Influence of welding current on RW machine follow-up behaviour, a practical test method

摘要

Machine dynamics of resistance spot welding (RSW) machines significantly influence process capability and performance. Integrated mechanical, electrical and thermal models of the RSW process also require accurate specification of machine dynamics. The influence of specific machine configurations is extremely difficult to predict starting from individual component specifications, and it has also been difficult in the past to accurately measure dynamic performance under typical operating conditions. This paper presents a reliable and very straightforward new method for the characterization of machine performance. This method has the advantage that it can be used to characterize the performance of RSW machines under realistic operating conditions. The test, the “Exploding Wire Test", uses a small diameter wire placed between the welding electrodes. The machines’ performance can subsequently be measured at the required operating load as the wire disintegrates when welding current is applied. This paper also describes the negative influence of the welding current itself on the machines’ mechanical behavior. The welding machines’ performance characteristics can be used directly, in order to optimize process operation towards a specific and demanding application, or serve as an input into an integrated mechanical / electrical / thermal model of the RSW process. The test method is relatively simple (although sophisticated instrumentation is required to accurately measure dynamic behaviour) and it can be used over a wide range, from micro-joining to heavy duty applications, and can be applied to projection welding as well as resistance spot welding.