Stamping mould blanking clearance impact on the quality of stamping parts!
source：未知 Writer： hmdmould Time：2021-04-20 09:17 Browse：
In the production process of stamping parts, the clearance between the punch edge and the mould edge is called blanking clearance. Through the mould cutting process, sheet section stress, deformation mechanism and forming condition analysis, to explore the influence of different gap hedge cutting cross section and the influence of the clearance of hedge cutting parts, and more specifically introduce mould cutting process and the abnormal situation, discusses how to choose appropriate blanking clearance and recoil cut exception handling.
Due to the existence of elastic deformation and the impact of clearance on dimensional accuracy, elastic recovery occurs after punching, making the size deviate from the edge size of punch and concave mould. Elastic deformation is directly related to the definition of blanking, when the gap changes, blanking, blanking, gap increases, metal inward stretching, elastic recovery to the size of the workpiece (aperture) increases, metal stretching increases, elastic recovery to the size of the workpiece (lower size); When the clearance is reduced, the metal pressure increases, the aperture decreases, the metal internal pressure increases, and the workpiece size increases. The effect of clearance on cutting force is that the smaller the clearance, the larger the compressive stress component in the deformation zone, the smaller the tensile stress component, and the greater the blanking force. On the contrary, the larger the clearance, the larger the tensile stress component, the lower the deformation resistance, the smaller the blanking force. When the clearance reaches 5%-20% of the thickness of the material, the blanking force does not decrease significantly. When the one-way clearance Z increases to 15%-20% of the material thickness, the unloading force is 0.3. The effect of the gap on the quality of the section: the upper and lower cracks coincide, the bright band is large, the collapse Angle, the burr and the taper are small, and the surface is smooth. Too large: the upper and lower cracks do not coincide, tear, rupture, the section is coarse, the bright band is small, the collapse Angle is large, the taper of the sharp point is large; Too small: the upper and lower cracks do not overlap, secondary shear occurs, the formation of secondary bright band and large burr; Non-uniformity: the mass cross section feature is small, the gap is small, the mass cross section feature is large. Because there is friction between the workpiece and the side wall of the punching mould, the clearance is small, the friction is large, and the mould life is short, which affects the life of the metal mould. There is friction between punch and punch and between mould and blanking valve in blanking process. The smaller the clearance, the more serious the friction. Therefore, too small clearance is not conducive to mould life, and large clearance can reduce the friction between the side of the mould and the mould material, so as to slow down the impact of uneven clearance, improve the life of the mould. Determination of reasonable clearance The selection of reasonable clearance should make the blanking parts achieve better section quality, higher dimensional accuracy, smaller blanking force and higher mould life. Reasonable clearance refers to a range value, maximum reasonable clearance and minimum reasonable clearance. The clearance is determined by comprehensively considering the influence of the above factors and selecting the appropriate clearance range as a reasonable clearance. The upper limit is the maximum reasonable clearance and the lower limit is the minimum reasonable clearance. The reasonable clearance refers to a range value. Mold design, according to the specific requirements of the workpiece and production, according to the following principles for selection: (1) in the case of not strict requirements on the quality of the workpiece section, in order to improve the life of the mold, reduce the blanking force, can choose a larger clearance value. (2) when the workpiece section quality and manufacturing tolerance is high, the smaller clearance value should be selected. (3) When calculating the cutting edge size of the punching mould, considering that the wear of the mould in the process of use will increase the cutting edge clearance, the cutting edge clearance should be calculated according to the Zmin value. Through the force form of the sheet material and the forming process of each area of the blanking section, it can be seen that the edge clearance is a very important parameter of the blanking mould.