EXPERIMENTAL STUDY OF THE FLOW IN THE METERING NIP OF A METERING-SIZE PRESS

摘要

The metering operation in the transfer-roll coating process is crucial for achieving a good uniformity and suitable thickness of the coating film. Experimental results carried out on a laboratory coater are reported. This coater mimics industrial flow conditions: it has a transfer roll and a metering-rod diameter similar to those found on a pilot coater, it operates at commercial speed, and the cover of the transfer roll is deformable The experimental apparatus is described first. Then, a video analysis of the rib pattern is presented. Some interesting features are shown, in particular the existence of an inertia regime at high speed. The nip flow hydrodynamics are investigated using measurements of the pressure profile. It is shown that the film stability is strongly linked to the flow at the exit of the nip. The analysis of the maximum pressure in the nip, for various fluid viscosities and operating parameters, is represented using a master curve. [References: 18]