KOM CAM AND FOLLOWER kinematics

1. Kinematics of machine
CAM and FOLLOWER

2. Sub Topics
Classification and terminology of cams and followers,
Different motions of the follower.
Displacement Diagrams,
Cam profiles for radial and offset followers,
Cams with specified contours - tangent cam with reciprocating
roller follower,
Circular arc cam with flat faced follower,
Graphical construction of cam profile.

3. INTRODUCTION
A cam is a mechanical device used to transmit motion
to a follower by direct contact.
The driver is called the cam and the driven member is
called the follower.
In a cam follower pair, the cam normally rotates while
the follower may translate or oscillate.
A familiar example is the cam shaft of an automobile
engine, where the cams drive the push rods (the
followers) to open and close the inlet exhaust valves in
synchronization with the motion of the pistons.

7. CAM
Follower

8. Question 1:
Discuss Terminology Used In Cam

9. ANSWER:
Fig. shows a
radial cam with
reciprocating
roller follower.
(1) Base Circle:
It is the
smallest circle
that can be
drawn to then
cam profile.

10. (2) Trace Point:
It is a reference
point on the
follower and is
used to generate
the pitch curve
(3) Pitch curve: It
is the curve
generated by the
trace point as
the follower
moves relative to
the cam

11. (4) Prime circle: It is the smallest circle that can be drawn from the center
of the cam and tangent in the pitch curve
Prime circle radius = Base circle radius for knife edge and flat faced
follower
Prime circle radius = Base circle radius + radius of roller for roller follower

12. (5) Lift or stroke: It is the maximum of the travel follower from its lowest
position to the topmost position.
(6) Pitch point: It is a point on the curve having maximum pressure
angle
(7) Pitch circle: It is a circle drawn from the centre of the cam though the
pitch points.
(8) Pressure angle: It is the angle between the direction of the follower
motion and a normal to the pitch curve
(9) Cam Profile: The contour of the working surface of the cam

13. Question 2:
CLASSIFICATION OF
THE FOLLOWER:
(A)
ACCORDING TO
SHAPE:- The follower is
classified as,
(1) Knife edge follower
(2) Roller follower
(3) Flat faced or
mushroom follower
(4) Spherical follower.

15. Knife- edge follower:
When the end of a follower which is in contact with cam has a sharp
knife-edge, it called a knife edge follower The sliding motion takes place between
the contacting surfaces i.e. the knife-edge and the cam surface. This cam is not of
much use as excessive wear occurs at the contacting surface.
Roller follower:
When the end of the follower is a roller the follower is termed as roller
follower. Here notice to be made that at the contact surface the rolling motion is
taking place; hence rate of wear is reduced. In both the knife edge & roller
follower side thrust exists between the follower and the guide. Roller follower is
extremely used where more space is available such as in stationary gas engines
Oil engines and also in Aircraft engines.

16. Flat faced or mushroom follower:
When the contacting end of the follower is a perfectly flat face, it is called a
flat-faced follower .Side thrust between the follower & the guide is much
.reduced in case of flat-faced follower. Relative motion between the contacting
surfaces is mostly of sliding nature but wear may be reduced by offsetting the
axis of the follower. They are generally used where space is limited such as in
cams used in valve mechanism of automobile engines.
Spherical faced follower:
When the shape of a surface which is in contact with the cam is spherical, the
follower is known as Spherical faced follower .The flat end of the follower is
machined to a spherical shape in order to minimize high surface stresses
produced during operation.

17. (B) ACCORDING TO THE MOTION OF THE FOLLOWER:-
The follower are classified as,
(1) Reciprocating translating follower
(2) Oscillating or rotating follower.

18. (C) ACCORDING TO LOCATION
OF LINE OF MOVEMENT:-
(1) Redial follower: If the line
movement of the follower passes
through the centre of rotation of the
cam, the follower is known as a radial
follower.

19. (2) Offset follower: If the line
of movement of the roller
follower is offset from the center
of rotation of the cam, the
follower is known as an offset
follower

20. TYPES OF MOTION OF THE FOLLOWER:
(1) Simple harmonic motion.
(2) Constant acceleration and deceleration.
(3) Constant velocity.
(4) Cyclonical motion.

21. Outstroke= Rise Of Follower
1. Simple harmonic motion.

24. 2. Uniform velocity

27. Problem 1
Draw the cam profile for following conditions:
For Radial follower,
Follower type = Knife edged, in-line;
lift = 50mm;
base circle radius = 50mm;
out stroke with SHM for 600 cam rotation;
dwell for 450cam rotation;
return stroke with SHM for 90ocam rotation;
dwell for the remaining period.

28. X axis: 1 cm = 200
Y Axis: 1 cm = 10 mm
Solution:
Follower rise return with Simple Harmonic Motion

30. Problem 2:
Draw the cam profile for following conditions:
Follower type=knife edge d follower, in line;
lift=30mm;
base circle radius =20mm;
outstroke with uniform velocity in 120°of cam rotation;
dwell for 60°;
return stroke with uniform velocity during 90°of cam rotation;
dwell for the remaining period.

31. X axis: 1 cm = 200
Y Axis: 1 cm = 10 mm
Solution:
Follower rise return with Uniform Velocity

33. Problem 3:
Draw the cam profile for following conditions:
For Radial follower,
Follower type = Knife edged, in-line;
Stroke of follower = 40mm;
base circle radius = 50mm;
Follower rise with Uniform Velocity for 600 cam rotation;
dwell for 300cam rotation;
return stroke with Uniform Velocity for 60ocam rotation;
dwell for the remaining 2100 period.
Axis of the follower offset by 20 mm to the right of cam center.

34. X axis: 1 cm = 200
Y Axis: 1 cm = 10 mm
Solution:
40 mm
600 300 600 2100
Rise
Return
Follower rise return with Uniform Velocity

35. 20mm offset
600
300
600

36. Problem 4:
Draw the cam profile for following conditions:
Follower type = roller follower, in-line; lift =
25mm; base circle radius = 20mm; roller radius =
5mm; out stroke with Uniform acceleration and
retardation, for 1200 cam rotation; dwell for
600 cam rotation; return stroke with Uniform
acceleration and retardation , for 900 cam
rotation; dwell for the remaining period.

37. Displacement Diagram

38. CAM Profile

39. Problem 5:
Follower type = flat faced follower, inline;
follower rises by 20mm with SHM in 120° of cam
rotation, dwells for 30° of cam rotation; returns
with SHM in 120° of cam rotation and dwells
during the remaining period. Base circle radius
=25mm.

42. Cam displacement diagram for cycloidal motion