Abstract: A method for determining the presence of slipping of a driven nip roller relative to the web in a web printing press includes systematically changing the speed of the nip driver while monitoring the corresponding change in web tension difference across the nip. The linearity and a slope of the relationship between the tension difference and the speed of the nip driver are determined. When the tension difference is non-linear relative to the speed of the driver or the slope of the relationship is substantially less than an expected slope, then slipping is determined to be present. An operator slip indication may be provided which includes the direction of the slip, positive or negative. The operator may then take corrective action to re-establish a non-slip condition, or automatic corrective actions may ensue.

Abstract: A method for dynamically controlling a driver of a nip roller in a web printing press includes controlling the speed of the driver in a tension-control mode during a phase of printing press operation and in a velocity-control mode during another phase of printing press operation. The controlling of the speed of the driver in the tension-control mode is based on the tension in the web upstream of the nip roller so as to maintain the tension at a desired tension value. The controlling of the speed of the driver in the velocity-control mode is based on a predetermined driver velocity ratio for maintaining the web tension. The tension-control mode may be employed during press start-up as the web accelerates to operating speed. The velocity-control mode may be used during printing operations of the press.

Abstract: An air bar for steering a web of material has a hollow interior subjected to an air bar supply pressure. At least one air jet exit is connected to the hollow interior of the air bar. A metering device is assigned to the hollow interior of the air bar for varying the air pressured formed below the web of material for moving the web of material in a lateral direction.

Abstract: A method for color adjustment and control in a printing press wherein the density spectra of individual process colors as well as the density spectrum of the color of paper are stored with given fractional percentages. The density spectra of at least one measuring point per ink zone on a printing copy and at respective points on a printed product are then measured. The density spectra measured on the printing copy and the printed product are then expressed as a linear combination of the density spectra of the individual process colors and the density spectrum of the color of the paper multiplied by fractions, the fractions being calculated so that the density spectra of the printing copy and the printed product are approximated through the linear combination. In the case of a deviation of the fractions between the printed product and the printing copy, the positions of the ink keys are adjusted so that a match of the density spectra is achieved.