CAM
- 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:
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.
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.