How Are Coil Springs Made?

Coiling

Coiling (winding) a wire is accomplished by any number of means but is mostly dependent upon the thickness of the wire. The thicker the wire, the more heat that is needed to bend and coil the metallic material. Thinner metal (.75 inches in diameter or less) are wrapped into a coil without the application of heat. Non-heated applications are treated by wrapping the metal around a mandrel inserted in to a power drill. The power drill's torque is reduced by adjusting the torque dial, and a low speed is set for safety. The trigger is pulled on the drill to begin winding the metal into a coil shape. The spacing between each loop of the coil is guided by a screw on a lathe. The leads are either straightened or looped for making connections to other components. Thick metal is heated and wrapped by an industrial machine around a mandrel, and then cooled in oil. The cooled metal is then tempered to give it extra hardness.

Hardening the Metal

Metal coil springs are tempered to give the metal a hardness that will keep its form. Tempering the spring is performed in a furnace. Because the metal has been coiled, a degree of stress remains in the metal. The metal is heated to allow the coil to retain some level of its original resilience. The heating process takes place in a furnace or oven, where the metal coil is heated at a constant temperature for about an hour (or other precalculated time). After heating, the metal coil is allowed to gradually cool and harden.

Metallurgy

Coil springs are typically made from steel alloys such as, stainless steel, carbon or chrome silicon. Beryllium copper, phosphor bronze and titanium are also used. However, coil springs are made more resistant to high heat conditions by constructing the coil form from ceramics rather than heat-conductive metals.

Engineering

Mathematic equations are employed to determine the composition, size, diameter, external force and the number of coils needed for producing the product. Coil springs made for electronic purposes are calculated for resistance, voltage and cross-sectional area (see "Resources"). Coils made for electronic components are wrapped around a bobbin.

Final Stage

The metal coil is not finished until it has been coated or electroplated. Chromium/ zinc is plated onto the spring, or the spring is dipped in liquidized rubber. If the spring is made of carbonized steel and it is electroplated (placed in electrically charged fluids), it will become easily breakable upon cooling (which takes a few hours). To rectify the fragility of the electroplated spring, the manufacturer will cure the spring in an oven for a few hours at a temperature of nearly 400 degrees Fahrenheit.