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: [also called 'indexing', see also Indexing Cams) ]
The follower moves progressively to a new position at the end of each cycle.
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