METHOD AND APPARATUS FOR MEASURING ANGLE OF BEND, METHOD OF BENDING, AND APPARATUS FOR CONTROLLING ANGLE OF BEND

摘要

When an angle detecting head (29) provided with an emitter (113) and a pair of receivers (115, 117) is rocked, a bent surface of a workpiece bent by a punch (P) and a die (D) of a bending machine (1) is irradiated with a measurement light from the emitter, a reflected light is received by the pair of receivers, and a bending angle in a bent portion of the workpiece is obtained from a peak value of an amount of the light received by the respective receivers, the angle detecting head (29) is movable parallel to the die (X direction), horizontally movable in a direction (Y direction) close to or apart from the workpiece, and vertically movable in a direction in which the die is raised/lowered (Z direction), the angle detecting head (29) is positioned in an optimum angle measurement position of the workpiece and the bending angle is measured. Moreover, the bending machine (1) presses the workpiece W to the vicinity of a target angle, measures the bending angle of the workpiece during final pressing, removes pressure to bring the workpiece to an unloaded state, measures the bending angle of the workpiece, and obtains and registers an angle difference between the final pressing angle measured value and the unloaded angle measured value as a spring-back amount. Since the angle difference between the bending angle of the workpiece during the final pressing and the bending angle of the workpiece in the unloaded state is registered as the spring-back amount in this manner, the spring-back amount of the workpiece can accurately be measured, and further the measured spring-back amount can effectively be utilized.