Abstract: A method for detecting errors in individual color separation images of a multi-color printing machine, in particular an electrophotographic printing machine, comprising a plurality of printing units, is described. Using this method, first a plurality of first register lines is printed with a first printing unit, and a plurality of second register lines is printed with a second printing unit in such a manner that each of the first register lines, together with one of said second register lines, is positioned inside a respective registration frame. Then the plurality of the first and second register lines in the respective registration frame are detected with a register sensor, and an output signal of the register sensor relating to the respective second register line is compared with an intensity threshold value in order to determine whether the second register lines can be recognized.

Abstract: A method for calibrating a printing machine having a plurality of printing units includes transporting a first group of at-least-semi-transparent sheets at least once through the printing units. A second group of at-least-semi-transparent sheets is transported at least twice through the printing units, with the sheets being turned over between passages. Registration marks are printed on one of the sheets of the first group of sheets, and on one of the sheets of the second group of sheets during their second passage through the printing units. No registration marks are printed on the sheets of the second group of sheets during their first passage through the printing units. The registration marks are measured at a registration sensor located downstream of the printing units. Calibration parameters are determined using the measurements of the first and second registration marks provided by the registration sensor.

Abstract: A method for calibrating a position of a first register line in a register mark for a multi-color printing machine, said first register line consisting of a first color that does not offer sufficient contrast with respect to a printing material to allow detection above a determined threshold on a register sensor. A plurality of register marks, each consisting of at least one starting line, a background line and a first register line, is printed, said background line consisting of a second color which offers sufficient contrast with respect to the first color for detection above the specified threshold on the register sensor if the first register line is printed on the background line, and said background line having a width that is greater than the first register line, and said starting line, said background line and said first register line being printed with the use of the pre-determined control parameters, which normally cause the first register line to be printed on the background line.

Abstract: A method of preventing a registration error while printing at least one printing image, wherein, in order to control or adjust the correct length of the printing image, the start and/or the distance of the printing image lines of the printing image are controlled by determining the ratio of the number of rotary encoder signals of a transport web counted during a specific time interval to the number of rotary encoder signals of a cylinder of a printing and by taking into account a change of this ratio as a correction, said ratio being a function of a printing sheet located in a printing nip between the transport web and the printing unit, is characterized in that a changed printing material situation occurring in said printing nip between the transport web and the printing unit is used to achieve registration accuracy immediately.

Abstract: The invention relates to a method and a device for controlling the circumferential register in a digital multi-color printing machine for printing sheets during a printing process, whereby, for each sheet, at least one register mark per color printing unit of the multi-color printing machine is produced, assigned to said sheet and defined with respect to its position, and whereby, based on the determination of the position of the register marks of a sheet, the circumferential register of at least one sheet, which follows the sheet associated with said determined register marks downstream of the printing process, is controlled. In duplex printing a sheet by recto and verso printing with the invention, register marks are applied for each side and, in order to control recto and verso printing of at least one subsequent sheet, said register marks are analyzed.

Abstract: The invention relates to a method of ensuring a correct lateral registration setting, in a digital multi-color electrographic sheet-printing machine, which the sheets adhere to a support, preferably a transport belt, are transported past printing units.

Abstract: The object of the invention is to achieve a correctly positioned print in duplex-printing mode. A method for the detection of marks (1, 1?, 1?) by a sensor array (10) for a printing machine has been provided, whereby the marks (1) on the first (recto) printing side (5) of a sheet (3) are detected, the sheet is turned over and shifted in a direction transverse to the transport direction, and the marks (1?) on a second (verso) printing side (6) of said sheet are detected. Furthermore, a printing machine is provided with an alignment device (40) for shifting a sheet (3) in a direction transverse to the transport direction for the detection of marks (1?) on the second printing side, said marks being offset relative to the marks (1) on the first printing side, after said sheet (3) has been turned over.

Abstract: A device and a method for improving the quality of prints using a printing device and system for carrying out a print job with a digital printing machine, preferably with a printing machine that works with a toner, in particular with an electrophotographically operating printing machine, whereby the sheets (1) are preferably printed by recto-printing and verso-printing, whereby the sheets (1) to be printed are divided into batches, and whereby, in the case of batches that are incompletely occupied with sheets (1), the slots of the missing sheets are replaced by an approximately sheet-sized toner field (3) on the transport belt (4) for the sheets.

Abstract: A method for calibrating a printing machine comprising a plurality of printing units includes transporting a first group of at-least-semi-transparent sheets at least once through the printing units. A second group of at-least-semi-transparent sheets is transported at least twice through the printing units, with the sheets being turned over between passages. Registration marks are printed on one of the sheets of the first group of sheets, and on one of the sheets of the second group of sheets during their second passage through the printing units. No registration marks are printed on the sheets of the second group of sheets during their first passage through the printing units. The registration marks are measured at a registration sensor located downstream of the printing units. Calibration parameters are determined using the measurements of the first and second registration marks provided by the registration sensor.

Abstract: A method for detecting errors in individual color separation images of a multi-color printing machine, in particular an electrophotographic printing machine, comprising a plurality of printing units, is described. Using this method, first a plurality of first register lines is printed with a first printing unit, and a plurality of second register lines is printed with a second printing unit in such a manner that each of the first register lines, together with one of said second register lines, is positioned inside a respective registration frame. Then the plurality of the first and second register lines in the respective registration frame are detected with a register sensor, and an output signal of the register sensor relating to the respective second register line is compared with an intensity threshold value in order to determine whether the second register lines can be recognized.

Abstract: Described is a method for calibrating a position of a first register line in a register mark for a multi-color printing machine, said first register line consisting of a first color that does not offer sufficient contrast with respect to a printing material in order to allow a detection above a determined threshold value on a register sensor.

Abstract: A device and a method for improving the quality of prints using a printing device and system for carrying out a print job with a digital printing machine, preferably with a printing machine that works with a toner, in particular with an electrophotographically operating printing machine, whereby the sheets (1) are preferably printed by recto-printing and verso-printing, whereby the sheets (1) to be printed are divided into batches, and whereby, in the case of batches that are incompletely occupied with sheets (1), the slots of the missing sheets are replaced by an approximately sheet-sized toner field (3) on the transport belt (4) for the sheets.

Abstract: A device and a method using a printing device and system for printing sheets whereby, for each sheet, at least one register mark per color printing unit of the multi-color printing machine is produced, assigned to said sheet and defined with respect to its position, so that in duplex printing register marks are applied to each side. The position of each mark is determined by analyzing the position of the mark assigned to the appropriate previous recto or verso sheet.

Abstract: The invention relates to a method of ensuring a correct lateral registration setting, in a digital multi-color electrographic sheet-printing machine, which the sheets adhere to a support, preferably a transport belt, are transported past printing units.

Abstract: A method of preventing a registration error while printing at least one printing image, wherein, in order to control or adjust the correct length of the printing image, the start and/or the distance of the printing image lines of the printing image are controlled by determining the ratio of the number of rotary encoder signals of a transport web counted during a specific time interval to the number of rotary encoder signals of a cylinder of a printing and by taking into account a change of this ratio as a correction, said ratio being a function of a printing sheet located in a printing nip between the transport web and the printing unit, is characterized in that a changed printing material situation occurring in said printing nip between the transport web and the printing unit is used to achieve registration accuracy immediately.