Bending method

Abstract

A bending method includes a series of processes of repeating bending of a workpiece by applying pressure to the workpiece with upper and lower tools attached to upper and lower tables of a press brake from a first process to an N-th process while feeding the workpiece at a predetermined pitch. The series of processes includes: measuring a bending angle of the workpiece at completion of an M-th process; and correcting a table output for applying pressure to the workpiece based on a measurement value of the bending angle of the workpiece as measured and a target value of the bending angle of the workpiece at completion of the M-th process. In a case where the table output is corrected, the bending is restarted from a previous process which is the M-th process or a process before the M-th process based on the corrected table output.

1 . A bending method comprising a series of processes of repeating bending of a workpiece by applying pressure to the workpiece with an upper tool attached to an upper table and a lower tool attached to a lower table of a press brake from a first process to an N-th process (where N is a natural number) while feeding the workpiece at a predetermined pitch so as to bend the workpiece at N processing positions, thereby bending the workpiece at a desired bending angle,
 the series of processes comprising:   a measuring process of measuring a bending angle of the workpiece at completion of an M-th process (where M is a natural number less than N); and   a calculation process of correcting a table output for applying pressure to the workpiece based on a measurement value of the bending angle of the workpiece measured in the measuring process and a target value of the bending angle of the workpiece at completion of the M-th process,   wherein, in a case where the table output is corrected, the bending is restarted from a previous process which is the M-th process or a process before the M-th process based on the corrected table output.   
     
     
         2 . The bending method according to  claim 1 , wherein the M-th process is a process among the first to the N-th processes in which the bending angle of the workpiece is within a predetermined angle range at completion of the process. 
     
     
         3 . The bending method according to  claim 2 , wherein the angle range is 165 degrees or more and 175 degrees or less. 
     
     
         4 . The bending method according to  claim 1 , wherein the calculation process comprises:
 calculating an accumulated error for the bending continued up to the N-th process based on an error between the measurement value of the bending angle of the workpiece and the target value of the bending angle of the workpiece at completion of the M-th process; and   correcting the table output so as to cancel out the accumulated error.   
     
     
         5 . The bending method according to  claim 1 , wherein,
 in a case where the bending angle of the workpiece is measured at one point between left and right ends of the workpiece in the measuring process, the calculating process comprises regarding the measurement value of the bending angle of the workpiece at the one point as the bending angle of the workpiece as a whole and uniformly correcting the table output between the left and right ends of the workpiece; and   in a case where the bending angle of the workpiece is measured at a plurality of points between the left and right ends of the workpiece in the measuring process, the calculation process comprises correcting the table output based on the measurement value of the bending angle of the workpiece at the plurality of points so that the bending angle between the left and right ends of the workpiece becomes uniform.