Yarn Conditioning

Textile fibers are subjected to various physical operations to make in to a yarn. For example cotton fiber passes through opening, carding, drawing and spinning to become a yarn. During these phases the original moisture content on the fiber would have been lost and some static electricity would be carried by the fiber. The amount of static current carried by yarn changes from fiber to fiber. Similarly the strength of any fiber depends up on how close the present moisture content is to the original natural value.

Similarly some high twist yarn would tend to loose its twist as and when it is allowed freely, making a lengthwise elongation.

Some fibers would tend to shrink when exposed to hot atmosphere or any treatment that involves heat and hence higher temperature. For example polyamide, polyester etc.

Some blends like Cotton/Lycra, Viscose/Lycra require conditioning to make the width the fabric stable.

So all the above said factors, if not addressed properly would reflect badly on the final quality of yarn or fabric. A process that addresses all the above parameters is called Conditioning. 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.

Conditioning Process for Various Yarns

100% Polyester yarn:

Load the yarn in the form cones wound on plastic cones, in to a beam dyeing machine. Introduce steam and raise the temperature to 100°C at 3°C per minutes. Steam for 15 minutes at 100°C followed by 15 minutes cooling = 1 cycle. Repeat the cycle for 4 times.

100% Nylon:

Load the yarn in the form cones wound on plastic cones, in to a beam dyeing machine. Introduce steam and raise the temperature to 100°C at 3°C per minutes. Steam for 15 minutes at 100°C followed by 15 minutes cooling to a temperature of 50°C = 1 cycle. Repeat the cycle for 4 times.

Silk yarn:

Load the yarn in the form cones wound on plastic cones, in to a beam dyeing machine. Introduce steam and raise the temperature to 70°C at 3°C per minutes. Steam for 15 minutes at 70°C followed by 15 minutes cooling to a temperature for 30°C = 1 cycle. Repeat the cycle for 4 times.

Cotton/Lycra (40's Lycra) or Viscose/Lycra (60's):

Load the yarn in the form cones wound on plastic cones, in to a beam dyeing machine. Introduce steam and raise the temperature to 70°C at 3°C per minutes. Steam for 15 minutes at 70°C followed by 15 minutes cooling to a temperature for 30°C = 1 cycle. Repeat the cycle for 4 times.

Benefits of Conditioning:

For Knitting:

The treatment temperature for knitting yarn is held below the melting point of the wax. Temperatures for unwaxed yarn are coordinated to the compatibility for each individual type of yarn.

• Upto 20% greater efficiency due to a reduction in the unwinding tension
• Fewer needle breaks
• Uniform moisture content and friction values
• Regular stitch formation
• No change in size of finished articles
• No extra dampening required
• Free from electrostatic
• Less fly hence less problems. It helps if the yarn is running on a closer gauge machines.

NOTE: The wax applied should be able to withstand min 60 degree centigrade. If low quality wax is used, it will result in major problem. Conditioning should be done at 55 to 60°C.

For Weaving:

• Upto 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

For Twisting:

• Conditioning and fixing of the twist at the same time in a single process.

For Dyeing:

• No streaks
• Better dye affinity

Terry Towel | Manufacturing Process

Terry Towel, a pile fabric is known as towel worldwide. In terry towel loop piles are present on one or both side of the fabric. Terry fabrics are used in various fields because of their water absorption properties.

Different Parts of a Terry Towel

The parts mentioned on the above image are known in different names like

-Side Hem is named as Selvedge.

-Cross Hem is named as top and bottom hem.

-Borders are called as Dobby.

-Terry Bar is known as Cuff.

A wide variety of towel styles are available in the market. All the above towel parts may not be present in a particular towel.

Manufacturing of Terry Towel:

Terry towel weaving

Terry towel is one type of woven fabrics where during weaving of this fabric 2 beams are used. One beam for ground fabrication and other beam for loop formation. Top beam is responsible for loop formation by terry loom’s beat-up mechanism. Commercially 3 pick terry is most popular. 3 picks terry means after each 3 picks insertion full beat-up is made and one loop pile is formed of the fabric. See the following illustration of beat-up position.

Pile of the towel plays major role for a towel for its water absorbency and other properties. Loop length is decided by the quality, weight etc. as per requirements. Pile manufacturers use better quality yarn like combed, compact, hydro, zero twisted yarns.

Piles are made by different high value fibers like superior qualities of cotton suvin, giza, pima, bamboo, modal etc. to get better absorbency and lint properties. For ground yarn, comparatively coarser counts are used in OE and 2-ply option to give better strength and compactness in ground fabric. Both piles and ground yarns are prepared in the same manner of warping, sizing, and drawing-in.

Wet Processing of Terry Fabric

• Desizing
• Scouring
• Bleaching
• Dyeing
• Finishing

Dyeing Terry Towel Fabrics

Commonly used dyes:

• Reactive dyes

Commonly used machine:

• Winch, Jet/soft flow/overflow: Fabric in rope form
• Pad batch, Pad steam: Fabric in open-width form

Finishing Towel Fabrics

Chemical Finishing:

• Hydrophilic softeners
• Enzymatic softening
• Antimicrobial treatment (If no inherently antimicrobial fiber used)

Mechanical Finishing:

• Tumble drying: Gives softness, fullness, fluffiness
• Stentering:To straighten up fabric and impart dimensional stability

Cutting and Sewing

• Longitudinal cutting
• Longitudinal hemming
• Cross cutting
• Cross hemming

Basic Parameters of a Quality Terry Towel

• Weight & GSM: Weight and GSM should be same as required by customer. Every manufacturer has some template or software (ERPs) where towel manufacturers calculate everything likes pile’s height, density of picks and ends to meet requirement. This database or any software has been developed through some basic calculation.
• Softness/ Hand feel: It depends on properties of the yarn used in pile, finishing chemicals and too some extent on pile orientation.
• Pile Orientation: Totally depends on process line.
• Lint: Lint are basically protruding fibers present in a finished towel. It is measured by weight of accumulated fiber collected from washing machine and tumble drying machine during testing.
• Absorbency: Terry towel should be highly water absorbent.
• Dimensional Stability: How a towel is behaving after washing is fall under dimensional stability properties. Dimensional stability is measured by the residual shrinkage % in a finished towel.
• Other Parameters are strength, color fastness etc.

HVI System | High Volume Instrument System

The testing of fibres was always of importance to the spinner. It has been known for a long time that the fibre characteristics have a decisive impact on the running behaviour of the production machines, as well as on the yarn quality and manufacturing costs. In spite of the fact that fibre characteristics are very important for yarn yarn proudction, the sample size for testing fibre characteristics is not big enough.

Advantages of HVI Testing

• The results are practically independent of the operator.
• The results are based on large volume samples, and are therefore more significant.
• The respective fibre data are immediately available.
• The data are clearly arranged in summerised reports.
• They make possible the best utilisation of raw material data.
• Problems as a result of fibre material can be predicted, and corrective measures instituted before such problems can occur.

Cotton classification does not only mean how fine or clean, or how long a fibre is, but rather whether it meets the requirements of the finished product. To be more precise, the fibre characteristics must be classified according to a certain sequence of importance with respect to the end product and the spinning process.

The ability to obtain complete information with single operator HVI systems further underscores the economic and useful nature of HVI testing.

LENGTH:

The length measure by HVI systems used by the USDA is called upper-half-mean length. This is the average or mean length of the longest one-half of the fibres in the sample. The spin lab system uses the fibrosampler device to load the fibres on needles, the motion control system uses the Specimen Loader to capture the fibres in a pinch clamp. However the preparation of the length specimen for both systems includes combin to straighten and parallel the fibres, and brushing to remove fibre crimp. The length measurement is then made by the instrument scanning along the length of the specimen to determine the length data.

The instruments are calibrated to to read in staple length. Length measurements obtained from the instrument are considerably more repeatable than the staple length determination by the classer. In one experiment the instrument repeated the same staple length determination 44% of the time while the classer repeated this determination only 29% of the time. Similarly, the instrument repeated to 1/32" on 76% of the samples, while the classer agreed on 71% of the samples to within 1/31".

The precision of the HVI length measurement has been improved over the last few years. If we take the same bale of cotton used in the earlier example and repeatedly measure length with an HVI system, over two-thirds of measurements will be in a range of only about 1/32 nd of an inch: 95% of the individual readings will be within 1/32nd of an inch of the bale average. In the 77000 bales tested, the length readings were repeated within 0.02" on 71% of the bales between laboratories.

LENGTH UNIFORMITY:

The HVI system gives an indication of the fibre length distribution in the bale by use of a length uniformity index. This uniformity index is obtained by dividing the mean fibre length by the upper-half-mean length and expressing the ratio as a percent. A reading of 80% is considered average length uniformity. Higher numbers mean better length uniformity and lower numbers poorer length uniformity. A cotton with a length uniformity index of 83 and above is considered to have good length uniformity, a length uniformity index below 78 is considered to show poor length uniformity.

Repeated measurements on a single bale of cotton show the length uniformity index measurement to have relatively low precision. About two-thirds of the measurements will occur within one unit of length uniformity; thus a bale with an average length uniformity index of 80 would have 68% of the readings occuring between 79 and 81, and 95% of hte readings occuring between 78 and 82. This does not seem too bad until one considers that most US upland cottons will have a length uniformity reading between 75 and 85.

Most organizations operate their HVI systems to use an average of 2 or 4 readings per bale for the length uniformity index. Using that number tests per bale, the USDA test of 77000 bales showed that laboratoriesat different locations agreed 68% of the time to within one length uniformity index unit.

In some cases low length uniformity has correlated with high short fibre content. However, in general the correlations between length uniformity index and short fibre content have not been very good. One important reason why the length uniformity index is a not a very good indicator of the short fibre content has to do with the fact that the HVI systems do not measure the length of any fibres shorter than about 4mm.

Another reason for the poor correlations between length uniformity index and short fibre content is that the short fibre content is related to staple length while the length uniformity index is fairly independent of staple length. As an example, the shorter staple cottons tend to contain higher amounts of short fibre than the longer staple cottons. Howeer, many short staple cottons have length uniformity index readings above 80.

MICRONAIRE:

The micronaire reading given by the HVI systems is the same as has been used in the commercial marketing of cotton for almost 25 years. The repeatability of the data and the operator ease of performing the test have been improved slightly in the HVI micronaire measurement over the original instruments by elimination of the requirement of exactly weighing the test specimen. The micronaire instruments available today use microcomputers to adjust the reading for a range of test specimen sizes.

The micronaire reading is considered both precise and reperable. For example, if we have a bale of cotton that has an average micronaire of 4.2 and repeatedly test samples from that bale, over two-thirds of thet micronaire readings will be between 4.1 and 4.3 and 95 %of the readings between and 4.0 and 4.4. Thus, with only one or two tests per bale we can get a very precise measure of the average micronaire of the bale.

This reading is also very repeatable from laboratory to laboratory. In USDA approx 77000 bales were tested per day in each laboratory, micronaire measurements made in different laboratories agreed with each other within 0.1 micronaire units on 77% of the bales.

The reading is influenced by both fibre maturity and fibre fineness. For a given growing area, the cotton variety generally sets the fibre fineness, and the environmental factors control or influence the fibre maturity. Thus , within a growing area the micronaire value is usually highly related to the maturity value. However, on an international scale, it cannot be known from the micronaire readings alone if cottons with different micronaire are of different fineness or if they have different maturity levels.

STRENGTH:

The strength measurement made by the HVI systems is unlike the traditional laboratory measurements of Pressley and Stelometer in several important ways. First of all the test specimens are prepared in a very different manner. In the laboratory method the fibres are selected, combed and carefully prepared to align them in the jaw clamps. Each and every fibre spans the entire distance across the jaw surfaces and the space between the jaws.

In the HVI instruments the fibres are ramdomly selected and automatically prepared for testing. They are combed to remove loose fibres and to straighten the clamped fibres, also brushed to remove crimp before testing. The mechanization of the specimen preparation techniques has resulted in a "tapered" specimen where fibre ends are found in the jaw clamp surfaces as well as in the space between the jaws.

A second important difference between traditional laboratory strength measurements and HVI strength measurements is that in the laboratory measurements the mass of the broken fibres is determined by weighing the test specimen. In the HVI systems the mass is determined by the less direct methods of light absorption and resistance to air flow. The HVI strength mass measurement is further complicated by having to measure the mass at the exact point of breaks on the tapered specimen.

A third significant difference between laboratory and HVI strength measurements is the rate or speed at which the fibres are broken. The HVI systems break the fibres about 10 times faster than the laboratory methods.

Generally HVI grams per tex readings are 1 to 2 units (3 to 5%) higher in numerical value. In some individual cases that seem to be related to variety, the differences can be as much as 6 to 8% higher. This has not caused a great deal of problems in the US, perhaps because a precedent was set many years ago when we began adjusting our Stelometer strength values about 27% to put them on Presseley level.

Relative to the other HVI measurements, the strength measurement is less precise. Going back to our single bale of cotton and doing repeated measurements on the bale we shall find that 68% of the readings will be within 1 g/tex of the bale average. So if the bale has an average strength of 25 g.tex, 68% of the individual readings will be betweeen 24 and 26 g/tex, and 95% between 23 and 27 g/tex.

Because of this range in the readings within a single bale, almost all HVI users make either 2 or 4 tests per bale and average the readings. When the average readings are repeated within a laboratory, the averages are repeated to within one strength unit about 80% of the time. However, when comparisons are made between laboratories the agreement on individual bales to within plus or minus 1 g/tex decreases to 55%.

This decrease in strength agreement between laboratories is probably related to the difficulty of holding a constant relative humidity in the test labs. Test data indicate that 1% shift in relative humidity will shift the strength level about 1% . For example, if the relative humidity in the laboratory changes 3% ( from 63 to 66%), the strength would change about 1 g/tex ( from 24 to 25 g/tex).

COLOUR:

The measurement of cotton colour predates the measurement of micronaire, but because colour has always been an important component of classer's grade it has not received attention as an independent fibre property. However the measurement of colour was incorporated into the very early HVI systems as one of the primary fibre properties.

Determination of cotton colour requires the measurement of two properties, the grayness and yellowness of the fibres. The grayness is a measure of the amount of light reflected from the mass of the fibre. We call this the reflectance or Rd value. The yellowness is measured on what we call Hunter's +b scale after the man who developed it. The other scales that describe colour space (blue, red, green) are not measured becasue they are considered relatively constant for cotton.

Returning once again to the measurements on our single bale, we see that repeated measurements of colour are in good agreement. For grayness or reflectance readings, 68% of the readings will be within 0.5 Rd units of the bale average, and 95% within one Rd unit for the average.

As for yellowness, over two-thirds of these readings will be within on-fourth of one +b unit of the average, and 95% within one-half of one +b unit. The grayness (Rd) and yellowness (+b) measurements are related to grade through a colour chart which was developed by a USDA researcher. The USDA test of 77000 bales showed the colour readings to be the most repeateable of all data between laboratories; 87% of the bales repeated within one grayness(Rd) unit, and 85% repeated within one-half of one yellowness(+b) unit.

TRASH CONTENT:

The HVI systems measure trash or non-lint content by use of video camera to determine the amount of surface area of the sample that is covered with dark spots. As the camera scans the surface of the sample, the video output drops when a dark spot (presumed to be trash) is encountered. The video signal is processed by a microcomputer to determine the number of dark spots encountered (COUNT) and the per cent of the surface area covered by the dark spots (AREA). The area and count data are used in an equation to predict the amount of visible non-lint content as measured on the Shirley Analyser. The HVI trash data output is a two-digit number which gives the predicted non-lint content for that bale. For example, a trash reading of 28 would mean that the predicted Shirley Analyser visible non-lint content of that bale would be 2.8%.

While the video trash instruments have been around for several years, But the data suggest that the prediction of non-lint content is accurate to about 0.75% non lint, and that the measurements are repeatable 95% of the time to within 1% non-lint content.

SHORT FIBRE CONTENT:

The measure of short-fibre content (SFC) in Motion Control's HVI systems is based on the fibre length distribution throughout the test specimen.

It is not the staple length that is so important but the short fibre content which is important. It is better to prefer a lower commercial staple, but with a much lower short-fibre content.

The following data were taken on yarns produced under identical conditions and whose cotton fibres were identical in all properties except for short-fibre content. The effects on ends down and several aspects of yarn quality are shown below:

	LOT -A, (8.6% SFC)	LOT-B (11.6% SFC)
Ends down / 1000 hrs	7.9	12.8
Skein strength (lb)	108.1	97.4
Single end strength g/tex	15	14.5
apperance index	106	89
Evenness (CV%)	16	17.3
Thin places	15	36
Thick places	229	364
Minor Defects	312	389

These results show that an increase of short-fibre content in cotton is detrimental to process efficiency and product quality.

HVI systems measure length parameters of cotton samples by the fibrogram technique. The following assumptions describe the fibrogram sampling process:

• The fibrogram sample is taken from some population of fibres
• The probability of sampling a particular fibre is proportional to its length
• A sampled fibre will be held at a random point along its length
• A sampled fibre will project two ends away from the holding point, such that all of the ends will be parallel and aligned at the holding point.
• All fibres have the same uniform density

The High Volume Instruments also provide empirical equations of short fibre content based on the results of cotton produced in the United States in a particular year.
Short Fibre Index = 122.56 - (12.87 x UHM) - (1.22 x UI)
where UHM - Upper Half Mean Length (inches) UI - Uniformity Index
Short Fibre Index = 90.34 - (37.47 x SL2) - (0.90 x UR)
Where SL2 - 2.5% Span length (inches) UR - Uniformity Ratio

MEASUREMENT OF MATURITY AND SUGAR CONTENT:

Near infrared analysis provides a fast, safe and easy means to measure cotton maturity, fineness and sugar content at HVI speed without the need for time consuming sample preparation or fibre blending.

This technology is based on the near infrared reflectance spectroscopy principle in the wavelength range of 750 to 2500 nanometers. Differences of maturity in cotton fibres are recognized through distinctly different NIR absorbance spectra. NIR technology also allows for the measurement of sugar content by separating the absorbance characteristics of various sugars from the absorbance of cotton material.

Cotton maturity is the best indicator of potential dyeing problems in cotton products. Immature fibres do not absorb dye as well as mature fibres. This results in a variety of dye-related appearance problems such as barre, reduced color yield, and white specks. Barre is an unwanted striped appearance in fabric, and is often a result of using yarns containing fibres of different maturity levels. For dyed yarn, color yield is diminished when immature fibres are used. White specks are small spots in the yarn or fabric which do not dye at all. These specks are usually attributed to neps (tangled clusters of very immature fibres)

NIR maturity and dye uptake in cotton yarns have been shown to correlate highly with maturity as measured by NIR. A correlation of R=0.96 was obtained for a set of 15 cottons.

In a joint study by ITT and a European research organization, 45 cottons from four continents were tested for maturity using the NIR method and the SHIRLEY Development Fineness/ Maturity tester(FMT). For these samples, NIR and FMT maturity correlated very highly (R=0.94).

On 15 cottons from different growth areas of the USA , NIR maturity was found to correlate with r2 = 0.9 through a method developed by the United States Department of Agriculture (USDA). In this method, fibres are cross-sectioned and microscopically evaluated.

Sugar Content is a valid indicator of potential processing problems. Near infrared analysis, because of its adaptability to HVI, allows for screening of bales prior to use. The information serves to selected bales to avoid preparaion of cotton mixes of bales with excessive sugar content. COTTON STICKINESS consists of two major causes- honeydew form white flies and aphids and high level of natural plant sugars. Both are periodic problems which cause efficiency losses in yarn manufacturing

The problems with the randomly distributed honeydew contamination often results in costly production interruptions and requires immediate action often as severe as discontinuing the use of contaminated cottons.

Natural plant sugars are more evenly distributed and cause problems of residue build-up, lint accumulation and roll laps. Quality problems created by plant sugar stickiness are often more critical in the spinning process than the honeydew stickiness. Lint residues which accumulate on machine parts in various processes will break loose and become part of the fibre mass resulting in yarn imperfections. An effective way to control cotton stickiness in processing is to blend sticky and nonsticky cottons. Knowing the sugar content of each bale of cotton used in each mix minimizes day-to-day variations in processing efficiency and products more consistent yarn quality. Screening the bale inventory for sugar content prior to processing will allow the selection of mixes with good processing characteristics while also utilizing the entire bale inventory.

The relationship between percent sugar content by NIR analysis and the Perkins method shows an excellent correlation of r2=0.95. The amount of reducing material on cotton fibre in the Perkins method is determined by comparing the reducing ability of the water extract of the fibre to that of a standard reducing substance. Using the NIR method, the amount of reducing sugar in cotton is measured.

The popularity of HVI testing has steadily gained since the introduction of the technology in the early 1960s.

Timely, valuable information, promotion of communication, standardization of measurements, optimization of processes, development of new products and cost control are the outstanding benefits of technology.

Import and Export Documents

A. Commercial Documents

1. Quotation: An offer to sell goods and should state clearly the price, details of quality, quantity, trade terms, delivery terms, and payment terms. Prepared by Exporter.
2. Sales Contract: An agreement between the buyer and the seller stipulating every details of the transaction. It is a legally binding document. It is therefore advisable to seek legal advice before signing the contract. Prepared by Exporter and Importer.
3. Pro Forma Invoice: An invoice provided by a supplier prior to the shipment of merchandise, informing the buyer of the kinds and quantities of goods to be sent, their value, and importation specifications (weight, size and similar characteristics). This is not issued for demanding payment but may be used when applying for an import licence/permit or arranging foreign currency or other funding purposes. Prepared by Exporter.
4. Commercial Invoice: It is a formal demand note for payment issued by the exporter to the importer for goods sold under a sales contract. It should give details of the goods sold, payment terms and trade terms. It is also used for the customs clearance of goods and sometimes for foreign exchange purpose by the importer. Prepared by Exporter.
5. Packing List: A list with detailed packing information of the goods shipped. Prepared by Exporter.
6. Inspection Certificate: It is a formal demand note for payment issued by the exporter to the importer for goods sold under a sales contract. It should give details of the goods sold, payment terms and trade terms. It is also used for the customs clearance of goods and sometimes for foreign exchange purpose by the importer. Prepared by Inspection Company or Exporter.
7. Insurance Policy/ Certificate: An insurance policy is an insurance document evidencing insurance has been taken out on the goods shipped, and it gives full details of the insurance coverage. An insurance certificate certifies that the shipment has been insured under a given open policy and is to cover loss of or damage to the cargo while in transit. Prepared by Insurer or Insurance Agent or Insurance Broker.
8. Product Testing Certificate: A certificate to certify the products are conformed to a certain international/national technical standard, such as product quality, safety and specifications etc. Prepared by Accredited Laboratories.
9. Health Certificate: Document issued by the competent country when agricultural or food products are being exported, to certify that they comply with the relevant legislation in the exporter's country and were in good condition at time of inspection, prior to shipment and fit for human consumption. Prepared by Exporter / Inspection Authority.
10. Consular Invoice: A document required by some foreign countries, showing shipment information such as consignor, consignee, and value description, etc. Certified by a consular official of the importing country stationed in the foreign country, it is used by the country's customs officials to verify the value, quantity and nature of the shipment. Prepared by Exporter.

B. Transport Documents

1. Shipping Order S/O: A document to give details of the cargo and the shipper's requirements. It is the basic document for preparing other transport documents such as bill of lading, air way bill etc. Prepared by Shipper / Transport Companies.
2. Dock Receipt D/R or Mate's Receipt: A receipt to confirm the receipt of cargo on quay/warehouse pending shipment. The dock receipt is used as documentation to prepare a bill of lading. It has no legal role regarding processing financial settlement. Prepared by Shipping Company.
3. Bills of Lading ( B/L): An evidence of contract between the shipper of the goods and the carrier. The customer usually needs the original as proof of ownership to take possession of the goods. There are two types: a STRAIGHT bill of lading is non-negotiable and a negotiable or shipper's ORDER bill of lading (also a title document) which can be bought, sold or traded while goods are in transit and is used for many types of financing transactions. Prepared by Shipping Company.
4. House Bill of Lading: A bill of lading issued by a forwarder and, in many cases, not a title document. Shippers choosing to use a house bill of lading, should clarify with the bank whether it is acceptable for letter of credit purpose before the credit is opened. Advantages include less packing, lower insurance premiums, quicker transit, less risk of damage and lower rates than cargo as an individual parcel / consignment. Prepared by Forwarder.
5. Sea Way Bill: A receipt for cargo which incorporates the contract of carriage between the shipper and the carrier but is non-negotiable and is therefore not a title document. Prepared by Shipping Company.
6. Air Way bill (AWB): A kind of waybill used for the carriage of goods by air. This serves as a receipt of goods for delivery and states the condition of carriage but is not a title document or transferable/negotiable instrument. Prepared by Airline.
7. House Air Way Bill (HAWB): An air consignment note issued by an air freight agent to provide the cargo description and records. Again, it is not a title document. Prepared by Forwarding Agent.
8. Shipping Guarantee: Usually a pre-printed form provided by a shipping company or the bank, given by an importer's bank to the shipping company to replace the original transport document. The consignee may then in advance take delivery of goods against a shipping guarantee without producing the original bill of lading. The consignee and the importer bank will be responsible for any loss or charges occurred to the shipping company if fault is found in the collection. It is usually used with full margin or trust receipt to protect the bank's control to the goods. Prepared by Importer's Bank / Shipping Company / Consignee.

C. Financial Documents

1. Documentary Credit D/C: A bank instrument began (issuing or opening bank), at the request of the buyer, evidencing the bank's undertaking to the seller to pay a certain sum of money provided that specific requirements set out in the D/C are satisfied. Prepared by The Issuing Bank upon an application made by the Importer.
2. Collection Instruction: An instruction given by an exporter to its banker, which empowers the bank to collect the payment subject to the contract terms on behalf of the exporter. Prepared by Exporter.
3. Bill of Exchange (B/E) or Draft: An unconditional written order, in which the importer addressed to and required by the exporter to pay on demand or at a future date a certain amount of money to the order of a person or bearer. Prepared by Exporter.
4. Trust Receipt (T/R): A document to release a merchandise by a bank to a buyer (the bank still retains title to the merchandise), the buyer, who obtains the goods for processing is obligated to maintain the goods distinct from the remainder of his/her assets and to hold them ready for repossession by the bank. Prepared by Importer.
5. Promissory Note: A financial instrument that is negotiable evidencing the obligations of the foreign buyer to pay to the bearer. Prepared by Importer.

D. Government Documents

1. Certificate of Origin (CO): A certificate to certify the place of manufacture, the nature/quantity/value of the goods. Prepared by Trade and Industry Department and five Chambers of Commerce.
2. Import / Export Declaration: A statement made to the Director of Customs at port of entry/exit, declaring full particulars of the shipment, eg. the nature and the destination/exporting country of the ship's cargo. Its primary use is for compiling trade statistics. Prepared by Exporter/ Importer.
3. Import / Export Licence: A document issued by a relevant government department authorising the imports and exports of certain controlled goods. Prepared by Trade and Industry Department, Customs & Excise Department, etc.
4. International Import Certificate (IIC): A statement issued by the government of country of destination, certifying the imported strategic goods will be disposed of in the designated country. In Hong Kong, it is issued only to meet an exporting country's requirement. Prepared by Trade and Industry Department.
5. Landing Certificate: A document issued by the government of country of destination, certifying a specific commodity has been arrived in the designated country. Prepared by Statistics Department.
6. Customs Invoice: A document specified by the customs authorities of the importing countries stating the selling price, costs for freight, insurance, packing and payment terms, etc, for the purpose of determining the customs value. Prepared by Exporter.

Cotton Fibre | Physical Properties and Chemical Properties of Cotton

Cotton is a cellulosic fibre. Cotton is used as a fibre because it has a large amorphous portion which makes the fabric comfortable. It is also soft when properly ginned and has a high absorbency power hence making it easy to use for dyeing. It is also said to have good strength and good drape ability.

Characteristics of Cotton

• Comfortable Soft hand
• Good absorbency
• Color retention
• Prints well
• Dry-cleanable
• Good strength
• Drapes well
• Easy to handle and sew

Physical Properties of Cotton

• Color: The color of cotton fibre could be white, creamy white, bluish white, yellowish white or grey.
• Tensile Strength: Cotton is moderately strong fibre; tenacity is 26.5-44.1 cN/tex and tensile strength 2800-8400 Kg/cm^2. The strength is greatly affected by moisture, the wet strength of cotton is 20%, which is higher than dry strength.
• Elongation at break: Cotton does not stress easily. It has an elongation break of 5-1%.
• Elastic Recovery: Cotton is inelastic and rigid fibre. at 2% extension it has an elastic recovery of 74% and at 5% extension the elastic recovery is 45%.
• Specific Gravity: Specific gravity is 1.54
• Moisture Regain: Standard moisture regain is 8.5%.
• Effect of heat: Cotton has an excellent resistant to degradation by heat. It begins to turn yellow after several hours at 120°C and decomposes marked by at 150°C. As a result of oxidation, cotton is severally damaged after few minutes at 240°C. Cotton burns in air.
• Effects of Age: Cotton shows a small loss of strenth when stored carefully. After 50 years of storage cotton may differ only slightly from the new fibres.
• Effect of Sun Light: There is gradual loss of strength when cotton is exposed to sun light and the fibre turn yellow. The degradation of cotton by oxidation is done when heat is promoted and encouraged. By sun light much of the damage is caused by UV-light and by the shorten weaves of visible light.

Chemical Properties of Cotton

• Effects of Acids: Cotton is attacked by hot dilute acids or cold concentrated acids which it disintegrates. It is not affected by cold weak acids.
• Effects of Alkalis: Cotton has an excellent resistance to alkali. It swells in caustic alkalis but does not damaged. It can be washed in soap solution without any problem.
• Effects of Organic Solvents: Cotton has high resistance to normal cleaning solvents. Cotton is dissolved by the copper complexes, such as cuprammonium hydroxide, cupriethylene diamine and concentrated 70% H2SO4.
• Effects of Insects: Cotton is attacked by moth-grubs or beetles.
• Effects of micro Organism: Cototn is attacked by fungi and bacteria. Mildew will feed on cotton fabric, rotting and weakling the materials. mildews and bacteria will flourish on cotton under hot and humid condition. They can be protected by impregnation with certain types of chemicals. Copper Nepthenate is one of the chemicals.

Scouring | Pretreatment Process in Wet Processing

Scouring is the pretreatment process of wet processing technology. Scouring is the process by which natural impurities (oil, wax, gum, fat etc) as well as added impurities (during fabrication process) are removed completely as possible. Especially hydrophobic character which is present in the fibre of the fabric is removed by this process.

Objectives of Scouring

• To remove impurities from the textile materials.
• To improve absorbency of textile materials without undergoing physical and chemical damage.
• To produce clean and hydrophilic effect.

Effect of Scouring

• Saponifiable oils and free fatty acids are converted into soaps.
• Pectose and pectin are changed into soluble salts of pectic acid.
• Proteins are hydrolysed into soluble degradation products.
• Mineral matters are dissolved an the water.
• Unsaponiafiable oils and waxes are emulsified by the soaps formed from saponification.
• Dust particles are removed and held in suspension.

Saponification:

The reaction by which the insoluble and water immiscible materials are converted into water soluble products is called saponification.

Motions of Loom

Weaving is the most basic process in which two different sets of yarns or threads are interlaced with each other to form a fabric or cloth. One of these sets is called warp which is the lengthwise yarn running from the back to the front of the loom. The other set of crosswise yarns are the filling which are called the weft or the woof.Therefore Weaving loom motions can be broadly catagorised as follows:

Primary Motions

Shedding:

The separation of warp thread by lifting and lowering of heald frames, according to pattern, to allow for weft insertion.

Picking:

The process of inserting the filling yarn through the shed while the shed is opening.

Beating-up:

The process of pushing the filling yarn into the already woven fabric at a point known as the fell and done by the reed.

Secondary Motions

Let-off motion:

This is the motion which delivers warp to the weaving area at the required rate and at a suitable constant tension by unwinding it from a flanged tube known as the weaver’s beam.

1. Positive let-off motion: A mechanism controlling the rotation of the beam on a weaving or other fabric forming machine where the beam is driven mechanically.
2. Negative let-off motion: A mechanism controlling the rotation of the beam on a weaving or other fabric forming machine where the beam is pulled round by warp against a braking force applied to beam.

Take Up motion:

This is the motion that withdraws fabric from the weaving area at a constant rate. It ensures that the required pick spacing is maintained, and then winds it onto the cloth roller.

1. Positive take up motion: It is the motion in which the take up roller is gear driven, a change wheel or variable-throw pawl and ratchet being provided to allow the required rate to be obtained, so determining the pick spacing.
2. Negative take up motion: It is the motion in which the take up roller is rotated by means of a weight or spring, this roller only rotates when the force applied by the weight or spring is greater than the warp lay tension in the fabric. The take up rate is controlled by the size of the force applied by the weight or spring and/or the warp tension.

Auxiliary Motions

To get high productivity and good quality of fabric, additional mechanisms, called auxiliary mechanisms, are added to a plain power loom.The auxiliary mechanisms are useful but not absolutely essential. That is why they are called the auxiliary mechanisms.

• Warp protector mechanism: The warp protector mechanism will stop the loom if the shuttle get strapped between the top and bottom layers of the shed. It thus prevents excessive damage to the warp threads, reed wires and shuttle.
• Weft stop motion: The object of the weft stop motion is to stop the loom when a weft thread breaks or gets exhausted. This motion helps to avoid cracks in a fabric.
• Temples: The function of the temples is to grip the cloth and hold it at the same width as the warp in the reed, before it is taken up.
• Brake: The brake stops the loom immediately whenever required. The weaver uses it to stop the loom to repair broken ends and picks.
• Warp stop motion: The object of the warp stop motion is to stop the loom immediately when a warp thread breaks during the weaving process.

Barre in Fabrics | Fabric Fault

In textile industry, one of the most common and perplexing quality control problems is barre (repetitive yarn direction streaks). The factors which can cause or contribute to barre are varied and diverse. Barre is defined as "unintentional, repetitive visual pattern of continuous bars or stripes usually parallel to the filling of woven fabric or to the courses of circular knit fabric."

Causes of Barre

Fibre properties:

• Fibre Micronaire variation
• Fibre color variation
• Improper mixing of cotton from different origin
• Improper mixing of cotton from different varieties
• Improper mixing of cotton grown in different seasons

Yarn properties:

• Yarn linear density variation
• Yarn twist variation
• Yarn hairiness variation
• Yarn package lot mixing
• Hard or soft winding of yarn package

knitting:

• Tight loops: This may take the form of a shaddow ( several courses involved) or a discreet line ( one course involved). It will normally show up as a dark or dense line or shaddow
• Slack loop: Similar to above, but it shows up as a sheer or light line.
• Improper stich length at a feed
• Improper tension at a feed
• Variation in fabric take-up from loose to tight
• Worn needles, which generaly produce length direction streaks
• Uneven cylinder height needles(wavy barre)

Weaving:

• Uneven warping tension
• Uneven take-up tension
• Uneven let-off motion
• Uneven tension on filling
• Scuffing or filling yarn on the beam
• Bent beam gudgeons

Parameters Influencing the Combing Operation

Combing is a process which is meant for upgrading the cotton raw material so that the following yarn properties will improve compared to the normal carded yarn. U% of yarn tenacity gms/tex trash in the yarn(or kitties in the yarn) Lustre and visual appearance. The main parameters influencing combing are:

RAW MATERIAL:

• Fibre type
• Fibre fineness (Micronaire)
• Fibre length
• Uniformity of fibre length (CV)
• Fibre stiffness
• Moisture content
• Foreign material associated with the fibres

MATERIAL PREPARATION:

• Parallelization of the fibres in the sheet (batt)
• Batt thickness
• Batt evenness
• Orientation of the hooks

FACTORS ASSOCIATED WITH THE MACHINE:

• Condition of the machine
• Condition of the combs
• Speeds
• Operational performance of the combs
• Type of sliver forming element (diagonal shift of the piecing)
• Accuracy of the settings
• Drafting arrangement
• Movement of the elements
• Weight of the elements
• Type of withdrawal of the combed web (either straight forward or oblique)

MACHINE SETTINGS:

• Feed distance
• Type of feed
• Detachment setting
• Point density of the combs
• Circular comb clothing (angles of teeth, density of teeth, etc)
• Depth of penetration of the top comb
• Piecing
• Draft
• Drafting arrangement settings

AMBIENT CONDITIONS:

• Room temperature
• Relative humidity in the room

Combing Process

Sequence of Operation in A Comber

For getting high quality of yarn, one extra process is introduced which is called combing process. Combing is an operation in which dirt and short fibers are removed from sliver lap by following ways:

1. Feeding, lap is fed by feed roller
2. Fed lap gripped by the nipper
3. Gripped lap is combed by circular comb
4. Detaching roller grips the combed lap and moves forward
5. While the detaching roller delivers the material, top comb comes into action to further clean the lap
6. While going back, nipper opens and receives a new bit of lap

The raw material delivered by the carding machine can not be fed directly to the comber. Lap preparation is a must.

A good lap fed to the comber should have

• Highest degree of evenness so that lap is gripped uniformly by the nipper
• A good parallel disposition of fibres so that long fibres will not be lost in the noil
• Trailing hooks from carding should be fed as leading hooks to reduce long fibre loss in the noil
• Degree of parallelisation of lap fed to the combers should be optimum

Types of feeds in Comber

Forward feed (concurrent feed):

Feed of the sheet into the nippers occurs while the nippers move towards the detaching roller.

Backward feed (counter-feed):

Feed of the sheet occurs during return of the nippers. Higher Noil % always improves the imperfections in the final yarn. But the strength and other quality parameters improve upto certain noil %, further increase in noil results in quality deterioration. In backward feed, the cylinder comb combs through the fibres more often than in forward feed. Therefore, the elimination of impurities and neps is always good. However the difference is usually undetectable in modern high performance combers of the latest generation.

The Feed Length has a direct influence on production rate, noil %, and the quality of combing. High feed length increases the production rate but cause deterioration in quality. Higher the quality requirement, feed length should be lower. To some extent , the feed length may be decided by the length of the fibre also.

Detaching length is the distance between the bite of the nippers and the nip of the detaching rollers. This distance directly affects the noil %. More the detaching distance, higher the elimination of noil.

Needles of the top comb have a flattened cross section and are used with a point density in the range of 22 to 32 needles per centimeter. More the needles, more the noil%. The Depth of Penetration of top comb also affects the Noil %. If the comb depth is increased by 0.5mm, approximately 2% increase in noil will occur. When the depth is increased , the main improvement in quality is seen in Neps. Over deep penetration of top comb disturbs fibre movement during piecing which will deteriorate the quality.

Production Calculation of the comber

• N- Nips per min
• S- feed in mm/nip
• G- lap weight in g/m
• K- Noil percentage
• A- tension draft between lap and feed roller(from 1.05 to 1.1)
• E- efficiency

Production = (E * N * S * G * (100-K) * 60 * 8) / (1000 * 1000 * A *100)

Combing

The straighten and parallelizing of fibres and removal of short fibres and impurities by using a comb or combs assisted by brushes and roller. Combing is the process which is used to upgrade the raw material. It influences the following yarn quality:

• Yarn evenness
• Strength
• Cleanness
• Smoothness
• Visual appearance

In addition to the above, combed cotton needs less twist than a carded yarn.

Objectives of Combing

• Elimination of short fibres
• Elimination of remaining impurities
• Elimination of neps

The basic operation of the comber is to improve the mean length or staple length by removing the short fibres. Since fineness of short fibres (noil) is low, the overall micronaire of the sliver after combing is high.

Because of combing, fibre parallelisation increases. Please note that this is a side effect which is not an advantage always. The high degree of parallelisation might reduce inter-fibre adhesion in the sliver to such an extent that the fibres slide apart while pulled out of the can. This may lead to sliver breaks or false draft.

Combers Noel

The wastage which is removed from the comber m/c during processing is known as comber’s noel. It is expressed as percentage. It is mainly of short fibers and naps. Noel is used for lower count as raw material.

Combing for finer/better yarn

• For finer count, high draft is required but draft irregularity for presence of short fibre. After combing short fibre free product (sliver/roving) is ready for higher draft.
• Longer fibres are finer than shorter fibre. After combing higher count is possible to keep minimum no. of fibre in yarn dia.

Contribution of combing to yarn quality

• Improve the spinning value of fibre.
• Better twist distribution improve the strength of yarn.
• Improve uniformity, smoothness and luster of yarn.
• Reduce yarn hairiness and imperfection.
• Improve Yarn regularity and strength.