Cams are mechanical devices commonly used to convert rotary motion into linear or vice versa. They consist of a rotating element (the cam) and a stationary element (the follower), which contacts the cam as it rotates. Depending on the shape of the cam, it can produce different types of motion, such as constant velocity, simple harmonic motion, or intermittent motion.
Categories of Cams:
Cams can be divided into two categories: with stoppers and without stoppers.
Cams with stoppers are designed to produce a specific motion profile that includes a period of dwell or pause. The stopper is a protrusion on the cam that prevents the follower from moving during this pause, creating a moment of zero velocity. This can be useful for many applications, such as indexing machines, controlling the timing of valves, or creating intermittent motion in packaging machines.
Cams without stoppers do not have a protrusion and do not produce a dwell period. Instead, the follower moves continuously in a cyclical motion, following the shape of the cam. This type of cam is helpful for applications that require continuous motion, such as conveying systems, printing presses, or cam-driven machines.
Sub-Categories of Cams (With Stoppers):
Cams with stoppers can be divided into two subcategories: positive and friction stop cams.
- Positive stop cams use a physical stopper that prevents the follower from moving, while friction stop cams use the friction between the cam and the follower to create the pause. Positive stop cams are more precise and reliable but require more force to operate and can cause wear on the stopper.
- Friction stop cams are simpler and require less force, but they can be less accurate and may require periodic adjustment.
Shapes of Cams:
Cams can also be designed with different shapes to produce different types of motion. For example, a sinusoidal cam produces simple harmonic motion, while a pear-shaped cam produces an asymmetrical motion profile. The choice of cam shape depends on the application and the desired motion profile.
