Compression Springs

Springs are mechanical components that have mechanical energy stored in them, capable of undergoing structural changes when subjected to external forces. They are compressed when a force is applied to them and lose their deformed structure when the force is taken off. A very common application of springs is for suspension in vehicles, where the springing action is triggered when the wheel comes in contact with some obstacle, the spring is compressed and the wheel is brought back to normal position when it loses contact with the obstacle. Springs are also a common component in weighing scales, where the force displacement transducer principle is applied.

Springs are available in many types. Some important types of springs are: leaf springs, compression springs, extension springs, disc springs, snap springs, torsion springs, etc. Compression springs (also called coil springs) are the most commonly used in many applications. The disadvantage of most metal springs is that the material cannot store the energy uniformly; meaning the stress throughout the spring varies. The wire of a helical compression spring is therefore usually a circular cross-section.

Compression springs are helical in shape and have an open coil. These apply an opposing force to the compression along the axis. These springs offer a good resistance to linear compressing forces and are among components that efficiently store significant amounts of mechanical energy in them. Several types of compression springs are available separated by their diameter and shape. Straight compression springs have even diameter across the entire length. Concave, convex, conical, barrel, etc. are the other types of compression springs.

Materials used for fabricating compression springs:

Alloys of steel are used to manufacture most types of springs. Some of the most common types of spring steels are oil tempered wire, chrome silicon, chrome vanadium, 302 and 17-7 stainless. Depending on the characteristics and need of the applications a few other materials are also used to fabricate springs. Beryllium copper, phosphor bronze, Inconel, Monel, and titanium are some of the other materials used to make springs.

Important factors for selecting a compression spring:

Outer diameter, inner diameter, wire diameter, length, and height are the important dimensions that must be considered.

• Length refers to the total length of a spring in its uncompressed position.
• Height is the length of spring when subjected to adequate load such that all the coils are in contact with each other.
• Spring rate is the stiffness of the spring and is denoted by the ratio of the force applied to the spring and the deflections undergone by the spring. It is given in Newton's/millimeter.
• Buckling value of the compression spring – it is important to note this value at which the spring may become permanently deformed when subjected to a load over a certain value.
• Spring index is the ratio of coil diameter to wire diameter. Springs with lower indices are difficult to manufacture and their curvature induces a stress. If the index of spring is below 3 then it is almost of no use. The most preferred springs have indices between 5 and 10.

Applications:

Compression springs are found in a wide variety of applications like automotive engines, large stamping presses, and major appliances. They are also used in specific applications like lawn mowers and cell phones. Sensitive instrumentation devices used in process control applications, medical electronic devices also use compression springs in some equipments.