Txl131 Lectures
Txl131 Lectures
Txl131 Lectures
Weaving
Knitting
Non-woven
Braiding
Woven
Knitted
Nonwoven
Braided
Figure 1.1 depicts the fabrics produced by the four major technologies. Fabric manufacturing
may be preceded either by fibre production (in case of nonwoven) or by yarn manufacturing (in
case of weaving, knitting and braiding). Fabrics intended for apparel use must fulfill
multidimensional quality requirements in terms of drape, handle, crease recovery, tear strength,
air permeability, thermal resistance, moisture vapour permeability. However, looking at the
versatility of textile fabrics, it is now being used in various technical applications where the
requirements are altogether different. Some examples are given in Table 1.1.
Fabric type
Filter fabric
Weaving
Weaving is the most popular way of fabric manufacturing. It is primarily done by interlacing two
orthogonal sets (warp and weft) of yarns in a regular and recurring pattern. Actual weaving
process is preceded by yarn preparation processes namely winding, warping, sizing, drawing and
denting.
Winding converts the smaller ringframe packages to bigger cheeses and cones. Pirn winding is
performed to supply the weft yarns in shuttle looms. Warping is done with the objective to
prepare a warpers beam which contains a large number of ends in a double flanged beam. Sizing
is the process of applying a protective coating on the warp yarns so that they can withstand
repeated stresses, strains and flexing during the weaving process.
Primary Motions:
For fabric formation in weaving, three primary motions are required namely shedding, picking and
beat up.
Shedding
It is the process by which the warp sheet is divided into two groups so that a clear passage is
created for the weft yarn or weft carrying device to pass through it. One group of yarns (red
yarns) either moves in the upward direction or stay in the up position (if they are already in up
position) as shown in Figure 1.2. Thus they form the top shed layer. Another group of yarns
(green yarns) either moves in the downward direction or stay in the bottom position (if they are
already in bottom position). Thus they form the bottom shed layer.
Except for jacquard shedding, warp yarns are not controlled individually during the shedding
operation. Healds are used to control a large number of warp yarns. The upward and downward
movements are controlled either by cam or bobby shedding mechanisms. The movement of the
healds is not continuous. After reaching the up or bottom position, the healds, in general, remain
stationary for some duration. This is known as dwell. In general, the shed changes after every
pick i.e. the insertion of weft.
Picking
The insertion of weft or weft carrying device (shuttle , projectile or rapier) through the shed is
known as picking. Based on picking device, looms can be classified as follows.
With the exception of shuttle loom, weft is always inserted from only one side of the loom. The
timing of picking is extremely important specially in case of shuttle loom. The shuttle should enter
into the shed and leave the shed when the shed is sufficiently open. Otherwise, the movement of
the shuttle will be obstructed by the warp yarns. As a result, the warp threads may break due to
abrasion.
Beat up
Beat up is the action by which the newly inserted weft yarn is pushed up to the cloth fell (Figure
1.4). Cloth fell is the boundary up to which the fabric has been woven. The loom component
responsible for the beat up is called reed. The reed is carried by sley which sways forward and
backwards due to the crank-connecting rod mechanism. This is known as crank beat up. In
modern looms, beat up is done by cam mechanism which is known as cam beat up. Generally, one
beat up is done after the insertion of one pick.
after the beat up. The take up speed also determines the picks/cm value in the fabric at loom
state. As the take up motion winds the newly formed fabric, tension in the warp sheet increases.
To compensate this, the weavers beam is rotated by the let off mechanism so that some new warp
sheet is released.
Auxiliary motions:
Auxiliary motions are mainly related to the activation stop motions in case of any malfunctioning
like warp breakage, weft breakage or shuttle trapping within the shed. The major auxiliary
motions are as follows:
Now, for cotton yarns, having packing factor of 0.6, the relationship between yarn diameter (inch)
and yarn count (Ne) is as follows:
d=1/28Ne
The relationship between end spacing (p ) and ends per inch (n ) is as follows:
1
n =1/p
1
k = n / 28Ne
1
Fabric cover is a very important parameter as it influences the following properties of the woven
fabrics.
Air permeability
Areal density : It is expressed by measuring the mass of the fabric per unit area. In most of the
cases the mass is expressed in gram (g) and area is expressed in square meter (m ). Therefore,
the unit becomes g/m which is popularly called as GSM. Areal density of fabric will depend on the
following parameters.
2
Crimp% in warp
Crimp% in weft
Web formation
Web bonding
Needle punching
Hydro-entanglement
Thermal bonding
Chemical bonding
Needle-punching Technology
Needle punching is the method of consolidation of webs by the repeated insertion of barbed needles into the
fibrous web as shown in Figure 1.5. This process consolidates the structure of fibrous web without any binder by
interlocking of fibres in the third or Z dimension. Continuous filaments or short staple fibres are initially arranged
in the form of a fibrous web in various orientations (random, cross, parallel, or composite). This forms a threedimensional intermingled structure which fulfils the necessary requirements of geotextiles.
Needle punched nonwoven geotextiles are extensively used in civil engineering applications including road and
railway construction, landfills, land reclamation and slope stabilization. Such applications require geotextiles to
perform more than one function including filtration, drainage, and separation. The properties of needle punched
nonwoven depend on parameters like Fibre type, web aerial density, needle penetration depth, punch density and
number of needling passages.
Hydroentangled nonwoven structures have an extensive range of applications like wipes, carpet backing, filters,
sanitary, medical dressings and composites. Among these applications, personal care and household wipes form the
fastest growing market.
Spun-bonding Technology
In spun-bonding process, fluid polymer is converted into finished fabric by a series of continuous operations.
Polymer is first extruded into filaments and then the filaments are attenuated. While the filaments are being
attenuated, they remain under tension. After attenuation, the tension is released and the filaments are forwarded
to a surface where the web is formed. The web is then subjected to the bonding process which can be done by
chemical and/or thermal process. A binder may be incorporated in the spinning process or applied subsequently
(e.g., a latex). Extensive experimental investigations also have been made for the production of spun bonded
nonwovens made of hollow filaments using polymers like Polypropylene, Metallocene Polypropylene and polyester.
Warp knitting a method in which the loops made from each warp thread are formed along the length of the
fabric. (Figure 1.9b)
Hook
Latch
Latch spoon
Stem
Butt
Hook is the curved part of the needle which is responsible for forming the loop. Latch is a tiny component and
it is riveted on the upper part of the stem of the needle. Latch spoon is the tip of the latch which touches the
tip of the hook when the former closes. The butt is actually the follower and it is pressed against the cam to
cause movement of the needle. The movement of the needle is caused by a set of cams.
The sequence of loop formation has been explained in Figure 1.11. When the needle moves up, the old loop
forces the latch open. When the old loop rests on the latch, the position is called tuck. The needle moves up
further and the old loop comes out of the latch. This is called the clearing. Then the needle starts to descend
and the hook catches the yarn. The old loop now helps to close the latch so that newly formed loop is caught
between the hook and latch. The needle continues to descend and new loop is cast off through the old one.
Course and wale: The horizontal row of loops is called course. The vertical column of loops is called wale
(Figure 1.12).
Flat bed machines, as the name implies, have one or two beds to carry the needles. Single bed machines
produce plain or single jersey structure where as double bed machines (V bed) produce double jersey
structures (Figure 1.13). The needles on the two beds in a double bed machine must be offset so that they
do not collide with each other while forming the loop.
In case of single jersey fabrics, all the heads of the loops are either facing or away from the viewer. In case of
double jersey fabrics, in some of the wales, heads of the loops are facing the viewer and vice versa. Single
jersey fabrics tend to curl at the edges. If the machine gauge (number of needles/inch) and yarn count is
same, then double jersey fabric is thicker and more stretchable in course direction than the single jersey
fabric.
In circular bed machines, two sets of needles namely cylinder and dial needles are used. They operate
perpendicularly to each other. One set of needles (cylinder needles) are arranged on a grooved cylinder.
Generally the cylinder is rotated and needles get the requisite movement from stationary cam jackets.
Another set of needles operate in horizontal plane and they are known as dial needles.
Another important knitted fabric structure which is made on circular machines is known as interlock which is
basically the combination of two rib structures (Figure 1.14). The overlapping of two rib structure is
responsible for lower stretchability of interlock fabrics as compared to the original rib structure. Interlock
fabrics are generally heavy and demonstrate least porosity among the three knitted structures
2. Winding 1
2.1 Objectives of winding
Objectives:
To wrap the forming yarn
on a package in a
systematic manner or to
transfer yarn from one
supply package to
another in such a way
that the latter is
adequately compact and
usable for the
subsequent operations.
To remove the
objectionable faults
present in original yarns.
Over end
withdrawal
Side withdrawal