Clinching, also known as press joining, is a high-speed, mechanical fastening technique for point joining of sheet metal components. It is suitable for ductile metal sheets from around 0.5 to 3mm thick, up to a total joint thickness of about 6mm. Clinching requires no consumables or pre-drilled holes and is performed in a single step, making it an inexpensive and simple technique.
A typical process cycle of this mainly proprietary technique is shown in the illustration. The sheets are initially clamped between the blankholder and the die assembly (stage 1). The punch is then forced onto the sheets, and locally pushes them into the die (stage 2). As the deformed sheets touch the bottom of the die, further downward movement of the punch forces the material to flow radially and form a button (stage 3). This material flow, made possible by the sprung segments of the die assembly, provides the mechanical interlock which holds the sheets tightly together. Finally, the punch is retracted (stage 4).
In some cases, solid dies are used, instead of the sprung type shown in the illustration. Also, rectangular punches which partly pierce the sheets may be used.
Clinched joints are mainly used for non-visible, non-critical joints because they are generally not as strong as resistance spot welds or self-piercing riveted joints.
Further information:
FAQ: What is clinching used for?
Clinching - a basic guide