Knitted Fabric Quality Parameters PDF

Knitting Technology  Introduction ►At present knit fabric quality is decided by few physical parameters namely GSM, loop dimensions (loop length, wales and courses per unit length), fabric width, dimensional stability and defects in the fabrics. ...

Knitting Technology  Introduction ►At present knit fabric quality is decided by few physical parameters namely GSM, loop dimensions (loop length, wales and courses per unit length), fabric width, dimensional stability and defects in the fabrics.  Introduction ►However, aesthetic value of the fabric or the appeal to the customer regarding the fabric, which ultimately accounts for satisfying the customer, is not measured by these parameters.  Introduction ►At the same time the comfort properties of the fabric like smoothness and fluidity of loops that influences shear and low stress mechanical properties are also not sufficiently covered by above listed parameters.  Introduction ►Further, more than just the stability of the fabric/garment, for which knits are known to be poor, the localized variation in dimension would hamper the appearance and useful life of it.  Parameters Of Fabric Quality ►The quality of fabrics at micro level could be, loop- to-loop variation in their dimension including loop shape (not as a shape factor but as geometrical shape of the loop) and localised variation in loop density (rather than GSM).  Parameters Of Fabric Quality ►The important loop dimensions are loop length, loop width (wale spacing) and loop height (course spacing).  Parameters Of Fabric Quality ►The uniformity in dimension of loops provides attractive appearance to fabric, as it eliminates blurring effect of irregular dimensions. ►The fabric would be more elegant, lustrous, smoother, softer and stable.  Parameters Of Fabric Quality ►The uniformity in geometrical shape of the loop is another parameter, which affects the elegancy of the fabric and its fluidity. ►In most of the structures the loop is distorted during relaxation, chemical processing or during usage resulting in dullness, rough or ridged effect in the fabric.  Parameters Of Fabric Quality ►A standard loop shape is shown in Figure 1 for single jersey structure. ►The geometrical shape of a standard loop should have same curvature for crown & sinker loop (normally sinker loops are larger than crown).  Parameters Of Fabric Quality ► Both the arms of loop should be in the same plane. ►The bending of crown and sinker loop should be to an equal depth and without twisting or turning. ►The shape factor, ratio of width to height of the loop should be about 1.3.  Parameters Of Fabric Quality ►The contact places of yarn in loop interlacement should be at the junction of loop arm and the crown/sinker loop, ie, at points A, B, C and D in Figure 1.  Parameters Of Fabric Quality ►The variation in this loop shape and the dimension should be minimum. ►Such structures can be more resilient because the mobility of loops or redistribution of yarn in loops during any deformation would be easier. ►This would improve the dimensional stability of the fabric.  Machine Parameters ►Machine parameters and technology of the machine influence the fabric quality as well as the demand on yarn quality.  Machine Parameters ►Below are the main machine parameters which can affect the fabric quality needle type, take down system, gauge, cloth rolling or cam type, spreading, yarn feeding system, monitoring and number of feeders, control systems  Machine Parameters ►However, selection of machine or its parameters for knitting a particular yarn for manufacturing given GSM is crucial. ►The ideal count range for a given gauge has to be followed. ►The coarser gauge machine can knit with much ease compared to finer one for a given yarn.  Process Parameters ►The below process parameters plays a vital role in deciding the quality of the fabric. ► cam setting, ►delay time (in double ► speed, jersey), ► yarn tension, ► stitch length, ►sinker setting (in single► take down rate, jersey), ► condition of machine, etc  Process Parameters ►The knit fabric from similar yarn knit on similar machine (make and condition) with similar process parameters produce fabrics of different quality and some times beyond acceptable limits. ►This speaks about influence of variation in yarn and process parameters other than those considered today in the industry.  Process Parameters ►They can create difference in strain at different loops as also variation in their relaxation. ►This leads to loop-to-loop variation in dimension, geometrical shape as well as the localised variation in loop density.  Yarn Quality ►The purchase of yarn for knitting is based on the general parameters like count, U%, imperfections, strength & elongation and TPM.  Yarn Quality ►Most of the knitters in SMEs test only the count for setting the GSM of the fabric.