A couple of years ago I provided a brief overview of compression springs and I have decided to return to this topic by providing a calculator (Figure 1) to calculate the forces and if the chosen spring is at risk of buckling. More info can be found below.
Figure 1 Compression spring calculator
Force calculation
Figure 2 Force calculation section
This section is for calculating the force (Figure 2) of your compression spring. You only need to fill out the Spring rate, free length and loaded length which are highlighted in blue. Multiple springs can be calculated at the same time as in some projects you may want to compare multiple springs at once to find out the best suited model. To help keep track you can record the model no you are comparing.
Springs generally have force tolerances of +/- 10%. The calculator will provide the +/-10% of the forces. It is always good practice to calculate with tolerances because you want to ensure your spring will provide the required preload with the machining tolerances in play.
You can also use this calculator to calculate the forces of a spring at different loaded heights to check if the spring will produce enough force as it is returning back to it’s free height.
Buckling
Figure 3 Buckling ratio with outer diameter
This section (Figure 3) is for calculating the slenderness ratio which determines if your spring will buckle under load if it is not supported.
You only need to fill out the Mean diameter, wire diameter and outer diameter which are highlighted in blue.
Figure 4 Slenderness ratio with inner diameter
Some cases the inner diameter of a spring is only supplied therefore a separate section (Figure 4) is provided to calculate the slenderness ratio with the inner diameter.
If the slenderness ratio is >4 the spring will buckle. You can help prevent buckling by placing the spring into a hole or having a mandrel in the center. To determine the required hole or mandrel size please refer to your manufacturer of your spring.
In the near future the calculator will be updated with different spring types.