Warp knitting - Raschel, made with latch needles

WARP KNITTING Raschel, made with latch needles, Tricot, using bearded needles... • More stable than knitted • Big and small holes are possible • Many designs are possible • Highly cour

WARP KNITTING

By Sunil Talekar, Student handout-SOFT -Pune

WARP KNITTING

Raschel, made with latch needles,

Tricot, using bearded needles.

• Warp sheet

• Loops development with the help of needles

• Loops insertion with the help of needles

• Needle movement controls mechanically and electronically

WORKING PRINCIPLE

• More stable than knitted

• Big and small holes are possible

• Many designs are possible

• Highly course yarn can be used

• Technical fabric can be produced

PROPERTIES OF WARP KNITTED FABRIC

• use to fulfill technical demands, like, filters, seat covers etc

• used as curtains, table covers

• used as chadar in some countries

• not used for clothing

USE OF WARP KNITTED FABRIC

7/26/15

WARP KNITTING

In this process;

• yarn sheet is developed (warp sheet)

• and then with the help of needles stitches are formed by,

• insertion new loop into old loop

THE PROPERTIES OF WARP KNITTED STRUCTURES

7/26/15

Warp knitting offers:

• Higher production rates than for weaving.

• A wide variety of fabric constructions

• Large working widths

• A low stress rate on the yarn that facilitates careful handling of fibres such as glass, aramide and

carbon (particularly when using weft-insertion techniques)

• Conventional warp knitted structures that can be directionally structured

• Three-dimensional structures that can be knitted on double needle bar raschels

WARP KNITTING MACHINE

WARP KNITTED FABRIC

WARP KNITTING TECHNOLOGY

• Warp knitting machines needles are mounted collectively and rigidly in a

horizontal metal bar (the needle bar that runs the full knitting width of the machine)

• Equally the yarn guides are also set rigidly into a horizontal metal bar (the

guide bar that runs the full width of the machine).

TRICOT KNITTING

Function of different parts of M/C:

1 Compound needle: In Tricot warp knitting m/c compound needle is used To form loop and produce the fabric is the main function of the needle

2 Needle bar: A needle bar is used in this m/c The main function of it is to hold the needles together and helps the needles to move unison while loop forming

3 Guide bar: Guide bar is used in this m/c to guide the yarn properly to the needle It feeds the yarn around the needle and controls the rate of warp feed from the warp beam by making lapping movement

TRICOT KNITTING

Function of different parts of M/C:

4 Sinker and Sinker bar: In the tricot warp knitting m/c tricot sinker is used to hold down the loops produced by the needles The sinker bar keeps the sinkers together to move unison while knitting The main function of the sinker is to hold down, knock over and supporting the fabric loops

5 Sliding latch: In warp knitting m/c compound needles are used A sliding latch is used here to close the hook while knitting

6 Sliding latch bar: In warp knitting m/c the sliding latches remain unison The latch bar keeps the latches together and helps it to move unison while knitting

7 Cloth roller: The produced fabric is wound on the cloth roller

TRICOT KNITTING

Function of different parts of M/C:

8 Let-off mechanism: The process of releasing the warp yarns according to the

requirement of the m/c and speed of cloth roller is the main function of let-off

mechanism

9 Take up mechanism: It helps the produced fabric to wound on the cloth roller in proper tension There are 3 take-up r/r in this m/c It also gives proper tension to the warp sheet and controls the speed of warp beam

11 Link: In the warp knitting m/c the link is used to make design in the knitted fabric The different links used here has different thickness and thus it helps to produce

design

TRICOT KNITTING

Function of different parts of M/C:

12 Pattern chain: The pattern chain is the chain of links joined with each other The pattern chain helps the m/c to produce design

13 Pattern drum: It is a drum, which gives motion to the pattern chain There are groove on it and the pattern chain is placed on it It gets motion from the m/c driving motor through gearing

14 Comb: In this warp knitting m/c the comb is used to separate the warp yarns

coming from the warp beam It works as the reeds of the weaving m/c and also

controls the fabric width

TRICOT KNITTING

Function of different parts of M/C:

15 Warp beam: In tricot warp knitting m/c warp beam is used to supply the warp

yarns parallely There are 8-warp beam in this m/c 4 beam are on the upper side and

4 are to the downside These beams are not so big as the weavers beam

16 Machine A/C: The m/c a/c is one kind of cooling device, which keeps the m/c parts and the motor from over heating and damage while running continuously

17 Main shaft: The main shaft of this m/c gives the m/c motion from the motor

TRICOT KNITTING

Function of different parts of M/C:

17 Lubrication: The m/c has automatic lubrication system

18 Controlling unit: The controlling unit is used to control the m/c easily It has a

digital control unit

19 Toothed belt: In this m/c the toothed belts are used to transfer motion without any slippage

Knitting Element Displacements

The diagram summarizes the

somewhat confusing

displacements made by the

guide bar The front of the

machine lies to the right of

the diagram.

Knitting Element Displacements

The diagram shows the individual

yarn guides set in a solid bar The

front-to-back movements are

called swings The first swing

from front to back is followed by

a lateral shog: the overlap, which

wraps the yarn in the needle

hook

Knitting Element Displacements

The next movement is a swing

from back to front followed by the

underlap that may be from 0 to 8

needle spaces depending on the

fabric structure being knitted.

TRICOT KNITTING

In diagram (1.3 a & b) the guide

bar swings from the front of the

machine (on the right hand side

of the diagram) to the back of the

machine taking the yarn through

the gap between two adjacent

needles.

TRICOT KNITTING

Diagram (1.4 c) shows the guide bar moving

laterally towards the observer

This is known as a shog movement, specifically the

overlap that wraps the yarn around the beard of

the needle.

Diagram (1.4 d) shows the second swing in the

cycle taking the yarn between adjacent needles

back to the front of the machine

At this time the needle bar moves upwards to

place the overlap below the open beard on the

shank of the needle.

Diagram (1.5 e) shows the presser bar

moving forward to close all the needles

and in (1.5 f) the closed needle passes

down through the old loop and the sinkers

move backwards to release the old loops

so that knock-over can take place.

TRICOT KNITTING

In figure (1.6 g) the sinker bar moves forward

to secure the fabric prior to the needle rising

in the next cycle and at this stage the guide bar makes a second shog, this time an overlap which may be of 0 to 8 needle spaces

depending on the structure being knitted.