Cam (mechanism)
A cam is a rotating component of a mechanical system that influences the motion of another part known as the follower. The cam rotates around a shaft, resulting in the follower experiencing movements termed rise, fall, and dwell. The shape of the cam—such as pear, circular, elliptical, square, or triangular—determines the specific way the follower moves during each rotation. For instance, a pear-shaped cam allows the follower to rise and fall only for a portion of the rotation, while a circular cam with an off-center shaft causes continuous movement without dwell periods, known as an eccentric cam. Cams are integral to various machines, including household appliances, industrial equipment, and automobile engines, making them essential for performing specific tasks through controlled motion. Understanding the interaction between the cam and follower provides insight into how machinery operates effectively.
On this Page
Subject Terms
Cam (mechanism)
A cam is a rotating piece of a mechanism in a machine that imparts motion to another piece of the mechanism. This other part is known as the follower. The cam rotates by way of a shaft, and this causes the follower to undergo several events that include movements and periods of rest. The shape of the cam—and sometimes the position of the cam's shaft—determines the way in which the follower moves. Cams are an important part of many machines and are found in everything from household appliances to automobile engines.
Overview
Many machines include two main parts: the cam and the follower. These parts are in contact with each other, with the follower sitting atop the cam. The cam rotates, which causes the follower to move. A shaft rotates the cam.
During the rotation of the cam, the follower undergoes a series of events: the rise, fall, and dwell. The rise is movement away from the center of the cam. The fall, also called the return, is movement toward the center of the cam. The dwell is a period of rest. Because the follower sits atop the cam, this means that it moves up during the rise and down during the fall. The follower's movement repeats with every rotation of the cam.
The way in which the follower moves is dependent on the shape of the cam. Common shapes include pear shaped, circular, elliptical, square, and triangular. With a pear-shaped cam, about three-quarters of its surface area is circular, and about one-quarter is elliptical. When the cam rotates, only the elliptical part of it causes the follower to move. This means that during one rotation of the cam, the follower is in the rise and fall states for approximately one-quarter of the time and the dwell state for about three-quarters of the time. Furthermore, with each rotation of the cam, the follower rises once, falls once, and dwells for the remainder of the time. A cam with a different shape causes the follower to move in a different way during each rotation of the cam, both in the amount of time it spends in the rise, fall, and dwell states and in the number of times it rises and falls.
The position of the cam's shaft also may affect the way in which the follower moves. A circular cam with a shaft positioned in the center does not cause the follower to rise or fall at all during a rotation. However, if a circular cam has a shaft that is off-center, this causes the follower to continuously rise and fall without any dwell period during each rotation. Such a cam is sometimes referred to as an eccentric cam.
Cams play an important role in the world of mechanics as they help parts of machines move. They are found in many household appliances, industrial tools, and automobile engines.
Bibliography
"Cams." CodeCogs, www.codecogs.com/library/engineering/theory‗of‗machines/cams.php. Accessed 13 Jan. 2025.
Nice, Karim. "How Camshafts Work." HowStuffWorks, 21 Feb. 2024, auto.howstuffworks.com/camshaft.htm. Accessed 13 Jan. 2025.
Woodford, Chris. "Cranks and Cams." Explain That Stuff, 22 Sept. 2022, www.explainthatstuff.com/cranks-and-cams.html. Accessed 13 Jan. 2025.
Zhang, Yi, et al. "Introduction to Mechanisms." Carnegie Mellon University, www.cs.cmu.edu/~rapidproto/mechanisms/chpt6.html. Accessed 13 Jan. 2025.