Details:
Summary:
The quality of an inker usually has limitations - especially starvation and ghosting - which will be described in detail later on. Earlier publications contain contradictory views and appear to agree only insofar as stating that the quality of inking is influenced by the ink flow ratio. Until now, no experimental work has been re- ported to determine these most important factors reliably and quantitatively on commercial inkers. A suitable method to evaluate the ink flow ratio by measuring the ink film thickness on the form rollers has been developed and is reported here. Taking measurement errors into consideration it has been shown that only a low inertia measuring method can be used. Glass cylinders with a transparent Artex coating and a built-in light source are used as form rollers. The ink film thickness on the rollers is measured by transmitted light and by means of silicon photovoltaic cells. Two different types of commercial inkers were examined and their distribution of ink film thickness and ink flow ratio are discussed. The measured results showed that the two types of inkers had two completely different ink flow ratios of 4.1 : 2.4 : 1 : 1 and 2.15 : 1.45 : 1.2 : 1, respectively. Furthermore, measurement of ink film thickness during printing with two form rollers showed that the splitting of this very thin ink film did not occur in the middle of the film. Instead, the ink film remaining on the form roller after ink splitting is approximately 50 percent thicker than the ink film on the printing plate.