Basic terminology of cam

1. Cam

2. Terminology in Cam

3. Cam Nomenclature
Cam Profile: Working
surface of cam which comes
in contact with follower
while transmitting motion, is
called cam profile.
Base circle: It is the smallest
circle that can be drawn
from the axis of rotation of
cam and tangent to the cam
profile.

4. Trace point: It is a reference point
on the follower and is used to
generate the pitch curve.
In case of knife edge follower,
the knife edge represents the
trace point. In a roller follower,
the centre of the roller
represents the trace point. For
flat faced follower, trace point is
the point of contact at the time
hen follower is in contact ith cam
on base circle.
Pressure angle: It is the angle
between the direction of the
follower motion and a normal to
the pitch curve. It represents
steepness of the cam profile.
Cam Nomenclature

5. Pressure angle = α = 0 (fig. A)
= 450 (fig.B)
Fig.A
45°
Fig.B
80°
80°
20°
180°
Pressure angle

6. Pressure angle

7. Influence of off-set on pressure angle
45°
80°
80°
20°
180°
26°
Pressure angle
decreases with
off set as shown
in figure

8. Cam Nomenclature
Pitch point: It is a point on the
pitch curve having the
maximum pressure angle.
Pitch circle: It is a circle drawn
from the centre of the cam
through the pitch points.
Pitch curve: It is the curve
generated by the trace point as
the follower moves relative to
the cam.
For a knife edge
follower, the pitch curve and
the cam profile are same
whereas for a roller follower,
they are separated by the
radius of the roller.

9. Cam Nomenclature
Prime circle: It is the smallest
circle that can be drawn from
the centre of the cam and
tangent to the pitch curve.
For a knife edge and a
flat face follower, the prime
circle and the base circle are
identical. For a roller follower,
the prime circle is larger than
the base circle by the radius
of the roller.
Lift or stroke: It is the
maximum travel of the
follower from its lowest
position to the topmost
position.

10. Angle of ascent: Angle turned by the cam during
outward stroke (ascent) of the follower.
Angle of descent: Angle turned by the cam during
the inward stroke (return/descent) of the follower.
Angle of dwell: Angle turned by the cam during no
movement of the follower.
Angle of action: Angle turned by the cam from the
beginning of the outward stroke of the follower till
the end of the return stroke.
Cam Nomenclature

11. As the cam rotates the follower moves upward
and downward.
•The upward movement of follower is called rise
(Out stroke)
• The downward movement is called fall (Return
stroke).
•When the follower is not moving upward and
downward even when the cam rotates, it is called
dwell.
Cam Nomenclature