تکنولوژی دوزندگی - textile.yazd.ac.irtextile.yazd.ac.ir/ms.ahmadi/Downloads/Textile Technology/Textile... · Schematic of single rapier insertion. ... •weft knitting

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Textile Technology 341

Shuttle Weaving


AIR-JET WEAVING

The advantages of air-jet weaving machines are:• high productivity• low initial outlay• high filling insertion rates• simple operation and reduced hazard because of fewmoving parts• reduced space requirements• low noise and vibration levels• low spare parts requirement• reliability and minimum maintenance

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Three different systems have been used mainly oncommercial air-jet weaving machines:

1. Single nozzle, confusorguides and suction on the other side

2. Multiple nozzles with guides

3. Multiple nozzles with profiled reed

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Relay nozzles and profiled reed


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Projectile Weaving

The projectile weaving machines offer the followingadvantages:• low power consumption• reduced waste of filling material due to uniqueclean, tucked-in selvages• quick warp and style change• mechanical and operational reliability and ease of use• low spare parts requirement and easy maintenance• long machine life


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Schematic of mechanism before picking


Schematic of mechanism after picking

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Rapier Weaving

In this type of weaving, a flexible or rigid solid element, called rapier, is used to insert the filling yarn across the shed.

Rapier weaving machines can be two types:

1. Single rapier machines: A single, rigid rapier is used in these machines. The rigid rapier is a metal or composite bar usually with a circular cross section.


Schematic of single rapier insertion

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2. Double rapier machines: Two rapiers are used in these machines. One rapier, called the giver, takes the filling yarn from the yarn accumulator on one side of the weaving machine, brings it to the center of the machine and transfers it to the second rapierwhich is called the taker.

Double rapier machines can be rigid or flexible.


Schematic of Gabler systemSchematic of Dewas system

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In flexible rapier machines, the rapier has a tape like structure that can be wound on a drum. This saves space and allows narrower machine widths compared to double rigid machines.


Grippers

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Filling cutter

Operating sequence of insertion


Schematic of filling yarn transfer

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Knitting Technology

363Textile Technology

knitting classification

• knitting may be divided into two types

according to the formation method

• weft knitting and warp knitting

Warp knittingweft knitting 364Textile Technology

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Weft knitting

• The yarn is feed into the needle along the weft direction and knitted into fabric.


Warp knitting

• The yarn is feed into the needle along the warp direction and knitted into fabric.


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Knitted loop structure

• (1) Loop: The

simplest unit of

knitted structure. It

consists of needle

loop and sinker

loop. The needle

loop include a head and two side limbs.


Face loop stitch


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Reverse loop stitch


Course• A course is a predominantly horizontal row of loops

produced by adjacent needles during the same knitting cycle.

• In weft knitted fabrics a course is composed of yarn from a single supply.


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Wale• A wale is a predominantly vertical column of needle

loops produced by the same needle knitting at successive knitting cycles and thus intermeshing each new loop through the previous loop. In warp knitting a wale can be produced from the same yarn.


Stitch density

• (a) Wale density

• The wales in a centimeter or 5 centimeters or in an inch along the course.

• (b) Course density

• The course in a centimeter or 5 centimeters or in an inch along the course.

Textile Technology

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Stitch length

• The yarn length that form a loop.


Needle

• 1.6.1 Bearded needle

• There are six main parts of the bearded needle:

• 1-stem

• 2-head

• 3-beard

• 4-eye or groove

• 5-shank

• 6-tip


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Latch needle

• The latch needle has five main features:

• 1-stem

• 2-hook

• 3-latch

• 4-rivet

• 5-butt


Compound needle

• it include two separately parts:

1-the needle

• 2-the tongue (close member)


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Knitting Action of the Bearded Needle

• (1)Clearing：The old loop is cleared from the hook to the

stem below the tip of the beard.

• (2) Feeding: A new piece of yarn is fed onto the stem and

bringed into hook by the sinker wheel.

• (3) Closing: The presser presses the beard and the tip of

beard enter the eye cut in stem. The new yarn therefore is

enclosed by beard.


• (4) Landing: The old loop moves upwards and is located

on the outside of the beard as soon as the beard is closed.

• (5) Knocking-over and loop length formation: As the old

loop continues upwards the old loop slide off the needle

and the yarn is drawn through it forming a new loop.


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Knitting Action of the Latch Needle



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(1)Clearing

• As the needle move upwards along the clearing cam, the

old loop slide inside the hook and is cleared from the

hook and latch spoon on to the stem. At this point the

feeder guide plate acts as a guard to prevent the latch

from closing the empty hook.


(2) Yarn feeding and latch closing

• The needle starts to descent the stitch cam so that its latch

is below the verge with the old loop moving under it. At this

time the new yarn is fed through a hole in the feeder guide

to the descending needle hook. The old loop contacts the

underside of the latch causing it to close on to the hook.


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(3) Closing and landing:

• As the needle continues downwards the latch is forced

to close under the influence of the old loop. The old

loop is located on the outside of the closed latch.


(4) Knocking-over and loop length formation

• As the head of the needle descends below the top of the trick the old loop slides off the needle head draws the loop length, which is approximately twice the distance the head of the needle descends below the surface of the sinker or trick-plate supporting the sinker loop.


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Warp knitting

Weft knitting

Machine Gauge

• (1) The “machine gauge” is

determined as the number of needles in

one inch of needle bed i.e.2.54 cm.

• (2) Machine gauge influences choice

of yarn and count, and affects fabric

properties such as appearance and weight.


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• (3) Straight bar frame (bearded needle)

(Cotton machine)


Warp Knitting Machine

• (1) Raschel warp knitting machine


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• (2) Tricot warp knitting machine


Sketches of stitch


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Pattern grid

• In a squared paper, each square represents a needle or a stitch

and the different symbol in a square represents a different type

stitch. For example, an „X‟ symbol in a square can represent a

face loop, an „O‟ is a back loop. The means of a symbol can be

defined by you self according to the stitch what is knitted. The

„X‟ can also is a tuck loop or a loop knitted with a certain color

yarn etc.


Weft knitting thread path notation


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1.8.3 Warp Knitting Lapping Diagram


The four primary base weft knitted structures

There are four primary base structures:

• Plain

• Rib

• Interlock

• Purl

from which all weft-knitted fabrics are derived.


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2.1 Plain Fabric (single jersey)

• 2.1.1 The StructurePlain is produced by the needles knitting as a single set, drawing the loops away from the technical back and towards the technical face side of the fabric.

• It is the base structure of ladies‟hosiery, fully fashioned knitwear and single jersey fabrics.

• Plain is composed entirely of face loops (or entirely of back loops).

• Its basic structure unit is only one face loop (or one back loop).



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The characteristics

• (1) The appearance of the face and back differ

The technical face is smooth, with the side limbs of the

needle loops having the appearance of columns of Vs In

the wales.

• The technical back has an appearance of columns of

semi-circles formed by the heads of the needle loops and the bases of the sinker loops.


• (2) Extensibility widthwise is approximately

twice that of the length direction. it normally has

a potential recovery of 40 per cent in width after

stretching.

• (3) The edges of the fabric tend to curl or roll


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• (4) A run (collapse of a wale) will occur if a cut or

exposed loop is stressed. The direction of collapse can

be either from top to bottom or vice versa

• (5) The fabric can be unraveled, course by course from

the course knitted last or from the course knitted first

Textile Technology

• (6) The fabric thickness is approximately 2

times the diameter of the yarn used.

• (7) Plain is the simplest and most economical

weft knitted structure to produce and has the

maximum covering power.


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Rib Fabric• The Structure

• (1) Rib requires two sets of needles operating in between

each other so that wales of face stitches and wales of

reverse stitches are knitted on each side of the fabric.

• The simplest rib fabric is 1×1 rib. It consists of alternate

face and back wales, where a face wale is composed

entirely of face loops and a back wale is composed entirely of back loops.



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• (2) There is a range of rib set-outs apart from 1×1 rib,

the fist figure in the designation indicates the number of

adjacent plain wales and the second figure, the number

of adjacent rib wales.

• Single or simple ribs have more than one plain wale but

only one rib wale, such as 2×1,3×1,etc.

• Broad rib has a number of adjacent rib as well as plain

wales, such as 6×3 Derby Rib.


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The characteristics of 1×1rib

• (1) The appearance of the face and back

are identical (1×1rib, 2×2rib)

• (2) The extensibility of the fabric

widthwise is approximately twice that of

single jersey. The lengthwise extensibility

is essentially the same as in single jersey.

• (3) The fabric does not curl at the edges.



• (4) A run will develop in the fabric if an exposed

loop is cut, as is the case for single knits, except

that the direction of collapse will be from top to

bottom only.

• (5) The fabric can be unraveled course by course

but only from the end last knitted.


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• (6) The relaxed fabric is theoretically

twice as thick and half the width of an

equivalent single jersey fabric.

• (7) Particularly suitable for the extremities

of articles such as tops of socks, the cuffs

of sleeves, rib borders for garments, and

strapping for cardigans.


Rib knitting action


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Needle Timing

• Needle timing is the relationship between the

loop-forming positions of the dial and cylinder

needles measured as a distance in needles

between the two stitch cam knock-over points.

There are three kind of timing:

• (1)Synchronized timing

• (2)Delayed, rib, or interlock timing

• (3)Advanced timing



Synchronised timing

Delayed timing

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Interlock Fabric

The structure

• Interlock is composed of two 1×1 rib fabrics locked

together. It has the technical face of plain fabric on both

sides but its smooth surface cannot be stretched out to reveal the reverse loop wales.



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The characteristics• (1) the appearance of the face and back is the same

• (2) Extensibility widthwise and lengthwise are approximately the same as single jersey

• (3) The fabric does not curl at edges

• (4) A run will develop in the fabric the direction of which will be from the end last knitted. An interlock fabric will run less freely than single jersey or rib structure

• (5) The fabric can be unraveled from the end last knitted. Two yarns must be removed to unravel a complete knitted course

• (6) The thickness of the fabric is approximately twice that of single jersey

• (7) Interlock relaxes by about 30-40 percent


Knitting

• (1) Interlock gating. The needles in two beds must be exactly opposite to each other so only one of the two can knit at any feeder

• (2) Two separate cam systems in each bed, each controlling half the needles in an alternate sequence, one cam system controls knitting at one feeder and the other at the next feeder

• (3) The needles are set out alternately; one controlled from one cam system the next from the other, diagonal and not opposite needles in each bed knit together

• (4) The the conventional interlock machine has needles of two different lengths, long needles knit in one cam-track and short needles knit in a track nearer to the needle heads.


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Purl Fabrics

The Structure• Purl structures have one or more wales which contain

both face and reverse loops. The semi-circles of the

needle and sinker loops produced by the reverse loop

intermeshing tend to be prominent on both sides of the structure.



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The Characteristics of 1×1Purl fabric

• (1) Same appearance,face and back (similar to the back of single jersey).

• (2) Highly extensible in all directions. Approximately twice as extensible as single jersey in the length direction.

• (3) The fabric does not curl at the edges.

• (4) The fabric will run in the wale direction starting from either end.

• (5) The fabric may be unraveled course by course starting from either end.

• (6) The fabric tends to be two or three times thicker than single jersey.


Documents

تکنولوژی دوزندگی - textile.yazd.ac.irtextile.yazd.ac.ir/ms.ahmadi/Downloads/Textile Technology/Textile... · Schematic of single rapier insertion. ... •weft knitting