quality management in the textile laboratory

Gabriela Peters November 2003 / Edition 2: November 2007 SE 577

USTER®

LABORATORY SYSTEMS APPLICATION REPORT Quality management in the textile laboratory

THE STANDARD FROM FIBER TO FABRIC


Copyright 2007 by Uster Technologies AG All rights reserved. No part of this publication may be reproduced, stored in a re-trieval system, translated or transmitted in any form or 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\Laborsysteme\SE_577_Quality management in the textile laboratory

2 (16) USTER® PRODUCTS


Contents

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

2 Size of the spinning mill and number of production machines5

3 Sample testing............................................................................ 6

4 Test conditions and sample size .............................................. 7

5 Combination of on-line and off-line tests ................................ 8

6 Test frequency, individual processes ...................................... 9

7 Influence of the relative humidity in the test room ............... 13

8 Summary................................................................................... 15

USTER® PRODUCTS 3 (16)


1 Introduction Quality management in the textile laboratory is of central importance to the spinning mill because production faults can be identified and eliminated with the test results. A question is often asked these days as to how often a machine has to be monitored and which machines must be monitored most carefully. It can be said with 100% certainty that a fault in the spinning preparation is considerably more serious than a defective cylinder on an individual ring spinning position. The crucial machine in a spinning mill with regard to fiber and yarn neps is the card, the saying ”the card is the heart of a spinning mill” is not said without reason. The raw material selection plays an equally important role but this report covers only the spinning process in order to find production faults. 2 Size of the spinning mill and number of produc-

tion machines A ring spinning mill with 30,000 spindles was the basis for the calculation of the test frequency in a laboratory. This spinning mill produces combed cot-ton yarns. The following machines are needed for the plant:

2

12

2 2

11

5

600

30000

600

1

10

100

1000

10000

100000

1 2 3 4 5 6 7 8 9

Number of processes

1 Blow room2 Card3 Drawing frame4 Comber lap5 Comber6 Drawing frame7 Roving frame8 Ring frame9 Winder

Fig. 1 Process steps and number of machines in a spinning mill

The number of corresponding machines from the blowroom to the final drawframe is mentioned in Fig. 1. The spindles and winding position are mentioned for the flyer, the ring spinning and winding machine.



3 Sample testing A lot could be written or cited about tests but tests should actually be sim-ple and practical. A systematic sample testing of each machines has as-serted itself in most spinning mills. There is the assumption that each proc-ess step in the spinning mill will be monitored during a certain period of time. This is not difficult for the process from the card to the finisher draw-frame because the cards should always be checked once a week. The test period of a roving frame and a ring spinning machine takes con-siderably longer because each individual spindle has to be checked once over a certain period of time. In our example there are 600 spindles on the roving frame which is equivalent to five to six machines depending on the type of spindles. If ten or eight spindles of a roving frame are removed and tested from the same roving frame every second day, it would take a whole month to test all the spindles on the flyer. It also needs to be considered that there are 30 ring spinning machines in our example. The laboratory staff would have to check 120 spindles daily if we assume a single shift and 250 working days per year. This would mean that ten bobbines have to be sampled every third day from the very same spinning machine. This calculation does not include the time needed for collecting the samples. A rotor spinning plant has ten rotor spinning machines on average which is equivalent to around 3,000 rotors, depending on the manufacturer. If ten cones are taken from each rotor spinning machine every day and checked, it would take about one and a half month to check the whole rotor spinning mill. The interval for checking rotor spinning machines is actually shorter than the one for ring spinning machines. However, considerably more yarn is produced on a rotor spinning position during a given interval which means that significantly more checks have to be made on each rotor spin-ning position. As the period of one year is extremely long between checks on ring spin-ning machines, most spinning mills have two shifts in order to shorten this test period. A defective spindle on a ring spinning machine results in con-siderably less subsequent defects than a defective machine in spinning preparation. Therefore, it has to be considered in the test frequency that the process from the card to the combing machine has to be checked far more intensively. This is normally no problem because there are considerably less production positions. The test frequency is described in chapter 6.



4 Test conditions and sample size The following table shows the test conditions and sample size for the individual quality characteristics. Quality characteristics

Name Unit Instrument Number of samples

Test within

Testing speed

[m/min]

Testing time [min]

Micronaire Mic USTER® HVI SPECTRUM 1 5 Upper Half UHML mm USTER® HVI SPECTRUM 1 5 Mean Length UI % USTER® HVI SPECTRUM 1 5 Bundle strength Strength g/tex USTER® HVI SPECTRUM 1 5 Color RD % USTER® HVI SPECTRUM 1 5 +b 1 5 Trash CNT USTER® HVI SPECTRUM 1 5 Area % 1 5 Neps Neps/g 1/g USTER® AFIS PRO 1 5 SCN/g 1/g 1 5

SFC(n) % USTER® AFIS PRO 1 5 SFC(w) % 1 5

Length

UQL(w) mm 1 5 Fine mtex USTER® AFIS PRO 1 5 IFC % 1 5

Maturity

Mat 1 5 Trash/g 1/g USTER® AFIS PRO 1 5 Trash Dust/g 1/g 1 5

VFM % 1 5 Count variation CVcb % USTER® TESTER 4 FA Module 10 1 Mass variation CVm % USTER® TESTER 4 10 1 400 1 CVmb % 10 1 400 1

H USTER® TESTER 4 10 1 400 1 sH 10 1 400 1

Hairiness

CVHb % 10 1 400 1 Thin places 1/1000 m USTER® TESTER 4 10 1 400 1 Thick places 1/1000 m 10 1 400 1

Imperfections

Neps 1/1000 m 10 1 400 1 Trash 1/1000 m USTER® TESTER 4 10 1 400 1 Trash and dust

Dust 1/1000 m 10 1 400 1 CVd % USTER® TESTER 4 10 1 400 1 Shape 10 1 400 1

Variation diameter

Dichte g/cm3 10 1 400 1 FH cN USTER® TENSORAPID 10 20 5 RH cN/tex 10 20 5 CVRH % 10 20 5 εH % 10 20 5 CVεH % 10 20 5 WH cNcm 10 20 5

Strength

CVWH % 10 20 5 FH cN USTER® TENSOJET 10 1000 400 RH cN/tex 10 1000 400 CVRH % 10 1000 400 εH % 10 1000 400 CVεH % 10 1000 400 WH cNcm 10 1000 400 CVWH % 10 1000 400 FP=0,1 cN 10 1000 400

HV strength

εP=0,1 % 10 1000 400

Table 1



5 Combination of on-line and off-line tests Due to the technical progress, it makes sense to choose a combination of on-line and off-line tests in today’s spinning mills because laboratory tests only are not sufficient for today’s high production quantities: the sample size is insufficient and, therefore, rare, disturbing faults are not detected, and as a consequence, not eliminated. However, there are three reasons why not all tests can be made on-line: a. The presentation of the fibers for example makes it extremely difficult

to test on-line in spinning preparation. The ring spinning machine with more than 1,000 spindles is not yet suitable for carrying out complete on-line tests.

b. It is only possible to test certain quality characteristics on-line such as

evenness. There are quality parameters, which cannot yet be tested on-line, such as all strength and elongation tests. Further, fiber neps in slivers and the short fiber content cannot yet be tested on-line.

c. The third and probably the most important reason is the climate. Tests

in a laboratory are generally made at a standard climate whilst the cli-mate on a testing position on a machine is not constant and does not correspond to the standard climate. Therefore, tests made in a labora-tory are unsurpassed with regard to their accuracy and reproducibility.

Thus, it is recommended to find a suitable combination of on-line and off-line tests. As already mentioned, it is highly advisable to start with an on-line measurement from the point of view of today’s high production quanti-ties. Therefore, the following examples are always based on on-line moni-toring. If there is no on-line monitoring on some machines, the sample size has to be increased for the laboratory tests in order to guarantee that an adequate quantity can be tested.



6 Test frequency, individual processes Combination of on-line and off-line quality management in the blowroom and on the card

Test method Quality Fiber Test Sample Equipmentcharacteristics presentation interval size

Laydown Fiber lengthFiber strengthMicronaireSCIColor GradeNepsShort fiber content

Blowroom Trash content Mat once per month 3 Tests Shirley-AnalyserTrash contentFiber neps

Card Sliver count RunningCV% 100 m productionSpectrogramSliver count Sliver once per week 5 x 10 m USTER® AUTOSORTEREvennessDiagramSpectrogramVariance-length curveNepsFiber lengthShort fiber contentTrash content

OFF-LINE

USTER® AFIS

USTER® HVI

Mat

Mat

per Laydown 5 Tests

per Laydown 5 Tests

OFF-LINE

ON-LINE

OFF-LINE

Mat

Sliver

Sliver

Sliver

once per month

continuous

once per week

once per week USTER® AFIS5 Tests

5 Tests USTER® AFIS

USTER® SLIVER EXPERT

min. 125 m USTER® TESTER

Table 2 Combination of on-line and off-line quality management in the combing process 1. Prozess : Sliver lap machine


Comber lap NepsFiber lengthShort fiber content

Draw frame Lap count 8 Laps once per week 1 x 1 m Lap balanceNepsFiber lengthShort fiber content

Comber Sliver count Sliver once per week 5 x 10 m USTER® AUTOSORTEREvennessDiagramSpectrogramVariance-length curveNepsFiber lengthShort fiber contentTrash content

once per week

once per week

per 3 months

USTER® AFIS5 Tests


5 Tests USTER® AFISOFF-LINE

OFF-LINE

Sliver

Sliver*

Lap

OFF-LINE USTER® AFISper 3 monthsLap 5 Tests

Table 3 Sliver* = The individual comber heads have to be tested if an increase of neps or short fibers of the comber sliver is noted.



Combination of on-line and off-line quality management in the combing process 1. Process: Drawframe


Drawing frame NepsFiber lengthShort fiber content

Comber lap Lap count 8 Laps once per week 1 x 1 m WickelwaageNepsFiber lengthShort fiber content

Comber Sliver count Sliver once per week 5 x 10 m USTER® AUTOSORTEREvennessDiagramSpectrogramVariance-length curveNepsFiber lengthShort fiber contentTrash content

OFF-LINE USTER® AFISonce per 3

monthsSliver 5 Tests

OFF-LINE

OFF-LINE

Sliver

Sliver*

Lap

once per week

once per week

once per 3 months

USTER® AFIS5 Tests


5 Tests USTER® AFIS

Table 4 Sliver* = The individual comber heads have to be tested if an increase of neps or short fibers of the comber sliver is noted. Combination of on-line and off-line quality management on the drawframe


Drawing frame Sliver count Running1. Passage Evenness production

SpectrogramSliver count Sliver once per week 5 x 10 m USTER® AUTOSORTEREvennessSpectrogramDiagramNepsFiber lengthShort fiber content

Drawing frame Sliver count Running2. Passage Evenness production

SpectrogramSliver count Sliver once per week 5 x 10 m USTER® AUTOSORTEREvennessSpectrogramDiagramNepsFiber lengthShort fiber content


Sliver once per week 125 m USTER® TESTER


ON-LINE

OFF-LINEUSTER® TESTERSliver once per week 125 m

Sliver

Sliver continuous

5 Tests

ON-LINE

OFF-LINE

Sliver

USTER® AFISonce per 3

months

Sliver continuous

once per month 5 Tests USTER® AFIS

Table 5 Remark: These figures are based on drawframes with autolevellers, perhaps double tests can be re-duced.



Combination of on-line and off-line quality management on the roving frame and on the ring spinning machine


Roving frame Roving count 8 Rovings Every 2. day 1 x 10 m each USTER® AUTOSORTEREvennessSpectrogramDiagramNepsFiber lengthShort fiber content

Ring frame Yarn breaks RunningEfficiency productionIdle spindlesYarn countCV Yarn countEvennessSpectrogramDiagramImperfectionsHairinessYarn diameterDensityTrash contentTenacity 20 Tests/Bobbin USTER® TENSORAPIDElongation 1000 Tests/Bobbin USTER® TENSOJETTwist 10 Bobbins once per week 10 Tests/Bobbin ZweigleClassimat Bobbins once per month 100 km USTER® CLASSIMAT

ON-LINE

OFF-LINE

USTER® AFISonce per month

10 Bobbins Every 3. day

10 Bobbins Every 3. day

OFF-LINEUSTER® TESTER8 Rovings Every 2. day 1 x 125 m each

8 Rovings

Bobbins Continuous

1 Test each

USTER® RING EXPERT

1 x 100 m each USTER® AUTOSORTER

10 Bobbins Every 3. day 1 x 400 m each USTER® TESTER

Table 6 Remark: In case of 30 ring spinning machines, ten bobbins should be removed from different spinning positions every third day.



Combination of on-line and off-line quality management on a winding machine


Winder Yarn faults N/S/L/TForeign fibersPearl chainEvenness RunningImperfections productionHairinessNumber of jointsClassification of yarn faultsClassification of jointEfficiency RunningProduction per kg productionStop timeAlarm timeYarn countCV Yarn countEvennessSpectrogramDiagramImperfectionsHairinessYarn diameterDensityTrash contentTenacity USTER® TENSORAPIDElongation USTER® TENSOJETFriction 10 Packages Per lot 1 test each SchlafhorstMoisture content 10 Packages Per lot 1 test each Mahlo

ON-LINE

OFF-LINE

10 Packages Per lot

Yarn

Yarn

Continuous

20 Tests/Packages

20 Packages Per lot

Continuous

10 Packages Per lot 1 x 400 m each USTER® TESTER

USTER® QUANTUM

USTER® QUANTUM EXPERT

1 x 100 m each USTER® AUTOSORTER

Table 7



Combination of on-line and off-line quality management on a rotor spinning machine


Rotor spinning Yarn faults N/S/L/Tmachine Foreign fibers

Moiré, Pearl chainEvenness RunningImperfections productionHairinessNumber of piecersClassification of yarn faultsClassification of piecerEfficiency RunningProduction per kg productionStop timeAlarm timeYarn countCV Yarn countEvennessSpectrogramDiagramImperfectionsHairinessYarn diameterDensityTrash contentTenacity USTER® TENSORAPIDElongation USTER® TENSOJETTwist 10 Packages once per week 10 Tests/package Zweigle

Friction 10 Packages once per month one test each Schlafhorst

Moisture content 10 Packages per lot one test each MahloClassimat Packages once per week 1000 km USTER® CLASSIMAT

USTER® TESTER

USTER® QUANTUM

Continuous USTER® QUANTUM EXPERT

USTER® AUTOSORTER

20 Tests/package

20 Packages once per day

Yarn Continuous

Yarn

10 Packages once per day one sample of 400 m

one sample of 100 m

ON-LINE

OFF-LINE

10 Packages once per day

Table 8 7 Influence of the relative humidity in the test room Material such as cotton, wool or even synthetic fibers absorb a certain amount of water. This water content depends, among other factors, on the relative humidity. The test results of the sensors, the count determination and the strength in particular are influenced by the water content. The following graph shows the influence of the relative humidity on the breaking force of yarns. The temperature was 20°C for all tests. The re-sults, which were measured at 65% humidity, serve as reference value and are set as 100%. Deviations from this reference are indicated as a differ-ence in percent for the various materials.



-30

-25

-20

-15

-10

-5

0

5

10

15

20

40 45 50 55 60 65 70 75 80 85 90 RH%

Cotton Wool / Silk Acetate Viscose Linen Polyamide Polyester

Fig. 2 Influence of the relative hu-midity on the breaking force of yarns

It is important for that tests are always made under the same conditions otherwise the results cannot be compared. There is an international stan-dard called ISO 139 for the standard climate of a textile laboratory. This standard also demands that the material to be tested has to be exposed to the standard climate for a certain period so that the material to be tested adjusts itself to the standard temperature. All measurements should generally be made in this standard climate. Un-fortunately this is not always possible due to practical reasons because a spinner wants to check his production as quickly as possible. This is often true for slivers whose evenness should be checked. In such cases it is pos-sible to acclimatize the test samples to the standard climate as described above. As a rule, this process needs a minimum of 24 hours. There is a rule of thumb which says that the test samples should be meas-ured immediately, in other words without waiting. If this second method is used, all further measurements have to be made in exactly the same man-ner. It is not advisable to switch between these two test methods because the results cannot be compared with one another.



8 Summary The test frequencies described in the chapters above should serve as a tool for the spinning mill. As each spinning mill is different, it may be that some adjustments have to be made. There may be cases where no online measurement can be carried out or certain test instruments are not avail-able. The test frequencies described above assume an optimum situation. The size of a spinning mill may also require more or less tests that have to be adjusted accordingly.



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quality management in the textile laboratory

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