QUALITY MANAGEMENT

Application Report

Management of outlier
bobbins in ring spinning mills

Textile Technology / June 2008 / SE 623

THE STANDARD FROM FIBER TO FABRIC

Editorial Team:
Richard Furter

© Copyright 2013 by Uster Technologies AG. All rights reserved.

All and any information contained in this document is non-binding. The supplier
reserves the right to modify the products at any time. Any liability of the supplier for
damages resulting from possible discrepancies between this document and the
characteristics of the products is explicitly excluded.

veronesi\TT\Application Reports\QualityManagement\SE-623_Management of outlier bobbins in spinning mills

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Contents

1 Introduction ............................................................................... 5

2 Where do outlier bobbins come from? .................................... 5

3 Tools for the detection of outlier bobbins ............................... 6

3.1 Description of the detection principles ......................................... 6
3.2 Seldom-occurring yarn faults and inferior quality
characteristics ............................................................................. 6
3.3 Limitations of online systems ....................................................... 8
3.4 Criteria to select the limits for quality characteristics .................... 8
3.5 Installation of a quality management system to eliminate
outliers....................................................................................... 11
3.6 Tracing back outliers bobbins to the source ............................... 12
3.7 Examples from the industry ....................................................... 14
3.8 Recommendations for a sampling plan ...................................... 15

4 Role of the laboratory in a modern spinning mill .................. 17

4.1 Tasks of a modern laboratory .................................................... 17
4.2 Sample testing........................................................................... 18
4.3 Elaboration of yarn quality profiles for customers ...................... 20
4.4 Development of new yarns ........................................................ 20
4.5 Analysis of outliers..................................................................... 22

5 Conclusion ............................................................................... 22

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1 Introduction
With the introduction of electronic textile laboratory systems a few decades
ago most of the spinning mills have started to systematically take samples
in the production area (Fig. 1). With this method quality managers could
establish a quality management system with which the influence of the raw
material, the spinning machinery, the environmental conditions, etc., could
be analyzed.

Spinning
Blowroom Spinning Winding
preparation

Elimination of
Improvements
disturbing yarn
faults with clearers
Sample
testing Testing of
Laboratory fibers, slivers Fig. 1
rovings, yarns Testing system found in
most of the spinning mills

With such quality improvement methods it is also possible to establish qual-

ity statistics for each article or each machine and to compare the quality
level of the mill with competitors by means of international benchmarks,
e.g. the USTER® STATISTICS.

It has to be taken into consideration, however that spinning mills mostly

have more than 20’000 production positions. Therefore, a mill has to expect
many outlier bobbins every day. An outlier bobbin can be characterized as
a bobbin which, when processed into a woven or knitted fabric, can be rec-
ognized by the human eye as a defect either in grey fabric or after dyeing.
The quality characteristics of such bobbins deviate from the tolerance band
throughout the bobbin and may also lead to manufacturing problems in
subsequent processes.

This paper deals with proven methods how outlier bobbins can be con-
quered in a ring spinning mill.

2 Where do outlier bobbins come from?

A ring spinning mill differs from many other industries by the high number of
production positions. In order to produce 5 to 20 tons of yarn per day it is
required to install 20’000 to 30’000 ring spinning positions which are oper-
ated 24 hours per day, 7 days per week. The daily production very much
depends on the yarn count.

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Therefore, the risk of having worn out or defective machine parts such as
card wires, rollers of drawboxes, ring travelers, spindles, etc., which pro-
duce outlier bobbins every day, is very high.

One single yarn in a woven or knitted fabric which is beyond the tolerance
limits can deteriorate the entire fabric.

Therefore, there is a considerable interest in all spinning mills to detect

such bobbins and to eliminate them from the spinning process.

3 Tools for the detection of outlier bobbins

3.1 Description of the detection principles

In order to speed up the recognition of outlier bobbins the capabilities of on-

line and off-line systems have to be combined. Table 1 shows the proper-
ties of off-line and on-line systems.

Off-line: On-line:
 Sample testing  100% monitoring
 High reproducibility  Detection and elimination of
seldom-occurring events
 High accuracy
 Enormous amount of data
 Interlaboratory comparison
 Sound statistical platform
 Comparison with benchmarks Table 1
Capabilities of off-line
 Trend analysis
and on-line systems

Table 1 underlines that on-line systems have one particular characteristic:

100% of all yarns are tested. In an average size spinning mill about 1 mil-
lion km of yarn is produced per day.

3.2 Seldom-occurring yarn faults and inferior quality char-

acteristics

When using on-line systems for the measurement of 100% of all bobbins
we have to distinguish the following:
 There are some seldom-occurring yarn faults which are disturbing in a
fabric and which have to be eliminated with a yarn clearer on the wind-
ing machine (Fig. 2).
 There are some deteriorations of quality characteristics of a bobbin
which can considerably downgrade a fabric and which concerns the en-
tire bobbin (Fig. 3).

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Fig. 2
Seldom-occurring faults /
Thick place on the left, for-
eign fiber on the right

Disturbing faults must be eliminated on the winding machine. However,

every cut has to be replaced by a splice. The number of cuts per 100 km
varies in the textile industry between 10 and 70 for each of the above men-
tioned yarn faults.

Bobbins which have quality problems such as high unevenness, high num-
ber of imperfections, excessive hairiness, periodic faults, high cut rates,
have to be ejected at the winding machine, because these inferior quality
characteristics are not seldom-occurring events, but available throughout
the bobbin.

Fig. 3 shows 2 different types of quality problems (knitted fabric on the left,
woven fabric on the right).

Fig. 3
High unevenness on the left
and high hairiness variation
on the right

The clearer has the capability to measure unevenness, imperfections, hair-

iness, etc., and, therefore, can separate the bobbins with excessive quality
characteristics.

Fig. 4 represents on a historical overview what kind of disturbing faults can

be corrected directly on the winding machine because they are seldom-
occurring events.

Bobbins of inferior quality characteristics throughout the bobbin can be rec-

ognized and, afterwards, the bobbins can be ejected at the winding ma-
chine.

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100% check of bobbin quality

Bobbins with
wrong counts
Bobbins with
inferior quality
Corrections on the
winding machine
Bad splices

Polypropylene
fibers
Colored
foreign fibers Ejection of
bobbins at
Disturbing winding
thin places machine

Disturbing
thick places
Fig. 4
45 years Quality problems which
could be conquered in the
past 45 years

In Fig. 4 it is also demonstrated that a significant part of the existing quality

problems in yarn manufacturing can be detected with modern yarn clearers
and that we are approaching the 100% line. This line is the reference and
the long-term objective to get rid of all disturbing faults which may occur
within a specific spinning process. Fig. 4 also explains that spinning mills
have a tool available today with which they can handle many quality chal-
lenges in spinning mills today.

3.3 Limitations of online systems

As already mentioned, a yarn clearer has the capability to separate outlier

bobbins from the production line. However, the clearer is not an ideal tool to
analyze outlier bobbins in order to find the sources of inferior quality. For
this purpose the laboratory systems offer much more options.

3.4 Criteria to select the limits for quality characteristics

Bobbins which exceed the selected limits of quality characteristics have to

be ejected at the winding machine. For this purpose we first have to dis-
cuss the characteristics which can be detected with a modern yarn clearer:

 Unevenness  Hairiness
 Frequent thin places  Periodic faults
 Frequent thick places  Excessive cuts
 Frequent neps  Clusters of faults

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For establishing a real quality management system it is of utmost im-

portance that selections made by the yarn clearer with respect to quality
characteristics can be verified in the laboratory.

The following are a few examples to explain what this means.

Fig. 5 represents the monitoring of a yarn unevenness on the winding ma-

chine (USTER® QUANTUM) and in the laboratory (USTER® TESTER 5)
over a period of 84 week. It can be noticed that the unevenness is increas-
ing in the first year from 12,8 to 13,0%. After the 55th week the unevenness
is increasing considerably. This increase is shown by the yarn clearer and
also by the evenness tester in the laboratory.

This indicates that we can analyze the ejected bobbins in the laboratory
and find the origin with all the evaluation options which a laboratory system
can offer.

CVm [%], UT5 CVm [%], UQC

13.4 13.2

13.3 13.1

13.2 13.0

13.1 12.9

13.0 12.8

12.9 12.7

12.8 12.6

12.7 12.5
12.6 12.4

12.5 12.3

12.4 12.2 Fig. 5

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 Weeks Evenness CVm, Count:
USTER® QUANTUM (UQC) ® Nec 30, ring-spun yarn,
USTER TESTER 5 (UT5)
cotton, combed

Fig. 6 shows an example of a comparison of thick places on the machine

and in the laboratory over a period of 48 weeks.

50 40
45
40 35
35
UQC (+50%)
UT5 (+50%)

30 30
25
20 25
15
10 20
5 Fig. 6
0 15 On-line monitoring of thick
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 35 37 39 41 43 45 47 Weeks places / Count: Nec 30,
USTER® QUANTUM (UQC)
ring-spun yarn, cotton,
USTER® TESTER 5 (UT5)
combed

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Fig. 7 shows the determination of hairiness on the machine over a period of

34 weeks.

Hairiness

4.65

4.55

4.45

4.35

4.25
Fig. 7
On-line monitoring of hairi-
4.15 ness / Count: Nec 30, ring-
0 3 6 9 12 15 18 21 24 27 30 33 Weeks
spun yarn, cotton, combed

In week 10 a massive increase of the hairiness can be noticed.

Fig. 8 shows the distribution of the hairiness of another yarn batch on the
winding machine. A threshold was selected to separate the bobbins which
exceed the warning limit. Yarns with hairiness values beyond the warning
limit can be recognized in a woven or knitted fabric.

Frequency
300

250

200

150
Selected limit for
separating bobbins
100

50

0 Fig. 8
and higher
3.27

3.42
3.50
3.58
3.65
3.73
3.81
3.89
3.96
4.04
4.12

4.58
2.80
2.88
2.96

3.11

3.34

4.20
4.27

4.43

4.66
3.03

3.19

4.35

4.51

On-line hairiness measure-

ment / Count: Nec 40, ring-
Hairiness
spun yarn, cotton, combed

Fig. 8 shows the distribution of the hairiness measured on a winding ma-

chine on 2500 bobbins.

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3.5 Installation of a quality management system to elimi-

nate outliers

In the previous chapters it was explained in detail how modern quality

management tools can contribute to the improvement of the performance of
a spinning mill. However, we identified some areas where the mill manag-
ers and the quality managers still suffer. One significant quality problem are
outlier bobbins. Since one single thread in the warp on a weaving machine
can downgrade the entire woven fabric, it is of utmost interest to get rid of
outliers.

Therefore, a well organized spinning mill has a maintenance and repair

crew which permanently improves outliers among the production positions.
The repair crew, however, needs input from the laboratory where systemat-
ic quality analyses are made.

Fig. 9 shows the principles of operation in a modern spinning mill.

Blowroom Spinning Winding

Spinning
preparation

Back to normal
Improvements distribution

Fig. 9
Analysis of The bobbins which are
Laboratory ejected bobbins
Outliers ejected by the winding ma-
Warning limit chine are analyzed in the
Testing of Yarn quality
fibers, slivers profiles for laboratory. Outliers are
rovings, yarns
Comparison with customers brought back to the normal
USTER® STATISTICS
distribution.

The bobbins of individual spinning machines are marked to identify the pro-
duction positions where the ejected bobbins came from.

The ejected bobbins are brought to the textile laboratory where the quality
problems are evaluated. The findings are listed on an instruction sheet for
the repair crew. It is the intention to bring back the outliers to the normal
distribution (Fig. 9).

The maintenance and repair crew has to undertake the repair works at the
machines (Fig. 10). Successful repairs are reported back to the laboratory.

100% bobbins
Repair crew Spinning process Winding machine

Action successful? Ejected outliers

Action plan for

Laboratory
repair crew Approx. 50 to 100 bobbins daily
Fig. 10
Recommendations for a
Outlier bobbins systematic quality
Second grade bobbins
management

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Bobbins which are recognized as having tolerated quality characteristics

will go back to the yarn batch. The outlier bobbins will be handled as sec-
ond grade bobbins and eliminated from the production.

3.6 Tracing back outliers bobbins to the source

Bobbin identification method

The easiest way to trace back outlier bobbins is the designation of each
bobbin with the number of the spinning position. This identification can be
realized for one ring spinning machine within 20 minutes.

Fig. 11 shows the identification of the bobbins.

Ejected bobbins from

winding machine Entry of marked spindle
Laboratory in action plan

Action plan
for repair crew
Marking of spindle
position

Fig. 11
Identification of spinning
positions for one doff

If the winding machine ejects a bobbin from this ring spinning machine, it is
easy to find the spinning position where the bobbin was produced.

Therefore, it is recommended, particularly in low cost countries, to desig-

nate the bobbins of one doff and one machine every day. In a medium size
spinning mill of 20’000 to 30’000 spindles it will last approximately 20 to 30
day to check and trace back all the outlier bobbins in a mill.

Identification process:
 The spinning mill establishes a test plan which ring spinning machine
has to be tested at what day.
 All the bobbins of this machine are identified for one doff so that the
laboratory operators know where the ejected bobbin came from.
 The production position which produced the ejected bobbin is entered
into the action plan for the maintenance and repair crew.
 The maintenance and repair crew receives an action plan from the la-
boratory.

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Fig. 12 shows part of an action plan for the maintenance and repair crew.
The yellow part is filled in by the laboratory staff. This part also has a col-
umn where the laboratory operators insert the expected source of the fault.

The green part of the action plan is filled in by the repair crew. They also
confirm if the expected source proposed by the laboratory staff was correct.
If the crew finds another fault, the technical problem is described in detail.

The action plan goes back to the laboratory the same day when all the ac-
tions are finished.

Machine Spinning Detection Expected Source found Action Time Signature Date
position in source by repair crew taken for
laboratory repair
14 231 Peak in Damage Contamination Cleaned 10 min June 25,
RSM spectrogram on front of front roller front roller 2007
at 8 cm roller, ring due to
spinning honeydew
14 284 High Ring Ring traveller Replaced 5 min June 25,
RSM periodic traveller worn out ring 2007
hairiness travellers
3 Periodicity at Conta- Same Cleaned 10 min June 25,
Finisher 28 m mination of drawbox of 2007
drawframe drawbox of finisher
Fig. 12
finisher drawframe Systematic repair of defec-
drawframe tive production positions

Lessons learned with the first systems in mills:

 The yarn monitoring system on the last machine in the spinning process
also has to check the quality characteristics.
 The monitoring of the quality characteristics on the winding machines
offers new opportunities to considerably lower the daily outlier bobbins.
 Modern on-line systems support spinners to keep the quality of every
yarn package within pre-set limits.

Outlier bobbins produced by non-identified spinning positions

As has been mentioned above, the bobbins of all spinning positions are
identified once in 20 to 30 days. This method allows a precise tracing back
of outlier bobbins to the source of the problem.

However, in a spinning mill with 25 ring spinning machines there are 24

machines which deliver non-identified outlier bobbins to the laboratory via
the winder at a certain date. If there is a clear assignment in the mill what
kind of bobbins were processed on what winding machines, it also allows
the assignment of the type of problems at least to a specific spinning ma-
chine.

If a spinning mill uses link systems, the back tracing of the bobbins to the
ring spinning machine is easy. In spinning mills with stand alone winders it
depends on the organization of the mill.

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Example: If more and more non-marked bobbins exceed the hairiness

thresholds, it may be time to replace the ring travelers.

3.7 Examples from the industry

The closed loop system was tested in the industry with considerable suc-
cess. If the clearer really can detect quality deviations from established
benchmarks, it will also be possible for the quality specialists to trace back
the yarn faults to the origin. The following are a few examples where faults
could be traced back to the ring spinning machine.

Examples 1 and 2
A bobbin was ejected by the automatic winding machine as an outlier, be-
cause the evenness (CVm) was too high. In the laboratory the high even-
ness could be confirmed. Since the bobbin was identified with the spinning
position at which the yarn was produced, the repair crew found that the top
roller of the respective drawbox was contaminated with honeydew (Fig. 13).

Fig. 13 Honeydew on front roller Fig. 14 Defective apron

Another outlier bobbin was ejected at the winding machine because the
number of S-faults was too high. A check at the spinning machine could
clarify that a defective apron with a hole has caused this alarm at the yarn
clearer (Fig. 14).

Examples 3 and 4
Another outlier bobbin was ejected because of a high number of S-faults.
After having confirmed this in the laboratoary as well, the check at the re-
spective spindle at the ring spinning machine has shown that the apron of
the drawbox moved in the wrong direction, and, therefore, the joint was
defective (Fig. 15).

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Fig. 15 Wrong direction of apron, bad joint Fig. 16 Intensive contamination at output of drawbox

A bobbin was identified as outlier by the yarn clearer because the number
of imperfections was too high. The check at the ring spinning machine has
shown an accumulation of fiber fragments at the locations indicated by yel-
low arrows in Fig. 16.

3.8 Recommendations for a sampling plan

There are some limitations on the winding machine to reach the same ac-
curacy as spinners reach in the laboratory. The reasons for these limita-
tions are:
 Long maintenance cycles for clearers
 Contamination of the measuring zones of on-line systems as a result of
a permanent monitoring, 24 hours a day, 7 days per week
 The yarn speed is not constant on a winding machine. Therefore, peri-
odic mass variations cannot be measured directly on the winding ma-
chine. Periodic events have to be measured by indirect measurements
such as the higher evenness or the frequent occurrence of thick and
thin places. However, in the laboratory the operator can measure the
yarns at constant speed and, consequently, an accurate spectrogram
can be determined. With this precise information of specific periodicities
the textile laboratory can elaborate a detailed action plan.
 The microclimate on the winding machine near the yarn clearer is given
by various variables such as the environmental conditions in the wind-
ing room, the heat produced by the winder, etc. In the laboratory the
environmental conditions are defined by international standards.

As a result of this it is strongly recommended to check the bobbins in the

laboratory which are ejected at the winding machine due to quality prob-
lems.

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Table 2 is a recommended test procedure for a textile laboratory in a mill

with 27’000 spindles, cotton 100%, count range Ne 40 to Ne 80.

Machine No. of ma- Quality Test intervals Test Test Required test
chines or characteristics speed length time per day *
positions
Evenness
Diagram
Card 12 2 per day 100 m/min 250 m 8 min
Spectrogram
Variance-length curve
Evenness
First draw- Diagram
2 2 per day 100 m/min 250 m 8 min
frame Spectrogram
Variance-length curve
Evenness
Diagram
Comber 12 2 per day 50 m/min 250 m 16 min
Spectrogram
Variance-length curve
Evenness
Finisher draw- Diagram
4 4 per day 50 m/min 250 m 32 min
frame Spectrogram
Variance-length curve
Evenness
Diagram 5 roving bob-
Roving frame 600 100 m/min 250 m 16 min
Spectrogram bins per day
Variance-length curve
Evenness
Diagram 10 bobbins per
Spectrogram machine every
Imperfections third day
Ring frame 27’000 800 m/min 1000 m 169 min
Hairiness
Yarn diameter (90 bobbins
Density daily)
Trash
Evenness 60 ejected
Diagram bobbins from
800 m/min 1000 m 113 min
Spectrogram winding ma-
Imperfections chine daily
Winder 600
Hairiness
Yarn diameter 20 cones per
Density 800 m/min 1000 m 39 min
day
Trash
Total 401 min

Table 2 Total test time required in the laboratory per day for this example

* Time required also includes setting of instrument and sample preparation

The total test time per day is equivalent to 401 minutes or 6 hours and 41
minutes. This indicates that the tests can be managed in one shift.

The total test time is based on an average work load in the laboratory.
However, the slivers of the cards, drawframe, combers, etc., can also be
measured at the same day.

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As a measure for corrections at machines with non-identified bobbins we

recommend to study the action plan once per day, to check the analysis of
the outlier bobbins, to walk along each machine and to check the spinning
positions.

4 Role of the laboratory in a modern spinning mill

4.1 Tasks of a modern laboratory

The textile laboratory in a modern spinning mill has to fulfill four tasks
(Fig. 17):
 Systematic or random sample testing of the current production for sta-
tistical reasons.
- Elaboration of a statistical platform for raw material, slivers, rovings
and yarns. For yarns the mill statistics can be based on machines or
articles Comparison with international benchmarks (green arrows,
Fig. 17). The production statistics are based on bobbins.
- Set up of new machines. Check of slivers, rovings or yarns and
comparison with known benchmarks or agreements.
- Changing of articles. Comparing quality characteristics with internal
statistics, if already available. Modification of machine settings if
quality characteristics are not within given limits, agreed with cus-
tomer yarn quality profile.
 Production of yarn quality profiles for customers (blue arrows, Fig. 17).
These quality profiles are frequently based on cones.
 Analysis of bobbins which were separated by the yarn clearer as outli-
ers (red arrows, Fig. 17). Listing of an action plan based on outlier bob-
bins as an instruction for the maintenance and repair crew.
 Development of new yarns (orange arrows, Fig. 17).

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Sample testing New yarn developments

... ...
Raw Slivers Rovings Yarns
material

Elimination of the
sources of outlier
bobbins
Testing of outliers
Machine Spinning Detection Ex pecte d Sourc e found A ction Time Signatu re Date
p ositio n in so urce b y repair cre w taken for
labor atory repa ir
14 231 Peak in Da mage C ontaminatio n C leane d 10 min June 25,
RSM spectrogram on front o f fron t roller f ront ro ller 2007

Outlier bobbins
...
at 8 cm rol ler, rin g d ue to
sp inning h oneydew
14 284 High Ri ng R ing tr avelle r R eplac ed 5 min June 25,
RSM period ic tra veller w orn o ut ring 2007
separated by the
3
Finish er
drawfra me
hairin ess
Periodicity at
28 m
Co nta-
mination of
dra wbox of
fin isher
Same
t ravelle r
C leane d
d rawbo x of
f inishe r
d rawfra me
10 min June 25,
2007 Laboratory yarn clearer
dra wframe

Action plan for maintenance

and repair crew

...
Comparison with
benchmarks
Testing of final product
Statistical platform for Yarn quality profile
spinning machines or articles for customers
Hairiness

4.65

4.55

4.45

4.35

4.25

4.15
0 3 6 9 12 15 18 21 24 27 30 33 Weeks

Fig. 17 Tasks in a modern laboratory

4.2 Sample testing

The sample testing in the laboratory includes the measurement of raw ma-
terial in all stages of the spinning process. This includes also the measure-
ment of sliver and rovings.

The systematic or random sample testing of the current production serves

for an establishment of a sound statistical platform for the mill.

Raw material testing:

The bale lay-down is carried out with the USTER® HVI System whereas the
process control is executed with the USTER® AFIS System. Process con-
trol means the monitoring of the raw material from the bale to roving.

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It concerns the change of the fiber length, the short fiber content, the for-
mation and elimination of neps, the reduction of dust and trash particles,
etc., along the spinning process.

Evenness testing of slivers:

This test is used as a standard test to detect changes of the performance of
cards and drawframes.

Evenness testing of rovings:

This test is used as a standard test as well to detect changes of the perfor-
mance of the roving frame.

Testing of yarns:
Depending on the requirements the sample testing can be based on the
yarns produced in the mill, i.e. for every batch which is produced for specif-
ic customers the mill has to define the quality characteristics for the mill
statistics.

The samples are taken randomly from the machines where the yarn batch
is produced. The size of the sample depends on the accuracy of the statis-
tics which has to be established (see also Table 3).

Example: A spinning mill produces a combed cotton yarn for a specific cus-
tomer, Ne 40, on 6 machines, 1008 spindles each, for 10 days. At these 6
machines 10 bobbins are taken randomly every third day during the day
shift and measured in the laboratory. This production lot is equivalent to
approximately 23 metric tons of yarn. The sample size after 10 days was
180 bobbins in total, which is sufficient for as a statistical basis for this lot.

A second option is a systematic check of all the machines to compare the

result with benchmarks which already exist in the mill or with the USTER®
STATISTICS.

For both mentioned options the mill uses the results for long-term statistics
for various quality characteristics such as the fiber parameters, the even-
ness, the imperfections, the periodic faults, the strength, the elongation, the
remaining disturbing thick and thin places and foreign fibers, etc. (see also
Table 3).

Installation of new machines or maintenance:

After the installation of new machines or after the maintenance of machines
the slivers, rovings and yarns have to be tested in the laboratory to be sure
that the machines have the expected performance.

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4.3 Elaboration of yarn quality profiles for customers

In a modern industrial environment the supplier determines the quality level

of his products. This is a basic quality concept which is also supported by
industrial standards such as ISO 9000. Consequently, if the yarn buyer
asks for the quality characteristics of the yarn batch, the supplier will deliver
these figures.
The figures are mostly based on the values of the cones because the
cones are the final product of the spinning mill. If the yarn buyer is not satis-
fied with the quality of the yarn, the claims have to be based on the quality
characteristics of the cones because the bobbins are not available any-
more.
The yarn producer and the yarn buyer together have to define the yarn
quality profile together. An example of yarn quality profile is shown in Table
3.

4.4 Development of new yarns

In most of the spinning mills it is not possible anymore to produce the same
yarn counts with the same raw material for decades due to the high cost
pressure for commodities. Therefore, mills have to be creative and have to
penetrate into new areas such as slub yarns, microfiber yarns, mélange
yarns, etc. The start-up of such developments consumes a considerable
amount of the time in the laboratory.

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An example of a yarn quality profile is shown in Table 3.

Nominal Yarn Count (Nec) 28 32 36 40 USTER®

Fiber Quality STATISTICS
AFIS: Number of neps, bale (1/g) max 250 240 230 220 50%
HVI: Micronaire, bale Range 3.8 – 4.5 3.8 – 4.5 3.8 – 4.5 3.8 – 4.5
HVI: Fiber Length UHML (mm) min 28 28 28 28 50%
AFIS: Fiber Length UQL(w), bale (mm) min 30 30 30 30 50%
AFIS: Short Fiber Content SFC(n), finisher drawframe (%) max 13 12 11 10 50%
Yarn Count and Twist
Deviation of Count (%) max ± 2.5 ± 2.5 ± 2.5 ± 2.5
Count Variation CVb (%) max 1.5 1.5 1.5 1.5
Twist Multiplier alpha e max 3.6 3.6 3.6 3.6
Variation of Twist CVt (%) max 3 3 3 3
Direction of Twist Z Z Z Z
Yarn Evenness and Hairiness
USTER® Evenness CV (%) max 11.8 12.5 12.7 12.9 20%
Thin Places - 40% (1/km) max 37 60 91 113 20%
Thin Places - 50% (1/km) max 1 2 2 2 20%
Thick Places + 35% (1/km) max 182 240 300 340 20%
Thick Places + 50% (1/km) max 16 19 23 25 20%
Neps +140% (1/km) max 153 200 245 272 20%
Neps + 200% (1/km) max 35 45 57 63 20%
USTER® Hairiness max 4.8 4.6 4.4 4.3 50%
Yarn Strength and Elongation
Single End Strength (cN/tex) conventional min 15 15 15 15 95%
Strength Variation CVb (%) conventional max 8.3 8.6 8.8 8.9 75%
Single End Elongation (%) conventional min 5.2 5 4.9 4.8 75%
Single End Strength (cN/tex) high speed min 16.5 16.5 16.5 16.5 95%
Strength Variation CVb (%) high speed max 8.6 8.9 9.1 9.3 75%
Single End Elongation (%) high speed min 4.7 4.6 4.5 4.4 75%
Significant CLASSIMAT Faults, remaining
A3+B3+C2+D2, cumulative (1/100 km) max 14 14 14 14 50%
E (1/100 km) max 0 0 0 0 50%
H2 + I2 (1/100 km) max 0 0 0 0 50%
Foreign fibers A3 + B2 + C1 + D1 + E1, cumulative (1/100 km) max 0 0 0 0 50%

Table 3 Yarn quality profile

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4.5 Analysis of outliers

A permanent headache in a spinning mill is the production of outlier bob-

bins. An outlier bobbin is a bobbin where one or more quality characteris-
tics exceed preselected thresholds.

The thresholds are set on a level where faults may be recognized in woven
or knitted fabrics, particularly after bleaching or dyeing.

A modern yarn clearer such as the USTER® QUANTUM clearer can sepa-
rate the outlier bobbins.

The clearer, however, does not analyze the bobbins in detail. On the dis-
play of the winding machine the type of alarm is indicated, but no analysis
is made about the source of the fault. For this purpose there are better tools
available in the laboratory.

This can be underlined with 2 examples:

 A periodic mass variation due to a front roller defect on one position of
the ring spinning machine will increase the coefficient of variation of
evenness CVm of the yarn. It may also trigger the “pearl chain channel”
which indicates that there are numerous faults in the same fault length
and mass increase area. However, since the yarn speed on the winding
machine is not constant, the clearer cannot analyze that there is a spe-
cific periodicity with a wavelength of 8 cm by means of a spectrogram.
Therefore, an analysis has to be made in the laboratory.
 A bobbin was rejected on the winding machine because the hairiness
has exceeded the predetermined threshold. The diagram of the labora-
tory system has shown that a defective ring traveller of this particular
ring spinning position has caused this fault.

5 Conclusion
Most of the spinning mills have an established quality management system
based on sample testing. With such a quality system, however, it may take
one year or more to get rid of outliers.

This paper describes a method with which outlier bobbins can permanently
be separated on the winding machine with the help of yarn clearers and
traced back to the faulty spinning position.

The method which is described in this paper also allows the daily elimina-
tion of outlier bobbins.

The described system is used by various mills with considerable success.

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Uster Technologies AG
Sonnenbergstrasse 10
CH-8610 Uster / Switzerland

Phone +41 43 366 36 36

Fax +41 43 366 36 37

www.uster.com
textile.technology@uster.com

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