Method of adjusting the stroke of a press brake

A method of adjusting a stroke of a press brake having a movable beam supporting a punch, a fixed beam supporting a die, displacement means for displacing the movable beam with respect to the fixed beam, said displacement means resting on side frames immovably attached to the fixed beam, linear encoders for measuring a displacement of the movable beam with respect to the side frames, at least one sensor measuring a physical parameter (p) varying with the force exerted by said punch on a metal sheet placed on said die, and an electronic bending control device controlling the speed of the movable beam between top dead centre and bottom dead centre (BDC), said control device being provided with calculation means for correcting said bottom dead centre depending on a measurement of said displacement of the movable beam and a measurement of said physical parameter (p), wherein the difference in thickness between the actual thickness of the metal sheet and a reference value (e) of the thickness of the metal sheet is determined by said control device by comparing the actual position of said displacement of the movable beam at which there occurs a predetermined variation Δp of said physical parameter (p) with the theoretical position of said displacement of the movable beam where this variation Δp should occur if the thickness of the metal sheet would have the reference value (e), and wherein said bending control device calculates a correction of bottom dead centre by taking account of said difference in thickness, wherein a speed of the movable beam is reduced to a measurement acquisition speed (vam), less than a predetermined bending speed (v1), when the punch is at a predetermined distance from a theoretical pinching level of the metal sheet greater than a manufacturing thickness tolerance Δe of said sheet, and wherein the speed of the movable beam increases to said bending speed after detection of said predetermined variation Δp of said physical parameter (p).