Woven Fabric Calculation

Cover Factor

Definit ion: Cover factor indicates the extent to which the area of a fabric is covered by

one set of threads.

For any fabric there are two cover factors: the warp cover f-actor and the weft cover f'actor.' l 'he

cloth cover f-actor is obtained by adding the weft cover factor to the warp cover.

CalcLr lat ion: The cover f-actor in SI uni ts is calculated as:

( 'over Fac tor 1S l )lltrcuJs Ic'nt .. --

'{ r//c'rl 0

I lxarnple : ' l 'cx-20. thrcads/cnr:2[l

Cover factor (SI ) : (2S x r /ZO; l l0 :12.5

Cover Factor (Pierce)

ovcr [ :ac to t ' (P ie rcc)n

lvhcre n: threads/ inch and N is cotton coLl l l t

t : rarnplc ' fex:20 coLlnt. threads/cm-28

Clotton CoLrnt:590 .5120 :29.5's- l 'hreads/ inch :28 x 2.54 - l I

Cover F actor (Pierce) :1 | I \129.5 :12.9

'l ' lrc resultaltt cover factor between Sl r-rnits and Pierce is less than 5o/o.

For any given thread spacing, plain rveave has the largest number intersect ions per t tni t

area. Al l other weaves have f-ewer intersect ions than plain weave.-fhe l ikely weavabi l i t l '

of al l labr ics woven with the same weave and f iorn sirni lar yarns can be forecast l io ln

their cover f-actor.

Plain weave f-abrics with rvarp and rveft cover factors of l2 in each direction are easy to

weave. Thereafter weaving becomes more di f f icul t and fbr cover factors of l4+14 fair ly

strong weaving machines are required. At a cover f-actor of l6+16, the plain structurejarns and a very strong loorr-r with heavy beat-Lrp is needed to defbrrn the yarns

suff ic ient ly to obtain a sat isfactory beat ing-up of the weft .

Three cloths with the same cover factor (K:12) woven rvith yarrrs of dif l-erent l irrear

densit ies are shor.vn in Table l . l t can be seen that horv thread spacing and l inear density

have to be adjLrsted to maintain the required cover factor and how cloth area density and

thickness are af ' fected.

Table I Cornparison of fabrics with identical warp and weft cover factors woverr with

yarns of different l inear densit ies (SI Lrnits)

Cloth Threads Der cm Linear densitv Cover factor Weisht thicknessI l l rl2 Nr Nz Kr K; (g/m') m m.,,

A 1 A- a 25 25 t2 t2 l 3 t ) 0 .28

B t2 t2 t00 100 t2 t2 260 056( l o () ,+00 400 t2 t2 520 l . 12

Fractional Cover

Ip fabrics constructcd f iorn yarns, cover may be considered as the fractiorr of the total

fabric area that "covered" b1,the component yarns. An over-si lnpl i f ication of the idea fbrwoven fabr ic is shorvn in F ig l l re l .

I : igurc I : I r rac t iona l Cover

' l 'hc rarrr has a circular cross-sect ion ol-dianrcter. r / . arrcl ad. iaccnt ) 'arns are cl isplaccd b1' a

distance s. I 'he f l 'act ional cover is then d/s.

I n t h c i d e a l r n o d c l . s r v i l l b e e q u a l t o l / n . w h c r e r i s t h e n u m b e r o l - t h r e a d s p c r u n i t I c - n g t hl l rc l iact ional cover could be exoresscd in tcrms of d arrd n

l r rac t iona l cover : c l X n

Grosberg showed that yarn diarnctcr d-1.44 l i ( tcx/ l ibcr dcrrsi t l ' x l0 r .

Fract ional cover.

C-4.,44 r(tcx/[ iber density) x threads/crrr x l0- '

lrxample: What is t l ie f iactional covcr tbr thc warp in a l 'abric with 35 ends/crn. \ \oventiom yarn of 30 tex' l ' l 'he f lbre density is 1.5 g/cm3.

Cr :4 .44 ! 30 /1 .5 x 35 x l 0 lctr:0.695

le. 690/o is covered by warp yarn.

WOVh]N-T AI ]R IC S' IRU( 'TU RL

)f)()' \,-____-,/ \*-/

I

Total Cover

l -he total area covered by the fabric (Plain r.veave) is ABCD. 'T'he shaded area is the part

of the total area .ou.r.d by both yarns, and. because of this, i t wor-r ld not be str ict ly '

accurate merely to add the ivarp and weft cover values together and qr-rote them as the

total cover.

rT

, --!

:-i

F i g u r e l : l . J n i t c c l l o f P l a i n l r a b r i c

f l te sf tadecl arcas arc eaclt dr x d: al ld thc total at 'ca ol ' the cel l is s1 x

By de f in i t ion . l iac t iona l cover . C . -d /s . Hcncc

d r : C r s rd: -C:s:

d r d : : C 1 s 1 C i : s l

I :xprcssed as a lpact iol of total : l l 'e3 S1 r s2. the shacled arca bccontcs:

5 a

h,xarrple:A plai l cottorr fabric is woven to thc fbl lowirrg dctai ls: rvarp: 20 tex, 28 ends/cm.

Wefi: 35 tex, 25 picks/cm (density of cotton 1.52 g/cm3)

What is the total cover f-actor?

Warp cover : Cr :4.44x r / :Ol t .SU x 28 x l0-3 :0 .451;

Wef l cover : Cz:4.44xr / :S l t .SZ x 25 x l0-3-0 '533

To ta l f r ac t i ona l cove r i s c1 + c : - C rc - - r : 0 .451 + 0 .533 -0 .451x0 ,533 :0 '144

l'heoretically, about 74o/o of the total area of this cotton sheeting is therefbre covered by

varn.

d r d : : C l s y C 2 s 1 / s 1 x s 2 - C r C :

be deducted f iorn the suln of 'Cl and C2,

Total f iact ional cover = Ct * C: - Cr C: