Short Answer:

A follower displacement diagram is a graphical representation that shows how the displacement of the follower changes with respect to the rotation of the cam. It illustrates the rise, dwell, and return periods of the follower motion during one complete revolution of the cam.

This diagram helps in designing the shape of the cam profile accurately. It ensures that the follower moves smoothly without jerks or sudden changes in velocity and acceleration. The diagram is essential for understanding and controlling the motion characteristics of the cam-follower mechanism.

Detailed Explanation :

Follower Displacement Diagram

A follower displacement diagram is one of the most important tools used in cam design. It represents the motion of the follower in relation to the angular position of the cam. In simple terms, it is a plot that shows how much the follower moves (displacement) for every degree of cam rotation. This diagram helps engineers to visualize the follower motion throughout the cam’s cycle and design the cam profile accordingly.

The follower displacement diagram is drawn on a graph where:

• The horizontal axis (x-axis) represents the angle of cam rotation.
• The vertical axis (y-axis) represents the displacement of the follower from its lowest position.

This diagram helps to plan and control the follower’s motion in different stages such as rise, dwell, and return, ensuring smooth performance and longer machine life.

1. Purpose of Follower Displacement Diagram

The main purpose of the follower displacement diagram is to show how the follower moves during one full rotation of the cam. It helps in:

• Understanding the follower’s motion pattern.
• Designing the correct cam profile.
• Avoiding sudden acceleration and deceleration of the follower.
• Ensuring smooth operation of the cam-follower mechanism.
• Analyzing the timing of machine parts like valves, levers, or hammers.

It also helps in deciding the duration of each motion stage — how long the follower will rise, stay still (dwell), and return.

2. Construction of Follower Displacement Diagram

The follower displacement diagram is constructed using the following steps:

1. Draw a horizontal line and mark it as the base line representing one complete revolution of the cam (360°).
2. Divide this base line into angular divisions to represent different parts of motion — rise, dwell, and return.
3. On the vertical axis, represent the displacement of the follower.
4. Plot the displacement values for each angle based on the desired motion (uniform velocity, simple harmonic motion, or uniform acceleration and retardation).
5. Join the plotted points smoothly to form the displacement curve.

The shape of the curve depends on the type of follower motion selected. The smoother the curve, the smoother the cam operation will be.

3. Types of Motion Shown in Displacement Diagram

The follower displacement diagram can be based on different types of motion laws, depending on the application. The most common types are:

• Uniform Velocity Motion:
  The follower moves upward or downward with a constant velocity. The displacement diagram forms a straight line during the rise and return. This motion is simple but not very smooth because of sudden changes at the start and end.
• Simple Harmonic Motion (SHM):
  In this motion, the follower accelerates and decelerates smoothly following a sine curve pattern. The displacement diagram forms a smooth curve, which makes it suitable for high-speed machines.
• Uniform Acceleration and Retardation:
  In this motion, the follower accelerates uniformly during the first half of the rise and decelerates uniformly during the second half. The displacement curve is parabolic in shape and gives smooth operation with minimal shock.
• Cycloidal Motion:
  The follower moves in a cycloidal path, providing the smoothest motion with minimum jerk. This is often used in precision and high-speed machinery.

Each type of motion law has a different displacement curve, and the choice depends on the required performance of the mechanism.

4. Representation of Rise, Dwell, and Return

In the follower displacement diagram:

• Rise is shown as an upward curve or slope, representing the lifting of the follower.
• Dwell is shown as a horizontal line, where the follower displacement remains constant.
• Return is shown as a downward curve, representing the follower moving back to its initial position.

The angular extent of each portion (rise, dwell, return) depends on how long the follower must perform each motion during one cam revolution. These parts together form the complete motion cycle.

5. Importance in Cam Design

The follower displacement diagram plays a key role in cam design because it acts as the foundation for generating the cam profile. Without this diagram, it would be very difficult to ensure proper timing and smooth motion of the follower.

Some important advantages are:

• It allows visualization of the follower motion before actual cam design.
• It helps to determine velocity and acceleration curves from the displacement data.
• It ensures that the cam profile generated will provide desired motion with minimum vibration.
• It aids in balancing performance and mechanical strength requirements.

Therefore, every cam-follower design starts with constructing the follower displacement diagram.

Conclusion

In summary, a follower displacement diagram is a graphical representation showing how the follower moves in relation to the cam’s rotation. It clearly indicates the rise, dwell, and return periods during a complete revolution of the cam. This diagram is the foundation for designing cam profiles and analyzing follower motion. A well-prepared displacement diagram ensures smooth, efficient, and accurate operation of the cam-follower mechanism, which is essential in engines, automation systems, and mechanical tools.