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CHAPTER 1: Introduction

1.1 Introduction

The major problem that occurs in the industry of knitted fabrics is the dimensional stability. The

knitted fabrics suffer from different types of distortions. These distortions are caused by different

ways and processes as well as technology. The chart below show the different types of existing

distortions that occurs in the textile tubular single jersey knitted fabrics.

Figure 1.Distortions that occurs in tubular Single jersey knitted fabrics

1.2 Spirality

Spirality is one of the main phenomenon problems in the textile industry other than the bowness,

skewness and the shrinkage. Spirality of single jersey knitted fabrics occurs when relaxed knitted

fabrics’ loops, which imply the courses and the Wales, show an angel other than 90 degree. On

the whole, in a perfect single jersey knitted fabrics construction, the courses must be 90 degree to

the aligned Wales. The Spirality on knitted fabrics produced by circular weft knitting machine

has been an historical phenomenon concerning the world of textile. It cannot be categories as a

knitting default as by default itself this effect on knitted fabrics is being produced.

Dimentional stability in Tubular single jersey knitted fabrics

Shrinkage Bowness Skewness Spirality

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However the problem of spirality can be cured using some finishing treatments such as stentering

where the fabric is being distorted in width wise for the wales to straighten. There are also some

chemicals finishing such as setting by resigns, heat treatment, steam treatment, mercerization

which are used to restore the wales and loops to 90° to each other but it has been reported by

domestic users that after 2 or 3 cycles of washing, seams displacement was occurring in the

finished garments.

1.3 Seams displacement

Seams displacement is the resulting effects of spirality in knitted fabrics which occurs in finished

100% cotton knitted garments and this where the real problem arouses at the production line,

where there are mismatched patterns, sewing difficulties and as well as the displacement of the

side seam which normally occurs after washing and tumble drying at industrial levels and also

after a certain wash cycle in domestic usages.

The seam displacement is in such a way that the side seams of the garments are displaced from

their initial place by rotating to the back and front of the garment. Figure 2(a) show a garment

before any relaxation process with the seams A and B. After the garment has been subjected to

some relaxation processes, like laundering, seams displacement occurs into the garment at figure

2(b), which is the Seam A has displaced to A1 and seam B has displaced to B1.

Figure 2. Seams displacement in knitted garments

A B

Side seams

Before Seams Displacement After Seams Displacement

A A1

B B1

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1.4 Problem description

The 100% cotton Single jersey knitted fabric is the most used fabrics structure in the world of

fashion as it satisfies the requirement of comfortability such as elasticity and lightness of its

structure. The production of this fabrics is also very rapid as well as it implies a low cost of

production compared to other complex knitted structures. But the fact that this fabric has the

default problem of spirality which results into seam displacement at the production line, so there

must be a way so that the spirality angle can be corrected or calibrated to its minimum. The most

reported parameter that was causing spirality angle was the machines parameters.

1.5 Aim

The aim of this project is to investigate on machine parameter which is varying the tightness

factor of the knitted fabrics.

The quality pulley of the weft circular knitting machine will be varied.

Samples of 100% cotton will be knitted from different adjustments of the quality pulley

wheels

Spirality angle and seams displacement test will be carried out on these grey knitted

fabrics of 100% cotton.

1.6 Objective

To find the spirality angle of the different fabrics tightness knitted from the different

quality pulley adjustments.

Evaluating spirality angle using the digital screen protractor software from a image

analysis technique using a 14 mega pixel digital camera for taking the photo of the

samples at an close-up view.

To find the effects that tightness factor has on seams displacement.

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CHAPTER 2: Literature review

2.1 Introduction to the subject

The aim of studying the spirality phenomenon is to understand the various factors affecting the

dimensional stability of knitted fabrics, so that we can get an idea about what is the parameter

that must be adjusted so that we get an optimum dimensional stability that can be established.

This can be attaining by analyzing of numerous possible factors that is influencing fabric

spirality. Since the begging of the discovery of spirality on knitted fabrics, researchers has been

keen to play along the different knitting parameters related to machine, fabrics properties as well

as yarn properties. Due to the complexity of the phenomenon of spirality, the problem has not

been deeply solved. The studies was based either on a limited number of factors or due to a

limited aptitude to prove the theory using experimental approach.

So in this review of literature, an overview analysis has been made about all these past

researchers and findings which contribute to the spirality on knitted fabrics with different fabrics,

yarn and machine related parameters and a partial study has been made about fabrics distortion

such as skew and bow in knitted fabrics.

2.2 The effect of number of feeders

A general study was carried out on spirality of single Jersey knitted fabrics by (Vishal Desale et

al, 2008) where core aspects like the influence of machine parameters were taken into concern

and the test were carried out on both grey and finished fabrics and it was found that spirality

increases when there is a high number of active feeders. As single jersey fabrics are being knitted

on circular machine, so it follows the spiral path of the knitting process as shown in figure 1, so

more feeders, more yarn is being fed to the knitting area and more spirals are being created in the

fabrics and this is the way that high number of feeders thus spirality is high.

Furthermore, if the knitting process of a circular knitting machine is examined closely, it can be

observed that the yarn being feed by the feeders go spirally around the knitting machine. For

example in Figure 4, we have feeder A and feeder B, on the circular knitting machine, so yarn

package A(Red) will make the first row turn around the tube helically, then the second yarn

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package B(blue) make the second row and the knitting action goes on like this spirally.( Zuleyha

degirmenci, August 2007) So in the formation of knitted fabrics , the loops are being subjected

to the knitting tension which goes around the knitted fabrics’ tube spirally and that is why when

the loops are in dry relaxed states as well as when it is processed in wet relaxation processes like

domestic washing followed by tumble drying, it tends to take back the spiral form, just as it was

formed in the knitting machines. This phenomenon of spirality is caused mainly by cotton knit

fabrics, when cotton fibers are in wet state, it swells causing changes in the loop shape which

resulted into dimensional and shape retention properties of the knitted fabrics( suh,1967)

Figure 4. Spiral path of yarns in a Fabric tube with two feeders

Yarn going helically in

the Fabrics tube

The helical path by the Yarn

Corn A

Corn B

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2.3 Twist factor

Twist factor is the number of turns inserted during the production of a yarn in relation to its

linear density, as described in the following formula:

TF = TPCm x √ T, where T signifies yarn linear density in Tex.(A.R Horrocks & S.C

Anand.2000)

This formula of twist factor is relatively derived from the relationship between twist angle and

yarn count. Going back to the root of the formation of yarn, in staple yarns, twist is the key

method to bring fibers together to form yarns (by hearle,Grosberg & Backer, 1969). Twist bind

the staple fibers together by frictional forces It provides the yarn with an appropriate strength as

well as tension within it. So these fibers are bending together into approximately a helical shape

which makes a turn around the yarn axis (see figure 5.a), which were defined by (Platt and

postle. 1968).The twist angle is found between the tangent and the helix formed by the fiber axis.

We can see the angle more clearly when the helix is slip into a square, thus the angle θ becomes

hypotenuse of the right angle triangle (see figure 5.b)

Figure 5. Idealised cylindrically helical path of a fiber within the yarn (Hearl et al. 1969)

Yarn which have lower angle has low twist and they are normally soft and bulky. Yarns with

high twist angles are strong and over twisted yarns will have very high twist angles and they are

normally very hard, weaker and snarl easily.(Anon. 3 March 2003)

(a) (b)

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Furthermore, analysing to the core of the happening, the crew of (Jiang Tao et al. January 1997)

has also focused on the yarn construction which contributes to spirality of knitted fabrics. They

have assessed 3 different yarn counts with each of 4 different level of tightness factor and the

samples were washed and tumbled dry. The yarn count and the tightness factor were kept steady

while the twist factor was varied and they observed that it has a great impact on spirality. More

twist is inserted, more spirality occurs as yarn twist multiple has a tendency to untwist to its

original position when it is under relaxation process, as it has been under continuous torque

during the spinning process. This property of the yarn is called as twist liveliness.

The same research about yarn parameters was carried out by (V.K Kothari et al. September

2011)where the researcher has used nine types of combed cotton yarns with the varying of three

linear density values and each counts had 3 different twist factors. In this test the stitch length of

the samples also was varied. V.K Kothari had observed that as the yarn twist level increases,

there was also an increase in spirality and in parallel when the stitch length was increased; this

also was resulting into a higher angle of spirality. So this implies that the findings of Jiang Tao

correspond to that of V.K Kothari and a plus point was added to the fact that a fabrics with

bigger loops also contributes to the high angle of spirality.

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2.4 Twist liveliness

When yarns are twisted together in a helical order, it will tend to produce a torque within the

yarn axis which results into releasing the strain arising from the stresses that has been created

during the twisting action. So the yarn has a tendency to untwist or snarl before any relaxation

process is done to the yarn. This property of yarn is called the twist liveliness of yarn. One of the

main causes of spirality is the twist liveliness of spun yarns, which has been studied by (Lau, Tao

& Dhingra. 1995). Before we understand how twist liveliness is a contributing factor leading to

spirality, we must understand how the twist liveliness reacts within the fabrics.

A stable loop normally looks like in the figure 6(a) below which are symmetrically balanced

about the axis X-X1, but the fact that yarns endure residential torque and try to rotate inside the

fabrics, so distortion of loops occurs by the unbalanced tension in the two legs of the loops, see

figure 6(b) and it rotates about itself (Motee dewsaw.1997). This is how partially spirality occurs

in plain single jersey knitted fabrics.

(a) (b)

X

X1

Figure 6. Loops distortion by unbalanced tension into the two legs of the loops.

Force

Fig (a)

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2.5 Measuring yarn twist liveliness

Twist liveliness of yarns can be tested using one among the three ways of measuring twist

liveliness in spun yarns, which is the indirect method, the direct method and Semi direct method.

The direct method, the torque which is linked with the twist in the yarn is directly

measured by using a torsion balance apparatus. The torque-twist and the torque-recovery

characteristics of yarns are measured.

The semi-direct method, it measure the twist lively yarn’s tendency to untwist when it is

free to rotate.

The indirect method, it support the fact that a twist lively yarn will untwist due to the

unbalanced twisted helix structure , which was forced during the spinning process.

Most of the time, the indirect method of measuring is used. .The yarn is taken randomly from the

knitting machine’s creel. A length of 100cm of yarn is taken from the bobbin, and both ends are

brought together and a dead weight is attached to the bottom of the yarn see figure below.

When both yarns are bringing together, the yarn will start to snarl and the number of snarls’ turns

are counted. This test must be carried out on 20 yarns of 100cm each to get an appropriate data

about yarn twist liveliness.

Dead weight

Two ends bring together

Snarls were formed

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2.6 Tightness factor

Fabric tightness is the relative looseness or tightness of knitted fabrics ,so as it implies looseness

and tightness of a knitted fabrics, the only things that can varies this is the loop length which is

also known as stitch length. When the stitch length is big, so the structure of the fabrics is

loosened and the fabrics become slack and when the loops are small, the fabric is tighter. All

these business of looseness and tightness of loops have an impact of the spirality of the knitted

fabrics.

Test on the effects of fabrics construction on spirality of cotton single jersey fabrics was carried

out by (Jiang Tao et al. September 2011), where the crew carried test on cotton yarns of 18,21,24

tex and twist factor 21,25,29,33,77 which gives different tightness factor. The samples were

washed and tumbled dry at 60°c followed by conditioning for 72 hours. It was experiential that

the spirality angle decreases as tightness factor increases and this implies that when the loops

were free to move about, spirality occurs and when the loops are compact , the rotation of the

loops are restricted thus spirality is deduced. So if a fabric is made up a twist-lively yarn, in

loosen structure, it is obvious that the spirality angle would be alarming but is the same fabrics

tightness is adjusted to rigid structure, the high level of inter-yarn friction in the loop will reduce

the tendency of loop rotation and this reduces the spirality in knitted fabric. The formulae for

calculating tightness factor (A.R Horrocks & S.C Anand.2000) are as follows:

:

Tightness Factor = √ tex count ÷ Stitch length

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2.7 Loop shape factor

The loop shape factor is the ratio of wales per inch and course per inch, briefly described by

(Hasan Shahariar.2012) in its research’s report. The loop shape factor has also been studied by

(Jiang Tao and al. January 1997).They has used the linear correlation methods and they

commented that the bond between loop shape factor and spirality as well as yarn count are very

weak. Nevertheless there is a connection between loop shape factor and tightness factor, and this

has also been proved using the partial correlation method where only two variables were taken

into consideration. It is also interesting to note that the weak correlation between yarn twist

factor and shape loop factor is transformed into strong relationship when in partial analysis.

Below there is derivation of the formula who to calculate shape factor of a knitted fabric taken

from the handbook by (A.R Horrocks and S.C Anand.2000).

kC, kW, kS are dimensionless constants, l is the stitch length and s is the stitch density

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2.8 Stitch length

Number of st itches and its size define the dimension of a weft knitted fabric. St itch

length can vary the properties of fabrics in terms of its weight and its structure . The

number of st itches and its size is controlled by the yarn feeding system in a knitt ing

machine, which is the series of posit ive feeders driven by the adjustable quality

pulley system. The formulae to calculate st itch length is as follows:

Stitch length in fabric = The Length of yarn (when unraveled)/ the number of loops

(Shahid et al .2010) made a research on ‘Spirality in cotton knit fabrics before and after

compacting using selected yarn count and stitch length’. Yarn of counts 26s/1 Ne, 28s/1 Ne, and

30s/1 Ne were used with varying stitch length of 2.58mm,2.63mm,2.68mm,2.70mm and

2.73mm. The samples were dyed, stentered at 150˚c and compacted. Spirality was tested under

65%± 2% relative humidity condition and the results that show the lowest % of spirality were

put together in the following arrangement of yarns’ Linear density, 26/1 Ne, 28/1 Ne and 30/1

Ne at stitch length 2.58mm, 2.70mm & 2.73mm before compacting and at stitch length 2.68mm,

2.70mm & 2.73mm after compacting respectively. Thicker yarns 26/1 Ne with smallest loops of

4.58mm before compacting is a combination found by the researcher for lower spirality % and

after compacting stitch length of 2.68mm (which is 3rd

position from smallest stitch length).

This indicates that it can’t really rely on the stitch length and linear density relationship as with a

26/1 Ne yarn of stitch length 2.68 it was observed to be receiving the lowest % of spirality, and

when the stitch length is 2.73 spirality is 2.5%, when stitch length is 2.63(which is 2nd

position

from smallest stitch length) spirality is 4.0%. There are not a follow up in the data, which means

no variation from small stitch length to big stitch length. However stitch length alone has an

impact on spirality, as the receipt for a high tightness factor implies the presence of a low stitch

length. Referring to the formulae Tightness Factor = √Tex count ÷ Stitch length (Handbook of

technical textiles by A. Richard Horrocks) ,it can be deduced that stitch length is an important

variable contributing to tightness factor.

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2.9 Twist factor v/s Stitch length

However (V.K Kothari. September 2011) disagree with this point of view that there is a

relationship between the yarn twist liveliness and the stitch length but he would rather consider

the tightness factor and the yarn twist factor together to be a contribution to the problem of

spirality in knitted fabrics and he proves this through a generated formula ;

Spirality angle = -95.633+6.160 (Tightness factor) – 0.393 (Gauge) + 4.774(Tex Twist Factor)-

0.266 (Twist factor x Tex Twist Factor),

In the above formulae, he try to show that the angle of spirality depends on the tex twist factor

and tightness factor. When the value of the TF is high, the spirality increases with respect to

twist factor which reduces to a large extent.

1.7 Yarn spinning methods

(Araujo and Smith.1989) has study on the effect of yarn spinning technology of jersey fabrics

dry and fully relaxed states for 100% cotton and blend of 50co/50pet. The methodology of the

test was like this, samples were dry relaxed for 24 hours followed by fully relaxed washing at

95° C in a top loading washing machine then tumble dried. The spirality angle for 100% cotton

was more than that of the blends in the fully relaxed state, the angle of spirality decreases as

follows; friction>ring>rotor>air-jet. For the blended yarns, the lowest angle of spirality were

obtained from both states, dry relax and fully dry relaxed were from the air-jet and the rotor

spinning.

1.8 Slubby Yarns

(Milon Hossain et al. March 2012) has focused on the ‘Impact of various yarn of different fiber

composition on the dimensional properties of different structure of weft knitted fabric’, in which

the research team carried of test on plain S/J fabrics, Slub S/J fabric, Cross Tuck fabric, Polo

Pique fabric, Single Lacoste fabric, Double Lacoste fabric, Lycra S/J fabric and Terry S/J fabric.

The yarn composition used were 100% cotton yarn, CVC (60% cotton+ 40% polyester) yarn,

mélange (85% cotton+15% viscose) yarn, PC (65% polyester+ 35% cotton) yarn and 100%

polyester yarn. Analyzing the data received from spirality test, it was found that slub single

jersey fabrics knitted from all the different yarns composition has higher spirality than the other

structures.

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Furthermore the theory of the Slub-yarn was studied by (Ruru Pan et al.2011). The composition

of the Slub-yarn is made up of two parts; the base yarn part and Slub part. In the figure 7, Lbi is

the length of base yarn; Nbi is the linear density of the base yarn; Lsi is the Slub length with

linear density Lsi, where i=1,2,3.

Figure 7.Structure of Slub-yarn (Ruru Pan et al.2011:P.25)

2.10 Twist direction (S-twist yarn & Z-twist yarn)

Twist in a yarn can be inserted in either S-Twist (which is in the clock wise rotation) or in Z-

Twist (which is in an anti-clock wise rotation). When a yarn is held in a vertical position and the

individual fibers seems to be in a diagonal way like the letter 'Z’ ,so it is call a Z-twist(see in

figure 8 a ) and when it is held diagonal appearing in a letter ‘ S’ , so it is call a S-twist(see in

figure 8 b) .Below there is an investigation where the researcher has commented on the effect of

yarn twist direction on spirality of knitted fabrics.

Figure 8. Twist direction in yarns.

(a) (b)

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One of the fundamental parameters that affect spirality of knitted fabrics is weight of the fabrics.

Experimentations were carried out on the effect of fabric weight on spirality of single jersey

fabrics, taking into consideration the yarn production technology. Different weight of 100%

cotton fabrics from different yarn types; carded z, carded s, were subjected to domestic

laundering and drying process. According to the results obtained, the domino effect of increasing

the fabrics’ weight is a low spirality angle and it has also come to this conclusion that the yarn

spinning direction has an impact on the machine’s direction.

Further observation was made on carded S, carded Z and carded S-Z verses the direction of the

circular knitting machine which was in the Z direction (anticlockwise). The results were that the

Carded S yarns had less spirality than the Carded Z yarns and the Carded S-Z had no spirality at

all. The researcher’s opinion on this fact was that the machine rotation and the yarn’s spinning

direction was opposite to each other, that is why there was less spirality in the Carded S yarn

while the knitting machine was rotating in the Z direction.( Züleyha Değirmenci & Mehmet

Topalbekiroğlu. April 2008). Commenting on the researcher’s opinion, S carded spun yarn

follows the direction of clockwise movement and when it will be subjected to wet relaxation

process, it was suppose to go back to its original position which is counter-clockwise and in this

test, the knitting machine also was going into the counter-clockwise direction, so was the

researcher’s view correct about the fact that direction was opposite to each other and this was

causing less spirality?

2.11 Fabric relaxation.

Fabric relaxation is a method used to removes the residual knitting tension that was produced

during the knitting of fabrics. As it has been studied before in this project that residual torque

occurs in a fabric while it passes certain steps in the knitting process, so when relaxation

treatment is carried out on the fabric, the residual yarn torque is relived and it results into

changes in the molecular structure and increasing yarn mobility. There are two types of

relaxation process that fabrics pass through after the knitting process; the dry relaxation process

and the wet relaxation process.

(Munden. 1959) has studied on fabric relaxation and fabric geometry with wool yarns and he was

the first one to introduce two types of relaxation states which is dry relaxation and wet

relaxation. When a fabric is arrived from the knitting factory, before any procedure take place,

the fabric is a unrolled and is allowed to relax freely for 24 hours and this is called dry relaxation

and nowadays we have machine with air blowers which relaxes the fabrics(seen a tropic knits

Mauritius) which accelerate this procedure and gives better results. However the fabrics is in an

state of equilibrium after static relaxation is water is done followed by drying processes (tumble

drying), this process of laundering fabrics and tumble dried it is known as wet relaxation.

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Tumble drying is a crucial point to focus on which very few researchers have put emphasis. This

is one of the main operations being carried out at industrial levels just prior to the laundering

process, which form part in the wet relaxation process. Here comes (L.Higgins et al.2003) with

the project ‘Factors during tumble drying that influence dimensional stability and distortion of

cotton knitted fabrics’.

The researchers has put prominence in the influences of moisture content, mechanical energy

and heat on dimensional stability and distortion during tumble drying from 100% cotton knitted

fabrics. As samples, there were three commercially finished fabrics, plain single jersey, interlock

and lacoste fabrics which were made into an open pillowcase of 50 x 50 cm2. The samples were

washed in domestic washing machine and then were tumble dried at 65-75° C and at 22° C then

flat dried at 65-75° C.

The researcher has commented on the effects of moisture content on distortion during tumble

drying; they had observed that on plain single jersey knitted fabrics, the degree of spirality and

level of skewness was higher than the other two fabrics. The degree of spirality and skewness

also decreases for all fabrics at 65-75° C. For the plain single jersey fabric tumble dried at 22° C,

it was observed that the dimensional stability was same when it was dried at 65-75° C. However

then the single jersey sample was subjected to flat drying at 65-75° C, results was better.

(Jiang Tao et al.1997) has also compare the partial wet relaxation behavior verse tumble drying

relaxation process and they deduce that when the fabrics is subjected to mechanical action and

agitation which implies laundering and tumble drying, the angle of spirality rises.

Laundering has a great impact on dimensional stability and it is the core process where spirality

and all sort of distortion occur in a knitted single jersey fabric, so when fabric distortion test are

being carried out, it is crutial to adopt certain laundering regimes. (S.C.Anand et al. June 2002)

have study the different washing and drying regimes in single jersey, 1x1 rib and interlock

fabrics. The samples were washed and dried in 5 cycles of 4 different regimes; fully finished

parameters, water wash with line drying, detergent wash with line drying, water wash with

tumble drying and detergent wash with tumble drying. The fabrics where washed in 42°C and

rinsed in cold water and were tumble dried for 60minutes at 75°C or line dried for 24hours.

After the entire test and analysis, they came to the conclusion that plain knitted fabrics show

more spirality than the other structures. Commenting more on the laundering regimes, the plain

single jersey fabrics shows a greater angle of spirality when washed with detergent and tumble

dried (6.5°) and secondly then it is water washed and line dried(6.0°). The researchers had also

focused on the different processes of laundering which is; wash, rinse, spin,, tumbling heat,

tumbling agitation. They found that tumbling agitation was the main cause for changes in fabrics

followed by spin which was the second provider.

.

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2.12 Bowing

In knitted fabrics, bow and skew occurs when the courses pattern are distorted across the width

of the fabrics.

Generally, we say that a knitted fabric has a bow when courses lies in an arc across the width of

the fabric from one end another end or selvages (see figure 9a). The bow formed in the middle of

the fabrics is either ahead or behind to the perpendicular line being drawn across the width of the

fabrics from selvages to selvages. However, bow in fabrics are not only the arc across the edges

but there are various types of bow conditions which occurs in a knitted fabrics (see figure 9b).

Figure 9(a) Bow in knitted fabrics. (ISO BS: 1990, reapproved 2006)

Selvage Selvage

Width

Perpendicular line drawn Bow

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Figure 9(b).Types of bowing that occurs in knitted fabrics (ISO BS: 1990, reapproved 2006)

a) Bow- an arc to the perpendicular lines across the width of the fabrics.

b) Double bow, two fabric bows, arcing in the same direction, as in a flatted M or W

depending on the viewing angle

c) Double hooked bow, one hooked bow at each side of the fabric that arc in opposite

directions.

d) Double reverse bow, two fabric bows arcing in opposite directions.

e) Hooked bow, fabric condition in which the filling yarns or knitted courses are in the

proper position for most of the fabric width but are pulled out of alignment at one side of

the fabric.

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2.13 Skewing

In knitted fabrics, the courses was supposed to be perpendicular to the edge of the fabrics as

illustrated in (figure 10a), but after some cycles of laundering and tumble drying, the loops got

angularly displaced from the ideal perpendicular angle, (see figure 10b). Skew occurs at the top

and bottom part of a tubular knitted fabrics (ISO BS: 1990, reapproved 2006).

According to past researches, there are two types of skews. When Wales are skewed from the

vertical, then we get ‘wale skew’ in the fabrics, on the contrary when the courses is skewed from

the horizontal so it said to be a ‘course skew’. Skew in fabrics occurs when they are allowed to

relax just after it has been knitted on the circular knitting machine. It has been reported that

drying knitted fabrics without tension maximize skewness (Technical bulletin. 2002).

Width Width

Length Length

Figure 10(a) Loops arranged 90 degree to

the edge of the fabric

Edge Edge

Figure 10(b) Loops are angularly displaced

from a line perpendicular to the edge

Skew

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The causes of skewness in knitted fabrics have been further elaborated in the (Technical

Bulletin.2002) by cotton incorporated. The researchers has emphasized on the yarn parameters,

the number of feeders on the machine, which is mostly the same parameters as the problem of

spirality. The problem of yarns is associated to the steep alignment of the Wales around the tube,

as show in (figure 11). the Wales goes spirally round the tube, thus in this case wale skewing

occurs.

Figure 11.Steep Wales on the tubular fabrics (Technical Bulletin.2002:P.3 fig 3)

After the wet processing of laundering and tumble drying relaxation, the tubular knitted fabrics

will be opened, then automatically the wales will straighten parallel to the edge of the fabrics and

now the results will be skew of the courses horizontally, which is known as course skew. See

figure 12 below.

Wale

s

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Figure 12.Skew of course loops where the rows of wales are straighten parallel to the edge of the

fabric (Technical Bulletin.2002:P.4 fig 5).

The course skew is linked also to the machine parameters such as the number of feeders. The

more the feeders on machine, more courses will be present in the fabrics and more courses may

skewed! Added upon the fact that circular knitting machines knits spirally, so each course is

piled upon each other which will be a factor for skewness to occurs. So both, number of feeders

and the spiral knitting of the circular knitting machine contributes to the problem of skewness in

knitted fabric

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Knitting machine

Flat bed knitting machine

Circular knitting machine

circular warp knitting machine

Circular Weft knitting machine

Single knit

(cylinder only)

Double knit

(cylinder & dial)

2.14 Classification of knitting machines

Figure 13. Classification of knitting machines.

2.14.1 Circular knitting machine

Circular knitting machines are tubular machines that knits spirally with the outcome fabrics

which is in a tubular form and without seams, usually for cutting facilities of tubular fabrics, at

industries they always put a needle-out otherwise there are machines that have a blade at the

bottom which cut the fabrics and enroll it in tubes. Among the circular knitting machines, there

are two main types of machines that are used at industrial level; the warp knitting and the weft

knitting. These two types of knitting technologies vary in their fabrics structure and properties.

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1. Warp knit

A warp knit is a procedure of producing fabrics in which the stitches are formed

vertically or warp wise direction. The yarns are arranged just like as the warps on the

beams, with the ends attached to the needles. The fabrics have a flatter, closer and less

elastic knit.

2. Weft knit

Weft knit is the knitting technique that is mostly used in the industries rather than the

warp knit. The loops are formed horizontally in the weft wise direction. The outcome

fabrics are more elastics and it is the only fabrics that most of the population uses

In this project , fabrics made from a weft circular knitting machine will be assed as the spirality

problems occurs mostly on the weft knitting machine and the fact that the weft knitting machine

is mostly use at industrial levels, the picture below is showing a weft circular knitting machine

with a cutter integrated at the bottom.

Figure 14. Circular weft knitting machine

25

2.14.2 Yarn passage for knitting on a weft circular knitting machine

The diagram below show a brief overview of the yarn passage for knitting on a weft circular

knitting machine. The package held on the creel at (A) feed the positive feeder (B) which is held

on a belt driven by the quality pulley adjustment (C). The yarn is feed at constant rate from the

positive feeder to the feeders (D) which deliver the yarn to the needles, while the cylinder (E) of

the machine is rotating at the same time in a specific direction. In this way, the fabrics is being

knitted spirally and it is being take down on rollers at (F) .

Figure 15. Showing the passage of yarn on the knitting machine

A

B

C

D

E

F

26

2.12.3 Different parts of a weft circular knitting machine

Figure 16. Different parts of the ‘Terrot’ circular weft knitting machine, found at University of

Mauritius, which was used to knit the sample.

1) Positive feeder

3) Feeder

2) Central stitch

adjustment meter

6) Quality adjustment pulley

4) Cam box 5) Individual stitch cam

adjustment

27

2.14.4 The functioning of the different parts of a weft knitting

machine

In a knitting machine there are two types of overhead feeders, the negative feeder and the

positive feeder. On the knitting machine ‘Terrot’, which has been used to knit the samples at the

University of Mauritius, positive feeder (1) are being used as it has more control over the

knitting of plain single jersey fabrics. The positive feeder is a device in the knitting machine that

takes yarn from the yarn package on the creel and delivers it to the needles. The device has a

amount of yarns which has already been enrolled into it, and as the positive feeder is feeding

yarn to the feeder found at the knitting section (3), at the same time yarn from the yarn package

are being reenrolled into the positive feeder. So the yarn feeding from the positive feeder to the

feeder at the knitting area is mostly constant under same tension.

The positive feeder are driven by a belt (see figure 17(a) )which is connected among all the other

64 feeders on the knitting machine contributing to the yarn feeding wheel around the machine

and the feeding rate are equalised. The rotating belt is connected to the quality adjustment pulley

(see figure 17(b))

Figure 17(a). The belt rotating the positive feeder

(J.Adolfsson.1998:P.716, fig 1)

Figure 17(b). Schematic diagram of the

positive feed system driven by the quality

pulley (J.Adolfsson.1998:P.716,fig 2)

Fd1-N Positive feed

Qp Quality pulley

GR Guide roller

TR Tape tension adjustable roller

28

2.14.5 The quality adjustment pulley

The quality pulley is a adjustable diameter which is driven by the main engine in the knitting

machine connected through the gears system. So for adjusting the stitch length, which influences

the weight of the fabrics, the quality pulley’s diameter is tuned by opening it more or closing it.

The quality pulley contains numbers from 10 to 0 (see figure 18) which is adjustable. Each time

the wheel is rotated from one number for another, it is either increasing the diameter of the

pulley by 2mm or reducing it by 2mm and this has an impact on the speed at which the set of

positive feeders are feeding yarn to the needles. The technical name used for adjusting the

quality pulley wheel is ‘LFA’, ‘Longuer de Fil Absorber’.

Figure 18. The quality pulley adjustment wheel.

The mark which is fixed

The adjustable diameters starting

from 0 to 11

29

Furthermore , when the quality pulley’s diameter are being adjusted, the results will be either

feeding more yarn to the positive feeder or less, so this will have an tensional impact on the

feeding of yarns from the positive feeder to the needles. The tension from these two points will

either increase or decrease, so in this case we use a tension meter to check the tension of the yarn

feed(see figure 19) and then the tension is adjusted for each yarn feed by adjusting the

‘individual stitch cam adjustment’ or the ‘central stitch adjustment’.

Figure 19.The machine technician is testing the tension from the positive feeder to the knitting area by

using a tension meter

30

CHAPTER 3: Methodology

3.1 Material and sample production

In this part of the project, the experimental procedures and the material used will be fully

detailed so that we have an overview about how to achieve the main goal of this project. Fabrics

of 100% cotton of 24/1 Ne was taken as sample because cotton is the most reported material for

spirality in knitted fabrics due its properties and its heliacal formation when during spinning of

the cotton yarn. The fabrics were knitted at the University of Mauritius, using the Terrot circular

knitting machine with the following parameters.

Gauge: 20

No. of needles: 1284

Machine diameter: 20

No. of positive feeders: 64

Cam setting: knit. Knit.

According to the project’s aim, effects of tightness factor was to be observed on the spirality

angle and seams displacement. One of the machine parameters was adjusted, which is the quality

pulley wheel and it has a direct effect on the tightness factor of the knitted fabrics. It has been

previously studied in the literature chapter that the quality pulley has a control over the whole

positive feeders on the knitting machine by accelerating and decreasing the speed of yarn feeding

keeping in tract that during the whole samples making procedure, the Rpm of the machine was

kept constant at 13.5Rpm.

The quality pulley wheels contains numbers from 1 to 12.The wheel was adjusted by opening its

diameter from 10 to 6. Five samples of different quality pulley adjustment were knitted. At

Different knitted fabrics, the diameter of the Q.P wheel were being enlarged in diameter and the

resulting knitted single jersey fabrics’ specifications was as follows:

Fab

no.

Q.P meter

adjustment

Diameter of Q.P

wheel increased by

Central

stitch

adjustment

Stitch

length

Tightness

factor

Shape

factor

g/m2

(GSM)

1 10 4mm 15 0.350 14.17 0.73 143.8

2 1 2mm 0 0.351 14.13 0.79 134.7

3 2 2mm 45 0.355 13.97 0.71 130.3

4 4 2mm 40 0.311 15.94 0.69 126.6

5 6 2mm 35 0.378 13.11 0.75 119.8

Table 1.The Single jersey fabric’s specifications.

31

3.2 Preparing samples for seams displacement

For measuring seams displacement in fabrics, there are three famous standard tests which are

available. The IWS test method no.276 (IWS Test Method), British standard 2819 (British

standard), and ASTM D 3882-88 (ASTM standard). But in this project, for measuring spirality

angle degree of the seams displacement, another type of test was carried out.

For testing seams displacement in the knitted fabrics, for each fabrics specification, 4 samples

namely ‘‘F1a,F1b,F1c,F1d……., F5a,F5b,F5c,F5d’’, were cut into squares of 25x25 cm, where 3

of its sides were stitched and one side was left open. As cotton knitted fabrics becomes curly

when it is cut, so this becomes a problem when it comes to joining the two pieced together. Most

of the time the sizes of the samples were not the same, it was either reduced or increased. So a

square of 19.5x19.5 cm was marked on the fabrics with the point ‘A, B, C, D’. Furthermore, the

open pillow case samples were proceed further for wet relaxation treatments.

Figure 20. The pattern cutting plan for the pillow case samples.

25cm

50cm

19.5 x 19.5

32

3.3 Laundering and Tumble drying process

Washing and tumble drying are two means of relaxation in knitted fabrics. So it contributes lots

to the project work as the core of this project is to find the effect of machine parameters on

seams displacement and spirality. In this project work, a specific laundering regime with several

washing cycles was adopted for a better analysis in the angle of spirality. As Laundering with

laundry detergents and water followed by tumble drying was studied by (S.C.Anand et al.2002)

which were resulting in a high degrees of spirality in knitted fabrics, so this method will be

adopted. It relaxes the fabrics more which results into the course and the wales to be angularly

displaced. And it is better to use laundry detergent in the washing as at domestic level, people

often use these commercial products, so this will give us an overview about what effects it has on

the knitted fabrics.

The 20 open pillow case samples were subject to Laundering at 60° C which was the ideal

temperature for washing of cotton fabrics in the new automated Samsung domestic washing

machine at the university for 1 hour. The laundering process was like this, rinse, washes and

spins at 1200 Rpm. For the spinning process, there was an option to do it at 400 and 800 Rpm as

well but 1200Rpm was preferred as this would allowed a quicker tumble drying process. Overall

for all samples, 5 consecutive cycles of laundering were carried out as at industrial level, for a

fabric to be stable a minimum of 5 washing cycles is required, as this allow a maximum

distortion, after the 5 cycles, the size of the fabric will be stable.

3.3.1 Tumble drying process

After the 5 cycles of laundering, the samples were tumble dried in the ‘Hoover autosense Dryer’

at the university. Tumble drying was preferred over flat drying as in tumble drying there is

mechanical agitation which occurs and this contributes to the fact of spirality, and at industrial

levels this procedure of tumble drying is carried out as it is a time saving process of drying

fabrics as well and there is a control over the drying of the fabrics about how much we want the

fabrics to be dried but the fact that the tumble dryer at the university was an old machine and the

exact drying time was unknown so an exercise was carried out to find out the drying time of the

samples using hand feel description as we didn’t have any apparatus to find the moisture content

in the fabrics. In the first 30 minutes, the fabrics were allowed to dry, the after each 15 minutes,

the machine were stopped to find out the drying time over hand feel.

33

Table 2. Hand feels assessment of drying time taken by the Tumble drying machine.

Figure 21. Hoover autosense Tumble Drying machine at University of Mauritius.

Time(Minutes) Hand feel descript ion

30 The samples were not completely dry.

45 Compare to the previous hand feel, the samples

were damp dry st ill there were some moisture

remaining in it.

60 The samples were dried but the seams still

contain some moisture

75 The sample were fully dried

34

3.4 Measuring percentage of seams displacement in knitted fabrics

After the wet relaxation processes, the samples were being conditioned for 24 hours at the

temperature of 20±2° C, relative humidity 65±2% under the (ISO 139: 1973), then the seams

displacement were measured. The pillowcase bags were put flat on the table without applying

any stresses on it and the seams displacement is measured. The displacement from C to C' is

measured and the length of A to C'. The formulae: 100*(C'C/AC') was used to calculate the

percentage displacement due to spirality and if the angle of spirality of the seams displacement

were to be calculated, according to Pythagoras theorem of trigonometry, the formulae: Spirality

angle θ= tan-1

(C'C/AC'), can be used. The comparing results of % and degree will be the same.

Figure 22.Sample after washing where point C' is formed

Fabric number C'C in cm AC' in cm Spirality%

1 2.65 16.70 15.9

2 2.78 15.60 17.8

3 2.43 16.20 15.0

4 2.85 15.78 18.1

5 1.90 15.40 12.3

Table 3.The spirality % of the seams displacement.

35

Figure 23.A schematic diagram of the processes of the sample till measurement taking steps.

3.5 Measuring spirality angle in knitted fabrics by using digital

photography method

There are numerous ways of calculating the angle of spirality in knitted fabrics. One of the

mostly used is the British standard Bs 2819:1990 which was adopted by (Jiang Tao et al.1997) as

well as (V.K Kothari.2011) in which the courses are kept horizontally aligned and the angularly

displaced wales are marked then by using the Pythagoras theorem basis formulae, the angle is

calculated. However this conventional method of measuring the angle spirality demands lots of

precisions and as the displacement of loops and wales are so miniature, so a closer analysis must

be carried out.

Spirality in knitted fabrics occurs when the courses and the wales are angularly displaced from

each other, so to have a closer look at this displacement, the photography methods has been used

in this project by using a camera of 12 mega pixel with close up zoom and varying focal length

adjustments. This method of identifying spirality angle via image analysis has previously been

carried out by (Istanbul Technical University. July/September 2005) where the researchers have

scanned grayscale images of 256x256 pixel resolution.

36

So when the fabrics were scanned they get black parts which were covered by the overall fabrics

and white spots where the loops left a little light throughout the scanner (see figure 24). Each

black and white pixel in the image has a value and upon these values software was created so

that it can be identify where the white and black spots are located and within this identification,

the angle of spirality is measured automatically via the software. This technique was more

oriented on the pixels of the scanned image, in this project, jpeg digital images will be analysed

on the computer screen itself.

Figure 24. Logarithmic spectrum. Arrows indicate the lines in the horizontal and vertical where

the loops has left a little light passing through (Istanbul Technical University. July/September

2005:P.48, fig 2)

Proceeding further with the test method, the samples were separated into 2 batches of 2.2 meter

width and 1meter long in tubular form (measurement for 1 sample), where two types of

relaxation method has been carried out prior to the assessment of spirality angle in the fabrics.

One batch of grey knitted fabrics were left to relaxed for 24 hours under the temperature of

20±2° C and relative humidity 65±2% and the other batch was washed and tumble dried using

the same laundering and conditioning regime which has been carried out on the ‘seams

displacement test’.

37

3.5.1 Photographing the samples

After the preparation of the samples, the camera was fixed on a tripod and it was facing the

object (the sample) down at 90 degree. The distance between the camera and the object was

7.2cm at a focal length of F3.9,(see figure 25)

Figure 25. The digital camera placed on tripod facing the fabrics at 90 degree.

The fabrics was lied flat on the table without stretching it and creases was avoided so that a clear

flat image of the fabrics can be obtained, otherwise there would be error in the spirality angle.

Using the ‘rule of thirds’ grids of the camera, the wales of the fabrics were aligned with the grids

vertically (see figure 26).

The fabric in parallel

with the camera

lenses 7.2cm

38

Figure 26. The wales are align vertically with the grid

Photograph was taken on the fabrics at three different places because according to the structure

of a knitting machine, the take down tension is not similar in the tubular fabrics so photo was

taken on both sides of the fabrics and as well as in the middle ,see the figure below.

Figure 27.Places on the fabrics where photograph was taken for analyzing angle of spirality in

knitted fabric

Rule of thirds’

grid Wales aligned

vertically with the

grid

Length

Width

The fabric

Photograph taken at

three places on the

fabrics

39

3.5.2 Measuring the spirality angle using a digital screen protractor software

After the photograph was taken, it was processed through Photoshop software for image filtering

and then the image was bring onto paint where the angularly displayed courses were located and

marked using a red paint.

Figure 28.Marking of the courses

Then the wales were located vertically and a perpendicular line was drawn to it, see the screen

shot below.

Figure 29. Wales were located, perpendicular line drawn

Courses were marked

Wales

40

The spirality was measured using a digital screen protractor which were freely available online, see

figure 30.

Figure 30.The Digital screen protractor

The digital screen protractor is freeware software available online. It is downloaded and installed on the

computer hardware and this tool allows an easy measurement of any angle on the computer screen.

The software is very user friendly, for measuring the angles, it has to be place on the object and Red

stick see figure 30, is moved by the click and drag of the mouse and the angle degree or radians is

generated automatically on the grey display screen.

The protractor was placed over the perpendicular lines virtually on the computer ;( see figure 31) bellow

and the movable stick was aligned with the red marked courses ‘line on the picture and the

measurement was noted down.

Figure 31. Digital screen protractor placed on the marked wale line.

Movable stick, to

find the degree

The Grey Display

degree

The digital screen protractor was

placed to the perpendicular line

41

Table 4. The results for spirality angle before and after laundering

Fabrics no. sample spirality angle

before washing After washing

1 1 11.26 13.53

2 9.06 12.98

3 1.45 13.04

average

7.26

13.18

2 1 7.3 15.47

2 4.21 15.22

3 -3 14.94

3 1 10.73 16.04

2 7.07 17.06

3 2.33 16.8

6.71

16.63

4 1 8.02 16.65

2 7.44 21.54

3 2.97 17.73

5 1 0 17.8

2 4.47 19.28

3 8.46 20.04

4.31

19.04

42

Chapter 4: Analysis of findings

4.1 Stitch length of the circular knitted fabrics

The quality pulley wheel has been adjusted at different parameters by open the diameter of the

wheel. Below there is a table which shows the quality pulley adjustment, the tension adjustment

and the resulting stitch length , tightness factor and the GSM of the fabrics. For the analysis and

observational part, only 3 varying samples were taken as the progressing values were too close to

each other.

Fab

no.

Q.P meter

adjustment

Diameter of Q.P

wheel increased by

Central

stitch

adjustment

Stitch

length

Tightness

factor

g/m2

(GSM)

1 10 0mm 15 0.350 14.17 143.8

3 2 6mm 45 0.355 13.97 130.3

5 6 4mm 35 0.378 13.11 119.8

Table 5. The fabrics’ specifications

In table 5, it can be observed that as the quality pulley adjustment was opened by increasing its

diameter, the stitch length began to become bigger from fabrics 1 to fabrics 3 and at the same

time the tightness factor’s values decreases and the GSM of the fabrics decreases. This explains

that when the quality pulley wheel is increased in diameter, the loop length increases and as loop

length increases, the value of the tightness factor decreases.

When loops in a fabrics is big, so the fabrics should appears more slack, so it is in this case, the

fabrics were also assessed visually and is was observed that the fabric number 5 appears to be

more loosen than the fabric number 1. So when a fabric is loosen, its tightness factor value is low

and we said that the fabric is less tight and when the tightness factor value is high, we said that

the fabrics are very tight.

Commenting on the GSM of the fabrics, it is observed that when the stitch length is small, the

fabrics weights more and when the stitch length is high, the fabrics is lighter. This implies that

when the stitch length is small, more loops is being formed in 1 square meter of fabrics and more

yarn is being feed and it is different when the loops are big, there are less loops being formed in

1 meter square of fabrics and less yarn is being fed.

43

4.2 Relationships between Tightness factor and the angle of spirality in

knitted fabrics which has undergo wet relaxation processes.

Table 6.tighness factor v/s spirality angle of knitted fabrics before and after washing.

Chart 1. Relationship between tightness factor and spirality angle of wash and unwashed knitted

fabrics.

7.26 6.71

4.31

13.18

16.63

19.04

0

2

4

6

8

10

12

14

16

18

20

14.17 13.97 13.11

Before washing after washing

Average Spirality angle

Fabrics number Tightness factor Before washing after washing

1 14.17 7.26 13.18

3 13.97 6.71 16.63

5 13.11 4.31 19.04

Tightness factor

Spirality angle

44

The (Table 6) and the (bar chart 1) above show the average angle of spirality versus the tightness factor

of 3 different fabrics, fabrics 1, 3, 5 before washing as well as after washing and tumble drying. It

has been observed that while the value of the tightness factor was decreasing, in parallel the

angle of spirality for fabrics which has been undergoing the wet relaxation processes was

increasing, means that the courses and the wales where going more angular to each other as the

tightness factor of the knitted fabrics was decreasing.

Decreasing tightness factor means that the structure of the fabric is more loosen and the loops are

bigger as well as they are free to move among each other. When the loops are free to move, there

are residential torque which occurs within itself and this residential torque make the loops to

rotate. So the loops will be free to rotate inside the fabrics and while a loop is deforming,

unbalanced tension occurs in its two legs, as the leg and the head of loops are connected to each

other, so the legs will have a tendency to pull the head along with to an angle other than 90

degree and the fact that the fabrics structure is loosen(less tight) so there will be adequate space

for the deformation of the loops to occurs.

When the tightness factor is high, the angle of spirality decreases as the loops in the fabrics is

restricted from movement within the fabrics. The loops are blocked to each other and there are

no spaces between them, so they cannot move about. So there is a relationship between the

tightness factor and the spirality angle of washed and tumble dried fabrics as for the spirality to

occurs, it depends on how tight the fabric is.

45

4.2.1 Relationships between Tightness factor and the angle of spirality in

knitted fabrics which has undergo dry relaxation processes.

However the spirality trend for the unwashed knitted fabrics were different from that which has

been undergoing laundering processes. It can be clearly seen in the (bar chart 1) above that as the

tightness factor is decreasing, at the same time, the angle of spirality for the unwashed samples

are decreasing. The reasons for this was that to find the spirality angle for the dry relaxed fabrics,

the samples were taken at 3 different places on the fabrics (see figure 27) with varying tightness

factor for fabrics 1,3,4.

Figure 27.Places on the fabrics where photograph was taken for analyzing angle of spirality in

knitted fabric

So it has been observed that when the samples were taken at three different places of the tubular

fabrics, the spirality angle were varying at the 3 different places (see the graph below). From this

we can deduce that the take down tension of the knitting machines were not stable, at a certain

part of the fabrics, the tension was more or less a the tree different places and from this it can be

deduced that there is no relationship between tightness factor and spirality angle of dry relaxed

fabrics. The dry relaxed fabrics may have been relaxed for an extent but they are not fully

The fabric

Sample 1’s photo taken

here

Sample 2’s photo taken here

Sample 3’s photo taken here

46

relaxed as the fabric which has been undergoing wet relaxation processes. So relationship cannot

be established between a dry relaxed fabrics and the spirality angle.

Figure 32. Additional observation about Spirality angle at 3 different places on 3 different

fabrics

0

2

4

6

8

10

12

Fabrics 1 Fabrics 2 Fabrics 3

sample 1

Sample 2

Sample 3

Fabrics no. sample

spirality angle in degree

before washing

1 1 11.26

2 9.06

3 1.45

average 7.256666667

3 1 10.73

2 7.07

3 2.33

average 6.71

5 1 0

2 4.47

3 8.46

Average 4.31

47

4.3 Relationships between Tightness factor and the seams displacement

in knitted fabrics.

Chart 2. Tightness factor v/s seams displacement

Tightness factor vs. seams displacement

Fabrics number GSM(gram per square meter) Tightness factor

Average Seams displacement %

1 143.8 14.17(more tight) 15.9

3 130.3 13.97 15

5 119.8 13.11(less tight) 12.3

Table 7. Relationship between tightness factor and average seams displacement percentage with

including fabric weight.

14.17 13.97 13.11

15.9 15

12.3

Fabrics 1 Fabrics 3 fabrics 5

Tightness factor v/s Seams displacement

Tightness factor seams displacement

48

The bar chart above show the tightness factor against the seams displacement percentages. It can

be observed that as the tightness factor is decreasing, the percentage of seams displacement was

decreasing as well. This implies that as the structure of the fabrics is getting loosed, the seams

displacement is improving.

The possible reason for this could be the weight of the fabrics which is related with the fabrics

tightness. Previously it has been observed that when the fabrics tightness was decreasing, at the

same time the fabrics weight also was decreasing (see table 7) and upon this fact, it has been

derived that when a fabric tightness is less in a given meter square of fabrics the weight as well is

less and the loops are big and less yarn is being consumed and when a fabrics is more tight, its

weight is more and the loops are small as well as more yarn is being consumed in the production

of the fabric.

So upon these facts, it can be said that when there is more yarns in the knitted samples will cause

yarn torque which is caused by yarn twist liveliness. That is partially why tight fabrics which

consist of numerous loops results into higher percentage of seams displacement rather than a less

tight fabrics. The tight fabrics’ loops forced each other to go angularly which results into seams

displacement. Before going into depth of the subject about how tightness factor affects the seams

displacement, figure 33 show a schematic diagram of the root of the problem.

Figure 33. Schematic diagram showing the Root of the problem.

Tight Fabric

Weights more

More yarn consumption and Small loops

More yarn torque

Loose fabrics

Weights less

Less yarn consumption and Big loops

Less yarn torque

49

Furthermore, when spirality occurs in a fabric, the loops are free to move whether they are tight

or loose, but in a garment, the movement of loops is very different as the seams have an impact

on the displacement of the loops. When seams are added in fabrics, this seams seals the courses

across the fabrics (see figure 34) below.

Figure 34. loops of a loose fabric structure to the lefthandside and of a tight fabric structure to

the righthandside onto which seems were stitched.

Loosen loops more space in

between

Tight structure less space in

between

Seams

50

When the sample are washed and tumble dryed, the loops in the fabrics start to go anangular to

each other due to the residential torque which occurs in the yarns. So the loops in the loosen

structured sample takes the little space left between them while going anangular to each

other(see figure), the seams do not displace that much

Seams

Figure35. Low percentage of seams displacement in Loosen structure fabrics due to the

adequate spaces available then the loops are going unangular to each other.

Low percentage of Seams

displacement occurs

Empty space filled by loop displacement

Little Seams displacement

3-D view of the sample

51

But the loops in a tight structure have no place between them to move, so they force each other

and as the courses are blocked at the two sides as well, so this displaces the seams at greater

percentage.

Seams

Figure36. High percentage of seams displacement in tight structure fabrics due to the

unadequate spaces between the loops which forces each other when they go unangular to each

other.

Subsequently coming to the point, there is a relationship between the tightness factor and the

seams displacement. As the displacement of the seams it depends on how much tight the fabrics

are.

Each loop pulling each other

A high percentage of Seams

displacement occurs

3-D view of the sample

Seams displacement

greater than the above

sample

52

4.4 The relationship between the angle of spirality and seams

displacement

Chart 3. Spirality and v/s seams displacement

Spirality angle vs. seams displacement

Fabrics number Fabrics tightness Average Spirality

angle in Degree Average Seams displacement %

1 14.17 13.18 15.9

3 13.97 16.63 15

5 13.11 19.04 12.3

Table 8. Relationship between Spirality angle and seams displacement.

13.18

16.63

19.04

15.9 15

12.3

Fabrics 1 Fbarics 3 Fabrics 5

Spirality angle v/s Seams displacement

Spirality angle Seams displacement %

53

The average angle of spirality and the percentage of seams displacement is shown in the bar

chart(chart 3) diagram above. It was observed that the while the spirality angle was increasing at

the same time the % seams displacement was decreasing. According to some previous approved

researches about spirality in knitted fabrics, the results above should have been a reverse where

the spirality angle and the seams displacement should have been increasing in parallel but here

the when one variable is increasing the other is decreasing.

When a fabric is free in its tubular form, and when seams are added into it by cutting it into an

specific sample sized, the behaviors upon spirality which occurs into the 2 fabrics are different.

The seams displacement in a pillow case bag do happens due to the dislocation of the course and

wales from each other which spirality occurring in is knitted structure. So this spirality

phenomenon pulls the seams and twists it around the pillow case bag. Logically when spirality

will be high automatically the seams displacement should have been high as well but here it’s the

inverse.

This is because the loops behavior within a sample onto which seams has been added is different

from a sample onto which seams has not been done. In this case, the seams displacement do not

depends on the spirality angle of the fabrics. The seams displacement and the spirality angle is

rather dependent on the tightness factor of the fabrics but there is no direct connection between

the seams displacement and the angle of spirality.

54

Chapter 5: Conclusion & Recommendations

5.1 Conclusion

Coming to the end of this investigation, the relationship between tightness factor and spirality

angle of wet relaxed fabrics were corresponding to previous researches which has been made, so

we can deduce that tightness factor and spirality angle are connected since the beginning of the

phenomenon. But the connection between tightness factor and seams displacement was doubtful

as the results was inverse of what it should have been, but going through out the root of the yarn

and when it is in a cluster respecting a certain tightness, it was observed that the weight of the

fabrics could have been of the causes. Going more into the loops behavior of the fabrics, it was

observed that it might be different when seams are included into fabrics and when a fabric is

free, it is just like atoms between clusters, they can’t get out they have to react in between and it

is merely different when they are free to move. This also supports the fact that why there is no

relationship between seams displacement and spirality angle, because it is two different things,

and two different behaviors as well.

5.2 Recommendations

For shading light upon the subject studied and the analysis which has been made, more

investigation should be carried out so that we come to the root of the problem. Previously it has

been observed that when fabrics are less tight, the seams displacement was decreasing, so

investigation should be carried out to find out at what extent of fabric tightness the seams

displacement can vanish or diminish.

The fact that the test has been done upon a certain size of sample, in the future investigation the

sample size also must be varied to create an equation between fabrics tightness and the size of

fabrics upon which an amount of seams displacement occurs, in this way data will be tabulated

and the industries can use these data.

The relationship between the tightness factor and spirality angle was not consequent and the fact

that the relationship between the tightness of the fabrics and the spirality angle should have been

in parallel. Further investigation should be carried out upon the behaviors of the loops regarding

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spirality which occurs in a knitted fabric without seams and in knitted fabrics with seams. The

behavior of the loops as well must be taken into consideration.

The fact that it was observed that the take down tension was influencing the fabrics’ spirality, so

it would be a point to focus on. An investigation should be carried out about how to control the

take down tension.