Automatic thickness control for extruded stretched polymer - by monitoring twin beam infrared pattern received by comparison with sample

摘要

Extruded and stretched polymer film, e.g. polypropylene is produced with set thickness. The thickness is measured across its width, using a twin-beam infra-red type measuring device with a narrow beam detecting varations in potential extension, the values measured are compared electrically with a pre-set fed-in profile across the width of a sample, and deviations are shown up in a suitable way, e.g. as a curve on a screen. Quick checking contrasted with cutting individual samples and testing, effective by using very narrow measuring beam and passing it through a slit in and vertical to the parallel faces of a receiver window.