Cracks in dense stamped parts occur more often when the […]
Cracks in dense stamped parts occur more often when the bending radius and bending angle are too strict. For products with a small bending width, the crack is at both ends of the width; when the bending width is large, the crack occurs along the bending line near the middle of the bending width. In addition, the bending line tends to crack at right angles.
Solution to cracks in precision stamped and bent parts:
1. Measures to be taken when cracks occur along the bending line.
(1) When the radius of curvature is constant, the thicker the sheet material or the longer the bending width, the more likely cracks are generated. When a SPCC type steel plate is used, if R/t < 0.5, cracks are generated. Therefore, R/t is designed to be 0.5 or more, and the occurrence of cracks can be avoided.
(2) Make the bending line at right angles to the fiber direction. However, the calendering material differs in the fiber direction and the vertical direction due to the bending limit. When approaching the limit bending process, the relationship between the bending line and the fiber direction when the sheet is unloaded must be considered.
(3) The side with the burr is placed on the inside of the bend.
(4) Remove burrs.
(5) Only the burr portion of the curved line is annealed.
(6) The shear section on the side of the burr is first compressed to a 45 degree angle and then bent.
(7) When the bending limit of the thick plate is exceeded and it is bent to a small R, an additional back pressure method is employed. The method is in a free bending die, and the lower die uses a strong top plate, which can increase the compressive stress on the deformed portion of the plate during the bending process, thereby making the bending radius significantly reduced and preventing the occurrence of cracks. After the V-bend is completed, the outside of the bending radius of the product forms a platform which is caused by the back pressure of the top material.