A schileren system for in-line quality control in a film extrusion process

Bernhard G. Zagar

Abstract

This paper addresses the problems arising in continuous film extrusion of thin foils that need to result in optical quality but due to process still not completely understood give suboptimal quality of the resultant foil. The foils show more or less severe chatter marks dependent on certain system parameters like feed rate of the product, temperature of the product casted, spinning rate and differential spinning rate of rolls, cooling rate and so on. An inline capable optical quality measurement system is devised that allows to continuously assess the product quality within seconds after the foil is extruded from the casting unit, thus allowing rapid corrective actions if quality declines below a set standard. It also allows for a continuous documentation of the amount of residual chatter marks for each and every inch of product. The system is based upon a schlieren optical setup able to resolve schlieren-caused refraction of collimated light of less than 1 second of arc.

Keywords

continuous cast extrusion; chatter marks; schlieren technique

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IMEKO-TC14-2007-39.pdf

DOI

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IMEKO TC

TC14 - Measurement of Geometrical Quantities

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