Have you seen the sewing machine needle move? The motion is called reciprocating as it goes to and fro or up and down.
This is a special mechanism seen in controlling the opening and shutting of the valves in IC engines.
What Is a Cam Follower?
A cam follower, or track or roller follower, is an assembly component that rotates or oscillates, directly contacting the translating cam to translate the cam’s reciprocating motions to vertical movement relating to the cam’s axis into linear motion.
The primary role of this component is to follow the shape of the cam lobe profile, whether regular or irregular, which may oscillate or translate. This motion will then be converted into linear oscillating or reciprocating motion.
Depending on application and type, followers can only contact the profile of the cam surface or provide force through spring loading; they can also exhibit a constant velocity or a constant acceleration speed acting to provide complex output motions by following the shape of the cam surface.
Types of Cam Followers
Cam followers are categorized by various aspects, and variety and specificity are central to them.
Based on the Shape
- Knife-Edge Follower: A pointed follower that contacts the cam. The tip is sharp, which can cause wear due to having a point.
- Roller Follower: Has a roller at the opposite end in order to reduce friction or wear on the cam, which is an improvement over a knife-edge follower.
- Flat-Faced Follower: Has a flat face and is general suitable for fast motion, but can create large stresses if misaligned.
- Spherical Faced Follower: Has a rounded face to reduce wear and disperse pressure on the edge.
Based on the Motion
- Oscillating Follower: When the cam rotates, the follower changes the cam’s rotational motion into a linear and oscillating motion creating a vibratory motion.
- Reciprocating Follower: When the cam rotates, it changes the cam’s motion into a back-and-forth linear motion.
Based on the Line of Movement
- Radial Follower: The path of motion of this follower aligns with the center of the cam converting a rotary motion of the cam into a linear reciprocating motion.
- Offset Follower: The path of motion of this follower does not extend through the center of the cam leading to a dissimilar linear motion.
Cam Follower Bearings
Cam followers are heavily dependent on bearings to achieve optimal performance. They are equipped to manage high radial loads through roller bearings and needle bearings.
The bearing aspect of the rotary core is an essential aspect of exact power transfer and further developments in advanced automation processes.
These “followers” of cam bearings – track followers – have physical characteristics engineered to be rugged, withstanding intermittent shocks and very heavy loads.
They can also be designed to include a flexible core to add additional protection against the effects of violent shock loads.
These followers are constructed in two basic designs:
- Stud type rollers: designed as an integral stud and mounted is easy – for direct mounting – which withstands high radial load.
- Yoke type rollers: Steered onto a shaft or pin and to have applications where alignment is sometimes varied or traversing is needed.
What is a Cam?
The cam is a rotating element that produces reciprocating or oscillating motion to the follower through direct contact. It is primarily designed to change the movement from the rotary to linear.
It is an element that belongs to machinery, is an electric wheel or shaft that revolves around and contacts the lever at several locations on the circular path. It is often used in a steam hammer as a simple tooth to change pulses of power into a steam hammer.
Types of Cams
Here are some types of cams, which are explained below:
- According to the Cam Shape:
- Wedge or flat cam
- Disk or Plate cam
- Spiral cam
- Cylindrical cam
- Heart-shaped cam
- Translating cam
- Snail drop cam
- Conjugate cam
- Globoidal cam
- Spherical cam
- According to the follower movement of the cam
- Rise return rise
- Dwell rise dwell return dwell
- Dwell rise return dwell
- According to the manner of the constraint of the follower
- Preloaded spring cam
- Gravity cam
- Positive drive cam
#1. Wedge or Flat Cam.
Wedge or flat cam has a straight shape, which is functioned for providing some specific straight movement following the followers application.
#2. Disc or Plate Cam.
The disc or plate cam does not have a straight shape, but provides some specific movement to the follower dispensing on it.
#3. Spiral Cam.
The spiral cam is having a semi-circular groove contours or spiral shape. The cam travels in a reciprocating motion, while the follower moves at a perpendicular direction to the axis of the cam.
#4. Cylindrical Cam.
Cylindrical cam consists of a groove on the cylindrical surface and the follower in turns moves parallel to the axis on a cylindrical surface.
#5. Heart-shaped Cam.
Heart-shaped cam shape like an asymmetric heart. It’s essentially used for turning a shaft to hold cam in position by its roller pressure.
#6. Translating Cam.
A translating cam contains a groove or contour plate, and the follower oscillates in front of the plate. The groove or contour plate decides the movement of the follower.
#7. Snail Drop Cam.
The snail drop cam is found in a mechanical timekeeping clock so the daytime advance system can run on midnight exactly, and involve a follower over 24 hours with the cam, in a spiral path.
The snail drops cam ends with a sharp cut-off as the follower will drop down, and activate the day in advance.
#8. Conjugate Cam.
The conjugated cam has a two separate oscillating roller mechanism. The followers as a conjugation measuring fixture. The change of the suboptimal angle between the two follower arms when the cam revolves, may denote the change of the cam profile errors.
#9. Glenoidal Cam.
Globoidal cam is the one of the most complex cams, in shape terminology. With the globoidal cam, the working surfaces are the contacting surfaces, and the roller surfaces.
#10. Spherical Cam.
In comparison to bevel gears, spherical cam mechanisms are an alternative as they provide less back-lash, and less friction losses.
What is a Follower?
A follower is an oscillating or rotating part of a machine that directly connects with the cam and follows the cam’s motion. In reciprocating motion, the follower moves in a parallel motion with the cam axis.
A follower is part of a machine that follows the cam and can oscillate or reciprocate in motion. Thus, the follower converts the cam’s rotary motion into reciprocating or oscillating movement.
Types of Followers
Following are the types of followers, which are described below,
- According to the shape of the follower
- Roller follower
- Knife edge follower
- Flat-faced follower
- Spherical follower
- According to the movement of the follower
- Reciprocating follower
- Oscillating follower
- According to the line of movement of the follower
- Radial follower
- Offset Follower
#1. Roller Follower.
The roller follower is especially used when operating at high speeds due to its smooth contact with the surface and less wear than other followers.
#2. Knife Edge Follower.
These types of followers have a sharp point of contact with the cam. The knife edge follower is the simplest of all followers. Radial followers are not used in high-speed applications, due to the sharp edge.
#3. Flat-faced Follower.
The flat-faced follower is a flat surface that resembles the irregular cam. In this case, the cam is applied when space is limited, as this follower can handle more thrust than other followers. The flat-faced follower can be applied for a specific application.
#4. Spherical Follower.
The spherical follower is a combination of a round or flat follower and a cam. This follower is modified from the flat-faced follower.
#5. Reciprocating Follower.
In the reciprocating follower, as the cam rotates, the follower reciprocates or will change into the guide.
#6. Oscillating Follower.
The oscillating follower is placed at a point on the frame with proper tension and will oscillate. The follower moves in rotary motion due to the cam.
#7. Radial Follower.
A radial follower is used when the line of follower movement passes through the center of rotation of the camshaft. The line of follower movement is in a reciprocal motion.
#8. Offset Follower.
An offset follower is used when the follower motion line is offset from the center of the camshaft rotation.
How Do Cams and Followers Work?
Working of Cam
The cam is a mechanical element that turns a wheel or revolves on its short axis that always maintains contact with the follower. Or in language of the layman, a cam is a mechanical element that will reciprocate and or oscillate or linear motion or any combination thereof to the follower.
The geometry of the cam is commonly an oblong or incomplete circle or eclipse. If the engineer considers an oblong cam, they would observe movements which would cause an external load and the load is periodic for its position.
This external burial is most useful and effective given the task being periodic mechanical. There are two styles of cam head; single and multiple head.
Working of Follower
A follower is the mechanical element on which the cam rotates in the oscillating or circular motion and it also stops the push and pulls of the cam. The followers are used to transfer the movement to a specific machine part.
The mechanism for the cams and followers varies based on one another. The follower also revolves on an oscillating or circular arc.
The cams and followers mechanism is essential to the engineering field. There are very different functions for each machine that have their own functions.
Terminology Associated With Cams and Followers
Here are the terms used in the terminology of cam:
- Cam profile
- Base circle
- Pitch curve
- Trace point
- Pressure angle
- Pitch point
- Pitch circle
- Prime circle
#1. Cam Profile.
The surface area of a cam where the follower engages is referred to as the cam profile.
#2. Base Circle.
The base circle is the min. circle of the cam profile from the canter rotation of the cam.
#3. Pitch Curve.
A Pitch curve is formed when we suppose the cam is very fine, and the trace point of the follower is rotating around the cam.
#4. Trace Point.
A trace point is helpful in the detection of the cam profile.
#5. Pressure Angle.
A pressure angle is formed between the normal to pitch curve and the motion line of the follower.
#6. Pitch Point.
A point where we maximize pressure is called a pitch point.
#7. Pitch Circle.
A pitch circle that goes through the pitch point.
#8. Prime Circle.
A prime circle is a circle drawn from the tangent to the pitch curve and concentric to the base circle.
Why Need Cams and Followers?
In mechanical engineering, the cam and follower mechanism plays an essential role in providing an even distribution of forces throughout an element of a machine.
An engineer can create automatic motion by mounting a cylindrical roller to the machine element.
Cams and followers can be used in machine elements with the size and shape of nuts. Also, various forms of linear motion can be found using the cam and follower mechanism.
In addition, the cam and follower mechanism can absorb a greater degree of shock due to added thickness compared to other bearings, which can increase the mechanical efficiency of the element of the machine.
Furthermore, this mechanism is generalized for applications in a soda machine or airplane (aviation) applications. It is also used in conveyor belt systems as well.
However, flat followers are commonly used to operate the valves of an engine, while roller followers are used in oil and stationary engines.
Where are Cams and Followers Used?
Applications of Cam and Follower:
- Cam and follower work in internal combustion engines to open and close the intake and exhaust valves.
- As a hydraulic system since the operation requires fluid pressure.
- Cam and follower are implemented in printing machines to move the screen into position.
- The cam and follower can also work in a textile machine to sew and pull fabric.
- Used in screw machinery and gear cutting machinery.
- Cam and follower can also work in wall clocks and automatic lath machines.