal increases, elastic recovery workpiece size decreases, The workpiece size) ； （ 2) Smaller clearance: metal compression degree increase, pore size decreases, and the metal level of internal pressure increases, workpiece size increases. Hedge the impact of the cutting force blanking clearance clearance hedge the influence law of the cutting force is: the smaller the gap, the greater the compressive deformation zone components; The smaller tensile stress components, material deformation resistance increases, the greater the blanking force. On the other hand, the bigger the gap, the greater the composition of tensile stress in the deformation zone, deformation resistance is reduced, the cutting force is small. Clearance up to 5% ~ 20% of material thickness, the cutting force decline is not obvious. When single side clearance when Z increases to 15% ~ 20% of material thickness, unloading force is zero. Clearance of die life due to the workpiece and the influence of wall friction exists between convex and concave die, small gap, friction, die life is short. Blanking process, between the punch and punch, concave die and fall are friction between materials, and the gap is smaller, the more serious the friction. So, the gap is too small to die life is very bad, and the larger gap can make the side of the punch and die and the friction between material is reduced, and can slow the effect of non-uniform clearance, so as to improve the service life of mould. The determination of reasonable gap value selection of clearance, to attain better section quality blanking, high dimensional accuracy, less cutting force, high die life. Reasonable gap refers to a range of values, the maximum reasonable clearance, reasonable minimum clearance. Determination of clearance is to comprehensively consider the effect of the above factors, choose a proper clearance range as reasonable clearance. The upper limit for the biggest reasonable clearance, reasonable lower limit for the minimum clearance, namely reasonable gap refers to a range of values. In the specific design mould, according to the specific requirements on the workpiece and the production can be selected according to the following principles: ( l） When there is no strict with the quality of workpiece cross section, in order to improve the die life and reduce the cutting force, can choose a larger gap value; （ 2) When the workpiece cross section quality and manufacturing tolerance requirement is high, should choose a smaller gap value; （ 3) When calculating the blanking die cutting edge dimension, considering the mould wear in the use process will make the blade clearance increases, shall be calculated according to the minimum Z.