A tension spring, also known as a tension spring, increases its force when the spring is stretched beyond its original length. In order to generate tension, spiral coils are wound together and then tightly wound together. One of the most common types of springs is tension spring, which is often used in lever based devices such as garage doors. They are typically used to provide rebound force for components that stretch during activation.

A tension spring is a tightly wound coil that can store and absorb energy and resist forces applied to it.
There is initial tension in the spring coil, which determines the tightness of the coil connection.
Many different types of materials are used to produce tension springs, such as copper alloys, carbon steel, stainless steel, nickel alloy composite materials, etc.
Stainless steel is the most economical and widely used in spring production.
After different types of processing, the spring is more durable and has better conductivity.
In the production of tension springs, certain parameters need to be considered, such as spring diameter, wire diameter, initial tension, ring end, etc.
There are many different types of ring heads on the market, each with its own function. Some require tools to produce, while others do not.
Stretch springs are used in many things in our daily lives, such as garage doors, toys, appliances, fence doors, and so on.

Customized stretch spring
General Wire Spring is a stretching spring manufacturer specializing in the production of customized stretching springs and customized stretching spring ends, including machine rings and cross ring ends, as well as other options to adapt to different tensions. Stretch springs absorb and store energy by resisting tension. Various types of ends are used to connect tension springs to a force source.

General Wire Spring offers a variety of stretch springs suitable for various types of applications. The types of tension springs include hooked end, tapered end, machine cut flat end, annular end, etc. Learn more "
Stretch spring

Stretch the end of the spring
There are various types of end fittings that can be installed on tension springs, limited only by imagination, which may include threaded inserts, reduced and enlarged holes on the side or center of the spring, extension rings, hooks or holes located at different positions or distances from the spring body, and even rectangular or teardrop shaped end fittings. When the opening is less than one wire diameter, the end is a loop; when the opening is greater than one wire diameter, the end is a hook. However, the most common ones so far are the machine loops and cross loops shown in Table 1. These ends are made in one go using standard tools and should be specified as much as possible to reduce costs.
It should be noted that as the space occupied by the mechanical loop decreases, the transition radius also decreases, resulting in significant stress concentration. This will greatly shorten the lifespan of the spring and lead to premature failure of the spring.
Most stretching spring failures occur in the end region. In order to maximize the service life of the spring, the path of the steel wire flowing into the end should be smooth and gentle. Tool marks and other stress concentrations should be kept to a minimum. The recommended minimum bending radius is 1/2 times the diameter of the steel wire.
In the past, many ends were made as secondary operations. Nowadays, with the help of modern machinery and computer-controlled machines, many custom stretch spring ends can be made as part of the winding operation. Due to the wide variety of machines available for single operation winding and coiling, it is recommended to consult the spring manufacturer before completing the design.

design and construction
The tension spring is carefully designed to withstand tensile forces without compromising its integrity. There is no spacing between the coils, which means there is initial tension sandwiched between the closed coils, allowing the spring to smoothly extend a considerable distance without causing mutual interference between the coils. This seamless extension is crucial for applications that require a lot of movement or stretching.
The typical design of a tension spring includes coils that can be freely separated when the spring is stretched. The end of the spring is usually equipped with a hook or loop, making it easy to connect to other components in the system. The overall structure aims to provide maximum resistance to tension while maintaining flexibility and durability.
Leave gaps for custom tension springs that are dynamically loaded. When deflected, the tension spring does not require a central axis or hole to prevent buckling. Sudden dynamic loading or unloading may cause lateral vibration of the tension spring, which may result in additional stress and lead to noise and premature failure. Appropriate gaps can reduce or alleviate these stresses and outcomes.
Static working stress - Due to the frequent stretching, twisting, or marking of the end of the tension spring wire during the coiling process, the maximum recommended stress at the end is lower than that of the spring body.
Tolerance Guide - Due to different processing capabilities of some spring manufacturers, tolerance values may change. Please discuss your commercial free length, end angle relationship, and load tolerance requirements with your manufacturer.
Strict tolerances may increase manufacturing costs.

The unique characteristics of tension springs
The characteristic of a tension spring is that the coil is uniform, tightly wound together when not subjected to tension load, and will pull apart when subjected to increased tension load. The following are the materials and characteristics that enable them to provide this functionality.
Material and Construction
Stretch springs are made of high-grade steel or metal alloys and are highly favored for their strength and flexibility, capable of withstanding large tensile forces. Stretching springs are significantly different from compression springs as they typically come with hooks or fixed end rings.
Load bearing performance
The load-bearing capacity of a tension spring is one of its major characteristics. These springs are specifically designed to work under tension, maintaining strength and elasticity even when stretched. The load capacity depends on factors such as wire diameter, number of coils, and material strength, and is carefully calibrated to meet application requirements. This precision enables the stretching spring to effectively absorb and store energy, providing the necessary force during stretching and reliably restoring its original shape.

Materials used
The performance and lifespan of tension springs are largely influenced by the materials used in their manufacturing. Common materials for tension springs include:
Stainless steel tension spring
Stainless steel 302 A313: Stainless steel is known for its corrosion resistance and is ideal for environments exposed to moisture, chemicals, or other corrosive elements. This makes stainless steel tension springs very suitable for outdoor applications, marine environments, and industries where hygiene and cleanliness are crucial.
Piano wire tension spring
ASTM A228 steel wire for piano: This type of steel wire is highly praised for its high tensile strength and precise performance. Piano wire tension springs are commonly used in applications that require consistent and precise application of force, such as precision machinery and instruments.
The selection of materials not only affects the strength and flexibility of the spring, but also its ability to resist fatigue and corrosion. Choosing the appropriate material is crucial to ensure the reliable operation of the spring in the expected environment.