Work positioning device

A workpiece positioning device, for a bending machine, which positions a workpiece at a predetermined position by image processing, comprising:

• an imager that photographs an entire image of only one corner of the workpiece supported by a gripper of a robot;
• a workpiece image detector that obtains an entire detected corner image based on the entire image of only one corner of the workpiece which is photographed by the imager;
• a workpiece reference image calculator that calculates an entire reference corner image based on pre-input information;
• a difference amount calculator that compares the entire detected corner image and the entire reference corner image, and that calculates an amount of difference between the entire detected corner image and the entire reference corner image in an angular direction and in X and Y axial directions;
• and
• a robot controller that controls, based on the amount of calculated difference, a robot such that the entire detected corner image and the entire reference corner image coincide at once with each other, in order to position the workpiece at the predetermined position.