13 Knitting

T. Palani Rajan

1. Introduction

Human “Basic needs” relate to those primary requirements that provide as the base for survival. According to the essential desires of life, as well as shelter, food, and article of clothing is required to the event of a powerful community and an essential precursor to individual independence. The article of clothing is fiber and fabric of textile material worn or drape on the human body. The quantity and sort of clothing could be a dependent on gender, physical stature, in addition to social and geographic concerns. Actually, clothing serves several purposes: it will provide as protection from climatic condition, and might enhance safety throughout risky activities for example climbing and food preparation. Fabric and clothing may be created out of natural fiber plants like cotton, synthetic plastics like polyester, or animal product and hair like wool. These clothing may be producing from numerous material and fabric forming systems according to its applications.

2. Fabric forming methods

Textile micro structures like fibers or yarn is converted to the textile macro – structure for the manufacturing of fabric. Yarns are most probably used as raw materials for the manufacturing of fabric. The yarn into fabric is that the most versatile technique of producing textile materials for an extensive choice of end-uses. In figure 1 shows the weaving, knitting, braiding and crocheting are the popular manufacturing systems that possibly used in construction of verity of goods. Bonding is the technique to manufactured non woven fabric by using fibres as a raw material.

Three basic principal strategies of converting yarn into textile fabrics: interweaving, interlooping and intertwining. All these three methods have developed from the manual techniques.

2.1 Weaving

The principle of weaving is interlacement yarns and producing woven fabrics. Woven fabrics are constructed by means of two set of yarns called warp and weft (filler). Warp yarns run lengthwise i.e. parallel to selvedge and weft yarns run cross wise i.e. perpendicular to selvedge shown in figure 2.

2.2 Knitting

The second most often used technique of fabric construction is knitting. Knitting is that the art of constructing a knitted fabric with knitting needles by interlooping one or more number  of yarns in many series of interlinked loops. From the figure 3 the loops are hanging and supporting each other.

2.4 Braiding

Braiding may be an easy variety of slim fabric construction that yarn contributes in three directions. Figure 5 shows a braid may be a rope like material that is formed by interweaving of three or more stands of yarns. The flat braided fabrics are producing strips or lengths in a diagonally overlapping pattern used for a variety of industrial purposes.

3. History of knitting

Knitting is a “timeless arts” and be in this world forever. But the truth is, it give the impression to have been invented in the first millennium, possibly as near the beginning of 8th C. Development of knitting from hand knitting with one to two hand needles and forward to peg frames, peg frames, stock frames, commercial knitting machines and modern fully automatic knitting machines.

14th century – Peg Frame: For the period of 1390, it absolutely was said that fashion accessory (gloves) were manufactured using knitting and its knitting elements. Peg frames was used to knit both gloves and caps.

16th century – Stocking Loom: In the 16th century, knitted stockings developed into high fashion. Stocking frame was designed Rev William Lee to construct fine silk stockings. Because of reasonable production and quality, hand knitters opposed the concept of stocking knit frames. Consequently, development in framework knitting took much more time and later it developed very gently in the next century.

18th century – Framework Knitting: In 1759 Jedediah Strutt and Belper introduced “Derby rib frame.” This might be the primary conversion of single bed knitting frame to a double bed knitting frame and it was a great motivation for growth of knitting frames. Samuel Betts joint the tuck with rib frame to expand his tickler bar knitting.

19th century – The Lamb Knitting Machine: Mr. Lamb developed the first domestic knitting machine about 1867. This machine have 84 needles with 15 lbs. In 1879, the Crane Knitter was introduced with 106-needle which is similar to modern flatbed knitting machines. About this period, the circular sock knitting machines also start to come out.

Modern Machines: Subsequent to the turn of the century, modern machines began to come into view shortly. The principle mechanisms of today‟s machines remain same. However, the advanced electronics devices have replaced mechanical punch cards systems and fully automatic computerized machine developed for many new design innovations.

4. Hand knitting

Thousands of years the hand knitting has been experienced for the manufacturing of knitted and crochet fabrics. Still it is a mystery that where this art was invented. Hand knitting is to construct a fabric by means of yarn using two or more hand knitting needles shown in figure

Usually two needles used and the loops are transferred from one hand needle to the other. It fabricates rows of linked loops to create a fabric.

On first needle, number of loops are formed and then the loops are grows as a fabric by drawing further loops from side to side. The loops are passed back and forward along with the needles from the row to row. Two kinds of stitches are formed in all kind of knitting. First one is “knit stitch,” and the second is “purl stitch.”

The Industrial and economic revolution took over the hand knitting to the invention of machine knitting.

5. Growth of knitting

There are number factors involved in the reason for the growth of knitting industries.

• No yarn preparatory machineries are required for weft knitting. Only beaming process required for warp knitting.
• Labour force requirement is less.
• Capital investment cost is less than other fabric forming techniques.
• Productivity of machine is high.
• Design and style can be changed and modified rapidly.
• More flexible operation.
• Give better wearing and fitting comfort.
• Fabric is wrinkle free and easy to maintain.
• Seamless garment can be possible
• Good demand for fabric and garment export.
• Used for special applications like technical textiles.

6. Characteristics required for knitting yarns

A good knitting yarn ought to have the subsequent characteristics within the order of their comparative importance:

• Uniformity of diameter
• Flexibility
• Elasticity
• Strength

Uniform in Diameter

A good knitting yarn ought to be as uniform in diameter as is feasible. Variations in yarn diameter exposed by knitted fabrics far more than any other fabric manufacturing system. The strange loop configuration places a superior length of yarn within a comparatively minute space in the fabric. Because of this, a thin or thick place present in the yarn is exaggerated in the fabric appearance. The uniformity in diameter is of such significant characteristics, which improve the appearance and uniformity in a knitted fabric.

Flexibility

Flexibility is important characteristics during knitting and knitting yarn, the yarn can knit the loops without delay. Knitted fabrics consist of a sequence of yarns interloped together. A rigid, stringy supply yarn refuses to accept the loops formation and is not good for knitting process. The soft twist hosiery yarns provide addition elasticity to increase fabric flexibility.

Elasticity

The ultimate knitted fabric performance can be increased by elasticity in a knitting yarn. . Elasticity is that property that sources a yarn to presume its original length of yarn subsequent to stretch through any tension smaller than its elastic limit. This elasticity creates an additional compact, slighter looped and added elasticity in knitted fabric.

Strength

The relative necessary of strength during a knitting yarn is a smaller amount than the other characteristic. The knitting action is comparatively easy by using any yarn. A flexible weak yarn can provide sufficient characteristics while knitting. But in rigid yarn have brittle nature and not able to knit. However that is not because of lacks strength of yarn, lacks of flexibility and elasticity. The comparative significance of yarn strength as a quality in a knitting process permits a yarn to be knit and support fabric with flexibility and elasticity.

7. Classification of Knitting

In the knitting method one set of yarns is employed from one direction that might be horizontally (weft knitting) or vertically (warp knitting) direction. Horizontally or vertically direction yarn formed through loops and stitches for the manufacturing of knitted fabric. In knitted fabrics, the loop is the primary component and stitches all the corresponding loop of all the knitted fabrics. Loop is the fundamental unit interlooped with the formerly formed loops by means of hooked needles Based on the method of loop formation knitting can be classified in two weft and warp knitting shown in figure 7. In weft knitting, loops are created in a horizontal course direction but in warp knitting, loops are created in a vertical wale direction

7.1 Weft Knitting

Weft knitting is that the commonest form of knitting, it is the method of constructing a fabric by means of shaping a sequence of linked loops in a horizontal or course-wise direction shown in figure 8. Weft knitting machines can be sub classified into circular and flat knitting according to the fabric delivery, form of needle bed, type of needle and type of fabric. Circular knitting machine needles are placed parallel in one or more circular needle beds. Alternatively, flat knitting machine make use of straight needle beds having separately functioned needles.

Applications:

• Garments like T-shirts, polo shirts, dresses and children‟s, casual skirts, jackets, suits dresses are made.
• Tubular seamless hosiery knitted fabric/garment can be manufactured circular knitting machines.
• High stretch sportswear with good dimensional stability is produced.
• Collar and cuffs manufactured by flat knitting and even some times sweaters are too made.
• Using tuck stitches, highly complicated textured patterns fabrics are made.
• Through weft knitting hats and scarves are made to use in the winter season.
• Industrial application fabrics also made like filter material, cars upholstery etc.

7.2 Warp knitting

Warp knitting is that the methods of constructing a cloth by shaping a loops in a vertical or wale-wise direction and it shown in figure 9. Yarn in beams is a supply material as warp and one or more yarns feed for each needle. The warp knitted fabric is flatter and less elastic than weft knitted fabrics.

Applications:

• Fabric type of tricot warp knitting is used to manufacturing lightweight fabrics frequently inner wear.
• Raschel warp knitting system is used for manufacturing a material for straight skirts, coats, jackets, and dresses.
• Sportswear, tracksuits, leisurewear and safety vests also used to manufacture.
• In home textile, warp knitted fabrics are used for constructing mosquito nets, mattress, furnishing, laundry bags, and fishnets.
• Industrial safety shoes are finished through warp knitting inner linings.
• From warp knitted fabrics head rest lining, car cushion, motorbike helmets lining and sun shades are being made.
• Industrial PVC/PU backing, caps, gloves and production masks are also made.
• Three-dimensional knitted constructions can be manufactured through simplex warp knitting machines.
• Bio-textiles products are also made from warp knitting process.

7.3 Differences in Warp and Weft Knitting

8. Knitting terms and definitions

Knitting processes manufacturing the fabrics with specific details on fabric structure by using the different techniques in knitting machine. It can be grouped into two categories.

• Fabric Terminology
• Machine Terminology

8. 1 Fabric Terminology

Fabric terminology represents all the terms and function related to fabric structure and geometrical properties.

Loop

The primary unit of a knitted structure is loop and that is shaped by „kinking‟ (bending) of the feed yarn and it is intermeshed with similar loop. The loop contains two segments head and foot that are connected by loop leg shown in figure 10. Apart from this the loop is shaped by the knitting element of needle and sinker forming needle loop and sinker loop in figure 11 and 12.

Fig. 10. Head and food loops

• Head loop– The top or head curved part of a loop
• Legs loop– The two sides of legs appearing a V-shape
• Foot loop – At the bottom of each one leg is foot and all loops going at the back of the legs shaped through the lower loop.
• Needle loop – The collective top arc of the loop.
• Sinker loop – The bottom piece of yarn that connects to one needle loop to the next one in weft knitted structure.
• Open loop – In a loop the same thread goes in and leaves the loop at the opposite walls without crossing (Figure 13).
• Closed loop – At the base of loop the thread is crosses over itself (Figure 14).
• Face loop – It refer the loop, legs are able to be seen and positioned on the head of already formed loop in the same wale (Figure 15).
• Back loop – It is called as reverse stitch or purl stitch. The head loop is observable and positioned on the legs of the following loop in the same wale (Figure 16).

• Course Length – The length of yarn used in form all the knitted loops in one course of fabric. It can be referred to run-in.
• Course density / Course Count – The number of courses decides the total length of the fabric and is calculated in a defined unit of Courses per Inch (CPI) or Courses per Centimeter (CPCM).

Wales

In figure 18, the vertical columns of loops are called wales and it traverse across the width of the fabric formed by means of the same needle through the nearby cycle of knitting.

• Wale density / Wale Count – The number of wales in a knitted fabric in a predefined unit  length called as wale density that are calculated in units of Wales per inch (WPI) or Wales per Centimeter (WPCM).

Stitch Density

Stitch density is the product of the courses per unit and wales per unit. It characterizes the number of needle loops in a given unit area.

Stitch Length

The length of yarn occupy in a single knitted loop is called as stitch length. It can be measured in millimeters or centimeters. The stitch length can be calculated by: Stitch length = Course length / Total no. of needles

8.2 Machine Terms

Cut or Gauge

The number of knitting needles arranged in a unit area (per circumferential inch) on the cylinder.

Number of feeders

It produces course one by one on revolution of the knitting machine. A feeder is represent by one or number of cams with a yarn supplying unit. The number of feeders used in knitting is mostly in even number.

Number of feeders depends on:

• The machine diameter
• The fabric forming principle (Plain, rib, purl)
• The possibilities of pattern
• The gauge of machine.

Gating

Gaiting is the arrangement needle employed to construct double jersey knitted fabrics. The spacing of the cylinder and dial needles in relation to each other on rib and interlock knitting machines. Two type of double jersey knitting gaiting are available. In rib gaiting, the needles are arrangements in the cylinder are between the needles of the dial. In interlock gaiting, the needles in cylinder are in a straight line to the needles in dial (opposite to each other) and appearance like right angle.

REFERENCES and URLs

• David Spencer, J 2001, Knitting Technology – A Comprehensive Handbook and Practical Guide, Woodhead Publishing Limited, England
• Ajgaonkar D.B., 1998, Knitting Technology, Universal Publishing Corporation, Mumbai.
• Chandrasekhar Iyer, Bernd Mammel and Wolfgang Schach., 1995, Circular Knitting, Meisenbach GmbH, Bamberg,
• Anbumani N, 2014, Knitting – Fundamentals, Machines, Structures and Developments, New Age International Publishers, New Delhi.
• http://mytextilenotes.blogspot.com
• www.knittingtradejournal.com
• http://www.knitepedia.co.uk/browse/knit_tech
• http://www.textileschool.com/Home.aspx
• https://en.wikipedia.org/wiki/Knitting