Application of quality control to resistance welding

This paper describes a system of quality control of resistance welding that has been used successfully for the past few years in manufacturing switchgear cubicles and equipment. Standard samples of material identical with production parts are periodically inserted in the welding machine and welded without disturbing the settings and then tested to destruction in a torsion device. The diameter, torque, and angle of twist at failure all are measured and combined into a single figure indicative of weld quality. This number is plotted on control charts, and corrective action is taken whenever the control limits are exceeded. By setting these limits well within allowable values the quality of production parts is assured.