Today we will learn about cam terminology and its displacement diagram. A cam is a mechanical member used to impart desired
motion or displacement to a follower by direct contact. It is widely used in automobile industries to
direct opening and closing of inlet and exhaust valves at desire time. Cams are
either in rotary or reciprocating or oscillating motion. The driver member in
cam follower mechanism is called cam and driven member is called follower. Cam
mechanism belong to higher pair mechanism because the cam and follower makes
point contact. When we study about cam follower mechanism, some common
terminology like prime circle, base circle, pressure angle etc. are used to
describe a cam. These are as follow.
Cam Terminology and Displacement Diagram:
Terminology:
Base Circle:
Base circle is the smallest circle that can be drawn
tangentially to the cam profile.
Trace Point:
A trace point is a theoretical point on the follower. It’s
motion describing the movement of the follower. For example a knife edge
follower, the trace point is at the knife edge.
Pitch Curve:
It is the curve drawn by the trace point assuming that the
cam is fixed and the trace point of the follower rotates around the cam.
Pressure Angle:
It represents the steepness of the cam profile. The angle
between the direction of the follower movement and the normal to the pitch
curve at any point is called pressure angle.
Pitch Point:
A pitch point correspond to the point of maximum pressure
angle. Its
Pitch Circle:
A circle drawn with its center at the cam center and pass
through the pitch point is known as the pitch circle.
Prime Circle:
The prime circle is the smallest circle that can be drawn
from the center of cam and it is tangential to the pitch curve.
Displacement Diagram:
Angle of Ascent:
It is the angle through which the cam turns during the time
the follower rises.
Angle of Dwell:
Angle of dwell is the angle through which the cam turns
while the follower remains stationary at the highest or the lowest point.
Angle of Descent:
Angle of descent is the angle through which the cam turns
while follower returns to the initial position.
Angle of Action:
This is the total
angle moved by the cam during the time between the beginning of rise and the
end of return of the follower.
These are basic terminology used in cam and and follower
mechanism and its displacement diagram. If you have any query regarding this article, ask by commenting. If
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