Technical Terms used in CAM II

• Motions of follower
• Simple harmonic motion
• Constant acceleration and deceleration
• Constant velocity
• Cycloidal Motion

• Simple harmonic motion: In this type of motion there is an abrupt change of acceleration from zero to maximum at the beginning of the follower motion and also from maximum negative to zero at the end of follower motion when the follower rises. Similar abruption would also be there at the start and end of the return motion. As these abrupt changes result in infinite jerk, vibration and noise etc. The programme should be adopted only for low or moderate cam speeds.
• Constant Acceleration and Deceleration: In such a follower programme, there is acceleration in the first half of the follower motion whereas it decelerates during the later half. The magnitude of the acceleration and deceleration is the same and constant in two halves.
• Constant velocity: Constant velocity of the follower implies that the displacement of the follower is proportional to the cam displacement and the slope of displacement curve is constant.

Cycloidal motion: A cycloid is the locus of a point on a circle rolling without slipping on a straight line. In this there are no abrupt changes in the velocity and the acceleration at any stage of the motion, thus it is the most ideal programme for high-speed follower motion.

Cams with specified contours:

• Tangent cam
• Circular arc cam

Tangent cam: When the flanks of the cam are tangential to base circle and nose circle then the cam is known as tangent cam. These cams are usually symmetrical about the central line of camshaft. These types of cams are used to operate inlet and exhaust valves of internal combustion engine.

circular arc cam: When the flanks of the cam connecting the base circle and nose are of convex circular arcs , then the cam is known as circular arc cam.