WARP KNITTING

By Sunil Talekar, Student handout-SOFT -Pune

WARP KNITTING

Raschel, made with latch needles,

Tricot, using bearded needles.

WARP-KNITTING

When producing warp-knits, a yarn sheet is linked by stitches in longitudinal direction.

Thus, each individual thread in the sheet (warp) forms a wale

Main products • Nets• Curtains• Technical fabrics• Covers • Covering sheets

WARP KNITTING

• 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

04/10/2023

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

04/10/2023

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 KNITTINGFunction 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 KNITTINGFunction 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 KNITTINGFunction 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 KNITTINGFunction 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 KNITTINGFunction 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 DisplacementsThe 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 KNITTINGDiagram (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

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.