Fabric Club Of BD: 03/01/2011

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.

Primary elements of knitting

Labels: Knitting Manufacturing Technology | at 3/03/2011 10:13:00 AM

Knitting:

Knitting is defined as interlacing of yarn into loop to form fabric. There are different ways that yarn can be subjected to needle for fabric formation. In knitting there basically two system these are –

Weft &
Warp

Weft knitting:

Weft knitting is a completion by loops formed a horizontal manner by adjacent needle. The most common machine is used for weft knitting is the circular knitting machine. This machine creates such able fabric in spiral configuration by run the cylinder. The width of the fabric is determined by the number of needle on the machine. One revelation of the machine complete one course for each yarn feed.

Fig 1: Circular knitting machine

Fig 2: Flat bed machine

A second type of machine can be used to produce weft knit. This machine produces fabric a needle beds that are flat so is called flat bed machine.

Regarding the types of machine used in weft knitting, needles place next to each other, knit one up to another in sequence to produce one raw of loops from the same yarn that show on the figure.

Fig 3: Loop formation in circular knitting machine

On the figure here is an illustration of loops yarn created by weft knitting machine that next yarn horizontal manner, so the loops are formed from right to left

Course:

The horizontal raw of loops produced by adjacent needle to the same knitting cycle is known as a course. The course can be measured by the number of courses per linear unit. Expressed as inch per centimeter. In the figure a pattern of loop range in raw in color that is course. If drawing represent one inch by one inch area we identify these three courses per inch.

Wales

The vertical column of loops produced by same needle knitting at successive knitting cycles is referred to as wale. The wale can measure by the number of Wales per linear length. In the same drawing three Wales per inch.

Stitch density

Stitch density refers to the total number of loops in a measured area of fabric and not to the length of yarn in a loop (stitch length). It is the total number of needle loops in a given area (such as a square inch, or three square centimeters).The figure is obtained by counting the number of courses or pattern rows in one inch (or three centimeters) and the number of Wales in one inch (or three centimeters), then multiplying the number of courses by the number of Wales. (Using a measurement of three centimeters rather than one is preferable for accuracy in counting). Stitch density gives a more accurate measurement than does a linear measurement of only courses or only Wales. Tension acting in one direction might produce a low reading for the courses and a high reading for the Wales; when they are multiplied together this effect is cancelled out. Pattern rows rather than courses may be counted when they are composed of a constant number of courses.

Loop formation:

There are only three types of loop or stitches possible in weft knitting. They are –

Knit
Tuck &
Float

Fig: Knit loop

Fig: Tuck loop

Fig: Float loop

Knit loop:

Just look at the first, one the knit stitch. If every needle is feed a yarn and goes to basic knitting cycle the product referred to as single jersey. All loops are knitted and all loops look exactly alike. Look closely at this drawing a back ground of knit loop the length of yarn in neck loop is called the stitch length. Notify each loop has what can identify as legs and crown. The fabric in the left is technically face side, and the stitches has an over all vertical apparent. And this side we see primarily legs rather than crown. The fabric at the right is technically in the back, which takes on horizontal appearance. In this view we see mainly crown. Referred to a jersey stitch, stitches arrange in this pattern have a distinguishly different look and feel face to the back.

Fig: Technical face

Fig: Technical back

Tuck loop:

Another types of stitch is referred to as the tuck stitch. Because one yarn is tuck behind another and hide. The pattern on the left shows the technical face for tuck stitch. Follow the green shaded course of yarn across the pattern and looks like a loop has been tuck behind another. The pattern on the right shows technical back, for a tuck stitch from the back tuck is more visible to the eye.

Fig: Technical face

Fig: Technical back

How is a tuck stitch made?

During the tuck cycle at feed one the needle move up from the rest position and old stages that has been formed is held and not allowed to close latch. At the needle moves up found up to grab a second yarn which is put into tuck position. Both yarns are then griped at the rest position. The knit cycle of course with a next feed of yarn at this time, both yarn are cleared the new yarn is feed and pull through both the held and tuck loop forming the tuck stitch. This stitch caused by holding one elongated stitch for an extra course caused more length shrinkage. The tuck loop makes the fabric wider and thicker and slightly extensible.

Fig: Tuck loop formation process

Float loop:

The third type of the stitch is the float which is also called miss stitch. The drawing on the left is a technical face. On the face in the middle course of yarn is middle wale. It looks like when a machine not captures or knit with any other stage this is float or miss stitch. In the technical back row the loop float

Fig: Technical face

Fig: Technical back

Float loop formation process:

To produce the float stitch in feed one, a yarn is laid to rest behind the hook of the needle. The needle remains in the rest position. It is not activated in the float cycle. In the knit cycle erase, one a subsequent yarn is knit in the next feed. The missed yarn floats to the technical back of the fabric. Loops can be made float over a series of Wales. To make the structure secured some float yarn can be tied into the ground with a jerky of tuck stitch. Float loops make the fabric more narrow and less extensible because the floating yarn is in straight configuration.

Fig: Float loop formation process

Circular knitting machine:

The principle for circular knitting machine feed from the knitting elements yarn moves from the yarn supply or creel through guides to stop motions control above the machine, then back down to tension controls and yarn feeding devices to the knitting elements. Quality products can be produced only on stop motion and yarn feeding functions are properly set. Then inter get action knitting and needles form loops. The course at the needle of the machine between the take up and yarn feeding mechanism. Circular weft knitting, needle let one after the other in a sequence for each yarn. Loops are formed horizontally by needle knitting around the cylinder forming a tube. After yarn is knit on the knitting elements the knitted fabric passed over a spiral mechanism through take-up roller and round a roll. This electrical spiral distribute the take-up tension uniformly and reliable to fabric confirm flat tube.

Fig: Circular knitting machine

Different parts of circular knitting machine:

1. Chassis 2. Main foot 3. Side foot 5.Supporting ring 6.Needle cylinder 7. Yarn carrier 8. Cam box ring

9. Yarn feed device 10. Feeding the yarn 11. Central machine axis 12. Protective cover 14. Working platform 15. Upper step 16. Lowest step 18. Safety railing 20. Holding rods 21. Roller 22. Horizontal axis 23. Guide way

Needle action:

Cylinder

Knitting machines are designed as each needle can be placed in a groove cut into the out side the middle cylinder. The groove may above refer to as slot or trick. The top edge of each groove is called the verge. This cylinder is very precisely manufacture, so the diameter measure the any place is equal. Machines are classified by the number of slot per linear inch. This is referred to as gauge of the machine. For example eight gauge machines have eight slots per inch. The total number of slot around the circumference of the cylinder, which indicate the number of needles in the cylinder. The more needles the wider the fabric.

Fig: Cylinder

Needle:

In the figure shown a latch needle and label it parts. At the top each needle is a hook, below this is a latch attach with a rivet, bottom edge of the latch is curved to feed over in completely close the hook. All the bottom of the needle is the butt, which place a part in controlling how needle activate up or down. A needle with a latch is very efficient, when the latch needles are used to create weft knit the knitting cycle can be complete with out any auxiliary attachments.

Fig: Latch needle

Latch needle works:

At rest or running position a knit loop rest above or on latch as the needle moves up the old loops are ready formed drops below and clears the latch. As the needle moves down every sieve the new yarn to began forming a new stitch. The latch is knock over by the old loop and this old loop is cast off. The needle moves further down to fully form and complete the new stitch. The amount of yarn used to form a new stitch determines the stitch length. This is the important because the stitch length affects the weight, width and static of the fabric.

Fig: Knitting action of latch needle

Causes needle move up or down:

Cam is responsible for needle movement up or down. Each cam is designed to allow the needle to runs straight or moves up and down. Here needle travels through various stages. At the rest or running position the needle runs straight over the rest cam. When it reaches the clearing cam it raises up step angle which forces the needle rise and clear the old loop. Then the needle drops with a contact stitch cam. As a continuous on its parts it catches new yarn. It continuous further down pulling the new yarn forming a new loop or stitch to form and old loop cast off the up through cam returns the needle to reach resting position. So it can begin cycle again.

Fig: Needle movement process by cam

Sinker:

As needle activation a course how the machine controls the movement of fabric as it knit. There is one more part place between each pair of needles. It’s called the sinker. It is steel element with distinctive shape. The sinker has a butt is place to insert a cam. It has a hold, throat and nose.

Fig:Sinker

As the needle goes up the sinker moves to catch the fabric in its throat. When its catch the loop the old loop clear the latch. When the hook catches the feeder yarn as the needle moves down, the sinker moves backward of the way and knock over, cast off and stitch forming takes place. As the new stitch formed the fabric rest on the top of the nose.