Identifying operating conditions from pre-weld information for resistance spot welding

Resistance spot welding is one of the dominant sheet metal joining processes in the automobile, aerospace and appliance industries. This process has been around since the turn of the century, but the factors affecting process quality are not well understood. The data presented in the paper shows that set-up conditions such as electrode condition, electrode alignment and part fitup are critical for selection of the appropriate weld schedule. The data further show that these conditions are reflected in the nature of the force and displacement signals that are measured when the electrodes are brought in contact with the work pieces. Several algorithms are discussed that can identify the presence or absence of four set-up faults: angular misalignment; fitup faults; axial misalignment; and edge welds. Further, there is some indication that these signals may provide dynamic information about electrode wear. The paper concludes with some discussion of the work needed to extend these results from the binary fault conditions presented, to the case of faults that can lie across a continuum.