The Three Main Types of Coil Springs

What type of spring should I use?

When it comes to coil springs, understanding the differences between Compression, Extension, and Torsion springs is crucial for selecting the right type for your needs. Each of these springs performs unique functions and operates differently under various forces. Whether you are an engineer designing complex machinery, a maker working on innovative projects, or simply someone seeking a reliable spring for a specific application, knowing how to choose the right spring can make all the difference in performance and longevity. 

Selecting the appropriate spring for your application involves understanding the mechanics of each spring type and how they respond to different forces. For instance, compression springs are ideal for applications requiring shock absorption and force maintenance, while extension springs are perfect for situations needing tension and a return to original length after stretching. Torsion springs, on the other hand, are essential for applications that need rotational force.

The process of finding the right spring can be daunting due to the variety of specifications and parameters involved. This is where Acxess Spring's tools come into play. The Online Spring Force Tester helps you measure the force exerted by your spring with precision, while Spring Creator 5.0 allows you to design custom springs tailored to your specific needs. These tools provide real-time feedback and ensure your springs meet all necessary specifications, making the selection and design process seamless and accurate.

Compression Springs

Compression springs are the most popular type of springs. These helical springs are designed to store and release energy efficiently. When a load or force is applied to a compression spring, the coils compress, storing potential energy. Once the force is removed, the spring returns to its original shape, releasing the stored energy in a controlled manner. This action is fundamental in applications where shock absorption or maintaining a consistent force between two surfaces is required.

Characteristics of Compression Springs

Compression springs possess several defining characteristics that make them uniquely suited for their diverse range of applications. These characteristics include:

1. Helical Shape: Compression springs are typically constructed in a helical shape, allowing them to compress and expand along the axis of the coil. This shape is crucial for storing energy efficiently and returning to the original form when the load is removed.
2. Material: They are made from various materials, including stainless steel ASTM A313, music wire ASTM A 228, and chrome silicon ASTM A 401.. The choice of material depends on the application's requirements, such as corrosion resistance, strength, and flexibility.
3. Wire Diameter: The wire diameter of a compression spring can vary significantly, typically ranging from 0.006 inches to 1.250 inches. The wire diameter influences the spring's strength, stiffness, and load-bearing capacity.
4. Outer Diameter: The outer diameter of the spring affects how much space it occupies and its fit within the application. It is essential to match the spring's outer diameter to the application's dimensions for optimal performance. It greatly impacts the spring constant k. The smaller the outer diameter, the stronger the spring is but this comes with a loss of travel deflection. The Bigger the outer diameter the weaker the spring constant k is with the benefit of more travel distance. 
5. Coil Count: The number of coils in a compression spring impacts its deflection and load-bearing characteristics. Springs with more coils generally offer greater deflection and lower spring rates, while springs with fewer coils provide higher spring rates and less deflection.
6. Free Length: The free length of a compression spring is its length when not under any load. This characteristic is crucial for determining how much the spring will compress under a given load and how it fits within the assembly with the compression springs loaded height.
7. Spring Rate: The spring rate, spring constant or stiffness, is a measure of how much force is required to compress the spring by a unit length (usually inches or millimeters). It is an essential factor in determining the spring's performance under load and its suitability for specific applications.
8. Pitch: The pitch of a compression spring refers to the distance between each coil. Springs with a larger pitch will have more space between coils, allowing for greater compression. Conversely, springs with a smaller pitch will be stifferweaker and compress less.
9. Load Capacity: The load capacity of a compression spring is determined by its material type, mean diameter, wire diameter, and coil count. It specifies the maximum load the spring can handle without permanent deformation or failure.
10. Deflection: Deflection, or travel, is the amount a spring compresses under a load. It is a critical parameter for applications requiring precise distance movement or force control. The maximum deflection a spring can achieve without damage is known as its max. travel.
11. Durability and Fatigue Resistance: Compression springs must be designed to withstand repeated compressions cycles and expansions without losing their mechanical properties. Material selection and spring design play vital roles in ensuring durability and resistance to fatigue.

By understanding these characteristics, you can better select or design compression springs that meet your application's specific needs. 

Applications of Compression Springs

Compression springs are used in a myriad of applications across various industries due to their versatility and efficiency in energy storage and release. In the automotive industry, compression springs are crucial components in suspension systems, providing the necessary shock absorption to ensure a smooth ride. They are also found in engine components, where they help maintain tension and prevent mechanical failure. In the medical field, compression springs are used in devices such as inhalers, ensuring consistent delivery of medication. They are also found in surgical instruments, providing the precision and reliability needed in critical procedures.

In everyday consumer products, compression springs are ubiquitous. They are found in pens, enabling the retractable mechanism that allows the pen to click open and closed. Household items such as battery compartments, push-button devices, and various types of latches and catches also rely on the dependable action of compression springs. In electronics, they are used in connectors and switches, ensuring reliable contact and operation.

Industrial machinery often incorporates compression springs to maintain force and tension in belts, chains, and other moving parts, ensuring the smooth operation of the equipment. They are also integral to valves and pumps, where they help regulate flow and pressure. In aerospace applications, compression springs must meet stringent standards for reliability and performance, as they are used in critical components such as landing gear, control systems, and actuators.

Compression springs are also essential in construction and agricultural equipment, where they provide the necessary force to operate tools and machinery effectively. In recreational equipment like trampolines and exercise machines, compression springs provide the necessary resistance and energy return to enhance performance and safety.

Extension Springs

Also known as tension or expansion springs, extension springs are tightly wound coils that create tension when a load or force is applied to their ends, causing them to extend. These springs usually feature hooks, loops, or end coils, which are often the weakest points. In high-force applications, replacing hooks with bolts can prevent bending or breaking, thereby increasing the spring's durability and reliability. Extension springs are used in devices where a force pulls apart the spring from its original length, such as trampolines, push and pull levers, rocking horses, and screen doors. The primary function of an extension spring is to provide extended force when stretched and to return to its original position when the force is removed. 

Torsion Springs

Characteristics of Extension Springs

Extension springs are uniquely suited for a wide range of applications due to their defining characteristics. These include:

1. Helical Shape: Extension springs are typically designed in a tightly wound helical form. This structure enables them to efficiently store energy when stretched and return to their original length once the force is removed.
2. Material: These springs can be crafted from various materials, such as stainless steel, music wire, and chrome silicon. The material choice is determined by the application’s requirements, including factors like corrosion resistance, strength, and flexibility.
3. Wire Diameter: The wire diameter of an extension spring can vary significantly, affecting its strength, stiffness, and load-bearing capacity. Thicker wires offer greater force and durability, whereas thinner wires provide more flexibility.
4. Outer Diameter: The outer diameter impacts how much space the spring occupies and its fit within the application. Matching the outer diameter to the application's dimensions is essential for optimal performance.
5. Coil Count: The number of coils in an extension spring influences its extension capabilities and the amount of force it can generate. Springs with more coils typically offer greater extension and flexibility, while those with fewer coils provide higher tension and less deflection.
6. Free Length: The free length refers to the spring's length when it is not under any load. This characteristic is critical for determining how much the spring will extend under a given load and how it fits within the assembly.
7. Spring Rate: Also known as spring constant k or stiffness, the spring rate measures how much force is required to extend the spring by a unit length (in inches or millimeters). It is a crucial factor in determining the spring's performance under load and its suitability for specific applications.
8. Hooks and Loops: Extension springs usually have hooks, loops, or end coils that allow them to attach to other components. These ends are often the weakest points of the spring, and in high-force applications, they may be reinforced or replaced with more robust attachment methods, such as bolts.
9. Load Capacity: The load capacity of an extension spring is determined by its material, wire diameter, mean diameter and coil count. It specifies the maximum load the spring can handle without permanent deformation or failure.
10. Deflection: Deflection, or travel, refers to how much an extension spring extends under a load. This is a critical parameter for applications requiring precise movement or force control. The maximum deflection a spring can achieve without damage is known as its maximum travel.
11. Durability and Fatigue Resistance: Extension springs must be designed to endure repeated stretching and returning without losing their mechanical properties. The selection of materials and spring design are vital for ensuring durability and resistance to fatigue.

By understanding these characteristics, you can better select or design extension springs to meet your application's specific needs. Whether your requirements include high-load applications, precise force control, or frequent cycling, the right combination of these characteristics will ensure your extension spring performs flawlessly.

Applications of Extension Springs

Extension springs are utilized in a myriad of applications across various industries due to their ability to provide precise tension and return to their original length after being stretched. In the automotive industry, extension springs are used in mechanisms such as throttle return springs, where they ensure that the throttle valve closes properly when not in use, and in brake assemblies, providing the necessary tension for brake components to function correctly. In household appliances, they are commonly found in items like garage door assemblies, where they counterbalance the weight of the door, making it easier to open and close. Screen doors also rely on extension springs to ensure they close automatically and securely after being opened.

In the medical field, extension springs are essential components in devices such as surgical tools and medical instruments, providing the necessary tension for precise and reliable operation. They are also used in physical therapy equipment, where they provide adjustable resistance for exercises and rehabilitation.

In consumer products, extension springs are found in items such as trampolines, where they provide the bounce and tension required for safe and enjoyable use. They are also used in toys, exercise equipment, and various types of machinery that require controlled motion and tension.

Industrial applications of extension springs include use in machinery that requires components to return to their original position after being moved or actuated. This includes applications in conveyor systems, manufacturing equipment, and agricultural machinery, where reliable tension and return capabilities are essential for smooth operation.

Torsion Springs

Torsion springs, or torque springs, perform a rotational force motion when a load or force is applied. These wire springs twist to store energy and release it when the force is removed, producing torque rather in a radial linear fashion.than a linear load. This makes them suitable for applications requiring radial force, such as clocks, watches, clips, and trailer ramps. The unique functionality of torsion springs allows them to provide a consistent rotational force, which is essential in various mechanical devices.

Characteristics of Torsion Springs

The free angleposition is the angle between the legs when the spring is in its unloaded state. This characteristic is crucial for determining the initial angular position and range of motion in the application.Torsion springs have several defining features that make them ideal for a wide range of applications. These features include:

1. Helical Shape: Torsion springs are typically designed in a helical configuration, allowing them to twist along the coil's axis. This design enables efficient energy storage and release through rotational motion.
2. Material: These springs are made from various materials, including stainless steel, music wire, and chrome silicon. The material choice depends on the application's requirements, such as corrosion resistance, strength, and flexibility.
3. Wire Diameter: The wire diameter of a torsion spring can vary significantly, affecting its strength, stiffness, and torque capacity. Thicker wires offer greater torque and durability, while thinner wires provide more flexibility.
4. Leg Length and Shape: Torsion springs have legs or arms extending from the coil ends. The length and shape of these legs can be customized to fit specific applications, providing necessary leverage and attachment points.
5. Outer Diameter: The outer diameter impacts how much space the spring occupies and its fit within the application. Matching the spring's outer diameter to the application's dimensions is essential for optimal performance.
6. Coil Count: The number of coils in a torsion spring influences its torque and rotational capabilities. Springs with more coils generally offer greater torque and flexibility, while those with fewer coils provide higher stiffness and less rotation.
7. Free Position: The free angleposition is the angle between the legs when the spring is in its unloaded state. This characteristic is crucial for determining the initial angular position and range of motion in the application.
8. Spring Rate: Also known as spring constant k, the spring rate per degree measures the torque required to twist the spring by a one degree of movement.  unit angle (degrees or radians). This is essential for determining the spring's performance under load and its suitability for specific applications.
9. Maximum Torque: The maximum torque capacity is determined by the material, wire diameter, mean diameter and coil count. It specifies the maximum torque the spring can handle without permanent deformation or failure.
10. Durability and Fatigue Resistance: Torsion springs must withstand repeated twisting and returning without losing their mechanical properties. Material selection and spring design are crucial for ensuring durability and resistance to fatigue.
11. Leg Configuration: The legs can be configured in various ways, such as straight, bent, or hooked, depending on the application. This flexibility in design allows for customized solutions to fit specific needs.
12. Maximum Deflection: Maximum Deflection refers to the angular displacement from the unloaded to the loaded position. The maximum angular deflection a spring can achieve without damage is known as its working deflection, critical for applications requiring precise angular movement.

By understanding these characteristics, you can better select or design torsion springs that meet your application's specific needs.

Applications of Torsion Springs

In the automotive industry, torsion springs are integral to vehicle suspensions, where they help stabilize and support the vehicle's weight. They are also used in trunk and hood mechanisms to assist in smooth opening and closing. In the aerospace industry, torsion springs are employed in aircraft controls and landing gear mechanisms, where precise rotational force is critical for safe operation.

In consumer products, torsion springs are commonly found in clothespins, where they provide the necessary force to hold the pin closed. They are also used in mousetraps, where the spring's rotational force triggers the trap. In the construction industry, torsion springs are essential components of garage doors, providing the counterbalance needed for easy lifting and lowering. Additionally, torsion springs are used in agricultural equipment, such as balers and harvesters, to control various moving parts.

In the medical field, torsion springs are utilized in surgical instruments and devices that require precise control and consistent force. They are also found in devices such as inhalers and insulin pens, where reliable and controlled force is crucial for accurate medication delivery.

The versatility of torsion springs extends to electronics, where they are used in switches and connectors to ensure consistent contact and operation. Their ability to provide consistent torque makes them indispensable in many applications requiring controlled rotational force and stability.