The top weight on the motor shaft rotates in a plane close to the centre of the mass of assembly. Rotation of the top eccentric weights creates vibration in the horizontal plane which causes material to move across the screen cloth to periphery. Increasing the top eccentric mass increases the horizontal throw causing oversize material to discharge at a fast rate. The bottom eccentric weight rotates below the centre of vibrating mass creating it on the screen giving vibration in vertical & tangential planes.

Increasing the vertical component of motion which promotes turnover of material on the screen surface helping maximum quantity of undersize material to pass through the screen. The effective vertical motion helps in minimising blinding of screen by near size particles. The tangential component of motion is controlled by the angle of lead given to bottom weights with relation to top weight