Characterisation of Dynamic Mechanical Behaviour of Resistance Spot Welding Machines

Patrick Van Rymenant and David Yapp

Machine dynamics of resistance spot welding (RSW) machines significantly influence process capability and performance. Integrated mechanical 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, for the first time, two new methods for characterisation of machine performance. Both methods have the advantage that they can be used to characterise the performance of RSW machines under realistic operating conditions.  The first test, the “free fracture test” uses a series of precisely machined bars, designed to fracture at a specified load.  The dynamic performance of the machine can then be measured accurately for a range of machine operating loads. The second test, the “exploding wire test”, uses a small diameter wire placed between the electrodes. The machine performance can also be measured at the required operating load as the wire disintegrates when the current is applied. The performance of both methods is compared, and their advantages and limitations are discussed. Typical data is presented for a range of welding configurations.

Patrick Van Rymenant

David Yapp