Subject: Kinematics of Machinery

Topic: CAM Mechanism

Difficulty: High

The pressure angle represents the steepness of cam profile, is the angle between the normal to the pitch curve at a point and the direction of the follower motion. It varies in magnitude at all instants of the follower motion. A high value of the maximum pressure angle is not desired as it might jam the follower in the bearings.

The image above displays it by showing the various follower positions and keeping the cam constant. But in actual conditions, it’s the other way around (usually).

From the definition, you can see that the pressure angle is dependent on the direction of motion and the cam profile. The direction of motion of translatory cams (which have a reciprocative motion) is considered as a straight line along the follower axis and is constantly the same even though such is not the case in oscillatory cams. But ultimately, the purpose of a cam is to get the desired motion using the cam and follower mechanism. Hence the direction of motion cannot be changed.