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ME 114 Engineering Drawing II
Dr. Ouzhan Ylmaz
Assoc.Prof.
Mechanical Engineering
University of Gaziantep
CAM DRAWING
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1
Introduction
A cam is a mechanical device with a surface or groove
that controls the motion of a second part called a follower
in order to convert rotary motion to linear motion (Fig. 1).
Figure 2
Figure 1
The follower, held against the cam by a spring or by gravity,
can be knife, roller, mushroom or flat-faced type (Fig. 2).
Type of follower, timing and manner of movement to be
created by the cam are the main elements in designing cams.
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2
Cam Types
Radial cam: The follower is raised and lowered as the cam revolves (Fig. 3).
Face cam: The follower at the end of an arm oscillates as the
cam revolves (Fig. 4).
Toe (Follower) and Wiper: The cam itself oscillates (Fig. 5).
Figure 3
Positive-Motion Cam (Yoke): The enclosed follower makes
possible the application of force in both directions (Fig. 6).
Cylindrical Groove and End Cams: The follower
moves parallel to the cam axis (Fig. 7). Force is
applied to follower in both directions in groove cam
(left) and in only one direction in end cam (right).
Figure 4 Figure 5 Figure 6
Figure 7
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3
Types of Cam Motion
Cams are designed to move the follower with a
constant velocity, constant acceleration /
deceleration orharmonic motion(from top to
bottom in Fig. 8). In most cases, the combined
motion of follower with rise orfall, or stationary
(dwell) make up the complete cam surface.
In studying the follower motion, a diagram
showing the height of the follower for successivecam positions is frequently employed. These
diagrams are usually made to actual size.
The cam position is shown on the abscissa where
one complete rotation (i.e. 360) of the cam is
divided into equally-spaced intervals, which
are generally 30 although the intermediate
points can also be used. The follower positions
are shown on the ordinate divided into the same
number of intervals as the abscissa.
0 30 60 90 120 150 180 210 240 270 300 360330
1
2
3
4
5
6
1'
2'
3'
4'
5'
6'
1''
2''
3''
4''
5''
6''
Rise (180) Fall (180)
R
R
R
One Complete Revolution (Cycle) of Cam = 360
TotalDisplac
ement
0 30 60 90 120 150 180 210 240 270 300 360330
Rise (180) Fall (180)
One Complete Revolution (Cycle) of Cam = 360
1'
2'
3''
2''
1''
1
4
9
4
10
0
3'''
2'''
1'''
01
4
9
0
1
4
9
0
0
3'
1''''
2''''
3''''
0 30 60 90 120 150 180 210 240 270 300 360330
1
2
3
4
5 6
1'
2'
3'
4'
5'
6'
1''
2''
3''
4''
5''
6''
Rise (180) Fall (180)
One Complete Revolution (Cycle) of Cam = 360
Figure 8
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4
0 30 60 90 120 150 180 210 240 270 300 360330
1
2
3
4
5
6
1'
2'
3'
4'
5'
6'
1''
2''
3''
4''
5''
6''
Rise (180) Fall (180)
R
R
R
One Complete Revolution (Cycle) of Cam = 360
TotalD
isplacement
Constant Velocity
Constant velocity gives a uniform rise and fall as plotted in Fig. 9.
The diagram is constructed by plotting the cam positions on the abscissa, measuring
the total follower movement on the ordinate and dividing it into the same number ofpoints as the abscissa.
As the cam moves one unit of its rotation, the follower likewise moves one unit which
produces the straight line of motion.
Figure 9
The starting and end sections
of the profile are rounded by
fillets of radius which equals
to of total displacement.
This is done due to the
reason that the cam surface
should have smooth transition
during the movement. This
type of motion is called
modified constant velocity.
constant velocitymodified constant velocity
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0 30 60 90 120 150 180 210 240 270 300 360330
Rise (180) Fall (180)
One Complete Revolution (Cycle) of Cam = 360
1'
2'
3''
2''
1''
1
4
9
4
10
0
3'''
2'''
1'''
01
4
9
0
1
4
9
0
0
3'
1''''
2''''
3''''
Constant Acceleration / Deceleration
With constant acceleration or deceleration, the distance travelled is proportional
to the square of the time (i.e. 1, 4, 9, 16, 25, etc.) where the increments of follower
distance are made proportional to 1, 3, 5, 7, etc. as shown in Fig. 10.Using a scale, the rise of follower is divided into the same number of intervals as
the abscissa, making the first part movement as one unit movement, the second
part as three units, and so on.
The points at the intersection of the coordinate lines are then plotted to obtain the
curve which accelerates and then decelerates when rising and falling.
Figure 10
uniform accceleration
uniform deceleration
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Harmonic Motion
Harmonic motion (sine curve) can be plotted as in Fig. 11 by measuring the rise,
drawing a semicircle, dividing it into the same number of intervals as the abscissa,
and projecting the points on the semicircle as ordinate lines.
Points are plotted at the intersection of the coordinate lines.
The swinging action of a mass at the end of a pendulum is a good example of
harmonic motion.
Figure 11
0 30 60 90 120 150 180 210 240 270 300 360330
1
2
3
4
56
1'
2'
3'
4'
5'
6'
1''
2''
3''
4''
5''
6''
Rise (180) Fall (180)
One Complete Revolution (Cycle) of Cam = 360
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Drawing a Cam Profile with Combined Motions
Lets draw a complete drawing of a cam having the following specifications
(The cam is rotating in CCW direction and a roller follower is used)
Base Circle Dia. = 40 mm
Hub Dia. = 20 mm
Shaft Dia. = 10 mm
Plate Thickness = 12 mm
Hub Thickness = 20 mm
Key Way = 2 x 2 mm
Follower Dia. = 6 mm
0 - 60Rise of 12 mm with uniform velocity
60 - 90Dwell
90 - 180Rise of 24 mm with harmonic motion
180 - 210Dwell
at 210Sudden fall of 12 mm
210 - 240Dwell
240 - 360Fall of 24 mm with uniform acceleration
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The Displacement Diagram
The displacement diagram for given cam specifications is shown below.
The circumference is divided into intervals of 30, and the profile of each motion between
specified intervals are plotted. Note that the intervals for harmonic motion are defined as 15.
Then, the intersection points between abscissa and ordinate (shown as A, B, C, etc.) are
connected in order to obtain the complete cam profile.
Figure 12
0 60 90 180 210 360
1
2
3
4
5 6
1'
2'
1
2 2''
3''
4''
5''6''
1''
1
4
9
2'''
3'''
1'''
Circumference = PI * (Base Circle Dia.)
12
24
12
24
dwell harmonic motion dwell uniform accelerationdwelluniform velocity
Base Circle
Cam Profile
240
A
B
C
D
E
F
G
H
J K L
M NP
Q
R
S
0
164'''
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The Cam Drawing
The complete cam drawing is obtained based on the displacement diagram. The ordinate of
each point on displacement diagram is measured and added onto the base circle with a radius
of follower (see the distance of M + follower radius).
Then, the follower circle is plotted having a center point as the end of each ordinate. Note that
the order of placing the points A, B, C, etc. is in CW direction (i.e. the reverse of cam rotation).
After that, the center of
each follower circle is
connected by smoothed
curve to obtain follower
path. This curve is shifted
(i.e. offsetted) towards
the base circle by the
value of radius of follower
in order to obtain the
complete cam surface.
The sectional side view is
also required to show the
plate and hub thickness.
Figure 13
Cam Surface
Follower Path
Base Circle
Hub
Shaft
Key Way
A
B
C
D E FG
H
J
K
LM
N
P
Q
R
S
CamRotatio
n
(CCW)
plate thickness
hub thickness
M+followerradius
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A Case Study Sheet
Base Circle Dia. = 40 mm
Hub Dia. = 20 mm
Shaft Dia. = 10 mm
Plate Thickness = 12 mm
Hub Thickness = 20 mm
Key Way = 2 x 2 mm
Follower Type = Roller
Follower Dia. = 6 mm
Cam Rotation = CCW
0 - 60 Rise = 12 mm
(uniform velocity)
60 - 90 Dwell
90 - 180 Rise = 24 mm
(harmonic motion)
180 - 210 Dwell
at 210 Sudden fall = 12 mm
210 - 240 Dwell
240 - 360 Fall = 24 mm
(uniform acceleration)
0 60 90 180 210 360
1
2
3
4
56
1'
2'1
2 2''
3''
4''
5''6''
1''
1
4
9
2'''
3'''
1'''
Circumference = PI * (Base Circle Dia.)
12
24
12
24
dwell harmonic motion dwell uniform accelerationdwelluniform velocity
Base Circle
Cam Profile
240
A
B
C D
E
F
G
H
JK L
M NP
Q
R
S
0
164'''
Cam Surface
Follower Path
Base Circle
Hub
Shaft
Key Way
A
B
C
D E FG
H
J
K
LM
N
P
Q
R
S
CamRotatio
n
(CCW)
plate thickness
hub thickness
M+followerradius
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Timing Diagrams
When two or more cams are used on the same machine and their functions are
dependent on each other (as in Fig. 14), the 'timing" and relative motions of each
cam can be studied by means of a diagram showing each follower curve.
The curves can be superimposed, but it is better to place them as in Fig. 15.
Figure 15Figure 14