Abstract: An optical light beam device for automatically controlling the bending operation when bending with a press brake, comprising an emitter (1), mounted on one side of the press, adapted to produce a large-diameter light beam (8), directed parallel to the bending axis of the workpiece to be bent, and a receiver (4) comprising a box (11) including a screen (14) drilled with a plurality of holes (15) arranged to forming a plurality of light beams (16) of small diameters. The box (11) comprises a deflecting means (17) intended to deflecting the light beams (16) on to a system of photodiodes (18) arranged on the axis of rotation (19) of a rotating motor (12) fast with the box (11) and with an angle coder (13). A microordinator is connected to the photodiodes (18) and to the angle coder (13) and permits the determination of the instantaneous bending angle of the workpiece and the control of the descent of the punch.

Abstract: The device employs a number of detectors (1) mounted at the level of the upper surface of the die (2) and a numerical control system (5). The purpose of the detectors is to signal to the numerical control the moment that the part b of the sheet begins to rise. The device allows the automatic determination of the thickness of the sheet in the area where the bend is to be located, during the course of the forming operation. The thickness of the sheet is then used by a numerical control system to correct the travel of the tool, without interrupting the forming cycle, in such a way as to obtain with high precision the required bend angle.