Abstract: A printing unit has at least two lateral frame parts. The distance between which can be changed, relative to each other, in a horizontal direction. Each frame part receives a printing group or parts of such a printing group. At least one of the lateral frame parts is displaceably supported for movement between a functional position, in which the lateral frame parts meet and are affixed relative to one another, and an open position in which the lateral frame parts are positioned at a distance from each other. The support of the at least one movable lateral frame part has at least one sliding surface which is made using a composite plastic that is composed of multiple materials.