Expulsion as shown below is to be avoided because it is not good for the integrity of the weld nugget. Before the advent of more advanced control systems, process engineers were more comfortable with the outcome of excessive expulsion over the occurance of missing welds. So the settings in the weld control were normally higher into the welding lobe - closer to the expulsion limits. This way, if there are deviations that would cause hotter or cooler conditions, the user sides with failure towards hotter. As a result, non adaptive systems can venture towards expulsion.

Excessive expulsion can be costly however. Besides causing burrs and other sharp safety concerns, expulsion causes debris that can affect other operations such as painting.