Prediction of Steady-State Operation in Keyless Lithography

Development of lithographic keyless inking systems at Rockwell Graphic Systems over the past several years has included numerous printing tests on web-fed presses during which ink and dampening solution consumption rates were monitored. Ink, dampening solution, press configuration and metering roller construction were the major system variables. The results were reviewed recently in an attempt to uncover basic principles that might apply to keyless lithographic systems across this spectrum of variables. Doing so required reconsideration of the mechanism by which doctor-blade-scraped celled rollers meter viscous oil-based inks into the press system. Accordingly, cell volume was found to not be a controlling parameter in celled-roller metering of paste inks. Cell area at the surface is important. Applying the new mechanism and actual material-use data from the press trials allowed formulating a simple equation, involving measurable variables, which quite accurately predicts the water-in-ink steady-state condition over a wide range of system variables.