Resistance spot welding processing monitoring based on electrode displacement curve using moving range chart

Abstract

Electrode displacement curve is an ideal monitoring parameter which can directly reflect spot weld nugget formation in resistance spot welding (RSW) process. The current RSW quality monitoring systems based on electrode displacement curve mainly focus on the low frequency information of the curve, such as the curve’s shape. Variation of the curve that represents process consistency is little studied. Based on on-line measured electrode displacement curve, statistical process control method is introduced to analyze the process consistency by employing moving range (MR) chart. The moving range method implemented the RSW process monitoring through providing the high frequency information of the curve. The results of this research will enhance the understanding of the electrode displacement curve, and help systematically design better on-line RSW quality monitoring systems. A case study demonstrates the validity and effectiveness of the methodology.