Abstract: An actual plate thickness and actual material constants are measured during punching before bending. The measured information is reflected on the bending, so that the bending is performed efficiently and accurately. Punching is carried out for each blank developed based on a nominal plate thickness and nominal material constants in blanking before the bending of a work W. Then, an actual plate thickness distribution and an actual material constant distribution of the work W are calculated based on various data containing a ram stroke and a pressure detected in the punching.

Abstract: In bending a workpiece, a position of the workpiece relatively pressed down by a punch is directly detected by a plurality of position detectors provided in a V-groove of a die, and a bending speed calculation section obtains a bending speed from a change in this position. If bending speeds at position of the respective position detectors differ, a uniform speed arithmetic operation section calculates a bending speed to make the bending speeds at the positions of all of the position detectors, and a driving shaft instruction section controls driving shafts to bend the workpiece at the uniform bending speed.

Abstract: A bending method includes determining a provisional bending stroke value that resulted in a predetermined angle during test bending. The bending method also includes calculating a stroke value correction amount for correcting the provisional bending stroke value, based on the number of times a test piece was contacted to obtain the predetermined angle during test bending. The stroke value correction amount is added to the provisional stroke value to obtain a corrected stroke value, so as to obtain the predetermined angle during operational bending using the corrected stroke value.

Abstract: A bending apparatus for bending a workpiece W according to cooperation of a punch P and a die D previously carries out various step bending or makes simulation of step bending, and calculates an approximation formula based on a correlation between a ratio % of a one-sided elongation value &agr; to a plate thickness t and a step bending angle &thgr; based on a relationship among the plate thickness t, the step bending angle &thgr; and the one-sided elongation value &agr; of the workpiece W so as to store the formula as a database. The more accurate one-sided elongation value &agr; of the step bending is calculated by small parameters including only two data including the plate thickness t and the step bending angle &thgr; previously input at the time of actual bending based on the approximation formula in the data base so that the bending is carried out easily.

Abstract: A plate thickness detector for a bending machine causes a punch to make a relative stroke and bend a workpiece mounted on an upper surface of a die cooperatively by the punch and the die. A displacement gauge is provided in the die, is always urged upward from a V-groove of the die, and measures a distance from the upper surface of the die to a lower surface of the workpiece. A ram position detector detects a relative stroke quantity of the punch to the die. The punch is caused to bend the workpiece from a position away from the die by a reference inter-blade distance.

Abstract: A bending apparatus for bending a workpiece W according to cooperation of a punch P and a die D previously carries out various step bending or makes simulation of step bending, and calculates an approximation formula based on a correlation between a ratio % of a one-sided elongation value &agr; to a plate thickness t and a step bending angle &thgr; based on a relationship among the plate thickness t, the step bending angle &thgr; and the one-sided elongation value &agr; of the workpiece W so as to store the formula as a database. The more accurate one-sided elongation value &agr; of the step bending is calculated by small parameters including only two data including the plate thickness t and the step bending angle &thgr; previously input at the time of actual bending based on the approximation formula in the data base so that the bending is carried out easily.

Abstract: An actual plate thickness and actual material constants are measured during punching before bending. The measured information is reflected on the bending, so that the bending is performed efficiently and accurately. Punching is carried out for each blank developed based on a nominal plate thickness and nominal material constants in blanking before the bending of a work W. Then, an actual plate thickness distribution and an actual material constant distribution of the work W are calculated based on various data containing a ram stroke and a pressure detected in the punching.

Abstract: At a time of executing a bending process of a work according to a cooperation between a punch and a die, a provisional stroke value for obtaining a predetermined angle is determined on the basis of a bending process condition. A test bending process is executed on the basis of the provisional stroke value, and a striking number required for striking the work until the predetermined angle is obtained is judged. Since a stroke value correction amount at a time of a main bending corresponding to the striking number and the predetermined angle is previously determined, a main bending process is executed by correcting to a stroke value at a time of the main bending by computing the corresponding stroke value correction amount on the basis of the stroke value correction amount at a time of the main bending process.

Abstract: In bending a workpiece (W), a position of the workpiece W relatively pressed down by a punch (P) is directly detected by a plurality of position detection means (RDC1, RDC2 and RDC3) provided in a V-groove (11) of a die, and a bending speed calculation section obtains a bending speed from a change in this position. If bending speeds at position of the respective position detection means differ, a uniform speed arithmetic operation section calculates a bending speed to make the bending speeds at the positions of all of the position detection means uniform, and a driving shaft instruction section controls driving shafts (7L, 7R) to bend the workpiece at the uniform bending speed.

Abstract: In a plate thickness detector for a bending machine causing a punch to make a relative stroke and bending a workpiece mounted on an upper surface of a die cooperatively by the punch and the die, a displacement gauge (17) is provided in the die, is always urged upward from a V-groove of the die, and measures a distance from the upper surface of the die to a lower surface of the workpiece, and ram position detection means (11) detects a relative stroke quantity of the punch to the die. The punch is caused to bend the workpiece from a position away from the die by a reference inter-blade distance.