To reproduce exactly the motion of the cam to the follower, it is necessary that the two remain in touch at all speeds at all times. The cams can be classified according to the manner in which this is achieved.
1. Pre-loaded spring cam
A pre loaded compression spring is used for the purpose of keeping the contact between the cam and follower.
2. Positive-drive cam
In this type, constant touch between the cam and the follower is maintained by a roller follower operating in the groove of a cam. The follower cannot go out of this groove under the normal working operations. A constrained or positive drive is also obtained by the use of a conjugate cam.
3. Gravity cam
If the rise of the cam is achieved by rising surface of the cam and return by the force of gravity or due to the weight of the cam, the cam is known as gravity cam. However, these cams are not preferred due to their uncertain behaviour.
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