Compression springs, also known as helical compression springs, are fundamental mechanical components. They are one of the most common types of springs that can be found in many everyday applications. These springs are designed to store and release energy efficiently when subjected to compressive forces, making them a crucial part of various mechanical systems.
In this article, we will discuss what compression springs are, how they work, and their diverse applications.
What Are Compression Springs?
Compression springs, sometimes called coil springs, are a type of mechanical spring that has an open-coiled helical design. These helical springs produce resistance to compressive loading applied axially. In other words, these springs are designed to absorb and store energy when subjected to a compressive force and release the energy when the force is removed.
Types of Compression Springs
There is a wide range of compression springs available, each with its own characteristics, design, and applications. The different types are listed below:
Regular Compression Springs
Regular compression springs, also known as straight coil compression springs, are the most common and widely used type of compression spring. Straight coil compression springs maintain a consistent outer diameter (OD) and inner diameter (ID) along their entire length, with each coil having the same diameter. The ends of these springs can be either ground or closed, featuring a 270-degree bearing surface. Unlike tapered compression springs, which have a conical shape, straight coil compression springs maintain a cylindrical shape. When compressed, they provide a uniform and linear resistance force. Regular compression springs are versatile and find application in numerous industries, from automotive and aerospace to consumer products. See Figure 1 for an illustration of regular, or straight coil, compression springs.
straight coil compression springs
Straight coil compression springs. Image Credit: https://www.indiamart.com/proddetail/straight-compression-springs-12672803130.html
Conical Compression Springs
Conical compression springs, as the name suggests, have a tapered or conical shape, with a smaller diameter at one end and a larger diameter at the other, as seen in Figure 3. This design results in a variable rate of force increase during compression. Conical springs offer advantages over standard compression springs, primarily in terms of stability. These tapered springs, with their larger outer diameter typically positioned at the base, provide enhanced stability. They are less prone to buckling and maintain their balance effectively even when subjected to compression.
Conical springs are advantageous when a gradual increase in resistive force is required. This makes them suitable for applications like shock absorption and automotive suspension systems. They are also commonly used in electrical contacts, such as push buttons and battery connectors, ensuring reliable electrical connections. In the firearms industry, some manufacturers utilize conical springs within the weapon’s firing mechanism to enhance its performance.
conical compression springs
Conical compression springs. Image Credit: https://www.asraymond.com/mechanical-wire-springs/conical-compression/spec-conical-compression-springs-165112/?Imperial=true
Hourglass Compression Springs
Hourglass compression springs (illustrated in Figure 4) feature a distinctive waist-like center section, resembling the shape of an hourglass. This design allows these springs to store more energy for a given length compared to regular compression springs. Hourglass springs are often employed in applications in which space constraints necessitate a compact spring with higher energy storage capacity.
hourglass compression springs
Hourglass compression springs. Image Credit: https://m.indiamart.com/proddetail/hourglass-compression-spring-19383513473.html
Barrel Compression Springs
Barrel compression springs have a barrel or convex shape, with a larger diameter in the center and smaller diameters at both ends. These springs can produce linear or nonlinear force. Barrel springs are chosen when maintaining a constant force is essential, such as in automotive valves and hydraulic systems. An image of barrel compression springs can be seen in Figure 4.
barrel-compression-springs
Barrel compression springs. Image Credit: https://www.indiamart.com/proddetail/barrel-springs-3719783962.html
Constant-Pitch Compression Springs
Constant-pitch compression springs maintain a consistent coil spacing along their entire length. This design ensures a uniform force profile during compression. The spring rate (the amount of force required to compress the spring a certain distance) remains relatively constant along the entire length of the spring. These springs are favored in applications in which predictability and consistency of force are critical, such as in industrial machinery and medical devices.
The difference between constant-pitch and variable-pitch compression springs are illustrated in Figure 5.
Variable and constant pitch springs
Differences between variable-pitch springs and constant-pitch springs. Image Credit: https://kbdelta.com/blog/spring-pitch.html
Variable-Pitch Compression Springs
Variable-pitch compression springs have varying coil spacing along their length. This variability allows for precise control over the spring’s behavior, including altering the rate of force increase during compression. Engineers use variable-pitch springs when they need fine-tuned and customized spring characteristics to meet specific application requirements.
Compression Spring End Types
Compression spring end types play a crucial role in the functionality and stability of the spring within various applications. Choosing the appropriate end type depends on factors like the available space, required stability, and cost considerations. Listed below are the different end types of compression springs, as seen in Figure 6:
compression spring end types
Different types of compression spring end types. Image Credit: https://www.acxesspring.com/coil-spring-design-basics.html
Open-End Compression Springs
Open-end compression springs are characterized by having both ends of the spring with open coils. This design means that the spring cannot stand or remain stable on its own without external support, typically a rod or shaft. Open-end compression springs are used in applications in which it’s essential to avoid increasing the solid height of the spring during compression, making them suitable for situations with limited space.
Closed and Squared End
The closed and squared design is the most commonly used style for compression spring ends. These ends are characterized by the fact that the final coil at each end of the spring is tightly closed during the manufacturing process on the coiling CNC machine. This design enables the spring to stand vertically on a flat surface when not under compression, which is advantageous for various applications.
However, it’s important to consider the slenderness ratio of your compression spring. The slenderness ratio is the proportional relationship between the spring’s diameter and its free length. If the free length of the spring is approximately four times or greater than its outer diameter, there is a possibility that the spring may not stand vertically on a flat surface, and it could bend or buckle when compressed.
To ensure proper functionality, especially when dealing with compression springs with a high slenderness ratio, it is advisable to place the spring over a shaft or inside a hole. This prevents the spring from bending or buckling, allowing it to perform its intended function effectively.
Closed and Ground End
Closed-ended, ground compression springs resemble the closed-end design, with the distinction that the ends are ground to create an even flatter plane. These end types are also common, but they come with a higher cost than closed and squared ends. The primary reason for the higher cost is that the ends are not ground directly from the coiling CNC machine, as is the case with springs that have closed and squared ends. Instead, grinding the ends of these springs is an additional manufacturing step that involves manual labor, adding to the production costs.
The benefit of closed and ground ends lies in their ability to ensure that your compression spring stands vertically upright on a flat surface, even when the slenderness ratio is significant. In situations in which it’s crucial for your spring to maintain a perfectly vertical orientation and it won’t be passing through a shaft or inside a hole, closed and ground compression spring ends prove to be the best choice. This added feature provides the stability and balance required for specific applications, making it a valuable option despite the higher manufacturing costs.
Double Closed End
In the double closed-end configuration, two extra windings are positioned adjacent to the last winding, providing added support to both the top and bottom of the coil spring. This enhanced stability is particularly beneficial when dealing with compression springs with a substantial outer diameter and a slender thread thickness, as well as with conical compression springs. Compression springs featuring double closed ends exhibit a unique characteristic – their ends can slide beneath the preceding coil during compression, further enhancing their stability. These springs typically find application in high-precision mechanisms and equipment.
What Are the Applications of Compression Springs?
Compression springs find a wide range of applications across various industries due to their ability to store and release energy efficiently under compressive loads. They are commonly found in door locks, firearms, and aeronautic applications like: guidance systems, air turbines, and engineering controls. They are also widely used in the automotive industry in: shock absorbers, suspension and brake systems, clutch mechanisms, and seat components. Listed below are some common applications of compression springs:
Medical Devices
Compression springs are widely used in the medical industry for medical devices. These springs can be found in small devices like: syringes, pill dispensers, and inhalers. They are also widely used in larger medical tools and devices, such as: orthopedic and surgical tools, prostheses, catheters, staple guns, valves, wheelchairs, peristaltic pumps, insulin pumps, and endoscopic devices.
Electronics
In the electronics industry, compression springs play a crucial role in ensuring the functionality of electronic components and connectors. They are found in devices like: switches, battery compartments, and circuit board connections, guaranteeing proper electrical contact.
Precision Instruments and Tools
Precision instruments and tools demand the utmost accuracy, and compression springs rise to the occasion. They are employed in devices such as: micrometers, force gauges, and laboratory equipment, contributing to tasks like: load testing, calibration, and shock absorption.
Industrial Equipment
Compression springs can be found in machinery, conveyors, and assembly equipment in which they absorb shocks, maintain tension, and provide return forces. Industries like: manufacturing, packaging, and construction rely on these springs for smooth operations. These springs are used for: valves, conveyor systems, actuators, and die and mold ejection, among other applications.
Mining and Drilling Equipment
In the mining industry, compression springs endure harsh conditions, dampening vibrations, maintaining tension in drilling components, and ensuring the safety and reliability of mining and drilling equipment.
Pens or Notebooks
Everyday items like pens and notebooks incorporate compression springs to enhance their functionality. These springs enable the smooth exposure and retraction of the pen tip.
Toys
In terms of toys, compression springs can be used to provide the kinetic energy necessary for motion, action, and sound effects in various toys, from push-button toys and wind-up toys to spring-loaded pop-up surprises.
Mattresses
Compression springs are integral components of mattress support systems, adapting to body weight and shape, and enhancing comfort and durability.
How Are Compression Springs Manufactured?
The manufacturing of compression springs begins with coiling, in which a wire is fed through a straightening process to ensure it’s as straight as possible. CNC machinery, programmed with specific settings, is used to modify the arbors and arms to make the spring. These adjustments include parameters like: the spring’s pitch, free length, and the number of coils. High-speed cameras record images during this phase, allowing for precise measurements and necessary adjustments to maintain tolerance. Once the spring is formed, it proceeds to the stress-relieving step.
Coiling imparts stress to the wire, making it brittle. To rectify this, the spring is heated in an oven, causing the coil to solidify in its intended shape and form metallic links. The oven maintains the coil’s temperature at the correct level for a predetermined period before slowly cooling it.
After the stress-relieving process, the wire undergoes various finishing operations tailored to its intended application. These finishing steps transform the spring from its initial state into a specialized tool suitable for specific tasks. Key finishing procedures include: grinding, strength peening, setting, and coating.
What Are Compression Springs Made Of?
Compression springs are crafted from a variety of materials to suit specific applications. Common materials used in manufacturing compression springs are hard-drawn steel, stainless steel, spring steel, and steel music wire. The choice of material depends on factors such as the intended use, required strength, and environmental conditions. For example, stainless steel is a favored choice due to its corrosion resistance, even when exposed to chemicals or moisture. It’s a robust option, ideal for applications in which durability is critical, and it can be used continuously without breaking.
Materials like: titanium, phosphor bronze, and beryllium copper alloy are used on occasion, particularly in high-temperature environments. Each material has specific characteristics and temperature limits, ensuring the correct match for the intended application.
Where Can I Find Companies That Manufacture Compression Springs?
If you’re looking for compression spring manufacturers, the ThomasNet Supplier Discovery Platform is an excellent resource to start your search. ThomasNet offers a vast directory of companies categorized by their manufacturing services and products. This platform is a valuable tool to connect with compression spring manufacturers and suppliers.
By using the ThomasNet Supplier Discovery Platform, you can efficiently locate a wide range of companies specializing in compression spring manufacturing. This resource simplifies your search process by providing access to a comprehensive database of businesses, ensuring that you can find the right manufacturer to meet your specific needs.
Compression Springs vs. Extension/Tension Springs
Compression springs and extension/tension springs differ significantly in their construction and usage. Compression springs are designed to absorb and store energy when subjected to compressive forces, such that their ends are pushed closer to one another. They have closely wound coils, often in a cylindrical or conical shape. Unlike extension springs, compression springs typically have no initial tension when at rest.
On the other hand, extension/tension springs are engineered to absorb and store energy when stretched or subjected to tensile forces, like being pulled apart. These springs have coils that are wound to be stretched along their axis and are usually in a helical shape. Extension/tension springs often have initial tension when relaxed, meaning they are already somewhat extended. In other words, compression springs become shorter under a load, whilst extension springs are extended and become longer under a load.
In terms of usage, compression springs find their application in scenarios in which the primary force is compression. They provide resistance to compressive forces or return objects to their original positions after compression. You’ll find compression springs in various applications, including: automotive suspensions, pens, shock absorbers, and industrial machinery.
In contrast, extension/tension springs excel in situations in which the primary force is tension (or pulling apart). They extend and return to their original state when the force is released. These springs are commonly used in garage doors, trampolines, door locks, and retractable mechanisms like those found in tape measures.
