shearing, while among the round clinching tools split dies require the minimum joining force and the largest interlock. One benefit of clinching is the capability to join prepainted sheet metal commonly used in the appliance industry without damaging the painted surface. Clinching is an important means of fastening aluminum panels, such as hoods and decklids, in the automotive industry, due to the difficulty of spot welding of aluminum. Main advantages as compared to welding Clinching is used primarily in the automotive, appliance and electronic industries, where it often replaces spot welding. Clinching does not require electricity or cooling of the electrodes commonly associated with spot welding. Being a mechanical joining process, clinching can be used to join materials showing no electrical conductivity such as polymers or plastic-metal composites. In addition, it does not require a substrate preparation such as pre-cleaning of surfaces which is required for welding processes. This fact contributes to reduce the joining costs and the environmental impact (since chemical cleaning is not required). Clinching does not generate sparks or fumes. The strength of a clinched joint can be tested non-destructively using a simple measuring instrument to measure the remaining thickness at the bottom of the joint, of the diameter of the produced button depending on the type of tools employed. Life expectancy for clinching tools is in the hundreds of thousands of cycles, making it an economical process. Clinched connections performed on aluminum sheets have higher fatigue life as compared to spot welding. Main advantages as compared to adhesive joining Clinching does not require a pre-cleaning of the surfaces, which is needed before applying adhesives. Clinching is almost an instant joining process (the required joining time is lower than a second) while adhesive joining often requires a much longer time mainly owing to the curing of the joint (up to many hours). Clinched joints are less affected by environmental agents and effect of aging. Main limitations Because it is based on the plastic deformation of the sheets, clinching is limited by the sheet material formability (ductility). Metal ductility increases with temperature, so heat assisted clinching processes have been developed, extending the clinching "joinability". Increasing the joining temperature reduces the material's yield stress, so that less joining force is required. Different heating systems are used to heat the sheets before clinching: Convective heating is the cheapest solution. It is suitable for a wide range of materials, including metals