Automated CtP calibration system in an offset printing workflow

Abstract

Although offset printing has been and still is the most common printing technology for color print productions, its print productions are subject to variations due to environmental and process parameters. Therefore, it is very important to frequently control the print production quality criteria in order to make the process predictable, reproducible and stable. One of the most important parts in a modern industrial offset printing process is Computer to Plate (CtP), used for printing plate production. One of the most important quality criteria for printing is to control the dot gain level. It is crucial to have the dot gain level within an acceptable range, defined by ISO 12647-2:2013. This is done by dot gain compensation methods in the Raster Image Processor (RIP). Dot gain compensation, which is also referred to as CtP calibration is, however, a complicated task in offset printing because of the huge number of parameters affecting dot gain. The conventional CtP calibration methods for an offset printing process, which are very time and resource demanding and hence expensive, mostly use one to five dot gain correction curves as the maximum. The proposed CtP calibration method in this paper calibrates the dot gain according to ISO 12647-2:2013 recommendations fully automatically parallel to the print production. Besides that, there is no limitation of the number of the needed dot gain correction curves. This automated CtP calibration method, which is much more efficient and economically beneficial compared to conventional CtP calibration methods, also makes the printing production very accurate in terms of dot gain value.