Staking (manufacturing)
Encyclopedia
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.
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 rivet
s and screw
s.
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.
Interference fit
An interference fit, also known as a press fit or friction fit, is a fastening between two parts which is achieved by friction after the parts are pushed together, rather than by any other means of fastening...
between the two pieces. One workpiece has a hole in it while the other has a boss
Boss (engineering)
In engineering, a boss is a protruding feature on a workpiece.A common use for a boss is to locate one object within a pocket or hole of another object...
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.
Thermoplastic staking
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 plasticPlastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
stud protruding from one component fits into a hole in the second component. The stud is then deformed through the softening
Softening
Softening is a numerical trick used in N-body techniques to prevent numerical divergences when a particle comes too close to another . This is obtained by modifying the gravitational potential of each particle as...
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
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
techniques, staking has the capacity to join plastics to other materials (e.g. metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
) 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 rivet
Rivet
A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...
s and screw
Screw
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...
s.
In heat staking, a compression probe is heated to form a head on a thermoplastic
Thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
stud. This widens the application of staking to a broader spectrum of thermoplastic materials than is possible with cold staking, including glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
-filled materials. The quality of the joint is dependent on control of the processing parameters: temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
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.