WCA March 2012

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. 2 Experimentation This paper is the outcome of a joint effort of Beta LaserMike and Tyco Electronics to better understand how to measure lay lengths, and correlate those measured values to finished cable performance. In order to develop a better understanding of the measurement capabilities, initial trials on individual pairs were conducted. After the pair lay information was gathered, data was gathered at a cabling line with simultaneous data on multiple pairs. The measurement technology includes a rapid sample rate that allows data to be captured at a rate of several samples per lay length. This rapid sample rate allows the further processing of the data, such as FFT analysis, trend analysis, and statistical evaluation. 2.1 Pair lay studies Initial trials were set up to measure pair lays that used a rewind line. This arrangement provided a simpler setup and allowed the measurement of pair lays across a number of twinning machines. Analysis and experiments were conducted to evaluate the measurement equipment performance as well as the differences seen across lay set points and process equipment. 2.1.1 Nominal lay of individual pairs An example of the distribution of measured pair lay is shown in Figure 1 . The data is in histogram format, with a probability density that reflects the distribution of the lay length data over the length of the pair sample. The x-axis scale has been calculated as a per cent deviation from the target to normalise the variation and the mean ❍ ❍ Figure 4 : Same lay length produced on two different machines

% Deviation from Target Pair 2

Frequency Frequency

% Dev Pair 2

% Deviation from Target Pair 2

% Dev Pair 2

❍ ❍ Figure 2 : Repeated measurements of replicated trials

% Deviation from Target Pair 1

Frequency Frequency

% Dev Pair 1

% Deviation from Target Pair 3

% Deviation from Target Pair 1

Frequency Frequency

% Dev Pair 3

% Dev Pair 1

A new lay length measurement technology 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 ❍ ❍ Figure 3 : Different process set points for the same lay length

% Deviation from Target Pair 3

% Dev Pair 3

% Dev Pair 3

102

Wire & Cable ASIA – September/October 2007 March/April 2012