1998 年 16 巻 2 号 p. 282-289
The fundamental requirements for torch construction have been clarified as in the following, which are to provide the specified curvature for a wire and are able to control its rotation at the same time for the sake of improving the accuracy to aim at target position in a weld joint. In order to provide a set curvature for the wire of 1.2 mm diameter, it is necessary to provide both radius of curvature of 90 mm or less and curve with the bend angle of 75° or larger for the torch. In case that the wrist (namely secondary axes) of a robot is twisted, it is difficult to restrict the rotation of the wire inside the torch only by selecting both simple curvature and bend angle for the curved torch. The rotation of wire tip can be restricted by providing a wire path with two curves having their centers of curvature in opposite positions each other. By using the wire reforming type torch such as the above, even in case that the bend direction of curvature of the wire supplied changes and/or a twisted wire is fed, the deflection of the wire tip from the datum of the torch can extensively be restricted and controlled to aim at the target position in joints. Furthermore, even if the wire conduit connected to the torch vibrates, the deflection of wire tip position is within about 0.1 mm and the stability of both welding current and voltage can be maintained until the end of life of a contact tube.