A first structural unit includes a laser image-setting head, and a second structural unit includes a loading compartment to accommodate a cassette housing having a thermal transfer ribbon on spools having hubs. After a cassette is inserted in the loading compartment, the compartment is closed so that drive rollers engage the hubs without play. To produce a printing plate, the second structural unit is then brought over the first structural unit in the manner of a telescope by a moving device, and the thermal transfer ribbon is brought to the laser image-setting head. The thermal transfer ribbon inserted into the loading compartment is guided by self-centering means so that it does not contact the cassette housing, and is positioned with respect to the plate cylinder by guide rollers. Wear-free and therefore fast ribbon guidance can be performed, and automation of the movement sequences of the thermal transfer ribbon can be achieved.