fly wheel will create a balancing effect for the cam shaft .. and also they will reduce jerks of cam ...and also they will store energy

Punching metal takes an enormous amount of power, as the area under the curve of the stress-strain curve is energy stored, and punching happens pretty quickly. A lot of energy is absorbed during plastic deformation.

If you subject an system directly to this kind of shock, it does not handle it well. The use of a flywheel allows the momentum of the flywheel to do the work instead of putting it directly on the engine. It allows the engine to run at a more regular velocity, to have less wear on the engine, and it allows punching of tougher materials.

Chirs is right, Flywheel stores power to exhort on the Ram (Tonnage). It reduces the load on the Motor.

If there were no flywheel, the punch would require a very large motor in order to provide the required power for the punch stroke. When not in the punch stroke, all that power would be essentially idle, waiting to be called upon for a brief period for the punch operation.

By including the flywheel, you have a means to store up energy, and make it available as needed during the punch operation. Then, during the idle period, the motor pumps energy back into the flywheel to bring it back to full speed.

DrD

Plz describe the working of EGR and how it operate??

DrD is correct about the motor size. The flywheel is the larger pulley than the drive pulley (notice the belt attached in the pic?). In principle it spins more slowly, which inversely gives it much greater torque. 

Also, they're usually  connected to a clutch so that theu can engage or disengage without the threat of damaging the drive shaft.