Patent ID: 7239736

Claim:
A method of welding a three-dimensional structure including a cylindrical portion, the method used when forming the three-dimensional structure by combining and connecting a plurality of members by welding along welding lines, the method comprising: determining in a first step, three-dimensional positions of welding points on at least one of said welding lines at a predetermined spacing on the basis of design data of said three-dimensional structure; determining an amount of deviation of position from the design data at the welding points from an image obtained by photographing the at least one welding line at the welding points by moving a light emitting section in a direction of x, y, and z axes and rotating work around its rotation axis so that the laser slit light irradiates the groove of the welding line when it crosses the welding line, and a CCD camera being positioned so that it receives the laser slight light from the direction slanting by a determined angle with regard to the emitting direction of the laser slight light; determining the amount of deviation of position from the design data in a vertical direction, gap width and amount of deviation from a designated seam line at the welding points from an image obtained from a CCD camera by light section method as a first deviation; and determining the amount of deviation of position from the design data in a horizontal direction by shading method from said obtained image, said obtained image being processed as a second deviation, a second step in which the teaching data corrected by said amount of deviation of position from the design data is obtained as modified teaching data; and a third step in which welding is performed along said at least one welding line in accordance with said modified teaching data.