PROCESS CONTROL IN CARDING

PROCESS CONTROL IN  CARDING

 

Heart of the Spinning process is Carding  and it is the most important process in yarn manufacturing. It contributes a lot to the yarn quality. The following process parameters and specifications are to be selected properly to produce a good quality yarn with a lower manufacturing cost. 

THEORIES OF CARDING

Classical theory

According to this theory, a fibre can be carded between two oppositely inclined wire points covered surfaces moving with a high relative speed, provided the wire are so inclined that the sliding component of tension acting in the fibre is strong enough to move the fibre down the wire towards its base. This is fulfilled only when

cot α>µ

Where,

α= inclination of wire point

µ= coefficient of friction between the fibre & wire.

The classical theory does not take into account the centrifugal force & presence of air current due to rotating elements and it is argued that the carding force which slides fibre down the wire is so small in comparison to compression & centrifugal force that it has practically no effect on the filling of the clothing.

Strangs theory

This theory is based on Prandtls Boundarylayer theory. In a card, cylinder may be considered to be enclosed from all sides by flats, back & front plates, licker in, doffer and undercasing, rotates in medium of still air. According to boundary layer theory, a series of concentric layers of air of infinitesimal thickness surround the cylinder. As a, these layers also rotate along with the cylinder with different velocities. The velocity of the layer in contact with the cylinder surface will be equal to the cylinder. The velocities of each successive layers become less & less as its distance from the cylinder surface increases until a layer close to the base of flat wires is reached where the velocity is low. The presence of surrounding air current has been confirmed by Kamogawa, Kanda & Imami, Krylov. Because air has such a different velocities, within the space between flats & cylinder. When a tuft is introduced in this boundary layer, it is subjected to terrific force caused by the shearing action of air. The air shear force on a tuft can be given by following equation.

F = RVA/d

Where,

R= coefficient of viscosity of air at given temperature (poise)

V= velocity of air current (m/s)

A= projected area of tuft in the

d= depth of air boundary layer (m)

The depth of boundary layer appears to be the distance between of wire on cylinder & flats. The force therefore increases as the setting between flats & cylinder reduced. It is this shear force that separate the fibre tufts into individual fibres. The reason of fibre transfer from licker in to cylinder has been assigned to the boundary layer of licker in & cylinder. The air stream around cylinder having higher velocity removes fibre from licker in around which air stream revolves at lower velocity. A theory explaining carding action solely by boundary layer and shearing force of air current is unrealistic since carding has found to occur even at very speeds. However, air current which is definitely present due to rotating cylindrical element may have some role in carding.

Kaufmans Theory

Tufts held on cylindrical surface approach to cylinder flat zone at very high speed and are introduced into the narrow gap between the flats &cylinder wire points, which is generally much lesser in dimension than size of tufts. The resulting compression force, the fibres into the wire clothing of both flats & cylinder since the flats are practically stationary as compared to fast moving cylinder surface, the loading factor of compression force against the flat is greater than that against cylinder which is due its movement present larger surface area for the same compression force. According to Kaufman’s calculation, the compression force against cylinder acts on 6 time larger surface as compared to flat surface. The penetration of teeth into the tuft immediately followed by shearing action on tuft due to great difference in speed between flat & cylinder. As a result, the tuft is pulled apart into pieces. The process repeats itself when a part of tuft is held by cylinder approach the subsequent flats and this goes on. As a result, the size of tuft diminishes progressively. Generally, the opening and separation processis over by the time, the tuft goes to 5^th& 6^th flat location. As a result of carding action, the flat gets loaded with fibre & the cylinder is evenly covered by separated fibres. The drawing apart of fibre between the two surfaces may also be considered as the process of interaction of friction field created between the fibres and wire points of cylinder & between fibre and wire points of flat place one above the other. 

 The carding quality could be judged by

•Transfer Efficiency %

•NEP Removal Efficiency.

•Fiber Arrangement in Sliver 

"Transfer Efficiency is defined as the percentage of fiber transferred to dofferfrom cylinder per revolution of cylinder." The Transfer Efficiency of card is important from the point of view of determining the level of loading of the cylinder. A poor Transfer Efficiencyresults in excessive loading of fibres on cylinder, which restricts the furtherscope of card for improving the quality and increasing the production level.But the higher TransferEfficiency need not be taken as a measure of good carding. The cylinder load consists of two parts viz-basic load and working load. Thebasic load represents the fibres, which get absorbed into the cylinderfoundation over a period of time. And the working load represents fibre loadon surface from which fibre get transferred to the doffer. In the metallic cardsfibres on the surface constitute the cylinder load. A high cylinder load isnaturally determined to good carding. Since it enter fares with fibreseparation and individualization in cylinder flat region. Transfer Efficiency of card is very sensitive to some of the settings in card. Transfer Efficiency or Transfer Ratio is going to change not only frommachine to machine but also due to some machine parameters, like speed,settings, card clothing etc.When ordinary card clothing is used the Transfer Efficiency is about 5%. Nowa day with metallic wires being introduced, the Transfer Efficiency isenhanced up to 25%. This is because the loading and unloadingcharacteristics of the card vary with the flexible wire and metallic wire.A high cylinder load is naturally determined to good carding since it interfereswith fibre separation and individualization in cylinder flat region. Low transferefficiency is also undesirable, as it not only leads to building up of highercylinder load but also over working of fibres since poor transfer efficiencyresults in the fibres being taken round the cylinder more number of timesthan necessary and it causes nep generation.

Simpson's Analysis:

 The doffer collecting fraction i.e. the proportion of fibre transferred to dofferdepends upon the following ratio of wire angles i.e.R = (Sinβ2 + Cosβ2)/ (Sinβ1 + Cosβ1) 

β1 = inclination angle of cylinder wire point.

β2 = inclination angle of doffer wire point. This ratio reaches its maximum value 1.414 when 
β1 =90° and

β2=45°.

However, since a cylinder wire point angle of 90° would not given a goodcarding action, angle of 88° for cylinder and 45° for doffer are suggested.

 Keeping production rate constant, if doffer speed is enhanced with aproportionate reduction in sliver hank the load on cylinder decreasesand Transfer Efficiency increases. It means at the same production ratea combination of faster doffer and lighter sliver improves carding.An increase in cylinder speed reduces load on cylinder. An increase incylinder speed the load on cylinder reduces with a concomitantincrease in transfer coefficient.In the first case, in order to keep the production rate constant, thedoffer speed needs to be adjusted according to sliver linear density. This however changes cylinder doffer surface speed ratio since cylinder speed  remains  unaltered.

 In the Second Case, to keep the cylinder doffer surface speed ratioconstant, the cylinder speed is also changed in proportion to change indoffer speed. From above discussion it can be concluded that heaviersliver increases loading and decreases transfer efficiency. It had beenalso observed the load to be more for heavier sliver than the lighterone irrespective of production rate. Transfer efficiency was alwayshigher for lighter sliver.

An increase in production rate through doffer speed results in increasein loading and as well as transfer efficiency. It means even thoughtransfer efficiency increases, it does not increase proportionate toincrease in production rate, resulting cylinder load to increase.

 Transfer Efficiency increases with closer setting cylinder doffer setting.Cylinder loading to decrease and transfer coefficient to increase withcloser setting since it increases the zone of interaction betweencylinder and doffer.If the diameter of doffer is reduced by half, the zone of interaction isreduced by 0.7 and the coefficient of entrapment by 1.18. Hencereduction in size may increase cylinder load. A higher wire point

density on doffer will reduce cylinder load. Though cylinder loadreduces with enhancement of wire point density on doffer but theeffect is less critical than wire angle.

 

Chiefly, carding should separate the flocks into individual fibers. Additionally, carding results in cleaning, reduction of neps, aligning, blending, and elimination of some short fibers. The elimination of short fibers must, however, be viewed in proportion.

The main eliminated material is in the flat strips. Assuming flat waste at 1 to 2%, with about half in the form of short fibers there is such a minor precentage of short fiber elimination that it could hardly be measured with the current coarse staple measuring equipment. The operation of carding is performed with the aid of oppositely disposed sets of teeth or small wire hooks.

 

Fig. 16 – Carding disposition

The teeth face in opposite directions (Fig. 16). This is the typical arrangement between the main cylinder and the flats, and also between the main cylinder and the doffer. In order to enable carding to take place, v₁ must be greater than v₂ or v₂ must be in the opposite direction to v₁. In this action, the fibers are drawn apart, separated, and aligned.

Fig. 17 – Doffing disposition

The teeth of both clothing surfaces face in the same direction (Fig. 17). This arrangement is typical of the licker-in/main cylinder region. Here there is a deliberate transfer of material from one clothing surface to another, but v₁ must be greater than v₂ (feeding clothing).

.

If a fiber is held by friction at its ends on two teeth that are moving apart, tensile forces F act on the fiber in the axial direction owing to the drag from both sides (Fig. 18). Since the fibers are held on inclined surfaces, this tensile force can be resolved in accordance with the parallelogram of forces into two easily derivable components E and K, E being the component tending to draw the fibers into the clothing. The retention capability of the clothing is dependent on this component. The parameter K is the carding component, which presses the fiber towards the points of the other clothing surface. The fibers are in close contact with the other clothing surface and are processed intensively.

Fig. 19 – Forces in the doffing disposition

In the doffing arrangement, the directions of the forces acting at one tooth have changed (Fig. 19). Resolution of force F into its components gives component D, which presses the fiber against the tooth, and a stripping component A, which tends to push the fiber off the tooth. The fiber catches on the other tooth and is stripped

Centrifugal force is superimposed on the forces produced by the machine parts. However, in order to produce noticeable effects, substantial speeds are required, and these speeds arise practically only at the main cylinder and to some extent at the licker-in.

The centrifugal forces are effective mainly in directions away from the main cylinder, and act both on fibers and on foreign particles. In spite of this, the fibers are not thrown off (at least the longer ones), because the high air resistance due to the rotation presses the fibers back flat against the surface of the main cylinder. In comparison to all other forces, centrifugal forces are of minor significance except when considering trash and short fibers. In this case the centrifugal forces support the transfer of trash and short fibers from the main cylinder into the Flats.

Reference to the forces exerted by the teeth in the carding disposition will show that, all other things being equal, it is a matter of chance on which tooth tip the fiber will remain caught.

Such a random result is not acceptable everywhere. The doffer, although it is in the carding disposition relative to the main cylinder, must be able to take up a portion of the fibers. This is only possible if the doffing conditions are improved by the following:

• An increased tooth density in the doffer clothing (no longer used with rigid wire clothing).
• A clothing supporting the carding capacity, by using a greater carding angle for the doffer clothing and thus obtaining an increased drawing-in component E.
• Maintaining the catching effect of the clothing by frequent sharpening.
• Keeping the doffer clothing clean and receptive by continually withdrawing the web.
• A very narrow setting between main cylinder and doffer.
• Assisting transfer of fibers by special air-circulation conditions in the convergent space between the main cylinder and the doffer.

Even with these measures, the odds in favor of transfer are not even 50:50.

According to Artzt and Schreiber , the transfer factor with rigid wire clothing is only 0.2-0.3.

This means that, on average, a fiber rotates from three to five times with the main cylinder before it passes to the doffer. The effect is caused by the strong adherence of the fibers to the main cylinder, the fibers being drawn into the main cylinder clothing during continual movement past the flats

This is the most serious problem zone of the card because the licker-in must tear individual flocks out of the fairly thick feed sheet with enormous force. Fiber damage is scarcely to be avoided here.

However, stress on the fibers is not the only important aspect. The degree of opening, on which the quality of carding is directly dependent, is also important – the more so, the higher the production rate of the card.

The degree of opening, degree of cleaning and, above all, damage to the raw material can be influenced by:

• thickness of the feed sheet;
• density of the feed sheet;
• evenness of the feed sheet;
• throughput speed;
• rotation speed of the cylinders;
• cylinder clothing;
• form of the feed plate;
• arrangement of the feed plate (co-rotation or counter-rotation).

On the other hand, the licker-in is the main elimination zone for coarse impurities.

The main work of the card, separation into individual fibers, is performed between the main cylinder and the flats. Only by means of this fiber separation is it possible to eliminate the last dirt, especially the finer particles and dust. These pass into the flats, the extraction system, or the droppings.

When a flat moves into the working zone, it first fills up. This occurs relatively quickly, i.e. after only a few flats have moved into the working zone. Thereafter, hardly any further take-up of fibers occurs, and only carding takes place. Accordingly, if a fiber bundle does not find a place in the first few flats, then it can be opened only with difficulty.

It will be rolled between the working surfaces and usually leads to nep formation.

Equally important at this working position is the reduction of neps. Kaufmann indicates that 75% of all neps can be disentangled, and of these about 60% are in fact disentangled.

Of the remaining 40% disentanglable neps:

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

The intensity of separation depends on:

• the sharpness of the clothing;
• the spacing of the main cylinder from the flats;
• the tooth density of the clothing;
• the speed of the licker-in (high, but not too high);
• the speed of the doffer (high, but not too high).

Transfer of fibers from the main cylinder (T) to the doffer (A)

The arrangement of the clothing between the main cylinder and the doffer is not, as might have been expected, a stripping arrangement, but a carding arrangement. This is the only way to obtain a condensing action and finally to form a web. It has both advantages and disadvantages. The advantage, is that an additional carding action is obtained here. This is important, since the processing of the fibers differs somewhat from processing at the flats.

A disadvantage to be noted is the formation of hooks at this point. Before transfer, some of the fibers remain caught at one end on the teeth of the main cylinder (Fig. 22, T). During transfer, the other ends of the projecting fibers are caught by the clothing of the doffer and taken up. Since, however, the velocity of the main cylinder is much higher than that of the doffer, the teeth of the cylinder wire (T) smooth out the fibers in the direction of rotation, whereby the rear ends of the fibers remain caught on the teeth of the doffer (A).

By this means, they form hooks at their ends. In the web, and then in the card sliver, most of the fibers in the strand possess trailing hooks. However, aside from the serious disadvantage of hook formation, the carding effect mentioned is also produced here, since either the main cylinder clothing rakes through the fibers caught in the doffer clothing, or the doffer clothing rakes the fibers on the main cylinder. Neps can still be disentangled here, or non-separated neps disentangled during the next passage through the flats

The intensity of carding (as at other carding positions) is here dependent upon 

• type of clothing;
• geometry of the teeth;
• number of teeth per surface;
• distance between the carding surfaces;
• speed relationships;
• sharpness of the clothing;
• degree of wear of the clothing.

The diameter of the cylinders is also relevant. Large diameters imply a large contact surface at the working positions and thus, in addition to improvement of the transfer factor, longer raking of the raw material by the clothing

A disadvantage of web formation at the card that has already been mentioned is the formation of hooks. According to investigations by Morton and Yen in Manchester, UK, and others, it can be assumed that the fibers in the web show the following hooks:

• more than 50% have trailing hooks;
• about 15% have leading hooks;
• about 15% have doubled hooks,
• and less than 20% have no hooks.

Such fiber hooks, which effectively convert longer fibers to short fibers, cannot be permitted in the yarn. They must therefore be removed before yarn formation. This is done by the draft or by combing as the following description shows:

In the drafting arrangement, the fiber hooks may be bedded in the body of fibers either as leading or as trailing hooks (Fig. 23 and Fig. 24). Consider first a trailing hook (S): it will be seen that for a certain period it moves with the remainder of the fiber strand at the speed of the back roller towards the front roller. If the fiber tip passes into the nip region of the drawing roller, the fiber is accelerated. However, since the trailing end is moving with a relatively thick body of slowly moving fibers, the fiber is straightened before the whole fiber can reach the drawing speed — the hook is eliminated. On the other hand, leading hooks (K) are immediately caught bodily by the front roller and carried along unchanged (Fig. 24). The comber however mainly straightens out leading hooks, because the needles of the circular comb can grasp only these (Fig. 25).

Fig. 23 – Trailing hooks in the drafting arrangement

Fig. 24 – Leading hooks in the drafting arrangement

Fig. 25 – Leading hooks in the comber

 

To eliminate the hooks, leading hooks must be presented to the comber and trailing hooks to the ring spinning machine. As Fig. 26 and Fig. 27 show, reversal of the hook occurs at each processing stage between the card and these machines. Accordingly, a definite number of machine passages are required in intervening stages. Between the card and the comber, there must be an even number of passages, and there must be an odd number between the card and the ring spinning machine. In rotor spinning, the disposition of the hooks is of little significance.

Fig. 26 – Reversal of the dispositions of hooks between the card and the comber C, card; D, sliver-lap machine; E, ribbon-lap machine; F, comber

Fig. 27 – Reversal of the dispositions of hooks between the card and the ring spinning 

In cleaning, it is necessary to release the adhesion of the impurities to the fibers and to give particles an opportunity to separate from the stock. This is achieved mostly by picking flocks out of the feed material and by rapid acceleration of these flocks over a grid. Dirt, dust, foreign matter, and neps should be eliminated.

Cleaning was always an important basic operation, and it will become steadily more important. For one thing, owing to machine harvesting, cotton contains more and more impurities, which furthermore are shattered by hard ginning; for another, almost all new spinning processes impose substantially higher demands on the cleanliness of the material than the conventional methods.

The available possibilities for cleaning natural fibers can be divided broadly into three groups:

• chemical cleaning;
• wet cleaning (washing);
• mechanical cleaning.

This discussion will be confined to mechanical cleaning, in which usually only particles on the surface of the flocks can be removed.

The following procedures can be used:

• striking = falling out;
• beating = ejecting;
• scraping = separation;
• suction = separation;
• combing = extracting;
• use of centrifugal force = ejecting.

Striking, carried out by pins, noses, etc., on the  Type and degree of openingopening devices<//a>, leads to repeated collisions of the flocks with the grid-bars, causing foreign particles to drop through. In a beating operation, the flocks are subjected to a sudden strong blow. The inertia of the impurities, accelerated to a high speed, is substantially greater than that of the opened flocks owing to the low air-resistance of the impurities. The latter are hurled against the grid and, because of their small size, pass between the grid-bars into the waste box, while the flocks continue around the periphery of the rotating beater. Impurities can be scraped off when the fibers are guided, under relatively high friction, over machine components, grid-bars, mote knives, or even other fibers.

This operation is chiefly of importance in dust removal. Suction is less suited to the elimination of coarse particles than to extraction of dust. Transport air is fed through filters or perforated sheets; the small dust particles, which have been released during beating or transport, pass with the air through the fine openings. The flocks cannot pass.

In combing, needles pass completely through the body of fibers and draw impurities out of the inner regions. This is the only form of mechanical cleaning in which regions other than simple surfaces are cleaned.

Genuine exploitation of centrifugal force, in which there is no need for beating, is achieved, for example, in the card. Because of their high ratio of mass to surface, when compared with the fibers, the dirt particles are thrown out into the flats while the fibers are retained in the clothing by the air current. This system was used still more intensively in the “air stream cleaner” from the former Platt company (Fig. 28). In this machine the transport flow of air and stock (A) was subjected to rapid acceleration (V) before the transport direction was sharply altered, i.e. by more than 90° (E). The flocks were able to follow the diversion but the heavier impurities flowed straight on through a slot in the duct into a waste box (C).

However, as impurities have become smaller and smaller in recent decades, this system does not function any longer – it has been abandoned.

Ignoring perforated surfaces and combs, separation of stock and impurities is achieved by devices which let the impurities pass but retain the stock. In most cases a grid (beneath the beater) is used, and this can be additionally fitted with one or two mote knives in front of the grid (Fig. 29). Grids can be made of perforated sheet (low elimination effect); slotted sheet (low elimination effect); bars with edges, arranged one after the other. A controlled influence on the elimination effect can be obtained by means of grid and mote knives. The intensity of cleaning depends on the spacing of the grid from the opening device; the setting angle of the bars relative to the opening device; the width of the gaps between the bars.

Fig. 29 – Co-operation of opening element, grid bars (a) and mote knife (b

Cylinder wire(wire angle, height, thickness and population) flat tops specification licker-in wire specification doffer wire specification feed weight draft between feed roller and doffer cylinder grinding doffer grinding flat tops grinding cylinder, falt tops, doffer wire life Licker-in wire life Cylinder speed flat speed Licker-in speed setting between cylinder and flat tops setting between licker-in and feed plate setting between licker-in and undercasing elements like , mote knife, combing segment etc. setting between cylinder and doffer setting between cylinder and back stationary flats setting between cylinder and front stationary flats setting between cylinder and cylinder undercasing

Cylinder Wire And Cylinder Speed

Cylinder wire selection is very important, it depends upon cylinder speed, the raw material to be processed and the production rate. The following characteristics of cylinder wire should be considered.

»       wire angle

»       tooth depth

»       wire population

»       rib thickness

»       tooth profile

»       tooth pitch

»       tooth point

»       overall wire height

Wire front angle depends on mainly cylinder speed and coefficient of friction of raw material. Higher the cylinder speed, lower the angle for a given fibre. The cylinder speed in turn depends upon the production rate.

Higher production means more working space for the fibre is required. It is the wire that keeps the fibre under its influence during carding operation. Therefore the space within the wire should also be more for higher production. Higher cylinder speed also increases the space for the fibre. Therefore higher cylinder speed is required for higher production. In the case of high production carding machines, the cylinder surface is very much higher, therefore even with higher number of fibres fed to the cylinder; the cylinder is renewing the carding surface at a faster rate.

Higher the cylinder speed, higher the centrifugal force created by the cylinder, this tries to eject the fibre from the cylinder, along with the trash. It is the cylinder wire's front angle which overcomes the effect of this force. Low front angle with too low cylinder speed and with high frictional force will result in bad quality, because the fibre transfer from cylinder to doffer will be less. Hence recycling of fibres will take place, which result in more neps and entanglements. The new profile with less free blade avoids loading of the cylinder with fibre and/or trash. This helps in keeping the fibers at the tip of the tooth. The movement of the fibres towards the tip of the tooth coupled with centrifugal action demands an acute front angle to hold the fibre in place during carding.

Lack of stiffness associated with fine and/or long fibres necessitates more control during the carding process. This control is obtained by selecting the tooth pitch, which gives the correct ratio of the number of teeth to the fibre length. Tooth pitch reduction is therefore required for exceptionally short fibres and those lack stiffness.

Number of points across the carding machine is decided by the rib width. It is selected based on the production rate and fibre dimensions. Finer the fibre, finer the rib width. The trend is to finer rib width for higher production.

The population of a wire is the product of the rib thickness and tooth pitch. The general rule is higher populations for higher production rates, but it depends upon the application. Sharp tooth points penetrate the fibre more easily and help to intensify the carding action. Cut-to-point wires are sharp and they have no land at all. The effective working depth of a cylinder wire tooth for cotton is approximately 0.2mm and for synthetic materials approx.0.4mm. Manmade fibres require more space in their cylinder wire than cotton. More tooth depth allows the fibre to recycle, resulting in damaged fibres and neps. If tooth depth is insufficient, there will be loss of fibre control. This will result in even greater nep generation. Looking into the above details, the following specifications can be used as a guideline.

MATERIAL	PRODN. RATE	RIB WIDTH	ANGLE(degrees)	POPULATION
Cotton low grade	low	0.6	65	700
Cotton low grade	high	0.5	55	840
Cotton Medium	low	0.6	60	800
Cotton Medium	high	0.4 to 0.5	55	840 to 950
Cotton fine	low	0.5	60	840
Cotton long	high	0.4 to 0.5	55	900 to 1100
Synth.coarse	low	0.7 to 0.5	70	550 to 650
synth.coarse	high	0.6	65	760
Synth.medium	low	0.7	65	700
synth.medium	high	0.5	65	760
Synth.fine	low	0.6	65	700
synth.fine	high	0.5	60	840

MATERIAL	PRODCUTION RATE	CYLINDER SPEED
cotton	low	360 to 400
cotton	medium	430 to 470
cotton	high	500 to 550
synthetic	low	300
synthetic	medium	380
synthetic	high	460

Doffer, Licker-In and Flat Tops:

The basic function of doffer is to strip the fibers from Cylinder. Please remember that the action between cylinder and doffer is carding action (or combing action or point to point action). The doffer wire's front angle plays a very important role in releasing the fibre from the cylinder. For most carding applications the optimum angle is 60 degrees.

Increased population over 400 ppsi does not give any advantage in the production of quality yarn. For smaller doffers, 5 mm doffer wire height helps in transferring the fibres from cylinder to doffer. If the fibre holding capacity of the doffer wire is less due to fibre friction or due to very high doffer speed, it is better to use a doffer wire with striations. For high production carding it is always better to use doffer wire with striations.

Licker-in plays a major role in opening the fibre tufts. In general 85 degrees is used both for synthetic and medium and long cottons. For coarse and dirty cottons 80 degrees can be used. Strength, hardness and sharpness are very important for Licker in wire. Licker-in wires should never be ground. Thinner blades penetrate the fibres more efficiently and increase the wire life.

Higher number of rows per inch gives better results. Now up to 12 rows per inch is being used. This is always better compared to 8 rows per inch. If the wire pitch is not sufficient, it can be compensated by increasing the licker-in speed. Higher licker-in speeds for fine and long cottons will rupture the fibres. Licker-in speed depends upon the fibre type and the production rate.

It is better to use a flat top with more than one population. The general combination is 280/450.This is suitable for both cotton and synthetics. Please remember that the rigidity of the fillets is different for cotton and synthetic. If cotton flat tops are used for synthetic processing, the load on the cylinder will be more, more heat will be produced and hence the probability of cylinder loading due to electrostatic charge will be high. Instead of using Rigid type flat tops, it is better to use semi-rigid type flat tops while processing synthetic fibres.

Settings:

The setting between cylinder and doffer is the closest setting in the card. This setting mainly depends upon the cylinder speed, hank of the delivered sliver and the type of wire. Cylinder speed upto 360, the setting should be 0.1mm. For cylinder speeds more than 450, the setting ranges from 0.125 to 0.15.If the setting between cylinder and doffer is very close, the wires will get polished and this will affect the fibre transfer. If the setting is too wide, the fibres will not be transferred to doffer from the cylinder, hence cylinder will get loaded. While processing synthetic fibres cylinder loading will badly affect the yarn quality. Moreover, it is difficult to improve the wire condition if the loading is severe. The only solution would be to change the wire. Therefore enough care should be taken while processing synthetic fibres.

The most critical setting in a carding machine is between cylinder and flat tops. While processing cotton, it can be as close as 0.175 mm provided the mechanical accuracy of flat tops is good. Since most of the cards are with stationary flats at the licker-in side, the setting from the back to front for flats can be 0.25, 0.2, 0.2, 0.2, 0.2mm.

Closer the setting between cylinder and flats, better the yarn quality. Neps are directly affected by this setting. Of course, very close setting increase the flat waste. For processing cotton the setting can be 0.25, 0.2, 0.2, 0.2, 0.2mm. For synthetic fibres it can be 0.3, 0.25, 0.25, 0.25, 0.25mm. Most of the cards are with 6 to 11 stationary flats at the licker-in side. This setting can start with 0.4 mm and end with 0.25mm. The wire points can start with 140 ppsi and end with 320 ppsi. The work done by the first few stationary flats is very high, therefore the wear of these flats is also high. It would be better if the first 50% of the flats are changed after 100000 kgs of production and the rest after 150000 kgs of production. These stationary flats open the material so that, the setting between cylinder and flats can be as close as possible.

The setting between feed plate and Licker-in depends upon the type of feed plate. Conventional feed plate setting is decided mainly by the feed weight and to some extent by the fibre length and type. With the latest feed plate and feed roller arrangements, the setting is decided mainly by the fibre length and to some extent by the feed weight.

Normally the setting between the feed plate and Lickr-in is around 0.45 to 0.7mm, depending upon the feed weight and fibre type. The setting between Licker-in and the first mote knife is around 0.35 to 0.5 mm. This helps to remove the heavier trash particles and dust. Closer the setting, higher the waste percentage. The setting between Licker-in and combing segments is around 0.45 to 0.6. This helps to open the material.

Some cards have two mote knifes in the Licker-in undercasing. The setting is around 0.4 to 0.5mm. This helps to remove the smaller trash and dust particles.

The setting between the cylinder and stationary flats at Doffer side helps to transfer the fibres to doffer by stripping the fibres to the top of the cylinder wire. This setting can be as close as 0.15mm. Number of wire points on stationary flats also plays major role. It is normally around 300 to 400. For a high production application it can be as high as 600. For cotton processing, the stationary flats are fixed with a knife attachment. The setting should e as close as possible, i.e. around 0.15mm. This helps to remove the trash particles of very small size. 

The setting between cylinder and cylinder undercasing should be as per the manufacturer's recommendation. The design of undercasing is different for different manufacturers. This setting is very important, as wrong settings will affect the fibre transfer and can also create air turbulance.

Speeds:

Higher cylinder speed helps fibre transfer. Higher the production, higher should be the cylinder speed. Higher cylinder speed improves carding action, thereby imperfections are reduced. Higher Licker-in speed for coarse fibres and diry cotton helps to remove the trash and improves, better the yarn quality. For fine and long cottons, higher speed results in fibre rupture, therefore, flat waste and comber noil will be more.

Higher flat speed improves yarn quality and at the same time increases the flat waste. With the same flat speed, higher the carding production, lower the flat waste and vice-versa. Very high tension drafts will affect carding U%. It is better to keep the draft between feed rollers to doffer around 75 to 95. The results are found better with these drafts.

Wire Maintenance:

For a modern cylinder wire of 2mm height, grinding with the normal grinding stone is not recommended. It is better to use TSG grinder from GRAF. It is better to grind the wire every 2nd or 3rd month, so that the sharpness of the wire is always maintained.

TSG grinder does not grind the wire, therefore if the wire is worn out very badly the quality improvement using this grinding machine will be nil. Frequent grindings are recommended. If TSG grinder is not available, it is better not to grind 2mm wires. The number of traverse should increase depending upon the life of the wire. The number of traverse for successive grindings should be like this 3, 5, 10,17 etc. Anyway the best method is to confirm with the microscope. If the grinding is not sufficient, the number of traverse should be increased.

Doffer is still working with a concept of Land formation. A normal grinding machine will be good for doffer grinding. All the wire points should be touched by the grinding stone. A slow and gradual grinding with the grind-out concept will give the best results. Harsh grindings will result in burr formation on the land. This will increase the number of hooks in the fibre, thereby the effective length of the fibre from this card will be reduced.

Flat tops grinding is very important. Every time a flat top is ground, yarn quality is improved. It is better to use a grinding machine with the emery fillet. Frequent flat tops grinding will result in less neps and the yarn quality will be consistent. Some mills increase the life of the flat tops compared to cylinder wire. But it is better to change flat tops and cylinder wire together for better and consistent yarn quality.

It is a good practice to check the individual card quality before changing the wire. Licker-in wire should be changed for every 150000 kgs. Earlier changes will further improve the yarn quality. Stationary flats should be changed for every 150000 kgs. But it is a good practice to change the first 3 or 6 stationary flats at Licker-in side for every 100000 kgs. This helps to maximise the carding effect between cylinder and doffer which is critical for better yarn quality.

Others:

Lower the feed variation, better the carding quality. Even if the card is with an autoleveller, feed variations should be kept as low as possible (plus or minus 10%). With the latest chute feed systems, it is easy to control the feed variation with in 5%. Lower the feed variation, lower the draft deviation, therefore yarn quality will be consistent.

If the card is with autoleveller, the nominal draft should be selected properly. Improper selection will affect sliver C.V% and yarn quality.

Improper feed roller loading and the setting between feed roller and feed plate will affect the quality, especially C.V% and neps. Before mounting, the eccentricity of cylinder and doffer should be checked. Eccentric cylinder and doffer will affect the U% and will affect C.V. % also. Defective bearings, gears and timing belts will affect U%. Uneven distribution of tension drafts will affect U%.

Selvedge of feeding bat should be good. It should not be folded and double. This will increase the neps and sometimes it may result in cylinder loading. Lap fed to the carding machine should be narrower than the nominal width of the machine. For processing cotton, minimum 800 pascal suction pressure should be maintained at trash master (at knife) for effective removal of trash and dust particles. Worn or damaged scraper blades will lead to web sticking to crush rollers. Insufficient pressure between scraper blade and crush roller will also result in web sticking. If the calender roller pressure is too high web sticking will also be high.

If Cylinder undercasing nose at doffer side is too long for the type of fibre being carded web disappearing problem will arise. If the nose is set too close to the cylinder, web disappearing problem will arise. Damaged and dull doffer wire also will result in web disappearing problem.

  Key Features of Trützschler TC-11 Card are:

1. Fully-integrated tuft feeder DIRECTFEED- High production with even card feeding
2. Setting Optimiser T-Con - For maximum utilisation of the TC 11 potential
3. Flexible Integral Feed Tray SENSOFEED+/- - Short-wave levelling for a low sliver count variation
4. Sliver former WEBSPEED - Completely maintenance-free
5. Precision Knife Setting System PMS - Adjustment of waste amount in no time at all
6. Aluminium flat bars without screw connection - Quick flat exchange, without tools
7. Magnet Flat System MAGNOTOP - Replacement of flat tops directly on the machine without tools
8. Precision Flat Setting System PFS - Reproducible flat setting in only a few seconds
9. Flat Measuring System FLATCONTROL - Objective and very precise flat adjustment
10. Infinitely variable setting of the flat speed - Exact adaptation to the fibre quality in only a few seconds
11. Electronic cylinder brake - Reduces cleaning and maintenance time
12. Nep sensor NEPCONTROL - Online measurement of neps and trash particles
13. Computer control with touch screen - Simple operation and targeted maintenance
14. Digital motor controls - Maintenance-free and high-precision
15. Spectrogram monitoring - Stops the card in case of faults in the spectrogram
16. Thick place monitoring - Stops the card in case of excessive thick places in the sliver
17. Spectrogram analysis - Assists in finding the cause of spectrogram errors
18. Management of maintenance and card clothing - Targeted maintenance support
19. 3-roll WEBFEED Unit - For gentle pre-opening
20. WEBFEED with one roll - For the carding of man-made fibres or ELS cotton
21. Needle or clothed rolls - Perfectly tailored to your product
22. Thick place monitoring and metal detection in the feed area - For quality assurance and protection of the card
23. Long- and short-wave levelling system - For perfect card sliver evenness
24. Special toothed belts for flat guiding - Flat replacement without tools
25. Premium clothings from TCC, made of high-grade steel - Extended service life ensures longer maintenance intervals
26. High-precision aluminium elements with super-smooth surfaces - Gentle material guidance in the fibre-carrying areas
27. Central safety locking system - High operational safety

     

Unique features of the TC 15 in the high-performance segment are: 

• Expansion of performance limits through T-MOVE and T-CON
• Increased delivery speeds during can change (can diameter 1,000 mm and 1,200 mm)
• Reduced air consumption
• Smallest floor space in comparison to production 
• Lowest waste quantities

New web doffing

Today's technology allows delivery speeds well above 400 m/min in practice. For this reason, web doffing and sliver forming have been newly developed for speeds up to 500 m/min for the TC 15.

Quality at the highest level

"The length of the carding section determines the quality". Even though this has been common knowledge for some time, Trützschler is the only one with the longest carding section worldwide. For this reason, Trützschler cards have set the standard for quality for decades. The valuable raw material cotton is optimally used, which ultimately also contributes to an increase in productivity.


 

C 70 High-performance card - The card with the maximum active carding area

The C 70 high-performance card achieves excellent quality values at highest production for all yarn applications. This is based on the well-proven 1.5 m working width and maximum active carding area. Precise flats guiding and innovation in the pre- and post-carding area allow, with the selective waste extraction, an excellent raw material exploitation and sliver quality. With the integrated grinding system IGS, the sliver quality is maintained at a high level. By utilising draw frame modules instead of the classical can coilers, the customer has the possibility to optimally layout the process.

Economy

• High production performance with top quality for all yarn applications thanks to the maximal active carding area and optimised pre- and post-carding area.
• Excellent raw material exploitation thanks to the adjustable knife on the licker-in, variable insertions of the extraction elements in the pre- and post-carding area as well as to the electronically adjustable flat speed.
• The lowest energy balance of the C 70 is based on the combination of compact construction with small, movable masses and innovative machine geometry and flats area.

Quality

• IGS – ensures a consistently good sliver quality with permanently sharp clothings and therefore increases the service life of clothings.
• High production and sliver quality with the reliable autolevelling of the card and controlled fibre transport.
• Sophisticated detailed solutions for absolutely uniform batt weight and web formation give a card sliver of superior quality and lead to machine operation requiring no intervention.

Flexibility

• The modular construction permits a rapid adjustment to new raw materials and requirements.
• The draw frame modules facilitate an optimal process, adjusted to raw material and application.
• The option exists to arrange the card lines with 8 cards, line production up to 600 kg/h or with 10 C 70 cards, line production up to 1 200 kg/h.

The new Rieter C 70 high-performance Card

With the C 70, Rieter has succeeded in raising the dependable technology of the 1.5 m wide card to a new level. Basis for the improvement in production and quality is the enlarged active carding area in combination with the precisely controllable carding gap. Optimized extraction elements in the pre- and post-carding area lead to a high raw material utilization. This raw material utilization and the lower energy consumption per kilogram of card sliver contribute to the efficient production of superior quality yarn.

The C 70 Card with 1.5 m width and optimized carding quality

Enormous leap in productivity

The production performance of the C 70 card, compared to that of the C 60, can be increased by up to 40% with equal or better sliver quality. This marked improvement is achieved by redistributing the carding zones in the flats area and by redesigned flats guiding.

Key factor, carding area

With the C 70, 32 flats are operative. Compared to the C 60, the active flats area is increased by 45% and compared to a conventional card by 60%. This means that with each cylinder clothing of the C 70, distinctly more carding work is performed.

Quality through precise carding gap

The precise flats guiding and the revised flats design permit a very exact and reproducible setting of the distance between the cylinder clothing and the flats, so that a minimum of 0.1mm is possible. This precision leads to improved carding results. Furthermore, the flats cleaning of the C 70 has been completely reorganized.

Optimal raw material exploitation

The customer profits from an optimal fiber utilization thanks to the extraction knife in the pre- and post-carding area. The extraction knife with variable ejector distance can be exchanged without tools in the shortest possible time.
The flats speed is infinitely adjustable via the frequency converter, independent of the cylinder speed. This means the card can be individually adjusted and thereby optimized to the type of raw material being processed.

Uniform sliver quality

The proven integrated cylinder grinding system IGS – an exclusive Rieter product – is available as an option and provides the customer with constant quality values during the whole lifespan of the card clothing. With this fully-automatic grinding system, downtimes for clothing maintenance are a thing of the past.

Low energy consumption

The high production performance of the C 70 positively affects the energy consumption per kilogram of produced card sliver. The C 70 has a 15% lower energy requirement than that of the C 60 which, considering the globally rising prices of electricity, represents a principal factor in the economic production of yarn.


 

CARD LC636

SALIENT FEATURES

• Higher Production up to 250 kg/hr
• Working width of 1,500 mm
• Pressure regulated chute for better feeding
• Specialized profiled finger plate
• Opening roller with mote knife for trash ejection
• Special stripper roller with tangential air strips for effective
  feed to card
• Individual drive for feed, opening and stripper rollers
• Direct feeding to card feed roller
• Single Licker-in arrangement with Arcual combing segment
• Highest Active Carding Area of 1.95 m2
• Highest Active Cylinder Area of 3.95 m2
• Optimum cylinder diameter of 1,017 mm, leading to lower thermal expansion and higher centrifugal force
• Standalone 40” Linear Coiler

SALIENT FEATURES

• Higher Production, up to 120 kg/hr
• Triple / Single Licker-in arrangement
• Aluminium alloy flats with increased no. of revolving flats
• Highest Active Flat Index (AFI)
• Pressure Regulated Chute for Uniform Feeding
• Optimum waste extraction at right place
• Precision and balanced geometry of technological elements
• High take up web doffing device

Card LC363 / LC361 is designed for higher production up to 120 kg/hr with distinctivefeatures to produce high quality sliver in every variety of cotton, man-made fibre and blends.“Well carded is half spun”. Card LC363 / LC361 is configured to produce better yarncharacteristic with reduction in running cost.

PRESSURE REGULATED CHUTE

Pressure regulated chute ensures active compression on the fibre material resulting intooptimal batt structure for highest sliver quality.

FEED AND LICKER-IN ZONE

Card LC363 / LC361 has unidirectional feeding arrangement with saw toothed feed rollerfor gripped and gentle fibre transfer to Licker-in zone. The material is fed from feed roller inthe direction of rotation of the Licker-in to eliminate the fiber rupture. Variable nippingdistance can be set for processing different staple fibres.
The triple Licker-in system with high speed will provide more percentage of individualizedfibers. The 1st Licker-in has double knife and an Arcual combing segment for intensivecleaning and pre opening. 2nd and 3rd Licker-in has a replaceable combing strip for furthergentle opening. Optimised wires and Specialized Angle help reduce load to cylinder.Resulting in better carding action in cylinder zone.

ACTIVE FLAT INDEX (AFI)

The Active flat index is a measure of actual carding area in the machine. The real cardingaction takes place between cylinder clothing and revolving flats. In Card LC363 / LC361,110 degrees of cylinder surface is occupied by the revolving flats (36 working flats out of97 total flats) which in linear terms works out to 1.296 mtrs over the carding width of 1 mtr. This helps to achieve better sliver quality.