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Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Outer Diameter:

to

inches mm

Inner Diameter:

to

inches mm

Free Length:

to

inches mm

Wire Diameter:

to

inches mm

Total Coils:

to

Rate: ? Spring rate or spring constant: The amout of force required to move the spring 1 inch of distance or in millimeters the amount of force required to move the spring 1 millimeter of distance.

to

lbs/in N/mm

Info! Please fill in one or more fields to narrow down your search.

Max. Load: ? The maximum amount of force or load you can place on this spring. If you put more force than this you will distort or fatigue the spring.

to

lbs N

Max. Deflection (Max. Travel):

to

inches mm

Solid Height:

to

inches mm

* Required Field

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Outer Diameter:

to

inches mm

Length Inside Hook:

to

inches mm

Wire Diameter:

to

inches mm

Info! Please fill in one or more fields to narrow down your search.

Max. Load: ? The maximum amount of force or load you can place on this spring. If you put more force than this you will distort or fatigue the spring.

to

lbs N

Max. Deflection (Max. Travel):

to

inches mm

Initial Tension: ? The force required to seperate the coils of an extension spring before the spring will extend.

to

lbs N

Rate: ? Spring rate or spring constant: The amout of force required to move the spring 1 inch of distance or in millimeters the amount of force required to move the spring 1 millimeter of distance.

to

lbs/in N/mm

* Required Field

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Outer Diameter:

to

inches mm

Inner Diameter:

to

inches mm

Free Position or Leg Position in degrees: ? Free Position or Leg Position in degrees

degrees

Total Coils:

to

Wire Diameter:

to

inches mm

Body Length:

to

inches mm

Info! Please fill in one or more fields to narrow down your search.

Max. Torque: ? The amount of force applied to a torsion spring to radially move the springs leg a certain amount of degrees.

to

lbs N

Max. Deflection (Degrees of travel):

to

degrees

Rate: ? Torsion spring rate is the amount of radial force required to move the spring 360 degrees of distance. Divide the spring rate by 360 degrees to get the rate per degree

to

in-lbs./deg. N-mm/deg.

Leg Length: ? Both legs are equal in length

to

inches mm

* Required Field

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Small Outer Diameter:

to

inches mm

Large Outer Diameter:

to

inches mm

Free Length:

to

inches mm

Info! Please fill in one or more fields to narrow down your search.

Rate: ? Spring rate or spring constant: The amout of force required to move the spring 1 inch of distance or in millimeters the amount of force required to move the spring 1 millimeter of distance.

to

lbs/in N/mm

Total Coils:

to

Solid Height:

to

inches mm

Wire Diameter:

to

inches mm

4 Compression Spring Design Problems

Depending on how demanding your spring needs are you might run into a couple of curve balls when working on a compression spring design. Either you can’t make the working loads match your requirements, you can’t get the strength/elasticity you need, or you have a design that is very difficult to manufacture. Whatever the case, you will find the solution to these and several other problematics that may arise when creating a compression spring design.

Design Problem #1

My compression spring took a set…

When a compression spring takes a permanent set, it means you’re exceeding the maximum safe load along with the maximum safe travel. This may happen because you don’t know your spring’s maximum safe compression and probably tried to compress it all the way down to solid height. A set compression spring will not bounce back to its original free length but the free length will actually be shorter. This means you’ve lost force and coil memory.

Solution

The way to fix this is to re-design your spring so that it is both stronger but under less stress so that you can achieve more force and more travel. If you make an adjustment to make the spring stronger, it will achieve more force but it will be under more stress. Which is why you must find the ideal balance between strength and weakness tweaking the design to make it weak enough to be a little more elastic and strong enough to withstand the force. The adjustments you must make are explained in the force chart provided in this article. Use it to work on the design until you are able to reach the point where you can meet both your force and elasticity requirements.

compression spring permanent set problem

Design Problem #2

My spring Index is too large / too small…

Both a loose or tight spring index can make it difficult to manufacture your compression spring. However, a tight index is much more complicated to manufacture. This is due to the stress that the tooling on the CNC machine is under when making these springs. The tighter it is, the more stress that the tooling is under which creates a risk of the coiling points breaking. This taken into consideration, not only will the spring be difficult to manufacture but it will also be a more costly job.

Solution

To fix a tight spring index (less than 4), you must loosen the coil diameter more by either making the wire diameter smaller and/or making the outer diameter larger. To fix a large spring index (over 15), you do the opposite: make the wire diameter larger and/or make the outer diameter smaller.

compression spring tight and loose index examples

Design Problem #3

My spring buckles / bends during compression…

When you have a compression spring which bends or buckles during deflection/travel, it means you have a high slenderness ratio. This is the proportional ratio between your spring’s coil diameter and the free length. A spring with a free length more than three times longer than the coil diameter runs the risk of bending during deflection.

Solution

To fix this issue, you must either make the free length shorter, make the outer diameter larger, or go for a tapered design. Spring types with tapered sections of their body include conical springs, barrel springs, and hourglass springs. Tapered springs are non-linear so you would have to work out a design that’ll meet your working loads (load at loaded height).

compression spring buckling example for slenderness ratio calculations

Design Problem #4

My spring’s solid height doesn’t allow me to meet my loaded height…

To calculate solid height, you must multiply the total coils by the wire diameter and add another wire diameter. If this measurement is longer than the solid height you want to achieve, you have a problem.

Solution

The way to solve this issue is by reducing the wire diameter or the number of coils. This might affect your spring’s rate or working loads so you might want to adjust the outer diameter as well while you’re at it to make sure it meets your needs. If you reduce the wire diameter, your spring will be weaker so you’d have to make the outer diameter smaller. If you adjust the number of coils, your spring will become stronger so you would have to make the outer diameter larger.



Less ForceMore Force
– Wire Diameter + Wire Diameter
+ Outer Diameter – Outer Diameter
+ Coils – Coils
+ Free Length – Free Length