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Spring Design Techniques: Helical Compression Springs

The logic diagram below is intended as a tool for helical compression spring design techniques. Hopefully it will be a guide and provide some inspiration for the designer. It is a template for one of many spring design techniques, outlining the step-by-step procedure. No single logic diagram will lead to the solution of all spring problems. The performance specifications vary far too widely for this.

This logic diagram shows the basic steps and procedures which will determine if the spring can be made to specifications. The design that is derived is only an initial design and may not be the most economical one. What also needs to be considered are the manufacturing techniques required, the quantities involved, the tolerances needed, etc.

Click here to go to our web page with the Wahl Factor(K_w1) chart.

Click here to go to our web page with charts on S_max and YS

Click here to go to our web page on Spring Steel Types for charts on TS

DESIGN EXAMPLE

The spring design techniques used by designers usually solve by manipulating the stress and load/deflection formulas. Designers do this by reconciling variables to meet three parameters-

available space
work to be done by the spring
strength of the material

Here is one systematic approach to this problem that has been found successful. There are three major steps:

A. Establish a tentative design
B. Evaluate this design by comparing

space used vs. space available
stress vs. strength of the material

Trying a larger or smaller wire size depending upon the values in step B, solve for N and repeat step B.

Refer to the logic diagram above for assumptions.

Here is the problem:

Given: Squared and ground compression spring to work in a D_H=1.5 in. diameter hole and exert P₁=60 lb. at a length of L₁=2.5 in. and P₂=105 lb. at a length of L₂=2.0 in. The application is static and at room temperature. The raw material is oil tempered round wire, ASTM 229.

A.Solve the uncorrected stress formula for wire diameter using approximate values for the unknown factors.

Calculate OD and D

Substitute this wire size in the load/deflection formula and solve for N. (Use approximate values for the unknown factors.)

B.Find the amount of space left between L₂ and L_s. Compare to f₂.

Find the corrected stress at solid height.

Compare to tensile of the material by going to this web page.

compression spring

The tensile of 0.158 diameter wire = 205,000psi. Click here to see the chart on S_max which shows that 165,000psi is greater than S_max for this wire size. The stress is too high at solid.

C. Because (L₂-L_s)=0.935>0.1 f₂=0.117 there is more space available and the stress is too high. Try a larger wire size.

Try d=0.177 in. and D=1.425-0.177=1.248 in.

This is within the elastic limit.

END OF DESIGN

Now that you have completed this page it is time to visit our page on Design for Manufacture and Assembly to help get some other perspectives on the effects of the design you may settle on. This page is also full of handy reference charts.

Stay tuned for updated information related to compression spring design. Our team and visitors to spring-makers-resource.net will be contributing.

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