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Weaving

 Brief History

Weaving is the action of producing fabric by interlacing warp and weft yarns at right angles to each other. This action can be produced on a frame, hand loom or automatic loom. The handloom has been around many years and with a significant development in 1733 when John Kay developed and patented the ‘Flying Shuttle’. This development helped fuel the industrial revolution. The first automatic loom was designed in 1784 by Edmund Cartwright and the next 47 years were spent perfecting this design until Kenworthy and Bullough developed the Lancashire loom in 1842. However this loom was not fully automatic and had to be stopped every time the shuttle needed new weft yarn. In 1984 George Draper and Son’s marketed the Northrop loom, a fully automatic loom, with a self feeding shuttle. It was named Northrop loom after its inventor ‘James Henry Northrop’. From 1942 technology advanced again with the invention of modern automatic and shuttle less looms. Today weaving is used in far more applications than any other textile manufacturing method.
The following video link gives a brief overview of the history of weaving to modern day technology:

Mechanism of the Shuttle loom

The modern automatic looms are based on the simple mechanisms of the handloom (hand shuttle loom). In order to understand how an automatic loom works, it is useful to consider the mechanisms of a hand loom. Figure 1 depicts the essential features a handloom. The following are the key components which control the weaving process.
The warp beam: The beam which the warp was wound onto during warping. As shown, the warp yarns are passed from the warp beam and over the whip beam, through the heddle wires in the shafts, the through the reed and onto the cloth beam.

The whip beam: The whip beam helps to keep the warp yarns under tension as they move from warp beam to cloth beam.

The heddle: Also known as ‘heald wire’, is a looped cord shaped wire with a hole in the middle known as an eye. These wires are attached to a frame known as a shaft. One warp yarn passes through one eye.

Shaft: This is a frame which holds the heddles. The more shafts used enables a more complex pattern can be woven.

Reed: Also known as a ‘sley’ is a device consisting of several wires closely set between two slats. It serves as any or all of the following purposes:

1. Separates the warp yarns
2. Determines the spacing of the warp yarns
3. Guiding the shuttle
4. Beating-up the weft yarn into the fell

Batten: A flexible device which the reed is attached to, in order for pushing back and forth to create the shed and allow beating-up. 

Fell: The line of termination of the woven fabric where the last weft yarn was beaten-up.
Shuttle: A yarn package carrier that is passed through the shed to insert a weft yarn (picks).

Breast beam: Holds the woven fabric under tension and guides the fabric onto the cloth beam.
Cloth beam: The woven fabric is wound onto the cloth beam under tension.

Treadles: Peddles which activate the movement of the roller above the shafts, alternating the and down motion of the shaft.
 

Hand Loom Fig 2

Fig.1 Hand Loom

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Weaving Process

The weaving process consists of five basic operations, shedding, picking, beating-up, left off and take up.

Shedding: Separating the warp yarns into two layers by lifting and lowering the shafts, to form a tunnel known as the ‘shed’. See Figure 2.

Shredding Fig 2

Fig 2. Shredding

Picking or Filling: Passing the weft yarn (pick) across the warp threads through the shed. See Figure 3.

Picking Fig 3

Fig 3 Picking

Beating-up: Pushing the newly inserted weft yarn back into the fell using the reed. See Figure 4.

Beating-up Fig 4

Fig 4 Beating-up

Let off:    The warp yarns are unwound from the warp beam during the above three processes.
Take up: The woven fabric is wound on the cloth beam during the above three processes.

The above operations must be synchronized to occur in the correct sequence and  not interfere with one another. The full sequence is repeated for the insertion and interlacing of each weft yarn length with the warp yarns, and is therefore called ‘The Weaving Cycle’ 

The following video link shows the five basic operations in weaving mentioned above: Primary Weaving Motions: (Youtube)

Shedding Mechanisms:

All weaving machines control the warp yarns to create a shed. This can be accomplished with the following systems:

• Crank shedding
• Cam shedding or tappet shedding
• Dobby shedding
• Jacquard shedding

Crank, cam and dobby mechanisms control the harnesses which lift the shafts. Jacquard machines control the individual warp yarns. Each system is outlined below:
Crank Shedding:
Crank shedding mechanisms are simple and relatively cheap to use. However it can only be used for plain weave fabric constructions. In this system the harnesses are controlled by the crank shaft of the weaving machine. For each crank shaft revolution a wheel is rotated half a turn, which changes the harness position.  This system is only used in air-jet and water-jet machines where high speed is achieved.
Cam Shedding:
Cam shedding is also simple and inexpensive. A cam is a disk which has grooved or conjugated edges which corresponds to the lifting plan. The lifting plan controls which harnesses are lifted. The disadvantage of cam shedding is that when the woven design has to be changed the cams have to be rearranged to suit the new design. Pattern design is also limited due to the amount of harnesses the cams can control.

Dobby Shedding:
Dobby shedding is more complex than crank and cam systems. The main advantage of dobby looms is that more intricate designs can be produced. Older dobby looms were operated by wooden lags with pegs, which rotated around a roller above the loom. The pegs in the lags correspond to the lifting plan, which controls which harnesses are lifted.  Punched paper or plastic pattern cards can also be used. Recently modern dobby looms are controlled via an electronic system. The disadvantage of dobby systems is that faults are more likely to occur due to there complexity.
The following video link shows an electronic dobby loom mechanism:

Jacquard Shedding:

In jacquard weaving a device called a ‘jacquard’ selects and lifts the warp yarns individually.  This type of machine is used for larger more detailed patterns, where all or most of the yarns in a repeat, move independently. There are single or double lift machines which use either mechanical or electronic systems, using CAD to control the harness lifting and lowering. Modern jacquards are capable of handling over 1200 harness cords which control the lifting and lowering of the warp yarns.
The following video link shows an electronic jacquard loom weaving tapes:

Weft Insertion Methods:

Modern automatic looms do not require a shuttle to carry the weft yarn across the shed.  Instead the weft yarn is inserted by either one of the following methods:
Rapier:
A shuttleless weaving loom in which the filling yarn is carried through the shed of warp yarns by fingerlike carriers called rapiers. There are two types of rapiers.
1. A single long rapier that reaches across the loom’s width to carry the filling to the other side.

2. Two small rapiers, one on each side. One rapier carries the filling yarn halfway through the shed, where it is met by the other rapier, which carries the filling the rest of the way across the loom. The insertion rate of picks can be up to 1000 m min-1.

Projectile:
Projectile machines carry yarn through the shed using a small bullet shaped object known as a ‘projectile’. The yarn must be presented to the projectile in order for it to grip this. This process can occur in the following ways:
1.  A single projectile is fired from each side of the machine alternately and requires a bilateral yarn supply.

2. A yarn supply from one side of the machine is presented to the projectile. It carries the weft yarn across the machine and is then transported back to the other side by a conveyor belt. Several projectiles are in use at the same time to enable rapid pick insertion. Pick insertion rate can be up to 1300m min-1.

Air jet:
In air-jet weaving machines the filling yarn is inserted pneumatically. It is carried through the shed by compressed air flow supplied from a main nozzle and relay nozzles. This is the fastest type of weaving enabling pick insertion of 3000 m min-1.

Water jet:
Water jet weaving is the same principle as air jet weaving, water is used instead of air and a similar speed is achieved. One disadvantage is that only hydrophobic yarns can be used.

Multiphase
All of the above methods are classed as single phase weaving, where by the weft yarn is laid across the full width of the warp yarns and beat-up takes place. Multiphase weaving involves several phases of the weaving taking place at the same time, so that several picks can be inserted simultaneously. The shedding mechanisms of the weaving affect this process:
1. Wave shed machines carry the yarn in either straight or circular paths. Parts of the warp are in different stages of the weaving cycle at any one moment. It is possible for a series of weft carriers to move along in successive sheds in the same plane.
2. In parallel shed machines numerous sheds are formed simultaneously. Each shed extends across the full width of the warp and moves in the warp direction.

The following video link shows the different types of weft insertions mentioned above:

Limitations and Energy Consumption:

Although air and water jet machines can weave fabric at higher speeds compared to the projectile and rapier looms, the high power consumption results in higher costs. The flow of the air is also difficult to control and waste heat produced by the compressors is sometimes wasted when it could be used for other operations in the factory. However cooling of the factories via air Conditioning? is not always necessary with air and water jet looms and so energy costs are saved in this way. The rapier and projectile looms produce a lot more heat and so air Conditioning? is often installed to keep temperatures down within the factory. Multiphase wave shed looms moving in a straight path have not been commercially successful as maintaining a clean shed has proved very difficult. The weft insertion rate of 2200 m min-1 was very attractive they became obsolete when simpler air jet machines began to surpass this speed. The following journal article gives further details and information: ‘Analysis of Energy Consumption in Woven Fabric Production’ http://www.fibtex.lodz.pl/article329.html

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Weaving (cont.)

Woven Fabric Design

Design of Weave
Woven fabrics are composed of warp and weft yarns which interlace with one another according to the weave design. A woven fabric design can be clearly indicated on square paper. The squares are used to indicate where the yarns interlace with each other. Each column represents a warp yarn and each row represents a weft yarn. For plain weave the warp and weft yarns pass over and then under each other once. This is repeated throughout the fabric structure. The place where one warp yarn passes over one weft yarn is indicated by a cross in the square. When one warp yarn goes under one weft yarn the square is left blank. Figure 5 shows a plain weave fabric, the smallest unit of weave that repeats to form the fabric is highlighted in red.

Fig 5

Figure 5

The following video links show different fabric designs:

Basic Understanding of Fabric Design:

 

Satin and Sateen: 

Drafts
A draft indicates the order in which the warp yarns are drawn through the heald wires in the shafts. This can also be drawn on square paper. Each column is used to indicate a warp yarn and each row indicates a shaft. A mark is used to indicate which shaft an individual warp yarn is drawn through. Every column in the design which has the same pattern can go onto one shaft. The example below in figure 6 shows a plain weave design. The numbers below correspond to a shaft number.  A draft can then be drawn to show which warp yarns are drawn through the heald wires in which shaft.

Fig 6

Figure 6

Denting Plan
The denting plan indicates how each yarn is drawn through a dent in the reed. For plain weave this is very simple, normally one yarn will be threaded through one dent. However for more complex designs where two or three warp yarns follow the same pattern, these warp yarns may be drawn through one dent. However this also depends on the yarn count. Figure 7 shows the denting plan for a more complex design. 

Fig 7

Figure 7

Lifting plan (Pegging plan)
A pegging plan indicates the order in which the shafts rise and fall. The pegging plan represents the design on the square paper. On old hand looms this design was pegged into wooden carriers which were rotated on cranks. However in modern day looms a computer system tells the machine what shafts to lift and lower.

Computer Aided Design (CAD)
CAD is used for constructing woven fabrics, by creating your design, draft and pegging plan on a computer softwear. ‘Scotweave’ is one of the well known CAD systems for this purpose. 
The following video link shows fabric design using a CAD system.

Computer Simulation of Weaving Preparation:

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3D Weaving

The term 3D weaving is commonly used in reference to the weaving of cloths that have pre-designed three-dimensional shapes, or can be directly manipulated into a 3D shape immediately after being woven. It is also used to describe the weaving of fabrics with substantial thicknesses, many times greater than the diameters of the yarns used to produce the fabrics.

3D woven fabrics play an important role in the development of advanced fibre reinforced composites. They are used as preformed shapes ready for resin impregnation or as thick materials with structural integrity, which when resinated have good interlayer shear strength and thereby outperform conventional laminated products.  

3D Shape Weaving
Conventional rapier-dobby looms can be used to produce certain three dimensional shapes by weaving multiple layers of fabric interlinked to each other, similar to a ‘double cloth’, so that after being woven the layers of 2D fabric can be manipulated into the required 3D shape; for example, a dobby loom can be used to produce the cellular structures of Fig. 8. For obvious reasons, this method is also termed multilayer weaving.
Rapier-Jacquard looms are used to produce directly woven thin, complex, 3D-curved geometries, such as the helmet, the dome and the motorbike body panel shown in Fig. 9.  These shaped structures are essentially based on 2D weaves, where the weft and warp yarns are in the horizontal plane, by convention in the x and y directions, of the fabric. No yarn lengths are present in the z direction of the fabric to give the 3D shape its thickness; the thickness is given by the diameters of the warp and weft yarns. 

3D Fabric Weaving
Although the above shapes may be classed as woven 3D structures, an actual woven 3D fabric is constructed so that lengths of its constituent yarns are positioned in the z- direction to produce the fabric-thickness, as well as lengths being arranged in the x- and y- directions for the fabric length and width.  The conventional 2D multilayer weaving can be used to construct 3D fabrics, but for profiled 3D fabrics (i.e. thick fabrics with a designed shape - termed shaped 3D fabrics) specially built looms are required.
2D Multilayer Weaving of 3D fabrics
Two techniques are used:- interlacing and non-interlacing

Interlaced 3D Fabrics
With an interlaced 3D fabric, multi-layers of warp and weft yarns provide the fabric thickness (z) as well as its length (y) and width (x) by the action weft or warp interlock as illustrated in Fig.10.  The multi-layer warp lengths are placed to give the fabric thickness by a pre-set sequence of the shedding operation across the loom width (or fabric-width) to enable the correct interlacing with the weft. Notably, the yarn lengths making up the x, y, z directions of such 3D woven fabrics are not geometrically at 90o to each other (i.e they are not orthogonally positioned). 

Non-interlaced 3D Fabrics
Whereas interlaced 3D-fabric weaving involves only two sets of yarns, a non-interlaced 3D fabric requires three sets of yarns as depicted in Fig.11; a multilayer warp (z-direction) and weft (x-direction), and a binder warp (y-direction). As the figure shows, the loom’s shedding operation requires only one heddle (or heald frame) which is used for the purpose of laying-in the binder warps in the z-direction to firmly hold the multiple layers of the other yarns thereby forming the fabric thickness.  This process of weaving 3D fabrics is referred to as Noobing, i.e. Non-interlacing, Orientating, Orthogonally and Binding, which are the key features of both process and fabric.

3D Weaving of 3D Fabrics
As stated above these are specially constructed looms which can produce directly woven complex shaped 3D fabrics of substantial thickness. The designs of such looms are not publically available, but certain basic features are described in accessible patents.  These patented processes are referred to as true 3D weaving because the weaving actions enable interlacement of three orthogonal sets of yarn: a set of multilayer warp (Z) and two sets of weft (X & Y), referred to as the horizontal and vertical wefts, respectively.  Fig 12 illustrates how the three orthogonal sets of yarns can be interlaced to produce a ‘fully’ interlaced 3D fabric.  To achieve this form of interlacing requires duel-directional shedding of the multi-layer warp (Z); that is to say, a shedding operation in the fabric-thickness direction as well as in the fabric-width direction, forming multiple column-wise and row-wise sheds.  This ‘duel-directional’ shedding occurs sequentially and not simultaneously.  The two orthogonal sets of weft are then alternately inserted in the mutually perpendicular multiple sheds. Since each weft is interlaced around a warp yarn, the warp yarns remain straight.  As is apparent form Fig.12, any yarn movement is fully constrained resulting in a highly stabilised fabric structure.

3D Fig 8

Fig.8 Multilayer Woven Cellular Structures produced on Conventional Loom  

3D Fig 9

Fig.9    3D Complex Shapes Woven on Conventional Jacquard Loom
[Source: Innovative Textiltechnik GmbH  http://www.shape3.com/Frameset_Shape3.htm]

3D Fig 10

Fig. 10 Interlaced 3D fabric structures

3D Fig 11 

Fig.11  Weaving of Non-interlaced 3D Fabric Structure

3D Fig 12

Fig.12 3D Woven Interlaced 3D Structure

The following journal article gives further details and information about 3D fabrics for composites: ‘An overview on fabrication of three-dimensional woven textile preforms for composites’

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Weaving in Technical Textiles

Woven textile fabrics are found in all market sectors of the technical textile industry. Different requirements may be applied to the specifications of a woven fabric depending on its end use. For example in medical textiles, implantable woven materials will have to be biocompatible. Fibres such as Polyester (PET) or Polyurethane (PU) may be the preferred choice. A few examples of woven fabrics in technical textiles are listed below in the following links and journals:

Woven textiles for transport:
http://www.holdsworthfabrics.com/content/pages/
http://www.botanyweaving.com/products/products.html

Woven textiles in medicine and health care:
http://www.neoligaments.com/products/leeds-keio-shoulder-ligament.php
http://secantmedical.com/resource-library/articles/johnshopkinssprg2011.pdf

‘Organ Weaving: Woven Threads and Sheets as a Step Towards a New Strategy for Artificial Organ Development’, in: MACROMOLECULAR BIOSCIENCE, Volume: 11, Issue: 11, Pages: 1491 1498, Published: NOV 10 2011 

Woven textiles in personal protective clothing:
‘Ballistic-proof Effects of Various Woven Constructions’, in: FIBRES & TEXTILES IN EASTERN EUROPE, volume: 18, Issue: 6, Pages: 63-67, Published: JAN-DEC 2010 

Woven textiles in civil engineering:
http://www.bonartf.com/en/x/123/products
http://www.sglgroup.com/cms/international/products/product-groups/cm/textile-products/index.html?__locale=en

Woven textiles in smart fabrics:
Wearable electronics.pdf

Further Reading:

1. Sabit Adanur, Handbook of Weaving, 2000, CRC Press, London, ISBN 1-58716-013-7
2. William Watson, Textile Design and Colour, 1946, Longmans Green and Co Ltd
3. N. Khokar, The Journal of the Textile Institute, 1996, 87 Part 1, No 1, 97-106
4. Making of Woven Fabrics: 
5. Camira Fabrics: 
 

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