A method and a device are disclosed for making thin plastic films having two or more layers, which are subdivided and separated in the form of tubular bags for portioned reception of different products, wherein the plastic films are provided with welding seams running substantially transversely to the longitudinal direction with predetermined spacing between one another to form bag-like containers, and the containers are separated from one another by a cutting or separating process, the method being characterized by the steps: a) welding the films with predetermined spacing by means of an ultrasound welding process, maintaining a defined, film-dependent distance between a processing tool and a counter tool while welding; and b) separating the tubular bags welded in this way by means of a mechanical cutting process, with or without reduced ultrasound excitation at the point of the respective weld seams.