Compression Springs

Compression springs: 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. Compression springs offer resistance to linear compressing forces (push), and are in fact one of the most efficient energy storage devices available.
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: configuration

The most common compression springs, the straight metal coil spring, have 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 of compression springs:

Compression 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
Stress: When a compression springs 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. The dimensions, along with the load and deflection requirements, determine the stresses in the spring. Stress and stress range govern the life of the spring. 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.
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.

Compression springs: Physical parameters

• d (wire diameter): This parameter describes the diameter of wire used as material for spring.S (shaft): This parameter describes the maximum diameter of spring shaft in industrial applications. Di (internal diameter): Internal diameter of a spring can be calculated by subtracting the doubled wire diameter from the external diameter of a spring. De (external diameter): External diameter of a spring can be calculated by adding the doubled wire diameter to the internal diameter of a spring. H (hole): This is the minimum diameter of the hole in which spring can work. P (pitch): Average distance between two subsequent active coils of a spring. Lc (block length): Maximal length of a spring after total blocking. This parameter is shown in the picture on right. Ln (allowable length): The maximum permitted length of a spring after loading. If deflection is higher it may cause plastic deformation (the non-reversible change of shape in response to an applied force). For many springs danger of deformation do not exists. In this case Ln = Lc + Sa, where Sa is the sum of minimum permissible spaces between active coils.L0 (free length): Free length of compression springs is measured in its uncompressed state after previous one time blocking. Nr of coils: This is a total number of coils in a spring - in the picture above it is equal to six. To calculate number of active coils substract two terminating coils from total number of coils. R (spring rate): This parameter determines spring's resistance, while it is working. It is measured in 1 DaN/mm = 10 N/mm. L1 & F1 (length at force F): Force F1 at length L1 can be calculated from equation : F1 = (L0-L1) * R. Equation derrived from previous for calculating L1 : L1 = L0 - F1/R.
• Grinding: Defines whether or not the ends of a spring are ground.

federn druckfedern zugfedern compression springs conical springs torsion springs