Expulsion of the molten material onto the bolt thread and bolt welded sheet during projection welding, causes burr formation on these parts. Used in all sectors and notably in the automotive industry, this situation arises major security problems causing functional loss and the corrosion risk. Moreover, these defects cause the loss of prestige and the power on competition by engendering customer complaints. In this study, burring problem is minimized without making any concessions about weld strength. Projection dimensions of weld bolt, effect level and the optimized values of welding process parameters are defined by using Taguchi and multi-objective optimization methods. Reliable results are obtained by using multi-objective optimization methods, including both two of the response factors, which are expulsion and burring index and weld strength. In terms of welding process, the parameters such as weld current, electrode force and projection height are found to be the effective factors which minimize expulsion and burring defects, then optimized values of these parameters are defined. [ABSTRACT FROM AUTHOR]