In designing the cam, the lift and the dwell angle θ are given. This is continuous with a tangent to the tip circle. Thus, in practice, the points at which lift begins and ends mean that a tangent to the base circle appears on the profile. Ideally, a convex curve between the onset and maximum position of lift reduces acceleration, but this requires impractically large shaft diameters relative to lift. Here, the cam profile is commonly symmetric and at rotational speeds generally met with, very high acceleration forces develop. Ī common type is in the valve actuators in internal combustion engines. The rise is the motion of the follower away from the cam center, dwell is the motion where the follower is at rest, and return is the motion of the follower toward the cam center. A simple displacement diagram illustrates the follower motion at a constant velocity rise followed by a similar return with a dwell in between as depicted in figure 2. Displacement diagrams are traditionally presented as graphs with non-negative values. These diagrams relate angular position, usually in degrees, to the radial displacement experienced at that position. In the example shown, the cam rotates about an axis. 2 Basic displacement diagram for a rotating camĬams can be characterized by their displacement diagrams, which reflect the changing position a follower would make as the surface of the cam moves in contact with the follower. A common example is the camshaft of an automobile, which takes the rotary motion of the engine and converts it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders.ĭisplacement diagram Fig. The cam can be seen as a device that converts rotational motion to reciprocating (or sometimes oscillating) motion. A cam timer is similar, and were widely used for electric machine control (an electromechanical timer in a washing machine being a common example) before the advent of inexpensive electronics, microcontrollers, integrated circuits, programmable logic controllers and digital control. The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in the follower, which is a lever making contact with the cam. a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path. It is often a part of a rotating wheel (e.g. Elliptical disk cam with an oscillating follower.Ī cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. 1 Animation showing continuous looking rotating cams producing reciprocating linear motion of the cam followers. For other uses, see Cam (disambiguation). For the part of an engine sometimes referred to as a "cam", see Camshaft.
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