Compression Springs

Compression Springs are open-coil helical springs wound or constructed to oppose compression along the axis of wind. Helical Compression is the most common metal spring configuration. These coil springs can work independently, though often assembled over a guide rod or fitted inside a hole. When you put a load on a compression coil spring, making it shorter, it pushes back against the load and tries to get back to its original length. Compression springs offer resistance to linear compressing forces (push), and are in fact one of the most efficient energy storage devices available.

The amount of energy stored in a compression spring is determined by the spring's material properties, wire diameter, and number of coils. The spring's rate, or stiffness, is determined by the wire diameter and the number of coils. The spring's rate is the change in force per unit change in length, and it is measured in pounds per inch or newtons per millimeter. The spring's rate can be adjusted by varying the wire diameter or the number of coils.

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Compression Spring Applications

Compression Springs are found in a wide variety of applications ranging from automotive engines and large stamping presses to major appliances and lawn mowers to medical devices, cell phones, electronics and sensitive instrumentation devices. The most basic installation is anywhere requiring a push button. Conical type springs are generally used in applications requiring low solid height and increased resistance to surging.

Stock Compression Springs

Lee Spring stocks millions of compression springs, with thousands of unique design parameters. Lee Spring stock compression springs are available for same day shipment and can be purchased in low or large quantity. Lee Spring stock compression springs are in stock and ready to ship.

Lee Spring offers the following stock compression springs series:

• Free Plating on all Music Wire Stock Springs
• Free Grinding on all Standard Stock Compression Spring
• Free Passivation on 302, 316, & 17-7 Stainless Steel Stock Springs
• Certificate of Compliance on all Stock Springs and Custom Springs
• Guaranteed RoHS Compliance on all Stock Springs
   

Stock Compression Spring Series 

Bantam™ Mini Series
        Free Length: 0.039" - 0.625"
        Ends Not Ground

Instrument Series
        Free Length: 0.039" - 2.087"
        Ends Square, Not Ground

Lite Pressure™ Series
        Free Length: 0.313" - 6"
        Ends Square, Not Ground

Standard Series
        Free Length: 0.173" - 11.417"
        Squared, Ground Ends

Heavy Duty Series
        Free Length: 0.875" - 6"
        Squared, Ground Ends

High Pressure Series
        Free Length: 0.250" - 4"
        Squared, Ground Ends

DIN-Plus Series
        DIN Part 2- Free Length: 0.039" - 2.063"
                                   Ends Square, Not Ground
        DIN Part 1: Free Length: 0.173" - 39.961" 
                                   Squared and Ground Ends

HEFTY™ Die Springs 
        Fit in Hole 0.375" - 2 
        Free Length 

REDUX™ Wave Springs
      Outside Diameter 0.210" - 1.707"
      Free Height: 0.060" - 2" 

LeeP™ Plastic Composite Series
      Free Length: 0.375" - 1.25" 
      Available in 5 Colors - Coded Strengths

MIL SPEC MS
     Free Length: 0.250" - 1.5" 
     Square and Ground 

Custom Compression Springs

Lee Spring offers extensive custom compression spring capabilities and engineering support from design through production. Custom compression springs can be manufactured in a wide range of size and material options. Common compression spring materials include stainless steel, carbon steel, chrome silicon, and music wire.

Lee Spring offers advanced capabilities and a wide variety of options for custom compression spring manufacturing needs such as; advance quality control systems, regulatory expertise including RoHS, REACH and DFARS CAD assisted product design, in-house prototype production services and global supply chain network. Lee Spring is ISO : certified, REACH and RoHS compliant and ITAR Registered.

Lee Spring can manufacture custom compression springs in small or large quantities. Lee Spring can supply for short run R&D projects up to large, long run blanket orders that run over a period of years.

To learn more about material options – click here.
To learn more about coatings and surface treatment options – click here.

Custom Compression Spring Quotes
Request a custom compression spring quote today or contact a Lee Spring Engineering for design help or to answer any technical questions. 

Compression Spring Supply - Global Flexibility 

Lee Spring partners with your business to find solutions that meet your geographic requirements wherever your business takes you in the world. Lee Spring has locations locations around the world ready to assist. Develop prototypes with a Lee Spring Engineering in one part of the world and reduce long run shipping costs by producing parts close to where you need them in another part of the world. This level of global flexibility and selection is just another reason to work with Lee Spring on your next project. 

Compression Spring Design Considerations 

Compression Spring Types & Shapes 
Compression springs are available variety of shapes. Some of the most common compression spring shapes are conventional, conical, hourglass, or convex, barrel, or concave, and reduced end designs. 

Key Compression Spring Parameters

Rate: Spring rate is the change in load per unit deflection in pounds per inch (lbs/in) or Newtons per millimeter (N/mm).

Stress: The dimensions, along with the load and deflection requirements, determine the stresses in the spring. When a compression spring is loaded, the coiled wire is stressed in torsion. The stress is greatest at the surface of the wire; as the spring is deflected, the load varies, causing a range of operating stress. Stress and stress range govern the life of the spring. The wider the operating stress range, the lower the maximum stress must be to obtain comparable life. Relatively high stresses may be used when the operating stress range is narrow or if the spring is subjected to static loads only.

Outside Diameter: The diameter of the cylindrical envelope formed by the outside surface of the coils of a spring.

Hole Diameter: This is a measurement of the space where you would insert a compression spring. It is the diameter of a mating part to a compression spring and often commonly mistaken for a dimension of the spring itself. The hole diameter should be designed larger than your compression spring’s outside diameter factoring tolerance and spring expansion under load.

Rod Diameter: This is a measurement of the rod that goes through the inside of a compression spring. Essentially a mating part, this rod can work as a guide shaft to minimize spring buckling under load. The rod diameter should be designed smaller than your compression spring’s inside diameter factoring tolerance; however, not too small or else it loses ability to minimize spring buckling.

Free Length: The length of a spring when it is not loaded. NOTE: In the case of extension springs, this may include the anchor ends.

Wire Diameter: This is a size measurement of the raw material used to form a spring. Conventional springs are made with round wires that are specified to a diameter. Consult our guide on How to Measure a Compression Spring.

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Solid Height: This is a length dimension of a compression spring at its maximum loaded condition. Effectively, this is the compression spring’s height when all the coils are pressed together.

Spring Set: This is an occurrence when a spring is loaded beyond its material elastic strength. It is a kind of permanent deformation that is noticeable when a spring does not return to its original length after releasing a deflection load. Depending on the application, spring set can be either desirable or undesirable.

Load at Solid Height: This is a measurement of the force required to completely deflect a compression spring to where the coils are fully pressed together. For product designers that want to avoid the occurrence of bottoming out a compression spring, Load at Solid Height is quick reference property to find springs capable of handling an assembly’s maximum operating load.

Resources

How Do Compression Springs Work?

Compression springs store and release energy when subjected to a compressive force. As the spring compresses, it stores energy within its structure. When the force is removed, energy is released and the spring expands to its original length. They are used in various products and applications, from smaller household items to larger industrial machinery, including pens, garage doors and vehicle suspension systems.

Once we understand how compression spring mechanisms work, we can use them in various applications such as shock absorption, vibration dampening, and maintaining contact pressure. This post will explore:

Table of ContentsPrimary Item (H2)

The Basics of Compression Spring Mechanism

Compression springs provide a versatile and efficient way of absorbing compression. The typical design for a compression spring is a helical wire coil spring, giving them their alternative name, compression coil springs. These springs come in various shapes and sizes, including conical compression springs and cylindrical ones, to suit their applications' specific needs.

Elastic Deformation and Hooke's Law

When a compression spring is subjected to a compressive force, its length reduces. This process is called deformation (also known as deflection). However, when the force is removed, it will return to its original length; the ability to return to its original shape is a fundamental part of a compression spring's functionality. Hooke’s Law describes this process, which states that the force is directly proportional to the displacement. This can be written as the equation: F = k * x, where F is the force, k is the spring constant (stiffness), and x is the deflection.

Stress and Strain in Compression Springs

Stress is the force that tries to compress a spring; it is typically measured in Pascals (Pa) or Megapascals (MPa), or pounds per square inch (psi) in the imperial system. 

Strain is the change in length relative to the original length of the material. Strain can be calculated using a simple formula > Strain = change in length/original length of the material.

Spring Constant and Its Significance

The spring constant is a measure of the stiffness or rigidity of a spring. A higher spring constant makes a stiffer spring; this means it requires a higher compression force to shorten the length of the spring (deflection). The ‘spring constant’ concept allows engineers to create specific springs to meet certain performance requirements. It is essential for understanding, designing and predicting the behaviour of springs in various applications.

Compression Spring Design

Several factors must be considered when designing compression springs. Factors include the load requirements, the deflection (deformation) requirements, the material, the number of coils, the spring parameters and stress and deflection limits. Considering the above, engineers can design compression springs that meet specific application requirements and balance these factors with manufacturing costs and feasibility.

Key Design Parameters

Many factors may affect the design of a compression spring, and by considering these, an engineer can produce springs that meet specific requirements while being aware of costs, overall performance, and durability.

Material Selection for Compression Springs

The material properties of a compression spring directly impact its performance as they determine its strength, durability, and resistance to deformation. 

Compression springs can be made from a wide range of materials, including Carbon Steel, Stainless Steel, Chrome Silicon, Chrome Vanadium, Phosphor Bronze, Beryllium Copper, Inconel Alloy, Titanium Alloy, Nitinol (Nickel Titanium) and Plastic (Acetal, Nylon). Material selection is crucial to ensure a spring can provide the required support under compression without exceeding its elastic limit. Other factors to consider when selecting a material include temperature range and corrosion resistance. Engineers conduct material testing to ensure the chosen material meets the requirements of the application.

Compression Spring Calculator

The equation used is: F = k * x, where F is the force, k is the spring constant (stiffness), and x is the deflection of the spring. We can then use two useful formulas to calculate Spring Rate and Load Capacity.

The Spring Rate is the load variation per deflection unit (deformation). We can calculate this using the formula below:

Spring Rate Calculation:
Spring Rate = Force Applied / Deflection of the Spring
*spring rate is measured in newtons per meter (N/m) or pounds of force per inch (lb/in)
*force applied is measured in Newtons (N) or pounds (lb)
*deflection is measured in mm or in

The Load Capacity is the maximum amount of Newtons a spring can withstand before it is at risk of buckling or permanent deformation.

Load Capacity Calculation:
Load Capacity = Spring Rate x Maximum Allowable Compression
*load capacity is measured in Newtons (N)

Forces and Deflection in Compression Springs

When a compression spring is subjected to a load, it experiences forces that cause it to deflect (deform) or change shape. Understanding the relationship between these forces and the spring’s deflection is crucial for designing springs that can efficiently store and release energy while maintaining structural integrity. By understanding these forces and deflections, engineers can design resilient springs that are more appropriate for their intended applications.

Exploring the Force-Displacement Relationship

Hooke’s Law states that the displacement of a compression spring is directly proportional to the applied force, meaning that as the applied force increases, the spring's displacement also increases. This relationship is essential for understanding how compression springs store and release energy.

Load (force)

The force the spring is required to support.

Free length

The length of a spring when no force is applied.

Spring constant

The stiffness or rigidity of a spring.

Wire diameter

A spring wire's diameter (affects strength and flexibility).

Coil diameter

A coil's diameter (influences the space requirements).

Spring Index

This is the ratio of mean coil diameter to wire diameter, which affects stress distribution.

Number of coils

The total number of coils in the spring (affects flexibility and response to load).

Deflection (deformation)

The amount of deformation a spring will experience when the force is applied.

Elastic limit

This refers to the maximum amount of force that a spring can undergo while still being able to return to its original shape.

Solid height

The length of a spring when fully compressed.

Material type

The type of material used to make the spring.

Buckling considerations

A spring may buckle under certain compression levels.

End Conditions

The design of the ends of a spring, e.g. open, closed and squared, closed and ground or double closed ends.

Permanent deformation

The consideration that springs may experience permanent deformation over time.

Equilibrium Position and Solid Height

The equilibrium position of a compression spring is the point at which the spring is at its natural length, neither stretched nor compressed. This point is the benchmark for measuring displacements (deformation) and supports an engineer in assessing how a spring reacts when exposed to compression or force. The solid height of a compression spring is when it is fully compressed; in this state, all of its coils touch one another. Understanding the concepts of equilibrium position and solid height is crucial for designing compression springs that can efficiently store and release energy while maintaining structural integrity.

Spring Rate and Load vs. Deflection

The Spring Rate is the load variation per deflection unit (deformation). A higher spring rate indicates a stiffer spring that can handle a more significant load and will experience less deflection. A lower spring rate means a softer spring with a lower load capacity, which, in turn, will experience more deflection.

Manufacturing Compression Springs

The manufacturing process of compression springs involves a series of steps, including coiling, heat treatment, and surface finishing. Each process ensures the spring’s highest performance, strength, and durability. In this section, we will discuss the various manufacturing processes involved in producing compression springs and the different surface finishes and coatings available to enhance their performance and longevity.

Coiling Process and Variations

The coiling process is a crucial step in the manufacturing of compression springs. This process uses specialised coiling machines, which ensure precise control over the pitch, coil diameter, and number of active coils. During the coiling process, various variations can arise, such as variations in pitch (distance between coils) and diameter. The coiling process, along with subsequent heat treatment and finishing steps, determines the final characteristics and performance of the compression spring.

Heat Treatment for Stress Relief

Heat treatment is a critical step in the manufacturing process of compression springs, as it helps to reduce residual tensile stresses and remove induced stresses caused by the coiling process. This results in improved performance and durability for the spring. There are several methods for heat treatment, including annealing, stress relieving, and spring setting treatment. Appropriate heat treatment is vital to ensuring the performance and longevity of compression springs.

Surface Finish and Coating Options

The surface finish of a compression spring is an essential factor that directly impacts its performance and longevity. The correct surface finish can reduce friction, extend the spring’s fatigue life, and improve its corrosion resistance. Each surface finish and coating option has pros and cons - it is essential to consider the specific requirements of the compression spring application before selecting a finish or coating.

Compressions Spring Examples 

Compression springs are incredibly versatile and have uses in various industries. They are used in automotive suspension systems, industrial machinery, aerospace and aviation, medical devices, consumer electronics, furniture and bedding, toys and games and sports equipment. Their ability to store and release energy efficiently makes them an essential component in many applications.

Automotive Suspension Systems

Compression springs play a key role in automotive suspension systems. They absorb shock and resist compressive forces, ensuring the vehicle’s stability and ease of handling. Compression springs work with other components, such as dampers, to optimise the overall performance and handling of the suspension system.

Industrial Machinery

Compression springs are used in various industrial machinery, providing resistance and absorbing forces to ensure components' smooth operation and movement. They are used in manufacturing, transportation, construction, agriculture, petrochemical, and other industrial sectors. Some examples of industrial machinery that utilise compression springs include construction equipment, agricultural machinery, medical devices and precision instruments.

Factors Impacting Compression Spring Behaviour

The performance of compression springs is affected by various factors, including their mechanical properties, design parameters, and the conditions under which they operate. Engineers may use mathematical models, simulations, and testing to optimise spring designs for specific conditions and load requirements. 

Temperature Effects

The temperature at which a compression spring operates can significantly impact its performance; the spring material may either expand or contract when exposed to different temperature environments. It is also possible for the material properties to change due to heat or cold exposure. 

Fatigue and Spring Life

Fatigue and spring life are critical considerations when designing compression springs, especially when the springs undergo cyclic loading or repeated compression and relaxation. Fatigue refers to cumulative damage that occurs when a material is subjected to repeated loading and unloading cycles, leading to the eventual failure of the material. Understanding fatigue is crucial for predicting compression springs' life expectancy and reliability.

Interestingly, a study titled ‘Stress relief effect on fatigue and relaxation on compression springs’ found that when they reduced heat treatment time (in a 400 °C group), the fatigue limit did not change. This result will differ depending on the materials used; however, it shows that a cost reduction may be viable in this manufacturing process. This shows how engineers can weigh up the pros and cons of certain materials, the intended use of application and the cost involved in production.

Stress Relaxation

When subjected to a constant load over time, stress relaxation happens to materials, including those used in compression springs. It involves a gradual decrease in stress within the material, even though the load remains constant. This is important to consider in applications where compression springs are used for extended periods, as it can affect the spring's overall performance. Choosing materials with low relaxation rates significantly reduces the risk of stress relaxation in springs.

Summary

Compression springs are a highly versatile and efficient way of absorbing force in various industry applications. The manufacturing process involves various materials with multiple properties, and engineers must choose materials appropriate to the spring application. Equilibrium position, solid height and spring rate affect a spring's performance, as does the manufacturing process, including coiling, heat treatment and surface finish.

Many factors affect compression spring behaviour, and these need to be carefully considered, as do precautions in installing, handling and maintaining springs.

If you would like to find out more about the different types of compression springs, you can check out our compression spring information page. We also have a glossary of spring terminology, which can help you better understand various elements and other types of springs.

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