TYPES OF CAMS

Cams are classified according to:

1. Shape

2. Follower movement, and

3. Manner of constraint of the follower.

2.1.1. According to shape:

1. Wedge and flat cams:

A wedge cam has a wedge W which, in general, has a translation motion. The follower F can either translate or oscillate. A spring is, usually used to maintain the constant between the cam and the follower. The cam is stationary and the follower constraint or guide G causes the relative motion of the cam and the follower.

Instead of using a wedge, a flat plate with a groove can also be used. In the groove, the follower is used. Thus, a positive drive is achieved without the use of a spring.

2. Radial or Disc Cams

A cam in which the follower moves radially from the centre of rotation of the cam is known as a radial or disc cam. Radial cams are very popular due to their simplicity and compactness.

3. Spiral Cams

A spiral cam is a face cam in which a groove is cut in the form of a spiral. The spiral groove consists of teeth which mesh with a pin gear follower. The velocity of the follower is proportional to the radial distance of the groove from the axis of the cam.

The use of such cam is limited as the cam has to reverse the direction to reset the position of the follower. It finds its use in computers.

4. Cylindrical Cams

In a cylindrical cam, a cylinder which has circumference counter cut in the surface rotates about its axis. The follower motion can be of two types as follows:

In the first type, a groove is cut on the surface of the cam and a roller follower has constrained (or positive) oscillating motion. A spring loaded follower translates along or parallel to the axis of the rotating cylinder.

Cylinder cams are also known as barrel or drum cams.

5. Conjugate Cams

A conjugate cam is a double disc cam, the two discs being keyed together and is in constant touch to the two rollers of a follower. Thus, the follower has a positive constraint. Such type of cam is preferred when the

requirements are low wear, low noise, better control of the follower, high

6. Globoidal Cams

A globoidal cam can have two types of surfaces, convex and concave. A circumferential contour is cut on the surface of rotation of the cam to impart motion to the follower which has an oscillary motion. The application of such cams is limited to moderate speeds and where the angle of oscillation of the follower is large.

7. Spherical Cams

In a spherical cam, the follower oscillates about an axis perpendicular to the rotation of the cam. Note that in a disc cam, the follower oscillates about an axis parallel to the axis of rotation of cam.

A spherical cam is in the form of a spherical surface which transmits motion to the follower.