Optimized Knits booket


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Optimized Knits booket

  1. 1. How to the ect 100% KnitCreate P erf Cotton A Technical Guide to Improving Your Knit Products PRODUCE FIRST QUALITY KNITS REDUCE SURFACE FUZZING 100 Cot % INCREASE COLOR RETENTION ton CONTROL SHRINKAGE
  2. 2. About 60% of all garments sold at retail in the United States are knit products. In order to engineer the performance rightyour customers expect in a knit garment at the price they are willing to pay, it is important to make thedecisions about each stage of the manufacturing process. Today’s customers have myriad choices inapparel, so they often show little brand loyalty, and if a purchase fails to meet their expectations , they areoften willing to try something different.The consumer’s garment care practices can significantly affect the overall appearance and performanceof a cotton knit garment. Improper care results in disruption of the fabric surface, causing the garment to lose itsnew appearance and to wear out prematurely. If a knit product has a tendency to fuzz easily or loseits color quickly, this only makes the problem worse. Consumers average 5 loads of laundry per week and expect to wash a dark garment 15 times before it fades.
  3. 3. n 1 00%CottoHow to Create the Perfect Knit A Technical Guide to Improving Your Knit ProductsFor over 25 years, Cotton Incorporated has conducted research examining the various cotton knit manufacturing processes and their effects on theperformance and overall quality of the resulting consumer products. The quality of the final product is directly affected by decisions made about themanufacturing process with respect to fiber selection, yarn spinning systems, fabric construction, fabric preparation, and dyeing and finishing. Decisionsabout any of these manufacturing steps can give rise to problems downstream that may not be easily remedied, resulting in a less-than-optimal product.Such problems can be anticipated and prevented if you make well-informed decisions to engineer a product that meets both the retailer’s performancespecifications and price point and the consumer’s expectation of quality. Savvy choices will result in a product that is a good value and performs well interms of color retention, fabric appearance, and shrinkage. Armed with knowledge of the various manufacturing operations and how each step affectsthe next, your company can make better-informed decisions that will help you• save time and money at each manufacturing stage, by reducing costly mistakes and off-quality goods,• deliver a higher-quality product, resulting in fewer customer returns and greater consumer satisfaction, and• develop value-added products that garner higher margins.
  4. 4. Type of Product Decision Chart for Production of Knit Garments Being Made? Fiber Yarn Murata Vortex Carding Drawing Selection Quality? Spinning Combing Open End Pique Spinning Type of Fabric to be Product Interlock Roving Knit? Color? Compact Ring Spinning Jersey Conventional Ring Spinning Scour Bleach Cost? Fabric Characteristics? Performance? Understanding the interactions between manufacturing stages, the influence of one step on another, and the trade-offs that can be made will increase both the profitability and quality of your knit products. Bio-Polish No Bio-Polish Cost? This guide will walk you through the manufacturing process, step by step. Each important decision, from Fabric Characteristics? choice of spinning system to dye selection to choice of finishing process(es), will be addressed in terms Performance? of the effect it has not only on the final product, but also on downstream manufacturing steps. Vats Reactives Directs Cotton Incorporated offers unmatched industry knowledge and expertise, based on decades of experience and a comprehensive understanding of every step of the knit manufacturing process. The information presented here provides a head start to creating a high-quality knit garment. However, to Cost? Fabric Characteristics? truly create the perfect 100% cotton knit for your company’s purposes, please consult one of our experts Performance? in any of the fields addressed in this guide. Our experts will discuss with you the particulars of your manufacturing process and tailor the answers to meet your specific needs. Chemical Mechanical Finishing Finishing
  5. 5. Throughout this manual four different symbols will be used to indicate probable outcomes for options at each step. Key Learnings from this Guide: Below are the definitions and parameters of each symbols.  The yarn spinning system can have a direct effect on fuzzing during home Processing Time: Processes with this symbol will require additional manufacturing time. laundering, though it has little effect on color performance itself. $ Cost: Processes with this symbol will require additional expense.  Bio-polishing is an option to control fabric fuzzing Hand of final knit garment: Processes with this symbol create a favorable hand to the end  Surface fuzz on knit fabrics can create product. the appearance of color loss. +/- Fabric Appearance after Consumer Laundering: A plus (+) denotes positive appearance  Colorfastness is significantly affected characteristics (less fuzzing and pilling, greater color retention) while a minus (-) indicates by dye selection, as well as consumer the fabric will show greater amounts of pilling and fuzzing, and less apparent color care, including detergent selection. retention. See photo below  Selection of dyestuffs is a critical + step; reactive dyes maintain their color strength and shade better than direct or sulfur dyes.  Resin finishing is an alternative to bio-polishing for control of fabric fuzzing. A visual fuzzing scale used to numerically rate  Softener selection influences surface appearance and color retention.  The overall sequence of manufacturing processes can affect fabrics after laundering color performance.  Consumer care practices can affect fabric surface appearance -It is important to note the above symbols are assigned to each alternative in relation to other options at that particular point in themanufacturing process, and are meant to be used strictly as a guideline in making decisions. The actual amount of increased timeor cost will depend on the specific manufacturer.
  6. 6. Fiber Processingand Yarn Spinning Cotton fiber properties directly affect a knit garment’s quality, appearance, and performance. It is important to select cotton fiber with the appropriate properties for each specific end product. It also is important to choose the appropriate spinning system to produce cotton yarn that will yield the desired fabric characteristics. The three current spinning systems have different effects on the yarn structure and therefore on the final product. Sourcing companies must determine which combination of fiber and spinning system will result in a knit product with the desired key characteristics. Decisions made about yarn spinning will affect appearance, softness (which depends on yarn hairiness and twist), color retention, yarn strength for performance, and cost factors related to spinning.
  7. 7. Ring Spinning Open End Spinning Vortex Spinning (Conventional & Compact) $$$ $ $$ Courtesy of Sussa Courtesy of Murata Conventional spun yarn Courtesy of M.J. Grimson shown on the left, compact spun yarn on the right in Courtesy of M.J. Grimson both photos Conventional ring spinning is the oldest production method used today, yet incorporates many of the Open-end rotor spinning has a production rate up latest technologies. It is also the most expensive and to ten times that of ring spinning. Open-end rotor time-intensive system, because of the roving step at spinning begins with sliver fed into a combing or Vortex spinning, a form of air-jet spinning, has the the beginning and the winding step at the end. This opening roller. This process separates the sliver highest production rate of all the spinning systems. system allows for the largest range of yarn counts into individual fibers, which are transferred into a It begins with sliver fed into a high-speed roller and is capable of spinning especially fine counts. rapidly spinning rotor where the sliver meets the and apron drafting system. An air vortex imparts Compact ring spinning differs from conventional tail of the feeder yarn. Twist is inserted into the twist to the leading fibers as the fibers leave the ring spinning by using suction in the bottom roller exposed yarn end. The yarn package is ready to front roller; the air wraps the leading fibers around to control the fiber in a more uniform manner. As a be used right off the machine. Open-end spinning the core fibers. Yarn packages are ready to use result, the fibers are more tightly condensed when produces a smaller range of yarn counts than ring right off the machine. exiting the front roller. (See the photo above right.) spinning.Yarn Characteristics Note: Ring spinning is used as a benchmark for comparison of spinning systems Conventional Compact Open End Vortex Ring Spinning Ring Spinning Spinning Spinning Strength Lower cost High production rate Strength Flexible yarn count High production rate Yarn evenness Low yarn hariness S and Z twist yarns Lowest yarn hariness Resistance to abrasion Less bulky yarn High yarn hariness Yarn evenness Strength Less soft fabric hand Fabric fuzzing Limited yarn counts Low yarn hariness Low production rate Soft fabric hand Less soft fabric hand Less soft fabric hand High cost Strength Critical system to Low production rate Z twist only operate
  8. 8. Proper fabric construction is essential to creating a well- engineered garment. Fabric construction must be engineered from the start of the manufacturing process, through selection of the right fiber, the appropriate yarn for the specific knitting machine, and the right stitch length. At the next step of the process, dyeing and finishing can either improve or impair the Fabric performance of any given fabric construction. To produce a knit fabric that delivers the best performance at the desiredConstruction cost, well-engineered construction must be combined with the appropriate dyeing and finishing processes. A knitting mill should have knowledgeable staff who can engineer the fabric to the performance specifications provided by the customer.
  9. 9. Engineering Cotton KnitsCotton knit products must be engineered for performance. This means they must be planned, constructed, and managed correctly at each step of the knitting process. Many factorsrelate directly to the performance of cotton knits, including fiber selection, yarn type and knitting parameters. The most critical considerations in engineering a cotton knit are the con-struction variables and the length processing tensions.Construction variables:Factors relating to construction include fiber type, yarn type, machine gauge and diameter, stitch length, and type of stitch. This section focuses on the elements that are selected andcontrolled by the knitter.Yarn:Four main factors determine a yarn’s performance: size, type, twist multiple, and twist direction. The size of cotton yarn relates to its yield, width, and performance. Yarn size usually ismeasured by a cotton count system, which is an indirect numbering system; by the English cotton count system (Ne), the higher the yarn number, the smaller the yarn. Yarn type capturesthe spinning process used, how the yarn was assembled (e.g., single or plied), and whether it is a spun yarn or a filament yarn. Finally, yarn type and twist determine the hand, appearance,and strength of the fabric, and they are the main factors affecting skew or torque. TURNS PER INCH The shorter the stitch length: The longer the stitch length: TM (Twist Multiple) = √NE the less yarn in a stitch the more yarn in a stitchMachine Gauge: the tighter the stitch the looser the stitchThe machine gauge or cut is determined by the number of needles and the diameter of the machine. When the less the length shrinkage the more the length shrinkageselecting a machine gauge, you are also selecting a range of yarn sizes. Only certain yarn counts can be used the more the width shrinkage the more the width shrinkageon each type of knitting machine, and this factor determines the types of knit products that can be produced the narrower the fabric the wider the fabricfrom a given machine. Generally, the higher the machine gauge, the finer the yarns that can be knitted. the heavier the fabric the lighter the fabric the firmer the hand the softer the handStitch Length:Stitch length is the amount of yarn in one stitch repeat, and course length refers to the amount of yarn usedin one revolution of the knitting machine. Stitch length affects the weight, width, and shrinkage of the fabric.If the stitch is too short, excessive stress on the yarn and knitting elements can result in holes. If the stitch is too long, dropped stitches aremore likely. It is important to determine the proper stitch length for the desired fabric properties. As shown in the chart to the right, shortand long stitches affect the fabric’s performance in very different ways.A measurement related to stitch length is the tightness factor, a number that indicates the relative tightness of knitting, taking intoaccount both the thickness of the yarn and the length of the loops. The tightness factor is important because when this number is out ofrange, the machine can operate at lower efficiency and produce a fabric with defects or a harsher hand. In addition, knitting costs can behigher, because higher-quality yarn is needed than for the same type of fabric knit with a lower tightness factor. English Metric Suggested Tightness Factor Ranges 9.567 √TEX TF (Tightness Factor) = Normal Limits L in √NE L cm Single 14-18 12-20Type of stitch: Interlock 10-14 8-16Three basic stitches are available to a knitter: jersey, tuck, and float.These three stitches 1X1 Rib 14-18 12-20are combined to create a multitude of design and performance characteristics in Single Pique 14-18 12-20knit fabrics. Illustrations of these stitches can be seen to the far right. Six-Thread Pique 14-18 12-20
  10. 10. Controlling Shrinkage
  11. 11. Controlling ShrinkageIn today’s competitive markets, where high quality is expected at a low price, apparel companies are demanding low shrinkage. Furthermore, shrinkage must be consistent from garmentto garment in the same style and fabric construction. The term “shrinkage” is commonly used to mean any dimensional change in a fabric or garment - either shrinkage or growth - causedby the application of force or a change in environment. For a cotton garment, shrinkage characteristics affect parameters such as seam puckering, torquing, and overall garment fit.Shrinkage during the manufacturing process is caused by two types of factors: those relating to the construction of the fabric or garment and those relating to how the fabric or garmentis processed.Construction Shrinkage:Dimensional changes during construction occur as a result of such parameters as fiber, yarn, machine gauge, total number of needles, stitch or course length, and type of stitch. This typeof shrinkage is controlled by careful selection of construction parameters to meet fabric specifications.Processing Shrinkage:Dimensional changes during processing can occur during any dyeing or finishing step (whether chemical or mechanical) and usually affect both the length and width of the fabric. Keysto reducing shrinkage and improving fabric performance are processing the fabric with minimal tension and using compacting or relaxed drying steps.Various wet processing techniques have different effects on shrinkage. In general,batch processing (in a jet dyeing machine) applies less linear tension on the fabricthan continuous processing. Processes such as napping, sanding, and merceriza-tion apply high tension, while others such as relaxed drying apply low tension.Weft knits can be processed either open width or in tubular form. Each processapplies tension in different ways, and different processes used on the same greigeand dyed fabric will result in different performance. Resin treatment also has a Width stretchedhuge effect on both fabric strength and shrinkage. Above and right are illustrations of a regularRelaxed Drying Relaxed stitch fabric and fabrics that have been stretched. Length stretchedand CompactingRelaxed drying and compacting are two methods used for shrinkage control in knit fabrics. On the opposite page is a photo of a compacting machine. Below is an illustration of therelaxed drying process and a photo of the actual drying machine.In this illustration, fabric is fed in from the left into the dryer where it is dried with slack in the fabricto allow it to return to its pre-engineered shape.
  12. 12. FabricPreparationIn the preparation stage, the greige cotton fabric is scouredand/or bleached to remove impurities, thus increasing itswhiteness and absorbency. This step prepares the fabricto receive dye or other wet processes. One additional stepthat can be performed before dyeing, to ensure an endproduct free of surface fuzz, is bio-polishing. Bio-polishingis a cellulase enzyme treatment that removes cotton fibersprotruding from the yarn or fabric surface to create a lesshairy knit fabric with clear stitch definition. Bio-polishing isone way to clean up the surface of a fabric made of lower-quality yarn, but it should not be considered a cure-all forpoor-quality, excessively hairy yarn. Courtesy of Carolina Cotton Works, Inc. The photo to the right shows a Jemco Bleaching machine
  13. 13. No Bio-Polish - With Bio-Polish + $Fabrics not treated with cellulase enzymes tend to have more surface Bio-polishing can reduce fabric surface disruption on a garmentfuzzing after 20 home launderings. during home laundering. Applied correctly, it can impart an “as new” appearance that is maintained for the life of the garment. TheHowever, if fabric is to be finished with a resin treatment, bio-polishing combination of bio-polishing and a resin finish was most effective inmay not be necessary, because the resin will inhibit fuzzing during home reducing shade change after multiple launderings. However, usinglaundering and tumble drying. Choosing a less hairy yarn also could both bio-polishing and resin adds an extra bath, which translates toeliminate the need for bio-polishing. extra processing time and cost.The photos show non-enzyme treated (below) and enzyme treated(right) knit fabrics after laundering, as well as a close up of the fibers. How are fabrics bio-polished? Manufacturers use a bath or series of baths to bio-polish fabrics. Depending on other factors in the manufacturing process, this step can be done before or after dyeing. Bio-polishing parameters must be strictly controlled to avoid damage to the fabric as a result of the process. Processing time, temperature, pH, and the amount of enzyme in the bath must all be coordinated to achieve the desired result. If these factors are not at the correct levels, the fabric may have excessive loss of weight and strength.
  14. 14. Dye SelectionFabric appearance and color retention are significantly affected by dye selection.It is essential to select dyes that have the right fastness properties for the desiredend product. Within a class of dyes, quality and price can vary. Use of high-qualitydyes, from reputable suppliers, will improve fastness. It is important to understandthe different types of dyestuffs available for cotton and to understand thetrade-offs between performance and cost. Decisions made at this stage directlyaffect the garment’s colorfastness when laundered by the consumer.Another important factor is the process used to dye the fabric. Knits fabrics aremost commonly jet dyed in sealed vessels. Jet dyeing can be used with variousdye classes. In the dyeing process, it is essential to avoid excessive abrasion of thefabric surface, which will affect the appearance of the end product.
  15. 15. Choosing a DyeDye selection for cotton knits is an important part of the manufacturing process. As illustrated below, each dye class has both advantages and disadvantages. It isnecessary to understand these differences in order to select the dye that is best for your product. Shade Application Wash Light Crock Dye Class Brightness Time Fastness Fastness Fastness Reactive +++ +++ ++ ++ Direct ++ + +++ ++ + +++ +++ ++ Vat Sulfur + ++ + +CharacteristicsTo achieve a quality end product, dyes should have:  Good cold water bleed characteristics  Good colorfastness to levels of chlorine in municipal systems  Shading components with good performance properties  Durability to multiple home launderings Courtesy of Gaston County Dyeing Machine CompanyProcessIn jet dyeing machines, both the fabric and dye liquor are moved simultaneously. Fabric is moved through a venturitube, and dye is pumped through the tube as the fabric moves by. The photo to the right shows unloading of themachine after a dyeing cycle.Benefits of using a jet dyeing process: The greatest benefit is the versatility of being able to use the same machineto bleach, enzyme treat, and dye. In addition, jet dyeing uses a low liquor ratio; using less water saves on energy forheating the water and reduces the amount of waste water that must be treated and disposed of. New machines canuse a ratio of water to dye as low as 5:1.
  16. 16. FinishingAlthough the finishing of a knit fabric can make orbreak the final product quality, the other steps in themanufacturing process can have just as great an effect.In determining how to finish a product, it is essentialto understand that decisions in the manufacturingprocess are cumulative. Finishing is not a cure-all,and it cannot overcome limitations resulting fromearlier steps in the process. In fact, finishing can evenhave counterproductive effects if the manufacturingprocess has not been thought through all the wayto the end. Engineering of the product should startat the end of the manufacturing process and workbackwards. Identifying and understanding thespecific properties desired in the final product willallow you to make better-informed decisions foreach stage of the process, ensuring that the finishedproduct has the characteristics you intended.
  17. 17. Resin $ Finishing Options: $Resin treatment can be used in place of bio-polishing to reduce fuzzing. Its effects The options for finishing knit products are seemingly endless. Everythingcan be similar; however, resin alone does not improve the color performance of knit from water repellent to soil release to flame retardant properties can befabrics. Although resin can help maintain a knit fabric’s dimensional stability and control incorporated onto the fabric. In addition, surface finishes such as sanding,shrinkage, it can also weaken the fabric. The amount of resin added to the fabric should sueding, napping, and shearing offer ways to dramatically alter the handbe carefully determined to achieve a balance of performance and strength. or appearance of the end product. It is important to remember that all of these processes will affect the visual characteristics of the final product, including the color and shade. To ensure that the final product has theSoftener - $ desired properties, plans for finishing need to be taken into account when the choices are made for every earlier step in the manufacturing process.Some silicone softeners can make fabric more prone to fuzzing during laundering, causingthe perception of color loss. Choice of softener is key to minimizing surface fuzzing dueto repetitive laundering. Napping Shearing Water Repellent To the left is an illustration and a photo of a tenter frame. Fabric is fed through rollers (here shown from the right) and set into a frame to hold it in place. The fabric then enters several ovens, where the processing occurs. Tenter frames are used for many purposes, including drying and curing and controlling skew.
  18. 18. Consumer Care
  19. 19. Garment LabelingGarment care labels are an important factor in maintaining the quality and appearance of a knit garment once it leaves the store.Understanding consumer laundry habits and how clothes are washed helps manufacturers to reduce problems resulting fromimproper laundering, to prolong an “as new” appearance.Two thirds (67%) of consumers “always” or “usually” refer to the care label before washing.If a shirt fell apart in the laundry, only 17% of consumers would hold themselves responsible for not reading theinstructions. More than 70% would blame the manufacturer.Simple actions by the consumer can preserve the appearance of a knit fabric and lengthen the life of a garment: Turn garments inside out before laundering, to reduce fabric surface abrasion. Use detergents with chlorine scavengers, to reduce fading due to chlorine in the water. Set the right water level in the washer for the amount of clothes, to reduce fabric surface abrasion. Prevent over drying in the tumble dryer by checking progress frequently, to reduce abrasion and shrinkage.What Happens in the Laundry?Why did my shirt shrink in the dryer?Only 20% of consumers were aware that the dryer, not the hot water or the fiber type, causes shrinkage. However, many of theseconsumers incorrectly identified the heat from the dryer as the reason their shirt went down a few sizes. In fact, the culprit is not thetemperature; shrinkage actually is caused by the dryer’s tumbling action.Does abrasion happen in the washer or the dryer?Abrasion can happen in either machine as a result of overloading. When clothes do not have enough room to move around, theyrub against each other and machine components constantly. Consumers can decrease abrasion-related fuzzing by not overloadingmachines, as well as by turning garments inside out for laundering.
  20. 20. Cotton Incorporated World Headquarters 6 39 9 Wes to n Par k way Car y, N C 27 51 3 Tel. (91 9) 67 8-2 22 0 Fax (91 9) 67 8-2 23 1 www.cottoninc.comNew York  Osaka  Shanghai  Hong Kong  Mexico City