Daily Question (20100119): Application characteristics of cam mechanisms

(1) Composition of the cam mechanism A cam is a component with a curved profile or grooves. Camshafts usually rotate at a constant speed, but they can also oscillate or move back and forth. The push rod is a component that is directly driven by the cam. Since the push rod in a cam mechanism is usually a follower, it is often referred to as a follower as well. A cam mechanism is a higher pair mechanism composed of three main components: a cam, a push rod, and a frame. 　　(2) Characteristics of cam mechanisms 　　1) Advantages: By appropriately designing the contour curve of the cam, it is possible to achieve various desired motion patterns for the push rod, and the mechanism remains simple and compact. 　　2) Disadvantages: The cam profile is in point or line contact with the push rod, which leads to easy wear; therefore, cam mechanisms are often used in applications where not much force needs to be transmitted.

Advantages: The cam mechanism consists of fewer components, resulting in a relatively simple structure. By properly designing the contour curve of the cam, it is possible to enable the follower to follow various desired motion patterns, and the design process is relatively easy. Disadvantage: A high pair of point or line contact is formed between the cam and the follower, and significant friction and wear occur at the contact point as a result of the interacting forces and relative motion. It is widely used in various machines, especially in automated machinery and the mechanical control devices in assembly lines

(1) The motion law of the driven member can be specified arbitrarily； (2) The cam mechanism enables variable-speed starting, with accurate and reliable operation ； (3) The machining of cam profiles as curved shapes has become much more convenient thanks to the widespread use of CNC machines and computers ； (4) At the high-contact point of the cam, it is difficult to maintain good lubrication, resulting in easy wear. To ensure a sufficient service life, the power transmitted should not be too large.

Advantages: Cam mechanisms consist of a small number of components, resulting in a relatively simple structure. By properly designing the contour curve of the cam, it is possible to enable the follower to follow various desired motion patterns, and the design process is relatively easy. Disadvantage: A high pair of point or line contact is formed between the cam and the follower, and significant friction and wear occur at the contact point as a result of the interacting forces and relative motion. Cam mechanism with knife-edge follower – sliding friction occurs at the point of contact, resulting in severe wear; therefore it is rarely used in practice. Cam mechanism with roller follower – rolling friction occurs at the point of contact, which significantly reduces frictional wear; therefore, it is widely used in practical applications. Cam mechanism with flat face follower – Although sliding friction still exists at the point of contact, an oil film is easily formed there, serving as a lubricant. Moreover, the force acting at that point (excluding friction) is always perpendicular to the flat surface, which ensures smooth transmission; for this reason, it is also widely used.

The basic components of a cam mechanism: cam, push rod (follower), and frame. ◆ Applications of cam mechanisms: Cam mechanisms are widely used in automatic machinery, automatic control devices, and assembly lines. ◆Advantages of cam mechanisms: they have a simple and compact structure. By appropriately designing the cam profile, it is possible to make the push rod perform various desired motion patterns, as well as achieve intermittent motion. ◆Advantages of cam mechanisms: The contact is of a high-order type, which makes them prone to wear; they are often used in applications where not much force needs to be transmitted.

　The basic feature of cam mechanisms in applications is that they enable the driven element to follow relatively complex motion patterns, while maintaining a simple and compact structure. Since the motion pattern of the follower depends on the cam profile curve, in practice it is sufficient to design the cam profile curve based on the motion pattern of the follower.

The basic feature of cam mechanisms in applications is that they enable the driven element to achieve more complex motion patterns. Since the motion pattern of the follower depends on the cam profile curve, in practice, by designing the cam profile curve according to the follower’s motion pattern, it is possible to achieve various desired motion patterns for the push rod, while keeping the mechanism simple and compact. However, its drawback is that there is point or line contact between the cam profile and the push rod, which leads to easy wear; therefore, cam mechanisms are mostly used in applications where not much force needs to be transmitted.

) Characteristics of cam mechanisms 　　1) Advantages: By appropriately designing the contour curve of the cam, it is possible to achieve various desired motion patterns for the push rod, and the mechanism remains simple and compact. 　　2) Disadvantages: The convex profile line is in point or line contact with the push rod, which leads to easy wear; therefore, cam mechanisms are often used in applications where not much force needs to be transmitted

Advantages: The cam mechanism consists of fewer components, resulting in a relatively simple structure. By properly designing the contour curve of the cam, it is possible to enable the follower to follow various desired motion patterns, and the design process is relatively easy. Disadvantage: A high pair of point or line contact is formed between the cam and the follower, and significant friction and wear occur at the contact point as a result of the interacting forces and relative motion. Cam mechanism with knife-edge follower – sliding friction occurs at the point of contact, resulting in severe wear; therefore it is rarely used in practice. Cam mechanism with roller follower – rolling friction occurs at the point of contact, which significantly reduces frictional wear; therefore, it is widely used in practical applications. Cam mechanism with flat face follower – Although sliding friction still exists at the point of contact, an oil film is easily formed there, serving as a lubricant. Moreover, the force acting at that point (excluding friction) is always perpendicular to the flat surface, which ensures smooth transmission; for this reason, it is also widely used.

Advantages: The cam mechanism consists of fewer components, resulting in a relatively simple structure. By properly designing the contour curve of the cam, it is possible to enable the follower to follow various desired motion patterns, and the design process is relatively easy. Disadvantage: A high-degree of contact is formed between the cam and the follower, which is of point or line contact; as a result of the interacting forces and relative motion at this contact point, significant friction and wear occur