The in-line ultrasonic measurement of wall thickness has been a common quality manufacturing tool for many years in the medical tubing extrusion field, most commonly for medical applications where documented quality is paramount. Recent years have seen the application of this measurement technique to wire and cable jacketing where significant material savings provide for a very attractive investment return. Now this valuable quality tool can also be applied to many of the key constructions in the fiber optic arena including tight buffer, loose tube and cable jacketing. Ultrasonic wall thickness measurement provides the unique ability to directly measure wall thickness at the beginning of the extrusion line which allows for optimum die centering by an operator. A real-time display of the wall about the core immediately shows the results of a centering effort such that subsequent changes can be made as needed to further optimize the wall balance. Without this capability, the manufacturer is dependent on sample checking at the end of the line on start-up. Quite often, a manual change to the die can effect an over correction and begin a process of multiple changes which are time consuming and will still end up with a less than optimum result. Therefore, human nature intervenes and the operator will eventually tend to "leave well enough alone." Beyond optimum die centering, measurement at the die enables a much faster control response when the system is set to control average or minimum wall thickness. Continuous wall thickness measurement, of course, also enables detailed quality documentation as with other measured parameters.
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