1.3 Fabric Representation

1.3.1 Methods of Weave Representation1.3.2 Repeat of weave and shift1.3.3 Drafts 1.3.4 Weaving plan1.3.5 Lifting plan1.3.6 Relations between Weave, Drafts, and Lifting.

1.3.1 Methods of Weave Representation How can you describe the structure of a fabric?

We can use different ways:

Plan diagram

Cross-section diagram

longitudinal-section diagram Canvas method

Plan diagram

Cross-section diagram

longitudinal-section diagram

Main points about the canvas method: The canvas method is widely used in the world.

1.3.2 Repeat of weave and shift

Here is a plain weave. From the diagram, we can see, the 3rd warp thread has the same movement with the 1st, and the 4th same with 2nd. Similarly, the 3rd weft thread is same with the 1st weft thread; the 4th is same with the 2nd.

Thus, the weave repeats after 2 ends and 2 picks. So, we define that: (shown in the next page)

Repeat:

The warp repeat----- the minimal number of warp threads after which the movements of warp threads repeat.

The weft repeat ----may be defined analogically. The Weave repeat---- a complete element of the

weave. Following are some examples:

2) Shift (move)

Shift is the distance from a painted square on a thread to its corresponding painted square on its adjacent thread.

The shift can be counted in warp way, So, and in weft way, Sy, (mostly in warp way)

The shift can be either positive or negative, depending on the direction of counting. Counting from the left to right or from low to high gives positive shift.

Schematic diagram of shift

1.3.3 Drafts 1. The various Drafts 1) Some concepts ① Draft ---- The draft shows the number of shafts and the man

ner in which the warp threads are drawn into the shafts. ②Why does it need to draft ? The warp threads must be drawn into the healds, for separating the

warp threads to form shed. ③ Position: The draft is usually shown at the top of the weave diagram.

The various drafts can be classified as follows:

⑴. Straight . Divided⑸ ⑵. Skip and sateen . ⑹

Grouped ⑶. Pointed . Curved⑺ ⑷. Broken . ⑻

Combined

① Straight draft

Each successive thread is drawn in successive shaft, i.e. the first thread in the first shaft, the second thread in the second shaft, and so on (see Fig. 1.9).

Fig.1.9

② Skip draftThis is used in weaving the fabrics with a high density of warp threads for reducing the friction between thread and thread as well as thread and healds

Three healds on each shaftTwo healds on each shaft

2. Requirements to Drawing-in

1). The possibility of using a straight draft should be studied first. Then the simplest type of draft, suitable for the given weave should be chosen.

2). The number of shafts should be as small as possible, but the density of healds is to be calculated and should not exceed the standard value.

3). The distribution of threads on different shafts should be as uniform as possible. In some cases additional shafts can be added to reduce the density of healds.

4). It is advisable to use the front shafts with minimum height of lifting for the threads with biggest number of intersections in the weave repeat and for a weaker system of warp threads.

5)Warps with different movement must not be drawn into the same shaft and warps with same movement can be drawn into different shafts

Requirements to Drawing-in

1.3.4 Weaving plan

The weaving plan consists of three elements placed in a certain order: (1) weave, (2) draft, or drawing-in, (3) lifting plan.

These three elements are closely dependent on one another. If any two elements of the weaving plan are known, the third element can be constructed. (see the figure on the right)

Weaving plan gives the introduction of weaving process.

1.3.5 Lifting plan

In order to produce the required weave the designer has to provide a lifting plan for the purpose of controlling the lifting and lowering of the shafts. In dobby shedding the plan is used either for pegging a set of lags or cutting a paper card.

Lifting plans are indicated on the right of the weave diagram.

Example: See the right figures, to obtain the given weave there are 4 vertical spaces in the lifting-plan controlling the 4 corresponding shafts in the draft

1.3.6 Relations between Weave, Draft, and Lifting.

Three elements of a weaving plan are dependent on one another. Any element of the weaving plan can be constructed if two others are given.

1. Construction of Lifting Plan from the Given Weave and Draft.

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2. Construction of Draft from a Given Lifting Plan and Weave. This diagram shown the lifting plan and the weave are given, and the p

roblem is to construct the draft.

To Construct the draft

Principle and method The number of vertical spaces

at C corresponds to the number of horizontal spaces at B. It means that the first vertical space at C controls the first shaft, the second vertical space controls the second shaft, and so on. Then the draft is constructed by comparing the arrangement of the lifting plan at C and weave at A. and so on.

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3. Construction of weave from a Given Draft and lifting plan.

Homework: 1. Explain the concepts: Repeat, warp repeat,

weft repeat, weave, shift. 2. Construct. Lifting plan from given weave

and draft. (See Fig.1) 3. Construct weave from given draft and

lifting plan. (See Fig.2)

Fig.1

Fig.2