When it comes to transforming rotary and vibration motion into linear, there's rarely a better and more appropriate mechanism than a cam and cam follower assembly. Cam and cam follower mechanisms are often used in mechanical engineering and various machinery, like internal combustion engines, automatic lathe machines, diesel fuel pumps, and other repeating machinery and manufacturing applications.

Cams are specifically designed rotating components that are used to transform rotary motion into linear motion. They're driving the cam follower (driven member) that internally connects to the cam. The cam profile is designed to achieve the desired motion, and its varying cross-section makes the cam follower reciprocate.

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In this article, we'll discuss cam followers, what exactly they are, what are the different types, and how they're classified using different classification criteria.

What Is a Cam Follower?

A cam follower, also known as a track follower or a roller follower, is a rotating or oscillating component of an assembly that follows the motion of the translating cam through direct contact; it transforms the cam's reciprocating motions into a linear motion by moving vertically in relation to the cam's axis.

The major function of this component is to follow the regular or irregular shape of the cam's lobe profile, which may be oscillating or reciprocating, and thus alter its rotation motion into oscillating or reciprocating linear movement.

Depending on the type and application, followers may merely touch the surface profile of the cam or exert pressure through spring loading. They may also have uniform velocity or uniform acceleration speed and help obtain complex output motions by trailing the shape of the cam.

Types of Cam Followers

Cam followers come in a vast array of different configurations and are mostly categorized into three basic categories with their specific sub-categorizations. Here's the breakdown of follower types by category:

1. According to the follower's shape:
   1. Roller follower
   2. Spherical follower
   3. Knife-edge follower
   4. Flat-faced follower
2. According to the follower's movement:
   1. Oscillating follower
   2. Reciprocating follower
3. According to the follower's line of movement:
   1. Radial follower
   2. Offset follower

Follower Shape Types

Here's a breakdown of cam followers according to the shape of the follower:

• Roller Follower — A roller follower is a follower that is hinged to a roller and in touch with a roller cam, and as the cam spins, the follower oscillates. Roller followers are mostly used in heavy-duty applications where a lot of power needs to be conveyed, like in stationary IC engines, as they provide smooth contact with the surface and have less wear and tear compared to other types of followers.
• Spherical Follower — This type of follower is an improvement of the flat-faced follower (mentioned below), which has a wide spherical contact point with the cam.
• Knife-Edge Follower — A knife-edge follower is a very distinct type of follower since its sharp shape facilitates a very narrow contact with the cam. Knife-edge followers are seldomly, if ever, used due to their shape and very high wear rate induced by incredibly high contact stress.
• Flat Face Follower — Flat followers have a wide, flat contact area, and it's mostly employed in applications with inadequate space, as they can withstand more side thrust. They're mostly used in precise applications.

Follower Movement Types

Here's a breakdown of cam followers according to the movement of the follower:

• Oscillating Follower — This type follows the oscillating rotating movement of the cam into a linear oscillating motion, producing a vibrating motion.
• Reciprocating Follower — This follower reciprocates as the cam rotates; the aforementioned types of followers (classified by shape) are good examples of reciprocating followers.

Followers by Type of Line Movement

Here's a breakdown of cam followers according to the follower's line of movement:

• Radial Follower — With this type of follower, its line of motion passes through the center of the frame, and the follower itself moves in a line, transforming the rotary motion of the cam into a reciprocating motion.
• Offset Follower — With this type, the follower line of motion doesn't lie in the same line as the center of the cam.

Cam Follower Bearings

Some cam followers, typically roller followers, have a broader application spectrum, and besides following rotating cams, they can also be used for power transmission, work holding and automation, and indexing. This is facilitated by their use of a rotary bearing core that serves as an interface between the independently moving sections of the assembly.

Roller cam follower designs usually employ roller bearings and needle bearings to carry a high radial load at high speeds. However, this design is widespread and used in almost all applications involving roller cam followers.

What Is a Cam?

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A cam is a rotating part of the cam and follower assembly that directly contacts the followers to transmit rotary or reciprocating movement. Its primary function is to act as an input of rotary motion that transforms into linear motion.

The cam is one of the crucial elements in machinery which relies on a multi-point lever system actuated by the rotating shaft or a rotating wheel, and it's one of the most frequently used components in mechanical engineering.

A common example of a cam is the camshaft of a vehicle, which takes rotary motion from the engine crankshaft and converts it into reciprocating motion to open and close the intake and exhaust valves.

However, cams and cam-operated mechanisms are everywhere, and besides cars, they're also found in washing machines, dishwashers, sewing machines (producing various seeing patterns), and lawn sprinklers.

Types of Cams

Just as there are different types of cam followers, so there are different types of cams, and you'll find the basic categorization below:

1. Based on the cam shape:
   1. Disk or plate cam
   2. Wedge cam
   3. Spiral cam
   4. Cylindrical cam
   5. Heart-shaped cam
   6. Translating cams
   7. Snail drop cam
   8. Conjugate cam
   1. Globoidal cam
   10. Spherical cam
2. Based on the follower motion:
   1. Dwell rise dwell return dwell  am
   2. Rise return rise cam
   3. Dwell rise dwell cam
3. Based on the follower constraint:
   1. Preloaded spring cam
   2. Positive drive cam

Based on the Cam Shape

Here's a breakdown of cam followers according to the cam shape:

• Disk or Plate Cam — These cams are used in conjunction with radial motion followers and are mostly compact and simple in design, with an irregular contour that transmits a specific motion to the follower.
• Wedge Cam — The wedge cam is flat and regular in shape, with a slope to transfer a specific follower movement, and we refer to a cam as being a wedge cam if it moves in a linear fashion. The four-link wedge cam mechanism consists of two permanent links and one link that resembles a cam wedge. Depending on the shape of this wedge, the follower will oscillate in the vertical direction as the cam oscillates in the horizontal direction.
• Spiral Cam — The spiral cam features a half-circular or spiral-shaped groove that guides the follower, transforming the rotating motion into a reciprocating vertical motion of the follower relative to the cam's axis.
• Cylindrical Cam — The cylindrical cam is a cam with circumferential outlines cut on the cylinder's surfaces while the cylinder rotates about its axis. They also come in two varieties. In the first type, a groove with a positive oscillating motion is carved into the surface of the cam and roller, while the other uses the cylinder itself as the working surface. The spring-loaded follower in this kind of cam translates into a cylinder moving around the parallel axis.
• Heart-Shaped Cam — This type of cam resembles an asymmetric heart, and it's mostly used to return the shaft to hold the cam in place by using the pressure exerted by the track roller interfacing with the recess in the cam surface.
• Translating Cams — These cams can rotate in the horizontal plane, and the attached follower's motion is assisted by a spring. In some cases, the groove cams are used to achieve a follower motion without needing a spring.
• Snail Drop Cam — This kind of cam is most frequently employed in mechanical chronograph watches and wall clocks so that the daytime measuring system can function. This is done by leading the follower in a swirling path through the cam for more than 24 hours.
• Conjugate Cam — This type of assembly has two cams that rotate independently of one another, with the follower acting as a conjugate measurement attachment. As the cams rotate and less-than-ideal change in an angle between two follower arms, it is interpreted as a cam profile error.
• Globoidal Cam — Globoidal cams are basically cylindrical cams with a convex or concave circumference and grooves machined into the surface that serves to guide the follower. Using a globoidal cam allows the assembly to swing the follower around a fixed point.
• Spherical Cam — Similar to the cylindrical and globolidal cams, this specific type is shaped as a sphere, with a machined groove that's in direct contact with the cam follower, which swings about a specified position while the cam spins.

Based On Follower Motion

This classification depends on the motion of the follower as dictated by the cam. Here's a breakdown of cam followers according to the follower motion:

• Dwell Rise Dwell Return Dwell Cam —The follower moves in such a way that it dwells, rises, dwells, returns, and then dwells again before rising. The entire process happens within one cam revolution.
• Rise Return Rise Cam — This is a simpler variation in which the follower rises, returns, and then rises again within one cam revolution.
• Dwell Rise Dwell Cam — Similar to other types, the follower first dwells, then rises, then dwells again, all within one cam revolution.

Based On the Constraint of the Follower

Here's a breakdown of cam followers according to the constraint of the follower:

Preloaded Spring Cam — This type of cam and follower assembly uses a spring force, with a compression spring being preloaded into the follower assembly to ensure continuous contact with the surface.

Positive Drive Cam — The positive drive doesn't require any external force generators within its assembly.

The Working Principle of Cam and Follower

The cam is a mechanical device that enables the reciprocating or vibration movement and inputs it to the follower. The follower receives the reciprocating movement from the cam and transforms it into a linear movement or transfers it to another part of the machine.

The cam is shaped like an eclipse, an imperfect circle, or an oval. An elliptical cam shows the motion that creates a periodic external load at that location. The benefits and effectiveness of this external load for routine mechanical tasks are excellent. These two devices depend on each other to function, and they're required for numerous engineering applications.

Cam and Follower Applications

One of the best-known applications for cam and follower assemblies is in internal combustion engines, where the reciprocating motion of the inlet and exhaust valves is achieved through the cam's rotational movement. However, cams and followers also found great use in children's toys that rely on simple periodic motion (like locomotive train sets).

Various industrial equipment also relies on cams and followers, including automatic lathe machines, which control not just the motion of the tool, but also the feed mechanism. Another great use is found in sewing machines, where single-head cams are used to dictate different seam patterns.

Terminology Associated With Cams and Followers

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Learning about the cam follower mechanism implies the use of common terminology that's used to describe the various sections of the assembly.

• Cam Profiles — The outer surface of the cam disc
• Base Circle — The smallest circle that's tangentially drawn with the cam profile
• Trace Point — The point on the follower which describes its motion
• Pitch Curve — The path the tracepoint generates as the follower actuates
• Pitch Point — The point of maximum pressure angle
• Prime Circle — The circle that's drawn tangentially to the base circle and pitch curve
• Pitch Circle — The circle drawn from the center of the cam that passes through the pitch point
• Pressure Angle — The angle between the normal pitch curve and the direction of the follower movement

Summary

Cam followers are perhaps the most effective way of transforming the rotation movement of the cam into the liner movement needed by another machine component. If you want to learn more about cams and cam followers, visit Reid Supply, and check out their extensive library of engineering literature and engineer resource guides.