Staking is the process of connecting two components by creating an interference fit between the two pieces. One workpiece has a hole in it while the other has a boss that fits within the hole. The boss is undersized so that it is a slip fit. A staking punch is then used to compress the boss radially and form an interference fit between the workpieces. This forms a permanent joint.[1]
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Thermoplastic staking, also known as heat staking, is the same process except that it uses heat to deform the plastic boss, instead of cold forming. A plastic stud protruding from one component fits into a hole in the second component. The stud is then deformed through the softening of the plastic to form a head which mechanically locks the two components together. It is a versatile technique benefiting from being quick, economical and consistent. Unlike welding techniques, staking has the capacity to join plastics to other materials (e.g. metal) in addition to joining like or dissimilar plastics and it has the advantage over other mechanical joining methods in eliminating the need for consumables such as rivets and screws.
In heat staking, a compression probe is heated to form a head on a thermoplastic stud. This widens the application of staking to a broader spectrum of thermoplastic materials than is possible with cold staking, including glass-filled materials. The quality of the joint is dependent on control of the processing parameters: temperature, pressure and time - a typical cycle time being between 1 and 5 seconds. Heat staking has the advantage that parts can be disassembled. It also has the flexibility to allow the simultaneous formation of a large number of studs and to accommodate a variety of stud head designs. There are four main methods to stake: hot air/cold stake, ultrasonic stake, direct contact stake, and infrared stake.