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EuroWire – January 2012
82
Technical article
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 for all comparisons in this study. The overall lay
lengths measured fall in to a rather tight band. The variation is on
the order of 1% or less, and the mode of the distribution can be
determined with somewhat additional precision.
2.1.2 Individual Pair Measurements
In one experiment, a single twinning machine was set to a
number of process set points, but the lay length set point was
unchanged. A series of pairs were made with no two set points in
immediate succession, and the samples were made in replicate.
Figure 2
shows the comparison of the same lay set points
measured at two different times from the same twinner, but with
all other machine set points identical. This result shows high
repeatability of both the twinner and the measuring technology
when pairs with the same twinner, lay set point and process
conditions are measured.
▲
▲
Figure 2
:
Repeated measurements of replicated trials
▲
▲
Figure 3
:
Different process set points for the same lay length
▼
▼
Figure 4
:
Same lay length produced on two different machines
% Deviation fromTarget
Pair 3
% Deviation fromTarget
Pair 3
% Deviation fromTarget
Pair 1
% Deviation fromTarget
Pair 1
% Dev Pair 1
% Dev Pair 1
% Dev Pair 3
% Dev Pair 3
Frequency
Frequency
Frequency
Frequency
Frequency
Frequency
% Deviation fromTarget
Pair 2
% Deviation fromTarget
Pair 2
% Dev Pair 2
% Dev Pair 2