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| Formulating equations for calculating of circular weft knitted fabric |
Fabrics are produced mainly by knitting technique and weaving technique. Knit fabric production is easier and quicker than weaving technique. Though knitting production is simple, its technical parameters calculation is complicated and difficult than weaving. Technical parameters involved in the knit fabrics are: loop structure, loop/stitch length, CPI ,WPI, GSM, shrinkage, spirality, fabric width etc. In reality knitted loops in the fabric is curvilinear in shape but this work has done necessary analysis to consider it like a circle, following thata circle geometry and corresponding formulae has been used in formulating some parameters of circular knitted single jersey fabric. It is very difficult to maintain& control circular knitted fabric parameters due to severalvariables (like yarn type, yarn quality, yarn twist, fabric structure, machine speed, machine rotation, yarn tension, take up tension & many more) related with circular knitting production and influences of them are unavoidable, so the parameters can be varying more than acceptable limit. But still the derived formulae focus practicalenvironmentand help to calculate parameters directly and easily.
Methodology:
The first attempt was to get a technical equation to calculate fabric diameter or width for factory use and for that several ways was followed, both searching books and trying to formulate new one. To have new equation, the proposed ideawas using circle for loops shape, then the same idea was used to calculate others parameters. All the equations were then checked with large number of factory data.
Related Terminologies & Definitions:
Knitting
Knitted structures are progressively built-up from row of intermeshed loops. The newly fed yarn is converted into a new loop in each needle hook. The needle then draws the new loop head first through the old (fabric) loop, which has retained from the previous knitting cycle. The needles, at the same time, release, (cast off or knock over) the old loops so that they hang suspended by their heads from the feet of the new loops whose heads are still held in the hooks of the needles. A cohesive knitted loop structure is thus produced by a combination of the intermeshed needle loops and yarn that passes from needle loop to needle loop.There are so many variables in knitting production like, yarn related (i.e. yarn composition, count, twist direction, twist per inch (TPI) etc.); machine related (i.e. machine diameter, machine RPM, rotation direction, no of feeder, VDQ pulley diameter etc.) & fabric related (i.e. fabric type, construction, stitch length, stitch density etc.) and this can vary fabric parameters at large.
Wales Per Inch
Wales per inch (WPI)indicate the total numbers of wales in one inch of linear fabric. WPI is one of the important parameters to determine GSM of fabric and other fabric properties.
Courses Per Inch
Coursesper inch (CPI)indicate thenumbers of coursesin one inch of linear fabric. In the same manner, CPI is one of the important parameters to determine GSM of knit fabric and other fabric properties.
Stitch length
Stitch length is theoretically the single length of yarn which include one needle loop and half of a sinker loopbetween that needle loop and the adjacent needle loop.The length is measured in millimeter (mm). Itinfluencesfabric dimension and other properties including weight.
Fabric Width
Where, d = Cylinder diameter, G = Gauge of machine
GSM
GSM means the weight in gram per square meter of fabric.
Fabric area density can be calculated by the following formula,
Here, T = Tex, S = Stitch density,
l= Stitchlength
GSM is one of the primary parameters for determining fabric quality and GSM depends on WPI, CPI, yarn count (Ne) and stitch length.The GSM cutter isvery popular and easy usable GSM testing instrument used in most of the knittingfactories.The construction of this cutter is very simple. It is circular disk of 100 square cm area with sharp blade attached to its edge. So 100 square cm of fabric can easily cut by it and weighted at the electric balance to get GSM Reading.
Technical formula used for GSM calculation,
Yarn Diameter Calculation:
In indirect system of yarn count, higher the yarn count finer the yarn
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