plate cylinder 11 12 is assigned a device 16 17 for fully automatic or semiautomatic printing plate exchange the sheet stack 8 rests on a stack board 10 that can be raised under control the sheets 7 are removed from the top of the sheet stack 8 by means of what is known as a suction head 18 which inter alia has a number of lifting and dragging suckers 19 21 for separating the sheets 7 furthermore blowing devices 22 for loosening the upper sheet layers and sensing elements 23 for stack tracking are provided in order to align the sheet stack 8 in particular the upper sheets 7 of the sheet stack 8 a number of side and rear stops 24 are provided as seen in the sheet transport direction a pre stacking station 26 is arranged upstream of the sheet stack 8 referring now to fig2 the pre stacking station 26 has milling devices 27 which are arranged such that they can be moved on vertical guides 29 the milling devices 27 each comprise a cylindrical milling head 32 which has a drive motor 33 the latter is fixed to a carriage 34 which can be moved up and down by means of a drive device.