Classification of Cam and Cam-Followers
There is not a general classification for cam mechanical systems. However, the 'functional embodiments' and 'functions' of each sub-system have relatively few possibilities, which we can classify.
A General Classification of Cam and Cam-Follower Types:
The general shape of the cam is generated by the interaction of the cam and follower motions.
Rotating Cams:
| • | Planar: the cam is disc, plate, flat |
| • | Spatial: the cam is cylindrical, barrel, globoidal |
Translating Cams:
| • | Planar: the cam is a slot, linear curve or ramp |
| • | Spatial: the cam is a slider-cylindrical, barrel |
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The modes of cam motion are.
Rotating Cams:
| • | The cam swings back and forth; the cam 'oscillates' |
| • | The cam rotates continuously |
Translating Cams:
| • | The slide back and forth; the cam 'reciprocates' |
Stationary Cams:
| • | The cam is a plate that is nominally 'Circular', fixed to a frame [most common on rotating machinery - such as bottle labelling, capping and filling machines]. |
| • | The cam is a ramp that is nominally 'Linear', for example it is a 'slot' or 'ramp'. |
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The modes of cam-follower motion are:
Rotating Followers: a 'lever'
| • | Swing 'back and forth', the lever 'oscillates' |
| • | Progressive motion, they index, in one direction |
Translating Followers: a 'slider':
| • | Sliding 'back and forth' , the slider 'reciprocates' |
Stationary Followers:
| • | The Stationary Cam-Follower moves the Cam, not as common, molding machines, wedge |
| • | A stationary follower might be used to position a cam part, like a 'wedge' cam. |
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The shape of the cam-follower influences the shape of the cam. There are advantages of each shape.
| • | Barrel [also called a Crowned Roller], Logarithmic |
| • | Knife-edged - not a practical cam-follower, but included here for completeness |
See Cam-Follower Shapes
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The constraint between the cam and the follower influences whether the cam is 'open' or 'closed'.
Force Closed
The constraint between cam-follower and the cam is with:
| • | Gravity, Spring, Air-Cylinder, ... |
When the track is 'Force Closed', the follower has one contact point/line with the cam.
Form Closed [also called Body Closed Cams]
The constraint between the cam-follower and the cam is with a:
| • | Groove (Track), Rib, Slot, within which the cam-follower is held. |
| • | Conjugate Cams: these systems require manufacturing and production accuracy. |
When the track is 'Form Closed', the follower can have two contact points/lines with the two cams.
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Non-progressive:
The follower returns to the same position after each cycle by reversing its direction of motion at some point in the cycle.
Progressive:
The follower moves progressively to a new position at the end of each cycle.
The term 'indexing' (see Indexing Cams) is also used for progressive motions.
In most cases the follower is replaced by another follower at the end of a motion cycle. Equally spaced followers return to their original positions after a number of motion-cycle. Most indexing systems use several roller followers equally spaced around a follower wheel or 'turret'.
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Cam : General Motion