what is cotton????????

Posted by MuNaWaR

COTTON
WHAT IS COTTON?:
COTTON is defined as white fibrous substance covering seeds harvested from Cotton Plant.
SEED COTTON (called Kapas in Pakistan) harvested from Cotton Plant.
LINT COTTON is obtained by removing the seeds in a ginning machine.
LINT COTTON is spun into Yarn, which is woven or knitted into a Fabric. Researchers have found that cotton was grown more than 9000 years ago. However large scale cultivation commenced during middle of 17th Century AD.
Many varieties of Cotton are cultivated mainly from 3 important genetic species of Gossipium.
G. HIRSUTUM - 87% Grown in America, Africa, Asia, Australia Plant grows to a height of 2 Meters.
G. BARBADENSE- 8% Grown in America, Africa & Asia. Plant grows to a height of 2.5 Meters with yellow flowers, long fibers with good quality, fibers with long staple and fineness
G. Arboreum - 5% Perennial plant grows up to 2 meters with red flowers, poor quality fibers in East Africa and South East Asia.
There are four other species grown in very negligible quantities. Cotton harvested from the Plant by hand - picking or machine picking is ginned to remove seeds and the lint is pressed into Bales for delivery to Spinning Mills. Cotton is Roller Ginned (RG) or Saw Ginned (SG) depending varieties and ginning practices.
Cotton is cultivated in 75 Countries with an area of 32 Million Hectares. Cultivation period varies from 175 days to 225 days depending on variety. Cotton is harvested in two seasons, summer and winter seasons.
Saw ginned cotton is more uniform and cleaner than Roller Ginned Cotton. But fibers quality is retained better quality in Roller Ginning than Saw Ginning which has high productivity.
Cotton Fiber is having a tubular structure in twisted form. Researchers have developed colored cotton also. As on date, percentage of Cotton fiber use is more than synthetic fibers. But, its share is gradually reducing. Cotton is preferred for under garments due its comfort to body skin. Synthetics have more versatile uses and advantage for Industrial purposes.
PROPERTIES OF COTTON
No other material is quite like cotton. It is the most important of all natural fibres, accounting for half of all the fibres used by the world's textile industry.
Cotton has many qualities that make it the best choice for countless uses:
Cotton fibres have a natural twist that makes them so suitable for spinning into a very strong yarn.
The ability of water to penetrate right to the core of the fibre makes it easy to remove dirt from the cotton garments, and creases are easily removed by ironing.
Cotton fabric is soft and comfortable to wear close to skin because of its good moisture absorption qualities.
Charges of static electricity do not build up readily on the clothes.
HISTORY OF COTTON
Nobody seems to know exactly when people first began to use cotton, but there is evidence that it was cultivated in India and Pakistan and in Mexico and Peru 5000 years ago. In these two widely separated parts of the world, cotton must have grown wild. Then people learned to cultivate cotton plants in their fields.
In Europe, wool was the only fiber used to make clothing. Then from the Far East came tales of plants that grew "wool". Traders claimed that cotton was the wool of tiny animals called Scythian lambs that grew on the stalks of a plant. The stalks, each with a lamb as its flower, were said to bend over so the small sheep could graze on the grass around the plant. These fantastic stories were shown to be untrue when Arabs brought the cotton plant to Spain in middle Ages.

In the fourteenth century cotton was grown in Mediterranean countries and shipped from there to mills in the Netherlands in Western Europe for spinning and weaving. Until the mid eighteenth century, cotton was not manufactured in England, because the wool manufacturers there did not want it to compete with their own product. They had managed to pass a law in 1720 making the manufacture or sale of cotton cloth illegal. When the law was finally repealed in 1736, cotton mills grew in number. In the United States though, cotton mills could not be established, as the English would not allow any of the machinery to leave the country because they feared the colonies would compete with them. But a man named Samuel Slater, who had worked in a mill in England, was able to build an American cotton mill from memory in 1790.
GROWING THE COTTON
Cotton plant's leaves resemble maple leaves and flowers look very much like pink mallow flowers that grow in swampy areas. They are relatives and belong in the same plant family.

Cotton is grown in about 80 countries, in a band that stretches around the world between latitudes 45 North to 30 South. For a good crop of cotton a long, sunny growing season with at least 160 frost-free days and ample water are required. Well drained, crumbly soils that can keep moisture well are the best. In most regions extra water must be supplied by irrigation. Because of its long growing season it is best to plant early but not before the sun has warmed the soil enough.

Seedlings appear about 5 days after planting the seeds. Weeds have to be removed because they compete with seedlings for water, light and minerals and also encourage pests and diseases. The first flower buds appear after 5-6 weeks, and in another 3-5 weeks these buds become flowers.
Each flower falls after only 3 days leaving behind a small seed pot, known as the boll. Children in cotton-growing areas in the South sometimes sing this song about the flowers:
First day white, next day red,
third day from my birth - I'm dead.
Each boll contains about 30 seeds, and up to 500 000 fibres of cotton. Each fibre grows its full length in 3 weeks and for the following 4-7 weeks each fiber gets thicker as layers of cellulose build up the cell walls. While this is happening, the boll matures and in about 10 weeks after flowering it splits open. The raw cotton fibres burst out to dry in the sun. As they lose water and die, each fibre collapses into what looks like a twisted ribbon. Now is time for harvesting. Most cotton is hand-picked. This is the best method of obtaining fully grown cotton because unwanted material, called "trash", like leaves and the remains of the boll are left behind. Also the cotton that is too young to harvest is left for a second and third picking. A crop can be picked over a period of two months as the bolls ripen. Countries that are wealthy and where the land is flat enough usually pick cotton with machines - cotton harvesters.
COTTON AND YARN QUALITY CO-RELATION:
Instead of buying any cotton available at lowest price, spinning it to produce yarn of highest count possible and selling Yam at any market in random, it is advisable to locate a good market where Yarn can be sold at highest price and select a Cotton which has characteristics to spin Yarn of desired specifications for that market.
ESSENTIAL CHARACTERISTICS of cotton quality and characteristics of Yarn quality of Yarn are given from detailed experimental investigations. Some of the important conclusions which help to find co-relation between Yarn quality and Cotton quality are given below
STAPLE LENGTH: If the length of fiber is longer, it can be spun into finer counts of Yarn which can fetch higher prices. It also gives stronger Yarn.

STRENGTH: Stronger fibers give stronger Yarns. Further, processing speeds can be higher so that higher productivity can be achieved with less end-breakage.

FIBER FINENESS: Finer Fibers produce finer count of Yarn and it also helps to produce stronger Yarns.

FIBER MATURITY: Mature fibers give better evenness of Yarn. There will be fewer ends - breakages. Better dyes' absorbency is additional benefit.

UNIFORMITY RATIO: If the ratio is higher. Yam is more even and there are reduced end-breakages.

ELONGATION: A better value of elongation will help to reduce end-breakages in spinning and hence higher productivity with low wastage of raw material.

NON-LINT CONTENT: Low percentage of Trash will reduce the process waste in Blow Room and cards. There will be fewer chances of Yarn defects.

SUGAR CONTENT: Higher Sugar Content will .create stickiness of fiber and create processing problem of licking in the machines.

MOISTURE CONTENT: If Moisture Content is more than standard value of 8.5%, there will be more invisible loss. If moisture is less than 8.5%, then there will be tendency for brittleness of fiber resulting in frequent Yarn breakages.

FEEL: If the feel of the Cotton is smooth, it will be produce more smooth yarn which has potential for weaving better fabric.

CLASS : Cotton having better grade in classing will produce less process waste and Yarn will have better appearance.

GREY VALUE: Rd. of calorimeter is higher it means it can reflect light better and Yam will give better appearance.

YELLOWNESS: When value of yellowness is more, the grade becomes lower and lower grades produce weaker & inferior yarns.

NEPPINESS: Nippiness may be due to entanglement of fibers in ginning process or immature fibers. Entangled fibers can be sorted out by careful processing But, Neps due to immature fiber will stay on in the end product and cause the level of Yarn defects to go higher.
An analysis can be made of Yarn properties which can be directly attributed to cotton quality.
1. YARN COUNT: Higher Count of Yarn .can is produced by longer, finer and stronger fibers.
2. C.V. of COUNT: Higher Fiber Uniformity and lower level of short fiber percentage will be beneficial to keep C.V.(Co-efficient of Variation) at lowest.
3. TENSILE STRENGTH: This is directly related to fiber strength. Longer Length of fiber will also help to produce stronger yarns.
4. C.V. OF STRENGTH: is directly related CV of fiber strength.
5. ELONGATION: Yam elongation will be beneficial for weaving efficiently. Fiber with better elongation has positive co-relation with Yarn elongation.
6. C.V. OF ELONGATION: C.V. of Yarn Elongation can be low when C.V. of fiber elongation is also low.
7. MARS VARIATION: This property directly related to fiber maturity and fiber uniformity.
8. HAIRINESS: is due to faster processing speeds and high level of very short fibers,
9. DYEING QUALITY: will defend on Evenness of Yarn and marketing of cotton fibers.
10. BRIGHTNESS: Yarn will give brighter appearance if cotton grade is higher.
HOW TO BUY COTTON?
COTTON BUYING is the most important function that will contribute to optimum profit of a Spinning Mill.
EVALUATION of cotton quality is generally based more on experience rather than scientific testing of characteristics only.
TIMING of purchase depends on comprehensive knowledge about various factors which affect the prices.
CHOOSING the supplier for reliability of delivery schedules and ability to supply cotton within the prescribed range of various parameters which define the quality of Cotton.
BARGINING for lowest price depends on the buyer's reputation for prompt payment and accept delivery without dispute irrespective of price fluctuations.
ORGANISING the logistics for transportation of goods and payment for value of goods will improve the benefits arising out of the transaction.
PROFIT depends on producting high quality Yarn to fetch high prices. Influence of quality of raw material is very important in producing quality Yarn. But, quality of yam is a compound effect of quality of raw material, skills of work-force, performance of machines,- process know-how of Technicians and management expertise.
A good spinner is one who produces reasonably priced yarn of acceptable quality from reasonably priced fiber. Buying a high quality, high priced cotton does not necessarily result in high quality Yarn or high profits.
GUIDELINES FOR COTTON CONTRACTS:
Buyer and seller should clearly reach correct understanding on the following factors.
1. Country of Origin, Area of Growth, Variety, Crop year
2. Quality - Based on sample or
Description of grade as per ASTM standard or sampleFor grade only and specifying range of staple length,Range of Micron ire, range of Pressley value, uniformity,Percentage of short fiber, percentage of non-lint content,Tolerable level of stickiness

3. Percentage of Sampling at destination
4. Procedure for settling disputes on quality or fulfillment of contract obligations.
5. Responsibility regarding contamination or stickiness.
6. Price in terms of currency, Weight and place of delivery.
7. Shipment periods
8. Certified shipment weights or landing Weights
9. Tolerances for Weights and Specifications
10. Port of Shipment and port of destination, partial shipments allowed or not, transshipment allowed or not, shipments in containers or Break-bulk carriers
11. Specifications regarding age of vessels used for shipment, freight payment in advance or on delivery
12. Responsibility regarding Import & Export duties
13. Terms of Insurance cover
14. Accurate details of Seller, Buyer and Broker
15. Terms of Letter of. Credit regarding bank .negotiation, reimbursement and special conditions, if any

Choose Correct Supplier or Agent:
Apart from ensuring correct terms of Contract, Buyer should ensure that purchase is made from Reliable Supplier or through a Reliable Agent. Some suppliers evade supplies under some pretext if the market goes up. Otherwise, they supply inferior quality Either way buyer suffers.
By establishing long term relationship will reliable Suppliers, Buyers can have satisfaction of getting correct quality, timely deliveries and fair prices.
CHOOSING SUPPLIER:
It is good to establish long term relationship with a few Agents who represent reputed Trading Companies in various Cotton Exporting Countries. They usually give reliable market information on quality, prices and market trends so that buyer can take intelligent decision. As cotton is not a manufactured Commodity, it is good to buy from dependable suppliers, who will ensure supply of correct quality with a variation within acceptable limits at correct price and also deliver on due date.
CHOOSING QUALITY:
In a market with varying market demand situation. Buyers should decide which counts of Yarn to spin. Buyer can call for samples suitable for spinning Yarn counts programmed for production. Many spinners plan to do under-spinning. For Example, cotton suitable for 44s is used for spinning 40s. Some spinners do over-spinning. They buy cotton suitable for 40s and spin 44s count. But, is advisable to spin optimum count to ensure quality and also keep cost of raw material at minimum level as for as possible. Some spinners also buy 2 or more varieties and blend them for optimum spinning. For' this purpose, a good knowledge to evaluate cotton quality and co-relate with yarn properties of required specifications. Cotton buyer should develop expertise in assessing cotton quality. Machine tests must be done only to confirm manual evaluation.
TAKING RIGHT OPTION:
It is not advisable just to look at price quoted by supplier. Correct costing should be done to work out actual cost when the cotton arrives at Mills. Further lowest price does not always mean highest profit for buying. Profitability may be affected by anyone or more of the following factors.
If the trash is higher, more waste will be produced reducing the Yarn out- turn and hence profit.
If the uniformity is less, end - breakages will be more reducing productivity and profitability.
If grade is poor or more immature fibers are found in cotton, the yarn appearance will be affected and Yarn will fetch lesser price in the market.
If the transit period for transport of cotton is longer, then also profitability will be reduced due blocking of funds for a longer period and increased cost of Interest.
Rate of Sales Tax varies from State to State. This must be taken in to account.
Hence, thorough costing should be worked out before deciding on the quoted value only
The margin of profit in spinning cotton should be calculated before deciding on the various options available depending on market conditions should be studied.
The factors to be considered for taking options are as follows.
Count for which demand is good in market
Prices for various counts for which demand exists.
Cost of manufacturing various counts.
Adequacy of machinery for the selected count.
Various varieties of cotton available for spinning the selected count.
Profit margin for each count using different varieties.
Price quoted by different Agents for same variety of selected cotton.
Reliability of supplier for quality and timely delivery.
Cost Consideration:
Apart from the price quoted by the seller, other incidental costs must be taken into consideration before buying.
a) Duration for goods to reach Buyer's go down from the seller's Warehouse. If the duration is longer, buyer will incur higher interest charges.
b) Cost of Transportation and taxes.
Resolution of differences
If any discrepancy arises in the quality, weight and delivery periods, sellers should be willing to resolve the differences amicably and quickly. In case the matter is referred to Arbitrator, the award of the Arbitrator must be immediately enforced.
Bench Marks for Easy Reference
It is better if quality bench marks are established for different varieties so that buying decisions are easy for buyers Following standards have been found to be appropriate for Strict Middling Grade Cotton of staple 1.3/32".
1. Staple Length ( 2.5% Spun Length) - Minimum 1.08" or 27.4 mm
2. Micron ire : Minimum 3.8, Maximum-4.6 Variation within bulk sample should not be more than _ 0.1
3. Colour : Rd not less than 75 not more than 10
4. Nep Content: Less than 150 per gram
5. Strength : More than 30 grams/tex
6. Length Uniformity Ratio: Not less than 85%
7. Elongation : More than 8%
8. Short Fiber Content: Less than 5%
9. Seed Count Fragments : Less than 15 per grams
1. Commercial Bench marks can be given as follows:
1. Price Competitiveness
2. Price Stability
3. Easy Availability throughout year
4. Uniform Classing and Grading system
5. Even- running Cotton in all Characteristics
6. Reliable deliveries òr Respect for sanctity of contract.
QUALITY EVALUATION:
The need for quality evaluation is for following purposes
a) To get optimum quality at lowest price.b) To decide whether cotton bought will can be processed to spin Yarn of desired specifications.c) To check the quality of sample cotton with quality of delivered cotton.d) To decide about correct machine settings and speeds for processing the cottone) To estimate profitability of purchase decisions.
Knowing the cotton properties is only half the battle for profits. It needs expertise to know how to get best of its value.
Currently popular instrument called HVI gives ready information on various parameters to make correct purchase decisions.
If may not be possible to get all the desired qualities in one variety or one lot of Cotton. In such case, an intelligent decision to select best combination of different varieties or lots to get desired Yam quality is necessary to get optimum yarn quality at optimum cost.
If correct evaluation is made, profits are large. Hence, evaluation of quality is essential for optimum profit making and also make the customers happy with supply of correct quality of Yarn.
Expert classers can manage to achieve reasonable level of correct evaluation. Now, with availability of better instruments, it is better to check qualities to make sure that desired quality of cotton is procured. These details should give cotton buyer reasonable guidance to make correct evaluation of cotton quality and ensure its suitability for producing required quality of yarn.

BASICS OF ELECTRICITY

Posted by MuNaWaR

ALTERNATING CURRENT (AC):
The supply of current for electrical devices may come from a direct current source (DC), or an alternating current source (AC). In direct current electricity, electrons flow continuously in one direction from the source of power through a conductor to a load and back to the source of power. The voltage indirect current remains constant. DC power sources include batteries and DC generators. In alternating current an AC generator is used to make electrons flow first in one direction then in another. Another name for an AC generator is an alternator. The AC generator reverses terminal polarity many times a second. Electrons will flow through a conductor from the negative terminal to the positive terminal, first in one direction then another.


AC SINE WAVE:
Alternating voltage and current vary continuously. The graphic representation for AC is a sine wave. A sine wave can represent current or voltage. There are two axes. The vertical axis represents the direction and magnitude of current or voltage. The horizontal axis represents time.

When the waveform is above the time axis, current is flowing in one direction. This is referred to as the positive direction. When the waveform is below the time axis, current is flowing in the opposite direction. This is referred to as the negative direction. A sine wave moves through a complete rotation of 360 degrees, which is referred to as one cycle. Alternating current goes through many of these cycles each second. The unit of measurement of cycles per second is hertz. In general it is 50Hz or 60 Hz depending upon the country.
SINGLE PHASE AND THREE PHASE AC POWER:
Alternating current is divided into single-phase and three phase types. Single-phase power is used for small electrical demands such as found in the home. Three-phase power is used where large blocks of power are required, such as found in commercial applications and industrial plants. Single-phase power is shown in the above illustration. Three-phase power, as shown in the following illustration, is a continuous series of three overlapping AC cycles. Each wave represents a phase, and is offset by 120 electrical degrees.

AC GENERATORS
BASIC GENERATOR:

A basic generator consists of a magnetic field, an armature, slip rings, brushes and a resistive load. The magnetic field is usually an electromagnet. An armature is any number of conductive wires wound in loops which rotates through the magnetic field. For simplicity, one loop is shown. When a conductor is moved through a magnetic field, a voltage is induced in the conductor. As the armature rotates through the magnetic field, a voltage is generated in the armature which causes current to flow. Slip rings are attached to the armature and rotate with it. Carbon brushes ride against the slip rings to conduct current from the armature to a resistive load.



BASIC GENERATION OPERATION:
An armature rotates through the magnetic field. At an initial position of zero degrees, the armature conductors are moving parallel to the magnetic field and not cutting through any magnetic lines of flux. No voltage is induced

GENERATION OPERATION FROM 0 TO 90 DEGREES:
The armature rotates from zero to 90 degrees. The conductors cut through more and more lines of flux, building up to a maximum induced voltage in the positive direction



GENERATION OPERATION FROM 90 TO 180 DEGREES:
The armature continues to rotate from 90 to 180 degrees, cutting less lines of flux. The induced voltage decreases from a maximum positive value to zero.

GENERATION OPERATION FROM 180 TO 270 DEGREES:
The armature continues to rotate from 180 degrees to 270degrees. The conductors cut more and more lines of flux, but in the opposite direction. Voltage is induced in the negative direction building up to a maximum at 270 degrees.

GENERATION OPERATION FROM 270 TO 360 DEGREES:
The armature continues to rotate from 270 to 360 degrees. Induced voltage decreases from a maximum negative value to zero. This completes one cycle. The armature will continue to rotate at a constant speed. The cycle will continuously repeat as long as the armature rotates.

FREQUENCY:
The number of cycles per second made by voltage induced in the armature is the frequency of the generator. If the armature rotates at a speed of 60 revolutions per second, the generated voltage will be 60 cycles per second. The accepted term for cycles per second is hertz. The standard frequency in the United States is 60 hertz. The following illustration shows 15 cycles in 1/4 second which is equivalent to 60 cycles in one second.



FOUR POLE AC GENERATOR:

The frequency is the same as the number of rotations per second if the magnetic field is produced by only two poles. An increase in the number of poles would cause an increase in the number of cycles completed in a revolution. A two-pole generator would complete one cycle per revolution and a four-pole generator would complete two cycles per revolution. An AC generator produces one cycle per revolution for each pair of poles


VOLTAGE AND CURRENT:
PEAK VALUE:
The sine wave illustrates how voltage and current in an AC circuit rises and falls with time. The peak value of a sine wave occurs twice each cycle, once at the positive maximum value and once at the negative maximum value




PEAK TO PEAK VALUE:
The value of the voltage or current between the peak positive and peak negative values is called the peak-to-peak value.

INSTANTANEOUS VALUE:
The instantaneous value is the value at any one particular time. It can be in the range of anywhere from zero to the peak value.


CALCULATING INSTANTANEOUS VOLTAGE:
The voltage waveform produced as the armature rotates through 360 degrees rotation is called a sine wave because instantaneous voltage is related to the trigonometric function called sine (sin q = sine of the angle). The sine curve represents a graph of the following equation:
e Epeak = ´sin qInstantaneous voltage is equal to the peak voltage times the sine of the angle of the generator armature. The sine value is obtained from trigonometric tables. The following table reflects a few angles and their sine value
The following example illustrates instantaneous values at 90,150, and 240 degrees. The peak voltage is equal to 100 volts. By substituting the sine at the instantaneous angle value, the instantaneous voltage can be calculated.

EFFECTIVE VALUE OF AN AC SINE WAVE:
Alternating voltage and current are constantly changing values. A method of translating the varying values into an equivalent constant value is needed. The effective value of voltage and current is the common method of expressing the value of AC. This is also known as the RMS (root-mean square) value. If the voltage in the average home is said to be120 volts, this is the RMS value. The effective value figures out to be 0.707 times the peak value


The effective value of AC is defined in terms of an equivalent heating effect when compared to DC. One RMS ampere of current flowing through a resistance will produce heat at the same rate as a DC ampere. For purpose of circuit design; the peak value may also be needed. For example, insulation must be designed to with stand the peak value, not just the effective value. It may be that only the effective value is known. To calculate the peak value, multiply the effective value by 1.41. For example, if the effective value is 100 volts, the peak value is 141 volts.
INDUCTANCE:
The circuits studied to this point have been resistive. Resistance and voltage are not the only circuit properties that effect current flow, however. Inductance is the property of an electric circuit that opposes any change in electric current. Resistance opposes current flow; inductance opposes change in current flow. Inductance is designated by the letter "L". The unit of measurement for inductance is the Henry (h).
CURRENT FLOW AND FIELD STRENGTH:
Current flow produces a magnetic field in a conductor. The amount of current determines the strength of the magnetic field. As current flow increases, field strength increases, and as current flow decrease, field strength decreases.
Any change in current causes a corresponding change in the magnetic field surrounding the conductor. Current is constant in DC, except when the circuit is turned on and off, or when there is a load change. Current is constantly changing in AC, so inductance is a continual factor. A change in the magnetic field surrounding the conductor induces a voltage in the conductor. This self-induced voltage opposes the change in current. This is known as counter emf. This opposition causes a delay in the time it takes current to attain its new steady value. If current increases, inductance tries to hold it down. If current decreases, inductance tries to hold it up. Inductance is somewhat like mechanical inertia, which must be overcome to get a mechanical object moving, or to stop a mechanical object from moving. A vehicle, for example, takes a few moments to accelerate to a desired speed, or decelerate to a stop.
INDUCTORS:
Inductance is usually indicated symbolically on an electrical drawing by one of two ways. A curled line or a filled rectangle can be used


Inductors are coils of wire. They may be wrapped around a core. The inductance of a coil is determined by the number of turns in the coil, the spacing between the turns, the coil diameter, the core material, the number of layers of windings, the type of winding, and the shape of the coil. Examples of inductors are transformers, chokes, and motors.
SIMPLE INDUCTIVE CIRCUIT:
In a resistive circuit, current change is considered instantaneous. If an inductor is used, the current does not change as quickly. In the following circuit, initially the switch is open and there is no current flow. When the switch is closed, current will rise rapidly at first, then more slowly as the maximum value is approached. For the purpose of explanation, a DC circuit is used.


The time required for the current to rise to its maximum value is determined by the ratio of inductance, in henrys, to resistance, in ohms. This ratio is called the time constant of the inductive circuit. A time constant is the time, in seconds, required for the circuit current to rise to 63.2% of its maximum value. When the switch is closed in the previous circuit, current will begin to flow. During the first time constant current rises to 63.2% of its maximum value. During the second time constant, current rises to 63.2% of the remaining 36.8%, or a total of 86.4%. It takes about five time constants for current to reach its maximum value.
Similarly, when the switch is opened, it will take five time constants for current to reach zero. It can be seen that inductance is an important factor in AC circuits. If the frequency is60 hertz, current will rise and fall from its peak value to zero120 times a second.
CALCULATING THE TIME CONSTANT OF AN INDUCTIVE CIRCUIT:
The time constant is designated by the symbol t. To determine the time constant of an inductive circuit use one of the following formulas:
T (in seconds) = L (henrys) / R (ohms)
T (in milliseconds) = L (mill henrys)/ R (ohms)
In the following illustration, L1 is equal to 15 mill henrys andR1 is equal to 5 W. When the switch is closed, it will take 3milliseconds for current to rise from zero to 63.2% of its maximum valueFORMULA FOR SERIES INDUCTORS:

Lt = L1+L2+L3+L4
Lt = 2mh+2mh+1mh+1mh = 6mh
FORMULA FOR PARALLEL INDUCTORS:
In the following circuit, an AC generator is used to supply electrical power to three inductors. Total inductance is calculated using the following formula:

1/Lt = 1/5 + 1.10 + 1/20 = 7/20
Lt = 2.86 mh
CAPACITANCE AND CAPACITORS:
Capacitance is a measure of a circuit's ability to store an electrical charge. A device manufactured to have a specific amount of capacitance is called a capacitor. A capacitor is made up of a pair of conductive plates separated by a thin layer of insulating material. Another name for the insulating material is dielectric material. When a voltage is applied to the plates, electrons are forced onto one plate. That plate has an excess of electrons while the other plate has a deficiency of electrons. The plate with an excess of electrons is negatively charged. The plate with a deficiency of electrons is positively charged
Direct current cannot flow through the dielectric material because it is an insulator. Capacitors have a capacity to hold a specific quantity of electrons. The capacitance of a capacitor depends on the area of the plates, the distance between the plates, and the material of the dielectric. The unit of measurement for capacitance is farads, abbreviated "F". Capacitors usually are rated in mF (microfarads), or pF (Pico farads).
CAPACITOR CIRCUIT SYMBOLS
Capacitance is usually indicated symbolically on an electrical drawing by a combination of a straight line with a curved line, or two straight lines.
SIMPLE CAPACITIVE CIRCUIT:
In a resistive circuit, voltage change is considered instantaneous. If a capacitor is used, the voltage across the capacitor does not change as quickly. In the following circuit, initially the switch is open and no voltage is applied to the capacitor. When the switch is closed, voltage across the capacitor will rise rapidly at first, then more slowly as the maximum value is approached. For the purpose of explanation, a DC circuit is used.
CAPACITIVE TIME CONSTANT
The time required for voltage to rise to its maximum value in a circuit containing capacitance is determined by the product of capacitance, in farads, times resistance, in ohms. This is the time it takes a capacitor to become fully charged. This product is the time constant of a capacitive circuit. The time constant gives the time in seconds required for voltage across the capacitor to reach 63.2% of its maximum value. When the switch is closed in the previous circuit, voltage will be applied. During the first time constant, voltage will rise to 63.2% of its maximum value. During the second time constant, voltage will rise to63.2% of the remaining 36.8%, or a total of 86.4%. It takes about five time constants for voltage across the capacitor to reach its maximum value.

Similarly, during this same time, it will take five time constants for current through the resistor to reach zero

CALCULATING THE TIME CONSTANT OF A CAPACITIVE CIRCUIT:
Time constant is decided by the symbol "T". To determine the time constant of a capacitive circuit, use one of the following formulas:
T (in seconds) = R (megohms) X C (microfarads)
T (in microseconds) = R (megohms) X C (pico farads)
T (in microseconds) = R (ohms) X C (microfarads)
In the following illustration, C1 is equal to 2 mF, and R1 is equal to 10 W. When the switch is closed, it will take 20 microseconds for voltage across the capacitor to rise from zero to 63.2% of its maximum value. There are five time constants, so it will take 100 microseconds for this voltage to rise to its maximum value.



FORMULA FOR SERIES CAPACITORS:
Connecting capacitors in series decreases total capacitance. The effect is like increasing the space between the plates. The rules for parallel resistance apply to series capacitance. In the following circuit, an AC generator supplies electrical power to three capacitors. Total capacitance is calculated using the following formula:
1/Ct = 1/C1+1/C2+1/C3

1/Ct = 1/5+1/10+1/20 = 7/20 = 2.86

FORMULA FOR PARALLES CAPACITORS:
In the following circuit, an AC generator is used to supply electrical power to three capacitors. Total capacitance is calculated using the following formula:
Ct = C1+C2+C3

INDUCTIVE AND CAPACITANCE REACTANCE:
In a purely resistive AC circuit, opposition to current flow is called resistance. In an AC circuit containing only inductance, capacitance, or both, opposition to current flow is called reactance. Total opposition to current flow in an AC circuit that contains both reactance and resistance is called impedance designated by the symbol Z. Reactance and impedance is expressed in ohms.
INDUCTIVE REACTANCE:
Inductance only affects current flow when the current is changing. Inductance produces a self-induced voltage (counter emf) that opposes changes in current. In an AC circuit, current is changing constantly. Inductance in an AC circuit, therefore, causes a continual opposition. This opposition to current flow is called inductive reactance, and is designated by the symbol XL. Inductive reactance is dependent on the amount of inductance and frequency. If frequency is low current has more time to reach a higher value before the polarity of the sine wave reverses. If frequency is high current has less time to reach a higher value. In the following illustration, voltage remains constant. Current rises to a higher value at a lower frequency than a higher frequency.



In a 60 hertz, 10 volt circuit containing a 10 mh inductor, the inductive reactance would be:
XL = 2 x 3.14 x 60 x .010 = 3.768 ohms
Once inductive reactance is known, Ohm's Law can be used to calculate reactive current.
I = E/Z = 10/3.768 = 2.65 amps

PHASE RELATIONSHIP BETWEEN CURRENT AND VOLTAGE IN AN INDUCTIVE CIRCUIT:
Current does not rise at the same time as the source voltage in an inductive circuit. Current is delayed depending on the mount of inductance. In a purely resistive circuit, current and voltage rise and fall at the same time. They are said to be in phase. In this circuit there is no inductance; resistance and impedance are the same.

In a purely inductive circuit, current lags behind voltage by 90 degrees. Current and voltage are said to be "out of phase". In this circuit, impedance and inductive reactance are the same.

All inductive circuits have some amount of resistance. AC current will lag somewhere between a purely resistive circuit, and a purely inductive circuit. The exact amount of lag depends on the ratio of resistance and inductive reactance. The more resistive a circuit is, the closer it is to being in phase. The more inductive a circuit is, the more out of phase it is. In the following illustration, resistance and inductive reactance are equal. Current lags voltage by 45 degrees


When working with a circuit containing elements of inductance capacitance, and resistance, impedance must be calculated. Because electrical concepts deal with trigonometric functions, this is not a simple matter of subtraction and addition. The following formula is used to calculate impedance in an inductive circuit:
In the circuit illustrated above, resistance and inductive reactance are each 10 ohms. Impedance is 14.1421 ohms. A simple application of Ohm's Law can be used to find total circuit current.
VECTORS:
Another way to represent this is with a vector. A vector is a graphic representation of a quantity that has direction and 50 miles southwest from another. The magnitude is 50 miles,and the direction is southwest. Vectors are also used to show electrical relationships. As mentioned earlier, impedance (Z) is the total oppositon to current flow in an AC circuit containing resistance, inductance, and capacitance. The following vector illustrates the relationship between resistance and inductive reactance of a circuit containing equal values of each. The angle between the vectors is the phase angle represented by the symbol q. When inductive reactance is equal to resistance the resultant angle is 45 degrees. It is this angle that determines how much current will lag voltage.

CAPACITANCE REACTANCE:
Capacitance also opposes AC current flow. Capacitive reactance is designated by the symbol XC. The larger the capacitor, the smaller the capacitive reactance. Current flow in a capacitive AC circuit is also dependent on frequency. The following formula is used to calculate capacitive reactance:
Xc = 1/2 x 3.14 x f x C
Capacitive reactance is equal to 1 divided by 2 times pi, times the frequency, times the capacitance. In a 60 hertz, 10 volt circuit containing a 10 microfarad capacitor the capacitive reactance would be:
Xc = 1/2 x 3.14 x f x C = 1/ (2 x 3.14 x 60 x 0.000010) = 265.39 ohms
Once capacitive reactance is known, Ohmís Law can be used to calculate reactive current.
I = E/Z = 10/ 265.39 = 0.0376 amps
PHASE RELATIONSHIP BETWEEN CURRENT AND VOLTAGE IN A CAPACITIVE CIRCUIT:

The phase relationship between current and voltage are opposite to the phase relationship of an inductive circuit. In a purely capacitive circuit, current leads voltage by 90 degrees.All capacitive circuits have some amount of resistance. AC current will lead somewhere between a purely resistive circuit and a purely capacitive circuit. The exact amount of lead depends on the ratio of resistance and capacitive reactance.The more resistive a circuit is, the closer it is to being in phase. The more capacitive a circuit is, the more out of phase it is. In the following illustration, resistance and capacitive reactance are equal. Current leads voltage by45 degrees
CALCULATING IMPEDENCE IN A CAPACITIVE CIRCUIT:
The following formula is used to calculate impedence in a capacitive circuit
In the cirucuit illustrated above, resistance and capacitivef reactance are each 10 ohms. Impedence is 14.1421 ohms

The following vector illustrates the relationship betweenresistance and capacitive reactance of a circuit containingequal values of each. The angle between the vectors is thephase angle represented by the symbol q. When capacitivereactance is equal to resistance the resultant angle is -45degrees. It is this angle that determines how much currentwill lead voltage.



































PROJECT REPORT REDUCTION OF YARN BREAKAGES IN WEAVING

Posted by MuNaWaR

Objective

The purpose of this project is to study the factors which causes and influence the yarn breakages also the practical step needed to reduce the breakages of both warp and weft yarns on the loom.
1. Importance of yarn breakages in weaving process
In the weaving industry it is always emphasized to increase production and maintain quality of woven fabric so the mill can meet the demands of both national and international quality familiar consumers and markets. Also Competitiveness is the main feature of the textile industry in future. The main issue is able to compete at international levels. It is clear from many international exhibitions that the competition will be very brutal in the coming years. Nowadays many mills are able to produce similar quality of the woven fabric. Therefore the main issue is the cost of grey cloth per meter. In order to lower the production costs per meter of woven fabric the yarn breakages are essential to be reduced at every stage of manufacturing the woven fabric. In weaving industry one of the most frequent facing problems is breakages of both warp and weft yarns which not only reduce the production rate and also deteriorate the quality of the produced fabric. These breakages on the preparatory processes and also on loom produce lots of problems and become labor intensive. Lesser the number of yarn breakages lesser will be the defects. So by reducing these breakages of both warp and weft yarns not only increase the productivity of the processes involved to the production of fabrics including warping, sizing etc maintain quality of the woven fabric can be increased but also reduces wastages of yarn, and energy ultimately the cost per meter/yard of the prepared fabric reduces.
1.1. Effect of yarn breakages on efficiency:It is generally observed and the analysis of the loom stoppage revealed that one breakage per loom per 100,000 picks looses considerably efficiency and at every loom stop there is a chance for a defect to come. So it is very important to note that the end breakage rate cone winding, weft winding, warping, sizing and finally onto the loom has to be controlled as minimum as possible. In order to control end breakage rate different quality control measures are taken in each process. Analysis of the requirements of the weaving mill show that no more than one stop per 100,000 m of weft yarn should occur. As soon as two or more stops per 100,000 m of yarn are available in the high production weaving mill, costs will increase as a result of a reduction in efficiency. If one takes as an example a ring-spun yarn with a yarn count of 20 tex (Ne 30) and a cop weight of 50 g, then at the most one weak place every 41 cops (which could result in a stopping of the machine) would be acceptable. Today, less than 0.4 stops per 1,000 warp threads and 100,000 picks are considered acceptable.
1.2. Benefits of reduction of yarn breakages
1.2.1. Cost Reduction:
When we reduce the yarn breakages the loom, the cost is also reduced. If there are stoppages at the loom because of any yarn breakages problem than it will be repaired and some cost will increase in this manners. When we entangled this problem which cause the loom to stop, the cost automatically goes down.

1.2.2. Man Power:
After resolving the problem which cause loom to stop man power will also b reduced. If there is problem of yarn breakage constantly at the loom than a person will be required to handle this situation, and when we solve this problem than there will be no need of person constantly at the loom.

1.2.3. Effect on Production:
When there is problem of yarn breakage or problem in the mechanical part of loom, the loom will stop to work. In this way the productivity of loom will be affected and when we solve these problems production will also be increased.

1.2.4. Quality of Fabric:
Yarn breakages on the loom also affect the quality of fabric. When there is constant breakage of yarn and there is definite knotting for this problem. It will damage the quality of fabric. When these problems are solved the quality will also be improved.

1.2.5. Wastages of Yarn:
Constant yarn breakages on loom due to different problems also cause the wastage of yarn .This problem will also be solved by reducing the yarn breakages on the loom.
1.2.6. Loom Efficiency:
When the yarn breakages occur because the looms to stop are reduced the loom shut down will also be reduced. This will affect the efficiency of loom and it will increase.
1.2.7. Department Efficiency:
When there are some problems in weaving department and suppose 10 looms out of 100 looms are not working, it will affect the department efficiency and it reduced 10% straight away and when the different problems are solved out the department efficiency will also increase.

1.2.8. Reduction of Start Mark:
Start Mark is a sign which comes on the surface of the fabric when a loom is restarted after a shut down. When there is any problem due to which loom gets off again and again it will leave a “Start Mark” at the surface of fabric and it effect the fabric very badly. After solving the problem this effect will also be reduced and a good quality fabric will obtain.

1.2.9. Convenience for post-weaving operations:
The reduction of yarn breakages will produce lots of convenience for the post weaving operations like wet processing etc

1.3. Types of loom stoppages:
The loom stoppages occur due to the following reasons.

1. Breakages of warp yarn
2. Breakages of weft yarn
3. Malfunctioning of some important of mechanisms of loom or basic loom motion.
4. Temperature and humidity of weaving depart

1.4. Factors influence the reduction of yarn breakages:
There are many factors which influence the yarn breakages on loom, though their contribution rations are quite different respectively

· Quality of yarn
· Preparation of warp beam & weft package
· Condition of loom (mechanical, electrical, electronic)
· Atmospheric condition of weave room.
1.5. Loom stoppages measuring units:
Loom stoppages can be calculated in stoppages per unit length of the fabric or per unit time of production. But the most suitable way to describe is stoppages/no of picks and usually no of picks are taken in the unit are 100,000 picks. Different styles of fabric have different value of weft density or no of picks per certain length of fabric such as picks/inches, pick/meter or picks/yard etc. Weft yarn value or pick density gives the exact value of length of fabric wherever it is to be mentioned. So the stoppages per 100,000 are commonly being use determine the stoppages of machines.
1.6. Practical measures for the reduction of yarn breakages:
There is need of implementation of following practical steps to reduce the yarn breakages.

¨ Ensure that the yarn coming from spinning must have the suitable characteristics of strength, hairiness, thick places, thin places, neps, and elongation according to the standards for different yarn counts.

¨ Prepare the report of yarn breakages in each preparatory process so the feed back may provided to the beck process for instance to spinning mills etc.

¨ Ensure the proper sizing with different chemicals by appropriate add on percentage.

¨ Study the yarn breakage due to different mechanical, electronic, and electrical parts of the loom and rectify them.

¨ Compare the yarn breakage rate of different looms and position them either they are effective or not.

¨ Study and prepare report of loom stoppages on the different loom having same qualities or not so better awareness may obtain about machine.

¨ Prepare & access the report of loom stoppages on the same type of looms having same qualities or not so better information regarding yarn breakages may obtain about loom.

¨ Study and define the defects, quality deterioration cases cause by the yarn breakages

2. Properties of yarn selection for weaving:
The choice of the yarn for weaving will necessitate purchase of yarn with CSP in the range of 2000 - 2500 depending on count even though yarn with a lesser CSP will also run. It is better to invest a little more in better raw material and benefit by lesser loom stoppages, better loom efficiency and reduced fabric damages. Yarn stoppages particularly warp yarn stoppages are attributable mainly to raw material quality and/or its preparation for weaving. It is therefore essential the right quality of yarn is purchased for the weaving. The selection of the yarn for production of fabric is a very sensitive matter because this selection affects the efficiency of different process for the production of fabric like weft winding, warping, and sizing and different loom operations. Ultimately the quality of the produced fabric is influenced by the selection of yarn. The selection of the yarn is done according to the requirements of finished fabric. In order to reduce yarn breakage, increase productivity of both machines and labor also the quality of the produced fabric it is essential to select the appropriate yarn for the production of fabric. The selected yarn should meet the predefined standards of yarn strength, yarn hairiness, yarn imperfections (thin, thick places and neps), twist per inch (TPI), yarn elongation and the most important factors. The yarn should be composed of good raw material like cotton of good staple length, maturity, fineness etc. There are different standards for different counts of ring spun yarns (carded/combed) which are given below. For each yarn count there are different standard values of factors e.g. yarn strength, Twist per inch, elongation, hairiness, thin places, thick places and neps.
During selection of yarn the following properties are needed to consider in order reducing breakages of yarns. These are as follows

· Twist in yarn
· Tensile strength
a)Single yarn strength
b)Lea strength
· Elongation
· Hairiness
· Yarn imperfection ( thin, thick places and neps)

2.1. Twist in yarn:
There are two types of twist i.e. Z-twist or clockwise twist and other one is S-twist these directions of yarns have not any effect on the strength of yarn, elongation, lusture, compressibility and compactness but affect the appearance the fabric.
Twist per inch can be calculated by T.P.I=T.F √cotton (Ne)

2.1.1. How the yarn strength is affected by the number of twists?
The strength of the yarn increases with the increase in TWIST FACTOR (T.F) so it reduces the yarn breakages but after certain limit this increment in the twist will reduce the strength of the yarn as shown in the graph. Ultimately the yarn breakages rate will be high. So in order to reduce the yarn breakage there should be appropriate twist in the yarn.

Staple yarn can not be spun below a certain value of T.F. At low T.F yarns breaks mainly as result of fiber slippages. However, the T.F increases the angle of the fiber to the yarn axis increase as the strength of the yarn will decrease and yarn breakages rate will be high.

2.1.2. How the yarn elongation is affected by the twist of yarn?
Twisting of fibers contraction in length when yarns twisted some of these tends to recover when the yarn faces tension so the elongation tends to increase with this twist factor. The strength of the yarn in increased and elongation is reduced by an increase in spinning tension, presumably because this produces a more compact and cohesive yarn. This reduction in elongation is not good when such yarns are subjected to the weaving. The rate of ends thus will increase and productivity and quality will be affected. So to reduce the breakages rate the appropriate T.F is used which does not affect the elongation.

2.1.3. How the yarn absorption is affected by the twist of yarn?
The twist of the yarn also affects the absorption the yarn in different processes like sizing. The no of twist in yarn is inversely proportional to the absorption of yarn i.e. high the twist less will be the absorption. This factor is most important before the selection of the yarn other wise the yarn will not get the sizing paste into its core and yarn strength also other purposes of the sizing will not obtain. Ultimately the yarn breakages rate will be high.
2.2. Strength of yarn:
This is one of the most important factor which influence yarn breakages. It is the force in gms weight or pound required to break the yarn. It is calculated either by one of the following method.
i. Single yarn tensile strength
ii. Lea strength

2.2.1 Single yarn tensile strength:
In weaving the yarn of each yarn is important because every yarn has to withstand high stress strain during different processes. The yarn should have good strength otherwise it will affect the efficiency of machine and quality of the fabrics. CV% of single yarn strength influences warp stoppages more than any other factor. Higher the single yarn strength lesser will be the yarn breakages. Single yarn strength variability should not exceed 8 % and variability of single yarn twist should not exceed 6% if optimum performance is required

2.2.2. Lea strength:
Lea strength is strength of 120 yards of yarn made on warp reel his lea is tested on the strength tester. Lea strength is also considered during selection of the yarn for the manufacturing of fabric. Higher the lea strength lesser will be the yarn breakages. It can be calculated by the following formula
Lea strength (C.L.S.P) = count × weight in lbs
2.3. Elongation:
The factor of elongation plays a very critical role in reduction of the yarn breakages. The elongation depends upon the length of the fiber and also on T.P.I. different yarns have individual values of elongation. For instance cotton has elongation of 6-7% which gives good power to the yarn against breakages. The elongation of yarn play part in each of the preparatory process e.g. cone winding, warping, sizing and weaving on loom. The sized warp sheet of cotton yarn always should have 4-5% elongation to avoid breakages on loom.
2.4. Hairiness:
The yarns which are spun from the higher percentage of short or medium staple length have high ratio of hairiness. The yarn used for the weaving should also have very low hairiness and uniform distribution of hairs throughout the length of yarn. The remaining hairiness of the yarn is sticked onto the yarn with the help of sizing paste. The yarns with minimum hairiness have low yarn breakage and quality of the fabric is also good. So during selection of yarn this factor should be considered and hairiness of the yarn should be tested on the hairiness determining apparatus, so breakages may control and quality of the end product may consistent. Yarn unevenness affects fabric appearance and should preferably be around 12% - 15 %, U% depending on whether we are using combed yarn or carded yarn. Doubled yarns should have significantly lesser U% and lesser number of yarn defects

2.5. Yarn imperfections (thick places, thin places & neps)
The yarn imperfection includes thin places, thick places and neps which have great influence on the yarn breakage and quality of the fabric. It is generally observed that all thick and thin places in the yarns are weak places, because at think place there is no T.P.I and at thin place more T.P.I than normal while neps in the yarn are either due to presence of immature fibers or due to poor carding operation. Neps tend to create FUZZ during shedding due to their breakage of protruding fibers by interfiber friction. Another quality affecting fabric appearance is yarn imperfections - particularly “neps”. These should not exceed 1000 - 1200 per km for carded yarns and 300 per km for combed yarns. The neps/unit length are measured on the apparatus known as “YARN IMPERFECTION TESTER”
3. Reasons of warp stoppages:
Today, less than 0.4 stops per 1,000 warp threads and 100,000 picks are considered acceptable. Only when one considers that (in each case according to the style) 20,000 m of yarn can be available in the weaving zone for 5 to 10 minutes, does the severity of this requirement really become comprehensible. Yarn hairiness, an important warp characteristic, has always been a factor which has influenced the appearance of the cloth, which was true even long before it could be measured. Varying yarn hairiness, e.g., from package to package, results in weft stripes in a woven fabric. Hairiness is also increasing in importance with respect to the running conditions at all processing stages subsequent to spinning. A high amount of hairiness of the warp yarns can negatively influence the movement of the weft yarn through the shed with air-jet weaving machines, and the weft transfer with rapier weaving machines. The result is usually a stop as a result of a warp. Hairy yarns and structure faults in the yarn, such as neps, often produce threads which cling to each other, particularly with the much smaller shed openings in modern weaving machines. If one increases the warp tension in order to avoid these clinging fibers, more end breaks can result due to weak places. The result of this is that hairiness, as well as hairiness variation and particularly periodic hairiness variation, is of increasing importance with warp yarns, especially with respect to their application on high-production weaving machines.
3.1. Selection of cones/spools for the weft yarn:
In order to produce the sheet of warp yarn cones are used as supply package for warp beam similarly the beams after sizing are brought on the looms for weaving. Meanwhile the weft packages don’t require the preparatory processes like warping and sizing. The cones of yarns are directly brought to the loom so the interlacement of weft and warp yarn may do to produce the woven fabric. Weft insertion rate is high and unwinding is intermittent on shuttle less weaving machines. Hence it is necessary to have a hard wound package. It is essential to have anti patterning device to prevent slough-off on the fabrics. For spun yarns, parallel wound package with core diameter of package of 95 mm and a traverse of 90 mm give a good performance. Smaller core diameter of package increases the unwinding tension and enhances the possibility of high weft breakage. Weft accumulators are to be used on high speed weaving machines when the weft insertion rate is above 1000 m/min. The yarn used for the weft insertion should also free from defects so the yarn breakages may not take place. There should be proper cleaning of the yarn during winding on the looms so defects may remove at this stage. If the yarn defects are not removed at this stage then these defected cone and yarn will increase breakages at loom as result the reduction in the production rate and quality of the fabric will also deteriorate. So in spinning process there should be authentic checks on the removal of yarn defects and also production of a good shaped cones having adequate compactness. Similarly when the bags of cones arrive in the weaving premises concern depart should also test the defects of yarn and cones. The report should be made and also send to the spinning mills so they may take practical steps and preventions to avoid these problems. The yarn should have strength, elongation, minimum hairiness, and minimum neps, thick and thin places. The better the yarn selection for the weft yarn better will be the quality of the produced fabric and minimum the rate of yarn breakages.
3.2. Weft yarn properties:
3.2.1. Importance of Automatic Pirn Winding:
In shuttle weaving the size of the shuttle will determine the maximum size of the pirn that can be used and we should use the pirn that has the longest length so that replenishment, which can cause damages, is less frequent. If the yarn breaks and is not sensed in time or if the pirn runs out and the feeler does not actuate stoppage or transfer in time a potential fault occurs and hence pirns must be wound to maximum density and in a shape that will permit tension free and or uniform tension withdrawal. It will, therefore, be necessary to use suitable automatic pirn winding equipment if we are not using shuttleless looms. This problem is compounded further if multi colour weft is used. In addition to the production of proper pirns it will be necessary to have them colour graded properly. This is essential as it is usual to have some shade variation between the end and beginning of the dyed cone or cheese when package dyeing is used for the dyeing operation. Hank dyed yarn can show still greater variation between lots and has to be guarded against.
3.2.2. Effect of Winding Tension:
Tightly wound pirns with material content of about 25 gms in the case of spun yarns and 15 gms in the case of filament yarns will have to be used in the interest of reduced transfers. In the case of filaments, excess winding tension can caused elongation and result in bright picks which are fabric defects. In earlier years it was usual to be satisfied with yarn of poorer quality characteristics for weft in view of the lesser tensions involved during the process of weaving. Modern high speed weaving machines and methods require higher tensions on both warp and weft, hence they do not permit the use of low quality of yarn. These modern looms also require that yarn quality characteristics for warp and weft must be similar.
3.2.3. Yarn Quality and Type of Loom:
As the weaving industry starts modernizing and installing more modern automatic looms in place of the old non-automatic looms the choice of raw material becomes more critical as the higher investment necessitates keeping the looms running round the clock at efficiencies greater than 90% and this will be possible only with proper raw material quality selection. We cannot afford to take the risks that might have been taken so far as these more expensive looms with their greater production potential can cause greater losses also if they are kept idle or allowed to produce faulty fabric. Modern looms have suitable safeguards to prevent warp breakages and weft breakages from causing defects in the fabric but if the raw material is not selected properly there is a loss in efficiency, which can be costly and has to be avoided
3.3. Requirements of weft yarn for weaving:
In contrast to earlier considerations, a weft yarn today must have a requirement profile as high as that of a warp yarn in order to satisfy the requirements of high-production weaving machines. According to the scientifically-based investigations, a weft yarn must exhibit at least the following quality characteristics as indicated in Table. What have become particularly important, for instance, are the yarn elongation as well as the variations in breaking force and elongation. The Classimat faults can also be considered as weak places, because a thick place fault usually contains less twist than the rest of the yarn, and can easily break when a tensile force is applied. It should be mentioned here that, with a higher variation (i.e., a higher coefficient of variation value of elongation), this can only be compensated by a elongation at break value in order to achieve equivalent running conditions. In terms of the spinning process, this means “Better raw materials, higher yarn twist, etc., certainly result in increased yarn manufacturing costs
4. Effects of yarn conditioning in the reduction of yarn breakages
Moisture in atmosphere has a great impact on the physical properties of textile fibers and yarns. Relative humidity and temperature will decide the amount of moisture in the atmosphere. High relative humidity in different departments of spinning is not desirable so before starting preparatory processes for weaving yarn can be conditioned. But on the other hand, a high degree of moisture improves the physical properties of yarn. Moreover it helps the yarn to attain the standard moisture regain value of the fiber. Yarns sold with lower moisture content than the standard value will result in monetary loss. Therefore the aim of CONDITIONING is to provide an economical device for supplying the necessary moisture in a short time, in order to achieve a lasting improvement in quality. In these days there is a dramatic change in the production level of weaving machines, because of the sophisticated manufacturing techniques. Yarn quality required to run on these machines is extremely high. In order to satisfy these demands without altering the raw material, it was decided to make use of the physical properties inherent in the cotton fibers. Cotton fiber is hygroscopic material and has the ability to absorb water in the form of steam. It is quite evident that the hygroscopic property of cotton fibers depends on the relative humidity. The higher the humidity more will be the moisture absorption. The increase in the relative atmospheric humidity causes a rise in the moisture content of the cotton fiber.
The relative humidity in turn affects the properties of the fiber via the moisture content of the cotton fiber. The fiber strength and elasticity increase proportionately with the increase in humidity. If the water content of the cotton fiber is increased the fiber is able to swell, resulting in increased fiber to fiber friction in the twisted yarn structure. This positive alteration in the properties of the fiber will again have a positive effect on the strength and elasticity of the yarn ultimately lesser will be the yarn breakages
4.1. Yarn conditioning process by XORELLA:
The standard conventional steaming treatment for yarn is chiefly used for twist setting to avoid snarling in further processing. It does not result in lasting improvement in yarn quality. The steaming process may fail to ensure even distribution of the moisture, especially on cross-wound bobbins (cheeses) with medium to high compactness. The thermal conditioning process of the yarn according to the CONTEXXOR process developed by XORELLA is a new type of system for supplying the yarn package. The absence of Vacuum in conventional conditioning chambers prevents homogeneous penetration. The outer layers of the package are also too moist and the transition from moist to dry yarn gives rise to substantial variations in downstream processing of the package, both with regard to friction data and strength. Since the moisture is applied superficially in the wet steam zone or by misting with water jets, it has a tendency to become re-adjusted immediately to the ambient humidity level owing to the large surface area. Equipment of this king also prevents the optimum flow of goods and takes up too much space.
4.2. Principle of working:
Thermal conditioning uses low-temperature saturated steam in vacuum. With the vacuum principle and indirect steam, the yarn is treated very gently in an absolutely saturated steam atmosphere. The vacuum first removes the air pockets from the yarn package to ensure accelerated steam penetration and also removes the atmospheric oxygen in order to prevent oxidation. The conditioning process makes use of the physical properties of saturated steam or wet steam (100% moisture in gas-state). The yarn is uniformly moistened by the gas. The great advantage of this process is that the moisture in the form of gas is very finely distributed throughout the yarn package and does not cling to the yarn in the form of drops. This is achieved in any cross-wound bobbins, whether the yarn packages are packed on open pallets or in cardboard boxes.
4.3. Advantages of process:
Saturated steam throughout the process
Even penetration of steam and distribution of moister
Lowest energy consumption with XORELLA ECO-SYSTEM
Short process time
Absolute saturated steam atmosphere of 50 degree C to 150 degrees C.
No additional boiler required, the steam is generated in the system
Minimum energy consumption(approx. 25 KWh for 1000 kgs of yarn)No tube buckling in case of mad-made yarns
Treatment of all natural yarns, blends, synthetics and microfiber yarns.
low installation and maintenance cost
Preheating for trolleys and plastic tubes to avoid drops (Wool)
Standardized sizes
Length up to 20 meters (66 feet) and max. temperature deviation of 1°C
Various loading and unloading facilities
No contamination of the treated packages
Energy recovery option offered by indirect heating system using steam or hot water
No special location required the systems can be operated next to the production machines.
4.4. Other benefits achieved out of conditioning for weaving
up to 15% fewer yarn breaks due to greater elongation
Less fly, resulting in a better weaving quality
Increased strength
Increased take-up of size, enhanced level of efficiency in the weaving plant
Softer fabrics
4.5. Comments:
Yarn conditioning is not carried out in all the weaving mills although the results of conditioned yarns play a vital role in the reduction of yarn breakages both warp and weft yarn. So yarn conditioning should be considered but keep in mind the additional cost of conditioning machine and cost of steam and other auxiliaries.
4.6. Conclusions:
The choice of the yarn for efficient single yarn weaving will therefore necessitate purchase of yarn with CSP in the range of 2000 - 2500 depending on count even though yarn with a lesser CSP will also run. It is better to invest a little more in better raw material and benefit by lesser loom stoppages, better loom efficiency and reduced fabric damages. Tests should be taken on the yarn for CV% of lea count and CV% of lea strength and yarns, not exceeding 2.5 % for the former and 6% for the latter, can be expected to perform satisfactorily. Similarly single yarn strength variability should not exceed 8 % and variability of single yarn twist should not exceed 6% if optimum performance is required. Whilst these factors affect loom performance, yarn unevenness affects fabric appearance and should preferably be around 12% - 15 % U% depending on whether we are using combed yarn or carded yarn. Another quality affecting fabric appearance is yarn imperfections - particularly “neps”. These should not exceed 1000 - 1200 per km for carded yarns and 300 per km for combed yarns. Doubled yarns should have significantly lesser U% and lesser number of yarn defects. Doubled yarn CSP in the range 2500 -3300 will provide proper weaving performance. The future of the weaving sector of Pakistan will depend on its ability to meet the quality demands of the domestic and export markets. In both markets by reason of fashion changes smaller runs and larger assortments are becoming the rule. For this purpose better looms have to be installed - Shuttle, Automatic and Shuttleless Looms - and these have to be operated round the clock at over 90% efficiencies and utilization. This will be feasible only with the use of good quality yarn which conforms to specifications for efficient weaving on the basis of low variability in count, strength, low unevenness and with minimum defects which affect performance and fabric visual appearance. Proper material handling has to be insisted upon, so that the material moves from spinning mill to warping / sizing and, thereafter to looms without damage to material, if one has to meet the stringent quality demands. As blend yarns acquire oil stains easily and fabric can be damaged it is essential that proper weft and warp handling procedures are followed at all stages.

KNITTING CALCULATIONS

Posted by MuNaWaR

KNITTING CALCULATIONS

Knitted fabric is made with the help of yarn loops. Yarn of different counts is used to produce fabric of different grammage. There is also a need to calculate optimum production of knitting machines. It is the job of knitting manager to do certain calculation for proper use of machines and production of fabric according to the demands of the customer. This chapter is aimed at explanation of different calculations.

Most suitable count for knitting machines

As it has been discussed in Chapter Two that needle hook has to take yarn to convert it into a loop and finally latch has to close the needle hook so that loop is properly held by the needle hook and ultimately this helps in passing new loop through the previously held loop. It is clear from this explanation that there should be a proper balance between needle hook size and the thickness of the yarn or filament. If the yarn is thicker than needle hook then there will a chance that needle hook will not able to hold this loop and consequently there will be a small hole in the fabric. If the situation is reverse, means yarn is thinner than the size of the needle hook then the fabric produced will look like a net. Both situations are not wanted. This situation demands a balance between needle hook size and count of yarn. It is worth to note that needle hook size depends upon the machine guage. Furthermore for different garments, fabric of different grammage is required. Every time knitter has to decide about the yarn count. There are many ways for the selection of proper count. In the following lines we will discuss most common methods to select count for different machines of different guage. It is also important to note that selection of yarn counts also depends upon the machine manufactures and type of machines, like, single and double knit machine. However a general guideline will be given hereunder.

As a thumb rule knitting experts prefer to use such knitting machine whose gauges is near to count of yarn (English count) i.e. for 20-gaugemachines most suitable yarn count is 20s. This rule is has certain limitations, like, for 28-gauge yarn of 26s to 30s is most suitable. But for very fine counts this rule is not applicable and also machines have maximum gauge 32. Normally fine counts are not used as such rather they are make double, like count 60s double, which means that net count is near to 30s. And this 60 double count is suitable for 30-gauge machine.
To solve this problem some authors have suggested following formulas.

For single Knitting Machine
Suitable count = G*G/18

For Double knitting machine
Suitable count= G*G/8.4
Where G is gauge of knitting machine

Some knitting machine manufacturers suggest a range of yarn count for their machine. There is another way to solve this problem and that is to take help from old record. Every firm is producing many types of fabrics and on the basis of experience they develop a database for ready reference. In the following line we give a table for guidance (table is under construction). One can get a ready reference from the table to produce fabric of certain grammage. We are also giving expected width of fabric after wet processing. This table can provide just a reference. Knitters have to decide by themselves after doing a trial production, since there are many more factors, which can affect yarn and gauge selection process.


Knitting Machine Parameters
Every knitting machine is made to fulfil certain demands of the customer. There are number of characteristics of machine which are intimated by the machine manufacturers while delivering the machine to customers/users. It is helpful for the user to be well aware about these parameters. Furthermore machine specifications are given in different unit. We will explain these parameters and will also give the conversion factors to convert parameters from one system to other.

Machine Gauge
As per Oxford Dictionary the word “gauge” is a noun and as well as verb. It is used to measure level of any thing or for an instrument to measure width, length or height of any thing. In knitting it is used to express the number of needle in a unit length of the needle bed. This needle bed may flat or circular. In double knit circular machine it is used for cylinder and as well as dial. Generally gauge is defined as number of needles per inch. According to German standard DIN 60917 (Iyer et al1995) alphabet “E “ is used to denote knitting machine gauge.


E = Number of needles
1 inch (25.4 mm)

Machine Pitch
As per German DIN 62125 (Iyer et al1995) the notation “gauge” is to be avoided in the future. Rather they prefer to use notation “pitch” for comparison purpose. Machine Pitch means the distance between the centres of two neighbouring needles. It is denoted with small “t”. It is given in mm.



Knitting Machine Production calculation

Before explaining the method to calculate the nominal production capacity of the knitting machine it is imperative to be well aware of count and denier system and one should also be familiar with the conversion factors. Yarn is sold and purchased in the form of cones and bags. Cones and bags have certain weights. Still in the international market yarn is sold in pounds not in kilograms. Bags are of 100 pounds, which is equal to 45.3697 kgs. Previously there were 40 cones in a bag but now there are bags available of 25 cones. In other words cones are of 2.5 pounds and four pounds. Big size cones are most suitable for knitting. When these cones are used in warping then there is a need to know the length of certain weight of yarn. And some time length is available and some one wants to know the weight of the yarn and in some cases count of the yarn is required. In the following lines we will give methods to calculate above-mentioned figures.
It is imperative to be well aware of count system. In the end of the book we have given different tables and explanation of different terms. Before going ahead students are asked to consult tables and explanation for better understanding of this chapter.

Relationship between count, length and weight of yarn
Length (in yards) = Count *840 *weight of yarn in pound
Count = Length / weight of yarn in pounds*840
Weight of yarn = length/count *840

Note: as per definition count is a relationship between length and weight of yarn. English count is defined as number of hanks in one pound. Hank means a certain length. It is different for different fibers. For details see tables given in the end of book. For explanation purpose we will use English count of cotton. For cotton length of hank is 840 yards. For other fibers use relevant length of hank

Examples:
Example:01
Calculate count of cotton yarn from the given data:
Weight of yarn = 2.68 pounds
Length of yarn = 33600 yard

Formula: Count = Length / weight of yarn in pounds*840
=33600/2.68*840
Answer =14.93s

Example :02
Calculate length of cotton yarn from the given data:
Weight of yarn = 3.5 pounds
Count = 40s

Formula: Length (in yards) = Count *840 *weight of yarn in pound
= 40*840*3.5
Answer =117600 Yards

Example :03
Calculate weight of cotton yarn from the given data:
Length of yarn = 40600 yards
Count = 30s

Formula:
Weight in pounds = Length of yarn in yards/ Count *840
= 40600/30*840
Answer = 1.61 pounds

Next examples are related to filament. Note that for filament we use direct system. In which most popular is denier. There are other units too. For detail consult the tables at the end of the book. Denier is number of grams per 9000 meters of filament.

For calculation related to denier we use following equations:

Length of filament in meters = Weight of filament in grams* 9000
Denier

Weight of filament in grams = Length in meters * denier 9000


Denier = 9000* Weight of filament in grams
Length of filament in meters


Example 4

Calculate length of polyester filament from the given data:
Weight 690 grams
Denier 75

Equation: Length of filament in meters = Weight of filament in grams* 9000
Denier
= 690 * 9000
75
Answer =82800 meters

Example 5

Calculate weigh of polyester filament from the given data:

Length in meters = 50900
Denier = 50

Equation: Weight of filament in grams = Length in meters * denier 9000

= 50900*50
9000
Answer =282.8 grams

Example 6
Calculate denier of polyester filament from the given data:

Length in meters = 550,000
Weight = 4.5 kgs (4500 grams)

Equation: Denier = 9000* Weight of filament in grams
Length of filament in meters

= 9000*4500
550,000

Answer= 73.66 Denier
Note: this calculation is up to two digits. For more accurate answers use calculation up to 9 digits.
Nominal Production of knitting machines
One very simple way to calculate knitting machine production by weighing the total production of one hour or one shift or one day. This will be most realistic production value but we cannot get knitting machine capacity in this way. There is a scientific way to calculate optimum production figure of any machine. This needs certain information and some calculation. In the following lines we will explain this method in detail and will give some example so that one can be familiar to this process. In the end we will give an equation to calculate the knitting capacity of the machine. In this method following information for production calculation are required:

• Machine Guage and Dia
• RPM Knitting Machine
• Yarn Count
• Stitch Length

From these figures we can calculate the length of yarn being used by the machine in one hour and then by converting this length into weight with the help of count given we can calculate the quantity of yarn being consumed by machine in one hour. This would be the optimum production of the machine. This optimum production can be converted into nominal production by multiplying it with efficiency. In the following pages we will explain this with few examples.


In the following pages we will explain the method to calculate nominal production capacity of knitting machine. It is commonly believed that we can run knitting machine up to 85% efficiency. However, by creating most suitable environment one can increase machine efficiency.


For this we need following figures:
Machine speed RPM
Machine guage
Machine Dia
Count/ denier of yarn being used
Stitch length

From the above-mentioned figures we can calculate the length of yarn being used in one revolution and if we know the length and count of yarn then it is quite easy to calculate weight of yarn (see Example: 03 for more details)


Example 07
Calculate nominal production of a single jersey-knitting machine per hour from the data given:
Machine Gauge 24
Machine Dia 30 inches
Number of Feeders 90
Machine RPM 26
Yarn Count 24
Stitch length 4 mm
Efficiency 85%
Solution:
Step one
First we will calculate number of needles and number of stitches produced in one revolution. This would help us in calculating the total length of yarn consumed in one revolution.
Number of needles = machine dia * gauge *  (3.14)
= 30* 24*3.14
=2260 (exact 2260.8 but needles are always in even number
so we will take nearest even figure)

Number of stitches produced in revolution
Every needle is making one stitch on every feeders because machine is producing single jersey fabric (full knit fabric).
Number of stitches produced in one revolution = Number of needles * number of feeders
= 2260*90
= 203400
This figure shows that machine is making 203400 stitches in one revolution.

Step Two
Length of stitch is 04 mm (stitch length is always calculated in metric system)
From this figure we can calculate yarn consumption in yards in one hour

Yarn Consumption (in yards) in one hour
= number of stitches * length of (mm) * RPM *60 (minutes)
1000(to convert mm into meters)

=203400 * 4 * 26 * 60
1000
= 1269216 meters or
= 1388015 yards

Step Three
In previous step we calculated quantity of yarn consumed in yards. We can easily calculate weight of this yarn while its count is known (see example 03).

Weight of cotton yarn = length of yarn
Count * 840

= 1388015
840 * 24
= 68.85 pounds or
= 31.23 Kilo grams
Efficiency 85% = 26.55 Kilo grams
Answer: this machine can produce 26.55 Kgs fabric in one hour at 85 % efficiency

Example 08
For Filament yarn
Calculate nominal production of a single jersey-knitting machine per hour from the data given:
Machine Gauge 28
Machine Dia 26 inches
Number of Feeders 120
Machine RPM 30
Yarn Denier 75
Stitch length 4.5 mm
Efficiency 85%
Solution:
Step one
First we will calculate number of needles and number of stitches produced in one revolution. This would help us in calculating the total length of yarn consumed in one revolution.
Number of needles = machine dia * gauge *  (3.14)
= 26* 28*3.14
=2286 (exact 2285.92 but needles are always in even number so we will take nearest even figure)

Number of stitches produced in revolution
Every needle is making one stitch on every feeder because machine is producing single jersey fabric (full knit fabric).
Number of stitches produced in one revolution = Number of needles * number of feeders
= 2286*120
= 274320
This figure shows that machine is making 274320 stitches in one evolution.

Step Two
Length of stitch is 04.5 mm (stitch length is always calculated in metric system)
From this figure we can calculate yarn consumption in yards in one hour

Yarn Consumption (in yards) in one hour
= number of stitches * length of (mm) * RPM *60 (minutes)
1000(to convert mm into meters)

=274320 * 4.5 * 30 * 60
1000
= 2221992 meters

Step Three
In previous step we calculated quantity of yarn consumed in yards. We can easily calculate weight of this yarn while its count/denier is known (see example 05).

Weight of filament in grams = Length in meters * denier 9000

= 2221992*75
9000
Answer =18516 grams or
=18.516 Kgs

Efficiency 85% = 18.516*85%
=15.74 Kgs

Answer: this machine can produce 15.74 Kgs fabric in one hour at 85 % efficiency

Note: if we are producing any textured fabric, like fleece, then we use two different yarns at different feeders and ultimately stitch length is also different. In such case we should calculate separately consumption of different yarn at different feeders. Following example will help in calculating production in case of use of more than one kind yarn.

Example 9
Calculate nominal production of a fleece-knitting machine per hour from the data given:
Machine Gauge 18
Machine Dia 30 inches
Number of Feeders for 60
Front yarn
Number of feeders 30
For loop yarn
Machine RPM 28
Yarn Count 26s for front
Yarn count for loop 16s
Stitch length of 4.5 mm
front yarn
Stitch length of 2.5 mm
Loop yarn
Efficiency 85%
Solution:
Step one
First we will calculate number of needles and number of stitches produced in one revolution. This would help us in calculating the total length of yarn consumed in one revolution.
Number of needles = machine dia * gauge *  (3.14)
= 30* 18*3.14
=1696 (exact 1695 but needles are always in even number
so we will take nearest even figure)

In this example we will calculate consumption of yarn in Kgs of both yarns and then we will add them to get final production per hour

Consumption of yarn for front knitting
Every needle is making one stitch on every feeder because machine is producing single jersey fabric (front of fleece).
Number of stitches produced in one revolution = Number of needles * number of feeders


= 1696*60
= 101760
This figure shows that machine is making 101760 stitches in one revolution.

Step Two
Length of stitch is 04.5 mm (stitch length is always calculated in metric system)
From this figure we can calculate yarn consumption in yards in one hour

Yarn Consumption (in yards) in one hour
= number of stitches * length of (mm) * RPM *60 (minutes)
1000(to convert mm into meters)

=101760 * 4.5 * 28 * 60
1000
= 769305 meters or
= 841312 yards

Step Three
In previous step we calculated quantity of yarn consumed in yards. We can easily calculate weight of this yarn while its count is known (see example 03).

Weight of cotton yarn = length of yarn
Count * 840

= 841312
840 * 30
= 38.52 pounds or
= 17.43 Kilo grams
Efficiency 85% = 14.85 Kilo grams
Answer: this machine will consume 14.85 Kgs of yarn to knit front of the fleece fabric in one hour at 85 % efficiency
Step Four
Yarn consumed for loop knitting (back of the fabric)
Every needle is making one stitch on every feeder because machine is producing single jersey fabric (front of fleece).
Number of stitches produced in one revolution = Number of needles * number of feeders


= 1696*30
= 50880
This figure shows that machine is making 50880 stitches in one revolution.

Note: that we have put 30 cones of course count for loops after every two feeders.

Step Five
Length of stitch is 2.5 mm (stitch length is always calculated in metric system)
From this figure we can calculate yarn consumption in yards in one hour

Yarn Consumption (in yards) in one hour
= number of stitches * length of (mm) * RPM *60 (minutes)
1000(to convert mm into meters)

=50880 * 2.5 * 28 * 60
1000
= 213696 meters or
= 233696 yards

Step Six
In previous step we calculated quantity of yarn consumed in yards. We can easily calculate weight of this yarn while its count is known (see example 03).

Weight of cotton yarn = length of yarn
Count * 840

= 233696
840 * 16
= 17.39 pounds or
= 7.89 Kilo grams
Efficiency 85% = 6.70 Kilo grams

Step Seven
Now we can add both yarn consumed
Yarn for front 14.85
Yarn for back 6.70
Total 21.55


This machine can produce 21.55 Kgs fabric in one hour at 85% efficiency

All above discussion to elaborate the way to calculate the optimum production of a knitting machine. We have develop a equation which is useful in evey situation to calculate the optimum production capacity of a knitting machine at 85% efficiency.

For cotton count

Production in one hour=

Gauge * Dia * 3.14 * RPM *60 * Stitch length (mm) *1.0936 * 1 * 85
1000 *840 * yarn count * 100

Grammage Expressions

Generally grammage is expressed in Grams per Meter Square (GSM) but in certain cases it is also expressed Ounces per Yard Square (OSY). People, particularly working in marketing and merchandising departments face problems in converting GSM into OSY. We will explain this conversion method with examples before that it is imperative to know the standard conversion factors of different measuring units. A complete conversion chart is given at the end of the book. One should be much familiar with these conversion factors.

Conversion of GSM (grams per square meter) into OSY (ounces per square yard)

250 GSM means that weight of one meter square fabric is 250 grams and 10 OSY means weight on one yard squares is 10 ounces. In the following lines we will explain the method of conversion from GSM to OSY and vice versa with the help of examples.



Example 10

Convert 10 OSY (ounces per square yard) into GSM (grams per square meter).

It means weight of one yard square is 10 ounces or
Weight of one square yard is 280 grams (one ounce is equal to 28 grams) or

Weight of one 0.836 meter square (one yard square is 0.836 meter square) is 280 grams or

Weight of one meter square = 280* 1
0.836

Answer = 344.9 grams per meter square



Example 11

Convert 250 GSM (grams per square meter) into OSY (ounces per square yard)


It means weight of one meter square is 250grams or

Weight of one square meter is 8.93 ounces (28 grams are equal to one ounce) or


Weight of 1.196 yard square (one meter square is equal to 1.196 yard square) is 8.93 or

Weight of one yard square = 8.93* 1
1.196

Answer = 7.47 ounces per yard square


Relation between length, width and grammage

It was observed during interaction with the people working in garment business that they face difficulties in calculation related to grammage, width and length of the fabric. In the following lines we will explain relationship among these factors with examples.

Example 10
Calculate weight of fabric from the given data.

Grammage 300 GSM
Width of fabric 35 inches (in tubular form)
Length of fabric 20 meters

First we will calculate area of the fabric

Area of fabric = Fabric length * fabric width

= 20 * 35*2 (since fabric is in tubular)
39.37 (one meter is equal to 39.37 inches)

= 35.6 meter square

Weight of one meter square is = 300 (GSM)
And weight of 35.6 meter square = 300*35.6
= 10680 grams or 10.680 Kgs


Example 13

Calculate GSM from the data given

Total Weight of fabric = 15.5 Kgs
Length of fabric = 35 meters
Width of fabric in open form = 65 inches


Solution:

First we will calculate area of the fabric

Fabric length = 35 meters
Fabric width = 65 inches or 1.65 meters
Fabric area = Length * width
=35 * 1.65
=57.75 meters square

Weight of 57.75 Meter square is 15.5 kgs or 15500 grams
So weight of one square meter = 15500/57075

= 268.39 grams per meter square of GSM of

the fabric

Calculation of different fibre percentage in knitted fabric

Normally fabrics are knitted with one kind of yarn but in some cases more than one type of yarn of different counts and combination (mixing of two different fibres) are used. One very common example is knitting of fleece fabric, which is knitted by using fine and course yarns, and one yarn is made of polyester and cotton. Another example is knitting of fabric by using spandex filament and cotton or pure polyester. In such condition there is a requirement to mention exact percentage of different fibres in the fabric. Supplier has to mention this ratio on label. In the following lines we discuss the methods to calculate such percentage with the help of examples.

Example
Find exact composition of different fibres in fleece fabric from the following data:
Yarn count front 30s 100 cotton
Yarn count for loop 20s 50:50 P/C
Consumption ratio Front: loop 2:1 (by weight)
Suppose for front we need 2Kg yarn and for loop we will be requiring 1 Kg yarn
Front yarn 2 KGS 100 % cotton Cotton 2000 grams
Loop yarn 1 Kg 50:50 P/C Cotton 500 grams and Polyester
500 grams
Exact Ratio

Cotton total 2.5 Kgs
Polyester 0.5 Kgs

Ratio:
Cotton: 83.33%
Polyester : 16.66