Chapter Ten Jacquard Fabrics

� 10.1 Elements of Jacquard Shedding

� 10.2 Preparation for Designing the Jacquard

Fabrics

� 10.3 Steps in construction of Jacquard Design

Jacquard Fabric sample:

Jacquard Fabric sample:

10.1 Elements of Jacquard Shedding

� Introduction:

To weave a fabric on loom, forming a shed is necessary. The tappet shedding is the simplest one. It can be used to weave plain, twill etc. Later, the dobby was invented. It can be used to weave more complicated weaves, such as diamond, diaper and some compound weaves.

� But dobby shedding can not fit the requirement of large

pattern which need not only a small group warp threads

lifting in same way, but also the single thread lifting as

well. See Fig. above. So another loom is to be created to

satisfy the demand.

2. Jacquard machine and Jacquard shedding

1: hooks

2: knife

3:knife frame

4: neck cord

5: rod

6: grade

7: horizontal needle

8: needle broad

9: cylinder

10: spring box

11: spring

12: card Fig. 10.1

The principles of the Jacquard shedding are described as below: (flash)

� The warp threads are lifted by hooks 1, which

are arranged in rows.

� The hook is made of wire. The top bent part of

hook can be engaged by the knife 2.

� The knives are mounted in the knife frame 3,

which reciprocates vertically once every pick.

� Each hook is connected with horizontal needle 7,

which can deviate the hook to the left.

� The right-hand ends of the needles protrude at the side of the machine, passing through the holes of needle board 8, which holds the ends of the needles in the proper position against the holes of cylinder 9. The left-hand end of the needles is positioned in the spring box 10. The spring 11 is intended to return the needle to initial position after the needle has been deviated by the card 12.

� If there is no hole in the card against the needle, the card presses the needle, moves the needle and shifting the hook to the left. The hook will not be engaged by the lifting knife. The warp thread remains in the lower position, forming the bottom part of the shed.

� If there is a hole in the card opposite the needle, it is not

deflected. The hook remains over the knife and at the next

moment, the knife grasps it while going up, and lifts it. As

a result, the harness cord and the warp thread are lifted.

The warp thread forms the top part of the shed.

� The number of holes in the card determines the number of

warp threads to be lifted in the particular shed, when this

card operates.

� And the number of cards in the chain equals the number

of weft threads in the repeat.

10.2 Preparation for Designing the Jacquard Fabrics

1. Calculate the repeats

� The warp repeat of the weave can be obtained

by multiplying the warp density by the width of

the pattern, and the weft repeat can be reached

in the same way.

� Warp repeat RO = warp density × width of the pattern

� The total number of hooks should be equal to or more

than the warp repeat.

� Weft repeat Ry = weft density × length of the pattern

� One weft thread corresponds with one card.

2. Select the design paper

� A design paper is characterized by the count,

which is a ratio of vertical spaces to horizontal

ones in each block. In order to retain correct

proportions and shapes of figure designs, the

ratio of vertical spaces to horizontal ones should

be equal to the ratio of warp density to the weft

density in the finished fabric.

� Count of design paper can be calculated by the formula:

Where: a = number of vertical spaces in the block, which is usually assumed equal to the number of hooks in short row of Jacquard machine;

b = number of horizontal spaces in the block;

PO = warp density of the finished fabric;

Py = weft density of the fabric.

O

y

Pab P=

� Next step is to find the number of blocks, which in

horizontal direction is calculated by the formula:

Where: RO is the warp repeat of the Jacquard weave.

OR

Ma

=

� The number of blocks in vertical direction is calculated

in the similar way:

Where: Ry is the weft repeat of the weave.

� The total number of block is .

� The purpose for selecting design paper is to retain

correct proportions and shapes of figure designs

NM ×

yRNb

=

Different design papers are shown below:

8/8 8/10 8/12

8/13 8/16

One block of the design paper:

10.3 Steps in construction of Jacquard Design

Studio techniques/conventional system.

Ⅰ. Designer: creating new ranges, pattern

sketches

Ⅱ. Drafter: transferring sketch on to point

paper complete with structure

Ⅲ. Cutter: semi-mechanical cutting methods,

reading in weave structure from point paper.

Ⅰ.The first step

� The first step is to draw the picture or to copy it from the art book or

any other source. A copy can be made by using the tracing paper.

The figure of any shape can be chosen, and as an example of figure

the flower has been chosen, which is shown at A in Fig. 10.3.

The picture should be divided by vertical lines into a certain

number of spaces equal to the number of blocks in

horizontal direction of the design paper, which have been

calculated before constructing the design.

Ⅱ. The second step

� The second step is to transfer the outline of the figure

from tracing paper to design paper. It can be done easily,

since the number of squares of the tracing paper equals

the number of blocks of the design paper. See Fig. B at

next page:

Ⅲ. Cutter:

� Before cutting, the type of weave for the

figure and the ground should be chosen.

� For this example at B in Fig.10.3 B plain

weave is chosen for the figure, and twill l/7

for the ground.

The 17th and 92nd horizontal space are cut as below:

2: Electronic data processing system

Fig.10.4 Construction of jacquard design by electronic way

� In jacquard weaving, computer technology is now

successfully employed.

� Designer: creating new ranges. Pattern sketches or designs

can be either created on the color monitor or images from

any media can be scanned into the system.

� Programmer: structures added, exchanged, repeated, re-

scaled, contours adjusted. The information is transferred

into the electronically controlled cutting machine or

directly record on magnetic tape cartridge.

Home works

1. Get to know each part of the Jacquard

machine at Fig.10.1.

2. Get to know how the design paper is

selected.