A system for manufacturing free-standing films from work pieces. The valve assembly includes at, at least one end thereof, a retaining assembly which allows the effective sealing against one surface of a ball and retention of the ball in position. The air bag further comprises inside and outside smaller fabrics that are stitched to constitute an inner bag that is installed in the outer bag. The image parameter of the partial region is stored and it, or of a transformation thereof, is composed with a predetermined guide value for the image parameter.