Abstract: A printing machine to work corrugated board and the like includes a print cylinder provided with radial holes (E, E?) for emitting compressed air in order to allow the introduction and removal of a print sleeve (S) carrying a print cliché (C), said print cylinder consisting of a fixed shaft (F) on which there is airtightly slidably mounted a mobile cylinder (M) carrying said print sleeve (S), the print cylinder being supported at one end by a dismountable flange with a removable part (R) and by a piston (L) suitable to engage a corresponding seat so to allow the axial movement of said mobile cylinder (M) between a retracted work position and an extended sleeve change position, in which it projects through the machine side to make the change easier, simply by means of the same compressed air used to replace the print sleeve (S).