Cam and Follower Experiment – Apparatus, Procedure and Displacement Diagram

Aim of the Experiment

To study the profile of different types of cams and to trace the displacement, velocity, and acceleration diagrams for a given cam and follower system.

Apparatus Required

• Cam and follower apparatus (with interchangeable cam profiles)
• Different cam types: circular, tangent, eccentric, cycloidal, harmonic
• Follower types: knife-edge, roller, flat-faced, spherical
• Graph paper and pencil
• Dial gauge or displacement sensor

Theory

A cam is a rotating or sliding piece in a mechanical linkage used to convert rotary motion into linear motion of the follower. The shape of the cam profile determines the motion characteristics of the follower.

Types of follower motion:

• Uniform Velocity (UV): Follower moves at constant speed, acceleration is zero except at the beginning and end (infinite impulse).
• Simple Harmonic Motion (SHM): Displacement follows a sine curve, smooth acceleration and deceleration.
• Uniform Acceleration and Deceleration (UAMD): Follower accelerates uniformly for the first half of the stroke, then decelerates uniformly.
• Cycloidal Motion: Minimum jerk, used for high-speed cams as it minimises dynamic forces.

Procedure

1. Mount the required cam profile on the apparatus.
2. Select the appropriate follower type and mount it in the guide.
3. Rotate the cam slowly by hand or at low motor speed.
4. Record the follower displacement for every 10° or 15° of cam rotation (0° to 360°).
5. Plot the displacement diagram (displacement vs. cam angle).
6. Differentiate the displacement curve graphically to obtain the velocity diagram.
7. Differentiate the velocity curve to obtain the acceleration diagram.
8. Repeat for different cam profiles and compare the motion characteristics.

Observation Table

Result

The displacement, velocity, and acceleration diagrams for the given cam and follower system have been plotted. Cycloidal motion gives the smoothest acceleration curve with zero jerk at the beginning and end of the stroke.

Internal Links

Related resources: Theory of Machines Lab Equipment | Dynamic Balancing Experiment | Governor Apparatus Experiment | Theory of Machines Lab Setup Guide

Cam and Follower Experiment, Complete Procedure and Displacement Diagram Construction

Types of Cams and Followers

Standard Follower Motions

Uniform velocity (UV): Follower rises at constant speed. Displacement is proportional to cam angle. Acceleration is zero during motion but infinite at the beginning and end, causes jerk and impact.

Simple harmonic motion (SHM): Displacement follows x = h/2 × (1 – cos(πθ/β)). Acceleration = (π/β)² × h/2 × cos(πθ/β). Smoother than UV, commonly used.

Uniform acceleration and retardation (UARM): First half of lift: constant acceleration; second half: equal constant retardation. Minimum peak acceleration for a given lift and period.

Cycloidal motion: Displacement = h[θ/β – (1/2π)sin(2πθ/β)]. Zero acceleration at beginning and end, smoothest motion, used in high-speed machinery.

Experiment Procedure

1. Mount the test cam (select type: circular, tangent, or SHM profile) on the apparatus spindle.
2. Select the follower type (knife-edge, roller, or flat-faced).
3. Set the dial gauge to measure follower displacement. Zero the gauge at the lowest follower position (base circle).
4. Rotate the cam slowly by hand, recording follower displacement every 10° or 15° of cam rotation using the protractor on the spindle.
5. Record observations in the table.
6. Plot the displacement diagram (cam angle on x-axis, follower displacement on y-axis).
7. From the displacement diagram, construct velocity and acceleration diagrams using graphical differentiation.
8. Repeat with a different cam profile or follower type.

Observation Table