In one embodiment of the invention, a motorized surgical instrument including an elongated shaft, a wrist member and a pair of working members with at least one working member moveable relative to other working member between open and closed position, is presented. The elongate shaft includes towards its proximal end a carriage plate that enables independent and controlled motion of the surgical instrument employing plurality of actuators securely held therein. Further, disclosed is a surgical instrument enabling easy and quick replacement of working members.