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General Spring FAQs

How is a spring's fatigue life predicted?
We analyze our spring’s fatigue life predictions using methods consistent with SAE and SMI guidelines. Essentially, the minimum and maximum operating stresses are calculated and compared to a family of reference Modified Goodman Diagrams. It is best to demonstrate fatigue life capability through testing. This testing is especially important in special cases with unusual spring configurations or the use of non-standard, unique materials. In these cases, MW Components uses reliability engineering techniques to develop test methods. We carefully analyze these test results to ensure our products will meet and exceed customer expectations.

How much energy is stored in a compression spring?
The stored energy is the integral of the load vs. deflection curve. For a spring with a constant rate of k deflected x from its free length, the stored energy will equal (kx^2)/2.

What are the common terms used to describe springs?
d – wire diameter
D – mean diameter, the diameter of the spring as measured at the wire centerline
ID – inside diameter, D-d
OD – outside diameter, D+d
Na – number of active coils
Nt – total coils, active coils plus any inactive coils. For a spring with closed ends, Nt=Na+2
FL – free length, the spring length with no load applied
P, F – load or force, the force exerted by the spring under a given deflection
l – instantaneous spring length, the spring length corresponding to a given applied load
x, s – instantaneous deflection, the amount the spring is compressed from free length to length l. x=FL-l
k – spring rate, the derivative of the load-deflection curve. k=P/x=(P2-P1)/(l1-l2)=(P2-P1)/(x2-x1)
C – spring index, the ratio of the mean diameter to the wire diameter. C=D/d

What are residual stresses?
Residual stress forms when a product is welded, cut, cast, or undergoes some other manufacturing processes involving heat or deformation. Residual stress may be beneficial or not, depending on the application.

MWI engineers will answer any questions you might have regarding product design, material selection, or application.

What are machined springs?
A machined spring is a single piece of material machined into a spring configuration and offering the traditional load cases of Compression/Extension, Torsion, Lateral Bending, and Lateral Offset. Key to the versatility of the machined spring is the Helical® Flexure, a flexible helix beam concept. Because our springs are “machined” to specific design requirements, they provide more precise performance, attachment features, and functions than more traditional types of springs.

Why choose machined springs over traditional wire-wound springs?
With machined springs, desired features or functions can be machined integral to the spring, therefore eliminating complex or expensive wire-wound spring assemblies. Features and functions can include custom attachments, precise spring rates, multiple start coils, and other special characteristics. These aspects are generally not possible with traditional springs. There are big differences in performance, reliability, versatility, integrity, and cost-effectiveness.

Looking for More Spring Resources?

Visit our resource center to find educational content like design guides, white papers, case studies, webinars, and more.