The contacting end of the follower with the cam has a sharp knife edged hence it is called so. The groove ensures no need for a return spring. This design produces a considerable side thrust between the follower and the guide. What could be used today instead of cams? This type of cam is formed on a cylinder. Most cams are made in simple shapes designed to create basic motions — the more complex the shape of the cam, the harder the follower must work to translate it. Where feasible, a continuous oil supply can be used to extend bushing life.
Radial lines are drawn from the start position to each of the follower division lines, and the parabola is obtained by drawing a line through successive intersections. The roller follower has the advantage that the sliding motion between cam and follower is largely replaced by a rolling motion. Note that the follower runs in a track in this example. Cam mechanisms are used in various areas of machine building, such as internal-combustion engines, metal-cutting machines, and machines of the food industry, in which the cam mechanism performs a programmed operation, as well as in automated machines, in which cam mechanisms perform control functions, connecting and disconnecting working parts at the proper moment. The follower systems used on motor vehicles to control the pistons, for example, usually have a teardrop shape that causes a sharp upward motion, or displacement, as the follower reaches the apex of the teardrop, causing the attached piston to fire.
Clevis mounting provides support on both sides of the cam follower and permits use of a high strength pin. Speed limits are a major factor in selecting a bearing type. They are used in wall clocks and the of automatic lathe machines. There are multiple cam follower systems in motor vehicles, one for each cylinder, and they are offset so that all the pistons do not fire at once. This permits relubrication through the hex head. Based on Follower Motion Based on the follower motion, followers can be classified into the following two categories: i.
Loads, speeds, and life requirements. Caged Roller Followers Caged roller followers provide large internal grease storage capacity for applications where relubrication is infrequent. Cam mechanisms are compact and may be easily introduced into the general scheme of a machine. Without a stabilizing force on the follower system, the follower may have a tendency to wobble or jitter, potentially causing a malfunction in the device being moved by the cam follower and wearing the follower down more quickly. Linear motion support applications include platform support rollers and die transfer rollers.
Unsealed Design The unsealed design provides decreased friction, which assists with the prevention of skidding in lightly loaded applications and flow-through lubrication. Temperature limits for greases usually range from 225 to 250 F. Yoke type cam followers are available with and without seals, and with crowned outer rings. Link to this page: Cam Mechanism. The cam and follower have a point or line contact constituting a higher pair. A groove is cut into the cylinder, with a varying location along the axis of rotation. However, load capacity is less than that of the conventional needle bearing because there are fewer rolling elements and they are shorter.
Selecting cam or track hardness Obtaining the proper cam or track surface hardness can be as important as finding the right bearing size. The unsealed design provides the additional advantages of very low friction to prevent skidding in lightly loaded applications and flow-through lubrication. Cam specification: Plate cam, rotating anticlockwise. The roller follows the groove, and the follower moves in a plane parallel to the axis of rotation of the cylinder. A knife-edge follower consists of a follower that is formed to a point and drags on the edge of the cam. Speed is the major factor influencing operating temperature, but loading also affects the temperature.
Uses Although cam and follower systems are used in a wide variety of mechanical applications, they may be most familiar to many people for their role in cars and other motor vehicles. Camshaft angle 10 mm represents 30° Fig. Last Updated on Thu, 17 Jan 2019 1 Uniform velocity This motion is used where the follower is required to rise or fall at a constant speed, and is often referred to as. These bearing types mainly ball and tapered roller come with various roller configurations, , so they can ride on different types of tracks or perform different functions. Least radius of cam, 26 mm.
A cam follower is a type of bearing typically used to replicate a specific motion. In other applications, the head may have a roller, rather than being flat or pointed, to allow for smoother movement. As the cam rotates, the roller maintains contact with the cam and rolls on the cam surface. Least distance from follower to cam centre, 30 mm. .
Installation To ensure long bearing life, make sure your cam followers are properly mounted. Although many requisite motions in machinery are accomplished by use of pin-jointed mechanisms, such as four-bar linkages, a cam mechanism frequently is the only practical solution to the problem of converting the available input, usually rotating or reciprocating, to a desired output, which may be an exceedingly complex motion. Video Credit: Emerson Power Transmission Solutions Types Needle Roller Needle roller cam followers are used in a wide range of linear motion systems. The life of a bushing type unit depends upon the amount of internal wear acceptable in the specific application. When mounted, caged roller followers normally placed directly on a hardened ground pin. Compared to knife edge followers, the rate of wear and tear is less due to less friction. Basic types Cam follower types include standard stud, heavy stud, and yoke,.
Although the axis of the follower and the face are at 90° in this example, other angles are in common use. Some types are made of molyfilled nylon to reduce friction between the roller and the end plate or flange. Needle bearing cam followers usually have the lowest speed limit. In the illustration given, point P appears to be the greatest distance, and hence the follower will require to be at least R in radius to keep in contact with the cam profile at this point. Consult the manufacturer to obtain speed limits for specific applications. Load magnitude and direction affects the selection of both bearing size and type.