An Alternative Computational Method of Trapping for the Print Machine Operators
2011 (English)In: Proc. TAGA (Technical Association of the Graphic Arts), Sewickley, PA, USA: Technical Association of the Graphic Arts , 2011, 363-373 p.Conference paper (Other academic)
In a multicolor offset press the process inks (kcmy) will be printed consecutively on the substrate from oneprinting unit to the other. The printing dots and elements in different process color will be printed either isolated, partly orcompletely overprinted depending on the halftoning. In a multicolor press the inks will be printed wet on wet. That meansthat in the area where process inks overlap each other one or more inks will be printed on another ink which is not dryenough. The adhesive power between the wet inks is different and less compared to the adhesive power between one inkprinted on the top of a less wet ink or even a completely dry ink. The adhesive power between the substrate and printed ink isalso different from the adhesive power of one ink on the top of another one. Depending on this adhesive power and the inks’inner cohesion power the thickness of the second printed ink varies. The thickness or amount of the second printed ink on thefirst one can be determined; its value is called trapping. The amount of the trapping will also be changed due to differentparameters such as ink temperature, dampening, printing speed etc. An important outcome is that the gray balance and thecolor appearance (secondary and tertiary colors) of the printed product also depend very much on the trapping’s amount. Thatshows how important it is to have an explicit value for the trapping. The amount of the second printed inks will bedetermined by trapping formulas. This value should be useful for the printer at the press. Unfortunately, the conventionaltrapping formulas are only useful for the “relative” comparison of trapping between two print products. All the conventionalformulas for trapping only deliver the amount of the second printed ink on the top of the first one in percent. This value for itsown (e.g. 63%) is not really useful and meaningful for print machine operators. There are three different formulas fordetermining trapping. These are Preucil, Ritz, and Brunner. All of them are based on density only. The results of theseformulas are different to each other, especially the Brunner formula differs to the other ones. Here a method will beintroduced which is based on spectrometry and will complement the conventional formulas.
Place, publisher, year, edition, pages
Sewickley, PA, USA: Technical Association of the Graphic Arts , 2011. 363-373 p.
Technical Association of the Graphic Arts Proceedings, ISSN 0082-2299
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-68240ISBN: 978-1-935185-03-1 (print)OAI: oai:DiVA.org:liu-68240DiVA: diva2:416932
TAGA (Technical Association of the Graphic Arts), March 2011, Pittsburgh, PA, USA
Shahram Hauck is Printing process and quality manager at manroland, Germany2011-05-232011-05-132013-12-03Bibliographically approved