Details:
Summary:
Ink viscosity has a significant impact on the ink transfer and colour in gravure printing. An evaluation of the use of automation compared with manual viscosity control was undertaken on a 5 colour web gravure press. The press was first operated with manual measurement control of solvent addition. The adjustments and corresponding colour were noted. The installed automatic viscosity control was used for monitoring. The trial was then repeated with the control of solvent addition by the automatic viscosity measurement system and manual monitoring of viscosity by the operators, with corresponding sample colour. Under manual control the colour varied significantly, whereas a more consistent result was obtained using the automatic system to control solvent addition. This difference can be ascribed to intrinsic measurement errors in the use of the flow cups to measure viscosity, highlighted in both the preliminary evaluation of the operators and the comparison with on the press automatic viscosity control system.