Module 4 : Drives and Mechanisms

Lecture 3 : Cams

5.  Three-dimensional cam or Camoid  

Camoid is a combination of radial and axial cams. It has three dimensional surface and two degrees-of-freedom. Two inputs are rotation of the cam about its axis and translation of the cam along its axis. Follower motion is based on both the inputs. Figure 4.3.10 shows a typical Camoid.

Figure 4.3.10 A Camoid

6.  Applications of cams  

Cams are widely used in automation of machinery, gear cutting machines, screw machines, printing press, textile industries, automobile engine valves, tool changers of machine centers, conveyors, pallet changers, sliding fork in wearhouses etc.

Cams are also used in I.C engines to operate the inlet valves and exhaust valves.The cam shaft rotates by using prime moveres. It causes the rotation of cam. This rotation produces translatory motion of tappet against the spring. This translatory motion is used to open or close the valve. The schematic of this operation is shown in Figure 4.3.11.

Figure 4.3.11 Cam in I.C engine

6.1 Cams in automatic lathes

The cam shaft is driven by a motor. The cutting tool mounted on the transverse slide travels to desired depth and at desired feed rate by a set of plate cams mounted on the cam shaft. The bar feeding through headstock at desired feed rate is carried out by a set of plate cams mounted on the camshaft.

6.2 Automatic copying machine

The cam profile can be transferred onto the work piece by using a roller follower as shown in Figure 4.3.12 . The follower can be mounted with a cutting tool. As the cam traverses, the roller follows the cam profile. The required feature can be copied onto the workpiece by the movement of follower over the cam profile.

Figure 4.3.12 Automatic copying of cam profile