In bottom pressing, or bottoming, the punch presses the workpiece in opposition to The underside area of a V or U-formed die, which defines the final bend angle. This technique provides precise bends and reduces the tendency for springback in the workpiece due to the appliance of greater bending power. https://jaiden1hg45.wikijm.com/1118921/the_smart_trick_of_hot_iron_stamping_that_nobody_is_discussing