Cams and Followers free study notes

1. What is Cams and Followers ?

A cam is a rotating or sliding element with a specially shaped profile, while a follower is a component that remains in contact with the cam surface and moves according to its contour. As the cam rotates, the follower executes a specific motion (linear or angular).

The motion generated is not simple harmonic by default—it depends entirely on the cam profile.

2. Elements of a Cam Mechanism

1. Cam – Driving element
2. Follower – Driven element
3. Frame – Supports cam and follower
4. Spring or Gravity – Maintains contact between cam and follower

3. Types of Cams

1. Disc (Radial) Cam

• Most common type
• Follower moves perpendicular to cam axis

2. Cylindrical Cam

• Has a groove cut on a cylindrical surface
• Produces complex follower motion

3. Translating Cam

• Cam moves linearly instead of rotating

4. Types of Followers

Based on Motion:

• Translating follower – moves in a straight line
• Oscillating follower – rotates about a pivot

Based on Contact Surface:

• Knife-edge follower – simple but high wear
• Roller follower – reduced friction and wear
• Flat-faced follower – better load distribution

5. Follower Motion Types

The motion of the follower is defined during cam design:

• Uniform velocity motion
• Simple harmonic motion (SHM)
• Uniform acceleration and retardation
• Cycloidal motion (preferred for smooth operation)

These motions are analyzed using concepts from Kinematics.

6. Important Terminology

• Base Circle – Smallest circle from cam center tangent to profile
• Prime Circle – Circle passing through pitch point
• Pitch Curve – Path traced by follower point
• Lift (Stroke) – Maximum displacement of follower
• Dwell – Period when follower remains stationary

7. Design Considerations

• Avoid excessive wear and friction
• Ensure continuous contact between cam and follower
• Minimize vibration and noise
• Optimize pressure angle for smooth motion
• Proper material selection and lubrication

8. Advantages

• Produces complex and precise motion
• Compact and simple mechanism
• Suitable for high-speed operations

9. Disadvantages

• High contact stresses
• Wear due to sliding motion
• Requires accurate manufacturing

10. Applications

• Internal combustion engines – valve timing mechanism
• Printing machines
• Textile machinery
• Automatic packaging machines
• Robotics and automation systems