5 Must-Have Features in a Spring Flat Steel

31 Mar.,2025

 

Types of Springs: Understanding Their Uses, Materials, and Process

There are several types of springs used in different capacities. Generally, there are three main categories, and each category has its subcategories. Below are the properties of the different spring types and their applications.

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Category One: Helical Springs

Helical springs have a general helix shape (hence the name) but different cross-sections. They are the most common types of springs in rapid prototyping and are widely applicable in product manufacturing. Below are the different types of helical springs.

Compression Springs

Compression springs are open coiled springs with a constant diameter and space between each coil. The springs are compressible only one way as they resist axial compression. These spring types are widely applicable in product manufacturing, such as valves and suspension.

Extension Springs

Extension springs are closed compression springs. They function by elongating during tension and storing energy. When on tension removal, the mechanical spring returns to its original shape dissipating the energy. Extension springs are an important part of garage doors, pull levers, jaw pliers, and weighing machines.

Torsion Springs

A torsion spring is attached to two components horizontally or vertically using their two ends. They function by storing and releasing rotational energy. The tighter the winding, the more energy the spring stores and releases on load removal. They are applicable in garage doors, watches, etc.

Spiral Springs

Spiral springs are rectangular metal strips made into a flat spiral that can store and release a reasonable amount of energy at a constant rate. Due to the constant release of energy, they are applicable in making mechanical watches, seat recliners, toys, etc.

Category Two: Leaf Springs

These spring types are from rectangular metal plates or leave bolted, clamped, and applicable in shock absorption in heavy vehicles. Below are the different leaf springs types.

Elliptical Leaf Spring

Elliptical leaf spring comprises two stacked, bolted, and clamped leaves with semi-elliptical shapes connected in opposite directions. Although they have opposite directions, there is no need for spring shackles due to the leaf’s subjection to the same amount of elongation on compression. These springs were important in old cars where car manufacturers attached them to the axle and frame. However, they are not much important nowadays.

Semi Elliptical Leaf Spring

Semi elliptical leaf spring comes from steel leaves having the same width and thickness but different lengths. The longest/uppermost leave is the master leaf. They are the most popular leaf spring in automobiles as they require less maintenance and have a long life.

Semi elliptical leaf springs have an end fixed rigidly to the automobile frame and the other to the shackles. Therefore, the length varies when driving in rough terrains, aiding in shock absorption.

Quarter Elliptical Leaf Spring

Like the elliptical leaf spring, the quarter elliptical leaf spring is olden. Also known as the cantilever type of leaf spring, it has one end fixed on the frame side member using a U-clamp or I-bolt and the other freely connected to the axle. Therefore, when the front axle beams experience shocks, the leaves can easily straighten and absorb the shock.

Three-Quarter Elliptical Leaf Spring

This leaf spring is a combination of the quarter elliptical spring and semi-elliptical spring. On the one hand, the semi-elliptical ends are attached to the vehicle frame and the quarter elliptical spring. On the other hand, the free end of the quarter elliptical spring is then attached to the vehicle frame using an I-bolt.

Transverse Leaf Spring

These are semi-elliptical leaf springs mounted transversely along a vehicle width. In this arrangement, the longest leaf is at the bottom while the mid-portion is fixed to the frame using a U-bolt. Transverse leaf springs lead to rolling. Therefore, they have limited use in the automobile industry.

Category Three: Disk Springs

Disk springs are springs with conical shapes and flexible effects. Consequently, they are applicable in limited space. Below are the types of disk springs.

Belleville Disk Spring

Belleville disk spring or coned-shaped disk spring has a cupped construction. Therefore, they don’t lie flat. They can compress and handle heavy loads. Therefore, they are applicable to products used in high-stress conditions.

Curved Disk Spring

Curved disk springs or crescent washers function by applying light pressure to the mating pair. Therefore, they can resist loosening due to vibration. They are applicable in products that use threaded bolts, fasteners, screws, and nuts in machines which high and constant vibration.

Slotted Disk Spring

Slotted disk springs have slots on the outer and inner diameter. Therefore, they reduce spring load and increase deflection. They are widely applicable in automatic transmissions, clutches, and overload couplings.

Wave Disk Springs

Wave disk springs look like architectural projects with their multiple waves per turn. Consequently, they are applicable in predictable loading as they can act as a cushion by absorbing stress when compressed axially.

Springs are made using a process of winding, heat treating, grinding, coating, and finishing option. The process is straightforward, although there are few variations depending on the types of springs.

1. Winding

The operator feeds the spring wire into a CNC machining or mechanical spring machine, straightening it. It then coils, forms, or bends the straightened wire to the desired shape. These processes can also be individual or in combination.

-Coiling involves using a spring coiler or CNC spring coiler machine to coil the straightened wire according to the desired coil. Coiling is applicable in making compression, extension, and torsion springs.
-Forming involves using a spring coiler or CNC spring former, which uses several bends, hoops, and radii to create several spring shapes. Forming is applicable in making extension springs, torsion springs, and wire forms
-Bending involves using a CNC wire bender to bend the straightened wire to several shapes. Hence, it is applicable in making wire forms.

2. Heat Treating

Heat treating the formed spring makes it undergo stress relieving process. Therefore, it can easily bounce back when you subject it to stress. It involves heating the spring to a specific temperature for a particular time, depending on the type and amount of material.

Heat treating is repeated depending on the type of material and the manufacturing process after which cooling occurs.

3. Grinding

Grinding involves using a grinder to ground the spring’s end flat. Therefore, it will stand up straight when oriented vertically.

4. Coating and Finishing

Coating and finishing are important in improving the aesthetic and functional properties of the spring. For example, electroplating with copper makes the spring conductive, and powder coating will improve its aesthetic value. Finishing options include shot peening (cold-worked springs), plating, powder coating, and anodizing.

Spring failure can lead to machine damage, an increase in maintenance cost, and subsequently, loss of trust in a product that depends on mechanical springs. Therefore, you should try and reduce spring failure. The best way to do that is to understand the causes. Below are the causes and solutions to spring failure.

1. Spring Stress

Spring stress occurs when you expose the spring to a force its design cannot handle. Therefore, leading to spring breaking. You can solve this issue by reducing the amount of force to what the design can handle or making a spring designed to meet such stress. You can make such a spring by using the right material or optimizing heat treatment.

2. Wrong Material Choice

The type of materials used for making the spring can determine the properties of the spring. For example, springs made from stainless steel and copper have high corrosion resistance. Therefore, using another set of materials would be wrong if you desire such property. You can avoid this by learning about the different materials used in making springs.

3. Poor or Incorrect Finish

Finishing options such as powder coating, anodizing, etc., help improve the spring’s aesthetic or functional properties. For example, you can use anodizing to improve the corrosion resistance of the spring. Therefore, applying such finishing poorly or not applying it on a spring that needs it can make it susceptible to corrosion leading to failure in harsh or caustic conditions.

4. Undefined Working Temperature

The spring must be suitable for the operating temperature. You can improve the spring’s heat resistance by choosing a material with the property, subjecting it to heat treatment, or using a finishing option.

5. Inferior Manufacturing Processes

Making springs must be with quality in mind. This will determine its functions and aesthetic appeal. Common examples of the machining operation used include CNC machining. Manufacturers should properly scrutinize the process and ensure that tooling is geared towards precision, reducing spring failure.

Spring (device) - Wikipedia

Elastic object that stores mechanical energy

A spring is a device consisting of an elastic but largely rigid material (typically metal) bent or molded into a form (especially a coil) that can return into shape after being compressed or extended.[1] Springs can store energy when compressed. In everyday use, the term most often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel. An example of a non-metallic spring is the bow, made traditionally of flexible yew wood, which when drawn stores energy to propel an arrow.

When a conventional spring, without stiffness variability features, is compressed or stretched from its resting position, it exerts an opposing force approximately proportional to its change in length (this approximation breaks down for larger deflections). The rate or spring constant of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve. An extension or compression spring's rate is expressed in units of force divided by distance, for example or N/m or lbf/in. A torsion spring is a spring that works by twisting; when it is twisted about its axis by an angle, it produces a torque proportional to the angle. A torsion spring's rate is in units of torque divided by angle, such as N·m/rad or ft·lbf/degree. The inverse of spring rate is compliance, that is: if a spring has a rate of 10 N/mm, it has a compliance of 0.1 mm/N. The stiffness (or rate) of springs in parallel is additive, as is the compliance of springs in series.

Springs are made from a variety of elastic materials, the most common being spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after manufacture. Some non-ferrous metals are also used, including phosphor bronze and titanium for parts requiring corrosion resistance, and low-resistance beryllium copper for springs carrying electric current.

History

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Simple non-coiled springs have been used throughout human history, e.g. the bow (and arrow). In the Bronze Age more sophisticated spring devices were used, as shown by the spread of tweezers in many cultures. Ctesibius of Alexandria developed a method for making springs out of an alloy of bronze with an increased proportion of tin, hardened by hammering after it was cast.

Coiled springs appeared early in the 15th century,[2] in door locks.[3] The first spring powered-clocks appeared in that century[3][4][5] and evolved into the first large watches by the 16th century.

In British physicist Robert Hooke postulated Hooke's law, which states that the force a spring exerts is proportional to its extension.

On March 8, , John Evans, Founder of John Evans' Sons, Incorporated, opened his business in New Haven, Connecticut, manufacturing flat springs for carriages and other vehicles, as well as the machinery to manufacture the springs. Evans was a Welsh blacksmith and springmaker who emigrated to the United States in , John Evans' Sons became "America's oldest springmaker" which continues to operate today.[6]

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Types

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Classification

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Springs can be classified depending on how the load force is applied to them:

Tension/extension spring
The spring is designed to operate with a tension load, so the spring stretches as the load is applied to it.
Compression spring
Designed to operate with a compression load, so the spring gets shorter as the load is applied to it.
Torsion spring
Unlike the above types in which the load is an axial force, the load applied to a torsion spring is a torque or twisting force, and the end of the spring rotates through an angle as the load is applied.
Constant spring
Supported load remains the same throughout deflection cycle[7]
Variable spring
Resistance of the coil to load varies during compression[8]
Variable stiffness spring
Resistance of the coil to load can be dynamically varied for example by the control system, some types of these springs also vary their length thereby providing actuation capability as well [9]

They can also be classified based on their shape:

Flat spring
Made of a flat spring steel.
Machined spring
Manufactured by machining bar stock with a lathe and/or milling operation rather than a coiling operation. Since it is machined, the spring may incorporate features in addition to the elastic element. Machined springs can be made in the typical load cases of compression/extension, torsion, etc.
Serpentine spring
A zig-zag of thick wire, often used in modern upholstery/furniture.
Garter spring
A coiled steel spring that is connected at each end to create a circular shape.

Common types

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The most common types of spring are:

Cantilever spring
A flat spring fixed only at one end like a cantilever, while the free-hanging end takes the load.
Coil spring
Also known as a helical spring. A spring (made by winding a wire around a cylinder) is of two types:
  • Tension or extension springs are designed to become longer under load. Their turns (loops) are normally touching in the unloaded position, and they have a hook, eye or some other means of attachment at each end.
  • Compression springs are designed to become shorter when loaded. Their turns (loops) are not touching in the unloaded position, and they need no attachment points.
  • Hollow tubing springs can be either extension springs or compression springs. Hollow tubing is filled with oil and the means of changing hydrostatic pressure inside the tubing such as a membrane or miniature piston etc. to harden or relax the spring, much like it happens with water pressure inside a garden hose. Alternatively tubing's cross-section is chosen of a shape that it changes its area when tubing is subjected to torsional deformation: change of the cross-section area translates into change of tubing's inside volume and the flow of oil in/out of the spring that can be controlled by valve thereby controlling stiffness. There are many other designs of springs of hollow tubing which can change stiffness with any desired frequency, change stiffness by a multiple or move like a linear actuator in addition to its spring qualities.
Arc spring
A pre-curved or arc-shaped helical compression spring, which is able to transmit a torque around an axis.
Volute spring
A compression coil spring in the form of a cone so that under compression the coils are not forced against each other, thus permitting longer travel.
Balance spring
Also known as a hairspring. A delicate spiral spring used in watches, galvanometers, and places where electricity must be carried to partially rotating devices such as steering wheels without hindering the rotation.
Leaf spring
A flat spring used in vehicle suspensions, electrical switches, and bows.
V-spring
Used in antique firearm mechanisms such as the wheellock, flintlock and percussion cap locks. Also door-lock spring, as used in antique door latch mechanisms.[10]

Other types

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Other types include:

Belleville washer
A disc shaped spring commonly used to apply tension to a bolt (and also in the initiation mechanism of pressure-activated landmines)
Constant-force spring
A tightly rolled ribbon that exerts a nearly constant force as it is unrolled
Gas spring
A volume of compressed gas.
Ideal spring
An idealised perfect spring with no weight, mass, damping losses, or limits, a concept used in physics. The force an ideal spring would exert is exactly proportional to its extension or compression.[11]
Mainspring
A spiral ribbon-shaped spring used as a power store of clockwork mechanisms: watches, clocks, music boxes, windup toys, and mechanically powered flashlights
Negator spring
A thin metal band slightly concave in cross-section. When coiled it adopts a flat cross-section but when unrolled it returns to its former curve, thus producing a constant force throughout the displacement and negating any tendency to re-wind. The most common application is the retracting steel tape rule.[12]
Progressive rate coil springs
A coil spring with a variable rate, usually achieved by having unequal distance between turns so that as the spring is compressed one or more coils rests against its neighbour.
Rubber band
A tension spring where energy is stored by stretching the material.
Spring washer
Used to apply a constant tensile force along the axis of a fastener.
Torsion spring
Any spring designed to be twisted rather than compressed or extended.[13] Used in torsion bar vehicle suspension systems.
Wave spring
various types of spring made compact by using waves to give a spring effect.
Main article: Wave spring

Physics

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Hooke's law

[edit] Main article: Hooke's law

An ideal spring acts in accordance with Hooke's law, which states that the force with which the spring pushes back is linearly proportional to the distance from its equilibrium length:

F = − k x {\displaystyle F=-kx} ,

where

x {\displaystyle x} is the displacement vector – the distance from its equilibrium length.
F {\displaystyle F} is the resulting force vector – the magnitude and direction of the restoring force the spring exerts
k {\displaystyle k} is the rate, spring constant or force constant of the spring, a constant that depends on the spring's material and construction. The negative sign indicates that the force the spring exerts is in the opposite direction from its displacement

Most real springs approximately follow Hooke's law if not stretched or compressed beyond their elastic limit.

Coil springs and other common springs typically obey Hooke's law. There are useful springs that don't: springs based on beam bending can for example produce forces that vary nonlinearly with displacement.

If made with constant pitch (wire thickness), conical springs have a variable rate. However, a conical spring can be made to have a constant rate by creating the spring with a variable pitch. A larger pitch in the larger-diameter coils and a smaller pitch in the smaller-diameter coils forces the spring to collapse or extend all the coils at the same rate when deformed.

Simple harmonic motion

[edit] Main article: Harmonic oscillator

Since force is equal to mass, m, times acceleration, a, the force equation for a spring obeying Hooke's law looks like:

F = m a ⇒ − k x = m a . {\displaystyle F=ma\quad \Rightarrow \quad -kx=ma.\,}

The mass of the spring is small in comparison to the mass of the attached mass and is ignored. Since acceleration is simply the second derivative of x with respect to time,

− k x = m d 2 x d t 2 . {\displaystyle -kx=m{\frac {d^{2}x}{dt^{2}}}.\,}

This is a second order linear differential equation for the displacement x {\displaystyle x} as a function of time. Rearranging:

d 2 x d t 2 + k m x = 0 , {\displaystyle {\frac {d^{2}x}{dt^{2}}}+{\frac {k}{m}}x=0,\,}

the solution of which is the sum of a sine and cosine:

x ( t ) = A sin ⁡ ( t k m ) + B cos ⁡ ( t k m ) . {\displaystyle x(t)=A\sin \left(t{\sqrt {\frac {k}{m}}}\right)+B\cos \left(t{\sqrt {\frac {k}{m}}}\right).\,}

A {\displaystyle A} and B {\displaystyle B} are arbitrary constants that may be found by considering the initial displacement and velocity of the mass. The graph of this function with B = 0 {\displaystyle B=0} (zero initial position with some positive initial velocity) is displayed in the image on the right.

Energy dynamics

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In simple harmonic motion of a spring-mass system, energy will fluctuate between kinetic energy and potential energy, but the total energy of the system remains the same. A spring that obeys Hooke's Law with spring constant k will have a total system energy E of:[14]

E = ( 1 2 ) k A 2 {\displaystyle E=\left({\frac {1}{2}}\right)kA^{2}}

Here, A is the amplitude of the wave-like motion that is produced by the oscillating behavior of the spring.

The potential energy U of such a system can be determined through the spring constant k and its displacement x:[14]

U = ( 1 2 ) k x 2 {\displaystyle U=\left({\frac {1}{2}}\right)kx^{2}}

The kinetic energy K of an object in simple harmonic motion can be found using the mass of the attached object m and the velocity at which the object oscillates v:[14]

K = ( 1 2 ) m v 2 {\displaystyle K=\left({\frac {1}{2}}\right)mv^{2}}

Since there is no energy loss in such a system, energy is always conserved and thus:[14]

E = K + U {\displaystyle E=K+U}

Frequency & period

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The angular frequency ω of an object in simple harmonic motion, given in radians per second, is found using the spring constant k and the mass of the oscillating object m[15]:

ω = k m {\displaystyle \omega ={\sqrt {\frac {k}{m}}}} [14]

The period T, the amount of time for the spring-mass system to complete one full cycle, of such harmonic motion is given by:[16]

T = 2 π ω = 2 π m k {\displaystyle T={\frac {2\pi }{\omega }}=2\pi {\sqrt {\frac {m}{k}}}} [14]

The frequency f, the number of oscillations per unit time, of something in simple harmonic motion is found by taking the inverse of the period:[14]

f = 1 T = ω 2 π = 1 2 π k m {\displaystyle f={\frac {1}{T}}={\frac {\omega }{2\pi }}={\frac {1}{2\pi }}{\sqrt {\frac {k}{m}}}} [14]

Theory

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In classical physics, a spring can be seen as a device that stores potential energy, specifically elastic potential energy, by straining the bonds between the atoms of an elastic material.

Hooke's law of elasticity states that the extension of an elastic rod (its distended length minus its relaxed length) is linearly proportional to its tension, the force used to stretch it. Similarly, the contraction (negative extension) is proportional to the compression (negative tension).

This law actually holds only approximately, and only when the deformation (extension or contraction) is small compared to the rod's overall length. For deformations beyond the elastic limit, atomic bonds get broken or rearranged, and a spring may snap, buckle, or permanently deform. Many materials have no clearly defined elastic limit, and Hooke's law can not be meaningfully applied to these materials. Moreover, for the superelastic materials, the linear relationship between force and displacement is appropriate only in the low-strain region.

Hooke's law is a mathematical consequence of the fact that the potential energy of the rod is a minimum when it has its relaxed length. Any smooth function of one variable approximates a quadratic function when examined near enough to its minimum point as can be seen by examining the Taylor series. Therefore, the force – which is the derivative of energy with respect to displacement – approximates a linear function.

Force of fully compressed spring

F m a x = E d 4 ( L − n d ) 16 ( 1 + ν ) ( D − d ) 3 n {\displaystyle F_{max}={\frac {Ed^{4}(L-nd)}{16(1+\nu )(D-d)^{3}n}}\ }

where

E – Young's modulus
d – spring wire diameter
L – free length of spring
n – number of active windings
ν {\displaystyle \nu } – Poisson ratio
D – spring outer diameter

Zero-length springs

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Zero-length spring is a term for a specially designed coil spring that would exert zero force if it had zero length. That is, in a line graph of the spring's force versus its length, the line passes through the origin. A real coil spring will not contract to zero length because at some point the coils touch each other. "Length" here is defined as the distance between the axes of the pivots at each end of the spring, regardless of any inelastic portion in-between.

Zero-length springs are made by manufacturing a coil spring with built-in tension (A twist is introduced into the wire as it is coiled during manufacture; this works because a coiled spring unwinds as it stretches), so if it could contract further, the equilibrium point of the spring, the point at which its restoring force is zero, occurs at a length of zero. In practice, the manufacture of springs is typically not accurate enough to produce springs with tension consistent enough for applications that use zero length springs, so they are made by combining a negative length spring, made with even more tension so its equilibrium point would be at a negative length, with a piece of inelastic material of the proper length so the zero force point would occur at zero length.

A zero-length spring can be attached to a mass on a hinged boom in such a way that the force on the mass is almost exactly balanced by the vertical component of the force from the spring, whatever the position of the boom. This creates a horizontal pendulum with very long oscillation period. Long-period pendulums enable seismometers to sense the slowest waves from earthquakes. The LaCoste suspension with zero-length springs is also used in gravimeters because it is very sensitive to changes in gravity. Springs for closing doors are often made to have roughly zero length, so that they exert force even when the door is almost closed, so they can hold it closed firmly.

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Uses

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See also

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  • Shock absorber
  • Slinky, helical spring toy
  • Volute spring

References

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Further reading

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  • Sclater, Neil. (). "Spring and screw devices and mechanisms." Mechanisms and Mechanical Devices Sourcebook. 5th ed. New York: McGraw Hill. pp. 279–299. ISBN . Drawings and designs of various spring and screw mechanisms.
  • Parmley, Robert. (). "Section 16: Springs." Illustrated Sourcebook of Mechanical Components. New York: McGraw Hill. ISBN  Drawings, designs and discussion of various springs and spring mechanisms.
  • Warden, Tim. (). “Bundy 2 Alto Saxophone.” This saxophone is known for having the strongest tensioned needle springs in existence.