A spring is an elastic device that stores potential energy while at rest, and applies a resistant force when compressed or stretched. Springs are a necessary component in many devices, machines, and systems. Springs are used to store and absorb energy and maintain force or tension in the applications for which they are designed. Some of these applications include: circuit breakers, ballpoint pens, paper clips, solenoid valves, writing instruments, medical devices, electronic lock systems, precision springs in MEMS (micro-electro-mechanical systems), and electronics. Industrial springs can even be used to earthquake-proof foundations for high rise buildings.
Technically speaking, springs are an elastic object that stores mechanical energy. In the manufacturing setting, the term coil springs are often referred simply to as springs. There are many types of springs in design; the common ones include compression springs, torsion springs, and extension springs.
Springs are used in all sorts of industries, including: medicine and healthcare, food service, transportation, electronics, security, nanotechnology, architecture and equipment.
The History of Springs
There is little information recorded about the early history of springs. Much of what we know of its beginnings we have gleaned from artifacts. For example, during the Bronze Age, people invented one of the first spring-based tools, the tweezer. These tweezers consisted of two strips of metal and a small plate brazed between them. Other early spring-based tools include pincer pliers and simple tongs. We also know that, during the Iron Age, King Tut used leaf springs to make his chariots run more smoothly and last longer. In the 1700s, the French also used leaf springs on their carriages.
In 1493, Leonardo da Vinci designed and manufactured a gun with a hammer spring, which allowed people to shoot the gun with one hand. He is credited as the first to make a gun using this spring. Next, in 1680, British physicist Robert Hooke discovered the principle upon which springs work. Known as Hooke’s Law, this states that “the amount of force (F) required to extend or compress a spring by some distance (X) is linearly proportional to the distance, where the constant (k) represents its stiffness.” When you apply pressure, the force develops into stress. The stress then creates deformation, known as stress. The official formula for Hooke’s Law is: F=kX.
Around 80 years later, in 1763, R. Tradwell invented the first coiled spring. Users were thrilled because the coil spring requires far less maintenance than the leaf spring, which had to be lubricated frequently and squeaked loudly.
In 1857, during the height of the Industrial Revolution, the steel coil spring was patented in the United States for use in chair seats. Shortly after, in 1871, a German man named Heinrich Westphal invented the innerspring mattress. Sadly, Westphal never profited from his work and died in poverty.
In 1943, Richard James, a naval engineer, came up with the idea for the Slinky, the coil spring that sells as an inexpensive child’s toy. He got the idea while working on developing springs that could support sensitive ship instruments and stabilize them on high seas. As he worked away, he accidentally knocked a coil off a shelf. The coil, instead of simply falling, walked down a stack of books, across a table and onto the floor, where it recoiled into an upright stack. Betty, his wife, named it “Slinky” for its smooth, graceful movement.
Since then, metalworking and heat-treating technologies have advanced significantly. Spring manufacturing has improved alongside them. Today, springs are available in more shapes and sizes than ever, with greater load resistance and more durable elasticity.
Spring manufacturers fabricate their products using a wide range of wires and metals, including: tempered steel, spring steel, cold spring steel, music wire, stainless steel, magnet wire, hastelloy, molybdenum, titanium, copper, bronze and thermoplastics. The choice of what material to use depends on the application and production method. Spring steel, for example, is a popular spring material, because of its elastic properties and its high yield strength. Manufacturers like using music wire for its uniform strength and inexpensive cost. Stainless steel is a popular choice in the pharmaceutical, food and beverages, and medical industries because of its chemically resistant properties, and its smooth, easy-to-sterilize surface. While the wire spring is most popular, for corrosion resistance and noise reduction, manufacturers will use thermoplastics, if possible. For applications that deal with sudden, significantly heavy loads, manufacturers prefer braided wire material.
Manufacturers make springs using either the cold rolling process or the hot rolling process. In the cold rolling process, the wire that is used can be up to 5/8” in diameter. In hot rolling, manufacturers can coil and fabricate into springs straight bars of steel up to 6” in wire diameter. These are ideal for shock absorption. They can also use lightweight and micro wire, which can be as fine as .01” and .002”, respectively. Manufacturers can form stronger springs using flat and square wire, in addition to round wire, and tubular stock, which is also a popular material. They usually make industrial springs from thick wire, while they make smaller springs from wire that is flexible and thin. Some of these springs are too small to be seen by the naked eye.
One of the methods used to produce spring is by wire forming process, which involves winding wire around a metal blank. This method can also be used to produce other products, such as electrical coils, by utilizing a conductive wire instead of a regular wire. Depending on the metal used in this process, the result would produce a different level of compressibility. One thing to note is that CNC programmable machines are needed to complete the design.
Considerations and Customization
When designing and customizing a spring, manufacturers think about: projected spring rate, projected physical dimensions and projected finished product load. They carefully design the spring’s material, size and function, as the potential energy that a spring stores can depend on these details. To achieve adequate load handling, they’ll calculate the number of active coils. To perfect a custom spring for your application, manufacturers can add things like: surface treatments, coatings, surface hardening, out surface coloring and other treatments for corrosion and wear resistance.
Types of Springs
Springs come in four main styles, which are compression springs, extension springs, torsion springs, and flat springs. Other types include: coil springs, leaf springs, constant force spring, conical springs and gas springs.
Coil springs are also known as helical springs. This category of spring gets its name from the method by which it is produced. The coil spring production process involves winding a spring wire around a cylinder to create a helical shape. For specified applications, these springs can be made from steel or stainless steel. Extension springs, torsion springs, and compression springs are types of coil springs, also known as helical springs.
Compression springs act as a cushion when a downward force works against it. Spring compression provides shock absorption. Two common examples of a compression spring are bed springs and the springs used in suspension transportation systems.
When one hears the word spring, one usually thinks of compression springs since they are the most common type of spring out there. One of the defining features of this type of spring is that it provides resistance force to the pressure of the external load. They are usually made out of metal wires and have various applications in motors. There are many parameters before deciding which compression spring to choose from, including the elasticity, line diameter, coil number, center diameter, and spring coefficient. These variables are used in the calculation of the stiffness of the spring.
Extension springs, on the other hand, do the opposite. These springs elongate and exert resistance when pulled by outward forces on both sides. Most often, you can find them installed in a screen door, where they help keep the doors closed.
The defining feature of this type is that in the absence of load, there is no gap between the ring and the ring of a stretch spring. It has application in medical breathing equipment, mobile control, shock absorber, pumps, and other mechanical components. Similar to the previous springs, the materials used to create such a spring would be highly dependent upon its usage, therefore it is suggested to first understand what the end-user is looking for. The necessary parameters to consider would be the free length, control diameter, wire size, material, number of cycles, the form of the end, load in the hook, load rate, and maximum stretch length.
Torsion springs exert pressure along a circular arc-shaped path, providing a twisting force known as torque. A familiar application that utilizes spring torsion spring is a mousetrap. Spring torsion can also be used with doors and windows.
The torsion spring is a variant of the spiral spring. What differentiates this type of spring from compression spring is the fact that they provide resistance to rotating external forces. The ends of this spring are usually attached to other components and will resist when external forces rotate around the center of the spring. It has applications in many fields, such as computer, electronics, automotive, and other mechanical industries. The material used to create it would be different depending on the usage, therefore it is advised to consult with an expert.
There are some springs that are not fabricated with coiled wire. Flat springs are one of them. Flat springs are instead made from flattened strips of plastic or metal, fabricated with a specific curvature. This curvature makes them capable of shock absorption and resistance.
Leaf springs are a type of flat spring that consist of multiple layers of tempered metal strips. These springs are common in the automotive industry and can be found in heavy vehicles such as trucks and vans.
Constant Force Spring
The combination of a flat spring and a coil spring is known as a constant force spring. It consists of a long strip of sheet metal that retains its coiled shape after it has been wound, coiled, and heat treated. Constant force springs are ideal for long spring extensions, as they provide a consistent amount of kinetic energy as they coil and recoil. Applications where constant force springs can be found include: gardening equipment, fitness equipment, toys, and electric motors.
Also known as tapered springs, after their shape, or conical compression springs, conical springs are designed to provide a near constant spring rate while under compression. Under maximum compression, the coils of a conical spring nest inside one another, creating a flat profile. By their nature, tapered springs offer greater stability and less load deflection. Usually, they’re used as electrical contacts and in push buttons. For this reason, they’re typically made from copper or stainless steel, which provide heat and corrosion resistance.
A gas spring is a spring that uses compressed gas instead of elastic deformation to work. The compressed gas is stored inside a closed container that is sealed by a sliding piston. There, it pneumatically stores potential energy and is able to withstand any external force that is applied parallel to the piston shaft. Gas springs are found in automobiles, office chairs and a variety of aerospace, medical and furniture applications. Also, especially large gas springs are used in industrial manufacturing equipment, like presses.
Advantages of Springs
Springs offer several advantages over other mechanisms that serve similar functions. One primary function of springs is their ability to store mechanical energy when deformed and release it when the force is removed, making them ideal for applications like shock absorption, suspension systems, and energy storage. While other mechanisms such as rubber or elastomer components can also absorb shock, they may not provide the same level of energy storage or withstand repetitive stress over an extended period.
Compared to rigid mechanical linkages, springs provide a more forgiving and flexible response to varying loads and forces, preventing damage to the system during sudden impacts or heavy vibrations. In contrast, rigid linkages may transfer excessive forces to connected components, leading to potential failures or reduced durability.
Another area where springs outperform other mechanisms is in their versatility and adjustability. By selecting different materials, wire diameters, and coil configurations, the spring’s stiffness, damping, and load-bearing capacity can be easily tailored to suit specific requirements. This adaptability is challenging to achieve with fixed or solid components.
Furthermore, springs often have a simpler design and require less maintenance than complex mechanisms like hydraulic systems or pneumatic cylinders. Their reliability and cost-effectiveness make them more practical for a wide range of applications.
In summary, springs excel in areas where other mechanisms fall short due to their superior energy storage and release capabilities, flexibility to adapt to varying loads, simplicity of design, and overall cost-effectiveness. While other mechanisms may serve similar functions in specific scenarios, springs remain a fundamental and widely used solution for various mechanical challenges.
Various accessories and hardware are used in conjunction with springs to enhance their performance and functionality in specific applications. Let’s discuss some of these components:
Spring mounts or seats are used to securely position the spring within a mechanical system. They provide a stable and consistent point of contact for the spring, ensuring proper alignment and preventing lateral movement during operation. Spring mounts also help distribute the load and minimize stress concentrations, leading to improved durability and performance.
Coil Spring Isolators
Coil spring isolators, also known as spring isolators or shock mounts, are used to isolate the spring from the surrounding structure or components. They reduce the transmission of vibrations and noise, making them suitable for applications like automotive suspension systems and industrial machinery, where damping unwanted oscillations is crucial.
Felt inserts are used between the spring coils to reduce friction and noise during compression and extension. They provide a smooth surface for the coils to slide against, preventing metal-on-metal contact and potential wear.
Ball studs are used to create a pivoting connection between the spring and other components, allowing for angular movement and articulation. This is common in applications like automotive suspension systems, where the wheels need to move up and down while maintaining a stable connection to the chassis.
End fittings are components attached to the ends of the spring to facilitate its connection to the surrounding structure. These fittings could include hooks, loops, or threaded ends, depending on the specific application.
To determine which accessories or hardware are needed for a particular application, several factors must be considered. The intended use, load requirements, environmental conditions, and desired performance characteristics are crucial aspects. Consulting with an engineering expert or a specialist in springs and their applications can help in selecting the appropriate accessories for optimal functionality and longevity of the spring system. Additionally, testing and analysis of the system under various conditions can aid in fine-tuning the choice of accessories to meet specific needs and ensure reliable performance.
Proper Care for Springs
Proper care for springs is essential to optimize their performance and extend their useful life. Regular inspection is crucial, as it allows for the early detection of any signs of wear, damage, or corrosion. Addressing these issues promptly can prevent further deterioration and potential failure. Lubrication is another vital aspect of spring care, as it reduces friction between the coils, minimizing wear and ensuring smooth operation, especially in dynamic applications. Avoiding overloading the springs beyond their specified capacity is crucial, as excessive loads can lead to premature failure. In corrosive environments, protective coatings or materials should be used to safeguard against corrosion and maintain the spring’s structural integrity. Temperature considerations are also important, as extreme temperatures can impact the spring material’s properties. Additionally, proper installation procedures should be followed to prevent misalignment and stress concentration, which could compromise the spring’s performance. Furthermore, optimal design, tailored to the specific application, is crucial for achieving reliable and efficient operation. Finally, storing springs in a clean, dry environment when not in use helps prevent contamination and preserves their original properties. By following these care guidelines, users can ensure that their springs perform optimally, have an extended lifespan, and avoid costly replacements or downtime resulting from premature spring failures.
Standards for Springs
Various industry and governmental agencies play a critical role in setting standards for springs, ensuring their safety, performance, and compatibility across different applications. Some of the prominent organizations involved in establishing standards for springs include SAE (Society of Automotive Engineers), ASTM International (formerly known as American Society for Testing and Materials), ISO (International Organization for Standardization), and AISI (American Iron and Steel Institute). We discuss the role that each of these organizations play regarding springs in greater detail below.
SAE establishes standards specifically focused on automotive engineering and technology. They set guidelines for various spring applications in vehicles, such as suspension systems, engine components, and braking systems, ensuring that springs meet rigorous safety and performance criteria for automotive use.
ASTM develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services. Their standards cover spring materials, manufacturing processes, and testing procedures to ensure that springs meet quality, performance, and safety requirements across industries.
ISO is an international standard-setting body that develops and publishes standards to promote international trade and ensure product quality, safety, and efficiency. ISO standards related to springs cover various aspects, including dimensions, materials, testing methods, and performance requirements, ensuring global compatibility and interchangeability.
AISI focuses on standards related to iron and steel, including those used in spring manufacturing. Their standards ensure that spring materials meet specific strength, ductility, and other mechanical properties necessary for optimal spring performance.
The impact of these agencies on the production and use of springs is substantial. Compliance with these standards provides manufacturers and users with clear guidelines for material selection, manufacturing processes, and testing methods. Adhering to these standards ensures that springs are safe, reliable, and consistent, regardless of the application or industry. Meeting the established standards also promotes compatibility and interchangeability, allowing springs from different manufacturers to be used interchangeably, reducing costs and facilitating efficient supply chains.
Failure to meet these standards can have serious consequences. Non-compliant springs may not perform as expected, leading to safety hazards, increased risk of failure, and potential damage to equipment or systems. In industries like automotive and aerospace, where precision and reliability are critical, using non-compliant springs may lead to accidents and legal liabilities.
On the other hand, complying with these standards offers numerous benefits. For manufacturers, it enhances the credibility and marketability of their products, fostering customer trust and satisfaction. For users, it ensures that springs meet specific quality and performance requirements, leading to improved safety and overall system reliability. Additionally, compliance with international standards facilitates global trade and promotes product interoperability, making it easier for companies to operate on an international scale.
In conclusion, the standards set by organizations like SAE, ASTM, ISO, and AISI have a significant impact on the production and use of springs. Complying with these standards ensures safety, reliability, and consistency, while non-compliance can lead to potential hazards and legal repercussions. Following industry standards is beneficial for both manufacturers and users, fostering trust, reliability, and efficiency in the spring industry.
Things to Consider Regarding Springs
Springs are simple but mighty. For the best results, you need to work with an experienced and reliable manufacturer who is in tune with your needs. To help you get started, we put together a comprehensive list of industry leaders that can meet a wide range of requirements. To help you narrow down your choices, we offer this advice: Before doing anything else, put together a list of your specifications, requirements and any questions. Make sure to include: your application, your spring’s projected load weight, the physical dimensions of the product your spring(s) will be supporting, details about the environment (corrosive, outdoor exposure, sterile, etc.), your budget, your deadline and your delivery preferences.
Once you have your list ready, pick out three or four of the spring manufacturers we have listed here that you feel best match your specifications. Then, reach out to each of them individually. Discuss your application at length. Leave no stone unturned; a quality manufacturer will be happy to make sure you understand one another well. Once you’ve done that, compare and contrast your interactions. Which manufacturer displayed the best customer service? Which one had the capabilities to best serve you? The right manufacturer will be in the sweet spot, offering both superior manufacturing capabilities and superior customer service. We’re confident that the manufacturer is in this group. Good luck!
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