Friction stir welding device

A friction stir welding device comprising:

• a workpiece holder configured to hold a first workpiece and a second workpiece whose end edge is butted and disposed in a posture making an angle intersecting a face of the first workpiece;
• and
• a welding device main body configured to be relatively moved in directions in which corners formed by the first and second workpieces held by the workpiece holder extend,
• wherein the welding device main body includes:
• friction stir welding tools including stationary shoulders, which have workpiece contact faces brought into contact with both of the workpieces forming the corners, and rotatable probes and disposed at both the corners between which the second workpiece is sandwiched;
• spindle units configured to rotate the probes of the friction stir welding tools;
• axial movement units configured to move the spindle units in directions following rotary shafts of the probes within a plane perpendicular to a direction of relative movement of the welding device main body relative to the workpieces;
• and
• axially perpendicular movement units configured to move the spindle units in directions perpendicular to the rotary shafts of the probes within the plane perpendicular to the direction of relative movement, and
• wherein the axially perpendicular movement units include:
• movable tables that are moved in the directions perpendicular to the rotary shafts of the probes within the plane perpendicular to the direction of relative movement;
• and
• gravity compensation mechanisms that are mounted on the movable tables.