Cam and Follower
A cam and follower mechanism is a profiled shape mounted on a shaft that causes a lever or follower to move. Cam and follower are used to convert rotary motion into linear (reciprocating) motion. As the cam rotates, the followers rise and fall in a process known as reciprocating motion.
A cam is a reciprocating, oscillating, or rotating body that imparts reciprocating or oscillating motion to a second body, called the follower, with which it is in contact. The shape of the cam depends upon its own motion, the required motion of the follower, and the shape of the contact face of the follower.
The working principle of Cam and Followers depends on the mechanism of the combination of both Cam and Followers.
Cam and Follower Terminology
When we study about cam follower mechanism, some common terminology like a prime circle, base circle, pressure angle, etc. are used to describe a cam.
- Cam Profile: Cam profile is the outer surface of the disc cam.
- Base Circle: The base circle is the smallest circle, drawn tangential to the cam profile.
- Trace Point: Tracepoint is a point on the follower, tracepoint motion describes the movement of the follower.
- Pitch Curve: Pitch curve is the path generated by the tracepoint as the follower is rotated about a stationary cam.
- Pitch Point: Pitch point corresponds to the point of maximum pressure angle.
- Prime Circle: This is a circle that drawn tangentially to the pitch curve and concentric to the base circle.
- Pitch Circle: A circle drawn from the cam center and passes through the pitch point is called a Pitch circle.
- Pressure Angle: The pressure angle is the angle between the direction of the follower movement and the normal pitch curve.
What is Cam Mechanism?
A cam is a rotating or sliding piece in a mechanical linkage, which is used in particular to convert a rotary motion into a linear motion. It is often part of a rotating wheel (e.g. an eccentric wheel) or a shaft (e.g. a cylinder with an irregular shape) that hits a lever at one or more points on its circular path.
The cam can be a simple tooth, such as is used to give pulses of power to a steam hammer, or an eccentric disc or other shapes that allow a gentle reciprocating motion in the follower, which is a lever making contact with the cam.
A cam timer is similar and was widely used to control electrical machines before the advent of inexpensive electronics, microcontrollers, integrated circuits, programmable logic controllers, and digital controls (an electromechanical timer in a washing machine is a common example).
For the smooth functioning of a cam-follower mechanism, it is imperative that the follower should move smoothly without requiring too much input power, which means the follower should not jam, during its movement.
In an IC engine the valves have to be kept open; first, then close it and keep it closed, all these timing operations can be easily set by having cam-follower mechanisms. In the case of linkages, we study planar linkages or two- dimensional linkages, and more.
Types of Cam
There are many types of cams describe below:
- Disk or Plate cam.
- Cylindrical cam.
- Translating cam.
- Wedge cam.
- Spiral cam.
- Heart-shaped cam.
- Conjugate cam
- Globoidal Cams
- Spherical cam
1. Disk or Plate Cam
The disc (or plate) cam has an irregular contour to provide a specific motion to the follower. The follower rotates in a plane that moves on the axis of rotation of the camshaft and place in contact with the cam by springs or gravity.
2. Wedge Cam
The wedge cam has an angled flat regular contour to impart a specific motion of the follower.
3. Spiral Cam
The spiral cam consists of a semi-circular or a spiral that shapes the Grooved contour, the cam moves in a reciprocating motion and the follower moves perpendicular to the axis of the cam.
4. Cylindrical Cam
The cylindrical cam has a groove cut along its cylindrical surface. The roller follows the groove, and the follower moves in a plane parallel to the axis of rotation of the cylinder.
5. Heart-shaped Cam
This type of cam looks like an asymmetric heart. It is mainly used to return a shaft to hold the cam to a set position by its pressure from a roller.
6. Translating Cam
The translating cam is a contoured or grooved plate sliding on a guiding surface(s). The follower may oscillate or reciprocate. The contour or the shape of the groove is determined by the specified motion of the follower.
7. Conjugate cam
In these types two discs connect to each other and the axes of discs are offset by the distance, to form a cam profile. The follower has surface contact with a cam profile by two rollers. As the cam rotates followers follow it.
8. Globoidal Cams
Globoidal cam is a shaft and has a concave or convex circumference. On which groove is made by machining and this groove use for giving movement to the follower. Globoidal cam use for oscillating followers about a fixed point.
9. Spherical cam
Spherical cam is in the form of spherical shape on which groove is made. The follower has surface contact with this groove. As cam rotate follower oscillates about a fixed point.
Types of Cam according to follower movement
In these category types of the cam is classified as per the movement of follower. The movement of follower is depending upon the cam profile for this; cams are also classified according to follower movement.
1) Dwell Rise Dwell Return Dwell cam
In this type, follower movement is considering. As per name follower movement is done in a way that first dwells then rise again dwell then return and again dwell. This all process is done in one rotation (360 degrees) of the cam.
2) Dwell Rise Return Dwell cam
In this type, follower movement is considering. As per name follower movement is done in a way that first dwells then rises then returns and again dwells. This process is done in one rotation (360 degrees) of the cam.
3) Rise Return Rise cam
In this type, follower movement is considering. As per name follower movement is done in a way that first rises then returns. This all process is done in one rotation (360 degrees) of the cam.
4) Dwell Rise Dwell cam
In this type, follower movement is considering. As per name follower movement is done in a way that first dwells then rise then again dwell. This process is done in one rotation (360 degrees) of the cam. And at 360 degrees it suddenly falls to its first position.
Types of Cam according to the constraint of the follower
For proper functioning of the cam and follower mechanism, it is important to keep the surface contact between the cam profile and the follower at all times of rotation and any motion. For this, spring force, gravitational force, or positive drive are used in the cam and follower mechanism. On this basis, cams are classified based on the type of follower and are as follows.
1) Preloaded spring cam:
In this type of cam, the spring force is used. The compression spring is preloaded into followers in such a way that it maintains surface contact all time.
2) Positive drive cam:
This type of cam, it does not require any external force. The follower is designed in such a way that it does not require any external force.
What is the Follower Mechanism?
A follower is a rotating or oscillating element of a machine that follows the motion of the cam by direct contact.
A follower is a mechanical component concerning which, the Cam rotates in an oscillatory or circular motion. Follower inhibits the push and pulls of the Cam. A follower is used to transfer the motion to the required machine part. The Follower rotates in an oscillating or circular arc.
A follower is a translating or oscillating mechanical member that follows the motion of the cam. It can touch the surface profile of the cam or can be spring-loaded. It can have a uniform velocity or can have uniform acceleration motion. Complicated output motion can be achieved with the help of the follower motion.
The mechanism for Cam and the mechanism for Followers depend upon each other so that the main mechanism of Cam and Followers. The mechanism is essential in the engineering field and has many different functions for the different machines.
Types of Follower
There are different types of surface contact between cam and follower and according to surface contact they are classified as follows:
- Types of follower according to Shape
- Types of follower according to Movement
- Types of follower according to the line of movement
Types of follower according to Shape
1) Knife-edge Follower
This type of follower has a sharp area of contact with the cam. This is the simplest among all of the followers and these kinds of followers are not in use in the case of fast application, because of its sharp edge.
2) Roller Follower
This type of follower mainly uses in high-speed operation because it has a smooth contact with the surface. This type of follower has less wear and tear as compared to the other followers.
3) Flat-faced Follower
This type of follower looks like a flat surface with an irregular cam. This type of cam is used when the space is limited and this follower can resist more side thrust. This follower can also be used in a precision application.
4) Spherical Follower
This type of follower has a curved but regular follower as well as cam. This is a modification of a flat-faced follower.
Types of follower according to Movement
In this category followers are classified by the relative motion and movement between cam and follower these are as follow.
1) Translatory motion type follower
In this type of follower, followers have translatory motion means the cam is rotating and the follower reciprocating between the guideway. Example of this type follower is knife-edge follower, roller follower, flat follower, and spherical follower.
2) Oscillatory motion type follower
In this type of follower, the follower has an oscillating motion. Cam rotates and as per cam profile follower also moves but the follower is fixed at the point about which the follower is oscillating. This type of follower is called an oscillatory motion type follower.
Types of follower according to the line of movement
1) Radial Follower:
In this type of follower, the line of movement passes through the center of the camshaft. Mainly the movement of the follower is in line. The follower is in a reciprocating motion.
Note: – Diagram is same as knife-edge follower
2) Offset Follower:
In this type of follower, the movement of the axis of the follower is not colinear with the cam axis.
Application of Cam and Follower
A CAM is a rotating machine element that gives reciprocating or oscillating motion to another element known as a follower.
There are so many applications of Cam and Followers as mentioned below:
- Cam and follower are widely used for operating inlet and exhaust valve of I C engine.
- These are used in wall clocks.
- These are used in the feed mechanism of the automatic lathe Machine.
- Screw pieces of machinery.
- Gear-Cutting Machineries.
- In Printing Machinery, this mechanism helps the screen to print. The push helps to take the position where the printing will do and the pull helps to print on that.
- In Hydraulic Systems, This is the main mechanism.
- Also in Textile Types of machinery, the mechanism of Cam and Follower helps to stitch clothes by a push and pull to move.
- In that case, the mechanism is dependent on the fluid pressure.
- Automated Types of machinery, Cam, and Follower use in different parts that are automated in motion.
A cam and follower mechanism is a profiled shape mounted on a shaft that causes a lever or follower to move. Cams are used to convert rotary to linear (reciprocating) motion. As the cam rotates, the follower rises and falls in a process known as reciprocating motion.
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel (e.g. an eccentric wheel) or shaft (e.g. a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path.
A cam and follower mechanism is a profiled shape mounted on a shaft that causes a lever or follower to move. Cams are used to convert rotary to linear (reciprocating) motion. The follower maintains contact with the cam through the force of gravity or by a spring.
A cam is a rotating element that gives oscillating or reciprocating motion to the follower, another element of this machine by direct contact.
A follower is a rotating or oscillating element of a machine that follows the motion of a cam by direct contact.
Cam and follower are widely used for operating inlet and exhaust valve of I C engine. These are used in wall clocks. These are used in the feed mechanism of the automatic lathe Machine. These are used in paper-cutting machines.