Friction stir conduction controller

A friction-stir welding apparatus for welding at least a portion of an elongated seam between juxtaposed workpieces, said apparatus comprising:

• a friction-stir pin tool;
• mounting, positioning and rotation means coupled to said pin tool, for holding said pin tool, for rotating said pin tool about an axis, and for controlling the position of said pin tool in the direction of said axis in response to a control signal:
• an anvil for supporting said juxtaposed workpieces with a portion of said seam on said axis;
• a seam anomaly sensing arrangement located adjacent said seam, for producing a first signal representing the magnitude of an electrical anomaly of at least that portion of said seam near said axis which is heated by said rotating pin tool;
• signal processing means coupled to said sensing arrangement and to said mounting, positioning and rotation means, for comparing said first signal with a standard signal representing the desired anomaly value of said seam, and for generating said control signal in response to the difference between said first and standard signals;
• and
• means for coupling said control signal from said signal processing means to said mounting, positioning and rotation means, for controlling the positioning of said pin tool so as to tend to maintain said desired anomaly value.