Reducing the R fillet on the bottom corner of the punch can reduce the amount of bending springback. You can also reduce the gap between the bending punch and the die, so that the gap value on both sides is less than two material thicknesses, so that the bending has some stretching effect, which can also reduce the amount of springback. At this time, the punch does not need to be 87° and can be made into 90°.