Fabric Club Of BD: Weaving Manufacturing Technology

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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 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.