Kinematics of Cam

Chapter: 3

Kinematics of Cam

Learning Objectives

• While reading and after studying this chapter, you will be able to:

• Classify the cam followers according to their shape, location and motion.

• Understand and explain the various terminologies used in the study of cam.

• Sketch and compare the displacement, velocity and acceleration diagrams for uniform velocity, uniform acceleration and retardation, simple harmonic motion and cycloidal motion, used in cam mechanisms.

• Construct the displacement diagram and the cam profile for the given follower motion.

• Construct the tangent cam and the circular arc cam.

• Describe the effect of pressure angle in a cam-follower system.

• Brief the phenomenon of undercutting in cam mechanisms.

SYLLABUS

Classification of cams and followers – Cam nomenclature – Displacement diagram - Derivatives of follower motions - Layout of plate cam profiles – Circular arc and tangent cams.

INTRODUCTION

• A cam is a rotating mechanical member used for transmitting desired motion to a follower by direct contact.

• The cam may be reciprocating, rotating or oscillating whereas the follower may be reciprocating or oscillating.

• It is one of the most convenient means of producing movements of an irregular or complex character not easily obtained by linkages.

• The cam and follower have a line contact and hence constitute a higher pair.

• Cam mechanisms are extensively used in the operation of many classes of machines such as for operating valves in internal combustion engines, in printing machinery, automatic screw machines, gear cutting machines, stamp mills, paper cutting machines, spinning and weaving textile machineries, etc.

• Cams are manufactured usually by die-casting, milling or by punch-presses.

• The three necessary elements of a cam mechanism are:

1. Cam: The driving member is known as the cam.

2. Follower: The driven member is known as the follower.

3. Frame: It supports the cam and guides the follower.