a screen panel for vibratory screening machines can consist of at least one cast , injection - molded or vulcanized perforated plate of elastically flexible material , such as plastic or rubber . it has a multitude of screen openings and crosspieces surrounding them which are interconnected forming one piece and thus the perforated plate . a self - cleaning effect can be achieved with such a perforated plate in the area of each individual screen opening by means of a relative movement of the edges of the screen openings in order to extend the self - cleaning effect to as large an area as possible of each individual screen opening . for this purpose , at least two of the crosspieces surrounding the individual screen openings have a differing bending resistance by means of differing cross - sections and / or reinforcements .