KEVOS® MAKEOS · Mechanics
Cam Follower Return Spring Check (Inertia Force, Jump Speed)
Is my follower return spring strong enough to keep the follower on the cam at this speed, and at what speed will the follower start to jump?
Check of the spring that holds a cam follower against the cam: the peak deceleration of the follower for the motion law, rise, cam angle and speed (as the cam follower motion tool), the inertia force at that point, where in the rise it occurs, the spring force there from its preload and rate, the margin against jump, the speed at which the follower would leave the cam, and the largest spring force against the spring’s rating.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Motion law | choice | Motion law of the rise. |
| Rise (lift) | mm | Total rise of the follower. |
| Cam angle for the rise | ° | Cam angle over which the rise happens. |
| Cam speed | rpm | Cam speed. |
| Follower moving mass (with a third of the spring) | kg | Mass of the follower and everything moving with it, plus about a third of the spring. |
| Spring | ||
| Spring force with the follower at rest (bottom) | N | Force the spring exerts with the follower at the bottom of its travel. |
| Spring rate | N/mm | Rate of the spring. |
| Required margin over the inertia force | How much the spring force must exceed the inertia force where deceleration peaks. | |
| Largest force the spring is rated for | N | Largest load the spring can take without overstress (at full lift). |
Method and formulas
- Peak acceleration = c h ω² ÷ β² with c for the law (as the cam follower motion tool); the peak deceleration has the same size.
- It occurs at the end of the rise (harmonic), ¾ of the cam angle (cycloidal), from half the rise (parabolic) or at 0.789 of the angle (3-4-5); the spring force there = F₀ + k × lift at that point.
- Jump speed = speed × √(spring force ÷ inertia force); spring force at full lift = F₀ + k h.
- Example: the follower decelerates at 28.274 m/s², needing 42.412 N; the spring gives 114.55 N there, so the follower jumps at about 493.03 rpm.
Limitations
- Rigid follower and linkage; elasticity adds vibration that can cause jump earlier.
- Gravity and friction ignored; a vertical follower moving down gains help from gravity on the return.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a cam follower return spring
- Find the highest safe cam speed
- Check a cam after a speed increase
Who it is for
- Machine designers
- Automation engineers
- Design engineers
What you get
- Peak deceleration and inertia force
- Spring force where it peaks and the margin
- Jump speed and full-lift spring force
Interpreting the result
- Inertia force rises with the square of speed: a 40% speed increase roughly doubles the spring force needed.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2284–2309, 304–320. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Cam Follower Return Spring Check (Inertia Force, Jump Speed) calculator
