Braiding, Plaiting

o By Mr. Yong Kok Swee

Braiding is the simplest form of fabric formation and probably it is older than weaving. A braid structure is formed by the diagonal intersection of yarns. There are no warp and filling yarns in the sense of woven fabric. Braiding does not require beat-up and shredding; the yarns do not have to go through heddles and reed. Flat, tubular or solid constructions may be formed in this way. Tubular fabrics made by this process may be constructed with or without core, gut, filter, or stuffing threads, which when present are not interlaced in the fabric.

Figure 1.6 Common Types of Braiding Pattern

Diamond braid                Regular braid                    Hercules braid

A)   Two-dimensional braiding:  A two-dimensional circular or flat braid is formed by crossing a number of yarns diagonally to that of each yarn passes alternately over and under one or more of the others. The most common designs in two-dimensional braids are as follows:
     l         Diamond braid: 1/1 intersection repeat
     l         Regular braid: 2/2 intersection repeat
     l         Hercules braid: 3/3 intersection repeat

  1. Circular braiding: Circular （tubular or round）braids are formed hollow or around a centre core.

  2. Flat braiding:  Flat braids are made in the form of a flat strip or rape.

  3. Triaxial braid:  The axial yarns do not interlace or intertwine with other yarns and are trapped between the two sets of yarns in the structure. By inserting addition yarns in the axial direction, triaxial braided structure is obtained. Triaxial braids are particularly suitable for composites to be used as tension or compression members.

  B)   Three-dimensional braiding: Three-dimensional braiding is relatively new compared to two-dimensional braiding. The first 3-D braiding machine was developed in the 1960s. The three-dimensional braiding concept has been developed mainly for textile structural composites. There is no three-dimensional braiding machine that is commercially available. The main reason for this is that every different three-dimensional braided structure requires a different machine with specific characteristics and dimensions. Therefore, companies and research institutions custom-build their 3-D braiding machine. 

  C)   Narrow fabric weaving:  Ribbons, tapes and webbing are all considered as woven narrow fabric if they contain woven selvage, and are less than12 inches. They are woven on special narrow fabric looms, using the basic principle of warp and filling interlacing.  

1.4.2    Interlooping 
Knitting is a process of forming a fabric by the intermeshing of loops of yarn. Knitting involves the interiooping of one yarn system into continuously connecting vertical columns（wales）and horizontal rows（courses）of loops to form a knitted fabric structure. There are two basic types of knit structure: weft and warp knit. Knitted loop is a basic unit of weft- knitted fabric consisting of a loop of yarn meshed at its base with a previously form loop. At the point of mesh with the previously formed loop, a knitted loop is usually open but may be cross. Component parts of the knitted loop may be identified as: 

Figure 1.7 Knitted loop of weft knitting

  Back loop    face or front loop   needle loop   sides or loop     sinker loop

  • Back loop; reverse loop:  A knitted loop meshed through the previous loop towards the back of the fabric, away from the viewer.

  • Face loop; front loop; plain loop:  A knitted loop meshed through the previous loop towards the front of the fabric, towards the viewer.

  • Needle loop:  The upper curved portion of a knitted loop.

  • Side; legs:  The parts of the knitted loop that connect the sinker and needle loops.

  • Sinker loop:  The lower curved portion of a knitted loop

In the weft knitting, he yarn loops are formed across the fabric width, i.e. in the course of weft direction of the fabric In the warp knitting, the loops are formed along the fabric length, i.e. in the wale or warp direction of the cloth. In both knitting systems, the fabric is delivered in the wale direction. 

The basis of knit fabric construction being the continuing intersecting of loops, any failure of a loop yarn will cause a progressive destruction of the loop sequence and a run occurs. Thus, knitting yarns must of good quality in order that yarn failures be kept at a minimum. Other important geometrical definitions relating the knit structures are as follows: 

  • Count:  Total number of wales and courses per unit area of the fabric

  • Gauge:  The number of needle per unit width, the fineness or coarseness of the fabric.

  • Stitch:  The loop formed at each needle, the basic repeating unit of knit fabric structure

  • Technical face:  The side of the fabric where the loops are pulled toward the viewer.

  • Technical back:  The side of the fabric where the loops are pulled away from the viewer.

There are different types of warp and weft knitting machines for the production of fabrics, garments and are classified and named, primarily, according to: 

A)       The type of fabric or garment they are intended to produce;
B)       The type of needle used;
C)       The form, arrangement and activation of their needles or needle beds;
D)       The types of patterning control used;
E)       Whether they are hand-operated or power-operated

There are no convenient English terms to distinguish between machines in which the individual needle operate independently (Germany, Strickmaschine), and machines in which the needle are mounted so that they must be operated in unison (German, Wirkmashine), although this distinction forms the basis of classification of knitting machines. 

Both weft and warp knit structures can be used for composite reinforcement, especially for flexible composite. Weft knit structure can be easily conform to different shapes. Weft or warp knitting is suitable to manufacture 3-D knit structures. By inserting yarns in the 0° and 90º direction, addition reinforcement can be obtained in the knit structure. One disadvantage of knit structures is low fibre volume fraction.

1.4.2.1       Weft knitting
Weft knit goods are made by feeding a multiple number of ends into the machine. Each loop is progressively forming by the intermeshing of loop of yarn by the needle or needles. The previously formed yarn loop actually becomes an element of the knitting process with the latch needle. This is why the latch needle is referred to as the “self-acting” needle. As the needle is caused to slide through the previous yarn loop, the loop causes the swiveled latch to open, exposing the open hook head of the needle. The newly selected yarn can now be guided and fed to the needle. If a simple knitted loop is to be formed, the previous loop, the one which opened the latch, must slide to a point on the needle stem allowing it to clear the latch. Having the needle reach this clearing position allows a reversal of the sliding action which in turn pulls down on the new yarn and uses the previous yarn loop to close the latch trapping the new yarn inside the hook. The previous loop is now in a position to ride over the outside of the latch and be cast off the needle head, thus becoming a part of the fabric while the new yarn loop is pulled through the previous loop.

Depending on the structure in weft knitting, several types of knitting stitches are used including plain, tuck, purl（reverse）, and float（miss）, stitch which are in Figure 1.7:

Figure1.8 Types of Stitching in Weft Knitting

          
             purl（reverse）stitch                        float（miss）stitch                             tuck stitch

The plain stitch fabric has all of its loops dawn through to the same side of the fabric. The plain fabric has a very smooth face and a rough back. Other stitches produce different effects depending on the arrangement of the loops. Special stitches are also available to prevent runs.

Weft knitting machines may be either flat or circular, the former knitting a flat single layer of fabric, the latter knitting a continuous tube. No matter which machine configuration is used, weft knit manufacturing involves the same fundamental functions:

  • Yarn selection and feeding

  • Needle knitting action

  • Fabric control during knitting

  • Needle selection

  • Fabric take-up and collection

Knit fabrics can be classified as single knits and double knits. Single weft knits have one layer of loops formed with one yarn system. Three major types of single weft knits are jersey, rib and purl structures. Double knits have two inseparable layers of loop. Each yarn forms loops that appear on both faces of the fabric. Two major types of double knits are interlock double knit and rib double knit.

  • The major characteristics of weft knit fabrics are as follows:

  • Can be either manufactured as net-sharp or cut to shape and sewn

  • Form a run the wale direction if a yarn breaks

  • Have good stretch especially in the course direction

  • Do not ravel

  • Do not wrinkle easily and have good recovery from wrinkling and folding

1.        Single jersey, weft knitted:  A single knitted fabrics made on one set of needle. The characteristics may varied to achieve the desired end-use or patterned effects.

2.        Single jersey, jacquard, weft knitted:  A patterned single-jersey weft-knitted fabric, usually made from two or more yarns differing colour or texture to give a construction that consists essentially of knitted or float loops, but may incorporate tuck loops. The surface pattern is derive from the chosen arrangement of the yarns and of the knitted and float loops. The inclusion of tuck loops into the construction eliminates long lengths of floating threads from the back of the fabric.

3.        Single-jersey tuck jacquard, weft knitted:  A patterned single-jersey weft-  knitted fabric usually made from two or more yarns differing in colour or texture in construction that consists of knitted and yuck loops. The surface pattern is derived from a chosen arrangement of the yarn and of the knitted and tuck loop.  

4.        Single pique, weft-knitted:  A non-jacquard double jersey fabric made on an interlock basis using a selection of knitted and tuck loops in the following sequence. The fabric is sometimes referred to as cross tuck.

5.        Crépe, weft knitted:  an irregular, surfaced weft knitted fabric either plain or rib-based usually constructed from knit-float or knit-tuck loops introduced in a predetermined random order.

6.        Double jersey, weft-knitted:  A range of knitted fabrics made on a rib or interlock basis, the construction of which is often designed to reduce the natural extensibility of the structure. The term is generally confirmed to fabrics knitted on machine of E10 gauge or finer and it may be classified as either non-jacquard or jacquard double jersey.

7.        Eight-lock fabric, weft-knitted: a double-face interlock-based fabric that usually repeats over four wales. When knitted in colour the fabrics a vertical or check effect..

Figure 1.9 Eight-lock weft knitted fabric

   

8.        Interlock: weft-knitted:  A double-face rib-based structure consisting of two 1x1 rib fabrics, joined by interlocking sinker loops. It is made on machines equipped with two sets of opposed needles and capable of knitting in the following sequence as shown in figure 1.8. Interlock was originally knitted from cotton and used for underwear, but today it is knitted from various materials for a variety of purposes, including outerwear.

Figure 1.10 Interlock, Weft-knitted Diagram

 

9.        Rib fabric, weft-knitted: A fabric in which both back and face loops occur along the course, but in which all the loops contained within any single wale are the same types, back and face loops. There are many types of rib fabrics:

Broad rib fabric, weft knitted: A rib fabric in which groups of three or more adjacent wales are of the same types, rather face or back.

6x3 rib fabric, weft-knitted; Derby rib: a fabric in which all the loops of six adjacent wales are intermeshed in one direction and all the loops of the next three wales knitted at the same course are intermeshed in the opposite direction, and so on alternately.

1X1 rib fabric, weft-knitted; English rib: A rib fabric in which single wales of face loops alternate with single wales of back loops.

2X2 rib fabric, weft-knitted; Swiss rib: A rib fabric in which two adjacent wales of face loops alternate with two adjacent wales of back loops in a series.

Figure 1.11 rib fabric, weft-knitted

           1X! rib                             2X2 rib


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   Repeat                            Repeat  

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