Motions
MACHINE ELEMENTS 2
Cams
➢ Cam is a link having an irregular surface or groove that imparts motion to a follower ➢ Cams are very important and frequently occurring elements in many types of machines – especially AUTOMATIC MACHINES ➢ Cams are the heart of such automatic devices as automatic devices as automatic machine tools, record changers, mechanical calculators, cash registers, and many other devices.
Types of Cams:
Motions Used for Cam Followers:
➢ The motion of the follower is of primary interest in the analysis of existing cams or in the design of new cams. ➢ It is easier to analyze the motion of cam followers if their motion is plotted as a graph often referred to as DISPLACEMENT DIAGRAM
A. Displacement Diagram
B. Motions that are most commonly used:
1. Uniform Velocity (straight line) motion – UVM 2. Simple Harmonic Motion – SHM 3. Uniformly Accelerated motion (Parabolic Motion) – UAM or PM 4. Modified Uniform-Velocity Motion – MUVM a. Arc method – MUVM-Arc b. Uniform Acceleration Method – MUVM-UAM 5. Cycloidal Motion – CM
A. Uniform Velocity Motion (Straight Line Motion)
If the follower is to move with uniform velocity, its displacement must be the same for equal units of time.
Its curve in the displacement diagram, therefore, is a STRAIGHT LINE.
Example 1:
Lay out the displacement diagram for a cam follower that is to have the following motions: Dwell 30O (at rest) Rise 2 inches in 90O (uniform velocity) Dwell 30O Fall 2 inches in 60O (uniform velocity) Dwell 150O
B. Simple Harmonic Motion (SHM)
As a point moves around the circumference of a circle with a constant velocity, its projection on the diameter of the circle moves with simple harmonic motion.
How to plot in
Cams
➢ Cam is a link having an irregular surface or groove that imparts motion to a follower ➢ Cams are very important and frequently occurring elements in many types of machines – especially AUTOMATIC MACHINES ➢ Cams are the heart of such automatic devices as automatic devices as automatic machine tools, record changers, mechanical calculators, cash registers, and many other devices.
Types of Cams:
Motions Used for Cam Followers:
➢ The motion of the follower is of primary interest in the analysis of existing cams or in the design of new cams. ➢ It is easier to analyze the motion of cam followers if their motion is plotted as a graph often referred to as DISPLACEMENT DIAGRAM
A. Displacement Diagram
B. Motions that are most commonly used:
1. Uniform Velocity (straight line) motion – UVM 2. Simple Harmonic Motion – SHM 3. Uniformly Accelerated motion (Parabolic Motion) – UAM or PM 4. Modified Uniform-Velocity Motion – MUVM a. Arc method – MUVM-Arc b. Uniform Acceleration Method – MUVM-UAM 5. Cycloidal Motion – CM
A. Uniform Velocity Motion (Straight Line Motion)
If the follower is to move with uniform velocity, its displacement must be the same for equal units of time.
Its curve in the displacement diagram, therefore, is a STRAIGHT LINE.
Example 1:
Lay out the displacement diagram for a cam follower that is to have the following motions: Dwell 30O (at rest) Rise 2 inches in 90O (uniform velocity) Dwell 30O Fall 2 inches in 60O (uniform velocity) Dwell 150O
B. Simple Harmonic Motion (SHM)
As a point moves around the circumference of a circle with a constant velocity, its projection on the diameter of the circle moves with simple harmonic motion.
How to plot in