In-Line Inspection of Resistance Spot Welds for Sheet Metal Assembly Chrysler’s Windsor Assembly Plant tries out an ultrasonic real-time monitoring system to track expulsion, electrode life, and weld problems Using a built-in ultrasonic sensor provides a new approach in quality inspection of resistance spot welds. With real-time quality monitoring, every weld can be instantaneously inspected as it is made. By knowing the quality of each weld joint, the welding control system user has the advantage of correcting problems before producing unacceptable products. It also becomes possible to collect data and infer information regarding the process stability that has been unavailable before. As a stand-alone unit or in tandem with adaptive control welding systems, the realtime ultrasonic inspection technology permits quality measurements, instead of just quality forecasting. The dynamics of spot weld size, instantaneous quality changes, electrode cap degradation, and other otherwise difficult-to-determine parameters become readily available to weld control engineers. This article presents a case study of an installation at Chrysler’s Windsor Assembly Plant where real-time monitoring is used to track weld quality, expulsion events, electrode life, and detect problems. With ever-increasing production volumes and new metals being introduced every year, 58 JANUARY 2014 the use of a nondestructive automatic inspection system is necessary for the sheet assembly industry to stay competitive and provide quality products at a low cost. Real-Time Inspection Technology Resistance spot welding is currently a dominant joining technology in the sheet metal assembly industry, especially in automotive manufacturing. A recent automotive roadmap suggests that this trend is not likely to change any time soon (Ref. 1). The average car contains 3 to 4 thousand spot welds, which ensure its structural integrity. For decades, the main quality assurance method in production was destructive testing: peel test, chisel test, and metallographic analysis. These methods are quite costly and time consuming. Beside, destructive testing is only a periodic procedure that selectively inspects a small random portion of the sample pool. Different nondestructive inspection techniques BY R. Gr. MAEV, A. M. CHERTOV, W. PEREZ REGALADO, A. KARLOFF, A. TCHIPILKO, P. LICHAA, D. CLEMENT, AND T. PHAN have been introduced to speed up the process and increase the percentage of validated welds. Today, nondestructive inspection of resistance spot weld quality is a subject of high interest in automotive and other sheet metal assembly industries. Still, with new inspection technologies, only a small fraction of resistance spot welds get tested. The procedure remains quite time consuming as parts must be removed from the production line, or production needs to be suspended for inspection. For this reason, many efforts have been made to develop a real-time spot weld quality assurance system. Most of the existing systems employ some kind of Fig. 1 — Schematic setup of ultrasonic in-process spot weld analyzer. R. Gr. MAEV, A. M. CHERTOV, W. PEREZ REGALADO, and A. KARLOFF are with Institute for Diagnostic Imaging Research, University of Windsor, Windsor, Ont., Canada. A. TCHIPILKO is with Tessonics, Inc., Windsor, Ont., Canada. P. LICHAA, D. CLEMENT, and T. PHAN are with Chrysler Windsor Assembly Plant, Windsor, Ont., Canada. This article is based on a paper presented at the Sheet Metal Welding Conference XV, Livonia, Mich., Oct. 2–5, 2012.
Welding Journal | January 2014
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