Instrumentation for Roller Nip Studies.

Many graphic arts processes involve rolling contact between cylinders with different elastic properties. In printing presses, the critical functions of applying ink to a printing plate and subsequently to paper are both performed in such contact zones. Much of the art associated with printing lies in the adjustment of conditions in these zones. This paper describes the techniques which have been used at the Springdale Laboratories in an attempt to learn what actually happens within the nip. A test setup has been built to simulate the form roller to plate conditions in a typical high speed magazine press. Instrumentation has been devised to allow measurement of the surface speed of the form roller relative to that of the driving steel cylinder in and near the zone of contact. Additional instrumentation makes it possible to obtain simultaneously oscillograins of the radial and tangential forces acting on an element in the surface of the steel driving cylinder. Tests which have been conducted with this equipment indicate the presence of appreciable relative speed gradients which are functions of the roller construction and operating conditions. The radial and tangential force patterns exhibit considerable speed dependence. The limited testing program which has been conducted to date has confirmed a number of practical and theoretical predictions regarding form roller behavior. The results suggest the existence of an optimum form roller construction which will minimize relative tangential motion within the contact zone.