136USTER®_TESTER_4_-_Determination_of_the_trash_and_dust_content_in_yarns

8/11/2019 136USTER_TESTER_4_-_Determination_of_the_trash_and_dust_content_in_yarns

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Wolfram Sll / Gabriela PetersSeptember 1999SE 556

Application Report

Determination of the trash and dustcontent in yarns with the USTER

TESTER 4-SX


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USTERTESTER 4-SX 2 (15)

Contents

1 Introduction ................................................................................ 3

2 Measuring princ iple of the optoelectronic OI sensor ............ 3

2.1 Technical measurement characteristics....................................... 4

2.2 Evaluation possibilities ................................................................. 5

3 Definit ion of optoelectronically determined qualityparameters .................................................................................. 5

4 Information gain through measurement of trash and

dust part icles .............................................................................. 6

4.1 Determination of trash and dust in raw cotton and inintermediate products................................................................... 6

4.2 Determination of trash and dust in yarn ....................................... 7

4.3 Influence of trash and dust on subsequent production

processes..................................................................................... 8

4.4 Effect of trash and dust on the wear of machine parts................. 9

5 Examples of dif ferent contaminants in yarn.......................... 10

6 Initial findings from pract ical applications ............................ 11

6.1 Comparison of trash and dust measurements of yarns with

different noil percentages........................................................... 11

6.2 Comparison of rotor yarns with different clearingefficiencies of the OE spin boxes ............................................... 12

6.3 Influence of the winding speed on the trash and dust

content of carded ring yarns....................................................... 13

7 Summary and outlook ............................................................. 15

Copyright 2005 by Uster Technologies

All rights reserved. No part of this publication may be reproduced, stored in a re-

trieval system, translated or transmitted in any form of by any means, electroni-

cally, mechanically, photocopying, recording or otherwise, without the prior permis-

sion in writing of the copyright owner.

veronesi\TT\Schulung_Dokumente\Off-line\Uster Tester 4\Sales Literatur\ englisch\PUBL_UT4SX_OI-e.doc


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1 Introduction

With the application of chemicals in todays cotton harvesting methods, it is

possible to defoliate the cotton plants and open the bolls which are stillclosed at the same time. However, the use of such chemicals also means

that the harvest is limited to a short period and therefore requires a preciseplanning and scheduling of the harvesting process. This explains why fully

automatic harvesting machines are often used today. These machinespermit a time-saving harvest of the cotton plants and a simultaneous re-moval (spindle picking) of stalks and remaining pieces of leaves. Another

automatic harvesting method (stripper) produces a yield of only 1/3 of cot-

ton compared with 2/3 of stalks, pieces of leaves and sand, which subse-quently have to be removed in a very aggressive ginning process. It is a

proven fact that the time-consuming manual harvest of cotton, which is stillused with high-quality, long-staple cotton, actually stands out through a

lower contamination of the raw cotton. This means that less aggressiveclearer settings are needed in the subsequent ginning process, because

the hand-picking is aimed specifically at harvesting only cotton bolls, sothere is no need for cleaning out pieces of leaves and stalk. With all har-

vesting methods, however, the cotton seed, together with the fibers, alwaysgets into the ginning plant where it is broken up into trash and seed-coat

fragments. This means that ginned cotton is always contaminated withtrash and dust particles and that an intensive cleaning is only possible in

the spinning mill.

The introduction of the USTERAFISmade a reproducible determination of

the trash and dust particles of raw cotton and of intermediate products atthe various production stages possible for the first time. It has been shownin many publications that knowing the trash and dust content in the spin-

ning process provides a great variety of information with regard to the ma-chine settings, the wear of machine parts and the quality of the finished

fabric. Until now, a reproducible, automatic determination of the trash anddust particles in yarns has not been commercially available on the textile

market. With the USTER TESTER 4-SX, Uster Technologies now offerstwo new optoelectronic sensors. The OI (Optical - Impurities) sensor de-

tects trash and dust particles in yarns and determines their number andsize. The OM (Optical - Multifunctional) sensor, on the other hand, deter-

mines the yarn diameter, the fine structure and the roundness of yarnsamong other parameters.

2 Measuring princip le of the optoelectronicOI sensor

The measuring principle of the OI sensor is based on the image of the yarnbody surface on a linear array opto-ASIC. The yarn passes through a

hemispherical, white testing space. This space is illuminated by blue light-emitting diodes mounted on the hemisphere. Blue light is most suitable for

the detection of trash particles, because it produces a strong contrast be-tween the trash particles and the yarn.


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Opto-ASIC

Light-emitting diodes

Lens

White hemisphere

Measuring slo t

Fig. 1

Measuring principle of the

OI sensor

2.1 Technical measurement characterist ics

In the first place, the measuring method determines the number of trash

and dust particles on the yarn surface. The OI sensor is not designed forthe detection of foreign fibers and of hidden, spun-in black hair in the areaof worsted yarn spinning. At this point, however, it should be considered

that foreign fibers are seldom-occurring events and are not detected in rou-tine laboratory testing on the USTERTESTER 4-SX.

The measuring method determines the mean area of the trash and dustparticles. From that, the USTERTESTER 4-SXcalculates the mean parti-cle size in micrometers. The system detects particle sizes from 100 to 1750

m. Like other USTERinstruments, the USTERTESTER 4-SXis basedon the definition of trash and dust particles of the International Textile

Manufacturers Federation (ITMF). Fig. 2below shows a dimensional com-

parison of the minimum and maximum sizes of the trash and dust particlesto be detected in relation to the yarn diameter of a cotton yarn with a countof 20 tex (Ne 30, Nm 50) as well as the limiting size of trash and dust.

Yarn 20tex (Ne 30,Nm 50)

Max. size: 1750 m Min. size: 100 m

Trash > 500 m Dust 500 m

500 m

Fig. 2

Dimensional comparison oftrash/dust and yarn


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The USTERTESTER 4-SXpermits a fully automatic testing of the quality

parameters up to a testing speed of 400 m/min. In addition, the OI sensor

provides reproducible measurement values independent of the testing

speed.

2.2 Evaluation possibi lit ies

With the yarn measurement, the new OI sensor provides the following addi-

tional quality data:

Determination of the number of trash particles per kilometer (1000 me-

ters) and gram

Determination of the mean trash size in m

Determination of the number of dust particles per kilometer (1000 me-ters) and gram

Determination of the mean dust size in m

Display of the number and size of trash and dust particles in a histo-gram

The number of trash and dust particles, like the number of imperfections

(thin, thick places and neps), has traditionally been defined per kilometer(1000 meters). The unit per gram has been included to allow an immedi-

ate comparison of the trash and dust particle results with those of theUSTERAFIS.

3 Definition of optoelectronically determinedquality parameters

Table 1provides an overview of the quality parameters measured with the

OI sensor:

Designation Unit Definit ion

Trash count 1/km Number of trash particles per kilometer of yarn

Trash count spec. 1/g Number of trash particles (>500 m) per gram

Mean trash size m Mean size of all detected trash particles

Dust count 1/km Number of dust particles per kilometer of yarn

Dust count spec. 1/g Number of dust particles (


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4 Information gain through measurement of trashand dust particles

4.1 Determination of trash and dust in raw cotton and inintermediate products

With the various, presently available testing methods, the determination oftrash and dust particles is still limited to fiber testing. Especially cottonspinning mills, but also many classing offices and laboratories of the textile

machine industry, use HVI installations (High Volume Instrument) for the

determination and classification of the trash content. This testing systemalso uses different sensors to measure other important quality parameters

such as micronaire, color, tensile properties (force, elongation) and fiberlength distribution.

A very important quality aspect, besides the information about the contami-

nation of the raw cotton, is the knowledge of the variation of the contamina-tion level in the entire spinning process. Fig. 3shows the variation of the

trash content in the preparation process of a combed ring yarn. The dia-gram clearly shows that, in absolute terms, most of the trash is removed atthe card but it also shows that the combing process, depending on the noil

percentage, has a considerable influence of the cleanliness of the mate-

rial.1

0

50

100

150

200

250

300

350

Raw cotton Card mat Card sliver Comber lap Roving

0

200

400

600

800

1000

1200

1400

1600

Neps / gTrash and

Dust / g

Neps / g

Trash and

Dust / g

Fig. 3

Process analysis in the

spinning process

With the USTERAFIS, the user is now in a position to carry out a processcontrol with regard to the variation of fiber parameters such as the fiber

length and the nep and trash content. The monitoring of these quality pa-rameters permits a specific control of the different production machines with

regard to the correct clearing and draft settings, the wear of parts and the

clearing efficiency of the individual process stages.

1M.Frey, U.Schneider: Possibilities of removing seed fragments with adherent fibers in the spinning mil l, Melliand Textile Reports 5/89


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An increase of the nep content after the carding process without a change

of the raw material or the machine settings, for example, can be an indica-

tion of a worn card clothing which requires a regrinding or even a replace-

ment of the card clothing. With such process control possibilities, it is quiteobvious that an optimization of the maintenance intervals can prevent apossible production of substandard quality and, in the end, represents anefficient possibility of saving costs (Fig. 4).

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Neps/g limit value

after grinding

week

Neps per gram [AFIS]

Fig. 4

Process control at the card2

4.2 Determination of trash and dust in yarn

So what is the added benefit we can expect from determining the trash anddust particles in yarn? With the introduction of the optoelectronic OI sensor

for the measurement of contaminants with the USTERTESTER 4-SX, it ispossible for the first time to obtain information with routine laboratory testsabout the trash and dust content in yarns together with the other quality

parameters. With the existing capacitive sensor, it was not possible to dis-

tinguish between neps and trash particles. The OI sensor, on the otherhand, identifies trash and dust as separate objects. Seed-coat fragments

are also counted as trash or dust depending on the size.

An important advantage of the determination of the trash and dust particles

at the very end of the spinning process is the objective assessment of the

clearing efficiency with regard to vegetable remains in yarn. In practice, thismeans that the cotton is purchased according to the usual criteria, i.e. the

cotton is assessed and selected according to quality standards of the class-ing office. At the same time, this quality assessment is the most importantfactor for the pricing of raw cotton.

2USTER NEWS BULLETIN No. 38, page 20, M. Frey, R. Furter, R. Meier, W. Schneiter, Ed. White, Uster Technologies


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After the raw material has been defined, the clearer settings in the spinning

preparation and the machine settings in the spinning mill are specified ac-

cordingly. Once they have been defined, the settings are usually left un-

changed. With a certain statistical variation, a constant quality will set inwith regard to the trash and dust content in the yarn provided no changeshave been made in the production process or the respective raw material. Ifthese requirements are fulfilled and the trash and dust content in yarn in-

creases, then this would indicate a fault in the production process and re-

quire an examination of the entire spinning process with the help of suitablefiber testing instruments, but especially with the USTERAFIS(Fig. 5). The

main advantage of controlling the trash and dust content in the yarn is theimmense time saving, because a quality control of the yarn at the end ofthe process is standard procedure in modern spinning mills. In addition, the

USTERTESTER 4-SXpermits an automatic monitoring of the measure-

ment values with defined warning and control limits and therefore ensures a

continuous monitoring of the test data.

1

10

100

1000

10000

0 2 4 6 8 10 12 14 16 18 20 22 24

Trash count Dust count

Limit value Limit value

Days

Trash / Dust per k m [UT4 OI]

Trash

Dust

Process control by m eans of fib er

testing equipment has to

Fig. 5

Increase of the trash and

dust content in yarn

4.3 Influence of trash and dust on subsequent product ionprocesses

A high trash content in yarn will also have an effect on the subsequent pro-duction processes. The information on the trash content in a yarn, for ex-

ample, is very helpful for a possible subsequent scouring process. At thisfinishing stage, vegetable contaminants are removed from yarns or from

fabrics with the help of sodium hydroxide (NaOH) and supporting chemicalsat a temperature of 98C. If the degree of contamination is known, it is pos-

sible to control this process by adjusting the concentration and duration

accordingly.


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Extensive tests with the USTERTENSOJEThave also shown that trash

particles and seed-coat fragments in yarn can cause dangerous weak

places. Fig. 6shows the different reasons for the 69 weak places detected

in a rotor yarn of 100% cotton (20 tex, Nm50, Ne30), which have been de-termined in a test series of two million breaks. The weak places have amean specific tensile strength of 7.4 cN/tex (min. 2.8 cN/tex, max. 9 cN/tex)and a mean elongation of 3.7% (min. 1.89 %; max. 6%). Because of the

special yarn construction of OE rotor yarns, with the twist being applied

from the inside to the outside, there is a danger that trash particles disturbthe twist application and, as a result, causing weak places.

Reasons for isolated weak places of OE rotor-spun

100% combed cotton, 20tex (Nm 50,Ne 30)

Seed-coat fragments

7% Trash

16%

Thick places

9%

Thin places

57%

Neps

1%

Foreign fibers

6%

Spinning starter

4%

Fig. 6

Reasons for weak places3

4.4 Effect of trash and dust on the wear of machine parts

The following section raises some issues which cannot yet be backed upwith examples, because this would require a continuous observation over

very long periods. However, they serve as a basis for discussion and show

possible application areas which can be opened up by a trash and dustmeasurement of yarn.

It should be possible to show, for example, that there is a connection be-tween the dust content and the wear of machine parts at friction and deflec-

tion points of the subsequent production process. This would apply in par-

ticular to the needle wear on knitting machines and the wear of yarn guideelements at deflection points in the weaving or warping areas. An increased

dust content will certainly result in accelerated wear of the production partsin the spinning process.

3A.Weber: Analysis of weak places with capacitive and optical sensors on the USTER TENSOJET, dissertation SS95, Fachhochschule fr

Technik und Wirtschaft, Reutlingen


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A high dust content also has an effect on the service life of the delivery

nozzle in the spin box of the OE rotor spinning machine, the ring traveler at

the ring spinning machine and the yarn guide elements in the winding area.

5 Examples of different contaminants in yarn

The following pictures show different examples of seed-coat fragments

(Fig. 7) and trash particles (Fig. 8) which, among other contaminants, canbe detected with the OI sensor of the USTERTESTER 4-SX. Seed-coatfragments are always accompanied by dozens or even hundreds of fibers,

while trash particles are not attached to fibers.

Fig. 7Seed-coat fragments

Fig. 8

Trash particles


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6 Initial findings from practical applications

6.1 Comparison of trash and dust measurements of yarns

with different noil percentages

Table 2shows a comparison of two ring yarns which were spun with differ-ent noil percentages. For the calculation of the percentage decrease of

imperfections, trash and dust particles, the yarn with the lower noil percent-age was taken as 100%.

Combing efficiency

Thin

-40%

/km

Thin

-50%

/km

Thick

+35%

/km

Thick

+50%

/km

Neps

+140%

/km

Neps

+200%

/km

Neps

+280%

/km

Trash

>0.5 mm

/km

Dust


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Fig. 10

Distribution of trash and

dust with a noil percentage

of 20%

The two diagrams show clearly how the overall level of trash and dust couldin fact be lowered considerably by increasing the noil percentage. The de-termination of an optimum noil percentage shall not be dealt with at this

point.

6.2 Comparison of rotor yarns with different clearing effi-ciencies of the OE spin boxes

The following example compares four drawframe slivers and the respectiveyarns spun by two spinning mills which produce similar yarn counts. In Fig.

11, the trash content of the slivers is compared with the trash content of the

yarns. The comparison of the drawframe slivers 1 and 3 of the two spinningmills shows a higher trash content for A, whereas the differences in thesecond sliver quality are quite small. In each case, the clearing efficiency of

the OE spin box of the spinning mill A with regard to the trash removal isbetter than that of the spinning mill B.

Comparison of finisherdrawframe sliver and

0

2

4

6

8

10

12

14

16

18Spinning mill A Spinning mill B

Fig. 11

Trash content in sliver andyarn


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The comparison also shows a noticeable difference in the dust content of

the two drawframe slivers. With an optimum clearer setting of the spin

boxes of spinning mill A, it was possible to achieve a dust reduction of 81%

in the yarn 105 tex (Ne 5.6; Nm 9.5) and 87% in the yarn with 87 tex (Ne6.75; Nm 11.5). The spinning mill B, on the other hand, produces a draw-frame sliver with about half the dust content compared with spinning mill A.In the subsequent spinning process, however, the high quality of this draw-

frame sliver with regard to a reduced dust content can only be utilized to a

limited extent. As shown very clearly in Fig. 12, the dust content of yarn B is50 to 78% higher than that of yarn A. This example illustrates how the de-

gree of contamination of yarns can vary according to the clearing efficiencyof the OE spin box.

Comparison of fini sher drawframe sliver to yarn

0

20

40

60

80

100

120

Spinning mill A Spinning mill B

Fig. 12

Dust content in sliver and

yarn

6.3 Influence of the winding speed on the trash and dustcontent of carded ring yarns

An additional trial series was carried out to examine the influence of thewinding speed on the trash and dust content of carded yarns, which werewound at different speeds and then tested with the UT4. The results are

shown in the following diagrams. With regard to the trash content (Fig.13)

of ring yarns, one would assume that a reduction in the trash content couldbe expected, on the one hand, through the spinning process and, on the

other hand, through the subsequent winding process. In the case of a wind-ing speed of 1200 m/min, the two yarns show a trash reduction of 50%. Inabsolute terms, however, the trash reduction of yarn B is much higher than

that of yarn A. The reason for this is the different structure of the trash par-

ticles such as seed-coat fragments and pure trash particles with no fibers

attached.


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A comparison of these structures leads to the conclusion that loose trash

particles are more likely to be thrown out in the winding process than seed-

coat fragments, which are more strongly tied into the yarn body by the at-

tached fibers.

Influence of the winding speed

Trash/km

0

10

20

30

40

50

60

0 m/min 800 m/min 1000 m/min 1200 m/min 1400 m/min 1600 m/min

Yarn A Ne 30

Yarn B Ne 30

Bobbin

Fig. 13

Influence of the winding

speed on the trash content

Fig. 14shows the reduction in the number of dust particles resulting from

the winding process. A comparison of the dust content of the bobbins,again at the winding speed of 1200 m/min, results in a calculated reduction

of about 30%.

Influence of winding speed

Dust/km

0

300

600

900

1200

1500

1800

0 m/min 800 m/min 1000 m/min 1200 m/min 1400 m/min 1600 m/min

Yarn A Ne 30

Yarn B Ne 30

Bobbin

Fig. 14

Influence of the winding

speed on the dust content


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USTER TESTER 4 SX 15 (15)

Up to a winding speed of 1200 m/min, there are no differences with regard

to the yarn evenness, the imperfections and the tensile properties. A loss of

quality in the yarn evenness, imperfections and tensile properties can be

observed only at winding speeds of 1400 m/min and up. The yarn hairinessincreases with every winding process.

7 Summary and outlook

With the installation of the OI (Optical - Impurities) sensor in the USTER

TESTER 4-SX, Uster Technologies has completed the quality assessment

of a yarn. In addition to the known quality parameters such as evenness,imperfections, hairiness and yarn count and the new parameters such as

yarn diameter and its variation as well as the yarn roundness, the fourth

generation of the USTER TESTER is now capable of determining addi-tional important parameters of the yarn quality. All quality parameters canbe determined simultaneously at testing speeds of up to 400 m/min on the

same piece of yarn. The activation of all five sensors results in an enor-mous saving of time and work for the spinning mill. The initial trials have

shown that there are a number of possible applications for the OI sensor. It

could be shown, for example, that the spin boxes of an OE rotor machinecan have a considerable influence on the clearing of trash and dust. In ad-dition, and against all expectations, it turned out that, with regard to trash

and dust, the winding process has cleaning effect on the yarn, because ahigh winding speed results in a reduction of the trash and dust content.

Unfortunately, it is not possible to select just any high winding speed be-cause of the other quality parameters involved. It is to be expected thatadditional advantages and application areas will be discovered in the fu-ture. Finally, it should be added that the OI sensor, in line with Fiber to

Fabric engineering, is an important step into the new millennium.

Uster Technologies AG

CH-8610 Uster / Switzerland

Telephone +41 43 366 36 36

Telefax +41 43 366 36 37

[email protected]

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136USTER®_TESTER_4_-_Determination_of_the_trash_and_dust_content_in_yarns