TextileStudyCenter: 2015

Thursday, December 31, 2015

Melt Spinning , Dry spinning and Wet Spinning Method

Melt Spinning, Dry spinning and Wet Spinning Method :

Man-made fibers are manufactured by spinning the polymer. There are three major types of spinning process. They are-

❶ Melt Spinning (It is used for polymers that can be melted easily.)

❷ Dry Spinning (It involves dissolving the polymer into a solution that can be evaporated.)

❸ Wet Spinning (It is used when the solvent can’t be evaporated and must be removed by chemical means.)

Melt Spinning:

Melt spinning uses heat to melt the polymer to a viscosity suitable for extrusion. This type of spinning is used for polymers that are not decomposed or degraded by the temperatures necessary for extrusion. This method is used by 70% of the fibers.

Vedio: Melt Spinning

Spinning process:

❶ In melt spinning, polymer is heated and it melts to form a liquid spinning solution or dope.

❷ Chips of polymers are fed to a hopper which is heated. There is a grid (sieve) at the base which permits only molten liquid to pass through.

❸ Then the solution is purified by filter.

❹ The molten polymer is extruded at high pressure and constant rate through a spinneret into a relatively cooler air stream that solidifies the filaments.

❺ Finally the filament yarn either is immediately wound onto bobbins or is further treated for certain desired characteristics or end use.

Example: Melt spinning is used for the production of polyester, nylon, olefin, saran and glass fibers.

Advantages:

►High speed (275 to 1500 yds/min); (4000 yds/min spin draw)

►No solvents

►No purification problems

Disadvantages:

►Separate drawing step (unless spin draw)

Dry spinning:

Dry spinning is used for polymers that need to be dissolved in a solvent. Solvent spinning (dry spinning and wet spinning) are used by 30% of the fibers.

Spinning process:

❶ In dry spinning, a volatile solvent is used to dissolve the raw materials and form a salutation.

❷ Then the solution is purified by filter.

❸ The solution is extruded through a spinneret into a warm air chamber where the solvent evaporates, solidifying the fine filaments.

❹ Finally the filament yarn either is immediately wound onto bobbins or is further treated for certain desired characteristics or end use.

Example: Dry spinning is used in the production of acetate, triacetate, and some acrylic, modacrylic, spandex, and vinyon (PVC,PVA) fibers.

Advantages:

►Yarn does not require purification

Disadvantages:

►Flammable solvent hazards

►Solvent recovery

►Slow (200-400 yds/min)

Wet Spinning:

This is the oldest, most complex and also the most expensive method of man-made yarn manufacture. This type of spinning is applied to polymers which do not melt and dissolve only in non-volatile or thermal unstable solvents.

Vedio: Wet spinning

Spinning process:

❶ In wet spinning, a non-volatile solvent is used to convert the raw material into a solution.

❷ The solvent is extruded through the spinneret either by simply washing it out or by a chemical reaction between the polymer solution and a reagent in the spinning bath.

❸ After extrusion, the solvent is removed in a liquid coagulation medium.

❹ Finally the filament yarn either is immediately wound onto bobbins or is further treated for certain desired characteristics or end use.

Example: Wet spinning is used in the production of aramid, Lyocell, PVC, Vinyon (PVA), viscose rayon, spandex, acrylic and modacrylic fibers.

Advantages:

►Large tows can be handled

Disadvantages:

►Slow (70-150 yds/min)

►Washing to remove impurities

►Solvent and chemical recovery

General process diagram of melt, dry and wet spinning process

Difference between Melt spinning, Dry spinning & Wet spinning

Melt Spinning , Dry spinning and Wet Spinning Method

Man-Made Fibers & Classification of Man-Made Fibers

What Is MMF?

In a very general way, a fiber is defined as any product capable of being woven or otherwise made into a fabric. It may be thought of as the smallest visible unit of textile production. Fibers may be agricultural products (such as cotton or wool) or units (such as nylon or polyester) manufactured in a chemical plant. Fibers than serve as the raw material in the next stage of textile manufacturing.

In seventeenth century a scientist named Hooke suggested that if proper liquid were squirted through a small aperture and allowed to congeal a fiber can be produced. Manufactured (MF) fibers (formerly termed “man-made”) are formed from a suitable raw material as a thick, sticky liquid, which is “spun” or extruded through spinneret holes, forming streams that are solidified into fibers.

Classification of Man-Made Fibers

Fibers are commonly produced in the following way

❶ Staple fibers

❷ Filaments

❸ Filaments tow

Staple fibers: A staple fiber is a fiber of relatively short length, as is the case with most natural fibers, which range from a few millimeters (e.g. the shortest cotton fibers, known as linters) to around a meter (e.g. fibers from bast plants). Staple fibers are typically between 3 and 20 cm in length. Given the differences in average fiber length, cotton fibers (2–3 cm) and wool fibers (5 cm or more) are, for example, sometimes referred to as ‘short staple’ and ‘long staple’ fibers, respectively.

Filaments: A filament is a fiber of indefinite length. The various silks are the only natural filament fibers. Most regenerated and synthetic fibers are produced as filaments. These can be used in single or multifilament form. Some of these are also assembled to produce a ‘tow’ which is then cut or broken into required short lengths to produce staple fibers suitable for blending with other fibers, in particular with cotton or wool.

Filaments tow: A tow can mean two different things:

In the synthetic fiber industry, a tow is a large assembly of filaments that is destined to be cut into shorter (staple) fibers.

In the processing of natural fibers (flax), tow is the shorter fiber produced when the stalks are processed to extract the fibers (the long fibers are called line flax).

Process Flow Chart of Man Made Fibre Production

Fiber forming polymer/Raw materials

Spinning (conversion to polymer to fiber)

Drawing/Stretching (To increase strength and crystallinity of molecules)

Texturing (To achieve bulk and grater absorbency)

Intermingling (For thrusting out protruding filament ends)

Heat setting (To improve dimensional stability)

Finished filament

Fiber forming polymer

Fiber forming polymers typically are linear and are capable of being oriented. The molecular weights of fiber forming polymers must be high enough for achieving good mechanical and thermal stability, and at the same time, low enough for dissolving or melting for extruding into fibers. These linear, moderate-molecular weight polymers can be made into fibers by difference type of spinning.

Spinning

Spinning is the process through which bulk polymers are processed into a thread and/or yarn.

All man made fiber spinning process are based on three general steps. These steps are:

❶ Conversion of a polymer into a liquid or spinning solution, also called a dope.

❷ Extruding the solution through a spinneret to from a filament or fiber.

❸ Solidifying the fiber by co-angulation, evaporation or cooling.

Spinneret:

Spinneret is a metal component (made of platinum or iridium) having ten to several hundred small holes. The fluid polymer is injected through these tiny openings to produce filaments from polymer solution. As schematized in figure, a spinneret is similar to a bathroom shower head. The number of holes in the spinneret varies with desired number of filaments required. A small spinneret have up to ten holes, while a large one has more than 10000 holes.

Spinneret features:

Spinneret length: 10-25 mm

Spinneret diameter: 30-200 mm

Spinneret thickness: 3.0 mm

Hole dia: 0.1-0.8 mm

Man-Made Fibers & Classification of Man-Made Fibers

Yarn Numbering System

Yarn Number

Yarn number is a measure of the fineness or size of a yarn expressed either as mass per unit length or length per unit. Yarn Count and Yarn Size are synonymous with Yarn Number.

Yarn Numbering System

There are two systems of expressing yarn number or yarn count.

❶ Direct yarn numbering system (mass/unit length)

❷ Indirect yarn numbering system (length/unit mass)

Direct yarn numbering system

In a direct yarn counting system, the yarn number or count is the weight of a unit length of yarn. This means the higher the yarn count number, the heavier or thicker the yarn. It is fixed length system. This system is generally used for jute or silk yarn.

The following formula is used to calculate direct yarn count system.

Where, w=yarn number or count

W=the weight of the sample (yarn) in units of the system at the official regain

L=length of the sample, and

l=unit of length of the system

Major direct numbering System

Denier: In the direct Denier system, the yarn count number indicates “the weight in grams of 9000 meters of yarn”.

e.g. 30D indicates that 9000 meters of yarn weight 30 grams.

Tex: In the direct universal Tex system, the yarn count number indicates “the weight in grams of 1000 meters of yarn”.

e.g. 30 Tex indicates that 1000 meters of yarn weight 30 grams.

Dtex: In the direct Decitex system, the yarn count number indicates “the weight in grams of 10000 meters of yarn”. (1 dtex=0.9 denier)

e.g. 50 Tex indicates that 1000 meters of yarn weight 30 grams.

Math: If a skein of 100 m of filament Viscose Yarn weight is 1.67 g, calculate its Denier.

Solⁿ: In the Denier system the weight unit is the gram and the unit of length is 9000 m.

Thus, W=1.67 g, L=100 m, and = 9000 m.

So the yarn count is 150.3 D.

Indirect yarn numbering or counting system

In an indirect yarn counting system, the yarn number or count is the number of “units of length” per “unit of weight” of yarn. This means the higher the yarn count number, the finer or thinner the yarn. It is based on the fixed weight system. This system is generally used for cotton, woolen, worsted and linen yarn.

The following formula is used to calculate indirect yarn count system.
Where, N_id=yarn number or count in indirect system

W=the weight of the sample (yarn) in units of the system at the official regain

w=unit of weight of the system

L=length of the sample, and

l=unit of length of the system

Major indirect numbering or counting System

English Cotton Count (Ne): In the indirect English cotton count system, the yarn count number indicates “number of 840 yard hanks of yarn per 1 pound weight”.

e.g. 30/1 cotton(1 means single yarn) indicates that 30 x 840 yards of yarn weight 1 pound.

e.g. 40/2’s (2 means ply yarn) indicates that 20(Resultant count)x 840 yards of yarn weight 1 pound.Metric Count (Ne): In the indirect metric count system, the yarn count number indicates “number of 1000 m (or 1 Km) of yarn per 1 Kg weight”.

e.g. 30 Nm indicates that 30 kilometers or 30000 meters of yarn weight 1 kilogram.

For example, if we consider a yarn of 2000m having the weight of 450g. So the count in metric system will be

Worsted Count: In the indirect worsted count system, the yarn count number indicates “number of 560 yards hanks of yarn per 1 pound weight”.

e.g. 1/20 worsted indicates that 20 x 560 yards of yarn weight 1 pound.

e.g. 3/40 worsted indicates that 13.33(Resultant count)x560 yards of yarn weight 1 pound.

e.g. 50 Nm Metric indicates that 50 x 256 yards of yarn weight 1 pound.

e.g. 15 cut Galashiels indicates that 15 x 200 yards of yarn weight 1 pound.

e.g. 16 skeins Yorkshire indicates that 16 x 256 yards of yarn weight 1 pound.

e.g. 10 lea Linen indicates that 10 x 300 yards of yarn weight 1 pound.

Note: Woolen and Worsted Systems-The basic difference between the two is that in the Worsted system all short fibers are removed and the remaining long ones are aligned parallel. In the Woolen system there is no removal of short fibers, so some fibers lie parallel and others randomly.

Math: A lea (120 yd) of cotton yarn weighs 25 gr, calculate its count in the cotton system.

Solⁿ: In English cotton count system, the ‘unit of length’ is the hank (840 yd) and the ‘unit of weight’ is 1 lb. In 1 lb there are 7,000 grains.

Hence, L =120 yd, =840 yd, W=25/7,000 lb, and w=1 lb

So the yarn count is 40’s.

Yarn Numbering System

Relation Between Yarn Count and Diameter & count calculation for ply yarn

Relation Between Yarn Count and Diameter & count calculation for ply yarn :

Count calculation for ply yarn :

We can make a plied yarn by twisting two single yarns together. The resultant yarn count is calculated as follows:

Expression of Resultant Count:

→Resultant count of indirect system= Number of plies/Count of single yarn Or Count of single yarn/Number of plies

→Resultant count of direct system= Count of single yarn × Number of plies Or Resultant count(count of ply or 3,4….yarn)/Number of plies

For example,

❶ 2/24s cotton count: This indicates a yarn made from two 24s cotton count yarns twisted together.

❷ 80 Tex x 2: This indicates a yarn made from twisting together two 80 Tex yarns. This type of designation is generally used with woolen yarns.

❸ R 74 Tex/2: This indicates a yarn made from twisting two yarns together whose resultant count is 74 Tex. This type of designation is generally used with worsted yarns.

Math: A two ply yarn in Tex is composed of one thread 40 Tex, one thread unknown count and has a resultant count of 100 Tex. What is the count of the other component yarn?

Solⁿ: We know that

Math: A resultant two ply yarn count of 16 worsted has one component yarn of 36 worsted. What is the count of the other component?

Solⁿ: We know that

Math: A three ply yarn is composed of one thread of 56 worsted, one thread of 48 worsted and one thread of 2/80 cotton. What is the count of resultant yarn?

Solⁿ:

Count calculation for ply yarn with contraction:

Normally, when two single yarns are twisted together one should expect some contraction or some increase in length depending on the twisting direction. A contraction will result in a yarn slightly coarser than the estimated value. In order to correct for this difference, typically 5% to 10% contraction or extension should be accounted for.

Math: Suppose two yarns of 24/1 Nm are going to be plied with 4% contraction. Find its resultant count in metric system.

Math: Suppose you are provided a cotton yarn of 1500 km of 2/24s found at completely dry condition. Calculate the resultant count in Tex at standard atmospheric condition with 7% contraction.

Relation Between Yarn Count and Diameter :

Before considering cloth setting formulae it is important to fully understand the relationship between the count of a yarn and its diameter (or thickness). If the diameter is increased or decreased then the yarn count is changed.

Relation Between Yarn Count and Diameter & count calculation for ply yarn

Spinning Carding Machine : Chute Feed System

Spinning Carding Machine :Chute Feed System / Flock Feed System :

CHUTE FEED SYSTEM:

The system of feeding small tufts of cotton fibers directly from blow room to the card is called the chute feed system.

Card is arranged in series circuit through pneumatic pipe. Pneumatic tubes are systems that propel cylindrical containers through a network of tubes by compressed air or by partial vacuum. The blow room machinery is linked to the cards by trunking and the opened cleaned cotton is conveyed by pneumatic
means to each card – this is the principle of chute feed system.

ADVANTAGE OF FLOCK/CHUTE FEED SYSTEM:

1.    Direct automatic feed to card increases B/R working efficiency.
2.   Elimination of man power during scutcher operation.
3.   Processing of rejected lap is avoided.
4.   Due to loose form of feeding of fibers trash particles can be removed easily

      during carding.
5.   This is the only solution for higher production
6.   Suitable for synthetic fibers bulky in nature.

DISADVANTAGES/LIMITATIONS OF CHUTE FEED SYSTEM:

1. Blow room should run the same number of hours per week as the cards do.

2.   The card production must be kept excessive to assure continuous feed to

      draw-frame at the time of stoppages at blow room due to maintenance and

      other unavoidable problems.

3. Chute feed system control short term variation but not the medium and

long term variations.

4.   A reliable check on the nominal count can be established in lap forming

       system by controlling total lap weight and C.V. value of the weight per unit

       length. There is no such control in the chute feeding system.

5. Change of mixing will result in more waste in chute feed.

6. Auto-leveler is must

7. investment and maintenance cost is higher

TYPE OF FLOCK/CHUTE FEED SYSTEM:

there are two basic concepts of flock feed:

. one piece chute/single chute:

1. without an opening device

2. simple, economical and requires little maintenance

3. closed system that is excess flock returns to the distributor

4. if too much material is present, neps can be increased

5. not flexible to run different mixings

6. more layout restrictions .

. TWO PIECE CHUTE/DOUBLE CHUTE:

1. with an opening system

2. complex, expensive, but delivers a uniform batt.

DIFFERENCE BETWEEN CONVENTIONAL AND MODERN CARDING MACHINE:

LAP FEED (CONVENTIONAL)	FLOCK FEED (MODERN)
1. whole installation is very flexible.	2. installation is not flexible
2. auto-leveler is not required.	2. auto-leveler is a must.
3. lower maintenance and investment cost.	3. higher maintenance and investment cost.
4. more manpower is needed for transportation of lap.	4. manpower requirement is less as there is no lap transportation or lap change.
5. linear density of lap is very good (uniform)	5. linear density of the web fed to the card is not as good as lap.
6. high production is not possible.	6. flock feed is the only solution for high production.

CONVENTIONAL FEED DEVICE:

A WELL DESIGNED FEED DEVICE IS EXPECTED TO PERFORM THE FOLLOWING TASKS:

clamp the batt securely over its full width
   be able to hold the material back against the action of the licker-in
   present the batt to the licker-in in such a manner that opening can be carried

       out gently.

conventional feed assembly comprises a stationary feed table with

(1) a feed plate

(2) a feed roller

(3) pressed against the plate.

The feed plate is formed as a special extension of the feed table and is adapted to the curvature of the

cylinder.

Spinning Carding Machine : Chute Feed System

Carding Machine Specification - spinning machine

Spinning Machine – Carding Machine Specification :

SPECIFICATION OF CARDING MACHINE:

   working width: 1000-1020 mm
   taker-in diameter: 250-350 mm, RPM: 500-1300
   cylinder diameter: 1016-1290 mm, RPM: 200-800
   doffer diameter: 500-700 mm, RPM: 30-100
no of flats: 100-112
no of flats in working position: 37-43
   direction of flat run: forward/backward
can size: (920mm*1200mm)-(1000mm*1220mm)
   no of sliver produced: 1
   sliver fineness: 0.1-0.2 Ne
   power required: 5.5-12.5 Kw
air required: 1500-300 Nm3h
   can changer: automatic

MATERIAL PASSAGE DIAGRAM OF CARDING M/C:

OPERATING PRINCIPLE OF CARD:

1. pipe ducting 10. flats

2. feed chute 11. cleaning unit

3. transport roller 12. fixed carding bars

4. feed arrangement 13. cover plates/grid

5. taker-in/licker-in 14. doffer

6. grid equipment 15. stripping device

7. suction duct 16. Calendar roller

8. main cylinder 17. cans

9. fixed carding bars 18. Coiler

In modern installations, raw material is supplied via pipe ducting into the feed chute.

A transport roller forwards the material to the feed arrangement. Feed arrangement consists of a feed roller and a feeder plate. These roller and plate push the sheet of fiber slowly into the operating range of the licker-in. Side by side, they maintain optimal clamping.

The materials are opened into tufts by the licker-in. Tufts are passed over grid equipment and transferred to the main cylinder.During the movement through mote knives, grids, carding segments etc the material loses the majority of its impurities. Suction duct carries away the waste.

The tufts go to the main cylinder and open up into individual fibers between the cylinder and the flats, which is called the actual carding process. The flat comprises of 80-116 individual carding bars combined into a belt moving on an endless path. Nowadays 80-116 (in modern cards about 27) of the flats are located in the carding position; the rest are on the return run. During this return, a cleaning unit eliminates fibers, neps and foreign matter from the bars.

Fixed carding bars are designed to assist the carding machine operation. Grids/cover plates enclose the underside of the main cylinder. After carding, the main cylinder carries along the fibers that are loose and lie parallel without hooks. They does not remain in transportable form. That is why doffer is required. The doffer combines the fibers into a web. This is possible because doffer has substantially lower peripheral speed relative to the main cylinder. A stripping device draws the web from the doffer. After calendar rollers have compressed the sliver to some extent, the coiler deposits it in cans. The working rollers, cylinder and flats are provided with clothing, which becomes worn during fiber processing, and these parts must be reground at regular intervals.

FEED SYSTEM:

There are two types of feeding to the cards:

1. lap feed system
2. chute/flock feed system

LAP FEED SYSTEM:

The system of feeding material to the card in the form of scutcher laps is called the lap feed system.

ADVANTAGES OF LAP FEED SYSTEM:

1.   maintenance of lap thickness is easier
2.   installation is very flexible
3. can be operated with several blends
4. the blends can be allocated to individual carding machines
5.   auto-leveler is not required
6.   investment and maintenance cost is lower

DISADVANTAGES OF LAP FEED SYSTEM:

1.    more manpower is needed in transport and lap change.
2.   additional burden on the taker-in as scutcher laps are happily compressed.
3. lap run out causes fault at the time of replacement by a newer one.
4.   clean and good fiber wastage takes place during lap change.
5.   higher production is not possible.

Carding Machine Specification - spinning machine

Test Post from Textile study center

Test Post from Textile study center http://textilestudycenter.com

Carding Definition

Carding Definition :

Carding Definition:

Carding is a mechanical process that disentangles, cleans and intermixes fibers to produce a continuous web or sliver suitable for subsequent processing.

Two proverbs of the experts- “Carding is the heart of spinning” and “well carded is half spun” demonstrate the immense significance of carding in the spinning process.

CARDING IS CALLED THE HEART OF SPINNING:

In carding, fibers are opened to more or less single fibers. Dust, dirt, neps are removed here. Fiber blending and parallelization are also done here. And sliver is also formed here. Since all the major functions are performed in carding, it is called the heart of spinning.

OBJECTS OF CARDING:

1. fiber individualization

2. fiber blending

3. fiber orientation

4. elimination of short fibers

5. elimination of dust

6. elimination of the impurities

7. disentangling of neps

8. sliver formation

Elemination of ( neps , dust , short fibre , impurities ) & does ( blending , individualization , orientation , formation ).

Carding Definition

Saturday, December 26, 2015

Yarn Numbering System

Yarn Number

Yarn number is a measure of the fineness or size of a yarn expressed either as mass per unit length or length per unit. Yarn Count and Yarn Size are synonymous with Yarn Number.

Yarn Numbering System

There are two systems of expressing yarn number or yarn count.

❶ Direct yarn numbering system (mass/unit length)

❷ Indirect yarn numbering system (length/unit mass)

Direct yarn numbering system

The following formula is used to calculate direct yarn count system: