Compound Disc Spring Mechanism Explained: Stacking, Parts, Formula, and Uses

How the discs are stacked

A disc spring is a conical washer with a central opening. The upper detail shows the central opening. In the lower axial section, each washer appears as two sloping sections on either side of the guide pin. A moving upper plate compresses the stack against a fixed lower plate.

Within each group, the discs face the same way and nest together. The next group faces the opposite way. Neighboring groups meet at their inner or outer rims, and each group shortens as its cones flatten. Alternating colors identify groups without implying different materials.

Both manufacturer guidance and Hiscox’s historical figure 1145 show the importance of dished discs arranged around a guide. The present dimensions are explanatory. Its count controls specify the number of groups and discs, not a commercially qualified stack.

Using the multipliers

Disc spring stacks are used where a compact axial spring is useful, including preload and compliant clamping arrangements. This calculator helps compare arrangements using identical discs. An actual selection must start with an appropriate manufacturer’s single-disc load-deflection data and application requirements.

Increasing the parallel count increases force at a corresponding disc deflection. Increasing the series count increases total travel at a corresponding force. The section view updates the arrangement so these changes can be checked visually.

Force, travel and local rate

Let s be the number of identical groups in series, p the discs nested in each group, and f(δ) the force of one disc at deflection δ. Ideal load sharing gives F_stack(δ_stack) = p f(δ_stack/s). The total washer count is sp.

Therefore force is multiplied by p at corresponding single-disc deflection, while stack travel is multiplied by s at corresponding force. Differentiating gives k_stack = (p/s) k_single at corresponding points on the curves. This is a local slope relationship: a nonlinear single-disc curve remains nonlinear.

The counts alone do not determine an absolute force, stroke, stress or fatigue life. Friction, uneven deflection and tolerances are omitted.

Example: four groups of two discs

Count the discs

Four series groups, each containing two parallel discs, use 4 × 2 = 8 discs.

Compare load and travel

If one selected disc has force F at deflection δ, the ideal stack has force 2F at total deflection 4δ.

Compare local stiffness

The local stiffness multiplier is 2/4 = 0.5. This comparison uses the corresponding point on the single-disc curve, not an assumed constant stiffness.

What changes in a physical stack

The ideal multipliers explain the arrangement, but friction and manufacturing variation can cause actual load-deflection behavior to differ. More interfaces also complicate contact and load sharing. The guide keeps the discs aligned; its clearances and the bearing surfaces need to be selected for the actual parts.

The animation does not represent buckling, stress, wear or permanent flattening. Its illustrated compression limit is chosen to make the movement visible, not to establish a permissible operating range.

Questions about compound disc springs

Which arrangement adds force?

Same-facing discs nested in parallel add their forces at the same single-disc deflection in the ideal model.

Which arrangement adds travel?

Opposing identical groups in series add their deflections while carrying the same load.

Why does the section show two pieces for each disc?

A section through an annular washer cuts its two sides. The apparent gap is the central hole around the guide; the washer remains one continuous ring in three dimensions.

Can the calculated multipliers give an absolute load rating?

Only when combined with suitable single-disc data and the additional checks required for the actual assembly. The two count inputs alone cannot provide that rating.