Have you ever wondered how the needle in a sewing machine moves? The needle’s periodic to and fro or up and down motion is known as reciprocating motion. This unique mechanism is also used in controlling the opening and closing of valves in Internal Combustion (IC) engines.
What Is a Cam and Follower Mechanism?
The cam and follower mechanism is a mechanical device used to achieve reciprocating motion. It consists of two main components: the cam, which is the rotating member, and the follower, which is the reciprocating member. The cam, which can be a profiled disc, cylinder, or sphere, influences the motion of the follower. The follower, often in contact with the cam through a spring or its weight, is a rod.
The cam and follower mechanism includes three members:
- Cam – Driving member
- Follower – Driven member
- Frame – Supporting member
As the cam rotates, its varying cross-section causes the follower to reciprocate. The frame or guide aids the reciprocating motion of the follower and provides support for the cam and follower.
Types of Cam and Followers
Cams and followers can be classified into various types. Let’s explore them.
Types of Cam Based on the Shape
- Radial Cam: This type of cam is a flat plate or disc carved to obtain the desired motion of the follower. In radial cams, the motion of the follower is perpendicular to the axis of rotation of the cam.
- Cylindrical Cam: These cams are cylindrical in shape, with a groove cut on the surface. The follower moves along the path of the groove, and its motion is parallel to the axis of rotation of the cam.
- Wedge Cam: Wedge cams have a wedge shape and exhibit sliding motion. The follower moves up and down as the cam moves to and fro. In this type, the motion of the cam and follower is perpendicular to each other.
- Conjugate Cam: Conjugate cams have two rollers connected to the follower. Both rollers restrict each other’s motion, making this type of cam suitable for noiseless operation.
- Globoidal Cam: Globoidal cams are similar to cylindrical cams, as they both have a groove cut. However, the surface of a globoidal cam is either concave or convex.
- Spherical Cam: Spherical cams have a groove cut into them, and their shape resembles that of a sphere.
Types of Followers
Like cams, followers can also be classified based on their shape, position, and motion.
Based on the Shape
- Knife Edge Follower: This follower has a pointed tip in contact with the cam. However, the pointed tip can cause wear and tear on the cam.
- Roller Follower: Roller followers are used to overcome the drawbacks of knife-edge followers. A roller attached to the tip of the follower makes contact with the cam, reducing friction and wear.
- Flat-Faced Follower: Flat-faced followers have a flat surface that makes contact with the cam. They are used when quick motion is required. However, they can develop high surface tension during misalignment and deflection.
- Spherical Faced Follower: Spherical followers are designed to overcome the difficulties faced by flat-faced followers. The contact area is spherical, resulting in reduced wear and tension.
Based on the Position
- Inline Follower: In an inline follower, the axis of the follower coincides with the center of the cam.
- Offset Follower: In an offset follower, the follower’s axis is slightly away from or at an offset to the center of the cam.
Based on the Motion
- Translating Follower: If the cam’s motion is in a straight line, it is called a translating follower.
- Oscillating Follower: An oscillating follower is pivoted, resulting in an oscillating motion.
Pros and Cons of the Cam and Follower Mechanism
The cam and follower mechanism offers several advantages:
- It is a simple mechanism that efficiently converts rotary motion to reciprocating motion.
- With proper design, any desired motion of the follower can be achieved.
- This mechanism can bear high vibrations.
- It is accurate and versatile.
However, there are also some disadvantages:
- The cam is prone to wear and tear.
- The manufacturing cost is high, requiring precision.
- The cam and follower setup consumes more space.
Applications of Cam and Follower Mechanism
The cam and follower mechanism finds various applications, including:
- In IC Engines: The reciprocating motion of the inlet and exhaust valves in IC engines is achieved using the cam and follower mechanism.
- In Children’s Toys: Many toys utilize the cam and follower mechanism to achieve simple periodic motion.
- In Automatic Lathe Machines: The motion of tools in automatic lathe machines is controlled by the cam and follower mechanism. Additionally, the feed mechanism in lathe machines is achieved through this mechanism.
Ongoing research aims to enhance the performance of the cam and follower mechanism. For instance, a student at Skill-Lync designed a simple cam and follower model using 3D contact in Hyper Works in 2019. By implementing a phenomenon called lift-off, the student achieved a curve-to-curve joint and reduced damping.
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