Overview: COMPRESSION SPRINGS are open-coil helical springs wound or constructed to oppose compression along the axis of wind. Helical Compression Springs are the most common metal spring configuration. Generally, these coil springs are either placed over a rod or fitted inside a hole. When you put a load on a compression coil spring, making it shorter, it pushes back against the load and tries to get back to its original length. Compression springs offer resistance to linear compressing forces (push), and are in fact one of the most efficient energy storage devices available.
Compression Spring Configurations
The most common compression spring, the straight metal coil spring, has the same diameter for the entire length. Other configuration options for compression coil springs include hourglass (concave), conical and barrel (convex) types. The straight coil spring configuration is the standard coil type for Stock Compression Springs.
Ends: Ground ends provide flat planes and stability. Squareness influences how the axis force produced by the spring can be transferred to adjacent parts. Although open ends may be suitable in some applications, closed ends afford a greater degree of squareness. Squared and ground end compression stock springs are particularly useful in applications in which 1) high-duty springs are specified, 2) unusually close tolerances on load or rate are needed, 3) solid height must be minimized, 4) accurate seating and uniform bearing pressures are required and 5) a tendency towards buckling must be reduced.
Applications: Compression Metal Springs are found in a wide variety of applications ranging from automotive engines and large stamping presses to major appliances and lawn mowers to medical devices, cell phones, electronics and sensitive instrumentation devices. Cone shape metal springs are generally used in applications requiring low solid height and increased resistance to surging.
Compression Spring Parameters
Dimensions: Outer Diameter, Inner Diameter, Wire Diameter, Free Length, and Solid Height.
Free Length is the overall length of a spring in the unloaded position.
Solid Height is the length of a compression spring under sufficient load to bring all coils into contact with adjacent coils.
Spring Rate (stiffness): Spring Rate is the change in load per unit deflection in pounds per inch (lb. /in.) or Newtons per millimeter (N/mm).
Unit of Measures Stress: The dimensions, along with the load and deflection requirements, determine the stresses in the spring. When a compression spring is loaded, the coiled wire is stressed in torsion. The stress is greatest at the surface of the wire; as the spring is deflected, the load varies, causing a range of operating stress. Stress and stress range govern the life of the spring. The higher the stress range, the lower the maximum stress must be to obtain comparable life. Relatively high stresses may be used when the stress range is low or if the spring is subjected to static loads only. The stress at solid height must be high enough to permit presetting, yet low enough to avoid permanent damage since springs are often compressed solid during installation.
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