• Abhi Shejul

Cam and go!

What is the mechanical way to switch on/off something at a desired interval of time?

Table of Contents

Introduction

Definition

Displacement diagram

Types of Cam

Disc or plate cam

Cylindrical cam

Face cam

Linear cam

Applications of cam


We all have sometime in our life driven a bicycle with deformed wheel. That rocking motion like going up and down a roller coaster. What was happening here? The wheel of the bicycle was in somewhat oval shape, which means the radius had become uneven and hence causing the rocking motion. But if you rode the bike for a longer time you would notice that there was a pattern in that rocking motion.


Well, this motion accurately represents a cam. Now let us take a look at what is a cam?

 

Definition:

A cam is a mechanical equipment which is used to convert a rotatory motion into linear motion. It is most commonly used in assemblies of rotating or sliding pieces.

 

Displacement Diagram:


It is possible to describe cams by their displacement diagrams, which give insight into the changes in position a follower would experience as the cam surface moves in contact with the follower. The diagram shows the cam rotating about it's axis. These graphs connect an angle, which is often expressed in degrees, to the radial displacement that is felt at that angle. Traditionally, displacement diagrams have been displayed as graphs with non-negative values. The follower motion at a constant velocity climb, followed by a similar return with a rest in between, is depicted by a straightforward displacement diagram. The follower moves in three different directions: away from the cam centre (the rise), at rest (the dwell), and back toward the cam centre (the return).



 

Types of Cam

Let us not take a look at what are the different types of cams.


Disc or plate cam

Cam plate which is also know as disc or radial cam is one of the most commonly used cams. This cam is a cut out of flat metal or plate.

In this instance, the follower moves in a plane that is perpendicular to the camshaft's axis of rotation. Base circle, prime circle (whose radius is equal to the sum of the follower radius and the base circle radius), pitch curve (which is the radial curve formed by applying the radial displacements away from the prime circle across all angles), and lobe separation angle are a few key terms that are important in this construction of plate cams (LSA - the angle between two adjacent intake and exhaust cam lobes).


Application: This kind of cam is used to activate mechanical switches that control various sections of many simple electromechanical appliance controllers.


Cylindrical cam

A cam in which the follower rides on the surface of a cylinder is known as a cylindrical cam or barrel cam. The follower rides in a groove carved into the surface of a cylinder in the most typical type. These cams are mostly employed to transform rotational motion into linear motion parallel to the cylinder's rotating axis. A cylinder can drive many followers through a number of grooves carved into its surface. In general, cylindrical cams give positive placement and can produce motions involving more than one rotation of the cylinder, negating the need for a spring or other mechanism to maintain the follower's contact with the control surface.

Application: Applications include shift control barrels in sequential transmissions, such as those found on the majority of contemporary motorbikes, and machine tool drives, such as reciprocating saws.


Face cam

A follower riding on the disk's face is how a face cam creates motion. The most typical design allows the follower to ride in a slot, producing radial motion with positive placement without the use of a spring or other device to maintain the follower's contact with the control surface. This kind of face cam typically just has one follower slot on each face. A single component, such as a gear, a barrel cam, or another rotating device having a flat face, may serve as a face cam in addition to serving other functions in some situations.


Linear cam

A linear cam is one during which the cam part moves in an exceedingly line instead of rotates. The cam element is usually a plate or block however_could also be any cross-section. The key feature is that the input may be a linear motion rather than rotational. The cam profile could be withdraw one or additional edges of a plate or block, may be one or more slots or grooves within the face of an element, or may even be a surface profile for a cam with over one input. the event of a linear cam is comparable to, but not identical to, that of a rotating cam.


 

Application of cam

  • One of the most common application found in any household is in the wall clock. The swinging pendulum we see receives a periodic jerk every minute via a disc cam.

  • The machine application include feed mechanism in an automatic lathe machine, screw and gear cutting machinery.

  • In any hydraulic system cams are used as primary mechanism.

  • Cam assembled on a shaft - cam shaft - is used in IC Engines. The cam shaft controls the fuel intake and output valves.


 

This is just an introduction to what cams are and what are their advantages. Stay tuned on Mech n Flow to understand the in-depth concept of cams and followers.

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