Press brake

A method of controlling a press brake, the press brake including:

• a die;
• a punch that is arranged so as to be opposed to the die and moves in an upper-lower direction relative to the die to press a front surface of the workpiece;
• a crowning structure that has an upper piece and a lower piece that interlock together, the upper piece and the lower piece span across the die in a die longitudinal direction, and the crowning structure changes a crowning amount that is an amount of upward projection of a middle portion of the die relative to both end portions of the die in the die longitudinal direction;
• and
• a conveyor to convey the workpiece in a longitudinal conveying direction, wherein the longitudinal conveying direction and the die longitudinal direction of the die are within a horizontal plane and are orthogonal to each other,
• the method comprising:
• pressing the workpiece by the punch to perform bending;
• conveying, by the conveyor, the pressed workpiece;
• acquiring a middle bending amount and end bending amounts, the middle bending amount being a bending amount of a width direction middle portion of the pressed workpiece pressed by the punch, the end bending amounts being bending amounts of width direction end portions of the pressed workpiece pressed by the punch;
• correcting the crowning amount in accordance with a difference between a shortage of the middle bending amount from a target bending amount and a shortage of each end bending amount from a target bending amount;
• and
• conveying, by the conveyor, the workpiece to a bending position, driving the crowning structure based on the corrected crowning amount, and
• pressing the workpiece by the punch to perform the bending again.

A method of controlling a press brake, the press brake including:

• a die;
• a punch that is arranged so as to be opposed to the die and moves in an upper-lower direction relative to the die to press a front surface of the workpiece;
• a crowning structure that has an upper piece and a lower piece that interlock together, the upper piece and the lower piece span across the die in a die longitudinal direction, and the crowning structure changes a crowning amount that is an amount of upward projection of a middle portion of the die relative to both end portions of the die in the die longitudinal direction;
• and
• a conveyor to convey the workpiece in a longitudinal conveying direction, wherein the longitudinal conveying direction and the die longitudinal direction of the die are within a horizontal plane and are orthogonal to each other,
• the method comprising:
• pressing the workpiece by the punch to perform bending;
• conveying, by the conveyor, the pressed workpiece;
• acquiring a middle bending amount and end bending amounts, the middle bending amount being a bending amount of a width direction middle portion of the pressed workpiece pressed by the punch, the end bending amounts being bending amounts of width direction end portions of the pressed workpiece pressed by the punch;
• correcting the crowning amount in accordance with a difference between a shortage of the middle bending amount from a target bending amount and a shortage of each end bending amount from a target bending amount;
• conveying, by the conveyor, the workpiece to a bending position, driving the crowning structure based on the corrected crowning amount, and pressing the workpiece by the punch to perform the bending again;
• and
• in a first bending by the die and the punch, setting an initial value of a stroke amount of the punch to a value smaller than such a value that it is expected that the target bending amount can be realized.