Custom Compression Spring Manufacturer

Compression Springs are open-coiled helical springs designed to resist a compression force applied along the axis of the coil. As the coils are compressed from their free length, the spring operating length is shorten and the compression spring stores energy or provides a force for the specific application.

Most compression springs are a straight cylindrical spring made of round wire. Optimum Spring manufactures custom compression springs in different types and configurations to suit your specifications.

To help you solve basic compression spring design challenges, please visit our Compression Spring Design Alternatives Guide.

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Configuration

Common shapes we manufacture are:

Cylindrical springs, straight or standard: All coils have the same diameter with a constant rate. These are the most common and cost effective to manufacture.
Conical or Tapered: Coil diameter decreases from one end of the spring to the other. The smaller coils telescope down into the larger coils as the spring is compressed so that the spring can operate in a smaller axial space. You can use this type of spring when there is not enough space for a cylindrical spring. In a conical spring the load vs. deflection curve gets steeper as the spring is compressed and the larger diameter coils bottom out, reducing solid height.
Barrel or Convex: Tapered so that coil diameter at the ends are smaller than the middle coil diameter. These types of spring have some of the same advantages as conical springs with the added advantage that they are symmetrical. The reduced end coils help the spring to be centered on a smaller diameter shaft.
Hourglass Springs or Concave: Tapered so that coil diameter at the ends are larger than the middle coil diameter. These types of spring have some of the same advantages as conical springs with the added advantage that they are symmetrical. The enlarged end coils aid the spring to be centered on a larger diameter hole.
Variable Pitch: With a varying amount of space between the coils. This type of compression springs has a non-linear load vs. deflection curve, and is used to minimize resonant surging and vibration. By adding closed coils in the center of the spring you can reduce tangling.

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Physical Parameters

d (Wire Diameter): Wire diameter for the spring material.
S (Shaft): Maximum diameter of a spring shaft in industrial applications.
Di (Internal/Inside Diameter): Calculated by subtracting two times the wire diameter from the external diameter of a spring.
De (External/Outside Diameter): Calculated by adding the internal diameter plus two times the wire diameter of a spring.
H (Hole): Minimum diameter of the hole in which a spring works.
L0 (Free Length): Overall length of a spring in unloaded position.
Number of coils: Total number of coils in a spring. The above picture shows six coils. To calculate the number of active coils, subtract two terminating coils from total number of coils.

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Performance Factors

P (Pitch): Average distance between two subsequent active coils of a spring.
Lc (Bock Length/Solid Length): Length of a spring when completely compressed.
Ln (Maximum Loaded length): Maximum permitted length of a spring after loading. If deflection is higher it may cause plastic deformation.
R (Spring Rate/Stiffness): the change in load per unit deflection in pounds per inch (lb/in) or Newtons per millimeter (N/mm).
L1 & F1 (Length at Force F): Force F1 at Length L1 can be calculated from equation:
F1 = (L0-L1) * R.
Equation derived from previous for calculating L1:
L1 = L0 - F1/R
Helix Direction: Right or left-handed. A left-handed spring loads in a clockwise direction.
End Treatment: Open, open and ground, closed or closed and ground ends

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Wire Diameter

We manufacture compression springs with a wire diameter of 0.004" up to 0.120" (0.1mm to 3.0mm)

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Wire Material

Music wire, hard drawn, and Stainless steel are the most common materials we use to manufacture compression springs. You can find other materials and properties listed in the Materials table.

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Wire Selection

Round wire is most commonly used for compression springs because it is most adaptable to standard coiler tooling. We can manufacture compression springs with square, rectangular and special wire sections.

An optimum compression spring depends on:

Operating Environment
Space
Energy
Service Life /Fatigue

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Design Decisions

Compression springs are mounted over a rod or fitted inside a hole. When the spring is compressed, it shortens, pushes back against the load and tries to get back to its original length thus offering resistance to linear compressing forces.

Dimensional Limits: As a compression spring assumes a load and shortens, the body diameter will large. Make sure the wire diameter times the number of coils is not greater than the space allowed for that spring.
High Temperature Environment: may affect the length of the spring. Consider designing your compression spring slightly longer.
Stress Level: Determined by the dimensional limits along with the load and deflection requirements. Our compression springs are stress-relieved to eliminate any residual bending stresses produced by manufacturing process and enhance stress performance of the compression spring.
Load: Spring Rate multiplied by the deflection from Free Length.
Measured Spring Rate: Lbs. of load per inch of deflection.

Compression springs can be measured by taking the difference in force at 80% maximum deflection and 20% maximum deflection and dividing by the difference in deflection. The spring rate is constant over the central 60% of the Deflection range. Because of end-coil effects, the first 20% of deflection range has a considerably lower spring rate. The final 20% of deflection shows considerably higher spring rate. If possible, critical loads and rates should be specified within the central 60% deflection range.
Spring Rate: (R) = Gd⁴/8nD³ pounds per inch where:
- R: Rate, pounds of load per inch of deflection
- G: Modulus of rigidity of material, pounds per square inch
- D: Wire diameter, inches
- N: Number of active coils
- D: Mean coil diameter, inches
We can manufacture variable rate compression springs to improve performance against buckling and surging, however they are usually more costly. These springs have a variable body diameter, or a variable pitch. To vary the spring rate, the amount and rate of active coil stack up is changed throughout the working range of the spring. As more active coil stacks up, the amount of active coil remaining active is reduced. This loss of active coil causes the rate to increase. It is not possible to have a variable rate compression spring where the rate decreases as the deflection increases.
Deflection: A spring will compress when a load is applied. It is not advisable to use more than 80% of the maximum possible deflection. The amount of deflection will be determined by dividing the maximum load by the spring rate.
Helix Direction: Consider helix direction when two or more springs are being nested, or when a spring is mounted over a rod. They must be alternated to avoid friction between the spring and the rod or coil conflict between adjacent springs.
End Treatment:
End grinding reduces the solid height of the spring, and will increase the available load bearing surface of the end coil. Grinding the ends permits greater squareness control and inhibits buckling. Closed ends prevent tangling. Grinding significantly increases the spring cost and is often unnecessary for small wire sizes.
- Ends Open and not Ground: the coils are consistent with no pitch change through the end of the spring. Springs with open ends and not ground, are manufactured when the solid height and rate are not an issue and where the design allows for more generous length tolerance. Open ends are commonly used when the spring screws onto a threaded part.
- Ends Closed (squared) and not Ground: the end coils' pitch is reduced so the end coils touch. Springs with closed ends and not ground are the most economical to manufacture and often performs well when the spring index exceeds 12:1 and/or the wire diameter is smaller than .020".
- Ends Open and Ground: last coil ground ‘flat’ in appearance and has a less parallel end. Springs that are open and ground are manufactured when it is necessary to have a lower solid height and/or more active coils are required to affect the needed rate.
- Ends Closed (squared) and Ground: Springs with ends closed and ground offer better seating/squareness, which also influences how the axial force produced by the spring is transferred to its mating part, or the mechanism that it works in. With this configuration buckling is reduced.
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Production

We offer fast turnaround on small, medium and large runs. In addition, we welcome any custom compression spring projects which require limited quantities. Our design specialists offer you specific advice and design review during the prototyping process.

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