Bend correction apparatus and method

A method of determining the correct bend angle when forming a workpiece subject to springback, the method comprising:

• bending the workpiece with bending means comprising pressure die means for holding a workpiece, radius die means for providing a radius form about which the workpiece is bent, the radius die means being adapted to rotate about an axis for bending the workpiece about the radius die means to a predetermined angle, and workpiece clamping die means for engaging and bending the workpiece relative to the pressure die means and about a portion of the radius die means;
• controlling said bending means by control means for moving the clamping die means between a bend angle position in which the workpiece is bent about the radius die means to said predetermined angle relative to the clamping means and a relieved position in which the clamping die means is not bending the workpiece;
• and
• sensing the free portion of the workpiece by sensor means, said sensor means movable conjointly with the radius die means for engaging the workpiece in a springback position upon rotation of the radius die means toward the workpiece when said clamping die means is in its relieved position and for sending a signal to the control means upon contact with the workpiece, said sensor being stationary relative to the radius die means as the radius die means rotates, said control means then determining a rebend angle to achieve the desired degree of bend in the workpiece and moving said clamping die means to its bend angle position and rotating the radius die means to the rebend angle to bend the workpiece to that angle and storing the rebend angle for bending subsequent workpieces.

A workpiece bending apparatus for automatically bending a workpiece having springback characteristics to a desired angle, comprising:

• a pressure die means for holding a workpiece,
• a radius die means for providing a radius form about which the workpiece is bent, the radius die means being adapted to rotate about an axis for bending the workpiece about the radius die means to a predetermined angle,
• a workpiece clamping die means for engaging and bending the workpiece relative to the pressure die means and about a portion of the radius die means,
• control means for moving the clamping die means between a bend angle position in which the workpiece is bent about the radius die means to said predetermined angle relative to the clamping means and a relieved position in which the clamping die means is not bending the workpiece, and
• sensor means movable conjointly with the radius die means, said sensor means normally engaging the workpiece in a springback position after a bend is made in the workpiece and the clamping die means moves to its relieved position and rotates away from the workpiece upon rotation of the radius die means away from the workpiece and sends a signal to the control means upon disengaging the workpiece, said sensor being stationary relative to the radius die means as the radius die means rotates, said control means then determining a rebend angle to achieve the desired degree of bend in the workpiece and moving said clamping die means to its bend angle position and rotates the radius die means to the rebend angle to bend the workpiece to that angle and storing the rebend angle for bending subsequent workpieces.