Abstract: A welding apparatus is provided which includes a rail member 5 installed along a side and a corner portion of a steel frame post, a pinion 46 mounted to a horizontally movable shifting member 50 such that even at the corner portion of the steel frame post 1 the pinion 46 is constantly held in mesh engagement with a rack 6 disposed on a side of the rail member 5, and a position holding roller 57 for guiding the shifting member 50 in a horizontal direction so that the distance between the rack 6 and the pinion 46 is kept constant. During the movement of the carriage, the distance between the rack and the pinion is kept constant to enable welding operations to be performed in succession with respect to side and corner portions of the steel frame post. Therefore, after a face-to-face welding operation at one side is completed, such a welding operation at the other side may be carried out without the necessity of removing the carriage from the rail member.

Abstract: An automatic welding apparatus including a robot which comprises a base, a rotary support rotatably mounted on the base, a pair of first arms pivotally movable together and rotatably supported each at its one end by the rotary support, a second arm rotatably supported by the other ends of the first arms at an intermediate portion close to its one end, and a hand connected to the other end of the second arm and rotatable about two axes intersecting each other at right angles. A core wire is supplied from a feeder to a welding torch attached to the hand of the robot. A control device controls movement of the robot, operation of the core wire feeder and power supply to the welding torch. When the forward end of the welding torch comes into contact with the work to be welded, with the core wire drawn into the torch, the resulting short-circuiting is detected to detect the position of the work.