Method for engraving printing cylinders

A method for engraving printing cylinders for rotogravure wherein at least two engraving lanes with predetermined lane widths lying next to one another in an axial direction of the printing cylinder are engraved with an allocated respective engraving element, comprising the steps of:

• before engraving, setting an axial spacing of the at least two engraving elements relative to one another and predetermining an axial reference position for each engraving element, an axial spacing of the at least two reference positions relative to one another corresponding to said predetermined lane widths of the engraving lanes;
• roughly positioning the engraving elements to their reference positions;
• measuring axial spacing errors between the reference positions and actual positions of the engraving elements based on the rough positioning;
• engraving with the engraving elements a sequence of cups into the rotating printing cylinder, and forming engraving control signals for drive of the engraving elements;
• during said engraving, executing with the engraving elements a feed motion along the printing cylinder in the axial direction and with faulty spacings relative to one another caused by the rough positioning;
• and
• compensating the axial spacing errors by a shifted engraving of the engraving lanes on the printing cylinder such that the engraving lanes exhibit said predetermined lane widths despite the faulty spacings of the engraving elements relative to one another.

An engraving machine for engraving at least two engraving lanes having predetermined lane widths that lie next to one another in an axial direction of a printing cylinder with a respectively allocated engraving element, comprising:

• a rotationally seated printing cylinder turned by a first drive;
• an engraving carriage movable in the axial direction of the printing cylinder with at least one second drive;
• engraving elements for engraving the engraving lanes that are arranged displaceable and lockable on the engraving carriage;
• a signal editing unit for generating engraving control signals for the engraving elements;
• a position measuring unit for measuring axial spacing errors between predetermined axial reference positions for the engraving elements and actual positions that the engraving elements have in fact assumed given a rough positioning onto the predetermined reference positions;
• and
• a compensation unit for compensation of the measured axial spacing errors by a shifted engraving of the engraving lanes on the printing cylinder and by a correspondingly shifted provision of the engraving control signal values for the engraving elements.

An engraving machine for engraving at least two engraving lanes having predetermined lane widths that lie next to one another in an axial direction of a printing cylinder, comprising:

• a rotatable printing cylinder;
• an engraving carriage movable in the axial direction of the printing cylinder;
• engraving elements for engraving the engraving lanes arranged displaceable on the engraving carriage;
• a signal editing unit for generating engraving control signals for the engraving elements;
• a position measuring unit for measuring axial spacing errors between predetermined axial reference positions for the engraving elements and actual positions that the engraving elements have in fact assumed given a rough positioning onto the predetermined reference positions;
• and
• a compensation unit for compensation of the measured axial spacing errors by a shifted engraving of the engraving lanes on the printing cylinder and by a correspondingly shifted provision of the engraving control signal values for the engraving elements.

A position measuring unit for an engraving machine for engraving at least two engraving lanes with predetermined lane widths lying next to one another in an axial direction of a printing cylinder with a respectively allocated engraving element that is provided with an engraving control signal, comprising:

• a video camera mounted on a measuring carriage in order to register video images of engraving stylus tips of the engraving elements or of the cups engraved as trials with the engraving elements as actual positions of the engraving elements roughly displaced onto predetermined reference positions;
• the measuring carriage is displaceable in the axial direction of the printing cylinder and is positioned at the predetermined reference positions for the engraving elements;
• an image evaluation unit connected to the video camera is present for evaluating the registered video images in order to determine spacing errors between the reference positions and the actual positions of the engraving elements;
• and
• a unit connected to the image evaluation stage to compensate the spacing errors measured by the position measuring unit by a shifted engraving of the engraving lanes on the printing cylinder and by a correspondingly shifted provision of the engraving control signals for the engraving elements.

A position measuring unit for an engraving machine for engraving at least two engraving lanes with predetermined lane widths lying next to one another in an axial direction of a printing cylinder with a respectively allocated engraving element provided with an engraving control signal, comprising:

• a video camera mounted to register video images of the engraving elements or of cups engraved as trials with the engraving elements as actual positions of the engraving elements roughly displaced onto predetermined reference positions;
• the video camera is displaceable in the axial direction of the printing cylinder and is positioned at the predetermined reference positions for the engraving elements;
• an image evaluation unit connected to the video camera for evaluating the registered video images in order to determine spacing errors between the reference positions and the actual positions of the engraving elements;
• and
• a unit connected to the image evaluation stage to compensate the spacing errors measured by the position measuring unit by a shifted engraving of the engraving lanes on the printing cylinder and by a correspondingly shifted provision of the engraving control signals for the engraving elements.