Control Mechanisms for Print Quality Assurance in HP Indigo Presses

摘要

The challenge of consistently achieving high print quality in HP Indigo digital presses is addressed both by the fundamentals of the liquid, HP ElectroInk™ based electrophotographic printing process, as well as by using a comprehensive set of ingenious control mechanisms. The control loops deal with a wide range of process parameters assuring the accuracy, consistency, and stability of the print quality. We cover the major print quality related automatic control loops. The paper reviews the liquid ink parameters -concentration, conductivity, flow, and temperature. It also explains how the Organic Photo Receptor (OPC) charge and discharge levels are maintained. At a higher system level, we describe a method of verification of stable and accurate image density, gray level control, and color-to-color registration. A method for obtaining accurate dot positioning and approving high accuracy for duplex printing is presented. The paper reviews the main parameters, measurement devices and related algorithms, and shows how they lead to the consistent high-level print quality characteristic of HP Indigo digital presses.