Springs are mechanical components, which are designed to store and release energy when compressed, stretched or twisted. They are typically made of materials like steels or specialized alloys, and are manufactured through processes including winding, heat treatment, grinding, coating and finishing. Springs serve various purposes such as shock absorption, vibration damping, and controlled motion in machinery. Additionally, they are versatile components integral to daily life, enabling smoother rides in automotive suspension, accurate timekeeping in clocks and watches, and comfort and support in furniture.
Some springs are custom-made to suit precise applications, while others are mass-produced for general functions. If your application demands a particular type of spring, it's important to determine the exact kind needed. In this article, we will delve into how springs work, explore the various types of springs and their applications, and consider how to select the right springs for your projects.
Working Principle of Spring
Springs are designed to deform when a force is applied, storing energy in the process. This deformation generates a restorative force that is released once the force is removed, allowing the spring to return to its original shape and size. Hooke's Law explains this behavior.
Hooke's Law is a fundamental principle in physics that describes the relationship between the deformation of an elastic material (particularly a spring) and the force applied to it. It was formulated by the English scientist Robert Hooke in the late 17th century.
Mathematically, Hooke’s Law is expressed as:
F = -kx
The negative sign indicates that the restoring force exerted by the spring is in the opposite direction to the displacement caused by an external force.
“F” is a force applied to the spring.
"k" is the spring constant, which quantifies the stiffness of the spring. In linear springs, "k" depends on factors like wire diameter, coil diameter, and the number of coils. In contrast, in torsion springs, "k" is influenced by the torsion angle (the angle of twist, typically in radians) and the arm length (the distance from the force application point to the axis of torsion).
"x" represents displacement; for linear springs, it's the distance stretched or compressed from the equilibrium position, and for torsion springs, it’s the angle of twist.
Types of Springs And Their Applications
Springs are fundamentally classified into three basic types: mechanical, gas, and air springs. Gas springs utilize compressed sealed gas to generate force, commonly found in automotive tailgates and adjustable chair backs. Air springs, on the other hand, use compressed air to absorb shocks and loads, and are typically used in the suspension systems of automobiles and trucks.
This article will primarily focus on mechanical springs—the most common type found in almost all consumer devices and industrial equipment,which are further divided into three subcategories: helical, disc, and leaf. Let's start with helical springs.
Category One: Helical Springs
Helical springs, also known as coil springs, are typically made using spring coiling machines by winding wire to create a helical shape. These springs are highly elastic and flexible, which allows them to absorb shock and maintain force over a broad range of load conditions.
1. Compression Springs
Compression springs are open-coiled springs with a constant coil diameter and space between the coils. They can only be compressed along their axial direction. To maintain even force distribution and ensure stable assembly, the ends of these springs are often subjected to precision grinding. Typical applications include mattresses, valves, ball-point pens, and weighing machines.
2. Extension Springs
Extension springs are tightly-coiled springs designed to resist stretching or pulling forces. The ends of these springs are usually formed into loops or hooks to facilitate attachment to other components. CNC machining is used to create these complex end shapes, especially for custom, heavy-duty, or special-purpose springs. Common applications include garage doors, weighing machines, and automotive suspensions.
3. Torsion Springs
The ends of a torsion spring are fixed to other components, and when these components rotate around the center of the spring, the spring pulls them back to their initial positions, generating torque or rotational force. This type of spring is used in hinges, counterbalances, door closers, and garage doors.
Spiral springs, also known as clock springs or flat coil springs, are a specific type of torsion spring. They're made by coiling rectangular metal strips into flat spirals and are capable of storing and releasing energy at a constant rate. Due to their ability to continuously release energy, spiral springs are particularly suitable for mechanical watches, toys, and seat recliners.
Category Two: Disk Springs
Disc springs are generally produced through a high-precision stamping process from flat sheets of metal. Their conical shape allows them to be stacked in various configurations to achieve specific force-deflection characteristics. Therefore, they are preferred in applications requiring high force in limited spaces.
1. Belleville Springs
Belleville springs feature a standard conical design with a central opening, thicker at the edges and thinner at the center. Due to their high spring rates and load capacities in a compact configuration, they are commonly used as mechanical tools, valves, clutches, and circuit breakers.
2. Curved Disk Springs
Curved disk springs are also known as crescent washers. They have a curvature that causes them to undergo a predetermined deformation path under axial loads. Such non-linear load characteristics enables them being widely used in regulating components of safety valves and pressure control valves, which require flexible response and progressive control.
3. Slotted Disk Springs
Slotted disk springs are characterized by slots on either their outer or inner diameter, allowing for greater lateral expansion during compression. As compression increases, the stiffness of the spring typically decreases, resulting in a softer response. Additionally, the load response of these springs shows non-linear variations at different stages of compression, making them ideal for applications that demand precise control over force and displacement. These springs are commonly used in automatic transmissions to facilitate smooth gear shifts, and in overload couplers to protect against excessive load by adjusting stiffness dynamically.
4. Wave Disk Springs
Wave disk springs feature an undulating shape with multiple waves per coil. This unique design enables them to absorb a significant amount of axial compression in a very compact form, allowing them to deliver the same force output as traditional helical springs but in a smaller space. Moreover, they offer a progressive load, which means that the force exerted by the spring increases gradually as it compresses. These characteristic is particularly advantageous in applications that require precise load management within compact assemblies, such as valve assemblies, electronic devices, and lightweight machinery.
Category Three: Leaf Springs
Leaf springs are long and narrow plates arranged in layers or stacks, typically manufactured by cutting and then shaping through hot forming or cold bending. Known for their robust construction and ability to handle very heavy loads, leaf springs have been an essential component of vehicle suspension systems for many years. However, with advances in materials and technology, modern suspension systems, such as air suspensions, are beginning to replace traditional leaf spring systems in some applications.
1. Mono-leaf springs
Mono-leaf springs, also known as single-leaf springs, are constructed from a single, thick piece of metal that tapers from the center to the ends. This design allows the spring to be lighter while still being able to handle significant loads. Moreover, they are generally easier and cheaper to manufacture and install. Mono-leaf springs are used in both light and heavy vehicles but are particularly favored in performance vehicles and light commercial vehicles.
2. Multi-leaf Springs
Multi-leaf springs consist of several layers of metal leaves stacked on top of one another, usually graduated in length. Each leaf is designed to support a portion of the load, with the leaves working together to distribute the load more evenly across the spring. Consequently, multi-leaf springs are better equipped to handle heavier loads and offer greater durability than mono-leaf springs. They also exhibit superior shock absorption and load distribution capabilities. These attributes make them commonly used in heavier vehicles such as trucks, vans, and SUVs.
Materials Used to Make Springs
Springs are usually made from metals, though composite materials and rubber are adopted sometimes. Next, we will focus on the commonly used metal materials for making springs.
High Carbon Steel
High carbon steel contains a higher proportion of carbon (typically between 0.6% and 1.5%), which gives it high hardness and strength. This allows it to withstand heavy loads and high pressures. It also has high fatigue resistance and wear resistance, which are crucial for springs that undergo numerous cycles of compression and release. However, it is more brittle and prone to corrosion.
Low-Alloy Steel
Low-alloy steel is a type of steel where the total content of alloying elements is less than 5%. It commonly contains elements such as nickel, chromium, and molybdenum, which enhance mechanical properties such as strength and toughness. This allows springs made from low-alloy steel to withstand greater loads without breaking. Additionally, low-alloy steel offers better corrosion resistance than carbon steel and is more cost-effective than stainless steel.
Stainless Steel
Stainless steel, a high-alloy steel containing at least 10.5% chromium, is ideal for manufacturing springs used in harsh environments exposed to moisture, chemicals, or salt. The addition of other alloying elements like nickel, molybdenum, and manganese enhances its strength, wear resistance, and fatigue resistance. Moreover, stainless steel performs well under both high and low temperatures, making it well-suited for springs operating in environments with variable temperatures.
Nickel Alloys
Nickel alloys possess excellent high-temperature and corrosion resistance, while maintaining good mechanical strength. They are a top choice for manufacturing springs that require high performance in extreme environmental conditions.
Copper Alloys
Copper alloys own excellent electrical and thermal conductivity, as well as corrosion resistance, and are easy to shape. They are commonly used to manufacture springs for applications requiring superior electrical conductivity and corrosion resistance, such as battery contacts and connectors.
Titanium
Titanium is favored for its low density and high strength, but it is particularly valued in the medical field for its biocompatibility. It also can withstand high loads in extreme environments, which makes titanium springs commonly used in high-performance sporting equipment and aerospace components.
When actually making springs, the above metal materials usually need to undergo a series of treatments to enhance their performance and durability:
Cold Drawing: Improves the crystalline structure of the material, enhancing its tensile strength and fatigue resistance.
Heat Treatment:
Quenching and Tempering: A common heat treatment process that involves heating the metal to a specific temperature, then rapidly cooling it (quenching), followed by moderate reheating (tempering). This process enhances the toughness and wear resistance of the metal.
Oil Quenching: Involves cooling the heat-treated metal in oil to improve the spring's fatigue resistance and elasticity.
Bainite Hardening: A special heat treatment process that controls the cooling rate to form a bainitic microstructure, enhancing the material’s strength and toughness.
Surface Treatment: Springs are often treated with zinc, nickel, or chrome plating to prevent oxidation and extend their lifespan. Alternatively, surface quality improvements like sandblasting or polishing are employed to reduce the occurrence of fatigue cracks.
Stress Relief: By moderately heating and then allowing the material to cool naturally, this process effectively eliminates the internal stresses generated during the manufacturing of the springs.
Benefits of Springs
Springs contribute to our daily lives in various ways, bestowing upon us a multitude of conveniences through their functions. These include but are not limited to the following:
Vibration Damping
Vibration damping aims to reduce the intensity and duration of vibrations within a system. For example, in industrial machinery, springs are used to absorb and dissipate the energy from vibrations, minimizing their transmission through the machinery and its supporting structures. This not only prolongs the lifespan of the equipment but also improves safety and comfort for operators by reducing noise levels and mitigating vibration-related fatigue. Furthermore, effective vibration damping through springs ensures more precise operation of industrial machinery.
Shock Absorption
Different from vibration damping focusing on amplitude, shock absorbing specifically aims to mitigate the effects of sudden, extreme impacts such as collisions or rapid changes in velocity. This is particularly valuable in automotive suspension systems, contributing to a smoother ride by absorbing the impacts from bumps and potholes on the road.
Force Provision and Motion Control
Springs can generate restorative forces to provide pushing, pulling, or compressive forces, thereby controlling motion or maintaining balance. For example, in everyday life, springs are used in door closers to provide the controlled force needed to smoothly and securely close doors.
Support and Compensation
Springs can support and compensate for various loads, balancing or adjusting as needed. A common example is in office chairs. As the user shifts their weight or changes the chair’s height, the spring adjusts to maintain comfort and provide ergonomic support, effectively compensating for changes in load and position.
Energy Storage and Release
Springs can store energy through deformation and release it when needed. This allows them to function as devices like batteries for energy storage and release in applications such as mechanical watches and driving toys.
How to Choose Right Spring for Your Application
Choosing the right spring for your application is crucial to ensure optimal performance and durability. Below are some detailed steps and considerations to help you select the most appropriate spring for your needs.
Select the Spring Type
Springs, regardless of coil springs or flat springs, function in one of three scenarios as described below.If you require a spring to release stored energy and generate a pushing motion, a compression spring is likely your best choice. For pulling actions, such as extending or retracting, a tension spring is suitable. And if rotational or radial movement is needed, torsion springs are often the preferred option.
Each type of spring has areas where it is most frequently used due to the specific mechanical properties it offers.For example, extension springs are not self-limiting, since they can be stretched beyond their breaking point, which is different from compression springs being designed with a maximum compression point to prevent spring failure. Extension springs are primarily used in non-critical applications where failure is not a major concern, such as trampolines and garage doors. Torsion springs are the most common type of spring, found in everyday items such as clothespins and clipboards, as well as in more intricate systems like garage doors and vehicle suspensions.
Consider the Application Requirements
In addition to the spring type, the specific requirements for specific applications must also be considered.
1. Force requirements
Firstly, it's crucial to discern the type of load, whether it's static or dynamic. Generally, to withstand dynamic loads, there needs more durable materials or special designs (such as progressive springs) capable of managing force fluctuations.
Secondly, it's essential to determine the maximum force the spring will endure and incorporate a safety factor (usually between 1.2 to 2 times) in force calculations. This ensures the spring can withstand unexpected overloads and prevent failures.
Lastly, Lastly, translate these force requirements into specific spring designs by determining parameters like wire diameter, coil diameter, and number of coils. To enable the spring to withstand greater loads, thicker wire diameters and tighter coil spacings can be selected to enhance the overall strength of the spring.
2. Evaluate Environmental Conditions
For applications that operate at high temperatures, springs made from nickel-based alloys like Inconel 600 or Inconel X-750, which offer outstanding heat resistance, are ideal. In corrosive environments, titanium alloys or stainless steel springs are excellent choices due to their corrosion resistance，additional surface treatments like coatings and bead blasting can further enhance their corrosion resistance and reduce friction. For applications that bear high loads, springs made from materials like silicon steel (e.g., AISI 5160) or chrome-vanadium steel (e.g., AISI 6150), known for their exceptional strength and fatigue resistance, are more commonly used.In scenarios requiring frequent usage, fatigue resistance is a prime factor that should be particularly considered. Materials with high fatigue limits and good elasticity, such as chromium-silicon steel, chromium-vanadium steel, and stainless steel, are prioritized. Alternatively, optimizing spring design by incorporating features like rounded transitions and uniform coil distribution can help enhance fatigue life.
3. Space limitations
The available space will dictate the size of the spring and possibly its configuration. For example, compared to traditional springs, disc springs provide greater force within the same axial space, making them suitable for applications with limited space. When space is constrained in width but not in length, such as in the chassis of trucks and railway carriages, leaf springs are advantageous.
Stock vs. Custom
The biggest advantage of stock springs lies in their immediate availability. You don’t need to wait and can obtain them right away. Additionally, they are generally less expensive than custom springs. However, springs serve as auxiliary components and must meet the specific requirements of various applications. Custom springs provide a precise match and are, therefore, popular in many applications. If opting for custom springs, it's important to choose a reputable manufacturer that adheres to industry standards and best practices. Chiggo is a company known for supplying a wide range of custom springs.
Work with Chiggo for Custom Springs
Springs play a pivotal role in the manufacturing sector. If you are seeking a reliable partner to produce essential springs for your products, Chiggo is your ideal choice! With over a decade of machining expertise, our daily engagement with diverse springs provides us with unparalleled knowledge of their properties. We are committed to helping you achieve your goals by delivering top-notch springs at a price that fits your budget. Contact us today for more information.
