Knitting Calculation

(ii)Optimum input tension : i T = textex pergms 1.0 = 0.1 × 22 = 2.2 grams(iii)Runin and Run- in ratio: The optimum conditions for knit ability occurs attightness factor, K =

15.(a)As the Punto-di-roma structure (Fig. 14.6) is made up from both Rib and Plain knitsonly, the difference in Tightness K between these two units is approximately 20%i.e., plain K = 16.2 and rib K = 13.8 Now, the respective loop lengths are calculated as, p l

= p K tex = 2.1671.4 = 0.291 cm r l = r K tex = 8.1371.4 = 0.342 cmReferring the Puntodi-roma structure,When knitting

with dial and cylinder needles (feeder 1 and 2) the course length, r L = n. r l When knitting with dial or cylinder needles (feeder 3, 4) the course length, p L = n. p

l Where n is the number of needles forming the loopsFor Punto-di-roma, n=N/2Where N is the total machine needles of dial and cylinder i . e . , N = 2 () 2030 π =3772n= 23772 =1886 Now course length,

r L = 1886342.0 × cm p L = 1886291.0 × cmTherefore, Run-in r I =

1254.21886342.0 ××× speed = 381 feet / min p I = 1254.2181886291.0 ××× = 324 feet / min

Therefore, Run-in ratio= 324381 =1.2(b)As Swiss Double Pique is knitted with rib gaiting, all the loops are considered to be plain loops. i.e., p K = 16.2 and loop length, p l = 2.16 tex

= 0.291 cmAt the feeders (1, 3) where dial and cylinder needles form loops, the total number of needlesforming the loops are, n + 2 n = 2829Therefore, Course length produced with both dial and cylinder needles, d L ,

c = 291.02829 × cmFig 14.7At the feeders (2, 4) where dial only form the loops, n/2 needles form knit stitches and the samen/2 needles form the miss stitches.For miss stitches, Gl 1 = inches = 127.054.2201

=× cm d L = () 418.0943127.0291.0943127. 02291.02 ×=+= ×+ × nn Run in, d I ,

c = 4861253.218291.02829 =××× ft / min 2331254.218418.0943 =×××= d I ft / minT h e r e f o r e R u n in ratio= 1.2233486 = 14.3 ANALYSIS OF WEFT KNITTED FABRICS

To, understand the history of the fabric as well as for its reproducibility, analyzing the fabricstructure is important. Type of machine used and design principles can also be revealed byanalyzing the knitted fabrics. For fabric analysis a piece glass (i.e., a counting glass), a pair of scissors, ruler and calculator are needed. The following analysis sheet (Table 14.1) can becompleted after having thoroughly

analyzed the fabric. The following procedure may assist incarrying out the analysis. These are only guidelines and it takes time and practice to acquire theskill in the analysis.(i)Fabric Name: To find out to which type of the knitted structure the given sample belongs viz, single jersey, rib purl, interlock etc. For single jersey fabrics, loops areseen at the face side and yarn lines are

visible at the back as shown below: Fig. 14.8

Double jersey fabrics have similar appearance on both sides. By holding the fabric shorizontally, in such a manner to observe its cross section, the

rib and interlock structures can be found by their cylinder and dial loop arrangements as given below: Fig 14.9 (ii)Fabric Appearance: To find out the technical face and technical back of the fabrics.The top of the fabric is the edge that was knitted last. The face of the fabric is alwaysthe side with the most knit stitches.(iii)Yarn Type: The last knitted yarn is unraveled from the fabric

and is observed for itstypes such as single, double, blend, mélange, staple yarn, filament yarn s/z twisted,2/3 plyed etc.,(iv)Wales/cm and courses/cm: With piece glass, the Wales per inch can be measured andconverted into per centimeter. It is advisable to analyze always the back of the fabric,a n d p a r t i c u l a r l y f or unbalanced fabric, the back is obvious.c = courses/cm and w =

Wales/cm(v)Loop length: Unravel 12 yarns from the sample and measure the total length, T L cm( i.e., L1+L2+L3…)Weigh all the 12 yarns together, in grams(wy)Find out the average length LAV = 12 T L Count the number of Wales occupied by LAV Now, the

average loop length = LAV /(vi) Grams per square meter: Cut a piece of 10 cm × 10 cm from the fabric sample Findout the weight of the sampl e, w Now, GSM = w 100 × (vii)Yarn Tex : Using the total yarn length and weight as found above, Yarn number can be calculated

as,Y a r n T e x = T y Lw 5 10 × (viii) Tightness Factor : Using the values of tex and loop length as found above, tightnessfactor can be calculated as ,TF l tex , where l

= loop length in cm’s(ix) Fabric construction: By carefully analyzing the fabric using a pick needle, the fulldesign repeat of the structure, number of feeders used, needle gating etc., can befound. The repeat can be drawn either as point paper design (symbolic nation) or yarn path diagram (diagrammatic notation).