Gm Global Technolgoy Operations, Inc.

Gregory L Nagel

Dixon Cleveland

James R Havens

Basil A Decina, Jr

Alfred L Kresse, Jr

Albert F Houchens

Anthony Lee

David M Sidlosky

Balarama Vempaty Murty

William C Jenuwine

Dale K Watney

Warren D Hill

Two sheet metal panels are joined together to form a closed box section structure. The two panels are individually stamped from a blank and each has a flange along one edge and a toothed edge of alternating notches and tabs along the opposite edge. The two panels are assembled in box section forming relationship with the flanges of the two panels abutting with one another and the toothed edges abutting with one another with the tabs of the one panel interdigitating with the tabs of the other panel. Clamps are applied to the panels and urge the interdigitating tabs into tight fitting relationship. Then the panels are welded together at the interdigitating tabs and also at the abutting flanges to form the closed box section structure. The toothed edges of the panels preferably extend generally normal to one another and the length of the tab is not substantially less than the length of the notch which receives the tab so that the interlocking tabs and notches align the panels longitudinally relative one another pending the welding together of the panels. The weld may be a single sided spot resistance weld, an arc weld, or a laser weld.

Joint for single side welding and self-fixturing of closed steel sections

Joint and method for single side welding and self-fixturing of closed

A method and apparatus are disclosed for analyzing the dynamic resistance of a resistance spot welding process to determine the time of an expulsion event and use that time as the weld completion time for controlling weld termination via a weld feedback signal, controlling automatic current stepping, and identifying maintenance needs. A preconditioning pulse is used to stabilize the weld process and aid in obtaining interpretable resistance information. After an initial blanking period the resistance curve is analyzed by calculating first and second derivative values and applying several algorithms that make possible the computer recognition of characteristic resistance curve shapes resulting from weld expulsion under good geometry, bad geometry and edge weld conditions.

Method and apparatus for monitoring and controlling resistance spot

A method and apparatus are disclosed for resistance spot welding including applying a preconditioning pulse at the beginning of a welding process to stabilize the resistances at the interface of the sheets being welded and at the interface of the electrodes and the sheets. A current pulse is applied just after contact of electrodes and the workpiece when the electrode force is between about 10% and 75% of its final value to melt interface surfaces followed by a cooling time to permit dissipation of heat from the interfaces, and is finally followed by a conventional weld current schedule. The contact time is determined be electrically monitoring the conductivity between the electrodes as they are moved toward the workpiece. Alternatively, the applied electrode pressure is monitored to determine when sufficient electrode force is applied to the workpiece to achieve the proper resistance for the pulse application.

Method and apparatus for resistance welding

During a weld period the weld parameters are monitored and data representing the weld resistance curve and the power curve are acquired and stored for analysis by a suitably programmed computer. The derivative of R, R is calculated and stored and the function is divided by power P to obtain R/P. The resistance curve is searched to obtain the maximum value R.sub.m which occurs during the heating phase and the function R/P is searched prior to the time of R.sub.m to find the maximum of that curve representing the highest rate of resistance increase. Then the R/P curve is searched subsequent to its maximum to determine when the function reaches a specified percentage of the maximum. That value occurs at the knee of the resistance curve and approximates the onset of melting in the weld. A prediction of whether a weld is a nugget or a sticker is made by calculating the ratio of weld energy after the onset of melting to the total weld energy, the ratio of the resistance drop after the resistance peak to the peak resistance, and then a weighted sum of the energy ratio and resistance drop ratio. An edge weld geometry is detected by calculating from the resistance and power curves the weld energy during the period of expulsion, if any, divided by the cumulative energy between the onset of melting and the end of expulsion, a measure of expulsion intensity based on the maximum degree of resistance inflection, and then a weighted sum of the energy value and the inflection value.

Method and apparatus for detecting the onset of melting in a resistance

Method and apparatus for predicting and controlling the quality of a

Method and apparatus for detecting edge welds during resistance spot

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Royal Oak, MI, United States of America

Gregory L Nagel