Manual of textile technology

However removal of dust is not simple. Dust particles are very light and therefore float with the cotton in the transport stream. Furthermore the particles adhere quite strongly to the fibres. If they are to be eliminated they are to be rubbed off. 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.

One piece chut is a closed system, i. 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. Owing to the direction of feed roller, the fibre batt runs downwards without diversion directly into the teeth of the taker- in licker-in which results in gentle fibre treatment.

This helps to reduce faults in the yarn. It clearly shows that fibre gets deteriorated at this opening point. Only the degree of deterioration can be controlled by adjusting the following 1.

The first one is constructed as needle roll. This results in very gentle opening and an extremely long clothing life for this roll. 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 good quality. But the performance may vary for different materials and different waste levels.

It exerts an influence on 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. At the Taker-in perhaps 0. 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 points per unit time must also be increased. Hence the best way is to add carding surface stationary flats. Carding plates can be applied at 4. If carding segments are not used, the load on cylinder and flats will be very high and carding action 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.

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 does not find place at the first few flats, then it can be opened only with difficulty. In reverse movement, the flats come into operative relationship with the cylinder clothing on the doffer side. At this stage, the flats are in a clean condition.

They then move towards the taker-in and fill up during this movement. Part of their receiving capacity is thus lost, but sufficient remains 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 part of the dirt is hurled into the first flats directly above the taker-in. 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 additional carding action is obtained here and it differs somewhat from processsing at the flats.

A disadvantage is that leading hooks and trailing hooks are formed in the fibres , beause the fibres remain caught at one end of the main cylinder leading hook and some times on the doffer clothing trailing hook. The fibre must enter the carding machine, be efficiently carded and taken from it in as little time as possible.

According to an investigation by morton and Yen in Manchester, it can be assumed that 1. Lawrence, A. Dehghani, M. Mahmoudi, B. Greenwood and C. Iype School of Textile Industries, University of Leeds Over the last 30 years numerous developments have taken place with the cotton card.

The production rate has risen by a factor of 5 with the main rotating components running at significantly higher speeds. Triple taker-in rollers and modified feed systems are in use, additional carding segments are fitted for more effective fibre opening, and improved wire clothing profiles have been developed for a better carding action.

Advances in electronics have provided much improved monitoring and process control. Most of these developments have resulted in enhanced cleaning of cotton fibres, reduced neppiness of the card web and better sliver uniformity. Despite the various improvements made to the card a commonly held view is that more is known about the cleaning processes on the card than about the carding process itself. With regard to these factors, increased production rate can reduce carding quality. It is therefore of importance that a better understanding is established of the effect that carding actions have on such quality parameters, particularly at high production rates.

The most widely accepted view of how fibres are distributed within the card under steady-state conditions is illustrated in Figure 1. Reported studies into the fundamentals of the carding process have largely been concerned with how the principal working components of the card affect this distribution of fibre mass and interact with the mass to achieve:trash and nep removal from cottons; the disentangling of the fibre mass into individual fibres, with minimal fibre breakage; and the alignment of the fibres to give a sliver suitable for drafting in down stream processes.

These actions occur at the interface of the card components within the three zones indicated in Figure 1. To effectively breakdown the fibre mass feed into tuftlets with minimal fibre breakage, the taker-in wire has to be coarse, with a low number of points per unit area 4.

The objective is to obtain gentle opening of the fibre mass feed and easy transfer of the tuftlets to the cylinder. For longer cottons and synthetics, a 90o or negative rake may be needed to facilitate gentler opening and satisfactory fibre transfer to prevent lapping of the taker-in.

Fibres, usually very short fibres, which are not adequately held by the teeth or present in the interspaces of the clothing are ejected causing fibre loss. However, it is the mote knives that govern the amount of fibre to trash i. Experimenting with the settings of two mote knives below the taker-in, Hodgson found that the absence of the knives greatly increased the lint content with little increase in trash.

With the knives present, the best setting was that which gave the least waste since increasing the amount of waste did not improve cleaning. Artzt found that irrespective of teeth density and tooth angle the waste increased with taker-in speed but the increase was attributed to higher lint content.

It is reasonable to assume that the smaller the tuftlet size and the greater the mass ratio of individual fibres to tuftlets the better the cleaning effect of the taker-in. Supanekar and Nerurkar suggest that the takerin breaks down the fibre feed into tuftlets of various sizes and mass, conforming to a normal frequency distribution. In the case of cotton, some tuftlets may consist of only fibres whilst others will contain seed or trash particles embedded among the fibres, these tuftlets constituting the heavier end of the distribution curve.

Thus, the mean of the distribution would depend on the trash content of the material, as well as on the production rate, the taker-in speed and the wire clothing specification.

However, the authors did not report any data to support their ideas. Nittsu using photographic techniques studied the effect of process variables on tuftlet size. It was found that the total number of tuftlets decreases the closer the feed plate setting, the lower the feed rate, the smaller the steeper rake of the saw-tooth clothing and the higher the licker-in speed.

Since th licker-in opens the batt into both tuftlets and individual fibres, a decrease in the total number of tuftlets suggests an increase in the mass of individual fibres. Liefeld calculated estimates of the opened fibre mass at various stages through the blowroom and gives a value of 50mg for tuftlets on the taker-in. Mills claims that the calculated optimum number of fibre per tooth is one, and that this should be maintained at increased production rates by increasing the taker-in speed.

There is, however, the question of fibre damage at high taker-in speeds. In all cases cotton fibres of The level of fibre breakage, however, would seem to depend on production rate and the batt fringe setting to the licker-in. High production rates achieved by increased sliver counts and a close setting of the batt fringe result in significant fibre breakage.

No fundamental studies have been reported on the forces involved in the fibre-wire interaction of revolvingflat card components. However, Li and et al report a simulated study of fibre-withdrawal forces for wool in high-speed roller- clearer cards.

Although impact forces could cause damage, it was found that card component speeds had no significant effect on the withdrawal-force, and that fibre configuration and entanglement were the important factors. The importance of producing small size tuftlets is evident form the various components fitted in the fibreopening zone on modern short-staple cards. Saw-tooth wire covered plates, termed combing segments, fitted below the taker-in or built into the taker-in screen are claimed to give improved trash removal.

Reportedly, the stationary flats fitted between the taker-in and the revolving flats provide extra opening of the tuftlets transferred to the cylinder from the taker-in. They also act as a barrier to large, hard, trash particles such as seed coats, protecting the wire of the revolving flats from damage, particularly at high cylinder speeds. This enables finer wire to be used for the revolving flats and thereby improves the cleaning effect of the interaction between cylinder and revolving flats.

The chances are also reduced of longer length fibres becoming deeply embedded in the revolving flats to become part of the flat strips. These attachments are widely accepted by the industry as beneficial, particularly at high production speed. However, there is no published systematic study of their effectiveness in reducing tuft size, and the effect of stationary flats on the recycling layer, Q2, is unknown. The little information that is available attempts to illustrate the effectiveness of these components on yarn quality, but there is no evidence of analytical rigour in the way the data were obtained.

Fig 3. It would appear that the added components in the taker-in region might well reduce the dust deposit in the rotor, but the results showing improvements in yarn quality are not convincing, and in all cases the stationary flats above the doffer appear the most effective. Leifeld reports that the cylinder — revolving flats carding action occurs when the fibre mass delivered to the cylinder is in a highly opened state.

Tandem cards are said to give a high standard of carding with low nep and trash levels in the card web. This is because a uniform web of almost discrete fibres is fed to the second cylinder of the tandem card and closer revolving flat settings with higher cylinder speeds can be used.

Single taker-in systems, even with combing segments and stationary flats, cannot give as high a degree of opening. However, Leifeld reports that a triple taker-in system facilitates high taker-in speeds and, fitted to a single-cylinder card, feeds a uniform web of discrete fibres to the cylinder, thereby offering a more cost- effective process than the tandem card, but no comparative data for the two types of card are given.

This is because the fibres would remain largely disoriented with a high proportion of them lying transversely to the direction of mass flow when transferred to the cylinder and subsequently to the revolving flats. This can result in fibre loss during transfer to the cylinder and an unevenness of the fibre mass across the cylinder width, causing neps to be formed and degrading the carding action between the cylinder and the revolving flats.

It is claimed that good carding requires a thin, uniformly distributed sheet of well-opened tuftlets fed to the cylinder from the taker-in. Fujino reports results that would appear to confirm the view that as the level of opening increases through faster taker-in speed, the degree of fibre parallelism on transfer to the cylinder decreases.

The nep level in the card web was, however, observed to decrease noticeably with increased taker-in speed. In contrast to these findings Harrison states that increasing taker-in speed did not affect the nep level in the card web, the exception being for low micronaire cottons. The apparent contradictions in these results suggest that a better understanding of the transfer mechanism may be needed which takes into account fibre properties.

Fibre Mass Transfer to Cylinder Two contrasting views have been reported on the mechanism of fibre transfer. Oxley suggests that the fibre mass on the taker-in is ejected between the cylinder wire and the back plate. Whereas Varga believes that the fibre mass is stripped from the taker-in in the following way. In the feed to the card, tufts and fibres lie randomly and by the action of the taker-in are brought into length-wise orientation in the direction of the roller rotation.

The trailing ends of newly formed tuftlets protrude above the taker-in wire and are easily stripped by the cylinder wire clothing. This implies that the transfer involves a reversal of the leading and trailing ends of the fibres. Further orientation and parallelism of the fibre mass is thought to occur during the transfer onto the cylinder. No experimental work has been published which specifically involves a study of the transfer of fibres from the taker-in to the cylinder.

Therefore it has yet to be established whether at the interface, the cylinder, which has the faster surface speed, strips the fibre mass with its clothing or the taker-in, through the action of centrifugal forces, ejects the tuftlets and single fibres onto the cylinder, or a combination of both occurs.

It is also of interest to determine if the airflow in the region assists the fibre mass transfer. Whatever the case, the fibre mass is likely to be subjected to an uncontrolled drafting effect, which could introduce irregularities in the mass flow. Zone 2: The Fibre Carding Zone In the carding zone, it is the interaction of the fibre mass and the wire-teeth clothing of cylinder and flats that fully individualises the fibres and gives parallelism to the fibre mass flow.

They are, thus, easily removed and more firmly held by the opposing teeth of the flats. It is therefore assumed that as a flat enters the carding zone it becomes almost fully loaded with fibres, the airflow within the region assisting the fibre mass transfer. Having been stripped of fibre mass, subsequent following areas of the cylinder wire clothing move past the fully loaded flat and proceed to comb fibres from the flat, carrying them towards the doffer. The action of combing causes the fibres to be hooked around the cylinder wire points and prevents them from being easily removed by other flats.

First, a carding action where the upper layer of a tuftlet or a loosely opened fibre group is caught and held by the flats whilst simultaneously the bottom layer is sheared away by the fast moving cylinder surface. This action causes the top to hang from the flats and to contact subsequent parts of the cylinder wire surface resulting in the second action which is combing, where the wire clothing of the cylinder hooks single or a small group of fibres and combs them from the top layer.

A second flat catches the bottom layer on the cylinder and the actions are repeated. In this way tuftlets or groups of fibres are separated into individual fibres. By making abrupt changes in the colour of the fibre mass fed to the card, Oxley demonstrated that tuftlets from the load on a given flat are carried forward by the cylinder clothing and separated into individual fibres over a small number of preceding flats, typically 4.

It was concluded that the interchange of fibres between cylinder and flats does not occur over the full carding zone. The load then increases exponentially with time, reaching nine-tenths of the final value within minutes. Completion of the load takes place slowly during the remainder of the working time.

See Fig 4. As shown in the figure, with flats moving in the reverse direction the load first increases rapidly with time and then slows until the flat is about to leave the working area. Here it encounters the fibre layer being transported on the cylinder surface from the taker-in.

The flat receives a sudden addition of fibre mass to become fully loaded, and, in agreement with other results, the load weighs more than for the forward direction of motion.

It may be reasoned that the number of flats involved in separating a tuftlet depends on the tuftlet size, the mass flow rate and the flat setting. The larger the tuftet, the higher the production rate and the closer the flat settings, the greater the number flats involved in the separation of a given tuftlet. Bogdan reports that flats tend to load quickly at the beginning of their cycle of contact with the cylinder.

This, however, is only a partial loading, since the fibre mass tends to resist more fibres entering the space but, in the case of cotton, not the leaf and trash particles present. Analysis of the trash in cotton flat strips showed that initially the percentage of trash in a given flat strip is low and increases slowly during the first 10 minutes of carding, then remains at almost a constant value.

The final percentage depends on the trash content of the cotton. For a fixed production rate, the amount of flat strips was found to be directly proportional to the flat speed, but provided the speed was such that the working time was not less than 10 minutes, both the weight and composition of the flat strips remained approximately constant.

A combination of centrifugal forces, mechanical contact with the flat wire and air turbulence causes the trailing ends of fibres attached individually to the cylinder clothing to vibrate and shake loose trash and dust particles. Short fibres which cannot adequately cling to the cylinder clothing will also be shaken free, and along with impurities become part of the flat strips. Fibres that are deeply embedded in the flats, and cannot be reached by the cylinder wires become flat strips.

For this reason the closeness of the flats setting to the cylinder is important. Cylinder diameters vary and Karasev showed mathematically that for a given cylinder rotational speed the carding power will be greater for a larger cylinder diameter with a higher number of working flats. However, because of lower mechanical stresses, smaller cylinders can be rotated at higher speeds than larger cylinders.

The above advantage is therefore reduced the higher the speed of the smaller cylinder. If this occurs the tuftlets generally become the thick places in the yarn. It was found that high teeth densities and low cylinder speeds were as effective as lower teeth densities and high cylinder speed. High teeth densities with high cylinder speeds did not give effective carding, but no reason was reported for this. Since the action of the cylinder in this region is to individualise fibres, the wire clothing on the cylinder has a steeper rake and a higher point density than the wire clothing of the flats.

Thus, with closer settings and higher cylinder speeds greater forces may be involved and may result in fibre breakage. However, the work of Li indicates that the withdrawal forces needed to separate an entangled fibre mass was largely dependent on the density of the fibre mass and the contact angle fibres made with the wire clothing, than on the machine speeds. Van Alphen reports that increasing cylinder speed causes more fibre breakage than increasing taker-in speed and that this is reflected in the yarn properties.

The higher sensitivity of ring yarns to fibre breakage was attributed to the negative effect of short fibres during roller drafting. It may be reasoned that the smaller the tuftlets and the more parallel fibres in tuftlets are to the direction of mass flow the lower the probability of fibre breakage. For cottons, fibre breakage was only found to have occurred when the staple length was greater than 25mm.

Increasing the flat speed appears to have no effect on fibre breakage. However, the amount of flat strips increased proportionally with the flat speed and the mean fibre length of the strips increased significantly.

Interestingly, when carding cottons, immature fibres were not readily found in the flat strips. The coarser rigid fibres seem more easily retained by the flats. It is of interest therefore to consider how the Q2 is formed during fibre transfer from cylinder to doffer, and its importance to the card web quality. The regions above and below the line of closest approach of the cylinder to the doffer i.

The two regions may be termed the top and bottom co-operation arcs or top and bottom zones. Simpson claims that transfer can occur in both zones and that the particular region in which transfer actually occurs influences the fibre configuration and the nep level of the card web, although cylinder-flats action is more important in reducing neps. Although reference is made to other authors who have proposed a mechanism for fibre transfer in the top zone, no mechanism or experimental evidence is given to support the idea of fibre transfer in the bottom zone.

Lauber and Wulfhorst used laser-doppler anemometry and high-speed cine photography to study fibre behaviour in the bottom zone, i. Their findings showed no evidence of fibre transfer within the bottom zone. Although, the calendar draft can be used to change the relative proportions, Gosh and Bhaduri showed that the method of removing the web from the doffer does not influence the propensity of any class of configuration.

It is the mechanism of transfer that is seen as principally responsible for the shape fibres have in the sliver. Table 1: Classification of Fibre Configuration in Card Sliver Several studies have been reported on the fibre-mass-transfer mechanism. A number used tracer fibres with one end of a fibre dyed a different colour from the other.

The reported findings suggest that fibre mass transfer occurs by fibres acting independently and not as a web of fibres. On transfer the relative proportions changed as indicated in Table 2. On occasions transfer only happened when the cylinder speed was increased. Hodgson found that cotton fibres make between 10 and 25 cylinder revolutions before being removed by the doffer.

With the continuity of fibre mass flow through the card, this means that the doffer web is built up over many cylinder revolutions and that the recycling layer, Q2, is comprised of multiple fractional layers of the fibre mass transferred from taker-in to cylinder during these cylinder revolutions.

Here the trailing ends of fibres are lifted from the cylinder surface by centrifugal forces and become hooked around the teeth of the doffer clothing. The frictional drag of the doffer clothing eventually removes these fibre from the cylinder clothing.

This mechanism only explains the formation, without reversal, of trailing hooks in the doffer web. However, the importance to fibre transfer of the relative angles and tooth lengths of the cylinder and doffer is self evident from the figure.

Baturin developed equations that showed the importance of tooth angle and teeth density of the cylinder and doffer wires to the value of K and thereby Q2. It was found that the more acute the working angle of the doffer wire compared to the cylinder wire, the higher the value of K, and the lower Q2, and that higher teeth densities on the doffer increased K. These findings would tend to suggest that the proposed mechanism is a principal action by which fibres are removed from the cylinder.

However, this mechanism of fibre transfer does not explain the change of fibre configuration with reversals and the formation of leading hooks in the doffer web.

It also does not explain how fibres forming the recycling layer, Q2, are subsequently removed, even though an input layer of fibre mass is added to Q2 each time it passes the taker-in. The above studies did not take account of the degree of fibre parallelism on the cylinder prior to transfer, nor the number of fibres per tooth on the cylinder and consequently the likelihood of fibre interaction during transfer.

Fujino and Itani used a microscopic technique to observe the orientation of fibres on the cylinder surface above the taker-in and just before the doffer, and in the doffer web.

They found that fibres showed the highest degree of parallelism when on the cylinder surface just above the doffer. The degree of parallelism decreases on transfer to the doffer, and further deteriorates when the web is removed from the doffer to form the sliver, even though the calendar draft helps to maintain some degree of parallelism.

The action of the flats fitted above the doffer is not fully understood. It is assumed that they tend to lift the fibres to the tip of the cylinder wire for more effective transfer to the doffer, particularly at high cylinder speed. Lauber and Wolfhorst, Kamogawa report that in this region aerodynamic forces affect the parallelism of the fibres and the way they are transferred to the doffer.

However, no details are given. High-speed photographs showed that in the bottom zone the main flow of fibre mass was with the doffer at close to the doffer speed, even when the fibres were just below the cylinderdoffer setting line.

However, some fibres were seen to be free of both the doffer and cylinder and tended to move with the air currents and eventually with the motion of the cylinder surface. From the above discussion, it can be seen that work is still needed to establish a more detailed understanding of fibre mass transfer between the cylinder and doffer.

The results of such work may also help in better explaining how fibres remain on the cylinder to form the recycling layer Q2.

Varga suggests that with fibre transfer in the top zone, the thicker layer of web on the doffer surface protrudes above the doffer wire and into the gap setting between doffer and cylinder.

The faster moving cylinder wire clothing combs through the doffer web and thereby pulls fibres back onto the cylinder surface. De Swann showed that fibres can be readily transferred from the doffer to the cylinder as well as from cylinder to doffer. Sing and Swani developed a Markovian model for the carding process in order to determine the probabilities of fibre transfer between cylinder and flats and cylinder and doffer, taking into account the recycling of fibres.

Pf …………. Simpson suggests that fibre properties are also of importance, in that there is a tendency for low micronaire cottons to give higher cylinder loading and for fibres with low shear friction and good compression recovery to result in higher K values. No physical explanation is given for these findings and no other studies are reported on the effect of fibre properties. Further work is therefore needed in this area.

This would seem to imply that the higher the value of K the better the carding since less fibre mass is recycling to be added to the mass transferred from the taker-in. However, there are several ways of increasing K and not all of them result in improved carding quality. Figure 6, shows that for a given cylinder speed and sliver count, increased doffer speed increases K and reduces Pf , whereas keeping the doffer speed and sliver count constant and increasing the cylinder speed increase both K and Pf.

For constant cylinder and doffer speeds, increased sliver count was found to reduce K and Pf. If the same up stream machinery is used, then the best measure of effective carding is the quality of the carded ring-spun yarns produced.

Singh and Swani studied the properties of yarns made from slivers corresponding to differing K and Pf values and found that Pf was the more important of the two parameters, in that the higher the value of Pf the better the yarn quality. Kaufman reports that the lighter the fibre load is on the flats, the better the carding quality. Since this gives the number of times the recycling fibre mass is subjected to the carding action, it may be a better indication than Pf of the importance of Q2.

From the expression, Np decreases when K increases by increasing doffer speed. The last two parameters are usually taken as indicative of good carding.

Figure 8 shows the effect of increased doffer speed and sliver count on web quality and there is a consistent trend which suggests that increasing the production rate by increasing the sliver count, instead of doffer speed, gives better web quality. With regard to sliver irregularity, several investigators report theoretical and experimental studies showing that increasing the recycling layer, Q2, reduces the short-term irregularity.

Figure 8: Effect of Doffer Speed and Sliver Count on Web Quality Karasev attempted to show experimentally the importance of Q2 by removing it during carding using a suction extractor. It was found that without Q2 a large proportion of the fibre mass transferred from the takerin became embedded into the empty teeth of the cylinder clothing. Hence, there is a greater chance of small groups of entangled fibres being removed by the doffer. Q2 therefore acts as a support to new layers of fibre mass being transferred form the taker-in, keeping the new fibre mass at the tips of the cylinder wire teeth and thereby promoting the interaction of tuftlets with the flats and cylinder clothing.

This idea, however, does not facilitate an explanation of the mechanism by which fibres leave the recycling layer to form part of the doffer web, Q1. Gupta suggest that the rotating cylinder could be considered as a large centrifuge that would cause fibres, impurities and seed fragments to migrate to the cylinder periphery and thereby make contact with the flats clothing and, presumably, the doffer teeth.

However, no experimental verification of this hypothesis is reported. Many of the authors have reported the effect of machine variables on fibre configurations within the card sliver and several have related yarn properties to the observed configurations. Generally it was found that for a fixed sliver count increasing the carding rate by increasing the doffer speed, increased the number of minority hooks and reduced the number of majority hooks, irrespective of cylinder speed.

However, for a given doffer speed, increased cylinder speed gave the reverse trend for minority hooks, but no clear trend for majority hooks.

Baturin and Brown showed that increased cylinder speed decreases cylinder load owing to the effect of centrifugal forces and Simpson showed that increased cylinder speed also increased minority hooks and decreased majority hooks. Bhaudri reports that when the fibres are forced nearer the surface of the cylinder teeth, either by increasing the fibre load or increasing the centrifugal force on the cylinder, the proportion of minority hooks increases.

Simpson found that there was a direct relation between yarn imperfections and increased occurrence of minority hooks and that spinning end breakage rates and yarn imperfection increased with increased card production speed owing to minority hooks. Gosh and Simpson found that heavier slivers had fewer minority hooks. However, the increased draft needed to process the heavier slivers into yarn led to increased yarn imperfections. The taker-in action separates the fed fibre mass into tuftlets and individual fibres.

Although it is reported that the taker-in action gives a normal mass distribution of tuftlet sizes, this is speculation. Little research has been reported on the effect of taker-in parameters, fibre properties and the blowroom process on tuftlet size distribution and on the relative proportions of tuftlets to individual fibres.

The perceived benefits of combing segments built into the taker-in under-screen and of stationary flats fitted before and after the revolving flats are well known, but only limited experimental findings have been reported to support the use of these attachments. There are conflicting views on the benefits of triple taker-in systems, concerning whether the fibre opening by such systems would give a high misalignment of fibres to the direction of mass flow during transfer to the cylinder and degrade the subsequent carding action.

A better understanding is therefore required of the fibre mass transfer from taker-in to cylinder, since the surface speed ratio of these components is seen as a key factor in the proper functioning of high production cards. The cylinder-flats and cylinder-doffer interactions have been well researched.

Published findings show that each flat acquires two-thirds of its load at the beginning of its cycle of contact with the cylinder, and that separation of a given tuftlet occurs over a few flats. With regard to clothing parameters and cylinder speed, high teeth densities and lower cylinder speeds gave similar results to the converse arrangement. However, a high teeth density and cylinder speed did not give effective carding. Results showed that high cylinder speeds caused more fibre breakage than high taker-in speed.

A high cylinder to doffer speed reduces cylinder load, gives a higher K value and a better web quality. Increasing doffer speed was also found to increase K, but the web quality deteriorated. The reported mechanism of fibre transfer from cylinder to doffer does not adequately explain the effect of the cylinder— doffer speed ratio, or the various reported changes in fibre configuration during transfer.

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. Cylinder wire 2. Doffer wire 3. Flat tops 4. Licker-in wire 5. Tooth depth 7. Carding angle 8. Rib width 9. Wire height Tooth pitch 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. 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 betweent the free blade of two adjacent teeth it is difficult to remove it. 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 fibresM have different co- efficients of friction values which also determine the front angle of the wire. 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. 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. Lack of parallelisation, fibre damage, nep generation, more flat waste etc.

Each fibre has a linear density determined by its diameter to length ratio. Fine fibres and long fibres necessitate 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. 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.

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.

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. The general rule is higher populations for higher production rates, but it is not true always. It depends upon other factors like production rate, fineness, frictional properties etc.

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.

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. 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.

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. 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. For a given design of clothing the condition of the teeth determines the maximum acceptable production rate that can be achieved at 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.

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.

A standard doffer wire has an overall height of approx. Press Inquiries. Press Contact : Maria Aglietti. Email: aglietti mit. Phone: Caption :. Credits :.

A few examples of the teams are: Team Natural Futurism, which presented a concept to develop a biodegradable lifestyle shoe using natural material alternatives, including bacterial cellulose and mycelium, and advanced fiber concepts to avoid use of chemical dyes; Team CoMIT to Safety Before ProFIT, which explored the various ways that runners get hurt, sometimes from acute injuries but more often from overuse; Team Peacock, which prototyped athletic apparel with color-changing material to highlight an athlete's movement and quickly analyze motion through an app; Team Ecollab, which designed apparel and footwear using PE polyethylene and color changing material that is multifaceted and environmentally conscious; and Team Laboratory 56, which created footwear to enhance longevity of product and reduce waste using PE, while connecting with the community through a recycling app program.

Related Articles. Advancing industry convergence through technology and innovation. Inventing future fabrics. More MIT News. Pricing carbon, valuing people New research suggests ways to optimize US climate policy design for a just energy transition. Synthesis too slow? Let this robot do it.

Manchester, Lord, School of. The Institute Series on Textile Processing. Volume 1: Opening, Cleaning, and Picking,. Zoltan S. All further authors are textile industry experts, who among others in various positions within the Rieter Klein; 'The Technology of Short-staple.

Spinning'; The Textile Institute, Manual of. Textile Technology, Manchester Belicin ; 'Cotton yarn structure and methods of its formation'; MTI thesis,. Moscow Yarn Technology. Credit Value. Develop further understanding of 1 the principles of Klein, W. Series, The Textile Institute. Volume 1 — Technology of Short-staple Spinning. Volume 1. Sep 10, Calculation pertaining to draft and production of draw frame machine.

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