A drag force sensor on a fountain solution carrier roller surface measures drag force of a fountain solution layer on the fountain solution carrier roller surface in real-time during a printing operation. The measured drag force is used in a feedback loop to actively control the fountain solution layer thickness by adjusting the volumetric feed rate of fountain solution added onto the imaging member surface during a printing operation to reach a desired uniform thickness for the printing. This fountain solution monitoring system may be fully automated.

An optical light reflectance measurement system above an imaging member surface measures fountain solution surface light reflectance interference on reflective substrate portions of the imaging member surface in real-time during a printing operation. The measured light reflectance interference corresponds to a thickness of the fountain solution layer and may be used in a feedback loop to actively control fountain solution layer thickness by adjusting the volumetric feed rate of fountain solution added onto the imaging member surface during a printing operation to reach a desired uniform thickness for the printing. This fountain solution monitoring system may be fully automated.

According to aspects of the embodiments, there is provided a method of measuring the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is measured using a diffractive optical element (DOE) configured with grating surfaces varying in a periodic fashion to hold an amount of fountain solution. When radiated with a light source the combination of the grating surface and the fountain solution therein reduces the scattering of the surface structure (“contrast”) that gives rise to a diffraction pattern. The diffractive optical element can be placed on the printing blanket of the lithography printing system or on a separate substrate.

An apparatus includes a doctor blade, an impression roller, and a housing assembly configured to be selectively securely mounted to a stationary-mounted printing machine cylinder. The housing assembly is also configured to support, in use, the doctor blade and the impression roller relative to an engraving area of the stationary-mounted printing machine cylinder once the housing assembly is selectively securely mounted to the stationary-mounted printing machine cylinder.

A sheet-fed printing press includes a printing cylinder and a high-precision sensor system for monitoring a sheet run in the area of the printing cylinder. At least one gage, which is mounted on the printing cylinder, can be detected by the sensor system. It is particularly advantageous if the sensor system is configured to be self-calibrating. A method for calibrating a sensor system and a method for aligning a sensor system are also provided.

Examples of the preferred embodiments use printed content (e.g., halftones, difference in grayscale or darkness) to determine thickness of fountain solution applied by a fountain solution applicator on an imaging member surface and/or determine image forming device real-time image forming modifications for subsequent printings. For example, in real-time during the printing of a print job, a sensor may measure halftones or grayscale differences between printed content and non-printed content of a current printing on print substrate. Based on this measurement of printed content output from the image forming device, the image forming device may adjust image forming (e.g., fountain solution deposition flow rate, imaging member rotation speed) to reach or maintain a preferred fountain solution thickness on the imaging member surface for subsequent (e.g., next) printings of the print job.

According to aspects of the embodiments, there is provided a method of determining the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is determined by examining optical density of some halftone or solid patch versus laser current level. The apparatus and method uses a variable current signal to dither or perturb the laser imaging system to irradiate a fountain solution layer to create patches at different laser current levels. An aptly programmed controller then process optical density measurements to indirectly estimate fountain solution level.

According to aspects of the embodiments, there is provided a method of measuring the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is measured using a glass roll at a lower temperature than the fountain solution. The lower temperature causes the fountain solution to undergo a change in state and in a solid state the fountain solution crystalizes and changes roll opacity with the thickness of the film. When radiated with a light source the opacity is continuously measured through the surface of the roller. The thickness of the crystallized fountain solution can then be determined via the opacity level increase by the crystallization and the impact to the opacity on the glass roll.

According to aspects of the embodiments, there is provided a method of measuring the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is measured using a diffractive optical element (DOE) configured with grating surfaces varying in a periodic fashion to hold an amount of fountain solution. When radiated with a light source the combination of the grating surface and the fountain solution therein reduces the scattering of the surface structure (“contrast”) that gives rise to a diffraction pattern. The diffractive optical element can be placed on the printing blanket of the lithography printing system or on a separate substrate.

A method operates a flexographic printing press. The press contains a printing cylinder carrying a sleeve with at least one flexographic printing forme or a flexographic printing cylinder and an impression cylinder forming a printing nip with the printing cylinder to print on a web of printing substrate. The method includes automatically adjusting the transport speed of the web of printing substrate as a function of a dot density of the flexographic printing forme, i.e. of a location-dependent density of printing elevations on the flexographic printing forme, or of data computationally derived therefrom, or as a function of gaps of the flexographic printing forme or printing cylinder or data computationally derived therefrom. The printing press advantageously provides a cost-efficient way of producing high-quality prints in an industrial flexographic printing process while avoiding undesired vibration. In addition, the method of the invention advantageously provides further automation of the printing process.