Method of friction stir spot welding

A method of friction stir spot welding, comprising the steps of:

• storing a lookup table in non-transitory computer readable memory, the lookup table including a data array for a plurality of materials and a plurality of thicknesses for each of the materials, and for each of the thicknesses of each of the materials, an initial dynamic welding parameter, a final dynamic welding parameter, and a type of varying function for changing the dynamic welding parameter from the initial to the final parameter during friction stir spot welding of a lap joint of a workpiece having the corresponding material and the corresponding thickness to maximize strength of the spot weld;
• receiving an input material and an input thickness associated with the input material;
• obtaining the initial dynamic welding parameter, the final dynamic welding parameter and the type of varying function associated with the input material and the input thickness from the lookup table;
• transmitting the initial dynamic welding parameter, the final dynamic welding parameter, and the type of varying function to a rotating tool;
• and
• performing friction stir spot welding with the rotating tool, the rotating tool being controlled to operate with the initial dynamic welding parameter, the final dynamic welding parameter, and the type of varying function.