A cam and follower is a mechanical pair in which a rotating (or sliding) shaped member called the cam imparts a precise, repeating motion to a contacting member called the follower. As the cam turns, its specially designed profile pushes the follower through a defined sequence of rise, dwell and return, converting rotary motion into reciprocating or oscillating motion. It is one of the most important higher pairs studied in the Theory of Machines.
Cam-and-follower mechanisms appear everywhere precise timed motion is needed: the valve gear of internal combustion engines, automatic lathes, printing machinery, textile looms and packaging equipment. Because the output motion is determined entirely by the cam profile, engineers can program almost any motion law into a single rotating part. This makes the cam and follower a core teaching topic for engineering, polytechnic and diploma students across India and abroad.
What is the basic working principle of a cam and follower?
The cam is usually mounted on a rotating shaft and rotates at a steady speed. The follower rests against the cam surface, held in contact by a spring, gravity or a positive groove. As the cam rotates, the changing radius of its profile lifts and lowers the follower. The motion the follower performs in one full rotation of the cam is the follower displacement diagram, which typically contains four phases:
- Rise — the follower moves outward away from the cam centre.
- Outer dwell — the follower stays stationary at maximum lift.
- Return — the follower moves back toward the cam centre.
- Inner dwell — the follower stays stationary at minimum lift.
The follower is a follower because it copies whatever motion the cam profile dictates. By cutting a different profile, the same hardware can deliver uniform velocity, simple harmonic, uniform acceleration–retardation or cycloidal motion. This programmability is what makes the mechanism so versatile.
What are the main types of cams?
Cams are classified mainly by their shape and the plane in which motion occurs. The most common types studied in a Theory of Machines lab are summarised below.
| Type of cam | Description | Typical application |
|---|---|---|
| Radial (disc/plate) cam | Follower moves perpendicular to the cam axis; profile is cut on the edge of a disc. | Engine valve gear, automatic machines |
| Cylindrical (drum) cam | A groove is cut around a rotating cylinder; the follower moves parallel to the axis. | Textile and machine tool feeds |
| Wedge / translating cam | A flat wedge slides linearly instead of rotating. | Simple indexing devices |
| Face / end cam | Profile cut on the end face of a cylinder. | Indexing and feed mechanisms |
| Conjugate cam | Two cams act together for positive drive in both directions. | High-speed precision machinery |
What are the types of followers?
Followers are classified by the shape of the contacting surface and by the direction of their motion. Both classifications are commonly demonstrated on a cam analysis apparatus.
Classification by contact surface
- Knife-edge follower — a sharp edge contacts the cam. Simple but wears quickly; mainly of theoretical interest.
- Roller follower — a roller reduces friction and wear; very widely used in practice.
- Flat-faced (mushroom) follower — a flat surface contacts the cam, used in automotive valve trains where side thrust must be low.
- Spherical-faced follower — a curved face reduces surface stress and tolerates misalignment.
Classification by line of motion
- Radial (in-line) follower — the follower axis passes through the cam centre.
- Offset follower — the follower axis is offset from the cam centre to reduce side thrust.
- Reciprocating follower — moves in a straight line.
- Oscillating (pivoted) follower — swings about a fixed pivot.
What are the types of follower motion?
The motion law programmed into the cam profile determines how smoothly the follower accelerates. The four standard motions taught are:
- Uniform velocity — constant follower speed, but theoretically infinite acceleration at start and end, so it causes shock. Suitable only for low speeds.
- Simple harmonic motion (SHM) — smooth velocity, finite acceleration; good for moderate speeds.
- Uniform acceleration and retardation (parabolic) — gives the lowest peak acceleration for a given lift and time, used for higher speeds.
- Cycloidal motion — zero acceleration at start and end, producing the smoothest, lowest-vibration motion; preferred for high-speed cams.
What is the displacement formula for a cam follower?
For a follower moving with simple harmonic motion, the displacement y at any cam angle is given by:
y = (h / 2) × [1 − cos(π × θ / β)]
where:
- y = follower displacement, in millimetres (mm)
- h = total lift or stroke of the follower (mm)
- θ = cam rotation angle measured from start of rise (degrees or radians)
- β = total cam angle for the rise or return phase (degrees or radians)
For uniform velocity motion the relationship is simply linear: y = h × (θ / β). The corresponding follower velocity is the rate of change of displacement with time, and the velocity and acceleration diagrams are obtained by differentiating the displacement diagram. Studying how peak acceleration changes between these motion laws is exactly what a teaching cam apparatus is designed to reveal.
How is a cam and follower demonstrated in a teaching lab?
A cam analysis apparatus (also called a cam and follower test rig) lets students measure follower displacement against cam angle and plot the actual motion curve. A typical experiment proceeds as follows:
- Mount the chosen cam (for example, a tangent or circular-arc cam) on the driven shaft.
- Fit the required follower — knife-edge, roller or flat-faced.
- Rotate the cam shaft in fixed angular steps using a graduated dial or protractor scale.
- At each angle, read the follower lift from a dial gauge or vertical scale.
- Tabulate cam angle (θ) versus follower displacement (y).
- Plot the displacement diagram and compare it with the theoretical curve from the formula above.
- At higher speeds, observe jump — the point where the follower loses contact with the cam because inertia exceeds the spring force.
Typical measurements and units
| Quantity | Symbol | Unit | Measured by |
|---|---|---|---|
| Cam angle | θ | degrees | Protractor / graduated dial |
| Follower lift | y | mm | Dial gauge or vertical scale |
| Total stroke | h | mm | Maximum minus minimum lift |
| Cam speed | N | rev/min | Tachometer (motorised rigs) |
The experiment teaches students how a cam profile translates directly into a motion law, why follower jump must be avoided in high-speed machines, and how spring stiffness keeps the follower in contact. It bridges the gap between the textbook displacement diagram and real machine behaviour.
Where to source cam and follower lab equipment
For colleges and training institutes, cam analysis apparatus is part of the wider Theory of Machines Lab Equipment range used to teach mechanisms, gears, governors and balancing. Scientico, based in Ambala, Haryana, is an ISO 9001:2015 and CE certified manufacturer of mechanical engineering teaching apparatus, including cam and follower setups, and has supplied laboratory equipment to institutions in 60+ countries since 1993. Scientico is GeM-registered, and quote-based proforma invoices (CIF) are typically issued within 24 hours; technical specifications, calibration and conformity documentation are provided with each instrument. Questions on configuration can be sent via WhatsApp at +91-7015865225.
Key takeaways
- A cam and follower converts rotary motion into a precisely timed reciprocating or oscillating motion defined by the cam profile.
- Cams are classified as radial, cylindrical, wedge, face and conjugate; followers by contact surface (knife-edge, roller, flat-faced, spherical) and by motion (radial, offset, reciprocating, oscillating).
- Common follower motions are uniform velocity, simple harmonic, uniform acceleration, and cycloidal — listed in order of increasing smoothness.
- The SHM displacement law is y = (h/2)[1 − cos(πθ/β)], measured in a lab by plotting follower lift against cam angle.
Frequently Asked Questions
What is a cam and follower in simple words?
A cam is a shaped rotating part, and a follower is the part that rests against it and moves as the cam turns. Together they convert rotary motion into a precise up-and-down or swinging motion set by the cam’s profile.
What is the difference between a cam and a follower?
The cam is the driving member with a specially shaped profile mounted on the rotating shaft. The follower is the driven member that contacts the cam and copies the motion dictated by that profile.
What are the four types of follower motion?
Uniform velocity, simple harmonic motion (SHM), uniform acceleration and retardation (parabolic), and cycloidal motion. Cycloidal gives the smoothest, lowest-vibration motion and is preferred for high-speed cams.
What is the displacement formula for simple harmonic follower motion?
y = (h/2) x [1 – cos(pi x theta / beta)], where y is follower displacement (mm), h is the total lift (mm), theta is the cam angle, and beta is the cam angle for the rise or return phase.
How is a cam and follower tested in a laboratory?
A cam analysis apparatus is used. The cam is rotated in fixed angular steps while the follower lift is read on a dial gauge at each angle. Plotting lift against cam angle produces the displacement diagram, which is compared with the theoretical motion curve.
Does Scientico manufacture cam and follower lab equipment?
Yes. Scientico is an ISO 9001:2015 and CE certified manufacturer in Ambala, India, producing Theory of Machines apparatus including cam and follower setups, exporting to 60+ countries since 1993. It is GeM-registered and issues CIF proforma invoices within 24 hours.
Lab Equipment Featured in This Guide
Manufactured in-house by Scientico India — ISO 9001:2015 & CE certified, exported to 60+ countries. Request a CIF quote within 24 hours.
