Chapter Seven Multi-ply Fabrics

7.1 Double fabrics 7.1.1 The concept of double Fabrics 7.1.2 The principles of double fabrics construction 7.1.3 Construction of double weave diagram.

7.1.1 Concept of double Fabrics

Double fabric consists of two layers which are woven one above the other. This fabric contains two systems of warps, and two systems of weft. This fabric can also be called two-ply fabric. The upper layer is formed by interlacing the face warp threads with the face weft threads, and the lower layer by interlacing the back warp threads with the back weft threads.

Applications: (1) A tubular fabric can be formed by connecting both

weaves at the selvages. (2) A double width cloth can be produced in conventional

looms by connecting one edge of the weaves.(3) Stitching the double fabrics to form a thicker and

heavier fabric.(4) The different materials can be used in each layer to

reduce the production cost.(5) Form patterns by interchanging double fabrics.

7.1.2 The principles of double fabrics construction

The principles of double-weave construction are shown as following. See Fig. 7.1.

Fig.7.1 Double weave

Fig. 7.1 shows a double fabric where face and back are all plain weave.

Here, the Arabic 1, 2 represent face ends and picks, and the Roman , represent back ends and picks.Ⅰ Ⅱ

The arrangement of face and back is 1:1, i.e. one face end, one back end; one face pick, one back pick.

For making double fabric, the picks are in sequence. When we fill the back pick, all the face ends must be lifted up.

The principles

Suppose the face ends are drawn in shafts 1 and 2, the back ends are drawn in shafts 3 and 4. The processes of the construction double fabric are described as following.

Show Flash

(1) First pick: This pick is face pick 1, and the entire back ends must be lowered down. The shaft 1 is lifted up. See Fig (A).

(2) Second pick: This pick is back pick , and all the Ⅰface ends must be up. The shafts 1,2 and 3 are lifted up, and shaft 4 remains down. See Fig. (B)

(3) Third pick: This pick is face pick 2, and all the back ends must be lowered down. The shaft 2 is lifted up.

(4) Forth pick: This pick is back pick , and all the face Ⅱends must be up. The shaft 1,2 and 4 are lifted up, and shaft 3 down.

7.1.3 Construction of double weave diagram.

To construct a double weave diagram, some elementary factors should be determined first:

1) Select the face weave and back weave.

2) Determine the arrangement of face and back in warp and weft directions.

3) Meet the weaving machine.

1) Select the face weave and back weave.

Due to their relatively independence, the face and back weaves can be same or not. But in order to weave smoothly with a uniform warp tension, the crimp of the two weaves should be quite similar .

2)Determine the arrangement of face and back in warp and weft directions.

The ratio of face to back : 1 : 1, 2 : 2 and 2 : 1 are recommended.

3) Meet the weaving machine.

If the looms are multi-box in both sides, any arrangement is possible. If the looms are multi-box in single side, the weft arrangement m : n must satisfy that: both m and n are even numbers.

Steps for the construction of double weaves:1) Select face and back weaves, and draw them.

2) Determine the arrangement m: n.

3) Calculate the double weave repeats.

4) Draw the outline of the repeat, and indicate the number of each space.

5) Transfer both face and back weaves to the new weave.

6) Lifters: all face ends are lifted when back picks are inserted.

Example:

Construct a double weave: face and back weaves are plain, arrangement m: n=1:1.

Select face and back weaves, and draw them:

See Figures A and B

The arrangement is given as 1:1 So, the new repeats can be obtained :

RO=4 Ry=4

Draw the outline of the weave of one repeat, and indicate the number of each space. Fig. (C)

Transferring the weaves. Fig. (D)

Lifters:

The mark ○ should be added at the intersections of face ends and back picks. Fig (E)

The longitudinal section and cross section are shown at Fig. 7.3 (F), (G).

The face ends are usually drawn in the front shafts, and divided drafts are usually employed.

Home works:

Construct the following double weaves.

(1) face weave 2/2 twill, back weave 2/2 ↗ ↗

twill, arrangement 1:1.

(2) face weave 2/2 twill, back weave 1/1 ↗ ↗

plain, arrangement of face and back in both directions are 2:1.