Welding machine and control method therefor

A control method for a welding machine, the control method comprising:

• defining a product as a master, which is taken as a reference among a plurality of products;
• defining another product among the plurality of products other than the master as a workpiece;
• acquiring a photographed master image by photographing, with a camera, a region including a master welding point and an edge on the master, the master welding point being a welding point set by a processing program for welding the master;
• receiving first coordinates of a position on the photographed master image, the first coordinates being indicated on a master constant surface by an operation unit, the master constant surface being a region of the master determined to lack a positional deviation with respect to the master welding point;
• extracting a master edge image of the master from the photographed master image;
• acquiring a master constant surface region of the master constant surface including the first coordinates;
• acquiring a master constant edge image based on the master edge image and the master constant surface region, the master constant edge image including a first edge image of the master constant surface region;
• acquiring a photographed workpiece image by photographing, with the camera, a region including a workpiece welding point and an edge on the workpiece, the workpiece welding point being set by the processing program for welding the workpiece together;
• extracting a workpiece edge image of the workpiece from the photographed workpiece image;
• acquiring a workpiece constant surface region including second coordinates of a position on the photographed workpiece image, the second coordinates being obtained based on the first coordinates;
• acquiring a workpiece constant edge image based on the workpiece edge image and the workpiece constant surface region, the workpiece constant edge image including a second edge image of the workpiece constant surface region;
• performing pattern-matching between the master constant edge image and the workpiece constant edge image so as to match the first edge image and the second edge image to acquire a first deviation amount between the master constant edge image and the workpiece constant edge image as a correction amount for the workpiece welding point;
• correcting the workpiece welding point by the correction amount to generate a corrected processing program for welding the workpiece;
• and
• controlling a welding robot to weld the workpiece based on the corrected processing program.