Automatic Gauging for Improved Quality, 1993 International European Extrusion Coating Symposium Proceedings

Ricky Keller

This paper will focus on the theoretical and practical aspects of the factors which effect gauge variation and control in coextruded cast film, extrusion coating and sheet dies.

The theory of polymer flow through a slot die will be introduced as it applies to practical extrusion applications. The effect of change in die gap on the extruded web will be studied. These principles and effects will then be applied to the design criteria for an automatic die system. The following topics will be discussed as they effect process control and film quality.

*Die bolt sensitivity to adjustment

*Die bolt backlash

*Die lip flatness and finish

*Die land area effect

*Measurement sensitivity and noise of measurement

*Plate out on die lip and gel entrapment

*External extrusion and film forming effects

*Stability of die manifold geometries

The future of automatic die systems and a view of areas for improvement will be explored in the conclusion.