Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
WEFT KNITTING
1. INTRODUCTION
Knitting is the method of manufacturing fabric by means of intermeshing of yarns by
looping. Loops are formed by needle action while a loop is taken through one more loops and the
stitch is produced. Loops / Stitches possibly created in a horizontal direction or in vertical
direction. Horizontal direction of loop formation is called weft knitting and vertical direction of
loop formation is called warp knitting, both are the main classifications of knitting technology.
2. WEFT KNITTING
A weft knitted fabric contains horizontal / parallel row of courses of yarn are knitted. It
requires just a single yarn to form a fabric but more number of yarns is fed with respect to
machine capacity. Weft knitted fabrics is used widely in the clothing industry for example
hosiery, sweaters, foundation garments and active wear. The most important benefit of weft
knitted fabric is its construction techniques. The fabric is capability to stretch and recover thus
match to body shape. To achieve a desired fabric performance properties, the selection of
suitable fibers and yarns are taken on to consideration.
3. CLASSIFICATION OF WEFT KNITTING
Figure 1 clearly shows the classification of weft knitting based on the machine frame,
needle and fabric produced.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
Fig. 1. Classification of weft knitting
The following points are taken consideration in the weft knitting classification based on the
different approaches.
Machine frame and needle bed arrangement
• Circular knitting
• Flat knitting
Number of needle bed
• Single jersey
• Double jersey
End product
• Fabric machine
• Garment machine
Basic fabric structure
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
• Single jersey or plain
• Rib
• Interlock
• Purl
Type of needle used
• By using latch needle
1. Circular knitting
2. Flat bed knitting
• By using spring bearded needle
1. Circular knitting
2. Straight bar knitting
4. KNITTING ELEMENTS
A knitting machine is an equipment for converting yarn into knitted loop structures by
means of mechanical moving parts either manual or power operated. These mechanical or electro
mechanical parts are called as knitting elements to convert yarn into knitted fabric. Circular
knitting machines elements are possibly divided into:
• Primary knitting elements
• Secondary knitting elements
The primary knitting elements are actually forming the stitches by means of needles and
sinkers. The secondary knitting elements are activating the needles and sinkers. Such knitting
elements are cylinder, dial, cams, and pattern wheels. Expect dial, remaining all the knitting
elements are common to all kind of weft knitting machine and dial is used only in double jersey
knitting machine.
4.1 Needles
Needle is the primary element of the knitting machine and it is a hooked metal piece. The
knitting needle gets the yarn from the yarn feeder and converts in to a knitted loop. This loop is
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
enclosed in the hook and finally drawn through the old loop. The needle has to rise from the
normal position to clear already held loop and to collect the new loop from the feeder. The new
feed yarn form a loop in the needle hook since the needle starts to slide down to retain the new
loop and to knock off the old loop. For that reason all needles should have various methods of
closing and opening the needle hook to keep hold of the new loop and leave out the old loop. As
a result, needles are classified in to three types shown in figure 2.
• The latch needle,
• The spring-beard needle and
• The compound needle
Fig 2. Three main types of knitting needle
The needle parts can be divided into four main parts:
o The hook - This receives and retains the thread to be looped.
o The hook opening and closing device - It permits the hook to get a new yarn and
release the old loop.
o The but - This is inserted with CAM system to lift and descend the needle for loop
formation.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
o The stem - A system allowing the loop to slide on its surface ant the of needle
move up and down.
The spring beard needle
The needle is a shape of round wire stem with a beard hook end. Opposite the point of the
beard, there is a groove in the shank which permits the needle eye / point forced by auxiliary
mechanism to close the needle hook. The spring beard needle needed an auxiliary mechanism i.e.
presser to seal the needle hook. The opposite end of the needle is equipped with but to raise and
move down the needle for knitting action.
The latch needle
Latch needle is called as self acting needle. This type is shaped into flattened wire shank
with a latched hook end. The latch swings by the rivet and close the tip of the hook. But is placed
in the opposite end of the needle and inserted with CAM to move up and down. There is no
auxiliary device is required to form a loop.
The compound needles
The compound needle has the advantages of both the bearded and latch needles. It
consists of two individually controlled parts i.e. shank and tongue. Both part of the compound
needle required independent and precise control system. This system is not a key trouble in warp
knitting because all the needles activated together. However in weft knitting, it may create
problems at the time of loop formation.
4.2 Sinker
The sinker is a thin metal piece of material which is arranged between the needles and it
is a second primary knitting element. During the loop formation, sinker moving at right angles
(forward and backward) to the needles by the special sinker CAM and executes one or more of
the following operations.
Help for loop formation - Sinker is to go under the surface and bend the newly laid yarn
into a loop
Holding down - Sinker hold down the old loops at a lower level on the needle stems
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
Knocking over - Sinker upper surface or belly supports the old loop as the new loop is
drawn through it.
Fig 3. Sinker
In figure 3 clearly show the sinker, it has an exclusive shape and size. The upper section
of the sinker is called the nose and lower one is the breast.
4.3 CAMs
A device which can convert the rotary force into a suitable reciprocating movement is
called as CAM. The reciprocating action of knitting needles and sinkers are independently
controlled by knitting cams.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
Fig 4. Knitting CAM
Conventional knitting machines cams are mostly single track cam to produce only the
basic knitted structures. Further increasing the complexity of knitted structure, multiple cam
tracks are needed for the each set of needle movement. The cams are employed either
independently or in a unit form of cam system and it depends upon the design of machine.
Separate cam systems are necessary for each yarn feeder to receive the yarn by the needle. In a
cam system various sections are available to control the needle movement and it shown in figure
4.
The functions of cams in a cam system
a. Guard cams To define a boundary to the movement of buts and to prevent knitting needles
falling out from the track.
b. Raising or
Clearing cam
To lift the needles in a different heights according to the fabric structure
requirement.
c. Stitch cam
• To control the yarn length to form needle loop by controlling the
descending movement of the needle.
• At the same time, it functions as a knock-over cam.
d. Up throw Cam To obtain the needles to return back to the relaxed position.
e. Running Cam The needles from the relaxed place to a knitting cycle to create new loops.
4.4 Cylinder
Cylinder is a metal plate which acts as a needle bed to support and hold the needles in the
knitting action. Outside wall of the cylinder made up of tricks are cuts. Figure 5 shows that the
needles that are placed into each trick and the arrangement of needles are depend upon the design
features of the knitted structure. The but protrudes from the needles and needles are arranged
perfectly vertical. This protruded but travels along the cam track, which provides the preferred
movement to the needle.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
Fig 5. Cylinder
4.5 Dial
Dial is a metal plate placed perpendicular to cylinder which acts as a needle bed to
support and hold the horizontal needles in the knitting action. Like cylinder, outside wall of the
dial made up of tricks are cuts. Dial is the main knitting element in double jersey knitting
machine
5. CIRCULAR WEFT KNITTING MACHINES
Circular weft knitting is a predominant knitting machine producing verities of knitted
fabrics according to the applications. It produces tubular knitted fabric with the help of
mechanical or electro mechanical components. It can be classified in two types based on the
number of needle bed. First one is single jersey knitting machine used one set of vertical needle
produces plain knitted fabric and its derivates. The second one is double jersey knitting machine
used two set of needles (vertical and horizontal) to produce rib and interlock fabrics.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
5.1 Single Jersey Knitting Machine
In single jersey circular knitting machine, the needles are placed in a vertical groove on
the surface of the cylinder. The cylinder needle buts are protruding into a cam track which is
provides reciprocating movement to the needles. The machine function can be divided into
different zone i.e. creel zone, knitting zone and take down zone. The creel zone consists of
creels, thread guide, tensioner, stop motion, feeders and yarn monitoring devices. The knitting
zone consists of primary and secondary knitting elements. The take down zone has spreader and
take up mechanism. The supply package cone is converted into knitted fabric and produced in
tube form.
Three stronger cast iron legs are provided to hold all the parts and components of knitting
machine and it anchor on the floor. A heavy duty motor is used to drive the cylinder and the
necessary parts of a knitting machine.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
Fig 6. Circular weft knitting machine
Passage of yarn
The supply package is cone, placed on the creel and the yarn is unwound than passed
through the thread guides and top stop motion. Different stages of stop motions are used to stop
the machine immediately to avoid the major defect. Subsequent to that, the yarn passes through
the middle stop motion and tensioners. The positive yarn feeding system is placed in between the
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
stop motion to feed the yarn positively. This positive feeder may be a storage feeder that
unwound the supply yarn from the creel continuously and carry the thread in an uniform tension.
From the positive feeder, the yarn feed to the knitting zone in a constant rate and feed yarn
tension is maintained. The knitting elements in a knitting zone begin to knit a fabric. The knitting
needle raise and descent to form a loop and this process is supported by remaining knitting
elements. After that the knitted fabrics is taken down in inside of the cylinder through take-up
mechanism and finally wound on the fabric roller without loop distortion and creases. Before
wound the tubular fabric on the cloth roller, the spreader is used to maintain the diameter of the
knitted fabric and spreader positioned inside the tube of knitted fabric. The cloth roller is
collected at the bottom of the circular weft knitting machine.
5.2 Double Jersey Knitting Machine
The basic principles of loop formation in double jersey knitting machine is same as single
jersey knitting machine. Here the machine equipped with two set of needle, one is cylinder
needle (vertical) and another one is dial needle (horizontal). Both are combined together to form
a knitted loop structure. The arrangement of needle in cylinder and dial in a machine decide the
type of fabric produced. Rib and interlock can be manufacture through double jersey knitting
machine.
1. Rib Knitting Machine
Rib knitted fabric has a vertical cord like appearance for the reason that loops in wales
direction form face loop and reverse alternatively or vice-versa. In rib knitted fabric
manufacturing, two sets of needles are alternately used and it arranged in a set or gaited between
each other. In rib gaiting, the needles are arrangements in the cylinder are between the needles of
the dial it shown in figure 7.
The knitting action:
Clearing. The cylinder needles and dial needles move to clear the old loops formed in the
earlier cycle.
Yarn Feeding. The needles are reserved and the open latches cover the old loops, new
yarn is supplied into the needle hooks portion.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
Knocking-over. The needles are reserved in action the old loops are knocking over and
the fresh loops are hanged through them.
Fig. 7 Rib knitting machine needle arrangement
2. Interlock knitting machine
Interlock knitted fabrics is produced mostly on particular type of cylinder and dial
circular machines with two different heights of needles. To produce interlock fabric, the entire
course involves two feeder courses systems. While considering the feeders individually, every
feed yarn knits on alternate needles (either long needle or short needle) to its corresponding
cylinder and dial to manufacturing two 1 x 1 rib structures.
At first, the interlock machine has two different needles height i.e. long and short needles
for both cylinder and dial. The arrangement of interlock needle gaiting is long needle in cylinder
exactly facing at right angles to short needle in dial and vice-versa. To construct this knitted
structure, two individual cam tracks used to controlling the long and short needles in the cylinder
and the same type of setup is applicable for dial.
In figure 8 shows that the odd yarn knit with the long needles of cylinder and dial
produces first alternate wales and the even feeders yarn knit with short needles of cylinder and
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
dial produces second alternate wales. While considering this structure individually it is 1 x 1 rib
structures. But in combine together the operation of all the feeders and needles in interlock
machine produces interlock structure. Here the appearance of fabric on both face and back are
reflecting same structure.
Fig. 8 Rib knitting machine needle arrangement
6. BASIC WEFT KNIT STRUCTURES
Weft knitted structures is manufactured either by means of circular or by flat knitting
machine. In both the knitting systems, knitted fabrics are produced by looping the feed yarn in a
horizontal / course wise direction to the width of cloth. Here the horizontal loops (courses),
vertical loops (wales), face loop and back loop are called the major deciding factor for the basic
weft knitted structures. The following four weft knitted structures are taken as primary / basic
parental structures.
• Plain structure (Single jersey)
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
• Rib structure
• Interlock structure
• Purl structure
1. Plain structure
It is known as single knit structure or single jersey.
Produced by means of single set of needles.
Two type of structure can be possible i.e. technical face (face loop) and technical back
(back loop).
Technical face - Loops are formed by drawing the new loops through the old loop at front
and the food of new loop is cover the head of old loop showing the appearance of ‘V’s
columns in the wales direction (figure 9).
Technical back - The new loops are formed under the old loop and the foot of the new
loop is covered by head of old loop showing the appearance of inverted ‘U’s rows in the
course direction.
Plain structure weft knitted fabric (single jersey) produced with face loop stitches on the
fabric face side and back loop stitches on fabric backside.
Fig. 9 Plain knit face loop structure
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
2. Rib structure
• Rib knitted structure is one of the double jersey knitted fabrics manufactured with
alternate face wales and back wales or vice-versa by means of cylinder and dial.
• In figure 10 shows, that the fabric produced with face loop and back loop alternatively in
wales direction shows vertical stripped appearance on either side of fabric.
• Because of the same appearance on face and back of the fabric, it is a reversible knitted
structure.
• 1x1, 2x2, 3x3 are called balanced rib knitted structures. Unbalanced rib structure can be
produced with small modification in knitting needle lifting action.
Fig. 10 1 x 1 Rib structure
3. Interlock structure
• Interlock knitted structure can be produced by a special arrangement in the knitting
needle and knitting action. It was initially derived from rib knitted structure.
• In figure 11, ‘A’ represent first 1x1 rib structure and ‘B’ shows the second 1x1 rib
structure. With meshing of two 1 x 1 rib knitted structure produces regular interlock
structure.
• By hiding the look of the reverse loops through knitting process, each side of the fabric
shows only face loop.
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
Fig. 11 Interlock structure
4. Purl structure
Purl is a special kind of structure producing special knitting machine. Two cylinder
knitting machine is used with two hook end needs. Latch needle is the most convenient
double-ended needle for the manufacturing of purl structure.
Loops are formed by alternate face courses and back courses or vice-versa by means of
two cylinders (figure 12).
Fig. 12 Purl structure
Paper Code and Title: H08TM Textile Manufacturing and Testing
Module Code and Title: H08TM15 Weft Knitting
Name of the Content Writer: T. Palani Rajan
6.1 Characteristics Basic Weft Knitted Structure
CHARACTERISTICS SINGLE JERSEY 1 X 1 RIB INTERLOCK 1 X 1 PURL
APPEARANCE Face and back differ. Face and back are
identical.
Face and back are
identical.
Face and back are
identical.
EXTENSIBILITY
Twice extension on
widthwise than the
length direction.
Twice extension
on widthwise than
the single jersey.
Lengthwise is
same as single
jersey.
Twice extension on
widthwise than the
single jersey. More
rigid than single
jersey.
Twice extension on
lengthwise than the
length direction.
CURL (OR) ROLL Fabric edges will
tend to curl or roll
Does not curl Does not curl Does not curl
UNRAVEL
From either end,
unraveled course by
course
Only from the last
course, unraveled
course by course.
Two feed yarns
must be unravel to
complete knitted
course.
From either end,
unraveled course
by course
FABRIC
THICKNESS
Twice of feed yarn
diameter.
Twice of single
jersey fabric.
Twice of single
jersey fabric.
Twice of single
jersey fabric.