Cams, Types of cams, follower, follower motions

1. Department of Mechanical Engineering
JSS Academy of Technical Education, Bangalore-560060
Kinematics of Machines
(Course Code:17ME42)

2. CONTENTS
DEFINITION, TERMS AND CLASSIFICATION
 Types of cams
 Types of followers
 Displacement Diagrams
 Velocity and Acceleration time curves for cam profiles
FOLLOWER MOTIONS
 SHM
 Uniform Velocity (UV)
 Uniform Acceleration And Retardation (UARM)
 Cycloidal Motion

3. • A cam is a rotating machine element which gives reciprocating or oscillating
motion to another element known as follower.
• Constitute a higher pair (line contact)
• Cam – driver;
• Follower - driven
• The cam normally rotates while the follower may translate or oscillates.
• Kinematic cam design is mainly concerned with the generation of the cam profile.
Cam Introduction

4. • Operating the inlet and exhaust valves of IC engines
• Automatic attachment of machineries
• Paper cutting machines
• Spinning and weaving textile machineries
• Feed mechanism of automatic lathes
Applications
Introduction

5. Classification of Followers
1. According to the surface in contact
(a) Knife edge follower (b) Roller follower
(c) Flat faced or
mushroom follower
(d) Spherical faced follower

6. 2. According to the motion of the follower
Classification of Followers

7. 3. According to the path of motion of the follower
Classification of Followers

8. Classification of Cams
1. Radial or disc cam
• In radial cams, the follower reciprocates or oscillates in a direction perpendicular
to the cam axis.

9. 2. Cylindrical cam
Classification of Cams
In cylindrical cams, the follower reciprocates or oscillates in a direction parallel to
the cam axis.
Note: In actual practice, radial cams are widely used

10. Flat plate cam / linear cam Mechanical paper punch

11. Box cam

12. Eccentric camSnail / Drop cam Swash plate cam

13. Cylindrical Cam / Barrel Cam

14. Disc cam with oscillating follower

15. Cam Nomenclature

16. 1. Trace Point
• Trace point is the theoretical point on the follower, movement of which defines
the motion of the follower.
• Point of the follower that is in contact with the cam at its nearest position.
E.g.: Roller center, knife edge.
2. Base Circle (rb )
• The smallest circle that can be drawn with cam center as the center and touching
the cam profile and is tangential to the cam profile
Cam Nomenclature

17. 3. Pitch curve
• Locus of the roller center which is parallel to the cam profile.
• Locus of the trace point/roller center.
4. Lift or stroke.
• It is the maximum travel of the follower from its lowest position to the top most
position.
Cam Nomenclature

18. 5. Prime circle
• Pitch curve is parallel to the cam profile.
• Circle drawn with cam center as the center and tangential to the pitch circle.
• rp = rb + rr (rr = Roller radius)
6. Offset (e): if cam rotates in counter clock wise direction, the roller will be offset
towards right (+e).
7. Pressure angle (ɸ): The common normal between the roller and the cam profile
passing through the roller center and is normal to the cam
profile.
 Angle between the common normal / contacting force and the follower movement.
Cam Nomenclature

19. Motion of the Follower
1. Uniform velocity (UV)
2. Simple harmonic motion (SHM)
3. Uniform acceleration and retardation (UARM)
4. Cycloidal motion (CM)

20. Displacement diagrams
• Displacement is the distance, that a follower moves during one complete
revolution (cycle) of the cam while the follower is in contact with the cam.

21. Motion of the Follower
1. Uniform velocity (UV)
• Since the velocity is constant, the
displacement diagram will be a straight
line with constant slope.

22. 2. Simple harmonic motion (SHM)
S = Stroke of the follower
O and R = Angular displacement of
the cam during out stroke & return
stroke, in radians.
 = Angular velocity of the cam in
rad/s.
Maximum acceleration of follower on
the outstroke & return stroke,
Maximum velocity of the follower on
the outstroke & return stroke,

23. 3. Uniform acceleration and retardation
(UARM)
Maximum acceleration of follower on
the outstroke & return stroke,
Maximum velocity of the follower on
the outstroke & return stroke,

24. 4. Cycloidal motion (CM)
A cycloid is the curve traced by a point on the rim of a circular wheel as the
wheel rolls along a straight line without slippage.

25. 4. Cycloidal motion (CM)
Radius of rolling circle is S / 2 .
Maximum velocity of the follower on the
outstroke & return stroke,
Maximum acceleration of follower on
the outstroke & return stroke,

26. Scale: 20 = 1cm
Numerical

27. Numerical
Scale: 20 = 1cm

28. End of Module