Selection of tension springs and compression springs – Overview / uses / application examples

Tension springs and compression springs are mechanical components that can be used in a variety of industries.

This article is dedicated to tension springs and compression springs by providing an overview and illustrating their various uses in mechanical engineering and custom machine construction. The calculation of the springs is not discussed in this blog.

Description of Tension Spring

Tension Springs are mechanical elements designed to generate tensile forces when pulled apart.

They usually consist of a coiled wire and can be constructed to store energy and to release energy as needed. Tension springs are capable of exerting linear forces in the direction of tension and are therefore extremely useful in applications where motion, spring force and control are required.

For easy fastening, there are tension springs with hooks or tension springs with eyelet.

Additional applications in mechanical engineering include the use of tension springs in safety switches and electrical circuits. For safety switches, the tension spring keeps the switch in an “off position” until it is manually reset. Tension springs can be used as contact elements or connecting elements in electrical circuits and devices.

Description of compression springs

Compression springs are useful in certain mechanisms for controlling movement or keeping components in position. For example, in control buttons or switches, compression springs are used to return the switch to its initial position. In safety valves, they ensure that the valve only opens at a certain pressure.

Compression springs are standardized in DIN 2098.

Advantages of compression springs and tension springs

Springs have a long service life, provided they are properly designed for static and dynamic loads. In addition, springs are characterized as being maintenance-free. They can adjust their length and therefore do not have to be readjusted. Other benefits may include:

• Shock absorption
• Precise control
• Simple design
• Low weight
• Relatively high resistance to environmental influences

The spring material itself can also serve a purpose. For example, plastic springs are particularly light compared to steel springs and springs made of stainless steel or titanium are more corrosion-resistant.

The material influences the main properties of the spring. Plastics are light and suitable for damp environments, and springs made of titanium are suitable with high spring rates at a lower weight. Stainless steel springs are corrosion-resistant, but not as light as plastic, but can absorb a higher load.

Design and characteristics of compression springs and tension springs

Springs are primarily designed based on acting maximum force, spring travel, material and spring constant. In addition, factors such as available installation space or spring force characteristic curve play a role in special applications. When selecting tension springs and compression springs, the following parameters can be taken into account:

Construction of the spring

The construction of a spring depends on the requirements and is based on the required spring force, the direction of movement and the ambient conditions.

Tension springs and compression springs must be designed to meet the expected loads and the desired service life. The selection of the material also plays an important role here. For example, tension springs made of stainless steel are used where corrosion resistance is important.

Spring Winding Outer Diameter

The outer diameter for springs is the outer diameter of the spring winding or spring body. It primarily affects the space that the spring occupies. The larger, the less suitable the spring is for applications with limited space, such as electronics. The form factor should also be observed so that adjacent components are not overloaded. The outer diameter also influences the spring constant. The larger the outer diameter, the higher the load, the spring can absorb at the same travel and wire diameter.

Conical compression springs differ from conventional cylindrical helical coil springs, for example due to the conical shape of the spring winding, and they have a progressive spring characteristic.

Wire diameter of the winding

The wire diameter is the diameter of the wire material. In addition to the factors that also influence the outer diameter, the wire diameter also has a direct influence on the spring travel. The spring travel is the difference between the free length and the compressed or stretched length of the spring under load.

Springs with a larger wire diameter generally have a smaller spring travel, while springs with a smaller wire diameter allow a larger spring travel.

Free length of the spring

The free length indicates the length that the spring has at the two ends without load. It is the part of the load area in which the spring can operate effectively. The free length is the starting point for calculating the spring travel.

Maximum tension length of a tension spring

For a tension spring, the maximum tension length is the maximum length that can be achieved at both ends when force is exerted. The maximum tension length limits the spring travel. The longer the maximum tensile length with the same material, diameter and wire strength, the greater the absorbable load.

Maximum compressed length of a compression spring

The maximum compressed length is the shortest possible length of a compression spring that is possible when compressed under a certain compression load without the compression spring permanently deforming or failing. The spring must not reach the block length - the length when the spring coils touch each other. The spring design takes into account a buffer for the block length to prevent bottoming out.

Spring constant for calculating helical coil springs

The spring constant (or spring rate or spring stiffness) describes how much a helical coil spring deforms when a specific force is exerted on it. It is measured in the unit Newton per meter (N/m).

The higher the spring constant under constant conditions, the:

• higher the absorbable load
• lower the spring travel
• higher the resonance frequency
• greater the damping effect

Depending on the application, a high degree of rigidity may be required, for example, in order to control precise forces or movements. If a softer suspension or better shock absorption is preferred, this can be achieved with lower rigidity.

Would you like to learn more about calculating tension springs and compression springs? Then please read the article Calculation for designing springs.

Relaxed tension of helical coil springs

The relaxed tension is the internal stress of a coil spring in its neutral or relaxed position before an external force is exerted on it. A higher relaxed tension results in a stiffer spring, while a lower relaxed tension results in a more flexible spring.

Application examples for tension springs would be, for example, mechanical engineering, where tension springs are used to pull moving parts back into the initial position. This allows them to be used in lifting or positioning systems to maintain a balance or constant tension.

The textile industry uses tension springs in spinning machines and weaving machines. There they keep the threads under tension and ensure that the thread has the correct tension and is pulled evenly during the production process.

At MISUMI, you will find a wide range of tension springs and compression springs for many different applications.