KEVOS® MAKEOS · Mechanics
Cam and Spring-Loaded Follower Design
Will this cam’s follower stay in contact at speed, what spring preload does it need, and is the pressure angle acceptable?
Design check of a radial cam with a translating roller follower held by a spring: follower displacement, velocity and acceleration through the rise for simple harmonic, cycloidal or constant-acceleration motion, the maximum pressure angle, the contact force through the cycle from inertia, spring and external load, and the spring preload needed to keep contact with a margin.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Rise motion | choice | Motion law used for the rise (the return is assumed symmetric). |
| Rise | mm | Total lift. |
| Cam angle for the rise | ° | Cam rotation over which the rise happens. |
| Cam speed | rpm | Cam speed. |
| Base circle radius | mm | Base circle radius of the cam. |
| Roller radius | mm | Radius of the follower roller. |
| Follower and linkage mass | kg | Moving mass reduced to the follower. |
| External load opposing the rise | N | Constant external force the follower works against. |
| Spring rate | N/mm | Return spring rate. |
| Spring preload at the bottom of the rise | N | Spring force with the follower at the bottom of its travel. |
| Contact margin on preload | Factor on the preload needed just to keep contact. | |
| Pressure angle limit | ° | Largest pressure angle you accept (about 30° for translating followers). |
Method and formulas
- Follower motion y(θ), y′(θ), y″(θ) for the chosen law; velocity = y′ω, acceleration = y″ω².
- Pressure angle = atan[y′ ÷ (R_b + R_r + y)], maximum found over the rise.
- Contact force N = F₀ + k y + F_ext + m a; the follower jumps where N < 0.
- Preload needed = margin × max(−m a − F_ext − k y) over the rise.
- Example: a 20 mm cycloidal rise over 120° at 600 rpm peaks at 113.1 m/s² and needs 142.44 N of preload.
Limitations
- Rigid follower train; at high speed elasticity adds vibration and needs a dynamic model.
- Symmetric return assumed; dwell periods are not modelled.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size the return spring for a cam follower
- Check a cam for follower jump at a higher speed
- Choose base circle size for the pressure angle
Who it is for
- Machine designers
- Automation engineers
- Design engineers
What you get
- Peak velocity, acceleration and pressure angle
- Minimum contact force through the rise
- Spring preload needed
Interpreting the result
- Cycloidal motion has no jerk spikes and is preferred at speed; a larger base circle lowers the pressure angle.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2284–2310. Topic reference; no source tables or recommended settings are reproduced.
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