Fabric Club Of BD: 2011

INTERLOCK STRUCTURE

Labels: Knitting Manufacturing Technology | at 8/25/2011 09:30:00 PM

Interlock structure

Interlock has the technical face of plain fabric on both sides, but its smooth surface cannot be stretched out to reveal the reverse meshed loop wales because the wales on each side are exactly opposite to each other and are locked together (fig). Each interlock pattern row requires two feeder courses, each with a separate yarn that knits on separate alternate needles, producing two half-gauge 1 x 1 rib courses whose sinker loops cross over each other. Thus, odd feeders will produce alternate wales of loops on each side and even feeders will produce the other wales.

Figure. Interlock fabric structure.

►There are TWO type of needle arrangement in circular machine.

►When the needle heads are offset with each other, it is called rib gating e.g. 1x1 ribs, 2x2 ribs.

►If the needle heads are facing with each other, it is called interlock gating, e.g. interlock fabric

Construction of interlock stitch

A knitted fabric is obtained which is characterized by situating loops of one course in every second wale, as these loops are formed on every second needle. Loops of the next course are also situated in every second wale, formed on needles that had not formed loops in the previous course. Thus loops of consecutive courses, formed in every second wale, are shifted in relation to each other by half of their height. An example of the stitch construction described is shown in Figure.

Figure. Warp-knitted interlock stitch.

A group of knitted fabric stitches produced according to the above-mentioned technology may be referred to as warp-knitted interlock stitches, as they are similar to the weft-knitted interlock stitches. The loops of one stitch are situated between loops of the other.

Anticipating the merits of some end-use properties of fabrics with the new stitches, the relationships between the structure of these stitches and some of their end-use properties are to be examined. The features of warp-knitted interlock fabrics have been compared to warp knitted fabrics with stitches applied so far.

An analysis of the production method of knitted fabrics according to the proposed technology led to the observation that warp-knitted interlock stitches can be obtained on warp-knitting machines with latch needles, equipped with a tuck presser.

Figure. An example of the warp-knitted interlock stitch, produced on a warp-knitting machine equipped with a tuck presser.

Machine requirement for interlock knit fabric

►Interlock fabrics are mainly produced on specially designed circular double jersey machines called interlock machines.

►They are high speed, multi-feeders with closed cam track machines.

►The common gauges for interlock fabrics are 20-24 npi, using 1/30 Ne cotton or 1/48 Nm worsted yarns.

►Worsted interlock is for ladies’ winter suiting fabrics. For those 28 gauge fabrics, the yarns used are mainly textures polyester of 75 denier.

CAM

Labels: Weaving Manufacturing Technology | at 8/21/2011 04:42:00 PM

Cam mechanism

The transformation of one of the simple motions, such as rotation, into any other motions is often conveniently accomplished by means of a cam mechanism A cam mechanism usually consists of two moving elements, the cam and the follower, mounted on a fixed frame. Cam devices are versatile, and almost any arbitrarily-specified motion can be obtained. In some instances, they offer the simplest and most compact way to transform motions.

A cam may be defined as a machine element having a curved outline or a curved groove, which, by its oscillation or rotation motion, gives a predetermined specified motion to another element called the follower. The cam has a very important function in the operation of many classes of machines, especially those of the automatic type, such as printing presses, shoe machinery, textile machinery, gear-cutting machines, and screw machines. In any class of machinery in which automatic control and accurate timing are paramount, the cam is an indispensable part of mechanism. The possible applications of cams are unlimited, and their shapes occur in great variety.

The transformation of one of the simple motions, such as rotation, into any other motions is often conveniently accomplished by means of a cam mechanism. It is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice versa. A cam mechanism usually consists of two moving elements, the cam and the follower, mounted on a fixed frame. Cam devices are versatile, and almost any arbitrarily-specified motion can be obtained. In some instances, they offer the simplest and most compact way to transform motions. A common example is the camshaft of an automobile, which takes the rotary motion of the engine and translates it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders.

A CAM has two parts,

► The FOLLOWER

► The CAM PROFILE.

Fig 1: CAM WITH NOMENCLATURE

TYPES OF FOLLOWERS

There are different types of follower but they all slide or roll on the edge of the cam.

Follower Configuration

1. Knife-edge follower (Figure 2a)

2. Roller follower (Figure 2b, e, f)

3. Flat-faced follower (Figure 2c)

4. Oblique flat-faced follower

5. Spherical-faced follower (Figure 2d)

Fig 2: TYPES OF FOLLOWERS

THE CENTRE SHED JACQUARD MECHANISM

Labels: Weaving Manufacturing Technology | at 6/29/2011 10:24:00 PM

The centre shed jacquard

As the title suggests, the centre shed jacquard machine is built to produce a warp shed on the closed & centre shedding principle. It consequently merits all the advantage which characterizes this principle of shedding, but it also inherits all its defects.

A centre shed jacquard is very suitable for use in weaving figured gauzes where one or two dopes are placed in front of the harness mounting.

The chief details of mechanism in the centre shed jacquard are supplied in fig: 1; which is a line diagram, showing one row of upright and needles, together with a vertical section through the griffe blades and upper and lower reciprocating boards. A indicates the top and usual griffe bars’ the resting or suspension hook board free to rise or fall. The griffe A is connected to the spindle C at the position D and the board B is similarly connected to the second spindle E at the position F. The uprights are shown at G and the cross wires or needles at H. The usual card cylinder, needle board and spring box are also indicated.

Fig: 1

The diagram is painted and the cards cut in the usual way. There are two jacquard cross heads K and L and two head levers and reciprocating rods and a double throw eccentric as in double lift machines, but the eccentric is set screwed fast to the crank shaft, so that as the cross head K rises and falls, the cross head L falls and rises once for each pick of weft or revolution of the crank shaft.

Action of the mechanism

The crank shaft of the loom revolves as usual once, for every shot of weft. The cross head K raises with the spindle C and griffe A with all the hooks G that have been left over the griffe knives, according to pattern, to from the top warp shed. Simultaneously the cross head L with spindle E descends together with the bottom board B supporting all the hooks G that have been left clear of the top knives in griffe A ,according to pattern , to from the bottom shed. Then the weft is inserted and the griffe A descends whilst B ascends until the uprights G meet in the centre, irrespective of the position which they are to occupy on the next and succeeding picks of weft. The operation is similarly repeated for each shot of weft.

NOTE: In the given diagram the shed is fully opened.

DEVOGE'S CROSS BORDER JACQUARD

Labels: Weaving Manufacturing Technology | at 6/23/2011 12:36:00 AM

Devoge’s cross border jacquard

This machine is a double acting, double cylinder jacquard but for cross borders is worked as a single cylinder machine with either cylinder at will. Fig: I is a diagonal representation of the mechanical details employed for locking and detaching either cards cylinder by hand to suit the requisite length or number of repeats of pattern for either sets of cards.’

A is the reciprocating rod operated from an eccentric on the crank shaft of the loom; B is a stud connecting the rod A with a lever C s crewed to the shaft D which extends across the length of the machine and near its base. B is a lever set sewed at right angles behind C to the same shaft D. An adjustable stud F combines the lever E with the link G which in turn is adjusted through the stud H to the lever I pivoted at J.K and Kꞌ are two studs set equidistant from the common fulcrum J.L is a connecting arm pivoted at K. Near the free end the arm L a special socket M is

Fig: I

Formed, which is free to lock as required with a suitable formed stud N, securely fixed near the base of the swing batten lever O, pivoted to a fixed bracket projecting from the top of the jacquard framework at P. The position of the card cylinder is shown at Q. The extremity of the arm L is linked by the connection R to a small lever S, set screwed to the shaft T which extends and is fastened to the swing batten O and its duplicates for the same cards cylinder. Immediately behind the lever S and set screwed diametrically opposite to it, is second lever U to which a cord V is attached. This hangs down to within the control of the weaver. Corresponding details, from K to V inclusive, are indicated from Kꞌ to Vꞌ for controlling the card cylinder on the opposite side of the jacquard machine. Portions of the needles and needle board for the right hand cylinder are given at W, and for the left hand at Wꞌ.

Action of the mechanism

In the illustration ,the socket Mꞌ of arm Lꞌ is in working contact with the stud Nꞌ in the swing batten lever Oꞌ , so that card cylinder Qꞌ will strike against the needles Wꞌ on every short whilst this arrangement last. But immediately weaver stops the loom, pulls down and makes fast the cord Vꞌ he elevates through the medium of parts Uꞌ, Sꞌ and Rꞌ the free arm of Lꞌ and detaches the socket Mꞌ from its connections Nꞌ and swing lever Oꞌ. Simultaneously the cord V is released and the arm L falls, by gravity ,on to the stud N ,so that by turning the loom slowly ‘over; the notch M falls over the stud N and locks itself , by which means the cylinder Q is in working operation for as long as required.

CROSS BORDER JACQUARD MACHANISM

Labels: Weaving Manufacturing Technology | at 6/22/2011 02:19:00 PM

Cross border jacquard mechanism

Cross border patterns are specially adapted to the manufacture of handkerchief, napkins, damask; table covers shawls tapestries and carpets. The arrangement of the mechanism for producing the side borders and the body or center for any of these types of woven figured fabrics present few difficulties , one portion of the upright hooks being set apart for weaving the borders and another for producing the center. When two or more jacquard machine is used one is frequently reserved for the border and the rest for the center. The harness cords are tied up to their respective sets hooks or machine and passed through the comber boards to suits the side borders and center.

The difficulties being when having woven one or more repeat of patterns it is necessary to producing a change or cross border which shall balance the side borders and make one complete square or oblong pattern. The manufacture of bordered fabrics involves the adoption of one or more other of the fallowing mechanical methods.

1) Whenever the center and the side border constitute only one repeat of pattern, it is usual to stamp two repeats of the cross border and one repeat of the center but to lace the second set of border cards the reverse way making one continuous chain so that the loom can run without interruption for change of pattern. When only a small quantity is required to be woven the cross border cards are only stamped for one repeat; this are woven forwards, before weaving the center and backwards after the center has been woven. Where a large number of webs have to be produced the former plan is sometimes adopted even when there are two or more repeats of pattern for the center to be woven withes very long length of table covers etc this plan become most expensive involving the use of many thousands of cards a greater number than the loom is capable of accommodating.

2) Two sets of cards are cut one for the center and sides and the other for the cross border the latter consisting of two repeats laced in opposite direction. As many repeats of the center as may be required are woven then by hand the cross border cards are substitute over the cards cylinder and adjusted so as to start with no 1 card and the whole sets are woven over once when the cards are again changed by hand to the first set; the operation are similarly repeated until the request quantity of material has been woven. The slowness and inconvenience of this method have led to the introducing of several semi or wholly automatic device.

3) A common method consists in employing two sets of cards with two cards cylinder as on the double lift principle. One sets of pattern cards and card cylinder controls the centre and the other set and cylinder the cross border. The cylinders are designed to strike on every pick but are only in action one at a time according to whether the centre or cross border is being woven. Whenever either cylinder has to be put into action the other must be simultaneously thrown out.Numerous inventions have been designed whereby this operation may be performed by hand or automatically. The mechanism which will perform these changes automatically is a desideratum and ideal but such motion of necessity involve very many mechanical details and complications for which reasons they do not readily find favor.

BASIC KNITTING ELEMENTS FOR A CIRCULAR KNITTING MACHINE

Labels: Knitting Manufacturing Technology | at 4/03/2011 05:07:00 AM

NEEDLES

The needles are the most important stitch forming elements. They are displaced vertically up and down and are mounted into the tricks or cuts of the knitting cylinder.

There are three types of needles namely:

1. Latch needle

2. Spring bearded needle 3. Compound needle.

We can divide a needle into three main parts:

A. the hook, which takes and retains the thread tube looped;

B. the hook opening and closing device, that allows the hook to alternatively take a new thread and release the previous one;

C. a system allowing the needle to move and form the loop.

1=Butt,2=Butt height,3=Back shank,4=Stem,5=Crimp,6=Groove,7=Cheek,8=Hook,9=Hook width,10=Latch,11=Rivet

Fig: Needle

Sinker

The sinker is the second primary knitting element. It is a thin metal plate with an individual or a collective action operating approximately at right angles from the hook side of the needle bed, between adjacent needles.

Sinkers capable of producing loop fabric are well known in the knitting industry. In such machines the sinkers generally include a blade having an upper edge which defines a lower knitting level and a nib having an upper edge which is at an upper knitting level. Long loops are formed at the upper knitting level of the sinkers with a loop yarn and a base yarn is knitted over the blade. The sinkers may be formed and their movement controlled to cause either the loop yarn to appear on one side of a fabric and the base yarn on the other or the loop yarn to appear on both sides.

In the past it has not been possible to producing loop cloth of ideal quality since loops would twist or coil making it difficult to finish a loop fabric into satisfactory velor. Furthermore loops which were supposed to appear on the front of a fabric would sometimes appear on the other side. The back of loop cloth was therefore apt to have objectionable loose protruding loops and double tuck stitches.

1=Butt,2=Butt breadth,3=Height of shank,4=Buldge,5=Neb,6=Length of neb,7=Throat angle,8=Sinker platform height,9=Breadth of lower shank,10=Clearance,11=Throat

Fig: sinker.

Sinkers Operation

1. The held loop is positioned in the throat of the sinker when the sinker moves forward and the needle moves upward for clearing. The held loop is held by the throat and hence its movement along the needle is restricted.

2. The sinker remains at its forward position when the needle attains its clearing position.

3. The sinker retracts when the needle comes down after feeding. At this stage, due to sinkers retraction, fabric or held loop is eased out. Also the sinker belly supported the fabric or held loop and hence its movements along the needle is prevented.

4. Sinker remains in backward position and the needle descends to its lowest position drawing the new loop through the old one.

5. Before the needle ascends, the sinker moves forward to push the knitted fabric a little and to hold the old loop away from the head of the needle and to be in a position to control the fabric.

Jack

In circular knitting machines of the rotatable cylinder type a well know means for selectively actuating the knitting instrumentalist is that of a pattern controlled slider jack system. Engaged the known type of slider jack system it is common practice to transmit the dictates of the pattern controlled slider jack directly to a needle actuating jack. Circular knitting machines which utilize a slider jack system must have a cylinder of sufficient length to accommodate the circular series of needle, needle actuating jacks and slider jacks which are slid ably mounted in the slots formed on the periphery of said cylinder. The slider jack must be raised a sufficient distance so as to raise the needle actuating jack or intermediate jack to a level where its operating butt will be engaged by a cam member and raise said jack to knitting height which in turn will raise its respective needle to the required height to perform its intended function.

Dial

Dial is the upper steel needle bed used in double knit machines. Into the grooves of the dial, the needles are mounted horizontally and are allowed to move radially in and out by their dial cams. The number of grooves per unit space conforms to the cylinder gauge in most of the cases.

Fig: dial

CYLINDER

The cylinder is a steel circular bed having grooves/tricks/cuts on its outer periphery into which the needles are mounted. With reference to the tricks, the needles move vertically up and down by their butt being in contact with the cam track. The number of tricks per inch i.e., number of needles per inch decides the gauge of the machine. Machines are built as low as 4 NPI to as high

as 32 NPI. Based on the machine gauge, the fineness of the yarn to be knitted can be varied. The diameter of the cylinder also varied based on the type and width of the fabric and a maximum of 75 cm diameter machines are available.

Fig: Cylinder

CAMS

The knitting cams are hardened steels and they are the assembly of different cam plates so that a track for butt can be arranged. Each needle movement is obtained by means of cams acting on the needle butts.

The upward movement of the needle is obtained by the rising cams or clearing cams. The rising cam places the needle at a certain level as it approaches the yarn area. Cams controlling the downward movement of the needles are called stitch cams.

The stitch cam draws the needle down below the knitting level, thereby drawing a loop formed by the fed yarn through the loop already on the needle. The lowest point to which the needle is drawn by the stitch cam is called the "cast-off" position. They are screwed to the cylindrical cam ring and are adjustable in vertical direction. If the stitch cam is raised, then shorter loop is drawn below the sinker level and a tighter fabric will result. With lowering of stitch cam, a reverse result is obtained. Guard cams keep the needle butts in their race-way.

Running cams or the needle butts at a low level until they meet the next rising cam.

Fig: Cams

FEEDERS/STRIPPERS

Feeders are the yarn guides placed close to the needles to the full circumference of the knitting zone. The feeders feed the yarn into the needle hooks and control the needle latches in their open position while the needle attain their clearing position. They consist of a yarn guiding hole and a bevel edge to guard the latches of the approaching needles. They are slightly curved to the corresponding curvature of the needle bed. Feeders may have two holes also for the purpose of plating.

Yarn feeders can be divided into “positive” or “negative” types depending on the possibility of controlling the yarn feeding speed and uniformity.

The feeder brackets can be adjusted to set their distance from the needle and to ensure yarn feed into needle hooks. Stripers are the feeders designed to deliver two or more yarns individually to the same feed. They can be considered as moving guide replacing the holes of fixed guides. In a two color stripe, two different colored yarns are supplied by two stripper fingers and their engagement is controlled by an endless control chain which governs the guide change at the appropriate feeds. At each revolution, a counter may select the movement of all the striper chains. The stripes are used on both single and double bed machines.

Fig: Feeders/Stripers

By
S&R

BASIC DISCUTION ABOUT WARPING CREEL

Labels: Weaving Manufacturing Technology | at 3/06/2011 04:57:00 PM

Creel

The creels are simply metallic frames on which the feeding bobbins are fitted. They are outfitted with yarn tension devices, which in modern machines are provided with automatic control and centralized tension variation.

The creels are the frames on which the cones which feed the warped are pinned. The number of cones depends on the type of fabric to be produced. The yarns are wound side by side and parallel one another on the beam, if possible with the same tension.

The tension devices fitted on the creels are designed to obtain this uniform tension.

The cone position and their accessibility are two important factors for the operator.

The latest creels have yarn tension devices with automatic control and centralized tension variation. These devices allow also processing a wide range of yarns on the same creeling plant.

Warping is a low yield operation owing to the time needed for creeling. Various solutions have been conceived to minimize this time, by trying to perform the creeling of the full cones while the warped is running.

The trolley creels have a yarn cutting and knotting device which can cut 720 ends in 50

Seconds and knot them in 10 minutes.

This system is suitable for staple fibre yarns in counts ranging from Nm 10 to Nm 140. Trolley creels have generally two series of trolleys: one in operation and one waiting for being creeled.

For staple fibre yarns also mobile creels are used. These can be equipped with a series of trolleys for the transport of the reserve cones; as an alternative, two creels with stationary cone carrier frame are used together with the warped. In both cases the bobbins are creeled during warping.

Another solution employs swivel frames. While yarns are unwound from the bobbins placed in the inside of the creel, it is possible to creel at the outside of the creel the new lot of cones.

For luxury yarns, the so-called magazine creels are used, which enable to creel two cones per creeling position and to piece head-tail end of two cones.

For the creeling of dyed yarns, a programmable electronic system has been studied. A warning light indicates the position where the yarn of a certain color must be creeled.

This allows a time saving of 60% in creeling and avoids patterning faults and double ends.

The creels are equipped with yarn break detectors which warn the operator through display at the start of the creeling operation. When the yarn breaks, the sensor stops the warped and indicates through signal lights the position of the yarn breakage.

All types of creels can be equipped with air-blowing trolleys to maintain tensions clean.

FIG: Warping creel

Types of creel

1. *Single ends creel

a) Truck creel

b) Duplicated creel

2. *Magazine creel

3. *Swivel frame creel

4. *Mobile creel

5. *V-Shaped creel

6. *Rotating frame creel

7. *Unrolling creel

Single ends creel

Single package is associated with each end being wound on beam. The creel packages contain same amount of yarn.

FIG: Single ends creel

a) Truck creel: In travel creel, head stock is rigid and creel is variable.

b) Duplicated creel: In duplicated creel, head stock is variable and creel is fixed.

FIG: Truck creel

Magazine creel

This invention has general reference to means or equipment such as used in the textile arts for the grouped resolvable support of threads or yarn supply package or spools for beaming or spools for beaming or re-spooling, with the tail end of the threads or yarn of one package or spool connected or tied over to the leading end of another package or spool to speed up the beaming, re spooling or as associated operation.

More specifically the instant improvement re-late to yarn package or cone supporting creels of the species commonly designated as vertical type magazine cone creels; such creels including multiple upright or standards having vertically adjustment opposed directed horizontal affording rotary support for active and inactive pairs of package or cones that have the tail end of the active cone tied up or connected to the leading end of the associated inactive cone.

Creel of the above specified type while satisfactory in many respects are disadvantageous when an active package or cone become exhausted in as much as the operator must exercise considerable care in making the replacement, with an attendant waste of time due to the difficulty experienced in bringing the exhausted package or cone carrier member out into the clear where the operator can make said replacement without reaching over, fouling or entangling any of the running threads or yarn.

FIG: Magazine creel

Swivel frame creel

This type of creel was designed as a variation of the mobile creel to enable the creeling up of bobbins which, owing to their heavy weight (5 to 25 kg), cannot be pinned on trolleys. Each bobbin holder is double-sided: the threads are unwound from one side, while a new series of bobbins is creeled up on the other side.

FIG: Swivel frame creel

Mobile creel

This creel type is similar to the standard creel, but is formed by trolleys which can be taken individually out of the creel.

With mobile creels, individual bobbin trolleys enter the one after the other. Reeling up of the bobbins can be performed outside the creel while the preceding sets of bobbins are being used.

This reduces considerably the waiting time. The mobile creel comes in handy especially when there is insufficient room to permit the use of two standard creels.

1=Creel frame, 2=Bobbins trolleys with bobbins, 3=Threads brake, 4=Threads brake, 5=Stop motion.

FIG: Mobile creel with outside draw off.

V-Shaped creel

V-Shaped creel are shaped like are a V when viewed from above; this shape reduces the number of deflections and guide elements. Also the time required to repair a thread break is reduced and creeling up can take place on the inside during the warping process V-Shaped creel take up pore space than normal ones, so the inside section is used often used for storage.

1=Creel frame, 2=Bobbin carrier with bobbins, 3=Threads brake, 4=Threads brake creel, 5=Stop motion

FIG:V-Shaped creel

Rotating frame creel

On rotating frame creel the bobbins are placed on rotating frames. In fig illustrates a rotating frame creel with outside draw-off. While the threads they are being draw-off during the warping process, new bobbins can be creeled up on the inside. If the outside bobbins are empty, the frame is rotated and a new pulled in. This type of creel reduces stoppage times during bobbin change.

1=Creel frame, 2=Rotating frame with bobbins, 3=Threads brake, 4=Threads brake creel, 5=Stop motion.

FIG: Rotating frame creel.

Unrolling creel

In situation in which elastic materials are being warped in section onto warp beams from individual bobbins, an even yarn tension can only be achieved using a positive thread feed. Cylindrical bobbins on one or more rollers that are turning synchronously in the same direction are unwound tangentially.

1=Lever, 2=Bobbin, 3=Take-up roller, 4=Stop motion,5=Pre-tensioning device,6=Spacer reed,7=Warped.

FIG: Schematic view of an unrolling creel placed parallel with the warping machine.

Importance of warping creel

In the same time a large amount of yarn package, cone or cheese are wound and unwound.
It ensures well decorated distribution of yarn on the warp beam.
By creeling all of the yarns are separated from each other.
By creeling all of the yarns of warp beam achieve a perfect tension.