Abstract: In prior art processes of this kind the actual thickness of the extrudate is measured, compared with a reference thickness and the setting regions of an extrusion plant are controlled dependent upon the degree of difference. In order nevertheless to improve the quality of the extrudate in relation to the desired reference thickness, according to the invention the evolution strategy process is used. An increase in the convergence rate can also be attained by taking into account strategy parameters which can be deterministically or stochastically changed, whereby mixing including fixedly settable strategy parameters is also possible. In particular, knowledge of the process can be involved as qualitative process partial knowledge.

Abstract: A device for crosswise stretching and fixing of plastic sheeting includes a chain carriage (5) which has an positionally adjustable first roller (7') and a second roller (7) mounted thereon. Tension, resulting from tractive forces transmitted when the chain carriage (5) travels in a running direction, is translated into a prestress force directed substantially in the crosswise direction of a guide rail (11). The prestress force holds the adjustable first roller (7') in constant prestress contact with a first running surface (1") of the guide rail and the second roller (7') in steady contact against a second running surface (1') of the guide rail.

Abstract: Conventional clips must be manufactured with high precision and run the risk of becoming stiff in the course of time or even to become inoperative in extreme cases due to sediments in their pivoting mechanism. In order to obtain a clip which remains operational in spite of sediments and the danger of clogging and which is furthermore easy to assemble and disassemble, the clip lever is supported with a first bearing part on another bearing part on the side of the clip body, forming a kind of rocking bearing. The rocking bearing can in particular be composed of a knife-edge or rolling bearing. This clip is particularly useful for plastics stretching machines.