page_title: Cam
section_title: Disc or plate cam
hierarchical_section_title: Cam / Disc or plate cam
context_page_description: A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path. 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 motion in the follower, which is a lever making contact with the cam. A cam timer is similar, and were widely used for electric machine control before the advent of inexpensive electronics, microcontrollers, integrated circuits, programmable logic controllers and digital control.
context_section_description: The most commonly used cam is the cam plate (also known as disc cam or radial cam)
  which is cut out of a piece of flat metal or plate. Here, the follower moves in a plane perpendicular to the axis of rotation of the camshaft. Several key terms are relevant in such a construction of plate cams: base circle, prime circle (with radius equal to the sum of the follower radius and the base circle radius), pitch curve which is the radial curve traced out by applying the radial displacements away from the prime circle across all angles, and the lobe separation angle (LSA - the angle between two adjacent intake and exhaust cam lobes).
  The base circle is the smallest circle that can be drawn to the cam profile.
  A once common, but now outdated, application of this type of cam was automatic machine tool programming cams. Each tool movement or operation was controlled directly by one or more cams. Instructions for producing programming cams and cam generation data for the most common makes of machine, were included in engineering references well into the modern CNC era.
  This type of cam is used in many simple electromechanical appliances controllers, such as dishwashers and clothes washing machines, to actuate mechanical switches that control the various parts.
caption: Motorcycle transmission showing cylindrical cam with three followers. Each follower controls the position of a shift fork.
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