Which method is NOT commonly used for forming sheet metal?

Welding is not a method used for forming sheet metal; instead, it is a joining process that involves fusing two pieces of metal together using heat and sometimes pressure. In contrast, the other methods listed—bending or folding, shrinking, and bumping—are techniques specifically employed to shape sheet metal into desired configurations without altering its material properties through fusion.

Bending or folding involves creating bends at specific angles, allowing for the formation of structural components. Shrinking is a technique that reduces the overall size of a sheet, often used in creating curves or contours. Bumping refers to raising or shaping the metal surface to create desired profiles or indentations. All these methods focus on altering the physical shape of the sheet metal while maintaining its integrity.