Manufacture Process

The principal raw materials for fertilizer production are air (to provide nitrogen), natural gas (to provide hydrogen for ammonia synthesis) phosphate rock, potash and sulfur (for suifuric acid production and subsequent use in phosphate fertilizer production). Fossil fuels are also used for power generation in the mining and processing of raw materials. As with other industries, mining and treatment of each raw material may raise environmental problems.

Use of natural gas for fertilizer production contributes around 2 per cent of global carbon dioxide emissions. The increased availability of nitrogen from fertilizers, manures and leguminous crops further adds to greenhouse emissions by the formation of increased amounts of nitrous oxide. These sources together may contribute as much as 3 to 5 per cent of the long term greenhouse effect. However, use of fertilizers stimulates plant growth and photosynthesis, removing carbon dioxide from the air. The overall effect of fertilizers on greenhouse gas emissions is therefore likely to be a positive one. Further, should soil organic matter concentrations increase due to fertilizer use, more carbon becomes 'locked away' in the soil.

Mining of phosphates and potash may damage the landscape. Phosphate rock is usually open-mined, generating large amounts of waste overburden. large scale restoration of the landscape is required. Some phosphate rock contains minor amounts of radioactive elements (e.g. uranium) necessitating special storage for mining waste. Leaching of waste may cause water pollution. Potassium extraction may also lead to water pollution when brines are produced as a by-product. Large stockpiles of common salt (sodium chloride) are often generated during the processing of potash ores.

Extraction of sulfur from industrial smoke stack gases, e.g. metal processing plants and fossil fuel power stations, may in fact minimise environmental impact by utilising sulfur dioxide, which may otherwise be emitted to the atmosphere, possibly contributing to acid rain.

Some emissions may occur during the manufacturing processes. Nitrogen oxides, ammonia, fluorides and sulfur dioxide, along with fertilizer dust, may be emitted. Losses however are small, less than 1 per cent of the nutrients handled.

Type of Fertilizers

The nutrients of most concern are nitrogen and phosphorus given their widespread use.

Nitrogen Fertilizers:

Excessive or inappropriately applied nitrogen fertilizers can lead to emissions of ammonia (by volatilisation) and nitrous oxides (by denitrification). The latter may contribute to greenhouse effects. The dominant source of atmospheric ammonia is from farm animals and manures, with fertilizer use contributing only an estimated 10 per cent of atmospheric ammonia in Western Europe. While ammonia concentrations in the air are too low (of the order of micrograms per cubic metre) to affect air quality, they may contribute to acid rain and soil acidification in these densely settled and intensely cropped regions.

Nitrogen fertilizers readily convert to nitrate in the soil. The nitrogen in soil organic matter and organic fertilizers becomes available more slowly. Nitrate from all sources may be readily leached if not used by crops or pasture. Leaching is particularly likely in sandy soils following heavy rainfall. Leached nitrate may contaminate underground water. This is of concern if the water is to be used for human or livestock consumption, as high concentrations of nitrate may affect health. Nitrate combines with haemoglobin, interfering with oxygen transport in the blood, particularly in young children. World standards are set for nitrate levels in drinking water (10 mg/L NO3- N or 45mg/L N03-). Nitrate contamination of groundwater is not of concern in most parts of Australia as little use is made of shallow underground water for drinking, and Australia's agriculture is far less intensive than in Europe and North America. Leaching of nitrate can be minimised by good fertilizer management (recommended rates, soil and plant tissue analysis, application when maximum uptake occurs, split-application etc.).

The use of fertilizers, particularly nitrogen fertilizers can accelerate the natural process of soil acidification. The initial effect fertilizers have on soil pH in the immediate vicinity of the granules is usually of little consequence. While some fertilizers are acidic e.g. MAP and others basic e.g. DAP, their effects are confined to the point of application. Due to the relatively small volume of soil affected compared to total soil volume, there is little effect on sail pH. Some fertilizers e.g. anhydrous ammonia and urea may initially raise the soil pH at the site of application but in the long term acidify the soils. This occurs when ammonium is converted to nitrate.

Superphosphate is popularly held to be responsible for soil acidification. It does not directly cause soil pH to fall, but since it does promote legume growth and nitrogen fixation it will, like most nitrogen fertilizers, have an indirect effect on soil pH. Any practice which increases plant growth such as proper fertilization will lead to the gradual acidification of the soil by two main processes. They are the formation and loss of nitrate through the soil, and removal of nutrients in the form of farm produce.

Removal of plant and animal produce removes alkaline cations such as calcium and magnesium, along with some acidic elements. There is an overall acidifying effect on the soil. Any accumulation of organic matter in the soil increases the amount of nitrogen stored in the soil. Organic nitrogen is then converted to ammonium and subsequently to nitrate by nitrification. In the process, hydrogen ions are formed i.e. acid is produced. Much of this increased nitrogen comes from fixation by legumes, and from fertilizer application. Acid produced in the nitrification process can be used if the nitrate is taken up by plants or soil organisms, but if the nitrate is leached beyond the root zone, acidification occurs. The effect then of intensive agricultural systems is one of soil acidification.

The effects of soil acidification include reduced availability of the trace element molybdenum, development of aluminium and manganese toxicity and modulation failure in legumes. Soil analysis is used in diagnosing soil acidity problems. Lime may be required where acidity is a problem. Lime (obtained from naturally occurring calcium carbonate) neutralises soil acidity and acts as a soil conditioner. Application rates depend upon the soil type, degree of acidity and crop being grown and may vary from 1-10 tonnes per hectare. The use of acid tolerant plant species is another management strategy.

Phosphorus fertilizers:

Excess amounts of phosphorus have been associated with the eutrophication of lakes and waterways, and with algal blooms. Nitrogen may also contribute; the level of nitrogen influencing the algal type. When nitrogen levels are low, blue-green algae which fix their own nitrogen are favoured.

Blue-green algae (more correctly named Cyanobacteria) are naturally present in small numbers in healthy waterways. During periods of prolonged dry weather, water stagnates, evaporation is high and nutrient levels become concentrated. These conditions of still waters, strong sunlight and high nutrient levels (particularly phosphorus) lead to rapid multiplication of the algae, and consequent algal blooms. The blue-green algae release toxins which cause sickness in humans and livestock. The bloom is fed by phosphorus in a mixture of soil run-off, sewage, manure from farm animals and wildlife and decaying material which enters the waterways, plus recycling of nutrients from within the waterway.

Given that phosphorus is relatively immobile in soils, leaching of fertilizer phosphorus is unlikely to cause build-up in waterways. This has happened, however, on deep sands in the south-west of Western Australia. Phosphorus present in surface water run-off may originate from soil erosion or freshly top-dressed fertilizer. Erosion of fertile top-soil, where fertilizer nutrients accumulate is another source of nutrient input to waterways. Soil conservation and cultural practices which reduce soil erosion can significantly reduce phosphorus inputs into waterways.

While the use of fertilizers can contribute to nutrient overload and consequent algal blooms, the extent of the contribution has not been measured and defined. It is one of many sources, and possibly a minor one. Minimising potential impact of fertilizers involves good fertilizer practices (appropriate application rates, timing and application techniques) to minimise potential losses. Management practices (improved erosion and run-off control and buffer vegetation around waterways) also contribute to minimising environmental effects.

Phosphorus fertilizers contain various impurities from the phosphate rock and acid used in manufacture. Cadmium (Cd) is of most concern. levels of cadmium in fertilizer will vary with the phosphate rock source. As there is currently no commercial means of removing cadmium during fertilizer manufacture, the only control is to use fertilizer made from low cadmium phosphate rock, especially in areas of intensive use, e.g. vegetables.

Use of phosphorus fertilizers may lead to a build-up of the heavy metal cadmium in soils. Cadmium is normally present in soils at levels of 0.1-1.0 mg/kg soil. Phosphorus fertilizers contain higher levels of cadmium as an impurity, so prolonged use over time increases soil cadmium levels. Cadmium input to soils also occurs from the atmosphere e.g. near industrial centres, and in sewage sludge.

The use of phosphorus fertilizers may increase cadmium concentrations in farm produce, which in some situations may exceed maximum permissible levels. This is most noticeable with certain crops e.g. potatoes and leafy vegetables (lettuce and spinach) and in the offal (kidneys and liver) of animals. Use of fertilizers with a low cadmium content i.e. less than 100 mg of cadmium per kg of phosphorus (P) and preferably less than 50 mg of cadmium per kg P is recommended, especially in vegetable production.

Reference:
http://www.incitecfertilizers.com.au/environmental_facts.cfm

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Cement Process

- QUARY
Basic Elements

For its raw materials, cement uses minerals containing the four essential elements for its creation: calcium, silicon, aluminum and iron.

Raw Materials

Most plants rely on a nearby quarry for limestone. The most common combination of ingredients is limestone (for calcium) coupled with much smaller quantities of clay and sand (as sources of silica, aluminum and iron). Other raw materials, such as mill scale, shale, bauxite and fly ash are brought in from outside source when necessary.

Crusher

Rock blasted from the quarry face is transported to the primary crusher, where chair sized rocks are broken into pieces the size of baseballs. A secondary crusher reduces them to the size of gravel. Some plants now crush materials in a single stage

- PROPORTIONING, BLENDING & GRINDING

The raw materials are now analyzed in the plant laboratory, blended in the proper proportion, and then ground even finer. Plant grind the raw materials into powder against a rotating table. After grinding, the material is now ready for the kiln or preheater, depending on plant type.

- PREHEATER TOWER

The preheater tower supports a series of vertical cyclone chambers through which the raw materials pass on their way to the kiln. To save energy, modern cement plants preheat the materials before they enter the kiln. Rising more than 200 feet, hot exit gases from the kiln heat the raw materials as they swirl throught the cyclones

- KILN

Raw materials now enter the huge rotatign furnae called kiln. It's the heart of the cement making process - a horizontally sloped steel cylinder, lined with firebrick, turning from about one to three revolutions per minute. The kiln is the world's largest piece of moving industrial equipment.

From the preheater, the raw material enters the kiln at the upper end. It slides and tumbles down the kiln through progressively hotter zones toward the flame. At the lower end of the kiln, fuels such as powdered coal and natural gas feed a flame that reaches 3400'F (1870 'C) - one-third of the temperature of the sun's surface. Here in the hottest part of the kiln, the raw materials reach about 2700 F (1480C) and become partially molten.

This intense heat triggers chemical and physical changes. Expressed at its simplest, the series of chemical reactions converts the calcium and silicon oxides into calcium silicates, cement's primary constituent. At the lower end of the kiln, the raw materials emerge as a new substance; red hot particles called clinker.

- CLINKER COOLER & FINISH GRINDING

The clinker tumbles onto a grate cooled by forced air. Once cooled the clinker is ready to be ground into the gray powder known as portland cement.

To save energy, heat recovered from this cooling process is recirculated back to the kiln and preheater tower.

The clinker is ground in a ball mill - a horizontal steel tube filled with steel balls. As the tube rotates, the steel balls tumble and crush the clinker into a super-fine powder. It can now be considered portland cement. The cement is so fine it will easily pass through a sieve that is fine enough to hold water. A small amount of gypsum is added during final grinding to control the set.

- BAGGING & SHIPPING

From the grinding mills, the cement is conveyed to silos where it awaits shipment. Most cement is shipped in bulk by trucks, rail or barge. A small percentage of the cement is bagged for customes who need only small amounts or for special uses such as mortar. Most cement is shipped to ready-mixed concrete producers. There, it's combined with water, sand and gravel to make concrete delivered in the familiar truks with revolving drums. Cement is also used for a wide array of precast concrete products.



Raw Materials

The main raw materials used in the cement manufacturing process are limestone, sand, shale, clay, and iron ore. The main material, limestone, is usually mined on site while the other minor materials may be mined either on site or in nearby quarries. Another source of raw materials is industrial by-products. The use of by-product materials to replace natural raw materials is a key element in achieving sustainable development.


Raw Material Preparation


Mining of limestone requires the use of drilling and blasting techniques. The blasting techniques use the latest technology to insure vibration, dust, and noise emissions are kept at a minimum. Blasting produces materials in a wide range of sizes from approximately 1.5 meters in diameter to small particles less than a few millimeters in diameter.


Material is loaded at the blasting face into trucks for transportation to the crushing plant. Through a series of crushers and screens, the limestone is reduced to a size less than 100 mm and stored until required.


Depending on size, the minor materials (sand, shale, clay, and iron ore) may or may not be crushed before being stored in separate areas until required.


Raw Grinding

In the wet process, each raw material is proportioned to meet a desired chemical composition and fed to a rotating ball mill with water. The raw materials are ground to a size where the majority of the materials are less than 75 microns. Materials exiting the mill are called "slurry" and have flowability characteristics. This slurry is pumped to blending tanks and homogenized to insure the chemical composition of the slurry is correct. Following the homogenization process, the slurry is stored in tanks until required.


In the dry process, each raw material is proportioned to meet a desired chemical composition and fed to either a rotating ball mill or vertical roller mill. The raw materials are dried with waste process gases and ground to a size where the majority of the materials are less than 75 microns. The dry materials exiting either type of mill are called "kiln feed". The kiln feed is pneumatically blended to insure the chemical composition of the kiln feed is well homogenized and then stored in silos until required.


Pyroprocessing

Whether the process is wet or dry, the same chemical reactions take place. Basic chemical reactions are: evaporating all moisture, calcining the limestone to produce free calcium oxide, and reacting the calcium oxide with the minor materials (sand, shale, clay, and iron). This results in a final black, nodular product known as "clinker" which has the desired hydraulic properties.


In the wet process, the slurry is fed to a rotary kiln, which can be from 3.0 m to 5.0 m in diameter and from 120.0 m to 165.0 m in length. The rotary kiln is made of steel and lined with special refractory materials to protect it from the high process temperatures. Process temperatures can reach as high as 1450oC during the clinker making process.


In the dry process, kiln feed is fed to a preheater tower, which can be as high as 150.0 meters. Material from the preheater tower is discharged to a rotary kiln with can have the same diameter as a wet process kiln but the length is much shorter at approximately 45.0 m. The preheater tower and rotary kiln are made of steel and lined with special refractory materials to protect it from the high process temperatures.


Regardless of the process, the rotary kiln is fired with an intense flame, produced by burning coal, coke, oil, gas or waste fuels. Preheater towers can be equipped with firing as well.


The rotary kiln discharges the red-hot clinker under the intense flame into a clinker cooler. The clinker cooler recovers heat from the clinker and returns the heat to the pyroprocessing system thus reducing fuel consumption and improving energy efficiency. Clinker leaving the clinker cooler is at a temperature conducive to being handled on standard conveying equipment.


Finish Grinding and Distribution

The black, nodular clinker is stored on site in silos or clinker domes until needed for cement production. Clinker, gypsum, and other process additions are ground together in ball mills to form the final cement products. Fineness of the final products, amount of gypsum added, and the amount of process additions added are all varied to develop a desired performance in each of the final cement products.


Each cement product is stored in an individual bulk silo until needed by the customer. Bulk cement can be distributed in bulk by truck, rail, or water depending on the customer's needs. Cement can also be packaged with or without color addition and distributed by truck or rail.

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The first completely automated loom was made by Jacques Vaucanson in 1745. It was used for silk but didn't develop further. Edmund Cartwright built and patented a power loom in 1785, and it was this that was adopted by the nascent cotton indudstry. Powered looms were shuttle-operated for two hundred years. In the early part of the 20th century the faster and more efficient shuttleless rapier looms and air looms came into use. Modern industrial looms can weave at speeds 2000 Weft insertions per minute. Today, advances in technology have produced a variety of looms designed to maximize production for specific types of material. The most common of these are air-jet looms and water-jet looms. Computer-driven looms are now also available to individual (non-industrial) weavers.

Knitting looms
Knitting looms (also known as Amish looms or knitting boards) were recently popularized in crafting circles by the Knifty Knitter system. Knitting looms are a descendant of the frame loom. Grooved pegs are spaced along a central frame. These pegs are wrapped with yarn in various ways, then the knitter uses an angled hook to pull the wrapped yarn over the top of the peg, resulting in a fabric with stitches similar to a needle knitted item.


Bow Looms
A type of loom used for thin strips of beading. A bow loom consists of a bendable branch of cedar, willow or other easily bendable types of wood. 10-11 holes are then made along the length of two smaller pieces of wood. Thread is looped through the holes and attached to the long bendable piece. Once the bow is threaded, the thread is then used for beading. This method was traditionally used by the Native Americans.


Shuttle looms
The major components of the loom are the warp beam, heddles, harnesses, shuttle, reed and takeup roll. In the loom, yarn processing includes shedding, picking, battening and taking-up operations.

Shedding. Shedding is the raising of the warp yarns to form a shed through which the filling yarn, carried by the shuttle, can be inserted. The shed is the vertical space between the raised and unraised warp yarns. On the modern loom, simple and intricate shedding operations are performed automatically by the heddle frame, also known as a harness. This is a rectangular frame to which a series of wires, called heddles, are attached. The yarns are passed through the eye holes of the heddles, which hang vertically from the harnesses. The weave pattern determines which harness controls which warp yarns, and the number of harnesses used depends on the complexity of the weave.

Picking. As the harnesses raise the heddles, which raise the warp yarns, the shed is created. The filling yarn in inserted through the shed by a small carrier device called a shuttle. The shuttle is normally pointed at each end to allow passage through the shed. In a traditional shuttle loom, the filling yarn is wound onto a quill, which in turn is mounted in the shuttle. The filling yarn emerges through a hole in the shuttle as it moves across the loom. A single crossing of the shuttle from one side of the loom to the other is known as a pick. As the shuttle moves back and forth across the shed, it weaves an edge, or selvage, on each side of the fabric to prevent the fabric from raveling.

Battening. As the shuttle moves across the loom laying down the fill yarn, it also passes through openings in another frame called a reed (which resembles a comb). With each picking operation, the reed presses or battens each filling yarn against the portion of the fabric that has already been formed. Conventional shuttle looms can operate at speeds of about 150 to 160 picks per minute.

With each weaving operation, the newly constructed fabric must be wound on a cloth beam. This process is called taking up. At the same time, the warp yarns must be let off or released from the warp beams.

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Sugarcane is a perennial herb belonging to the grass family. Native to tropical and subtropical regions of the world, this tropical grass is 10-24-feet tall. bears long, pointed leaves, and has several stalks. The segmented stalks have a bud at each joint and as the plant matures, small flowers appear.

PLANTING

Sugarcane cuttings are planted in fields by workers or mechanical planters. In order for the cane to grow, the seeds must be planted in well-drained soil. Typical cane soil is made of a mixture of silt, sand, clay particles and organic matter. Canes are spaced at least 4-feet apart and lined in rows and covered with soil. Fertilizers are applied from the time of planting up until the beginning of the ripening period. Cane fields are also routinely weeded to provide for optimum growth of the cane. Depending on the region where the crop is planted, cane seasons last from 8-22 months. In the United States, sugarcane is grown in Florida, Hawaii, Louisiana and Texas.


COLLECTING THE HARVEST

Mature canes are gathered by a combination of manual and mechanical methods. Canes are cut at ground level, its leaves are removed and the top is trimmed off by cutting off the last mature joint. Cane is then placed into large piles and picked up, tied, and transported to a sugar factory.


CLEANSING AND GRINDING

Stalks are thoroughly washed and cut when reaching the sugar mill. After the cleaning process, a machine led by a series of rotating knives, shreds the cane into pieces. This is known as "grinding." During grinding, hot water is sprayed on to the sugarcane to dissolve any remaining hard sugar. The smaller pieces of cane are then spread out on a conveyer belt.

JUICING

The shredded pieces of sugarcane travel on the conveyer belt through a series of heavy-duty rollers, which extract juice from the pulp. The pulp that remains or "bagasse" is dried and used as fuel. The raw juice moves on through the mill to be clarified.


CLARIFYING

Carbon dioxide and the milk of a lime are added to the liquid sugar mixture and it is heated to the boiling point, as the process of clarifying begins. As the carbon dioxide travels through the liquid it forms calcium carbonate, which attracts non-sugar debris (fats, gums, and wax) from the juice, and pulls them away from the sugar juice. The juice is then pushed through a series of filters to remove any remaining impurities.


EVAPORATION

The clear juice which results from the clarifying process is put under a vacuum, where the juice boils at a low temperature and begins to evaporate. It is heated until it forms into a thick, brown syrup.


CRYSTALLIZATION

By evaporating what little water is left in the sugar syrup, crystallization takes place. Inside a sterilized vacuum pan, pulverized sugar is fed into the pan as the liquid evaporates, causing the formation of crystals. The remaining mixture is a thick mass of large crystals, which is sent to a centrifuge to spin and dry the crystals. The dried product is raw sugar, still inedible.


REFINERY

Raw sugar is transported to a Cane Sugar Refinery for the removal molasses, minerals and other non-sugars, which still contaminate the sugar. This is known as the purification process. Raw sugar is mixed with a solution of sugar and water to loosen the molasses from the outside of the raw sugar crystals, producing a thick matter known as "magma." Large machines then spin the magma, which separate the molasses from the crystals. Crystals are promptly washed, dissolved and filtered to remove impurities. The golden syrup which is produced is then sent through filters to remove the color and water. What's left is a concentrated, clear syrup, which is again fed into a vacuum pan.


SEPARATION AND PACKAGING

Once the final evaporation and drying process is done, screens separate the different sized sugar crystals. Large and small crystals are packaged and shipped, labeled as white, refined, sugar.


SUGAR FACTS

REFINED white sugar is 99.9-percent sucrose.


WHITE sugar is pure sucrose, containing no preservatives or additives.

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INTRODUCTION:
As Carding machine design improved in 1950's and 60's, it became apparent that card clothing was a limiting factor
Much time and effort was spent in the development of metallic card clothing.
• There are two rules of carding

1. The fibre must enter the carding machine, be efficiently carded and taken from it in as little time as possible
2. The fibre must be under control from entry to exit

• Control of fibres in a carding machine is the responsibility of the card clothing
• Following are the five types of clothings used in a Carding machine

1. Cylinder wire
2. Doffer wire
3. Flat tops
4. Licker-in wire
5. Stationary flats

CYLINDER WIRE:
The main parameters of CYLINDER Card clothing
1. Tooth depth
2. Carding angle
3. Rib width
4. Wire height
5. Tooth pitch
6. Tooth point dimensions

• TOOTH DEPTH:
1. Shallowness of tooth depth reduces fibre loading and holds the fibre on the cylinder in the ideal position under the carding action of the tops. The space a fibre needs within the cylinder wire depends upon its Micronaire/denier value and staple length could have to be reduced.
2. The recent cylinder wires have a profile called "NO SPACE FOR LOADING PROFILE"(NSL). With this new profile, the tooth depth is shallower than the standard one and the overall wire height is reduced to 2mm , which eliminates the free blade in the wire. This free blade is responsible for fibre loading. Once the fibre lodges between the free blade of two adjacent teeth it is difficult to remove it. In order to eliminate the free blade, the wire is made with a larger rib width
• FRONT ANGLE:
1. Front angle not only affects the carding action but controls the lift of the fibre under the action of centrifugal force. The higher the cylinder speed , the lower the angle for a given fibre. Different fibres M have different co-efficients of friction values which also determine the front angle of the wire.
2. If the front angle is more, then it is insufficient to overcome the centrifugal lift of the fibre created by cylinder speed. Therefore the fibre control is lost, this will result in increasing flat waste and more neps in the sliver.
3. If the front angle is less, then it will hold the fibres and create excessive recyling within the carding machine with resulting overcarding and therefore increased fibre damage and nep generation.
4. Lack of parallelisation, fibre damage, nep generation, more flat waste etc. etc., are all consequences of the wrong choice of front angle.
• TOOTH PITCH:
1. Each fibre has a linear density determined by its diameter to length ratio. Fine fibres and long fibres necessitates more control during the carding process. This control is obtained by selecting the tooth pitch which gives the correct contact ratio of the number of teeth to fibre length.
2. Exceptionally short fibres too require more control, in this case , it is not because of the stiffness but because it is more difficult to parallelise the fibres with an open tooth pitch giving a low contact ratio.
• RIB THICKNESS:
1. The rib thickness of the cylinder wire controls the carding "front" and thus the carding power. Generally the finer the fibre, the finer the rib width. The number of points across the carding machine is determined by the carding machine's design, production rate and the fibre dimensions. General trend is towards finer rib thicknesses, especially for high and very low production machines.
2. Rib thickness should be selected properly, if there are too many wire points across the machine for a given cylinder speed, production rate and fibre fineness, "BLOCKAGE" takes place with disastrous results from the point of view of carding quality. In such cases, either the cylinder speed has to be increased or most likely the production rate has to be reduced to improve the sliver quality
• POINT POPULATION:
The population of a wire is the product of the rib thickness and tooth pitch per unit area. The general rule higher populations for higher production rates, but it is not true always. It depends upon other factors like production rate, fineness, frictional properties etc.
• TOOTH POINT:
The tooth point is important from a fibre penetration point of view. It also affects the maintenance and consistency of performance. Most of the recent cylinder wires have the smallest land or cut-to-point. Sharp points penetrate the fibre more easily and thus reduce friction, which in turn reduces wear on the wire and extends wire life.
• BLADE THICKNESS:
Blade thickness affects the fibre penetration. The blade thickness is limited by practical considerations, but the finer the blade the better the penetration of fibres. Wires with thin blade thickness penetrate the more easily and thus reduce friction, which in turn reduces wear on the wire and extends wire life.
• BACK ANGLE:
A lower back angle reduces fibre loading, but a higher value of back angle assists fibre penetration. Between the two extremes is an angle which facilitates both the reduction in loading and assists fibre penetration and at the same time gives the tooth sufficient strength to do the job for which it was designed.
• HARDNESS OF WIRE:
The cylinder wire needs to be hard at the tip of the tooth where the carding action takes place. The hardness is graded from the hard tip to the soft rib. High carbon alloy steel is used to manufacture a cylinder wire and it is flame hardened. Rib should not be hardened, otherwise, it will lead to mounting problems.
• The design or type of clothing, selected for the fibre to be carded is important, but it is fair to
state that within reason, an incorrect design of clothing in perfect condition can give acceptable carding quality whereas a correct clothing design in poor condition will never give acceptable carding quality. There is no doubt that the condition of the clothings is the most important single factor affecting quality at high rates of production. Wire condition and selection of wire are considered to be the two most important factors which influence the performance of modern high production carding machines.
• The condition of the clothing may be defined as the collective ability of the individual teeth of the clothing to hold on to the fibre against the opposing carding force exerted by other teeth acting in the carding direction. For a given design of clothing the condition of the teeth determines the maximum acceptable production rate that can be achieved at the card.
• The speed of the main cylinder of card provides the dynamic force required to work on separating the fibres fed to the card but it is the ability of the carding teeth on the cylinder to carry the fibre forward against the opposing force offered by the teeth of the tops which determines the performance of the card. Increasing cylinder speed increases the dynamic forces acting upon the carding teeth and thus the condition of teeth becomes more important with increased speed. If the condition and design of the cylinder wire is poor, the teeth will not be able to hold onto the fibre through the carding zone, thus allowing some of the freed fibre to roll itself into nep.

DOFFER WIRE:
1. The doffer is a collector and it needs to have a sharp tooth to pickup the condensed mass of fibres circulating on the cylinder. It also requires sufficient space between the teeth to be efficient in fibre transfer from the cylinder, consistent in the transfer rate and capable of holding the fibre under control until the doffer's stripping motion takes control.

2. A standard doffer wire has an overall height of approx. 4.0 mm to facilitate the deeper tooth which must have sufficient capacity to collect all the fibre being transferred from the cylinder to meet production requirements. Heavier webs require a deeper doffer tooth with additional collecting capacity to hanndle the increased fibre mass.

3. The doffer wire's front angle plays a very important part in releasing the fibre from the cylinder wire's influence. A smaller angle has a better chance of enabling the doffer wire's teeth to find their way under the fibres and to secure the fibre's release from the cylinder with greater efficiency. A 60 degree front angle for Doffer has been found to give the optimum performance under normal carding conditions. Too small an angle results in cloudy web and uneven sliver whilst too large an angle results in fibre recirculation and nep generation.

4. Having collected the fibre, it is important for the doffer to retain it until it is stripped in a controlled manner by the doffer stripping motion. The tooth depth, tooth pitch and rib width combine to create the space available for fibre retention within the doffer wire. Thus they directly influence the collecting capacity. If the space is insufficient, fibre will fill the space and any surplus fibre will be rejected. When the surplus fibre is left to recirculate on the cylinder, cylinder loading can take place. Unacceptable nep levels and fibre damage will also result. In severe cases pilling of the fibre will take place.

5. The point of the doffer wire normally has a small land which helps to strengthn the tooth. The extremely small land of around 0.05 mm ensures that the doffer wire height is consistent, has no adverse effect on fibre penetration and is considred essential for efficient fibre transfer from the cylinder. The land has micropscopic striations which are created during manufacturing or grinding. The striations help to collect the fibres from the cylinder and keep them under control during the doffing process.

6. It has been found that a cut-to-point doffer wire penetrates the fibre better than does the landed point wire but is less likely to keep the fibre under control during the doffing process. Sometimes a cut-to-point doffer wire is accompanied by striations along one side of the tooth for this reason. Until recently 0.9mm rib thickness is standardised for doffer wire, regardless of production and fibre characteristics. This rib thickness has been found to give optimum results. However doffer wires with a 0.8mm rib thickness have been introduced for applications involving finer fibres.

7. In general 300 to 400 PPSI(points per square inch) has been found to perform extremely well under most conditions. Doffer wire point population is limited by the wire angle and tooth geometry. Higher population for doffer does not help in improving the fibre transfer.

8. As the production rate rises, the doffer speed also increases. The doffer is also influenced by the centrifugal force, as is the cylinder. But cylinder wire front angle can become closer to counter the effect of centrifugal force, to close the front angle on a doffer wire would reduce its collecting capacity and result in a lowering of the production rate. The solution is to use the wire with striations, which will hold the fibre until the doffer is stripped.

9. The hardness of the doffer wire is a degree lower than that of the cylinder but sufficiently hard to withstand the forces generated in doffing and the resultant wear of the wire. The reason for this slightly lower hardness requirement is the longer and slimmer tooth form of the differ wire.

10. The fibres which are not able to enter the wire will lay on top, i.e. completely out of control. There fore instead of being carded by the tops the fibres will be rolled. Similarly a fibre buried too deep within the cylinder wire will load the cylinder with fibre, weaken the carding action and limit the quantity of new fibres the cylinder can accept. Therefore, the production rate would have to be reduced.

LICKER-IN WIRE:
• Licker-in with its comparatively small surface area and small number of carding teeth, suffers the hardest wear of all in opening the tangled mass of material fed to it.
• Successful action of the Licker-in depends upon a penetrating sharp point rather than a sharp leading edge as with the cylinder wire. Therefore the licker-in wire cannot be successfully restored to optimum performance by grinding.
• The most satisfactory system to adopt to ensure consistent performance is to replace the licker-in wire at regular intervals before sufficient wear has taken place to affect carding quality.
• The angles most widely used are 5 degrees negative or 10 degrees.
• There is no evidence to suggest recommendation of a tooth pitch outside the range of 3 to 6 points per inch.
• It is better to use Licker-in roller without groove. Interlocking wires are used for such type
of licker-ins. This avoids producing the eight precise grooves and to maintain them throughout its life. Interlocking wire is almost unbreakable and thus no threat to the cylinder, tops and doffer in the event of foreigh bodies entering the machine.

FLAT TOPS:
1. The flat tops are an equal and opposite carding force to the cylinder wire and it should be sharp, well maintained and of the correct design.

2. The selection of flexible tops is very much related to the choice of cylinder wire, which in turn is related to the cylinder speed, production rate and fibre characteristics, as previously stated.

3. The modern top is of the semi-rigid type, having flexible foundation and sectoral wire. The points are well backed-off and side-ground to give the necessary degree of fineness. The strength of the top from a carding point of view is in the foundation and is affected by the number of plies and the type of material used. The position of the bend in the wire is determined by stress factors, at around 2:1 ratio along the length of the wire protrusion.

4. The modern top is made from hardened and tempered wire to increase wear resistance , thus improving the life of the flat top.

• Life of the cylinder wire depends upon
1. Material being processed
2. production rate
3. cylinder speed
4. settings

• Wear is the natural and unavoidable side effect of the work done by the vital leading edge of the metallic wire tooth in coping with the opposing forces needed to obtain the carding action which separates fibre from fibre. When the leading edge becomes rounded due to wear, there is a loss of carding power because the point condition has deteriorated to an extent where the leading edge can no longer hold on to the fibre against the carding resistance of the flats. This ultimately leads to fibres becoming rolled into nep with consequent degradation of carding quality. Therefore it is important to recognise that, due to the inevitable wear which takes place during carding, metallic wire must be reground at regular intervals with the object of correctly resharpening the leading edge of each tooth.

• GRINDING:
1. GRINDING A CUT-TO-POINT CYLINDER WIRE:

1. Wire points of cylinder have become finer and the tip is cut-to-point.Because of this new profile, it has beccome necessary to recommend a little or no grinding of the cylinder wire following mounting. TSG grinding machine of GRAF(wire manufacturer) can be used to sharpen these modern wires. TSG grinding is a safe method of grinding.

2. Before grinding , the wire should be inspected with a protable microscope to ascertain the wear. Based on this and the wire point land width, no of traverse for TSG grinding should be decided. If the width of the wire point tip is bigger and the wear out is more, the number of traverse during grinding should be more.
For a new wire, 3 or 4 traverses may be enough. But it may require 10 to 30 traverses for the last grinding before changing the wire, depending upon the maintenance of the wire.

2. GRINDING A NORMAL CYLINDER AND DOFFER WIRE:
1. The first grinding of the metallic wire on the cylinder and doffer is the final and most important step leading up to providing the card with a cylinder in the best possible condition for carding well at maximum production rate. Grinding the lands of the teeth provides the leading edge of each tooth with the final sharpness required for maximum carding power.

2. The first grinding should be allowed to continue until at least eighty percent(for cylinder) and 100% (for doffer) of the lands of the teeth have been ground sufficient to sharpen the leading edge of the tooth.

3. To ascertain this stage of grinding, it is necessary to stop the cylinder regularly and use a simple microscope to examine the teeth at random across and round the cylinder.

4. If the wire on the cylinder is of good quality and has been correctly mounted, the initial grinding period should be completed with in 20 min.

5. It is essential to avoid over-working the wire before taking corrective action. The regrinding cycle must be determined accurately for the conditions applying in the individual mill, by using the microscope.
6. If regrinding is done properly, there are several advantages
1. carding quality will remain consistent
2. There is no risk of overworking the wire
3. Time required for regrinding is very short
4. The exact condition of the clothing is known
5. The working life of the wire is likely to be longer because the points are never allowed to become worn
6-beyond recovery
7. To obtain acceptable grinding conditions at the low grinding speed, the grindstone must always be SHARP, CLEAN and CONCENTRIC. If the grinding stone is gradually allowed to become dull and glazed through constant use, the limited cutting action available will eventually disappear, resulting in burning and hooking of the carding teeth.
8. Due to the low peripheral speed of the grindstone which has to be used, it is most important that the speed of the wire to be ground is as high as is practicable to provide a high relative speed between the grindstone surface and the carding teeth. If wire speed is low, the individual carding tooth spends too long a time in passing under the grindstone, thereby increasing the risk of hooking and burning the tooth, which is usually irreparable.
9. With cylinder grinding, speed is no problem because the normal operating speed of the cylinder is more than sufficient. The speed of the doffer for grinding is more commonly a problem and this should be driven at a minimum speed of 250 m/min, to avoid damage when grinding the wire, the design which is particularly
susceptible to hooking due to the long fine, low angled teeth needed on the doffer.
10. The directions of rotation for metallic wire grinding are normally arranged so that the back edge of the tooth is first to pass under the grindstone. This is termed grinding "back of point"

3. GRINDING FLAT TOPS:
1. Flat tops provide the opposing carding force against the cylinder wire and hence can equally effect carding quality. It is essential to ensure that the tops are kept in good condition to maintain maximum carding power with the cylinder. Again, the only reliable approach is to examine the tops with the microscope and decide whether grinding is required or not.

2. For cards fitted with regrindable tops, it is good practice to regrind the flats at regular intervals thus ensuring that the conditions of the two principal carding surfaces are always complementary one to other.

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The ring spinning will continue to be the most widely used form of spinning machine in the near future, because it exhibits significant advantages in comparison with the new spinning processes.
• Following are the advantages of ring spinning frame

• It is universaly applicable, i.e.any material can be spun to any required count
• It delivers a material with optimum charactersticss, especially with regard to structure and strength.
• it is simple and easy to master
• the know-how is well established and accessible for everyone

• Functions of ringframe

• to draft the roving until the reqired fineness is achieved
• to impart strength to the fibre, by inserting twist
• to wind up the twisted strand (yarn) in a form suitable for storage, transportaion and further processing.

DRAFTING

• Drafting arrangement is the most important part of the machine. It influences mainly evenness and strength
The following points are therefore very important

• drafting type
• design of drafting system
• drafting settings
• selection of drafting elements like cots, aprong, traveller etc
• choice of appropriate draft
• service and maintenance

• Drafting arrangement influence the economics of the machine - directly by affecting the end break rate and indirectly by the maximum draft possible.
• If higher drafts can be used with a drafting arrangement, then coarser roving can be used as a feeding material. This results in higher production rate at the roving frame and thus reducing the number roving machines required, space, personnel and so on.
• In fact increase in draft affects the yarn quality beyond certain limit. Within the limit some studies show that increase in draft improves yarn quality. The following draft limits have been established for practical operation:

• carded cotton- upto 35
• carded blends - upto 40
• combed cotton and blends(medium counts) - upto 40
• combed cotton and blends(fine counts) - upto 45
• synthetic fibres - upto 50

• The break draft must be adapted to the total draft in each case since the main draft should not exceed 25 to 30. It should be noted that higher the break draft, more critical is the break draft setting
• The front top roller is set slightly forward by a distance of 2 to 4mm relative to the front bottom roller, while the middle top roller is arranged a short distance of 2mm behind the middle bottom roller.
• Overhang of the front top roller gives smooth running of the top rollers and shortens the spinning triangle. This has a correspondigly favourable influence on the end break rate.
• Rubber cots with hardness less than 60 degrees shore are normally unsuitable because they can not recover from the deformation caused by the pressure on the top roller while running.
• Soft rubbercots for toprollers have a greater area of contact, enclose the fibre strand more completely and therefore provide better guidance for the fibres.However softer cots wear out significantly faster and tend to form more laps.
• Normally harder rubbercots are used for back top rollers, because the roving which enters the back roller is compact , little twisted and it does not require any additional guidance for better fibre control.
• In the front top roller, only few fibres remain in the strand and these exhibit a tendency to slide apart . Additional fibre guidance is therefore necessary.Therefore rubbercots with hardness levels of the order 80 degrees to 85 degrees shore are mostly used at the back roller and 63 degrees and 65 degrees at the front roller.
• If coarse yarns and synthetic yarns are being spun, harder rubbercots are used at the front roller because of increased wear and in the case of synthetic yarns to reduce lapups.
• Three kinds of top roller weighting(loading) are presently in use

• spring loading
• pneumatic loading
• magnetic weighting

• With pneumatic loading system, the total pressure applied to all top rolers is obtained by simple adjustment of the pressure in the hose using pressure reducing valve. Moreover the rubbercots will not get deformed if the machine is stopped for a longer duration, because the pressure on top rollers can be released to the minimum level.
• The fibre strand in the main drafting field consists of only a few remaining fibres. There is hardly any friction field and fibre guidance provided by the rollers alone is inadequate. Special fibre guiding devices are therefore needed to carry out a satisfactory drafting operation. Double apron drafting arrangements with longer bottom aprons is the most widely used guding system in all the modern ringframes.
• In doube apron drafting system two revolving aprons driven by the middle rollers form a fibre guiding assembly. In order to be able to guide the fibres, the upper apron must be pressed with controlled force against the lower apron. For this purpose, a controlled spacing (exit opening), precisely adapted to the fibre volume is needed between the two aprons at the delivery. This spacing is set by "spacer" or "distance clips". Long bottom aprons have the advantage in comparison wiht short ones, that they can be easily replaced in the event of damage and there is less danger of choking with fluff.
• Spindles and their drive have a great influence on power consumption and noise level in the machine The running characteristics of a spindle, especially imbalance and eccentricity relative to the ring flange, also affect yarn quality and of course the number of end breakage. Almost all yarn parameters are affected by poorly running spindles. Hence it should be ensured that the centering of the spindles relative to the rings is as accurate as possible. Since the ring and spindle form independent units and are able to shift relative to each other in operation, these two parts must be re-centered from time to time. Previously, this was done by shifting the spindle relative to the ring, but now it is usually carried out by adjusting the ring.
• In comparison with Tangential belt drive, the 4-spindle drive has the advantages of lower noise level and energy consumption, and tapes are easier to replace.
• Lappet guide performs the same sequence of movements as the ringrail, but with a shorter stroke, this movement of the guide ensures that differences in the balloon height caused by changes in the ring rail positions do not become too large. This helps to control the yarn tension variation with in control, so that ends down rate and yarn charactersitics are under control.
• Spindles used today are relatively long. The spacing between the ring and the thread guide is correspondingly long, thus giving a high balloon. This has two negative influence

• A high balloon results in large bobbin diameter leading to space problems
• Larger the balloon diameter , higher the air drag on the yarn.This inturn causes increased deformation of the balloon curve out of hte plane intersecting the spindle axis.This deformation can lead to balloon stability, there is increase danger of collapse.

Both these disadvantages result in higher yarn tension, thereby higher endbreaks.In order to avoid this, balloon control rings are used. It divides the balloon into two smaller sub-balloons. Inspite of its large overall height, the double-balloon created in this way is thoroughly stable even at relatively low yarn tension.
• Balloon control rings therefore help to run the mahcine with long spindles(longer lift) and at high spindle speed, but with lower yarn tension. Since the yarn rubs against the control ring, it may cause rougheningof the yarn.
• Most ends down arise from breaks in the spinning triangle, because very high forces are exerted on a strand consisting of fibres which have not yet been fully bound together in the spinning triangle.

RING and TRAVELLER COMBINATION:

• The following factors should be considered
• materials of the ring traveller
• surface charecteristics
• the forms of both elements
• wear resistance
• smoothness of running
• running-in conditions
• fibre lubrication

• For the rings two dimensions are of primariy importance. 1.internal diameter 2. flange width.
• Antiwedge rings exhibit an enlarged flange inner side and is markedly flattened on it upper surface. This type of profile permitted to use travellers with a lower centre of gravity and precisely adapted bow(elliptical travellers), which in turn helped to run the machine with higher spindle speeds. Antiwedge rings and elliptical travellers belong together and can be used in combination.
• Low crown profle has the following advantage. Low crown ring has a flattened surface top
and this gives space for the passage of the yarn so that the curvature of the traveller can also be reduced and the centre of gravity is lowered.In comparison with antiwedge ring, the low crown ring has the advantage that the space provided for passage of the yarn is somewhat larger and that all current traveller shapes can be applied, with the exception of the elliptical traveller. The low crown ring is the most widely used ring form now.
• The ring should be tough and hard on its exterior. The running surface must have high and even hardeness in the range 800-850 vikcers. The traveller hardness should be lower (650-700 vickers), so that wear occurs mainly on the traveller, which is cheaper and easier to replace. Surface smoothness should be high, but not too high, because lubricating film can not build up if it too smooth.

• A good ring in operation should have the following features:

• best quality raw material
• good, but not too high, surface smoothness
• an even surface
• exact roundness
• good, even surface hardness, higher than that of the traveller
• should have been run in as per ring manufacturers requirement
• long operating life
• correct relationship between ring and bobbin tube diameters
• perfectly horizontal position
• it should be exactly centered relative to the spindle

• In reality, the traveller moves on a lubricating film which builds up itself and which consists primarily of cellulose and wax. This material arises from material abraded from the fibres.If fibre particles are caught between the ring and traveller, then at high traveller speeds and with correspondingly high centrifugal forces, the particles are partially ground to a paste of small, colourless, transparent and extremely thin platelets. The platelets are continually being replaced during working. The traveller smoothes these out to form a continuous running surface.The position, form and structure of lubricating film depends on

• yarn fineness
• yarn structure
• fibre raw material
• traveller mass
• traveller speed
• heigh of traveller bow

Modern ring and traveller combination with good fibre lubrication enable traveller speeds upto 40m/sec.
• Traveller imparts twist to the yarn. Traveller and spindle together help to wind the yarn on the bobbin. Length wound up on the bobbin corresponds to the difference in peripheral speeds of the spindle and traveller. The difference in speed should correspond to length delivered at the front rollers. Since traveller does not have a drive on its own but is dragged along behing by the spidle.
• High contact pressure (upto 35 N/square mm)is generated between the ring and the traveller during winding, mainly due to centrifugal force. This pressure leads to generation of heat. Low mass of the traveller does not permit dissipation of the generated heat in the short time available. As a result the operating speed of the traveller is limited.
• When the spindle speed is increased, the friction work between ring and traveller (hence the build up) increases as the 3rd power of the spindle rpm. Consequently if the spindle speed is too high, the traveler sustains thermal damage and fails. This speed restriction is felt particularly when spinning cotton yarns of relatively high strength.
• If the traveller speed is raised beyond normal levels , the thermal stress limit of the traveller is exceeded, a drastic change in the wear behaviour of the ring and traveller ensues. Owing to the strongly increased adhesion forces between ring and traveller, welding takes place between the two. These seizures inflict massive damage not only to the traveller but to the ring as well.Due to this unstable behaviour of the ring and traveller system the wear is atleast an order of magnitude higher than during the stable phase. The traveller temperature reaches 400 to 500 degrees celcius and the danger of the traveller annealing and failing is very great.
• The spinning tension is proportional

• to the friction coefficient between ring and traveller
• to the traveller mass
• to the square of hte traveler speed

and inversely proportional

• to the ring diameter
• and the angle between the connecting line from the traveller-spindle axis to the piece of yarn between the traveller and cop.

• The yarn strength is affected only little by the spinning tension. On the other hand the elongation diminishes with increasing tension, for every tensile load of hte fibres lessens the residual elongation in the fibres and hence in the yarn. Increasing tension leads also to poorer Uster regularity and IPI values.
• If the spinning tension is more, the spinning triangle becomes smaller . As the spinning triangle gets smaller, there is less hairiness.

SHAPE OF THE TRAVELLER:

• The traveller must be shaped to match exactly with the ring in the contact zone, so that a single
contact surface, with the maximum surface area is created between ring and traveller. The bow of the traveller should be as flat as possible, in order to keep the centre of gravity low and thereby improve smoothness of running. However the flat bow must still leave adequate space for passage of the yarn. If the yarn clearance opening is too small, rubbing of the yarn on the ring leads to roughening of the yarn, a high level of fibre loss as fly, deterioration of yarn quality and formation of melt spots in spinning of synthetic fibre yarns.

WIRE PROFILE OF THE TRAVELLER:

• Wire profile influences both the behaviour of the traveller and certain yarn characteristics, they are

• contact surface of the ring
• smooth running
• thermal transfer
• yarn clearance opening
• roughening effect
• hairiness

MATERIAL OF THE TRAVELLER

• The traveller should

• generate as little heat as possible
• quickly distribute the generated heat from the area where it develops over the whole volume of the traveller
• transfer this heat rapidly to the ring and the air
• be elastic, so that the traveller will not break as it is pushed on to the ring
• exhibit high wear resistance
• be less hard than the ring, because the traveller must wear out in use in preference to the ring

• In view of the above said requirements, traveller manufacturers have made efforts to improve the running properties by surface treatment. "Braecker" has developed a new process in which certain finishing components diffuse into the traveller surface and are fixed in place there. The resulting layer reduces temperature rise and increases wear resistance.
• Traveller mass determines the magnitude of frictional forces between the traveller and the ring, and these in turn determine the winding and balloon tension. Mass of the traveller depends upon

• yarn count
• yarn strength
• spindle speed
• material being spun

If traveller weight is too low, the bobbin becomes too soft and the cop content will be low. If it is
unduly high, yarn tension will go up and will result in end breaks. If a choice is available between two traveler weights, then the heavier is normally selected, since it will give greater cop weight, smoother running of the traveller and better transfer of heat out of traveller.
• When the yarn runs through the traveller, some fibres are liberated. Most of these fibres float away as dust in to the atmosphere, but some remain caught on the traveller and they can accumulate and form a tuft. This will increase the mass of traveller and will result in end break because of higher yarn tension. To avoid this accumulation , traveller clearers are fixed close to the ring, so that the accumulation is prevented. They should be set as close as possible to the traveller, but without affecting its movement. Exact setting is very important.
• Specific shape of the cop is achieved by placing the layers of yarn in a conical arrangement. In the winding of a layer, the ring rail is moved slowly but with increasing speed in the upward direction and quickly but with decreasing speed downwards. This gives a ratio between the length of yarn in the main (up) and cross(down) windings about 2:1.
• The total length of a complete layer (main and cross windings together) should not be greater
than 5m (preferably 4 m) to facilitate unwinding. The traverse stroke of the ring rail is ideal when it is about 15 to 18% greater than the ring diameter.
• End break suction system has a variety of functions.
• It removes fibres delivered by the drafting arrangement after an end break and thus prevents mulitple end breaks on neighbouring spindles.
• It enables better environmental control, since a large part of the return air-flow of the aircondition system is led past the drafting system, especially the region of the spinning triangle.
• In modern installations, approx. 40 to 50 % of the return air-flow passes back into the duct system of the airconditioning plant via the suction tubes of pneumafil suction system.
• A relatively high vacuum must be generated to ensure suction of waste fibres
o for cotton - around 800 pascals
o for synthetic - around 1200 pascals
• A significant pressure difference arises between the fan and the last spindle. This pressure difference will be greater , the longer the machine and greater the volume of air to be transported. The air flow rate is normally between 5 and 10 cubic meter/ hour.
• Remember that the power needed to generate an air-flow of 10 cubic meter/ hour , is about 4.5 times the power needed for an air-flow of 6 cubic meter/ hour, because of the significantly higher vacuum level developed at the fan.

SPINNING GEOMETRY:

• From Roving bobbin to cop, the fibre strand passes through drafting arrangement, thread guide, balloon control rings and traveller. These parts are arranged at various angles and distances relative to each other. The distances and angles together are referred to as the spinning geometry,has a significant influence on the spinning opeartion and the resulting yarn. They are

• yarn tension
• number of end breaks
• yarn irregularity
• binding-in of the fibres
• yarn hairiness
• generation of fly etc.
• Spinning Triangle:

Twist in a yarn is generated at the traveller and travel against the direction of yarn movement to the front roller. Twist must run back as close as possible to the nip of the rollers, but it never penetrates completely to the nip because, after leaving the rollers, the fibres first have to be diverted inwards and wrapped around each other. There is always a triangular bundle of fibres without twist at the exit of the rollers, this is called as SPINNING TRIANGLE. Most of the end breaks originate at this point. The length of the spinning triangle depends upon the spinning geometry and upon the twist level in the yarn.
• The top roller is always shifted 3 to 6 mm forward compared to bottom roller. This is called top roller overhang.This gives smoother running and smaller spinning triangle. The overhang must not be made too large, as the distance from the opening of the aprons to the roller nip line becomes too long resulting in poorer fibre control and increased yarn irregularity.
• Continuous variation of the operating conditions arises during winding of a cop.The result is that the tensile force exerted on yarn must be much higher during winding on the bare tube than during winding on the full cop, because of the difference in the angle of attack of the yarn on the traveller. When the ring rail is at the upper end of its stroke, in spinning onto the tube, the yarn tension is substantially higher than when the ring rail is at its lowermost position. This can be observed easily in the balloon on any ring spinning machine.
• The tube and ring diameters must have a minimum ratio, between approx. 1:2 and 1:2.2, in order to ensure that the yarn tension oscillations do not become too great.
• Yarn tension in the balloon is the tension which finally penetrates almost to the spinning triangle and which is responsible for the greater part of the thread breaks. It is reduced to a very small degree by the deviation of the yarn at the thread guide. An equilibrium of forces must be obtained between the yarn tension and balloon tension.

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Combing is the process which is used to upgrade the raw material. It influences the following yarn quality

1. yarn evenness


2. strength


3. cleanness


4. smoothness


5. visual appearance
   

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

TASK OF THE COMBER:
To proudce an improvement in yarn quality, the comber must perform the following operation.

1. elimination of short fibres


2. elimination of remaining impurities


3. 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.

SEQUENCE OF OPERATION IN A COMBER

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 rawmaterial 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

1. highest degree of evenness so that lap is gripped uniformly by the nipper


2. a good parallel disposition of fibres so that long fibres will not be lost in the noil


3. 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. If fibres are over parallelised lap licking will be a major problem. Because of fibre to fibre adhesion, mutual separation of layers within the sheet is very poor.Moreover the retaining power of the sheet can be strongly reduced that it is no longer able to hold back the neps as it usually does. Some of these neps also pass thro the top comb. Neppiness of the web is increased.

Retaining power of the fibres results in self cleaning of the lap during combing operation. A thick sheet always exerts a greater retaining power than a thin one.To certain extent, the bite of the nipper is more effective with a higher sheet volume.On the negative side , a thick sheet always applies a strong load to the comb and this can lead to uncontrolled combing.A compromise should be struck between quality and productivity.

If the sheet is more even across the width, clamping effect at the bite of the nipper will be better.
Evenness of the lap is therefore of considerable significance. The most effective method of obtaining a high degree of evenness of the sheet is through more number of doublings in the web form. (as it is done in RIBBON LAP)

Fibres must be presented to the comber so that leading hooks predominate in the feedstock. This influences not only the opening out of the hooks themselves, but also the cleanliness of the web.If the sheet is fed to the comber in the wrong direction, the number of neps rises markedly.

Both quantity and form of fibre hooks depend mainly upon the stiffness of the fibres. This rises to the second or third power with fine fibres. Fine and long fibres will always exhibit more and longer hooks than short and coarse fibres. Accordingly, the role of fibre hooks in the spinning process becomes more significant as fibres become finer.

There are two types of feeds in COMBER

1. Forward feed (concurrent feed):Feed of the sheet into the nippers occurs while the nippers move towards the detaching roller


2. 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 qality parameters improve upto certain noil %, further increase in noil results in quality detrioration.

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 hte nippers and the nip of the detaching rollers. This distance direectly 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.

Since the web from detaching roller is intermittent because of the intermittent functions like feeding, combing and detaching, to have a continuous web from the comber,fibre fringes are laid on the top of each other in the same way as roofting tiles. This process is called Piecing. This is a distinct source of fault in the operation of Rectinlinear Combing. The sliver produced in this way exhibits a periodic variation.

As large a lap as possible with adapted lap weight which is as high and as uniform as possible
must be positioned in front of the comber. The better the comber lap is prepared, the heavier the lap weight can be set on the comber and the less the resultant noil waste with the same degree of cleanliness of the yarn.

The higher degree of combing out are used in order to permit final spinning of ultra-fine yarns or to increase the strength of a yarn. Reducing the lint content improves the medium staple. However, not all cottons meet these requirements. Low degree of combing out , on the other hand, frequently serve to improve purity. When the card sliver is pulled through the needle bars, these separate off foreign bodies, large neps and torn fibres. Light combing out has also been introduced to a greater extent owing to the impairments in cotton purity influenced by mechanical harvesting. Even when combing with minimum noil percentages, there is a noticeable improvement in fibre parallelsim in the sliver. Even the smoothness and shine of the yarn are
improved. It must thus be anticipated that this method will become more and more popular in the future.

Production of the comber is dependent upon the following

1. N- Nips per min


2. S- feed in mm/nip


3. G- lap weight in g/m


4. K- Noil percentage


5. A- tension draft between lap and feed roller(from 1.05 to 1.1)


6. E- efficiency

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

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TASKS OF DRAWFRAME

1. Through doubling the slivers are made even


2. doubling results in homogenization(blending)


3. through draft fibres get parallelised


4. hooks created in the card are straightened


5. through the suction ,intensive dust removal is achieved


6. autoleveller maintains absolute sliver fineness

Quality of the drawframe sliver determines the yarn quality.

Drawing is the final process of quality improvement in the spinning mill

Drafting is the process of elongating a strand of fibres, with the intention of orienting the fibres in the direction of the strand and reducing its linear density.In a roller drafting system, the strand is passedthrogh a series of sets of rollers, each successive set rotating at a surface velocity greater than that of the previous set.

During drafting, the fibres must be moved relative to each other as uniformly as possible by overcoming the the cohesive friction. Uniformity implies in this context that all fibres are controllably rearranged with a shift relative to each other equal to the degree of draft.

In drawframe, the rollers are so rotated that their peripheral speed in the throughflow direction increases fromroller pair to roller pair, then the drawing part of the fibres, i.e.the draft, takes place. Draft is defined as the ratio of the delivered length to the feed length or the ratio of the corresponding peripheral speeds.

Drawing apart of the fibres is effected by fibres being carried along with the roller surfaces. For this to occur, the fibres must move with the peripheral speed of hte rollers. This transfer of the roller speed tothe fibres represents one of the problems of drafting operation. The transfer can be effected only byfriction, but the fibre strand is fairly thick and only its outer layers have contact with the rollers, and furthermore various, non-constant forces act on the fibres.

Roller drafting adds irregularities in the strand.Lamb states that,though an irregularity causing mechanism does existin drafting, drafting also actually reduced the strand irregularities by breaking down the fibre groups.Drafting is accompanied by doubling on the drawframe, this offsets the added irregularity.

Variance(sliver out) = Variance(sliver in) + Variance(added by m/c)

In Statistics , Variance is the square of standard deviation

Two passages of drawing with eight ends creeled each time would produce a single sliver consisting of 64 ribbons of fibre in close contact with each other.In the ultimate product, each ribbon may be only a few fibres thick,and thus the materials of the input slivers are dispersed by the drawing process. The term doubling is also used to describe this aspect of drawing

Drafting arrangement is the heart of the drawframe. The drafting arrangement should be

• simple


• stable design with smooth running of rollers


• able to run at higher speeds and produce high quality product


• flexible i.e suitable to process different materials , fibre lenths and sliver hanks


• able to have good fibre control


• easy to adjust

Roller drafting causes irregularities in the drafted strand since there is incomplete control of the motionof each individual fibre or fibre group.The uniformity of the drafted strand is determined by

• draft ratio


• roller settings


• material characteristics


• pressure exerted by the top roller


• hardness of top roller


• fluting of the bottom rollers


• distribution of draft between the various drafting stages

drafting is affected by the following rawmaterial factors

• no of fibres in the cross section


• fibre fineness


• degree of parellelisation of the fibres


• compactness of the fibre strand


• fibre cohesion which depends on

1. surface structure


2. crimp


3. lubrication


4. compression of the strand


5. fibre length


6. twist in the fibre


7. distribution of fibre length

3-over-3 roller drafting arrangements with pressure bar is widely used in the modern drawframesBigger front rollers are stable and operated at lower speeds of revolution, this necessitated pressure bararrangement for better control of fibres. Some drawframes are with 4-over-3 drafting arrangement, butstrictly speaking it behaves like a 3-over-3 drafting system except for the fact that fourth roller helpsto guide the sliver directly into the delivery trumpet.


DRAFTING WAVE:
Floating fibres are subject to two sets of forces acting in opposite directions. The more number of fibreswhich are moving slowly because of the contact with the back rollers restrain the floating fibres from accelerating. The long fibres in contact with the front rollers tend to accelerate the floating fibres to the higher speed.As the floating fibres move away from the back roller, the restraining force by back roller held fibres reduces,and the front roller influence increases. At some balance point, a fibre accelerates suddenly from low to high speed.This balance point is compounded by the laws of friction, static friction being higher than dynamic friction.When onefloating fibre accelerates, the neighbouring shor fibres suddenly feel one more element tending to accelrate them and one fewer trying to restrain them. Thus there may be an avalanche effect which results in drafting wave.

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Carding is the processing of brushing raw or washed fibers to prepare them as textiles. A large variety of fibers can be carded, anything from dog hair, to llama, to soy fiber (a fiber made from soy beans),[1] to polyester. Cotton and wool are probably the most common fibers to be carded. Not all fibers are carded; Flax and bast, for example, are retted then threshed.


Carding is used to take unordered fibers and prepare them for spinning by either the worsted or woollen process or to produce webs of fibre to go into nonwoven products depending on the mechanism at the output from the card. It can also be used to create blends of different fibers or different colors. The process of carding mixes up the different fibers, thus creating a homogeneous mix of the various types of fibers, at the same time as it orders them and gets rid of the tangles. Machine cards for carding wool also have rollers and systems designed to remove some vegetable contaminants from the wool.



INTRODUCTION
"Card is the heart of the spinning mill" and "Well carded is half spun" are two proverbs of the experts.These proverbs inform the immense significance of carding in the spinning process.High production in cardingto economise the process leads to reduction in yarn quality.Higher the production, the more sensitive becomesthe carding operation and the greater danger of a negative influence on quality.The technological changes thathas taken place in the process of carding is remarkable. Latest machines achieve the production rate of60 - 100 kgs / hr, which used to be 5 - 10 kgs / hr, upto 1970.

THE PURPOSE OF CARDING:

1. to open the flocks into individual fibres
2. cleaning or elimination of impurities
3. reduction of neps
4. elimination of dust
5. elimination of short fibres
6. fibre blending
7. fibre orientation or alignment
8. sliver formation
   

TECHNOLOGICAL POINTS IN CARDING
There are two types of feeding to the cards

1. feeding material in the form of scutcher lap
2. flock feed system (flocks are transported pneumatically)
   

lapfeeding

1. linear density of the lap is very good and it is easier to maintain(uniformity)
2. the whole installation is very flexible
3. deviations in card output will be nil, as laps can be rejected
4. autolevellers are not required, hence investment cost and maintenace cost is less
5. transportation of lap needs more manual efforts( more labour)
6. lap run out is an additional source of fault, as it should be replaced by a new lap
7. more good fibre loss during lap change
8. more load on the taker-in, as laps are heavily compressed

flock feeding

high performance in carding due to high degree of openness of feed web

labour requirement is less due to no lap transportaion and lap change in cards

flock feeding is the only solution for high prouduction cards

linear density of the web fed to the card is not as good as lap

installation is not felxible

autoleveller is a must, hence investment cost and maintenance cost is more

Type of flock feed(chute feed)

there are two basic concepts of flock feed

1. one piece chute without an opening device
2. two piece chute with an opening system

one piece chute is simple, economical and requires little maintenance
two piece chute is complex, expensive, but delivers a uniform batt.
One piece chut is a closed system, i.e.excess flock returns to the distrbutor, if too much material is present,neps can be increased
one piece chute is not flexible to run different mixings
layout restrictions are more with one piece chute

A feeding device is a must to feed the web to the Taker-in region and it should perform the following tasks

1. to clamp the batt securely throughout its width
2. to grip the fibres tightly without slippage during the action of taker-in
3. to present the fibres in such a manner that opening can be carried out gently

The divertor nose(sharp or round) and the length of the nose(guide surface) have a significant influence on quality and quantity of waste removed. Shart nose divertor avoids fibre slippage but the opening action is not gentle.If the length of the guide surface is too short, the fibres can escape the action of the taker-in. They are scraped off by the mote knives and are lost in the waste receiver.

Feed roller clothed with sawtooth is always better , because it gives good batt retention. Thus the opening effectof the taker-in is more as it is in combing

Rieter has devloped a "unidirectional feed system" where the two feed devices(feed roller and feed plateare oppositely arranged when compared with the conventional system. i.e. the cylinder is located below and the plate is pressed against the cylinder by spring force. Owing to the direction of feed roller, the fibre battruns downwards without diversion directly into the teeth of the taker-in(licker-in) which results in gentlefibre treatment. This helps to reduce faults in the yarn.

The purpose of the taker-in is to pluck finely opened flocks out of the feed batt, to lead them over the dirt eliminating parts like mote knives, combing segment and waste plates, and then to deliver the fibres to themain cylinder. In high production cards the rotational speed ranges from 700-1400

The treatment for opening and cleaning imparted by Taker-in is very intensive, but unfortunately not verygentle.Remember that around 60% of the fibres fed to the main cylinder is in the form of individual fibres.

The circumferential speed of Taker-in is around 13 to 15 m/sec and the draft is more than 1000.It clearlyshows that fibre gets deteriorated at this opening point. Only the degree of deterioration can be controlled by adjusting the following

1. the thickness of the batt
2. the degree of openness of the rawmaterial
3. the degree of orientation of the fibres
4. the aggressiveness of the clothing
5. the distance between the devices
6. the rotational velocity of the taker-in
   the material throughput

Latest TRUTZSCHLER cards work with three licker-ins compared to one liker-in.The first one is constructed as needle roll. This results in very gentle opening and an extremely long clothing life for this roll. The other tworollers are with finer clothing and higher speeds, which results in feeding more %of individual fibres and smallest tufts compared to single lickerin, to the main cylinder. This allows the maing cylinder to go high in speeds and reduce the load on cylinder and flat tops. There by higher productivity is achieved with goodquality. But the performance may vary for different materials and different waste levels.

between the taker-in and main cylinder , the clothings are in the doffing disposition. It exerts an influenceon the sliver quality and also on the improvement in fibres longitudinal orientation that occurs here. The effect depends on the draft between main cylinder and taker-in.The draft between main cylinder and taker-in should be slightly more than 2.0.

The opening effect is directly proportional to the number of wire points per fibre. At the Taker-in perhaps 0.3 points/ fibre and at the main cylinder 10-15 points /fibre.If a given quality of yarn is required,a corresponding degree of opening at the card is needed. To increase production in carding, the number of pointsper unit time must also be increased. this can be achieved by

• more points per unit area(finer clothing)
• higher roller and cylinder speeds
• more carding surface or carding position

speeds and wire population has reached the maximum, further increase will result in design and technological problems. Hence the best way is to add carding surface (stationary flats). Carding plates can be applied at

• under the liker-in
• between the licker-in and flats
• between flats and doffer

Taker-in does not deliver 100% individual fibres to main cylinder. It delivers around 70% as small flocksto main cylinder. If carding segments are not used, the load on cylinder and flats will be very high and cardingaction also suffers. If carding segemets are used, they ensure further opening, thinning out and primarily, spreading out and improved distribution of the flocks over the total surface area.carding segments bring the following advantages

1. improved dirt and dust elimination
2. improved disentanglement of neps
3. possibility of speed increase (production increase)
4. preservation of the clothing
5. possibility of using finer clothings on the flats and cylinder
6. better yarn quality
7. less damage to the clothing
8. cleaner clothing

In an indepth analysis, all operating elements of the card were therefore checked in regard to theirinfluence on carding intensity. It showed that the "CYLINDER-FLATS" area is by far the most effectiveregion of the card for.

1. opening of flocks to individual fibres
2. elimination of remaining impurities(trash particles)
3. elimination of short fibres( neps also removed with short fibres)
4. untangling the neps dust removal
5. high degree of longitudinal orientation of the fibres

The main work of the card, separation to individual fibres is done between the main cylinder and the flatsOnly by means of this fibre separation, it is possible to eliminate the fine dirt particles and dust.When a flat enters the working zone, it gets filled up very quickly. Once it gets filled, after few seconds, thereafter , hardly any further take-up of fibres occurs, only carding.Accordingly, if a fibre bundle doesnot find place at the first few flats, then it can be opened only with difficulty.It will be rolled betweenthe working surfaces and usually leads to nep formation

In princile, the flats can be moved forwards or backwards, i.e. in the same direction as or in opposition to the cylinder.In reverse movement, the flats come into operative relationship with the cylinderclothing on the doffer side. At this stage, the flats are in a clean condition. They then move towardsthe taker-in and fill up during this movement.Part of their receiving capacity is thus lost, but sufficientremains for elimination of dirt, since this step takes place where the material first enters the flats.At this position, above the taker-in, the cylinder carries the material to be cleaned into the flats. The latter take up the dirt but do not transport it through the whole machine as in the forward movement system.Instead , the dirt is immediately removed from the machine. Rieter studies show clearly that the greater partof the dirt is hurled into the first flats directly above the taker-in.

Kaufmann indicates that 75% of all neps can be disentagled, and of these about 60% are in fact disentagled. Of the remaining 40% disentaglable nep

• 30-33% pas on with the sliver
• 5-6% are removed with the flat strips
• 2-4%are eliminated with the waste

The intensity of nep separation depends on

• the sharpness of the clothing
• the space setting between the main cylinder and the flats
• tooth density of the clothing
• speed of the main cylinder
• speed of the flat tops
• direction of flats with reference to cylinder
• the profile of the cylinder wire

The arrangement of the clothing between the cylinder and the doffer is not meant for stripping action, It is for CARDING ACTION.This is the only way to obtain a condensing action and finally to form a web. It has bothadvantages and disadvantages.The advantage is that additional carding action is obtained here and it differssomewhat from processsing at the flats.A disadvantage is that leading hooks and trailing hooks are formedin the fibres , beause the fibres remain caught at one end of the main cylinder(leading hook) and some times onthe doffer clothing(trailing hook).

There are two rules of carding

1. The fibre must enter the carding machine, be efficiently carded and taken from it in as little time as possible.
2. The fibre must be under control from entry to exit

Carding effect is taking place between cylinder and doffer because, either the main cylinder clothing rakes through the fibres caught in the doffer clothing, or the doffer clothing rakes thro the fibres on the main cylinder.Neps can still be disentangled here, or non-separated fibre bundles can be opened a bit in this area and can be separated during the next passage through the flats

A disadvantage of web-formation at the card is the formation of hooks. According to an investigation bymorton and Yen in Manchester, it can be assumed that

• 50% of the fibres have trailing hooks
• 15% have leading hooks
• 15% have both ends hooked
• 20% without hooks

Leading hooks must be presented to the comber and trailing hooks to the ring spinning frame.There must be even number of passages between card and comber and odd number between the card and ringframe.

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Basic operations in the blowroom:

1. opening


2. cleaning


3. mixing or blending


4. microdust removal


5. uniform feed to the carding machine


6. Recycling the waste
   

Blow room installations consists of a sequence of different machines to carry out the above said operations.Moreover Since the tuft size of cotton becomes smaller and smaller, the required intensities of processing necessitates different machine configuration.


TECHNOLOGICAL POINTS IN BLOWROOM

• Opening in blowroom means opening into small flocks.Technological operation of opening means the volume of theflock is increased while the number of fibres remains constant. i.e. the specific density of the material is reduced


• The larger the dirt particle , the better they can be removed


• Since almost every blowroom machine can shatter particles, as far as possible a lot of impurities shouldbe eliminated at the start of the process.Opening should be followed immediately by cleaning, if possible in the same machine.


• The higher the degree of opening, the higher the degree of cleaning. A very high cleaning effect isalmost always purchased at the cost of a high fibre loss. Higher roller speeds give a better cleaning effectbut also more stress on the fibre.


• Cleaning is made more difficult if the impurities of dirty cotton are distributed through a largerquantity of material by mxing with clean cotton.


• The cleaning efficiency is strongly dependent on the TRASH %. It is also affected by the size of the particle and stickyness of cotton. Therefore cleaning efficiency can be different for different cottons with the same trash %.


• There is a new concept called CLEANING RESISTANCE. Different cottons have different cleaning resistance.


• If cotton is opened well in the opening process, cleaning becomes easier because opened cotton has more surface area, therefore cleaning is more efficient


• If automatic bale opener is used, the tuft size should be as small as possible and the machine stop time should be reduced to the minimum level possible


• If Manual Bale openers are used, the tuft size fed to the feed lattice should be as small as possible


• Due to machine harvesting , cotton contains more and more impurities, which furthermore are shatteredby hard ginning. Therefore cleaning is always an important basic operation.


• In cleaning, it is necessary to release the adhesion of the impurities to the fibres and to give hte particlesan opportunity to separate from the stock. The former is achieved mostly by picking of flocks, the latter is achieved by leading the flocks over a grid.


• Using Inclined spiked lattice for opening cotton in the intial stages is always a better way of opening the cotton with minimum damages. Ofcourse the production is less with such type of machines.But one should bear in mind that if material is recyled more in the lattice, neps may increase.


• Traditional methods use more number of machines to open and clean natural fibres.


• Mechanical action on fibres causes some deterioration on yarn quality, particularly in terms of neps . Moreover it is true that the staple length of cotton can be significantly shortened .


• Intensive opening in the initial machines like Bale breaker and blending machines means that shorteroverall cleaning lines are adequate.


• In a beating operation, the flocks are subjected to a sudden strong blow. The inertia of the impuritiesaccelerated to a high speed, is substantially greater than that of the opened flocks due to the low air resistanceof the impurities. The latter are hurled against the grid and because of their small size, pass between thegrid bars into the waste box, while the flocks continue around the periphery of the rotating beater.


• By using a much shorter machine sequence, fibres with better elastic properties and improvedspinnability can be produced.


• Air streams are often used in the latest machine sequence, to separate fibres from trash particlesby buoyancy differences rather than beating the material against a series of grid bars.


• There are three types of feeding apparatus in the blowroom opening machines
  

1. two feed rollers( clamped)


2. feed roller and a feed table


3. a feed roller and pedals
   

• Two feed roller arrangements gives the best forwarding motion, but unfortunately results in greatestclamping distance between the cylinders and the beating element


• feed roller and pedal arrangement gives secure clamping throughout the width and a small clamping distance, which is very critical for an opening machine


• In a feed roller and table arrangement, the clamping distance can be made very small. This gives intensiveopening, but clamping over the whole width is poor, because the roller presses only on the highest pointsof the web. Thin places in the web can be dragged out of hte web as a clump by the beaters


• Honeydew(sugar) or stickiness in cotton affect the process very badly. Beacause of that productionand quality is affected. Particles stick to metal surfaces, and it gets aggreavated with heat and pressure.These deposits change the surface characteristics which directly affects the quality and running behavior.


• There are chemicals which can be sprayed to split up the sugar drops to achieve better distribution.But this system should use water solutions which is not recommeded due to various reasons.


• It is better to control the climate inside the department when sticky cotton is used. Low temperature ( around 22 degree celcius) and low humidity (45% RH). This requires an expensive air conditioning set up.


• The easiest way to process sticky cotton is to mix with good cotton and to process through two blendingmachines with 6 and 8 doublings and to install machines which will seggregate a heavier particles by buoyanccy differences.


• General factors which affect the degree of opening , cleaning and fibre loss are,

1. thickness of the feed web


2. density of the feed web


3. fibre coherence


4. fibre alignment


5. size of the flocks in the feed (flock size may be same but density is different)


6. the type of opening device


7. speed of the opening device


8. degree of penetration


9. type of feed (loose or clamped)


10. distance between feed and opening device


11. type of opening device


12. type of clothing


13. point density of clothing


14. arrangement of pins, needles, teeth


15. speeds of the opening devices


16. throughput speed of material


17. type of grid bars


18. area of the grid surface


19. grid settings


20. airflow through the grid


21. condition of pre-opening


22. quantity of material processed,


23. position of the machine in the machine sequence


24. feeding quantity variation to the beater


25. ambient R.H.%


26. ambient teperature
    

• Cotton contains very little dust before ginning. Dust is therefore caused by working of the material onthe machine. New dust is being created through shattering of impurities and smashing and rubbing of fibres.However removal of dust is not simple. Dust particles are very light and therefore float with the cottonin the transport stream.Furthermore the particles adhere quite strongly to the fibres. If they are to beeliminated they are to be rubbed off.The main elimination points for adhering dust therefore, are thosepoints in the process at which high fibre/metal friction or high fibre/fibre friction is produced.


• Removal of finest particles of contaminants and fibre fragments can be accomplished by releasing thedust into the air, like by turning the material over, and then removing the dust-contaminated air.Release of dust into the air occurs whereever the raw material is rolled, beaten or thrown about.Accordingly the air at such positions is sucked away. Perforated drums, stationary perforated drums, , stationary combs etc.are some instruments used to remove dust

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