Which of the following welding types primarily benefits from having minimal contact area between parts?

The principle behind projection welding involves creating molten metal at specific projections or raised areas on the workpieces that are being joined. This technique relies on minimal contact area between parts to effectively focus the heat and pressure on the projections. The reduced contact area enhances the efficiency of the welding process by concentrating the electrical current and thermal energy, allowing for faster heating of the joint and minimizing the risk of overheating surrounding material.

In projection welding, the process can be more controlled, leading to consistent and strong welds while using less energy. By having only the projections in contact, it ensures that the heat generated is localized, which aids in achieving a good fusion at the point of contact without affecting the larger areas of the parts being welded. This makes projection welding particularly effective for joining components with specific design features that can facilitate this method.

The other welding types mentioned do not primarily focus on minimizing the contact area in the same way. Resistance spot welding, for example, does use point contacts but is less specialized in this regard than projection welding. Arc welding and oxy-acetylene welding are generally more suited to joint designs that allow for wider contact areas and do not utilize the same localized heating principles as projection welding.