Textile Weaving
In weaving, the warp and the filling may be interlaced in many different ways. The particular method that is used to interlace the warp and filling is called the weave. It is very interesting to study the various weaves; and it is important, too, because the weave greatly influences the texture of the woven cloth. Design that are woven in the cloth are plotted on design paper. This squared paper is arranged so that the vertical, or up-and-down, rows of squares represent the warp.
The horizontal rows of squares represent the filling. This is merely for convenience in counting the squares; it has no influence on the design. A riser is a painted block on the design paper. It indicates that the warp is raised over the filling at the point of interlacing. A sinker is an unpainted block and signifies that the filling is over the warp at the point of interlacing. In plotting or laying out ordinary weave constructions, the warp is painted on the design paper, the filling is not. Keep in mind that the warp is white, but it is indicated by painted blocks because the warp is always represented by painted blocks on design paper. Therefore this design on paper looks like a negative of the pattern in the cloth.
Plain weave
The plain weave is the most popular. Interlacing of the plain weave, which is also called taffeta weave, linen weave, calico weave, or tabby weave. You'll notice that each end goes over every second pink. Also, every pick goes over every second end. The weave repeat is therefore only 2 ends and 2 picks. If you don't quite understand this, take some trips of paper or pieces of string and interlace them in the manner. This little experiment will show you how the weave works. The plain weave has the shortest repeat and the tightest interlacing of any common weave. That is, while the ends could pass, or float over more than one pick, they could not possibly float over less than one pick.
With a given number of ends and picks per inch, the plain weave will give you a stronger and stiffer fabric than any other weave will give you a stronger and stiffer fabric than any other weave. As you'll see later, there are a great many possible variations in all other types of weaves, but there is only one plain weave. While the plain weaves is always the same, you can use it for a great number of different fabrics. For example, you can use more ends per inch than picks per inch. You can introduce colour into warp and filling. You can use different yarns and fibers.
Let's look at a few of the stable materials in the trade today made from these variations of the plain weave construction. A duck fabric in which heavy cotton ply yarn is used both in warp and filling. This is one of the strongest of all fabrics. The body of the cloth consists of coloured warp and white filling in a linen fabric. Variety is added by warp stripes in bright colours. The plaid dress goods clearly shows one of the many colourful variations possible in plain weave. The linen fabrics shows irregular filling yarn, which gives the cloth a homespun appearance and texture. You might note at this point that warp yarn is usually more regular and straighter in a fabric than filling yarn, which is under less tension in the loom during weaving. The result is that the warp yarn is bedded down in the filling yarn, and hardly shows on the surface.
The poplin is characterized by fine, tightly set warp and a slight cord effect, or rib, in the filling direction. Heavy, cylindrical filling yarn tends to give this surface effect in the cloth.
Seersucker, is made with a permanent crinkled or puckered effect in the warp direction. The effect can be put in during weaving, but it is introduced more often by a caustic print treatment in the finishing or the goods.
Plisse fabric, made to simulate seersucker, is often not permanent in finish, Moire, or watermarked effects, are often seen on taffeta and similar fabrics. Fine warp and cylindrical filling are used to obtain the surface effect, which is enhanced by the more treatment applied by engraved rollers in the finishing of the cloth.
A crepe fabric made with the plain weave in which certain risers are left out of the produce the crepe, sand, or granite feel and effect. The rayon crepe is made with the regular plain weave. Extra high twist in warp and filling yarns brings out the pebble effect in the texture of the fabric.
Twill Weaves
The simplest and smallest twill that can be made is on three ends and three picks. It is sometimes called the prunelle weave, or the jean twill. Twill weaves produce diagonal lines run to be right on the face of the material. The twill lines run from the lower left-hand corner to the upper right-hand corner.
However, some few cloths made with twill weaves have a left twill effect on the face of the fabric, running from the upper life-hand corner to the lower right-hand corner of the goods. The interlacing of one of the most common twills is the 2-up and 2-down twill, which is usually written 2/2. It has an effect formed by light-and dark-coloured yarns in warp and filling. It is a tweed fabric made from a 2/2 right-hand twill weave.
A solid-coloured Harris tweed made from a high-hand twill weave. There is a woolen fabric made from a twill weave with fancy or novelty warp yarn. A chalk stripe fabric made with a twill weave is a banjo stripe fabric. The same 2/2 twill weave is used in the black and 6-white check-effect woolen cloth. In the common twill weaves the diagonal lines make angles of 45 degrees with the filling. For example, in the 2/2 twill weave, one repeat requires the use of four ends and four picks. The rule is to go up one pick for each successive warp end in a 45-degree twill weave.
To make the 5th second repeat of the twill, as x-marks, the procedure is as follows : the 5th end and the 5th pick weave the same as the 1st end and the 1st pick, respectively: the 6th end and the 6 pick weave the same as the 2nd end and the 2nd pick, respectively; the 7th end and the 7th pick weave the same as the 3d end and 3d pick, respectively; the 8th end and the 8th pick weave the same as the 4th end and the 4th pick, respectively. In a 45-degree right-hand twill the riser moves up one pick for each successive end. The diagonal line goes to the right. In a 45-degree life-hand twill the riser moves down one pick for each successive warp end. For some purposes it is desirable to have the twill line steeper; for other purposes, not so steep. In the 63-degree twill, in the riser moves up two picks. In the 70-degree twill, the riser moves up three picks, and so on.
Reclining twill weaves are twill weaves in which the angle between the diagonal lines and the filling is less than the usual 45 degrees. Some goods are made with the regular 2/2 twill, or another regular twill, but still show a step twill line. If, for example, the goods have twice as many ends as picks per inch, the twill line will be 63 degrees, even though a regular twill weave has been used.
Effect and flush
The terms effect and flush are used to describe weaves with respect to the appearance noted on the surface of the cloth. There are three types of effect.
- Warp effect : In a warp effect, or war-flush weave, there is more warp than filling on the face of the cloth. For example, the 2/1 twill, has 2 ends up and 1 end down.
- Filling effect : In a filling effect, or filling-flush weave, there is more filling on the face of the cloth. In an even-sided effect, or equally-flush weave, like the 2/2 twill, there is the same amount of warp and filling on the face of the goods. These terms for the three kinds of effect also apply to other types of weaves, such as satins.
Twill weaves we have seen thus far were relatively simple. Now let's look at applications of twill weaves that are a little more complicated. A cavalry twill fabric made from 63-degree weave which is sometimes called elastique. The tricotine material in sample is characterized by the double-diagonal twile line. It is made from 3/1 3/1 1/1 1/1 twill of 63 degrees. It is the same weave as that used for the cavalry twill. The fabrics differ only in the yarns used and in the finish given to the cloth. There is no set rule that specifies whether or not a cloth must have a right-hand twill or a left-hand twill construction.
Custom, deep-rooted tradition, local circumstances, usage of the material, and the appearance are all basic factors in determining the weave direction. Some twill fabrics may be either right-hand or left-hand in the diagonal twill line effect. Drill jeans, and certain other small twill-effect constructions are often left-hand twill on the face of the fabric. The twill may be broken and reversed in the fabric. A broken-twill fabric, known as herringbone. The weave is 2/2 twill, with 8 ends of right-hand twill followed by 8 ends of left-hand weave.
A woolen fabric made with s broken-twill weave. The border or selvage, of the cloth may be observed at the left. A broken-twill fabric made with a 2/2 twill weave. It has 2 ends of right-hand twill followed by 2 ends of left-hand twill. This too might be called a herringbone fabric. Just like the plain weave fabric, you can vary the twill weave fabrics by using yearns of different colours. A worsted fabric made with applied colour effect called glen Urquhart or glen plaid. It is made with a regular 2/2 twill weave, and the plaid is only a colour effect.
The woolen fabric also made on the twill weave and shows a variation of the glen plaid. A worsted suiting made of twill construction, with a 1 light, 1 dark colour effect usually called sharksin. In this particular case further variety is added by arranging the twill in herringbone fashion. The novelty worsted fabric made with a colour effect on a twill weave is intended to show a design of hair-line and tricot effects.
Many further variations of the twill weaves are possible. For instance, if you'll look once more at you'll notice that the cloth is based on a combination of twill weaves. This is known as a fancy entwining twill. You'll realize that a long and through study of designing will be necessary to known and to be able to originate all the various designs.
Satin weaves
Satin weaves do not have a clearly distinguishable twill line despite the fact that it is actually present in cloth made of these weaves. The eye, however does not discern these lines on the face of the cloth. For this reason, one may speak of a satin weaves as devoid of any characteristic twill line.
The absence of the twill lines in a satin weaves is brought about by the way in which the interlacing of warp and filling is arranged. The few points where the filling is up in a warp satin are covered by the adjacent ends. The long stretches of warp on the surface will crowed together in a tight weave construction and over the few points where the filling is up.
In goods is covered with either warp yarn or filling yarn, depending on whether the weaves are warp flush or filling flush. The fine diagonal lines are not plainly visible, and to find them you must look carefully and closely at the material. Regular satin weaves repeat on as low as five ends. The order of interlacing in any regular satin weave may be found by the use of a base, or counter. This is determined by dividing the number of ends in the repeat into two unequal parts. Every end in the satin weave interlaces at some point with each pick.
There can never be two interlacings at any point on any end or pick within the confines of the repeat of an ordinary satin weave. Satin weaves are used to make brocade, brocatelle, cape or cloak fabric, cotton sateen, coverings, curtain material, damask, dress silk, evening gowns and warps, fancies and novelties, furniture fabric, jacquard fabrics of many types, runners, slipper satin, sport fabrics made of silk or synthetics, materials with striping effect, tablecloth and napkin material, tapestry, tie fabric, and other fabrics.
In textiles the word 'satin' implies a rayon, silk, or similar fabric made with a satin weave. The word sateen implies a cotton material made with a satin weave. Satin weaves give a more solid and glossier appearance on the face of the goods than any other type of weave. This explains their extensive use in the materials previously named.
The types of yarn used affect to a large extent the brilliance in fabrics made with the satin weave. Satin weave fabrics do not possess the strength of equivalent plain cloths, or even of twill woven cloths, because of the loose plain in interlacing and the length of the floats in the weave. If you hear of an 8-shaft, or 8-harness, satin, there is one interlacing in every eight ends. That is, each end interlaces once in every eight picks and makes a float in ordinary satin weaves is one number less than the number of ends in the repeat of the pattern weave. Thus, an 8-end satin weave would have a float of seven.
Unless the fabric has an extremely high number of ends and picks per inch, the long floats may pull out. To avoid this, so-called double satin weaves with extra binding points are used. Such satins, however, never have quite the same glossy even surface as a well-constructed cloth with a regular satin weave.
Basket and Rib Weaves
In a simple basket weave the warp is divided into two parts, as in the case of the plain weave, but with this difference : this basket weave is called a 2 Ã- 2 basket because the ends and picks are arranged in groups of two. In a simple basket weave the shuttle or shuttles pass twice through the same shed. Consequently, there are two picks in each shed. You seen how a simple basket weave looks on design paper. This can be varied by having three or more ends work alike. Since there are fewer binding points, basket weave fabrics are fuller and looser than equivalent fabrics in plain weave.
Basket weaves give a good appearance to certain types of fabric-monk's cloth and Oxford shirting, for example. However, the yarns in a basket weave may have the tendency to move about and become rather loose. Consequently, the material may give some trouble in sewing. Also, the strength of basket weaves does not compare favorably to equivalent plain-weaves construction. A 2 Ã- 2 basket weave is popular in hopsacking. Sample which is a suiting material made of woolen or worsted yarn. With some exceptions, basket-woven materials are not desirable for apparel since they do not withstand friction and abrasion, chafing, and wear. There is considerable call for basket-weave fabrics, however, in decorative materials such as hangings, portieres, and curtainings. Rib weaves are another development of the plain weave.
These weaves are derived from the plain weave by causing two or more successive ends or picks to weave alike. A group of yarns that where alike will form a rib in the material and are said "to weave as one yarn." The rib yarns used indicate the direction of the rib or wale in the fabric. The rib line or effect may be made to go in the either warp or filling direction. Remember the rib weaves are similar to the plain wave in working properties and that the set of yarns forming the rib is usually heavier than the rest of the yarn in the material. Warp rib weaves have their rib effect running in the direction of the filling, and filling rib weaves have their rib effect going in the warp direction.
Incidentally, rib weaves afford a chance for the use of waste or poor yarn, since the rib yarns are covered by the close texture of the yarns interlacing with them. This effect may be seen in hatband fabric, bengaline grosgrain, and ottoman. Hatband fabric is a warp rib weave because the rib effect runs in the filling direction. Simple filling fib weaves similarly repeat on two picks. A further development is corded weaves, in which the effect is strengthened by combining the rib principle with the plain weave.
Weave combinations
The number of weaves, that can be made when features of various weaves are combined is much greater. Furthermore, when you consider the various effects of differently coloured yarns in warp and filling, the possibilities stagger the imagination. No wonder, then, that new combinations are put on the market every season by our weaving mills.
A fine example of a combined weave and colour effect is the worsted bird's-eye suiting in sample. It is constructed with two ends of light and two ends of dark yarn alternating in the warp. Similarly, two light and two dark picks alternate in the filling.
Warp and filling floats, as has been shown in connection with satin weaves, cause the dark yarns to slide over the light yarns in most of the weave. Only on spots planned by the designer are the light yarns allowed to show, forming the light bird's eye that give this cloth its name. Not to be confused with the suiting is the bird's-eye diaper cloth in sample. This, of course, is all-white. The effect is formed purely by the weave. Diagonal lines of points where warp and filling interlace from the diamond-shaped pattern, and a little bird's eye of warp floats is in the center. Similar arrangements of diagonal lines and warp foats are used by the designer to form the matelasse.
Warp floats, arranged in clusters and bound by lines of tightly interlacing warp and filling, form the honey comb design in the printed fabric of sample. Don't confuse the weave effect of the cloth with the birds, which have been added later by printing. The many possibilities of design are studied by the textile designer. A great deal of specialized training is needed to understand all of them. For your present knowledge, you'll do all right if you grasp the general principles involved.
Designs that must be woven with a special loom attachment, called a dobby, are often simply classified as dobby designs, such as the one in sample. The dobby, or head motion of the loom is a mechanism that raises and lowers the harnesses which control he warp in the order planned by the designer. Ribs can be formed in the cloth by simple variations of the plain weave.
Diagonal ribs, such as the whipcord fabrics, are formed by special twill weaves in combination with a preponderance of warp over filling. These simple weaves should not be confused with the pique weaves. These, as well as the Bedford cord, sample are special fabrics of intricate construction. A simple Bedford cord design is shown on design paper. In this weave the cord is composed of four ends which weave in a plain-weave order on alternate pairs of picks. The cords are separated by two ends in a continuous plain weave.
Painted blocks signify warp risers over picks. The x-marks signify plain-weave risers that produce a sharp groove between the ends that form the cords. The plain-weave ends also prevent the cloth from slipping. When it is desired to have more pronounced cords, thick stuffer ends are introduced into the design. These ends are placed in the cords.
The stuffer ends are completely covered by the regular warp, and are held in the cloth by the filling floats on the back. The stuffer ends, however, do not interlace with the filling; hey are merely held in place for the purpose of accentuating the cords. The cords, or wales as they may by called, can be arranged high or flat, narrow or wide. The weave and the number of ends and picks per inch, as well as the yarns used for the cloth itself and for the stuffer ends and picks, all influence the appearance. In evaluating textiles, you must keep in mind that a loose construction and long floats always have an adverse effect on the resistance of a fabric to wear and tear.
But there are other fabrics that are so interact that and attempt to put them on design paper would only confuse you. We'll therefore leave the problems of presentation to the designer, and simply look at the actual construction of the fabrics. Suppose you want to make a fabric with a herringbone face. On the back of this same fabric you want a check. You can do this by weaving two fabrics in one operation.
These fabrics held together by a few binding points or binder ends. Such double cloth, or ply fabric, was very popular for coatings in former years. But modern living has little use for heavy fabrics. The trend is away from heavy fabrics, special linings, or better yet, linings fastened by zippers, are used. These can be removed or inserted as desired, and they give the garment a much winder range of usefulness. If you were to make, for instance, a filmsy curtain material in plain-weave construction, the ends and picks might slip.
Consequently, a special kind of weave, requiring doup attachments on the loom, has been developed. In the weaves that are made with doups, called gauze or leno weaves, adjacent ends cross each other and grip the picks firmly. Note how one end goes over every pick, while the end that crosses it goes under every pick. A variation, called half leno. Here an end weaving in leno fashion. The most common application of leno weaving is in marquisette. However, doup weaving is sometimes used to get novelty effects in dress goods.
Another variation in weaving, called lappet weaving, is sometimes used to produce spot effects. Each spot is made from one end, controlled by a special needle motion on the loom. The back of a fabric with a lappet effect, and the face of the same fabric.
Another method is of getting spot effects. Here a contrasting filling is allowed to float on the back may be clipped off during finishing, hence the name clip-spot, often used for these fabrics. Similar fabrics can be made by using an extra warp to form the spots. Very intricate designs can be made with a loom attachment known as a jacquard. In sample you see the face of a jacquard upholstery fabric. The back of the same fabric is in sample. You'll notice the fine, plain warp yarn and the fancy, heavy filling yarn which forms most of the surface.
Another variation of jacquard upholstery fabric is shown in sample. In this fabric weave alternates with a loose weave. The loose-weave portions appear to be raised above the tight portions. In sample you'll see a damask for table linen. This type of jacquard weave alternates warp stain and filling stain to show the design.
The most intricate designs are used in carpet weaving. A portion of the warp or the filling in these constructions is woven so that loops are formed on the cloth. These loops may be cut open and brushed in order to form a pile. Sketch shows and artist's drawing or motif for the surface design of a carpet. You'll realize how intricate the interlacing of warp and filling may be as you study sketh, showing a section through a Wilton carpet. There are many varieties of jacquard designs. We'll just look at a few more.
The texture can be in the weave and the yarn, which is in the Oriental, or Moresque, style; or the texture can be carved into an even pile surface. Still another pile carpet effect, made by alternating high and low pile, is illustrated. By now you'll be able to recognize quite a few common woven fabrics. Don't confuse them with knit good. Also, you'll understand that, even though you can easily lean to recognize fabrics, you need long specialized study to lean textile designing.
Face and back of fibres
Anybody who handles textiles, from the designer and weaver in the mill to the ultimate consumer, should know the correct manner in which to recognize and to manipulate woven materials. Certain methods are employed to distinguish the face from the back of the goods. Knowing the face from the back is valuable because it will assure proper handling of the goods in cutting, in fitting, in sewing, and in trimming.
Every woven fabric has two sides, the face and the back, or the right side and the wrong side, and you should be able to tell the one from the other where possible. The face and back of some fabrics are alike. These are sometimes called reversible goods. Duck, as you have seen in sample falls in this group as do canvas, burlap, mail bagging, and linen. With the exception of plaid-back over coating such as the cloth as in dress goods, some silks, umbrella fabric, and novelties.
Face-finished fabrics use the more attractive side for the face. These include beaver, bolvia, boucle, broadcloth, camel's-hair fabric, chinchilla, kersey, melton. Montagnac, Saxony, tree bark, zibeline, and many others. Most fabrics are made so that only one side is suited to be used as the face. Long floats, knots, and extra yarn stitching on the back usually render the back unsuitable.
In some goods, such as crepe-back satin or a rib-back satin, either side may be used as the face, though the smoother satin side is the real face of the fabric. In print goods, one side of a print is the clearer and cleaner. Cretonne, shirting prints, dress goods, and dercorative fabrics are often printed. Fabrics decorated with fancy yarns, nubs, and bright spots have that side as the face which clearly shows those effects.
A fabric with diagonal or twill lines, when held with the warp vertical, will usually show the twill lines slanting to the right of the cloth. This effect is noticeable in cassimere, charmeen, convert, diagonal suiting, elastique or tricotine, gabardine, piquetine, poiret twill, serge, car seat covers, tartan plaid, tweed, and whipcord. A few fabrics have a "left-hand twill" on the face : twill lines running from upper left to lower right. This is noticeable in denim, drill and middy twill galatea, jean cloth, nurses' uniform cloth, some cotton linings, and some cotton twills.
Some ribbed or corded fabrics have a more pronounced rib on the face. Bedford cord, ottoman, grosgrain, bengaline, corduroy, and pique are characteristic of this group. It is of particular importance to those interested in garment making that, unless only the face of the material is used as the exposed side of the garment, there may be different shade-of-garment appearance caused by a difference in colour or by a difference in design. If the sleeve, for example, is made from the back of the goods and the rest of the garment is made from the face of the goods, the sleeve will make the garment is made form the face of the goods and the rest of the garment is made from the back of the goods, the sleeve will make the garment an imperfect, or a second. The direction of the design in the material must also be considered. Stripes, plaids, checks, and floral effects should be in proper alignment and should be properly matched. If each stripe or block effect were of different colour, a matching problem would arise-all parts of a garment should match. Surface effect or texture must be kept in mind; for example, in deciding when to use a lustrous satin face and when to use a dull back-of-fabric effect. If the former is used as body of the garment, the latter may be used for cuffs, collars, lapels, and trimmings.
Fabrics with raised designs, such as sprigged dimity, dotted swiss, and flock-dotted fabric, should have the raised effect on the face of the goods. In twill fabrics care should be exercised to see that all parts of the garment have the twill serge or gabardine would be spoiled if the sleeve were made inside out and had a left-hand twill effect used for the face. Knots, blemishes of several types, press marks, flaws in weaving, and flaws from dyeing should be brought to the back of the goods, so as not to show on the face of the goods. Some knitted fabrics, such as those shown in samples, are made to simulate woven fabrics. Sometimes it is all but impossible to tell from the face of the finished goods whether they are woven or knitted textiles.
Knitted fabrics
Knitting is defined as an interloping of one or more yarns to make a fabric. Look at the sketches which show a plain-knit fabric. You'll immediately notice that it is entirely different from the plain weave you have seen in women fabrics. There are a few definitions you must learn in order to study knit goods. Wales in knitted cloth may be compared to the warp direction in woven material; courses may be compared to the filling direction in woven goods.
A knitted fabric is entirely different in construction when compared with woven fabric. Knit goods are often made from a single continuous yarn, folded into rows of loops. Each row of loops is drawn through the preceding row of loops. In such a knitted fabric, if the yarn is severed at any point, it will cause the material to ravel, and may cause the loops to give way in many directions. That is, if a loose end is caught up, the whole structure of the fabrics may disintegrate. This explains the "run" which occurs in women's hosiery when a yarn breaks.
Knitted fabric in its elementary form does no lend itself to garments which encounter wear and ear. On the other hand, dependable textures are attained, since every loop is connected to its neighbour above, below, and at either side. Thus elasticity, despite friction and chafing is found in knit goods, as in knitted underwear fabric. To determine the best loop for specific knitwear, there are the horizontal and the vertical factors to consider.
In general, the loop should be symmetrical in form, and it should cover about the same space in both horizontal and vertical directions in order to give an even balance. For some purposes, however, a loop may be elongated to cover more space vertic1ally than horizontally. Care should be exercised in selecting a yarn for knitting that is not too fine in diameter for the set of loops. If the yarn is too fine, the fabric will be loose, irregular, and unstable. There will be an elongated appearance and a lack of balance in the goods. On the other hand, a thick thread will give an irregularly spaced and congested type of goods in which the elasticity will vary. Consequently, care must also be exercised in inspecting the yarn for thick threads.
A loom may weave various fabrics : bulky, coarse, fine, or sheer. Wheaving, as you know, involves two sets of yarns: warp and filling, interlacing at right angles with each other in a flat plane on the loom. The number of ends and picks per inch, or thread count, is very important in woven fabrics. In knit goods, of course, there is nothing you can compare exactly to the thread count in woven goods. However, in descriptions of knit goods you'll often find the term gauge used. You'll hear that a high gauge is used to produce fine or sheer fabrics, while a low gauge is used to knit coarse or bulky fabrics.
The word gauge stands for a unit of measurement. In flat knitting, such as in full-fashioned hosiery, the word gauge refers to the number of knitting needles in 1½ in. That is, gauge refers to the needle spacing on the machine, and it determines the fineness of the fabric. A gauge of 60 would mean that there are 40 needles to the inch in the knitting machine. The higher the gauge of stocking, the higher will be the number of needles per inch. On circular machines, the thickness of the needle determines the gauge. Fineness of circulr-knit fabric is expressed by the total number of needles in the cylinder, and by the cylinder diameter.
Knitting can be done more rapidly than weaving, and it is often cheaper, because in knitting, a number of yarns may be fed into the machine simultaneously. Thus, if 8, 24, 40, or any number of yarns are fed into the machine, the higher the number of feeds, the greater will be the production.
Compare a knitting frame with 24 feeds of yarn with a loom in which one pick at a time is woven, and you will understand that there are actually 24 machines combined into the one knitting frame. Another item to be considered in knitted fabric is that in loop formation the thread is subjected to considerable strain, which axes the elasticity of the yarn. Too much strain will result in poorly knitted cloth.
Sometimes, however, this may be alleviated by the fact that the passage of the yarn between the needle and the sinker in knitting is oblique, not straight as is the case when the ends pass through the loom in weaving. Proper yarn lubrication may also be of value in overcoming irregularities in the yarn being knitted. Double work in knitting consists of running two yarns where one would ordinarily be used. Fancy effects are obtained in double work by running two colours instead of one. The tendency is for one yarn to twist around and other, there by making fancy effects.
Just as there are different weaves in weaving, there are different stitches in knitting. Various types of needles are used to produce these stitches. One needle that is very common is the spring needle. The spring needle is mostly used for fine fabrics. Another type of knitting needle is the latch needle. This type of needle is used mostly for coarse fabrics. The latch of this needle swings loosely on a rivet in a hollow part of the needle, called the cheek. Again, the names of the needle parts are given in the legend of the illustration. A third type of needle, the tubular, is used in warp knitting on some machines which make very wide fabrics. This needle allows a very high production. Since we only want to get a general idea here, we'll not go any further into special idea here, we'll not go any further into special types of knitting needles. Instead we'll see how the needles are used in the formation of loops.
Plain knitting stitch is commonly used for thin and sheer fabrics. Notice that the tops and bottoms of the loops are always on the back of the fabric. In another common stitch, the purl stitch, this procedure is reversed. That is, the face, of knit goods made with the purl stitch interlaces like the back of the plain fabric. You'll note that is causes successive courses of loops to be drawn to the face of the fabric. The purl stitch is sometimes called links-and-links. This is derived from the German work links, meaning left. In that language the face is called right and the back is called left, so links-and-links really means that the purl stitch looks like the back of the plain stitch. The surface appearance of the plain-knit stitch is quite different from that of the purl stitch. Therefore, many different designs can be made by combining the two stitches. It alternates one wale of plain stitch with one wale of purl stitch. This stitch produces lines of wales on both sides of the material.
There are many other knitting stitches besides the plain stitch and its derivatives, which you just studied. One stitch which is very common is the truck stitch. In this stitch there is one wale of the plain stitch alternating with a wale in which the needle holds one or more loops and then cats them all on the next loops. The face of the goods has a gridiron or honeycomb appearance. The knitting stitches used for special fabrics, such as run-resistant fabrics, tricot, and so on, are very looking at a diagram of such stitches would make you dizzy. You could not understand it without a special study of knitting. Still further variations are possible by letting the knitting needle form several loops at the same time. That is, several yarns run parallel, just as in the basket weaves in woven fabrics. Knit stitches made in this manner are called plaited stitches.
Full-fashioned hosiery is knit on a flat knitting machine. It is shaped during manufacture by an inward transfer of the loops from the selvage. Since full-fashioned hosiery is woven flat, it can be recognized by the seam up the back, which extends from top to toe. Another characteristic is the fashion marks, or narrowing marks, which appear as small dots in the leg and foot adjacent to the seam. Most full-fashioned those are made with the plain stitch. The leg is made uniform in width down to the calf, where the narrowings are performed to the rate of diminution required.
The greatest labour and ingenuity, however, must be used when the heel is reached. It is necessary to work the heel in two sections at each side. Full-fashioned type hosiery may be made at the heel in a rather square shape, and of any convenient size, by enlarging or contracting the heel portions. This type of heel is called the English heel. It can be recognized by the seam which always occurs along each side of the foot and down the back of the heel. In the French type of foot, which is more common, the seam occurs along the center of the sole of the foot.
The French style is ideal when clocking or embroidered patterns are to be worked into the article, and there is also a saving of time in making this type heel. The upper and the lower portions of the foot are made in one width and afterwards are folded over with only one seam along the middle of the sole of the foot. In seamless, or seam free, hosiery the fabric is knitted circular. The entire stocking can be made on one machine, ready for finishing. Seamless hosiery is recognized by the absence of fashion marks.
However, there is a type of hosiery called mock-fashion hosiery. This is made from seamless stockings which the sewed up the back to give them a full-fashioned appearance. Like the seamless hosiery mock-fashion hosiery is usually priced lower than true full-fashioned hosiery. The full-fashioned hosiery keeps its shape better than the seamless types. The narrow places at the ankle of seamless stockings are formed only by having the fabric shaped, or set, after knitting, rather than by having the fabric actually knitted narrower.
Socks are stockings that are not full-length. That is, they do not go over the knee. These include the ankles, the short socks which come to just below the calf of the leg, and the full-length socks which reach above the leg calf. There is another group, called golf or leisure-wear socks, which are really 5/8 and 7/8-length stockings and are made for men, misses, and children. Most socks are made on circular-knitting machines and comparatively few are produced on full-fashioned knitting frames. Socks usually have a single fabric cuff portion which is made of rib-stitch fabric, but the body is plain knit.
The rib cuff is made as a continuous cuff section on a separate rib-knitting machine, with a cylinder diameter or needle count corresponding to the body of the machine. The cuffs are separated and transferred, stitch, to another machine which knits he leg the foot portions. Less expensive socks have the cuffs sewed to the leg. The lowest-priced socks have an automatic top, that is, a cuff made by a form of rib knitting on the machine. This arrangement knits the entire sock in one operation. Rubber yarns are often incorporated into the fabric. These produce an imitation rib fabric which processes ankle-supporting and leg-hugging qualities.
Misses' and children's socks and anklets often have a longer doubled-over fabric portion at the top. This is, in turn, folded down again in the finishing, producing the fold over-cuff socks, as against the regular stand-up-cuff types. The same is often true of golf socks made for men and boys. These usually have a ribbed fabric cuff which, when worn in folded position, brings, the height of the socks to just over the calf in the 5/8 length and immediately to the knee joint in the 7/8 length. Regardless of the types or the style, practically all socks are made to foot sizes. These present the length in inches from the outer center of the toe fabric to the outer fabric of the heel, when the sock. It is merely a separate and washable absorbent shoe liner made of knit fabric for use with bare-leg or stockingless costume.
Knitted underwear includes fabrics which are worn under clothing and next to the skin. It does not include cardigan jackets, sweaters, and comparable fabrics or garments. Knit underwear fabric must be elastic and have considerable yield with the body movements; it must be hygroscopic and hygienic, more so than other knitted fabrics. Contraction and shrinkage of knitted fabrics and garments must be given close consideration. Combined contraction and shrinkage is caused by the formation and by the yarn composition.
Ordinarily, knit fabric will contract when released from the knitting machine. The openings or interstices of the loops caused by the needles and sinkers allow the material to contract in both length and width. Contraction and shrinkage on circular machines is greater than that encountered on straight-bar machines. In theory of the full width of a fabric as it comes from the machine should be equal to the circumference of the machine.
The fabric, however, is made on a needle circle in the machine and the actual width of the goods is practically only 2/3 of the theoretical width. If the material is afterwards boarded out to a greater width, the extra width will be lost the first time the garment is laundered. Underwear may be made from flat, knitted web which comes in lengths wound up on rolls, and which is finished. It can also be cut from circular-knit or full-fashioned fabrics, in which case allowance must be popular. It allows net measurements to be used.
Furthermore, the finished web lies flatter, and will not have the tendency to curl, as it does in the cut circular-knit or full-fashion fabrics. In these later fabrics the respective parts, when being made into full-fashioned garments, must be salvaged to shape. Seamless underwear is made on flat knitting frames and is finished after the making up.
Knitted fabrics for the coating trade appeared in the United States about 1915 and steadily increased in popularity. At the present time, a large percentage of fleece coatings sold in both the men's and women's wear fields are knitted fleeces. The knitted fleece has several advantages over the woven fabrics. The knitted fabrics give better wear and greater warmth for the same weight, and because of their construction, they have an ease of wearing not obtainable in the woven garment. The wool and hair fleeces knitted on a cotton back also produce a fabric of luxury at a price that could not be duplicated in a woven fabric.
On the other hand, the knitted coating is more likely to get baggy. Also, because the back is often unsightly, it must be lined throughout. In surface appearance, the coat made from a knitted fabric cannot be distinguished from any other fabric by the layman, and many consumers never realize that their fine coat was made from a knitted fabric. Originally, only the heavier type fleece coatings were made on knitting machines, but late developments have brought out lighter-weight fabrics in both smooth and rough finishes.
Another development in the knitted and 50 per cent cotton back, contains 50 per cent cotton back. The Government has recognized the advantages of the knitted construction furs and moutons are being produced that are difficult to distinguish from the genuine; There are two types of circular knitting machines used to produce coating fabrics. The spring-needle machine is the original types. The second type is the latch-needle machine which is coming into wide use because of its faster production and greater pattern possibilities.
Success of the knitting mill is very dependent on knowledge gained through trail-and-error methods in finishing. The fabric comes off the machine in tubular form. After fulling-that is, shrinking under pressure in hot, soapy water-the tabular cloth is cut, and the wide fabric goes through the other finishing processes. The gray weight of knitted coatings is normally heavier than that of woven fabrics for the same finished weight. The head shrinkage is also more and will usually average at least 20 per cent. The gray width is about one-third greater than in woven fabrics.
Any finish applicable to woven fabrics is usually suitable for knitted coatings this applies to water repellency. Shrink proofing, mothproofing, resin treating and so forth. In the manufacture of knitted fabrics, new methods are being adopted continually. New end uses are being found for the product, and great improvements are being made in the fabric itself. The possibilities for the end uses of these fabrics are only limited by the ingenuity of the knitting-mill technologies.
Colouring
The knitting machine permits flexible control of the individual or multiple yarns and of the fabric-forming members, or knitting needles. Fancy effects or motifs can be produced in a great variety of colour flashes, or by the variations which are possible in the basic fabric stitch. Continuity of design, reversals, or intermittent repeats with plain or pattern combinations are characteristics or knitting techniques, particularly with weft knitting machines.
Small allover pattern repeats in the predominantly vertical motifs are more the work of warp-knitting machines. Colour patterns in weft-knit fabrics, other than simple horizontal stripes, and produced by plaiting one yarn simple horizontal stripes, are produced by plaiting one yarn over another. Certain yarns are made to appear on the face of the fabric, but others are knitted to the back of the goods. This plan can take place from needle to needle of from course to course, and it can be alternated when reverse plaiting is desired. Examples of this technique are the two-colour fabrics which have a face of one colour and a back of another colour.
Imitation Argyle socks are made by plaiting in which the diamond effects are formed by reverse plaiting. Colour patterns in knitting may result from the use of differently coloured yarns with the same dye properties or from the use of yarns which can be cross-dyed. Very often the plaiting process is used in conjuction with tuck stitches to produce still more pronounced fabric effects. Other patterns are produced in weft knitting by floating, which is forming is forming loops of one yarn upon certain needles while another yarn is carried in a nonknitting position past those needles which are knitting the first yarn. This second yarn is caught subsequently and knitted into face loops by other pattern producing needles. By the used of this technique, the floats on nonkint yarn appear on the back of the fabric, which is usually of plain-knit stitch.
Eyelet or lace effects in knitting are made by keeping yarns off some needles, as in the case of the end-out warp knitted fabrics. They can also e produced by needles out of play, by nonknitting needles on circular machines, or by loop transfer on full-fashioned machines. Tuck stitching, which is holding loops upon a needle from one to eight courses, also produces a holelike effect in knit fabric. Clocks and other decorations are sometimes used in stockings. They are supposed to have been sued first to cover up a seam. Clocks may be embroidered by hand or by machine.
Lace clocks, such as Paris clocks, can be made in the knitting process, or they may be made by a process similar to drawn-work thread. In this last type of clock, the threads are dropped, forming a ladder effect which can be hemstitched on both sides. Clocks should branch out at the lower end. In the lower-quality stockings, this is not always the case, and it may show up when worn with low shoes.
Braiding
In braiding, the yarns are not interlaced at right angles, as in weaving, nor are they looped together, as in knitting. Rather, the yarns are connected by twisting, by entwining, or by knotting them together. Braiding of a little girl's hair in to a pigtail is a simple example of the principle of braiding. Of all plaited and braided fabrics, lace is the most important. Commercial braiding and plaiting are usually done by machine in mills, whether the material is shoelace or lace tablecloth. The following sentences explain the differences among the various methods of making braided or plaited fabrics. In crocheting, separate loops are thrown off and finished by hand successively.
Netting consists of knotting threads into meshes that will not ravel. Chinese-type lace and fish net have a knot at every intersection. Knotting is done through actual knotting of the parts of one or more threads so that they will not slip or loosen. Tatting is used to make banding, edging, or insertion which is lacelike in formation in the finished condition. It done by means of a small shuttle. All these methods may be carried out either by hand or by machine. In the making of braided or plaited fabric, a single yarn could theoretically produce the material, since the yarn is made to interlace, entwine, and twist in several directions. More than one yarn, however, is used to make lace by machine. The action is like that of the several feeds of yarns entering the machine used to make knitted or woven fabrics.
Lace
Major laces of today include curtain and table laces, filet net, novelty effects, combination effects, and rough-weave and shadow weave effects. Lace has been with us for a long time. A crude form of meshed cord for ornamentation was used in Peru over 4000 years ago. Ancient Egypt used a form of lace to cover mummies as far back as 2500 B.C.
The history of lace making further reveals that it was made in the early Christian era, that its use increased greatly in the fifteenth century in Italy and Flanders, or Belgium and parts of France and the Netherlands. After this time, fashions and styles changed as the growing industries made people wealther. England, Frace and Italy began to use considerable amount of lace on clothing.
Lace was used in a lavish way; men used lace cravats and lace cuffs and collars; even their books were trimmed with lace. By the eighteenth century, lace was common all over Europe, and its used reached the heights of extravaance. Handmade lace is now made in Austria, Belgium, China, France, India, Ireland, Italy, and Syria. The lace is the result of long, tedious, trying work, which therefore causes the price to be rather high. Handmade dress flounces, for example, may range in price from about ten dollars to about four hundred dollars a yard.
There are four types of handmade or real lace. Needlepoint lace is the most expensive and most difficult type of lace to make. It is made with a needle. The first step is to sketch the pattern on parchment, which is then stitched down upon two pieces of linen. The thread is then laid on the leading lines drawn on the parchment and fastened to the parchment here and there by stitches. The solid parts are filled in by the needle with buttonhole stitching. The meshes, or ties, are manipulated so as to link the different parts into the one fabric.
A knife is next passed between the parchment and the linen, thereby releasing the completed lace. One variety of needle-point lace is called Alencon. The name comes from the city of France where it was first made. Birds, Flowers, and other motifs form the background of Alencon. The groundwork of this lace is hexagonally shaped in mesh construction of double-twisted thread. Venetian point lace has floral patterns in which the design is marked with regular open-worked vine effects. Rose point resembles Venetian point lace.
Bobbin lace is made on pillows, and so is often referred to as pillow lace. A twisting and plaiting action brings the threads into the motif. The pattern is first drawn on a piece of paper and pricked with holes which determine where the pins shall and pricked with holes which determine where the pins shall be placed for guiding the thread. The pattern is then fastened to a pillow. The end of each thread is held by one of the pins. A small bobbin holds the thread supply. The lace is formed by throwing the bobbins over and under each other, so that the threads are plaited about the pins to form the fabric. One variety of bobbin lace is uncut-thread lace. This variety of single-piece lace includes Binche, Cluny, malines. Old Flanders, point de Lille, point do Paris, common torchon, and Valenciennes. The meshes are hexagonal, round, or square. From these types the motif is developed. Heavy outline threads are employed to set off the design.
Another variety is the united lace, in which individual details are combined to give the finished fabric. Black and white Chantilly, blonde, and Bruges duchesse, and Brussels duchesse are the more popular types. Relief motifs are a feature in these laces. Coarse Flanders and point d' Angleterre laces are made from a combination of needle point and bobbin lace. The latter term was originally used for very fine Flemish lace of the eighteenth century.
Crocheted lace, sometimes called Irish lace, is made with a crochet hook. It is not as fine in texture as needle point.
Syrian lace resembles Irish crocheted lace and is used chiefly for handkerchiefs. Darned lace is made with a chain stitch that outlines the motif on a background of net or some other suitable fabric. In the variety called antique, a heavy linen thread is used in a large, rectangular-knotted mesh effect. Filet lace has square mesh in which the patterns are made with animal and tree effects.
Some of the most beautiful and intricate handmade laces have for centuries bee made in convent schools throughout the world. This work is exceptionally fine in detail and superb in motif. Machine-made lace came into being because of the great demand for lace.
The famous Nottingham lace machine has the following features: Patterns are made on the principle of the cards used in weaving jacquard designs in woven fabrics on a jacquard loom. A warp is used the same as in making woven fabric on a loom. Separate spools furnish yarn in different quantities, as required by the motif. There is no filling yarn employed in the strict sense as is used in making woven cloth. Fine yarn is would on small brass bobbins and set in frames known as carriages.
It darts back and forth, spiraling around so as to tie in the warp yarn and yarn from the spools used for the motif. Tensions on the machine must be carefully watched for tautness or looseness, of the fabric. The Nottingham machine is 30 feet wide and the frame may be divided to make eight or ten curtains at the same time. Each fabric is controlled by the jacquard head motion for motif and accuracy.
Machine-made laces are divided into
- Oriental lace, which is fine net, made with a heavily embroidered edge;
- Princess lace, which is made of machine braid on a machine-made net and put together by hand; and
- Shadow laces, which have a fine-mesh ground in which shadowlike patterns of finer mesh are seen.
There are irregularities in handmade laces, Since the patterns do not repeat in Perfect order. Insert a pin into threads of the pattern of machine-made-lace, and observe that it is possible to slide the threads back and forth. This is not possible in handmade lace. Lace may be made from linen, cotton, and silk; also from nylon and other synthetics. If you study fibers and yarns, you'll be able to distinguish one from the other.
Non woven fabrics
The Fabrics you have studied this far have differed in many respects. There were heavy rugs and wispy laces. There was stiff duck and elastic hosiery. All these fabrics hand one thing common : every one of them was composed of yarns. You'll have to consider still another group of textiles: those fabrics that are changed directly from loose fibers into a fabric, without spinning the fibers into yarn. For want of a better term, textile technologists call them the non woven textiles. You must understand that his term refers only to fabrics made from yarns. The non woven textiles can be subdivided into two classes : Felt is made from wool and similar fibers.
The physical structure of these fibers can cause them to interlock tightly under certain conditions. Felt has been used for many purposes since ancient times. Their construction is based on the fact that certain synthetic fibers melt when heated. Just below the melting point, the fibers become sticky or tacky. You can therefore fuse, or bond, the fibers together by a suitable heat treatment. The felt industry uses wool fibers, also fur fibers.
Let's first look at the manufacturer of wool felt. Suppose you spread wool fibers in a nice, even layer, somewhat like batting. Then you add a thick solution of soap and warm water, or a similar substance. Finally you stamp around on the layer of squashy wool with your feet or you beat it with a wooden mallet. During this time the soapy water, has opened the scales on the wool, and so they will act like tiny bards. Every time you press the fibers down, they move a little, but the barbs don't allow the fibers to return to their original position after you remove the pressure. Eventually, the fibers becomes so mattered together that you have a compact piece of felt instead o a layer of loose fibers. In modern industry, machines are used to make felt. The wool is spead into even layers by carding. Fulling mills are used to felt the wool. Finishing processes are used to improve the felt fabrics. But the basic principle of felting is identical in all processes.
Wool felt is used for a wide variety of purposes. Fine wool felt can be made so thin that it can be used for kisses' skirts. Since there are no yarns that can ravel, such skirts are very easy to make. The felting power of wood is so great that it holds the fibers together even when re-used wool, waste cotton, and other low-priced fibers are mixed with it in inexpensive felts. Such felt are used for carpet cushions, and in industrial shocks absorbers. An interesting variation or felt making is the production of felt from fibers for use in hats.
The prolific rabbit produces most of the fur fibers for this purpose, but beaver, nutria and other furs can be used too. The tiny barbs on these fur fibers are tightly closed, and must be opened by means of chemicals. This process is called carroting. In former days mercuric nitrate, a poisonous chemical which affected the brain of the worker, was used to open the bards. Hence the saying "as mad as a hatter". Today harmless chemicals are used for carroting, and the hatters are just as sane as other skilled craftsmen. Practically all felt made from fur, and much wool felt too, is used by the hat industry.
The felt bodies for hats are made in plants called back shops. Their functions are parallel to those of the clothing industry, which readies the product for the consumer. About six million hat bodies are produced every year in the United States. In some hats a hard finished is desired, especially in the brim. This is achieved by putting shellac solution into the felt, a process that really combines felting with bonding of the fibers. In some instances the different techniques of making textiles are intermingled. For instance, you can take woven woolen fabrics and then felt them in a fulling mill until the fibers are matter together. The result is a woven felt which combines the strength of woven fabrics with the cohesion of felt.
Bonded fabrics
Manufacture of bonded fabrics has not yet reached proportions that allow a full evaluation of their possibilities. In properties and appearance the bonded fabrics occupy a place between paper and textiles. Most of the bond fabrics manufactured today are prepared by producing a web of fibers on a card. The web can be held together by applying adhesive, that is, suitable plastic or glue, in narrow stripes or other suitable patterns.
Another method is asutogenous bonding, where the fiber itself is treated to become tacky and to stick together. Some fibers such as rayon, can be made tacky by treatment with acid. Bonding is then followed by compressing the web, washing, and drying.
Other fibers, such as acetate, can be bonded by simply applying heat and pressure. If you take a piece of acetate fabric and carefully apply a very hot iron, you'll notice that the fibers become tacky and stick together.
Many bonded fabrics can be laundered and dry cleaned. However, the fabrics are relatively inexpensive, and their major use seems to be in the production of disposable items. Bonded fabric are used in disposable napkins and tablecloths, shoepolishing cloths and dustcloths filters, bandages, and decorative ribbons for wrapping gifts. As further technical advances are made, the uses for bonded fabrics may expand.
Automatic Weaving Machine
Use of high performance textile structural composites is becoming increasingly popular in many engineering applications. Examples include aerospace and aircraft structural components, deep submergence vessels, sports equipment, textile machinery and automotive parts. The rate of growth of composite use is expected to continue to increase rapidly with new developments in fibre and matrix materials and manufacturing technologies. Fibre reinforced composites basically consist of two fundamental components; the reinforcing fibres and the surrounding matrix.
Technologies for the manufacture of the reinforcing fibrous performs include a number of conventional textile processes as well as several speciality techniques developed mainly for the composites industry. Laminating several layers of a woven fabric, cross-laying of tapes of continuous filaments or filament winding the fibres into the required shape were most common in the late seventies and early eighties. However, because of failure by delamination of the these materials, several systems of producing three-dimensional integral shapes have been developed over the last decade.
The new textile systems include 3-D weaving and 3-D Knitting. Other systems were developed especially for bodies of revolution or for the manufacture of billets which have to be machined to the required shapes after consolidation. Recently stitching multiple layers of multiaxial warp knitted 2-D fabric into 3-D shapes has improved the availability of structures with several fibre orientations as well as enhanced damage tolerance. Considerable development work is taking place in industry, research institutes and universities to automate 3-D braiding machinery using the 2-step and 4-step proesses.
Developments in 3-D weaving of net shapes have not been given sufficient attention by the industry. This lack of activity was the driving force behind the effort which will be described in this paper. Composites made wit 3-D integral structures woven or braided into net shapes offer considerable advantages over laminated composites.
The properties which made composite materials so attractive include their high specific strength, high specific modulus and low thermal expansion coefficient among others. However, the high cost of advanced composites has limited their use mostly to space and military applications, where the performance of these materials has been unmatched by metals.
3-D weaving processes
Three-dimensional fabrics not only have three-dimensional shape, but also have yarns in three or more directions. Multi-layer woven fabrics have been used for a long time in industrial applications, particularly in belting and webbing. Multi-layer fabrics are composed of several series of warp and weft yarns which form distinct layers, one about the other. Binding the layers together can be achieved by many ways, either by interlacing warp ends in the structure with the weft of adjacent layers (referred to an angle interlock), or by having ends interlace between the face and back layers (warp interlock).
The binding yarns may also interlace with the weft vertically up and down between layers producing an orthogonal weave. This system usually involves insetting the weft on pick at a time, which requires moving the fabric up and down, during beat-up, to achieve the desired thickness. The loom can be adapted to weave three-dimensional shapes by the proper arrangement of the warp.
The density of the structure is limited by the need have sufficient distance between the yarns to accommodate the means of inserting the weft and Z yarns. The patent described the production of structures with rectangular cross section only and did not describe the formation of 3-D net shapes. King invented a different method of forming three-dimensional structure.
In this method, the Z axis yarns, which are rigid rods made of a self supporting material, are vertically oriented and positioned passing through holes in the upper frame and resting in mating recesses in the upper surface of the lower frame. The X and Y axes filament feed units are essentially identical. They insert the X and Y filaments by advancing parallel, equally spaced needles alternately. The X and Y yarns are doubled and are inserted leaving a loop at the far outside edge of the Z axis filaments.
The selvage (fabric edge) is formed by pins which hold the X and Y axes yarn loops during insertion. The pins may be removed as the filament layers building. After sufficient layers have been formed, it is suggested (but not necessary) to compress. The fabric along the Z axis by lowering the upper frame. Again, this method is used to produce only structures with rectangular cross sections. The patent also describes a different method to produce cylindrical shapes.
Mohamed et al. described an automated, computer controlled machine designed to weave 3-D orthogonal structures according to the method described above. Warp yarns taken from bobbins on a creel are separated into layers to allow for weft insertion. In this case there are more than one layer, and thus more than one shed. These warp sheds are fixed open. Multiple weft yarns are inserted through the sheds by needles. The Z yarns are fed into the machine parallel with warp yarns and separated into two layers controlled by harness. When the top Z yarn layer is moved to the bottom and the bottom Z yarn is moved to the top a vertical component of yarn is added.
The weaving process can be described as follows: several needles containing doubled weft yarns are inserted horizontally through the sheds in one motion. The weft yarns can be inserted simultaneously or alternately and from one or both sides according the cross-sectional shape. The weft yarn loops are temporarily held on the opposite side by a vertical selvage needle. The insertion needles are then withdrawn to their original position leaving behind a set of doubled weft yarns.
The selvage needles are lowered and the formed structure is then "taken-up", that is, moved a distance corresponding to the required spacing of the weft yarns. The need is then moved back and the entire cycle is repeated. This process lends itself to continuous production of long structures. The yarn supply is from bobbins on a creel behind the machine. The tensioning of the warp and Z yarns is achieved by weights applied to the yarns individually. The layers of warp yarns are drawn through the reed in a formation similar to the shape being produced. Weft yarn tension is controlled both passively and actively and varies throughout the weaving cycle. All the motions are pneumatically actuated, with the exception of the take-up action. This simplified the design of the machine and eliminates the need for drive motor which could have a high risk of being shorted when weaving carbon fibres.
Double acting air cylinders controlled by solenoids are used for weft insertion, reed, harness and the selvage needle movements. The reed movement is controlled to the linear and perpendicular to the insertion direction. The linear motion is necessary to ensure the vertical placement of the Z yarns. A step motor is used to turn a threaded rod causing the linear motion effecting fabric take-up. A microprocessor using a simple programme, written in BASIC controls the timing of all the movements and the amount of take-up. To control the neatness of the edges, the selvage yarns are knitted through the weft loops.
The control system of the 3-D automatic weaving machine consists of a microcomputer, a control board which is connected to the computer with an interface card, solenoid air valves, a step motor, and pneumatic cylinders. Any micro computer should be able to accomplish the control job, because of the availability, an IBM compatible 386/16 personal computer is used for the machine. An AC5 parallel interface card is used for digital input and output. This caM enables the PC to communicate with OPTO 22's PB24 mounting rack, which can accommodate up to 24 single channel 1/0 modules.
One channel is used for checking on/off status of the control switch to cause the machine to run or to pause. Two channels are used for the operation of the step motor. The control programmes are written in BASIC language and are stored in either a floppy disc or a hard disc. Depending on the dimensions and the cross-section of the perform to be woven, an appropriate programme can be loaded to run the machine. The parameters and the programmes themselves can be modified to meet different weaving requirements. The machine speed could be controlled by changing the corresponding parameters in the programmes. Control of the pick density is by means of the number of steps made by the take-up motor.
