Compression springs are an open-coil helical spring that offers resistance to a compressive force applied axially. Compression springs are usually coiled as a constant diameter-cylinder. Other common forms of compression springs such as conical, concave, (barrel,) convex (hourglass) or various combinations of these are used as required by the application. While square, rectangular or special-section wire may have to be specified, round wire is predominant in compression springs because it is readily available and adaptable to standard coiler tooling. Compression springs should be stress-relieved to remove residual forming stresses produced by the coiling operation. Advanex Americas can produce compression springs with wire diameters of .005″ – .320″ in a variety of materials and specifications.
There are a few options when it comes to end type selection for a compression spring. The two most common are ‘closed and ground’, and ‘closed not ground’. Generally speaking, end grinding is an expensive process, and is therefore to be avoided wherever possible. The ‘closed not ground’ option can often be selected where spring end squareness is not critical. As the spring index (mean diameter/wire diameter) ratio increases, the need to grind reduces, as large index springs tend to stand fairly square without grinding. Grinding can be difficult on large index springs anyway, as the spring yields too easily under the pressure applied by the grinding wheel.
For small wire diameters, grinding is also impractical, so unground ends are normally specified for wire under 0.5mm, although it is possible to grind smaller wires, with care, if absolutely necessary.
In many applications however, there is no question that the springs will need to be ground. For instance, valve springs will need to be very square to ensure that the valve seat seals properly. End grinding can also help with spring stability; an unground spring is more susceptible to buckling under load than one that is ground.
Other end type possibilities exist, such as ‘open’, ‘open and ground’, and ‘half-closed’ (ground or unground). These are used comparatively rarely however, as spring stability is poor.
Multiple inactive coils are sometimes used at the ends of compression springs. Generally this is done to help prevent tangling. When compression springs are packed in bulk, springs will often tangle (dependent upon the design). Using perhaps three or four dead coils at each end means that these close-coiled sections are longer than the gap between the active coils in neighboring springs, and are therefore less likely to lock together. Contact us today for your custom spring manufacturing needs.