JUNE 2005 507

End Breaks in the Spinning and Weaving of Weavable Singles Yarns

Part 1: End Breaks in Spinning

JAMES LAPPAGE1
Canesis Network Limited2, Private Bag 4749, Christchurch, New Zealand

ABSTRACT
An end break will occur in spinning when the tension in the balloon exceeds the strength
at the weakest point in the yarn, which is at the point of twist insertion and before the fibers
are fully twisted together. Other than gross faults such as slubs, the cause of an end break is
generally a very thin place, the incidence of which can be estimated from the mean linear
density of the yarn and its variance. A good correlation was found between the end breakage
rate and the irregularity (CV%) of the yarn, which appears to be independent of yarn count.
The tenacity of the yarn at a break was estimated to be only about 1.85 g/tex. For wool yarns
which are woven in the warp as singles, end breaks in spinning effectively remove those thin
places which are likely to break in warp ends during weaving. It is recommended that such
yarns be spun at high speed to remove those short, very thin places which might not be
detected in clearing, but which may fail in weaving.

Singles yarns are sometimes used in weaving, when weight fabrics under the stimulus of product opportunity.
that is considered practicable, with the commercial ad- To achieve this, it will be necessary to spin very even
vantage of the savings made in processing, particularly in yarns and to manipulate the weaving process to minimize
the spinning process itself, and by obviating the twisting the stresses put upon warp ends.
process and all which that entails. A second means of This paper provides background information for both
reducing costs accrues from the possibility of spinning spinners and weavers, and indicates how spinning prac-
the equivalent of a particular two-fold yarn using a tices can affect weaving performance. Part 1 discusses
coarser, and therefore cheaper, fiber, when the aesthetics how the spinning performance is determined by the ir-
and other requirements of the end product permit. Ordi- regularity of the yarn, and how the end breakage rate can
nary singles worsted yarns are generally considered to be be predicted. Part 2 discusses the weaving performance
unweavable as warp, unless they are given a further of weavable singles yarn and shows how the end break-
treatment such as sizing. In recent years, new technolo- age rate can be predicted from knowledge of the yarn
gies have emerged for spinning singles worsted yarns, properties, the fabric construction and the peak tensions
which are considered to be weavable as warp; one such developed in the loom. Solospun technology was used
technology is Solospun [4], which requires no additional for spinning the yarns used in this work, as it is readily
treatment and is recommended as an alternative to two- available technology.
fold worsted weaving yarns, and offers all of the above
commercial advantages.
Spinning Performance of Eight Weavable
More exciting to the entrepreneur is the possibility of
spinning much finer weaving yarns and weaving very fine Singles Yarns
fabrics, not previously made in wool. This provides an Eight lots of experimental weavable singles yarns
exciting opportunity for product development, with similar were monitored closely in spinning and weaving, in a
potential to that for the introduction of a new fiber, since the trial comparing yarns spun to two counts and two twist
opportunity exists to put wool into products previously levels. The yarns were spun to nominally 31 and 37 tex,
restricted to finer cotton and synthetic fibers. with 105 and 120 ␣ twist, from 23.4 ␮m (CV ⫽ 23.1%)
It can be expected that the weaving limits of weavable wool which had a mean fiber length of 71.6 mm (hau-
singles yarn will be extended into finer yarn and lighter teur), on a Zinser ringframe, at 9000 rpm spindle speed,
with 50 mm diameter rings and balloon control rings.
1
Two replicates containing about 8 kg of yarn were spun
To whom correspondence should be addressed: e-mail:
jim.lappage@canesis.com for each count and twist level, with some variation in the
2
Formerly Wool Research Organisation of New Zealand Inc. spinning process to produce yarns of differing irregular-

Textile Res. J. 75(6), 507–511 (2005) DOI: 10.1177/0040517505053869 © 2005 Sage Publications www.sagepublications.com
508 TEXTILE RESEARCH JOURNAL

TABLE I. Spinning performance and yarn properties of experimental weavable singles yarns.

Yarn no. 1 2 3 4 5 6 7 8

Linear density (tex) 39.2 38.0 31.5 30.9 31.5 32.0 36.5 36.6
Twist (tpm) 624 545 681 596 596 681 545 624
Mean strength (g/tex) 304 291 219 217 212 199 258 249
Extension at break (%) 23.08 20.26 18.19 17.69 18.39 18.65 23.85 21.16
Irregularity CV% 15.25 15.24 16.54 16.93 16.08 16.05 14.99 14.61
Theor. min. irreg. CV% 13.63 13.84 15.20 15.35 15.20 15.08 14.12 14.10
Irreg. index 1.12 1.10 1.09 1.10 1.06 1.06 1.06 1.04
Faults/km:
Thin (⫺50%) 40 54 149 174 119 111 50 40
Thick (⫹50%) 17 10 30 30 25 20 11 12
Nep (⫹200%) 6 5 8 5 7 6 4 5
Spinning bks/106 m 6.09 9.79 45.37 50.77 10.33 15.67 2.12 3.41
Traveller no. 22 22 24 24 24 24 20 20

ity, to create different end breakage rates in both spin- yarn. The yarn is at its weakest at the point of twist
ning and weaving. Spinning breaks were recorded and insertion, before the fibers are fully twisted together.
the yarn properties tested before winding and clearing. When a very weak place or a gross fault, such as a slub,
These data are given in Table I. occurs in the yarn, the balloon tension may be, or may
The end breakage rates of these eight yarns varied become, greater than the strength at the twist triangle. In
considerably, from a low of 2.12 to a high of 50.77 a well-made roving there should be no slubs, nor the
breaks/106 m. The variation was not consistent with yarn potential for slubs to form in the spinning operation,
linear density or strength, but was consistent with the although slubs can arise from poorly made joins in the
measured irregularity of the yarn and the frequency of slivers fed to the roving frame, for example. Very weak
thin places (–50% level). The end breakage rate is plotted places, however, can occur when even the best spinning
against yarn irregularity in Figure 1. The two nominal practice is followed, because of the random distribution
yarn counts are distributed in two separate groups, but of fibers and the quasi-periodic variations induced by
the points appear to lie on the same curve of increasing drafting; these are the major cause of end breaks. These
end breaks with increasing yarn irregularity, suggesting very weak places are generally very thin places.
that the end breakage rate depends primarily on the
evenness of the yarn, and is relatively independent of The Incidence of Thin Places in a Yarn
yarn count.
The measured irregularity of a yarn is made up from at
least two components, the first being a natural variation due
to the variability of fibers, both between individual fibers
and within a single fiber, and the random way in which
fibers are distributed along a yarn. This component of
irregularity is the well-known ‘minimum irregularity’ de-
fined by Martindale [3], and represents a completely ran-
dom variation in local linear density along the length of a
yarn. The second component is generated because of the
inability of modern processing machinery to perfectly con-
trol fibers during processing, particularly in drafting. The
shorter fibers in the blend cannot be properly controlled
during their passage through the drafting system and a
periodicity related to the mean fiber length is generated in
the yarn. This periodicity has a wavelength approximately
four times the mean fiber length (hauteur) and is commonly
FIGURE 1. Relationship: end breaks versus yarn irregularity.
referred to as the drafting wave.
Usually, several such ‘drafting waves’ are present in a
yarn, since a new drafting wave is introduced at every
Causes of End Breaks in Spinning
drafting step in the processing sequence from top to yarn.
An end will fail in spinning when the tension in the Drafting waves introduced in the earlier stages of process-
balloon exceeds the strength at the weakest point in the ing can often be detected in the yarn, but their wavelength
JUNE 2005 509

is increased by the factor of the draft ratio at every subse- rings. Their findings are summarized in Figure 2, which
quent processing step, and their amplitude is reduced by shows that for a given spindle speed, V, balloon tension, T,
subsequent steps of doubling. The dominant drafting wave is directly proportional to the mean yarn linear density, m,
is that introduced at the last processing step (i.e., the spin- at least for the three spindle speeds studied. The gradient,
ning process). The thinnest thin places in the yarn can be T/m, of each line in Figure 2 is plotted against the square of
expected to occur when a random thin place happens to the spindle speed in Figure 3, and again a substantially
coincide with a thin place introduced by the drafting wave. linear relationship is found where:
The thinnest places can then be expected to be spaced at
least by one wavelength, ␭, of the drafting wave, but places T/m ⫽ KV 2
weak enough to fail in spinning are statistically rare events or
and are spaced by very long lengths of yarn.
The variation in linear density is measured continu- T ⫽ mKV 2, (3)
ously along a yarn by test instruments such as the Uster
where K is the gradient of the line.
Evenness tester. The measured irregularity of a yarn can
The balloon tension, T, defines the maximum strength
be used to estimate the incidence along the yarn of places
of a weak place that will break in spinning. The maxi-
of any given linear density, provided the distribution of
linear density is known.
No reports have been found in the literature of how linear
density is distributed along a yarn. Other work [2] has
suggested that the distribution is normal, or close to normal,
at least for places as frequent as 1/1000. Thin places which
may break in spinning are much less frequent than this, and
it is not certain that the normal distribution can be extrap-
olated to rare events. However, in this work it has been
assumed that local linear density, including rare event thin
places, is distributed normally along a worsted yarn. Allow-
ing this assumption, we can say the probability of finding a
place along the yarn as thin as t tex is given by:

pr共t兲 ⫽ prZ ⬍ ⫺ 冉 冊
t⫺m
␴
(1)

where m is the mean and ␴ is the standard deviation of

the linear density of the yarn, and Z is the normal
probability function. FIGURE 2. Relationship: balloon tension and yarn linear density.
The average length, L, of yarn between places as thin
as t tex is the average length of yarn between the thinnest
places. Because of the predominance of the drafting
wave introduced during spinning, thin places in the yarn
are substantially spaced by the length of the drafting
wave, ␭, and thin places of linear density t, will then be
spaced by L, where:
␭
L⫽ (2)
pr共t兲

Balloon Tension and End Breaks in Spinning

The primary factors determining the tension in the
spinning balloon are spindle speed, balloon diameter, yarn
linear density and traveller weight. A number of authors
have published rigorous theoretical analyses of ring spin-
ning, including Bracewell and Greenhalgh [1] who also
measured balloon tensions for a variety of yarns and spindle FIGURE 3. Relationship: balloon tension/linear density ratio
speeds using 50-mm-diameter rings and balloon control versus spindle speed.
510 TEXTILE RESEARCH JOURNAL

mum local linear density, t, of a thin place at a break Prediction of End Breakage Rate
could be estimated if the instantaneous strength of the
From equation (1), a thin place will just break when
yarn at the point of twist insertion could be related to the
instantaneous linear density. Although yarn strength at Z ⫽ 共m ⫺ t兲/ ␴ ⫽ 共m ⫺ t兲 䡠 100/m 䡠 CV%.
the point of twist insertion cannot be measured directly,
the maximum linear density of a thin place which might Assuming the tenacity of a thin place at a break is 1.85
g/tex,
break during spinning can be estimated from actual mea-
surements of the spinning performance. Knowing the t ⫽ T/1.85
number of end breaks and the length of yarn spun, the
probability of an end break can be calculated by equation Therefore,
(2), and t by equation (1). It is then possible to estimate Z ⫽ 共m ⫺ T/1.85兲 䡠 100/m 䡠 CV%
the tenacity of the thin place at the break. These calcu-
lations were made for the eight weavable singles yarns From equation (3):
spun in this trial, with the results given in Table II. T ⫽ mKV 2,
The parameter Z is determined from tables of the
normal probability function. (End breaks in spinning are and
a statistically rare event and a table of the normal prob- Z ⫽ 共m ⫺ mKV 2/1.85兲 䡠 100/m 䡠 CV%
ability function reading to ten decimal places is re-
quired.) The balloon tension, T, was estimated from the ⫽ 共1 ⫺ KV2 /1.85兲 䡠 100/CV%.
results of Bracewell and Greenhalgh [1], given in Figures From Figure 3,
2 and 3, whose experiments were carried out with a
balloon diameter closely similar to that occurring on the K ⫽ 6.5625 ⫻ 10 ⫺9.
Zinser ringframe. For a given spindle speed of 9000 rpm,
For the (nominally) 37 tex yarns, the average esti-
mated value for ៮t ⫽ 11.15 tex, and for the (nominally) 31 Z ⫽ 71.27/CV%
tex yarns ៮t ⫽ 9.1 tex. The estimated local tenacity (T/t)
This implies that the end breakage rate for a given twist
of a thin place at break varied unsystematically among
is independent of the yarn linear density and is dependent
the eight yarns, as mean T/t ⫽ 1.85 ⫾ 0.15 g/tex and can only upon the irregularity of the yarn, the spindle speed
be considered substantially constant within experimental and, of course, the delivery speed of the yarn.
error. This suggests that the thin places in the yarn that The probable end breakage rates have been calculated
break during spinning are surprisingly weak in the zone for the range of irregularities CV ⫽ 14 to 17%; the
immediately downstream of the front drafting rollers, results are given in Table III.
and before the yarn is fully twisted, compared to the The calculated end breakage rates have been plotted in
average yarn tenacity of about 7 g/tex. Figure 1 in comparison with the actual end breakage rates

TABLE II. Calculations of statistical parameters.

Yarn no. 1 2 3 4 5 6 7 8

L (m) 164 522 102 147 24 905 19 697 96 799 63 436 471 822 293 351
Pr (break) 1.74⫻10⫺6 2.8⫻10⫺6 1.31⫻10⫺5 1.45⫻10⫺5 2.96⫻10⫺5 4.5⫻10⫺6 6.07⫻10⫺6 9.76⫻10⫺6
Z 4.6626 4.5440 4.2012 4.1773 4.5332 4.4385 4.8683 4.9700
␴ 5.978 5.791 5.101 5.314 5.065 5.136 5.471 5.347
t (tex) 11.83 11.68 9.67 9.05 8.54 9.20 9.86 11.22
T (g) 20.88 20.50 17.09 16.58 17.09 17.21 19.74 19.76
T/t (g/tex) 1.77 1.76 1.78 1.83 2.00 1.87 2.00 1.76

TABLE III. Calculated probable end breakage rates.

Irregularity CV% 14 14.5 15 16 17

Z 5.0907 4.9152 4.7513 4.4544 4.1924

Pr bk ⫻ 105 0.018 0.044 0.101 0.428 1.390
L (106 m) 1.590 0.651 0.283 0.067 0.021
Bks/106 m 0.63 1.56 3.53 14.95 48.54
JUNE 2005 511

TABLE IV. Effect on end breakage rate of reducing spindle speed.

Spindle speed (rpm) T (g) t (tex) Z Pr (break) L (m) End breaks per 106 m

9000 16.6 9.05 4.177 1.45⫻10⫺5 19697 50.63

8500 14.8 8.08 4.362 6.46⫻10⫺6 44334 22.56
8000 13.1 7.16 4.538 2.82⫻10⫺6 101560 9.85
7500 11.5 6.29 4.704 1.32⫻10⫺6 216970 4.61

observed. The experimental points follow the theoretical fault in the yarn which can, however, be easily made
curve closely simply because the experimental results have detectable by the clearer. Preferably, weavable singles
been used to “calibrate” the system. A different calibration yarns should be spun at high speed to remove thin places
may be required for a different ringframe and particularly in the yarn which might not survive the weaving process.
for a different fiber blend and yarns other than weavable This may result in an increased end breakage rate, but
singles. This could be done from a mill’s existing records to has the bonus of maximizing productivity.
provide the means of predicting the spinning performance
of any lot from routine yarn tests. Calibration requires only Conclusions
the determination of the tenacity of the thin places in the
spinning triangle. It has been shown that the end breakage rate per unit
length of yarn for a given lot of fiber spun as SoloSpun
weavable singles yarn, under the given spinning condi-
Recommended Mill Practice tions of spindle speed and ringframe, depends only upon
In industry, it is common practice to select the spindle the evenness of that yarn. When the end breakage rate is
speed as a compromise between productivity and the end measured on a time basis, there is also a small depen-
breakage rate. If end breaks occur too frequently, the spin- dence on yarn count, because the twist level, and there-
dle speed is reduced, which reduces the balloon tension and fore the delivery speed, varies with count, which varies
therefore the magnitude of a thin place at an end break. The the rate at which thin places are encountered.
balloon tension is proportional to the square of the spindle The tenacity of the forming yarn was estimated to be
speed, so a small reduction in spindle speed results in a only 1.85 g/tex at the point of break; breaks usually occur
significant reduction in end breaks. in the spinning triangle, where the yarn is not yet fully
In the present trials, Yarn 4 had the worst recorded twisted and is at its weakest.
spinning performance, with an end breakage rate of The end breakage rate can be predicted from a knowl-
50.77/106 m, spinning at 9000 rpm spindle speed (which edge of the evenness of the yarn, the tension in the
is equivalent to a balloon speed of about 8810 rpm, spinning balloon and the tenacity of thin places in the
taking account of the speed of winding yarn on the cop). spinning triangle.
The calculated effect on the end breakage rate of reduc-
ing spindle speed is illustrated in Table IV. ACKNOWLEDGMENTS
Reducing the spindle speed to 8000 rpm can be ex- This work was carried out under a project funded
pected to reduce the end breakage rate by about 83% in partly by the Australian Wool Research and Promotion
this example, to a commercially acceptable rate. This Organisation, and partly by the New Zealand Govern-
may be advantageous for the spinner, even though pro- ment Foundation for Research, Science and Technology.
duction is reduced by 11%, but it may be to the disad-
vantage of subsequent users of the yarn. To achieve an
Literature Cited
acceptable end breakage rate, the balloon tension is re-
duced (in this case to 13.1 gf) and thin places as fine as 1. Bracewell, G. M., and Greenhalgh, K., Dynamical Analysis of
7.2 tex may survive in the yarn. Such thin places may the Spinning Balloon, J. Textile Inst. 44, T266-292 (1953).
then result in end breaks in subsequent processing, par- 2. Lappage, J., The Distribution of Linear Density from Point-
to-point Along Worsted Spun Yarns. Submitted to JTATM.
ticularly in weaving weavable singles yarn. In this re-
3. Martindale, J. G., A New Method of Measuring the Irregu-
spect, end breaks in spinning can be regarded as the first larity of Yarns with some Observations on the Origin of
yarn clearing process, eliminating the very thin places. Irregularities in Worsted Slivers and Yarns. J. Textile Inst.
These thin places are likely to be too short to be detected XXXVI, T35-47 (1945).
in clearing, and the spinning process may provide the 4. Prins, M., Lamb, P., and Finn, N, Solospun – The Long
only option for their detection and removal. End breaks Staple Weavable Singles Yarn, Textile Institute 81st. World
in spinning are usually replaced by “piecenings”, another Conference, Melbourne 2001.