Application of a Dynamic Measurement Technique for the Investigation of the Causes of Dot Gain in Web Offset Lithography

The purpose of this work is to identify the causes of dot gain in web offset lithography. To do this a system was assembled to dynamically measure, calculate, and record the individual components of dot gain (fill-in and slur) during normal operation of a web offset press. Using this system, experiments (24 factorial) were run to test the effect of a total of six factors on fill-in and slur. Analysis of variance of the data show that of the factors tested, solid ink density had the largest effect on fill-in and a smaller, but inverse effect on slur. A large increase in blanket packing had a surprisingly small effect on both fill-in and slur., and water amount, paper tension, press speed, the number of press units on impression and all interactions have no effect on dot gain. Fill-in is shown to be the largest component of dot gain. slur., and water amount, paper tension, press speed, the number of press units on impression and all interactions have no effect on dot gain. Fill-in is shown to be the largest component of dot gain.