Use of Ink Modeling and Volumetric Equations for Closed Loop Control of Optical Density in Coldset Newspaper Applications


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Paul L. Cousineau and Tuba Kuklen


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This paper describes the development and use of ink models, volumetric equations, and machine translations to accurately control process color and black ink optical density in coldset newspaper application using three-color gray and solid black. It will also provide analysis and results from running data collected during actual production runs. There are several enabling procedures and technologies that support the use of this methodology for ink density control. Specifically: o Standardization of raw materials (ink, fountain, plates) o Development of repeatable imaging to the plate substrate o Development of digital controls for newspaper presses o Development of repeatable water application within a tolerance with spray bars o Development of accurate and repeatable metering of ink on a per column basis through the use of digital ink pumps o Development of on-line and off-line scanning spectrodensitometer reading devices o Development of linear curves to control ink and water. Use of optical density as the control feedback mechanism to the press controls and press operators keeps the operating environment on a common platform. There is no translation of the optical density readings as they are read using industry standard spectrodensitometer instruments and used as optical density readings. This provides for sufficient inter-instrument agreement between scanning and handheld instruments. Understanding of cyan, magenta, yellow, and black optical density is ubiquitous among press operators and this reduces the hurdle to accept the ink adjustment methodology. Use of this technology improves end-to-end quality performance available from coldset newspaper applications.

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