EoW January 2012

Technical article High speed laser gauges for lay length measurement and FFT analysis for assessment of process stability By Stephen Pearson, Tyco Electronics, Greensboro and Kenneth E Cornelison, Beta LaserMike, Dayton

Abstract In this paper, we describe the work done to evaluate crosstalk performance in Category 5 and higher data communication cables. Specifically, a new technology was introduced that allows the accurate measurement of the lay of pairs. In addition this technology provides information about the variability of the lay along the length of the pair. We show in this paper how the pair lay length as well as the variation of the lay affect the crosstalk performance. Unlike designs that intentionally induce changes in lay length, the effects discovered and described occur as part of the mechanical operation of the pairing and cabling equipment. We have shown that by changing set points on the machines other than the lay setting itself, changes in the crosstalk performance of finished category cable performance occurs. These changes in performance are also accompanied by changes in the lay length values, even with the same lay length set points on the machine. 1 Introduction It is well known in the industry that crosstalk is a key characteristic for high performance category cables. manufacturers guarantee crosstalk performance better than industry standards. This high level of performance requires the implementation of a solid product design and stable manufacturing processes. It is also well known that even with a solid design, In many instances,

% Deviation fromTarget Pair 1

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% Dev Pair 1

▲ ▲ Figure 1 : Example of lay length distribution

This can also be a significant barrier to production scheduling, since often only certain ‘qualified’ equipment can be used on specific products. A new lay length measurement tech- nology has been developed that allows high speed acquisition of lay length data. With this technology, lay lengths can be accurately measured across different machines. This information can be useful in a number of ways. For instance, each machine on a production floor could then be adjusted to deliver a single desired lay value. The variation around the nominal lay is also an important factor that contributes to the crosstalk of the completed cable. We show that effects such as the double twist bow rotation as well as the pretwist of the single wires are quite visible in the analysis of pair length variation. In some cases, even variation caused by the rotation of the payoff and take up spool can be seen in the pair lay data.

excessive process variation will reduce crosstalk performance. Changes in performance may occur quickly in the case of a specific machine or process upset. Changes in performance may also occur slowly over the course of days or weeks that are often caused by gradual changes in the operation of the manufacturing equipment. It is not uncommon to implement scheduled maintenance of equipment to reduce the instances of performance degradation, but the effectiveness of that maintenance to control the lay length attributes has not been understood adequately. Another key factor affecting crosstalk performance is the consistency of lay lengths across a number of different machines. It is known, or at least previously suspected, that the lay length can be different from machine to machine. Managing the use of different machines on a factory floor without good feedback on the actual pair lays is often a problem.

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EuroWire – January 2012