Profile shape and motion synthesis
A cam is a rotating or sliding profile that directs a follower (a roller, needle, or flat surface in contact with the cam) through a prescribed displacement path. The cam profile determines how far and how fast the follower moves as the cam rotates. Engineers design cam profiles to achieve specific follower displacement, velocity, and acceleration curves, a process called motion synthesis. Common profiles include polynomial functions (parabolic, cubic), harmonic motion (sinusoidal), and cycloidal (smooth combination) chosen to balance smoothness and manufacturing feasibility.
Acceleration and shock loads
Rapid acceleration causes high inertial forces and dynamic stresses in both cam and follower. Ideally, acceleration ramps smoothly from zero, avoiding instantaneous jumps that transmit shock to the mechanism. Parabolic profiles accelerate uniformly (constant jerk); cycloidal profiles approach zero acceleration smoothly at the endpoints. Roller followers reduce sliding friction and wear compared to flat followers, but add mass and moment of inertia, slowing transient response in high-speed cams.
Manufacturing and precision
Cam profiles are ground to fine tolerance (+/- 0.01 mm typical) because small profile errors compound into follower position errors and dynamic excitation. Cast iron and hardened steel are common materials. Computer numerically controlled (CNC) grinders produce complex profiles faster than manual methods. Pressure angle (the angle between the normal force and follower velocity direction) affects friction and wear; limiting it to 30 degrees or less prevents follower jamming and excessive side loading.