APPLICATION REPORT QUALITY MANAGEMENT The standardization of quality characteristics in the textile supply chain THE STANDARD FROM FIBER TO FABRIC R. Furter October 2009 SE 634
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Contents 1 Introduction... 5 2 Standardization of cotton fibers... 5 2.1 Standardization of cotton fiber characteristics in cotton producing countries... 5 2.2 Standardization of fiber testing in spinning mills... 7 2.3 Basics of Fiber Quality Profiles... 9 3 Standardization of yarn quality characteristics... 11 3.1 Standardization of the yarn quality characteristics in spinning mills... 11 3.2 Basics of yarn quality profiles... 12 4 Conclusion... 15 USTER PRODUCTS 3 (16)
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1 Introduction Textile specialists and managers may have noticed that there was a significant evolution in textile measuring technology in the past four decades, particularly in the area of cotton classification and yarn testing because in these two domains modern sensor technology and sophisticated scientific methods can be applied. As a result, cotton of various growth areas as well as all kinds of yarns can be compared easily because accurate figures are available. This will lead to a standardization in the textile industry. 2 Standardization of cotton fibers 2.1 Standardization of cotton fiber characteristics in cotton producing countries For a long period cotton was tested visually, mostly by certified classers, because accurate electronic systems were not available. But the only quality parameter which certified classers could determine with a reasonable accuracy was the fiber length. Many additional quality characteristics which are nowadays also important such as the short fiber content, the fiber strength and elongation, the maturity, the number of neps, the number of dust and trash particles, could not be determined or had to be determined with time-consuming manual instruments. Therefore, the United States Department of Agriculture already started a cooperation with the local electronics industry in 1968 to replace the certified classer by an electronic system. After an intensive development period the measuring system was available for large scale testing of cotton bales in the US cotton belt. A strong motivation for accurate electronic testing systems were correct incentives to farmers for the obtained fiber quality, better sales criteria for cotton trading and the superiority of the US cotton trading system. Other cotton producing countries followed. In 1999 similar classing offices were available for cotton testing in Uzbekistan. Subsequently, additional classing offices for cotton fibers were also installed in Australia, Brazil, India, Zimbabwe, Greece, Turkmenistan, Malawi, Mexico and Tadzhikistan. The China Fiber Inspection Bureau CFIB has also to installed such High Volume Testing Systems in various locations. By 2010 the classing offices in China will be completed. Table 1 and Table 2 show the replacement of the human classer by Uster Fiber Testing Systems and the percentage of electronically tested bales worldwide. Table 2 also shows the amount of cotton which is tested with USTER HVI Systems in 14 cotton producing countries in 2010. USTER PRODUCTS 5 (16)
Year Country 1968 USA USDA starts to replace visual fiber inspection by automatic testing 1988 USA USDA classification system complete 1999 Uzbekistan Classification system in Uzbekistan complete 2001 Brazil Part of cotton fiber production classified with HVI systems 2002 Australia Classification system in Australia complete 2004 India (Maharashtra) Part of cotton fiber production classified with HVI systems 2005 Zimbabwe Part of cotton fiber production classified with HVI systems 2006 Turkmenistan Part of cotton fiber production classified 2006 Malawi Part of cotton fiber production classified 2007 Mexico Part of cotton fiber production classified 2007 Pakistan Part of cotton fiber production classified 2008 Kazakhstan Part of cotton fiber production classified 2008 Greece Classification system in Greece complete 2010 China Classification system in China complete 2010 Tadzhikistan Part of cotton fiber production classified with HVI systems Table 1 History of classing offices for cotton fibers Country Cotton measured with USTER HVI in 2010 * USA 4,0 mn tons 17,2% Uzbekistan 1,2 mn tons 5,2% Brazil 0,2 mn tons 0,8% Australia 0,4 mn tons 1,7% India (Maharashtra) 0,1 mn tons 0,4% Zimbabwe 0,1 mn tons 0,4% Turkmenistan 0,06 mn tons 0,2% Malawi 0,03 mn tons 0,1% Mexico 0,03 mn tons 0,1% Pakistan 0,2 mn tons 0,8% Kazakhstan 0,1 mn tons 0,4% Greece 0,3 mn tons 1,3% China 7,1 mn tons 30,1% Tadzhikistan 0,3 mn tons 1,3% Total 14,1 mn tons 59,7% Percentage of electronically tested bales worldwide ** Table 2 Percentage of HVI tested cotton per country and worldwide * One USTER HVI System is used for the classification of 14 000 to 35 000 metric tons of cotton, depending on the number of shifts, the throughput rate of the HVI Systems and the duration of cotton classing per year. ** Estimation for 2010: Total cotton production worldwide 23,6 mn tons (Source: ICAC, September 8, 2009, Plenary Meeting, Cape Town, South Africa) 6 (16) USTER PRODUCTS
With the USTER HVI Systems a standardization of the cotton fiber parameters took place. As a result, the fiber parameters of cotton of various growth areas can be compared throughout the world. 2.2 Standardization of fiber testing in spinning mills Such USTER HVI Systems are also used for bale lay-down in spinning mills. With the single fiber testing system USTER AFIS the effect of the spinning process on cotton fiber quality parameters can be measured from the blowroom to the roving frame (Fig. 1). Bale Blowroom Card Drawframe Ribbon lap machine Comber Finisher drawframe Roving frame Bundle fiber testing (HVI) Entangled fibers Single fiber testing (AFIS) Entangled fibers Parallel fibers Fig. 1 Measuring range of fiber bundle and single fiber testing system The USTER HVI System is able to measure entangled fibers. Therefore, the USTER HVI System can be used for the measurement of the cotton quality characteristics in the bale and throughout the blowroom. The USTER AFIS System is able to measure entangled and parallel fibers. Therefore, in can be used for process control throughout the entire spinning process (Fig. 2). Blowroom Card Drawframe Comber Finisher drawframe Roving frame Ring spinning machine Winding machine Initial fiber quality, minimization of fiber deterioration Increase or decrease of neps, reduction of short fibers, reduction of dust and trash Maximum yield of fibers, maximum productivity, minimum raw material costs Efficiency improvement of subsequent processes, less fabric faults, less claims Fig. 2 Purpose of fiber testing in spinning mills USTER PRODUCTS 7 (16)
The USTER AFIS System is used for the measurement of fiber damage, the increase and reduction of neps, the reduction of short fibers, the reduction of dust and trash, etc., in each processing step. It is also used to maximize the yield of fibers and the productivity. In addition to this, the USTER AFIS System serves for maintaining the maximum yield of fibers and the highest possible production with the processed raw material. The USTER AFIS System is also a helpful tool to investigate efficiency improvements of subsequent processes such as weaving and knitting and to improve the appearance of fabrics. With these tools as well as with cost considerations by means of Uster Calculation Tools it will be possible to optimize the productivity as well as the costs. With the above mentioned USTER HVI System as well as with the USTER AFIS System it is today possible to measure a wide variety of quality characteristics shown in Table 3. USTER HVI System Moisture Content Micronaire Maturity Upper Half Mean Length Mean Length Uniformity Index Short Fiber Index Bundle Strength Bundle Elongation Color (Reflectance Rd) Color (Yellowness +b) Trash (Count) Trash (Area) USTER AFIS System Neps (Count) Neps (Mean Size) Fiber Neps (Count) Seed Coat Neps (Count) Length of 5% of the longest fibers Upper Quartile Length Mean Length Length Variation (CVL) Fineness Maturity Ratio Immature Fiber Content Trash (Count) Trash (Size) Dust (Count) Dust (Size) Visible Foreign Matter Table 3 Cotton quality characteristics determined by USTER HVI and USTER AFIS System 8 (16) USTER PRODUCTS
2.3 Basics of Fiber Quality Profiles In order to reach the specifications for a yarn agreed upon between a weaving/knitting and a spinning mill (Table 7 and Table 8) it is highly recommended to specify the minimum or maximum conditions for the raw material. Otherwise it will be difficult to reach a sustainable situation in a spinning mill. Fig. 3 shows the principles of a Fiber Quality Profile. Micronaire Fiber length Quality characteristics below requirements Short Fiber Index Uniformity Index Required quality characteristics exceeded Maturity Bundle Strength Reflectance Rd Yellowness +b Trash (Area) Trash (Count) Neps 0% 50% 100% Cotton Quality Profile defined by spinning mill Fig. 3 Optimization of the fiber quality characteristics based on a Fiber Quality Profile Fig. 3 shows that the raw material profile is not ideal for the yarn which has to be produced in the spinning mill. Some of the cotton quality characteristics exceed the requirements and some of the characteristics are below the requirements. The adaptation of the raw material quality to the needs of the yarn to be produced for a customer is a significant step towards quality consistency and reduction of costs. Therefore, the fiber purchasing as well as the blending in the blowroom is important. It is also obvious that in a spinning mill with a wide variety of yarns an ideal fiber blend cannot be realized, but it is highly recommended to approach the fiber quality profile as good as possible. This is the area where most of the cost savings can be realized. Table 4 shows an example of a spinning mill where there was a mismatch between the raw material requirements and the current raw material in the warehouse of a mill. It was the intention of the mill to come closer to the requirements for future fiber purchasing. The adaptation of the raw material to the requirement is also a significant option to lower the costs. Table 4 shows the ideal requirements of the fiber quality characteristics of the cotton bales based on a Yarn Quality Profile for a weaving yarn, ringspun, combed, cotton 100%, count range Ne 30 to Ne 50. Enduse: shirts. All these figures are measured with the Uster HVI Systems with neps feature. USTER PRODUCTS 9 (16)
Fiber parameter Unit Limit Value USTER STATISTICS Micronaire (-) Range 3,5 4, 25 75% Fiber Length UHML mm Min 28 (1 1/8 ) Reference Uniformity Index % Min 84 60% Short Fiber Index % Max 10 50% Maturity % Min 85 75% Bundle Strength cn/tex Min 26 50% Reflectance (-) Max 76 50% Yellowness +b (-) Max 9,2 50% Trash (Area) % Max 0,5 30% Trash (count) (-) Max 20 30% Neps 1/g Max 200 25% Table 4 Fiber Quality Profile, cotton bale, USTER HVI values This profile was based on an optimization process where the quality requirements of the customer, the sustainability of the quality as well as the costs played a fundamental role. The spinning process causes various changes of the fiber quality characteristics. The number of neps and the dust/trash particles are drastically reduced. The short fiber content, particularly in case of combing, is also reduced. If the fiber quality has to be known which finally ends in the yarn it is advisable to measure the quality characteristics in the sliver of the finisher drawframe. Table 5 shows a Fiber Quality Profile for a sliver of the finisher drawframe. These figures have to be measured with the Uster AFIS System. The fibers are used for a yarn of combed cotton, count range Ne 30 to Ne 50. Enduse: Shirts. Fiber parameter Unit Limit Value USTER STATISTICS Upper Quartile Length mm Min 30 (1 3/16 ) Reference Short fiber content (n) % Max 10 50% Fineness mtex Max 150 75% Maturity (-) Min 0,90 50% Immature Fiber Content IFC % Max 5,6 50% Neps 1/g Max 25 40% Dust 1/g Max 10 40% Trash 1/g Max 2 75% Visible Foreign Matter % Max 0,03 50% Table 5 Fiber Quality Profile, sliver of finisher drawframe 10 (16) USTER PRODUCTS
3 Standardization of yarn quality characteristics 3.1 Standardization of the yarn quality characteristics in spinning mills The standardization of the yarn quality characteristics began with the publication of the first USTER STATISTICS in 1957 which served as benchmarks to compare the yarn quality of various origins. The pressure for accurate yarn quality characteristics was intensified in the past 10 years due to the influence of the big retail names who had to improve the supply chain management in order to keep the quality claims within reasonable limits. For many spinning mills which have to supply yarns of consistent quality it was a requirement to improve the quality, the productivity and to reduce the costs. The tools for the determination of fiber and yarn quality characteristics were used to establish a future-oriented quality management. Table 6 shows an example of a Yarn Quality Profile with a list of parameters which can be specified in detail to be sustainable. There are also a few fiber characteristics listed in Table 6. Many yarn buyers do not specify the raw material because they are of the opinion that the spinning mill must have the degree of freedom what kind of raw material has to be used for a specified yarn. Test Quality parameter Test Quality parameter Fiber quality Micronaire Yarn Hairiness required Length Thin places Short fiber content Thick places Neps Neps Strength Strength Yarn Deviation of count Variation of strength Count variation Elongation Twist variation Remaining disturbing thick and thin places Direction of yarn twist Remaining foreign fibers Evenness Table 6 Quality characteristics which can be specified for a yarn The following items have motivated yarn buyers and retailers to better specify yarns and to establish Yarn Quality Profiles: For a sales agreement and for arguments in case of claims accurate figures are required to define the yarn Accurate figures are also required for spinning mills in order to deliver yarns of consistent quality In order to use the Uster Calculation Tools to quickly compute cost improvements in spinning mills, the managers of the mills need accurate figures to adapt the quality to the required specifications. USTER PRODUCTS 11 (16)
3.2 Basics of yarn quality profiles Yarn quality profiles containing a selection of quality characteristics mentioned in Table 6 are now well known in spinning mills. The yarn buyers are more and more in the process to exactly specify the minimum requirements for yarns. Such Yarn Quality Profiles are developed with the data base of the USTER STATISTICS as benchmarks. For spinning mills it frequently means a reduction of manufacturing costs because the raw material and the spinning process can be adapted to the minimum requirements listed in the Yarn Quality Profile. In addition to this, various reference figures are now available to monitor and improve the productivity and the costs. Fig. 4 shows the basics of a Yarn Quality Profile. Count variation Evenness Thin places Thick places Neps Hairiness Twist Twist variation Tenacity Tenacity variation Elongation Disturbing thick places Disturbing foreign fibers 0% 50% 100% Required quality characteristics exceeded Quality characteristics below requirements Yarn quality profile agreed with customer Fig. 4 Optimization of the yarn quality characteristics based on a yarn quality profile The important quality characteristics of a yarn have to be defined according to a specific yarn type and enduse (compact yarn, OE rotor yarn, air-jet yarn, woven fabric, knitted fabric, textile or technical application, etc.). These specifications are equivalent to the 100%-line in Fig. 4. Fig. 4 demonstrates which quality characteristics exceed the specifications and which characters are below the expectations. 12 (16) USTER PRODUCTS
Table 7 represents a yarn quality profile for a weaving yarn with only a few specified quality characteristics. Nominal Yarn Count Nec 30/1 Uster Statistics level Yarn Count and Twist Unit Limit Deviation of Count % max ± 2.5 Count Variation CVcb % max 1.5 50% Twist Multiplier alpha e - max 4.0 50% Variation of Twist CVt % max 3.0 35% Direction of Twist - Z Yarn Evenness and Hairiness Uster Evenness CVm % max 11.6 15% Thin Places - 50% 1/km max 1 15% Thick Places + 50% 1/km max 13 15% Neps + 200% 1/km max 26 15% Uster Hairiness - Range 4.0-5.0 5 60% Yarn Strength and Elongation Single End Strength, high speed, 400 m/min cn/tex min 21.5 25% Strength Variation CVb, high speed, 400 m/min % max 7.5 25% Single End Elongation, high speed, 400 m/min % min 5.8 25% Table 7 Agreement on minimum or maximum requirements / Ring-spun yarn, cotton 100%, combed, for woven fabrics, bobbins All the values are either specified as maximum values (count variation, evenness, imperfections) or minimum values (strength, elongation) or as a range (hairiness). All the values are based on the USTER STATISTICS as benchmarks. Table 8 shows a Yarn Quality Profile where minimum requirements for the applied cotton fibers are also specified. Particularly important for some yarn buyers are the remaining short fibers in the sliver of the finisher drawframe. USTER PRODUCTS 13 (16)
Nominal Yarn Count (Nec) 28 32 36 40 USTER Cotton Fibers Instrument Unit Limits STATISTICS Number of neps, bale AFIS 1/g max 270 270 195 195 50% Micronaire, bale HVI - Range 3.8 4.5 3.8 4.5 3.8 4.5 3.8 4.5 Fiber Length UHML HVI mm min 28 28 31 31 50% Fiber Length UQL(w), bale AFIS mm min 29 29 32 32 50% Short Fiber Content SFC(n), finisher drawframe AFIS % max 13 12 11 10 50% Yarn Count and Twist Deviation of Count UAS % max ± 2.5 ± 2.5 ± 2.5 ± 2.5 Count Variation CVb UAS % max 1.5 1.5 1.5 1.5 50% Twist Multiplier alpha e UZT - max 3.6 3.6 3.6 3.6 50% Variation of Twist CVt UZT % max 3.1 3.2 3.3 3.4 30% Direction of Twist UZT - Z Z Z Z Yarn Evenness and Hairiness USTER Evenness CVm UT % max 11.5 11.9 12.2 12.5 20% Thin Places - 40% UT 1/km max 24 40 62 91 20% Thin Places - 50% UT 1/km max 1 1 2 2 20% Thick Places + 35% UT 1/km max 172 213 254 294 20% Thick Places + 50% UT 1/km max 15 18 22 25 20% Neps +140% UT 1/km max 154 204 261 325 20% Neps + 200% UT 1/km max 24 32 41 50 20% USTER Hairiness UT - max 6.6 6.3 6.0 5.8 50% Yarn Strength and Elongation Single End Strength conventional, 5 m/min UTR cn/tex min 16.3 16.3 16.4 16.4 60% Strength Variation CVb conventional, 5 m/min UTR % max 7,6 7,9 8.2 8.4 50% Single End Elongation conventional, 5 m/min UTR % min 5.1 5.1 5.0 5.0 60% Single End Strength high speed, 400 m/min UTJ cn/tex min 18.3 18.4 18.6 18.7 60% Strength Variation CVb high speed, 400 m/min UTJ % max 7.9 8.2 8.5 8.7 50% Single End Elongation high speed, 400 m/min UTJ % min 4.9 4.8 4.7 4.7 60% Significant CLASSIMAT Faults, remaining A3+B3+C2+D2, cumulative * UCQ 1/100 km max 14 14 14 14 50% E UCQ 1/100 km max 0 0 0 0 50% H2 + I2 UCQ 1/100 km max 0 0 0 0 50% Foreign fibers A3+B2+C1+D1+E1, cumulative UCQ 1/100 km max 0 0 0 0 50% Yarn friction, waxed yarn Coefficient of friction UZF - max 0.16 0.16 0.16 0.16 Table 8 Agreement on requirements / Ring-spun yarn, cotton 100%, combed, for knitted fabrics, cones In addition, the maximum amount of remaining seldom-occurring events such as disturbing thick and thin places and foreign fibers are also specified in Table 8. List of testing systems: AFIS = USTER AFIS / Single Fiber Testing System HVI = USTER HVI / Bundle Fiber Testing System UAS = USTER AUTOSORTER / Count Measuring System UZT = USTER ZWEIGLE TWIST TESTER / Twist Measuring System UT = USTER TESTER / Multi-purpose Laboratory System for yarns, rovings and slivers UTR = USTER TENSORAPID / Single End Strength Tester UTJ = USTER TENSOJET / High-speed Single End Strength Tester UCQ = USTER CLASSIMAT QUANTUM / Yarn Fault Classifying System UZF = USTER ZWEIGLE FRICTION TESTER / Yarn Friction Measuring System * Cumulative means: The counts also include the values in higher classes (A4+B4+C3+C4+D3+D4) 14 (16) USTER PRODUCTS
4 Conclusion The accurate specification of cotton and all kinds of yarns (cotton, blended, 100% synthetic) is an enormous support for spinning mills to buy cotton according to minimum requirements. Together with a precise measurement of yarn quality characteristics a standardization takes place within a significant domain of the textile industry (raw material and yarn) where all the specialists and managers use the same language. USTER PRODUCTS 15 (16)
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