Poor fit-up condition in resistance spot welding

An experimental setup for poor fit-up condition research, which makes it possible to analyze poor fit-up conditions of different intensities and also quantify them is presented. The intensity of poor fit-up condition can be estimated by measuring the welding force during the initial contact between the electrode tips and the weldpieces. In order to reduce the negative influence of the poor fit-up condition on weld strength an addition of preheating phase was studied. Although it helps to increase the weld strength, a significant gap remains between the weld strength of non-deformed welds and poor fit-up welds even at large preheating currents.