Open-coil helical springs that are constructed or wound to oppose compression along the direction of the wind are known as compression springs. The most typical design for metal springs is helical compression. Although frequently assembled over a guide rod or fitted inside a hole, these coil springs can function independently. A compression coil spring resists the load and tries to revert to its original length when you compress it, making the spring shorter. Compression springs will be thoroughly discussed in this article.
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What Is Compression Spring?
A compression spring is an axial helical spring with an open coil that resists axial compression. Although they can be coiled in other necessary shapes like conical, concave (barrel), convex (hourglass), or various combinations of these, they are typically coiled at a constant diameter.
Depending on the situation, compression springs can be used to store energy or resist force.
By being compressed or pushed against, compression springs exert force. All compression springs are cylindrical and made of music wire or round stainless steel. Compression springs can also be produced in a variety of shapes, such as barrel, conical, hourglass, or oval. Additionally, the wire may be square, rectangular, or almost any other shape, size, or material.
Compression springs, by far the most common kind of spring, are made to resist compression and expand back to their original length once the applied force is removed. Compression springs can be used in a variety of situations; the only restriction is your imagination.
Common Compression Spring Applications
Compression springs can be made in countless sizes and have a high degree of power. Because of this, compression springs are ideal for a diverse range of applications – most living in your every day, such as:
- Pens
- Pogo sticks
- Couches
- Mattresses
- Locks
- Button-operated devices or mechanisms
- Automobile suspension
- Medical devices
What To Consider When Selecting Compression Springs?
The are various considerations when choosing compression springs which include:
Compression Spring End Considerations
There are both standard and custom compression spring end types. Open, closed, and ground ends are all possible for standard ends. The spring rate will vary depending on whether the ends are open or closed when the coil count, wire size, and outside diameter (OD) is the same.
This characteristic will, however, improve the squareness of the loading force and lessen spring buckling tendencies when combined with closed ends. Ground ends necessitate additional manufacturing work.
It’s important to understand that not all manufacturers, but some do, offer closed and ground ends in their standard catalog stock designs. Expanded coils that snap into ring grooves, offset legs that act as alignment pins, and decreased coils for screw attachment are a few examples of special ends.
Compression Spring Material Considerations
Only a few possible spring materials include carbon steel and rare alloys. Music wire, a high-carbon spring steel, is the most common substance. Although music wire is stronger, stainless steel 302 has better overall corrosion resistance.
Due to their extremely high or low operating temperatures, unique corrosive environments, and non-magnetic characteristics, nickel alloys are preferred. They bear a number of trademarks on their packaging. Phosphor bronze and beryllium copper are two additional copper alloys with exceptional electrical conductivity and corrosion resistance.
Compression Spring Physical Considerations
- Outer Diameter: It is important to take the outside diameter of the compression spring into account if it is going into a hole. In any case, it is necessary to measure any internal parts of the device that will surround the spring. If a spring will be used in a tube or a bore, it is important to take into account that its outer diameter (OD) will increase when it is compressed.
The assembly’s required envelope size may increase due to manufacturing restrictions on the outside diameter of springs. A work-in-hole diameter for spring will typically be specified by spring manufacturers based on anticipated OD expansion and manufacturing tolerance. Use this knowledge to more clearly communicate your product requirements when ordering springs that aren’t in stock or to pick out springs from catalogs with ease.
- Inner Diameter: The spring’s inner diameter must be taken into account if the compression spring passes over a shaft or mandrel. A ten-thousandth of an inch must separate the shaft from the spring in order to avoid friction.
- Free Length: It is suggested that the compression spring’s free length be slightly greater than the available space to guarantee that it is in a preloaded state and maintains its position.
- Solid Height: The spring’s solid height is influenced by the wire diameter and the total number of coils. Verify that the height when loaded does not fall below or rise above the height when it is solid.
Temperature and other elements like moisture are included in the environment where the spring will be used. A spring can withstand higher temperatures as long as its material is more expensive, but doing so will raise the price of the spring.
Compression Spring Load Considerations
It is also necessary to take the loading or travel of the compression spring into account. The term “spring rate” or “spring constant” refers to the relationship between the force required to compress a spring by a unit of length, which is typically measured in pounds per inch (lbs/in). Therefore, the projected spring travel under a specific load can be calculated by the product designer.
As the spring is driven farther, it experiences increasing stress. Under prolonged stress, the wire’s composition may eventually give way, causing spring set, a phenomenon. Once the spring is set, it won’t expand back to its original, unloaded length. Nevertheless, this spring might be helpful depending on the assembly.
How Is A Compression Spring Measured?
- Using calipers, measure the diameter of the spring wire, preferably to three decimal places for accuracy.
- The coils’ external diameter should be measured. Consider measuring the higher value as there may be a slight variation in this between coils.
- The length should be measured in its uncompressed, free state.
- How many coils are there? Count to the nearest eighth to determine the number of revolutions from tip to tip.
- Be sure to take note of the coils’ winding direction. In the majority of applications, this is not significant, but check to see if any adjacent components call for the spring to be in a particular direction.
- Remember the spring’s end type. The ends of compression springs may be ground or not, the end coils may be open or closed, or they may have another configuration that may need to be described in a blueprint.
- Find out what kind of material spring wire is. If the wire is not drawn to a magnet, it might be a unique metal alloy that requires precise identification. If the substance is unknown, make a note of any unusual operating circumstances, such as extremely high or low temperatures, the presence of corrosive substances, or rapid cycling.
