Moisture in atmosphere has a great impact on the physical properties of textile fibres and yarns.Relative humidity and temperature will decide the amount of moisture in the atmosphere. High relative humidity in different departments of spinning is not desirable. It will result in major problems. But on the other hand, a high degree of moisture improves the physical properties of yarn. Moreover it helps the yarn to attain the standard moisture regain value of the fibre. Yarns sold with lower moisture content than the standard value will result in monetary loss. Therefore the aim of CONDITIONING is to provide an economical device for supplying the necessary moisture in a short time, in order to achieve a lasting improvement in quality.
In these days there is a dramatic change in the production level of weaving and knitting machines, because of the sophisticated manufacturing techniques. Yarn quality required to run on these machines is extremely high. In order to satisfy these demands without altering the raw material, it was decided to make use of the physical properties inherent in the cotton fibres. Cotton fibre is hygroscopic material and has the ability to absorb water in the form of steam. It is quite evident that the hygroscopic property of cotton fibres depends on the relative humidity. The higher the humidity, more the moisture absorption. The increase in the relative atmospheric humidity causes a rise in the moisture content of the cotton fibre, following an S-shaped curve.
The relative humidity in turn affects the properties of the fibre via the moisture content of the cotton fibre. The fibre strength and elasticity increase proportionately with the increase in humidity. If the water content of the cotton fibre is increased the fibre is able to swell, resulting in increased fibre to fibre friction in the twisted yarn structure. This positive alteration in the properties of the fibre will again have a positive effect on the strength and elasticity of the yarn.
CONTEXXOR CONDITIONING PROCESS BY XORELLA:
The standard conventional steaming treatment for yarn is chiefly used for twist setting to avoid snarling in further processing. It does not result in lasting improvement in yarn quality. The steaming process may fail to ensure even distribution of the moisture, especially on cross-wound bobbins(cheeses) with medium to high compactness. The thermal conditioning process of the yarn according to the CONTEXXOR process developed by XORELLA is a new type of system for supplying the yarn package.
The absence of Vacuum in conventional conditioning chambers, prevents homogeneous penetration. The outer layers of the package are also too moist and the transition from moist to dry yarn gives rise to substantial variations in downstream processing of the package, both with regard to friction data and strength.
Since the moisture is applied superficially in the wet steam zone or by misting with water jets, it has a tendency to become re-adjusted immediately to the ambient humidity level owing to the large surface area. Equipment of this king also prevents the optimum flow of goods and takes up too much space.
PRINCIPLE OF WORKING:
Thermal conditioning uses low-temperature saturated steam in vacuum. With the vacuum principle and indirect steam, the yarn is treated very gently in an absolutely saturated steam atmosphere. The vacuum first removes the air pockets from the yarn package to ensure accelerated steam penetration and also removes the atmospheric oxygen in order to prevent oxidation. The conditioning process makes use of the physical properties of saturated steam or wet steam (100% moisture in gas-state). The yarn is uniformly moistened by the gas. The great advantage of this process is that the moisture in the form of gas is very finely distributed throughout the yarn package and does not cling to the yarn in the form of drops. This is achieved in any cross-wound bobbins, whether the yarn packages are packed on open pallets or in cardboard boxes.
pic: XORELLA CONDITIONING SYSTEM
ADVANTAGES OF CONTEXXOR PROCESS:
saturated steam throughout the process
even penetration of steam and distribution of moister
absolute saturated steam atmosphere of 50 degree C to 150 degreees C.
no additional boiler required, the steam is generated in the system
minimum energy consumption(approx. 25 KWh for 1000 kgs of yarn)No tube buckling in case of mad-made yarns
treatment of all natural yarns, blends, synthetics and microfibre yarns.
low installation and maintenance cost
preheating for trollys and plastic tubes to avoid drops (Wool)
length up to 20 meters (66 feet) and max. temperature deviation of 1°C
various loading and unloading facilities
no contamination of the treated packages
energy recovery option offered by indirect heating system using steam or hot water
no special location required, the systems can be operated next to the production machines.
BENEFITS ACHIEVED OUT OF CONDITIONING:
The treatment temperature for knitting yarn is held below the melting point of the wax. Temperatures for unwaxed
yarn are coordinated to the compatibility fo each individual type of yarn
Upto 20% greater efficiency due to a reduction in the unwinding tension
fewer needle breaks
uniform moisture content and friction values
regular stitch formation
no change in size of finished articles
no extra dampening required
free from electrostatic
less fly hence less problems. It helps if the yarn is running on a closer gauge machines
NOTE: Please note that the wax applied should be able to withstand min 60 degree centigrade. If low quality wax is used, it will result in major problem. Conditioning should be done at 55 to 60 degree centigrade.
upto 15% fewer yarn breaks due to greater elongation
less fly, resulting in a better weaving quality
increased take-up of size, enhanced level of efficiency in the weaving plant
Pic: improved strength Pic: improved elongation
Conditioning and fixing of the twist at the same time in a single process.
better dye affinity
Pic: dye pick up of conditioned and unconditioned yarn
Roving machine is complicated, liable to faults, causes defects, adds to production costs and delivers a product that is sensitive in both winding and unwinding. This machine is forced to use by the spinner for the following two reasons.
Sliver is thick, untwisted strand that tends to be hairy and to create fly. The draft needed to convert this is around 300 to 500. Drafting arrangements of ring frames are not capable of processing
this strand in a single drafting operation to create a yarn that meets all the normal demands on such yarns.
Drawframe cans represent the worst conceivable mode of transport and presentation of feed material to the ring spinning frame.
· Fibre to fibre cohesion is less for combed slivers. Rollers in the creel can easily create false drafts.Care must be taken to ensure that the slivers are passed to the drafting arrangement without disturbance.
Therefore, a perfect drive to the creel rollers is very important.
· The drafting arrangement drafts the material with a draft between 5 and 15.The delivered strand is too thin to hold itself together at the exit of the front bottom roller.
· Bobbin and flyer are driven separately, so that winding of the twisted strand is carried out by running the bobbin at a higher peripheral speed than the flyer.
· The bobbin rail is moving up and down continuously, so that the coils must be wound closely and parallel to one another to ensure that as much as material is wound on the bobbin.
· Since the diameter of the packages increases with each layer, the length of the roving per coil also will increase. Therefore the speed of movement of bobbin rail must be reduced by a small amount after
each completed layer
· Length delivered by the front roller is always constant. Owing to the increase in the diameter of the package for every up and down movement, the peripheral speed of package should keep on changing , to maintain the same difference in peripheral speeds between package and flyer.
· There are two types of drafting systems.
3/3 drafting system
4/4 drafting system
In general 3/3 drafting system is used, but for higher draft applications 4/4 drafting system is used.
· The draft often has limits not only at the upper limit (15 to 20), but also at lower limit. It is around 5 for cotton and 6 for synthetic fibers. If drafts below these lower limits are attempted, then the fibre masses to be moved are too large, the drafting resistance becomes too high and the drafting operation is difficult to control.
It is advisable to keep the break draft (predarft) as low as possible, because lower break draft always improves roving evenness.
· In general two condensers are used in the drafting arrangement. The purpose of these condensers is to bring the fibre strands together. It is difficult to control, Spread fibre masses in the drafting zone and they cause unevenness. In addion, a widely spread strand leaving the drafting arrangement leads to high fly levels and to high hairiness in the roving. The size of condensers should be selected according to the volume of the fibre sliver.
· Flyer inserts twist. Each flyer rotation creates one turn in the roving. Twist per unit length of roving depends upon the delivery rate.
Turns per metre = (flyer rpm)/(delivery speed (m/min))
Higher levels of roving twist, therefore, always represent production losses in Roving frame and possible draft problems in the ring spinning machine. But very low twist levels will cause false drafts and roving breaks in the roving frame.
· Centrifugal tension is created at the bobbin surface as the layers are being wound and is created by the rotation of the package. Each coil of roving can be considered as a high-speed rotating hool of roving on which centrifugal tension increases with increasing diameter of the package. centrifugal tension in the roving is proportional to the square of the winding surface velocity.In this context, centrifugal force acts in such a manner as to lift the top roving strand from the surface of the package so that the radial forces within the strand that hold the fibres together are reduced and the roving can be stressed to the point of rupture. Breaks of this type may occur at the winding-on Point of the presser or in strands that have just been wound on the top surface of the package. This phenomenon is known as “bobbin-bursting”. This phenomenon will be prominent if the twist per inch is less or the spindle speed is extremely high when the bobbin is big.
· Apart from inserting twist, the flyer has to lead the very sensitive strand from the flyer top to the package without introducing false drafts. Latest flyers have a very smooth guide tube set into one flyer leg
and the other flyer leg serves to balance the flyer. The strand is completely protected against air flows and the roving is no longer pressed with considerable force against the metal of the leg, as it is in
the previous designs. Frictional resistance is considerably reduced, so that the strand can be pulled through with much less force.
· False twisters are used on the flyers to add false twist when the roving is being twisted between the front roller and the flyer.Because of this additional twist, the roving is strongly twisted and this reduces the breakage rate. Spinning triangle is also reduced which will reduce the fibre fly and lap formation on
the front bottom roller.
· Because of the false twister, the roving becomes compact which helps to increase the length wound on the bobbin. This compactness helps to increase the flyer speed also.
· Roving strength is a major factor in determining winding limitations. It must be high enough for the fibres to hold together in a cohesive strand and low enough for satisfactory drafting at the spinning machine. The factors affecting roving strength are as follows:
the length, fineness, and parallelisation of fibres
the amount of twist and compactness of the roving
the uniformity of twist and linear density.
· BUILDER MOTION: This device has to perform the following tasks
to shift the belt according to the bobbin diameter increase
to reverse the bobbin rail direction at top and bottom
to shorten the lift after each layer to form tapered ends
· Shifting of the belt is under the control of the ratchet wheel. The ratchet wheel is permitted to rotate by a half tooth. The bobbin diameter increases more or less rapidly depending upon roving hank. The belt must be shifted through corresponding steps. The amount of shifting, which depends upon the thickness of the roving, is modified by replacement of the ratchet wheel or by other gears.If a ratchet wheel with fewer teeth is inserted, then the belt is shifted through larger steps, i.e. it moves more rapidly, and vice versa.
· To form a package, the layer must be laid next to its neighbours. For that the lay-on point must continually be moved. The shift of the winding point is effected by moving the bobbin rail. This raising and lowering is done by rails.Since the package diameter is steadily increasing, the lift speed must be reduced by a small amount after each completed layer.
· During winding of a package, the ratchet is rotated at every change-over.Reversal of the bobbin layer occurs little earlier for every reversal.This gives a continuous reduction in the lift of the rail . Thus bobbins are built with taper.
In most cases, the limit to productivity of the ring spinning machine is defined by the traveller in interdependence with the ring, and yarn. It is very important for the technologist to understand this and act on them to optimise the yarn production.
Traveller imparts twist to the yarn. Traveller and spindle together help to wind the yarn on the bobbin. Length wound up on the bobbin corresponds to the difference in peripheral speeds of the spindle and traveller. The difference in speed should correspond to length delivered at the front rollers. Since traveller does not have a drive on its own but is dragged along behind by the spindle.
High contact pressure (upto 35 N/square mm)is generated between the ring and the traveller during winding, mainly due to centrifugal force. This pressure leads to generation of heat. Low mass of the traveller does not permit dissipation of the generated heat in the short time available. As a result the operating speed of the traveller is limited.
Heat produced when by the ring traveller is around 300 degree Celsius. This has to be dissipated in milliseconds by traveller into the air.
Parts of a traveller:
Height of bow: It should be as low as possible for stable running of traveller. It should also have sufficient yarn passage.
Yarn passage: According to count spun the traveller profile to be selected with required yarn passage.
Toe gap : This will vary according to traveller number and flange width of the ring
Wire section: It plays an important role for yarn quality, life of traveller.
Ring contact area: This area should be more, uniform, smooth and continuous for best performance.
Inner width: This varies according to traveller profile and ring flange.
SALIENT FEATURES OF A TRAVELLER:
Generate less heat
dissipate heat fastly
have sufficient elasticity for easy insertion and to retain its original shape after insertion
friction between ring and traveller should be minimal
it should have excellent wear resistance for longer life
hardness of the traveller should be less than the ring
When the spindle speed is increased, the friction work between ring and traveller (hence the build up) increases as the 3rd power of the spindle rpm. Consequently if the spindle speed is too high, the traveller sustains thermal damage and fails. This speed restriction is felt particularly when spinning cotton yarns of relatively high strength.
If the traveller speed is raised beyond normal levels , the thermal stress limit of the traveller is exceeded, a drastic change in the wear behaviour of the ring and traveller ensues. Owing to the strongly increased adhesion forces between ring and traveller, welding takes place between the two. These seizures inflict massive damage not only to the traveller but to the ring as well.Due to this unstable behaviour of the ring
and traveller system the wear is atleast an order of magnitude higher than during the stable phase. The traveller temperature reaches 400 to 500 degrees celcius and the danger of the traveller annealing and failing is very great.
The spinning tension is proportional
to the friction coefficient between ring and traveller
to the traveller mass
to the square of the traveller speed
and inversely proportional
to the ring diameter
and the angle between the connecting line from the traveller-spindle axis to the piece of yarn between the traveller and cop.
In order to maintain the same friction or spinning tension with different coefficients of friction, different traveller weights must be used. The coefficient of friction is determined by the fiber lubrication and is subject to fluctuation. Dry cotton means higher coefficient of friction. For manmade fibres depending upon the manufacturer, lower to medium coefficient of friction.
The coefficient of friction with fiber lubrication can vary from 0.03 and 0.15.
R = Coefficient of friction x N
R – traveller friction in mN
N = Normal force >= (Fc x ML x V xV)/(R)
Fc – centrifugal force
ML – mass of the traveller in mg
V – traveller speed in m/s
R – radius of the ring (inside)
The yarn strength is affected only little by the spinning tension. On the other hand the elongation diminishes with increasing tension, for every tensile load of the fibres lessens the residual elongation in the fibres and hence in the yarn. Increasing tension leads also to poorer Uster regularity and IPI values.
If the spinning tension is more, the spinning triangle becomes smaller . As the spinning triangle gets smaller, there is less hairiness.
SHAPE OF THE TRAVELLER:
The traveller must be shaped to match exactly with the ring in the contact zone, so that a single contact surface, with the maximum surface area is created between ring and traveller. The bow of the traveller should be as flat as possible, in order to keep the centre of gravity low and thereby improve smoothness of running. However the flat bow must still leave adequate space for passage of the yarn. If the yarn clearance opening is too small, rubbing of the yarn on the ring leads to roughening of the yarn,
a high level of fibre loss as fly, deterioration of yarn quality and formation of melt spots in spinning of synthetic fibre yarns.
WIRE PROFILE OF THE TRAVELLER:
Wire profile influences both the behaviour of the traveller and certain yarn characteristics, they are
contact surface of the ring
yarn clearance opening
MATERIAL OF THE TRAVELLER
The traveller should
generate as little heat as possible
quickly distribute the generated heat from the area where it develops over the whole volume of the traveller
transfer this heat rapidly to the ring and the air
be elastic, so that the traveller will not break as it is pushed on to the ring
exhibit high wear resistance
be less hard than the ring, because the traveller must wear out in use in preference to the ring
In view of the above said requirements, traveller manufacturers have made efforts to improve the running properties by surface treatment. “Braecker” has developed a new process in which certain finishing components diffuse into the traveller surface and are fixed in place there. The resulting layer reduces temperature rise and increases wear resistance.
Traveller mass determines the magnitude of frictional forces between the traveller and the ring, and these in turn determine the winding and balloon tension. Mass of the traveller depends upon
material being spun
If traveller weight is too low, the bobbin becomes too soft and the cop content will be low. If it is unduly high, yarn tension will go up and will result in end breaks. If a choice is available between two traveller weights, then the heavier is normally selected, since it will give greater cop weight, smoother running of the traveller and better transfer of heat out of traveller.
When the yarn runs through the traveller, some fibres are liberated. Most of these fibres float away as dust in to the atmosphere, but some remain caught on the traveller and they can accumulate and form a tuft. This will increase the mass of traveller and will result in end break because of higher yarn tension. To avoid this accumulation , traveller clearers are fixed close to the ring, so that the accumulation is prevented. They should be set as close as possible to the traveller, but without affecting its movement. Exact setting is very important.
For the rings two dimensions are of primarily importance. 1.internal diameter 2. flange width.
Antiwedge rings exhibit an enlarged flange inner side and is markedly flattened on it upper surface. This type of profile permitted to use travellers with a lower centre of gravity and precisely adapted bow(elliptical travellers), which in turn helped to run the machine with higher spindle speeds. Antiwedge rings and elliptical travellers belong together and can be used in combination.
Low crown profile has the following advantage. Low crown ring has a flattened surface top and this gives space for the passage of the yarn so that the curvature of the traveller can also be reduced and the centre of gravity is lowered.In comparison with antiwedge ring, the low crown ring has the advantage that the space provided for passage of the yarn is somewhat larger and that all current traveller shapes can be applied, with the exception of the elliptical traveller. The low crown ring is the most widely used ring form now.
The ring should be tough and hard on its exterior. The running surface must have high and even hardeness in the range 800-850 vikcers. The traveller hardness should be lower (650-700 vickers), so that wear occurs mainly on the traveller, which is cheaper and easier to replace. Surface smoothness should be high, but not too high, because lubricating film can not build up if it too smooth.
A good ring in operation should have the following features:
best quality raw material
good, but not too high, surface smoothness
an even surface
good, even surface hardness, higher than that of the traveller
should have been run in as per ring manufacturers requirement
long operating life
correct relationship between ring and bobbin tube diameters
perfectly horizontal position
it should be exactly centred relative to the spindle
In reality, the traveller moves on a lubricating film which builds up itself and which consists primarily of cellulose and wax. This material arises from material abraded from the fibres.If fibre particles are caught between the ring and traveller, then at high traveller speeds and with correspondingly high centrifugal forces, the particles are partially ground to a paste of small, colourless, transparent and extremely thin platelets.
The platelets are continually being replaced during working. The traveller smoothed these out to form a continuous running surface.The position, form and structure of lubricating film depends on
fibre raw material
high of traveller bow
Modern ring and traveller combination with good fibre lubrication enable traveller speeds upto 40m/sec.
When the ring diameter is less, balloon diameter will be small. This leads to more yarn tension. Hence use lighter travellers.
When the ring diameter is bigger, balloon diameter will be more. This leads to less yarn tension and the balloon touches the separator. Hence use heavier travellers
When the tube length is short, the yarn tension will be more. Hence use lighter travellers
When the tube length is long, the yarn tension will be less, hence use heavier travellers
When the yarn contact area and ring contact area in traveller is closer, fibre lubrication is better especially in cotton. For this use heavier travellers
When spindle speed is increased use lighter traveller with low bow height. At higher speeds, lighter travellers give lesser yarn tension. When low bow height travellers are used centre of gravity will be closest to the ring which aids in running of traveller.
Use lighter travellers on new rings. This is done to reduce end breakages by reducing the yarn tension.
Use heavier travellers on old rings. This is done to avoid bigger balloons
Heavier travellers reduce hairiness
When using lighter travellers, yarn stretch will be less. It helps for better yarn elongation
During running-in the end breakage rate should be kept minimum, hence use lighter travellers.
The shorter the balloon, the lighter the traveller to be used, the higher traveller speeds can be achieved.
The ring traveller, together with the yarn as a pull element, is set into motion on the ring by the rotation of the spindle. If the direction of pull deviates too much from the running direction of the traveller (spinning angle less than 30 degrees) the tension load will be too high.
Preconditions for good operating results
The maximum ability of the ring/traveller system to withstand occurring stress situation during operation determines the performance limit of the ring spinning and twisting machine. Traveller wear does not only depend on traveller material; problems of heat dissipation are of crucial importance, too. The heat generated between ring and traveller must be reduced as quickly as possible to avoid local temperature in the traveller wear zones. The ability of the traveller to resist to stress is determined by several factors. Investigations regarding improvements of rings and travellers aimed at a further increase of performance should above all make sure that all other conditions with a certain influence on the spinning process are optimal.
Therefore make sure that:
¥ the rings are correctly centered with regard to the spindles
¥ the yarn guide eyelet is well centered with regard to the spindle
¥ the spindle bearing is in good condition, thus preventing spindle vibrations
¥ the ratio between bobbin diameter and ring diameter is correct
¥ the concentricity of the ballon control ring with regard to the
spindle is correct
¥ the fibre tufts which accumulate on flange travellers are removed by
means of suitable traveller cleaners
¥ the climatic conditions (temperature and relative air humidity) are favourable
for the spinning process
¥ the air in the mill is free from disturbing particles that influence efficient
performance of the traveller
It has to be stressed that a smooth and well run-in track is of most importance.
Concentricity of spindle, ring, yarn guide and balloon control ring
Especially at high spindle speeds concentric positioning of ring, spindle, yarn eyelet and balloon control ring is required for keeping the ends down rate at low level. Spindles and rings must be aligned and centered absolutely parallel. Ring rails or ring holders should, therefore, be installed absolutely horizontally compared to the vertically fitted spindles. Ring and traveller form the main elements in ring spinning and twisting. They determine to a large extent performance and operating conditions of the machine.
The traveller accomplishes two main tasks while running on the ring at high speeds:
a) It gives the roving supplied by the feed rollers the necessary twist.
b) It assists in winding the yarn onto the bobbin in the form of a cop with ã correct tension.
During this operation the ring guides the traveller, which is essential for the perfect positioning of the yarn and the formation of the cop. The traveller is pressed against the ring track by centrifugal forces. The resulting frictional forces reduce traveller speed, which is dragged along by the passing-through yarn, and provide the yarn with the tensile forces necessary for assembling the individual fibres into the spun yarn as well as for limiting the yarn balloon.
Steel travellers are hardened to a certain degree and polished to a mirror finish. They can be adapted in shape, weight and surface finish to the ring, yarn type and yarn count. Nylon travellers of standard quality (for HZ and J rings) are made of highly wear-resistant polyamide. Extremely aggressive yarns are processed with glass-fibre-reinforced a Super Nylon travellers. Twisting and winding carried out by the traveller must be performed with appropriate yarn tension. The ratio between spindle speed and the speed at which the yarn is supplied determines yarn twist. Any change of this ratio is easily compensated by the traveller without having an influence on twisting, winding and tensioning.
On flange rings, the gliding speed of travellers having a suitable shape can be as rapid as 130 ft/s (88 MPH) or 40 m/s (140 km/h); on DIA-DUR coated rings the speed can to some extent reach 147 ft/s (100 MPH) or 45 m/s (160 km/h) . Having an average life span of 200-300 operating hours the traveller covers a distance of more than 18.000 miles (30.000 km) – a tremendous task for a small part of wire weighing only a few milligrams. These standards can even be surpassed by nylon travellers used on HZ rings, if operating conditions are favourable.
These high traveller speeds involve pressures of up to 35 N/mm 2 . But even if high-quality materials with an optimum of hardness and resistance to wear are used, these standards can only be reached if
¥ in the case of flange rings, a film of lubricating fibres is produced continuously,
¥ in the case of HZ and J rings, a sufficient amount of lubricant is consistently
d 1 = spinning ring diameter
d 2 = fitting diameter
h 1 = ring height
h 2 = ring height above ring rail
b = flange width
flange 1 = 3.2 mm
flange 2 = 4.1 mm
Spindles operating without vibrations contribute a great deal to a smooth operation of the traveller. Non-concentric spindles and spindles not running smoothly cause constant changes in yarn tension , because the traveller cannot run around the ring without being shaken.
Vibration-free movements of ring rail and ring holder
The ring rail should move smoothly without jerking. Vibrations and hard jolts at the reversing points of the ring rail disturb the operation of the traveller. Repeated changes in yarn tension cause the traveller to flutter. This results in increasing yarn breaks and in accelerated wear of ring and traveller.
Correct ratio between bobbin diameter, bobbin length, ring diameter and spindle gauge
Ratio bobbin length (H) : Inside ring diameter (D)
Thread tension increases with growing bobbin length. In view of the limited thread tension, the total bobbin length should not exceed 5 times the ring diameter. Only when using balloon control rings or similar devices this value can be exceeded.
H : D = 5 : 1
Ratio bobbin diameter (d) : Inside ring diameter (D)
The bobbin diameter d is equivalent to the mean outer bobbin diameter d 1 + d 2
The following values are recommended:
for spinning: d : D = 0.48 – 0.5 (a = 29°-30°), (minimum value a = 26°)
for twisting d : D = 0.44 – 0.5 (a = 27°-30°), (minimum value a = 22°)
For light and heavy bobbins, the values for light bobbin types are decisive for calculating d : D. If the ratio d : D is reduced thread tension increases.
Correct surface smoothness, i.e. optimum peak-to-valley height and evenness of the ring track
The traveller contact surfaces must be smooth and even. Only then a smooth operation of the traveller will be possible. The contacted surfaces should be clean and preferably without traces of wear. In addition, they should be designed in such a way that they offer sufficient adherence for potential lubricants (e.g. fibres, oil, grease).
Once the sliding surfaces have lost their original quality, even the best ring traveller will not be able to run smoothly. For maintaining the surface of the running track in a good condition, it is very important – besides a certain degree of maintenance – to run the ring well in.
Balloon control rings and separators
The influence of balloon control rings is quite considerable, especially at long cops. A reduction of the yarn balloon is advantageous or may even be the prerequisite for optimum performance. If balloon control rings are mounted at correct distance (the yarn balloon should be restricted as long as possible during one lift of the ring rail) then a marked performance increase is possible. The balloon control rings are removed when sensitive materials are processed and sufficiently long separators are installed to avoid many yarn breaks and to prevent fibre fly from accumulating on the adjacent spindles.
Traveller cleaners are an excellent method for removing all fibre fly that accumulates on the outer part of C and El travellers. The traveller cleaner should have the right distance to the outside ring flange. A distance of about 0.5 mm between cleaner and traveller (in operating position) is recommended. When adjusting the distance between outside ring flange and cleaner, the size of the traveller should be taken into consideration.
Constant temperature and air humidity have positive effects on the operation of the traveller. Changes of the room climate, such as raised air humidity will increase wear by friction. Besides the regular exchange of air, the purity of the air is of great importance for the traveller. Any dust (also dust from unsuitable floors) or other impurities may impair traveller operation and lead to more ring/traveller wear.
Flange width and ring height
Optimal operating results are reached when the ideal flange width is chosen for flange rings and the ideal ring height is obtained for self-lubricating HZ and J rings, dependent on yarn count range, yarn quality and traveller type.
Ring profile and traveller shape
Determining the most favourable ring and traveller shapes is a precondition for obtaining the optimal individual performance. If ring profile and traveller shape match well, the traveller will adopt a stable position in the ring. It should have sufficient tolerance of movement, so that any obstacles which may occur especially when the machine is started are avoided. A satisfactory large yarn clearance counteracts yarn breaks and yarn damage.
Running-in of rings
Normally the running-in procedure is decisive for the future positive/nega tive behaviour of the ring and the length of its service life. Every ring requires a certain degree of running-in time if it is to maintain high traveller speeds with as little ring and traveller wear as possible. During running-in the use of steel travellers without surface treatment is recommended. After the termination of the running-in process, steel travellers with surface treatment or nylon as well as bronze travellers can be used.
The running-in process, beginning with the starting phase, consists of improving the initial running properties of the metallic running surface up to the optimal values by smoothing and passivation(oxidation) as soon as possible. In this way, together with fibre lubrication, constant minimum mixed friction conditions and minimum thermal stressing can be attained for the ring traveller. A careful running-in process will improve the lifetime of the rings.
In order to keep the stress on the traveller as low as possible during the starting phase, it is advisable to always change the traveller in the upper third part of the cops. Further advantages are brought with the use of a traveller running-in program(reduction of the speed by about 10% for 10 to 20 minutes, only available on modern spinning machines).
Spindle speed should be reduced at least for the first 10 traveller changes. If final speed is higher than 32m/sec, reduce by atleast 20%. If final speed is lower than 32m/sec, reduce by at least 10%.
New rings should not be degreased, but only rubbed over with a dry cloth.
In general, the running in should be done with the same traveller type which is used for normal operation with the 10 to 20% less than normal speed. It is not advisable to do running with the same speed but with 1to 2 numbers lighter travellers than usual.
The first traveller change should be carried out after 15 min
The second traveller change should take place after 30 min
The third traveller change should be made after 1 to 1.5 hours.
The fourth traveller change should be made after the first doff.
Further traveller changes are to be made according to the manufacturers recommendations
HAIRINESS: Following are the reasons for higher yarn hairiness due to ring and travellers
Poorly cantered spindles, anti balloon rings and yarn guides lead to inconsistent yarn tension.
Rough surfaces roughen the yarn(due to damaged parts)
Open anti balloon ring
The clearance between ring and cop should not be too small. Traveller will cut the fibres protruding from the cop.
the fibres get electrostatically charged
poor twist propagation to the spinning triangle due to lighter travellers
Heavy friction of the balloon on the anti-balloon ring respectively impact on the balloon separator( due to lighter traveller)
Poor ring cantering
yarn getting roughened in narrow yarn passage in the traveller
scratched up yarn passages catch the yarn and roughen it (due to very high traveller running time)
friction of the yarn due to very high traveller weight
rough gliding surface of the ring ( due to worn out rings)
With the ComforSpin technology a new yarn with perfect yarn structure – the COM4 yarn – has been established in the market. With the help of a microscope the structure of the yarns can easily be compared: The conventional ring yarn shows to be far less perfect than commonly assumed. The long, protruding fibres cause a number of problems in downstream processing. COM4 yarn shows a very compact structure with highly parallel fibres and much less disturbing hairiness.
The air current created by the vacuum generated in the perforated drum condenses the fibres after the main draft. The fibres are fully controlled all the way from the nipping line after the drafting zone to the pinning triangle.
An additional nip roller prevents the twist from being propagated into the condensing zone. The compacting efficiency in the condensing zone is enhanced by a specially designed and patented air guide element.
Optimal interaction of the compacting elements ensures complete condensation of all fibres. This results in the typical COM4 ® yarn characteristics.
The ComforSpin ® technology allows aero-dynamic parallelization and condensation of the fibres after the main draft. The spinning triangle is thus reduced to a minimum. The heart of ComforSpin machine is the compacting zone, consisting of the following elements:
The directly driven perforated drum is hard to wear and resistant to fibre clinging. Inside each drum there is an exchangeable stationary suction insert with a specially shaped slot. It is connected to the machine’s suction system.
The operating method of the SUESSEN EliTe Spinning System is well-known.After the fibres leave the drafting system they are condensed by an air-permeable lattice apron,which slides over an inclined suction slot.The fibres follow the outer edge of this suction slot and at the same time they perform a lateral rolling motion.
Above the front bottom roller of the drafting system,the fibre band influenced by high draft is spreading.In the area of the suction slot,which is covered by the lattice apron,the fibre band is condensed.Commencing from the semi-dotted clamping line of the EliTe Q Top Roller,twist is being inserted.There is no spinning triangle.
The improvement achieved is shown in Fig .The left side displays the fibre triangle at the exit of a conventional ring frame drafting system.The twist imparted by the spindle cannot flow up to the clamping line.The outer fibres spread out and are thus more highly tensioned than those on the inside. The right side of the picture does not show a spinning triangle.The yarn twist flows right up to the clamping line.The yarn is round and smooth.
Since the spinning triangle is very very small, the end breaks will be very less and therefore the fly liberation will also be less.
Condensing of the fibre bundle,which follows the drafting process,can already be seen as a significant development of the ring spinning technology.Condensed ring yarn is more than a speciality.In view of its manifold advantages.
It is of technological importance that the suction level relevant for the condensing operation is exactly the same for all spinning positions. To fulfil this criteria,individual motors combined with suction units for 6 spinning positions,have been arranged accordingly.This provides short air-flow distances with identical negative pressures at all spinning points .
During yarn formation all fibres are perfectly condensed and gathered parallel to each other in the compacting zone. Consequently all fibres are twisted in and contributing to the superior fibre utilisation rate compared to conventional ring yarn. The result is exceptionally low hairiness combined with higher yarn tenacity and elongation. These are the unique characteristics of these yarns.
ADVANTAGES OF COMPACT YARN:
• higher fibre utilisation
• higher tenacity with same twist factor, or
• same tenacity with reduced twist factor for higher production
• lowest hairiness (highest reduction in hairs longer than 3 mm)
• fewer weak points
• better imperfections (IPI) values
• higher abrasion resistance
• greater brilliance of colour
• intensive dye penetration
• no singeing before printing
Due to better utilization of fibre substance it is possible to reduce yarn twist of these Yarns,particularly of knitting yarns,by up to 20%,maintaining the yarn strength of conventional ring yarns.This increases yarn production. The ends-down rate in spinning these Yarns is reduced by 30 to 60%,which improves machine efficiency.
Applying the same winding speed as with conventional ring yarns,there are less raised points in these Yarns and the increase in yarn imperfections is reduced because they have a better resistance to shifting. Higher winding speeds are therefore possible with compact yarns Yar ns .
In accordance with up to 20%twist reduction in spinning compact yarns ,the twisting turns can be reduced for certain types of yarn.As a result,production of twisting frame is increased and twisting costs are reduced.
Owing to the lower hairiness and higher tenacity of compact Yarns,the ends-down rate in beaming is reduced by up to 30%.Higher beamer efficiency,higher produc tion and fewer personnel for repair of ends-down in beaming are the consequence.
Compact Warp yarns help to save up to 50%of sizing agent,while the running behaviour of weaving machi-nes is the same or even better. Cost can be saved in sizing and desizing processes.
Owing to the better work capacity of compact Yarns ,ends down can decreased by up to 50% in the warp and by up to 30%in the weft. Efficiency is consequently increased by 2 to 3%, production is increased and weaving costs are reduced. In practice,the average ends-down rate is reduced by 33% per 100,000 weft insertions of compact Yarns on rapier weaving machines and by 45% on air-jet weaving machines. Instead of a weft insertion of 500 –600 m/min with conventional ring yarn,700-800 m/min is possible with compact Yarns on air-jet weaving machines.
Due to reduced Yarn hairiness,singeing can sometimes be dispensed with,or it can be carried out at a higher cloth advance speed.As a result,production costs are considerably reduced.
fibres upto 7% can be saved because singing can be avoided
Dyeing and Printing Improved structure of compact Yarns and their reduced twist favours the absorption of colour pigments and chemical finishing agents.Saving of dyestuff is possible.
Owing to the improved yarn strength, compact Yarns are well suited for non-iron treatment of woven fabrics. In the course of such treatment,the strength of fabrics made from conventional ring yarns can decrease by up to 25%,with frequent problems in the manufacture of clothes. compcat Yarns make up for this loss in strength.
Knitting :Compact Yarns with their increased yarn strength and reduced formation of fluff permit to achieve higher machine efficiency and therefore production on knitting machines at a reduced ends-down rate,less interruptions and less fabric faults. Production costs therefore decrease. The enormously low hairiness of compact Yarns often permits to dispense with usual waxing. Considerable cost saving is achieved because of this.
In knitting fibre abrasion reduced by 40% due to low hairiness. Fewer defects/ yarn breaks and better quality. Less contamination on all machines by foreign fibres . Less wear of needles, guide elements and sinkers due to less dust in the compact Yarn . Low hairiness has positive impact on loop structure . L Low pilling values get more and more important . In many cases single compact Yarns substitute conventional ply yarns. Waxing can be reduced or completely dispensed with .
Compact Yarns are much more suitable for warp knitting than conventional ring yarns,because of their higher work capacity and lower hairiness. They are predestined to bear the high load due to numerous deflecting points with high friction in the warp knitting machine.
Due to better embedding of fibres (including short ones)in compact Yarn,approx.6%fewer combing noils are possible.
Cheaper carded qualities instead of combed qualities can be spun with the Compact Spinning ystem.
in many cases single EliTe ® Yarns can substitute conventional ply yarns
new qualities can be developed, opening up a new creative scope for products
Hairiness Testing of Yarns
Hairiness of yarns has been discussed for many years,but it always remained a fuzzy subject. With the advent of compact yarns and their low hairiness compared to conventional yarns,the issue of measuring hairiness and the proper interpretation of the values has become important again.Generally speaking,long hairs are undesirable, while short hairs are desirable (see picture ). The picture shown below just give a visual impression of undesirable and desirable hairiness at the edge of a cops.
RING YARN COMPACT YARN
There are two major manufacturers of hairiness testing equipment on the market,and both have their advantages and disadvantages. Some detail is given below.
USTER is the leading manufacturer of textile testing equipment. The USTER hairiness H is defined as follows .
H =total length (measured in centimetres) of all the hairs within one centimetre of yarn .
(The hairiness value given by the tester at the end of the test is the average of all these values measured, that is,if 400 m have been measured,it is the average of 40,000 individual values) . The hairiness H is an average value,giving no indication of the distribution of the length of the hairs. Let us see an example
Both yarns would have the same hairiness index H, even though yarn is more desirable,as it has more short hairs and less long hairs,compared to yarn 2.
This example shows that the hairiness H suppresses information,as all averages do. Two yarns with a similar value H might have vastly different distributions of the length of the individual hairs.
The equipment allows to evaluate the variation of the value H along the length of the yarn. The “sh value “is given, but the correlation to the CV of hairiness is somehow not obvious.A spectrogram may be obtained.
Zweigle is a somewhat less well known manufacturer of yarn testing equipment. Unlike USTER,the Zweigle does not give averages. The number of hairs of different lengths are counted separately, and these values are displayed on the equipment. In addition, the S3 value is given,which is defined as follows:
S3 =Sum (number of hairs 3 mm and longer)
In the above example,the yarns would have different S3 values:
S3yarn 1 =2 .
S3yarn 2 =4 .
A clear indication that yarn 2 is “more hairy “than yarn 1. The CV value of hairiness is given a histogram (graphical representation of the distribution of the hairiness) is given.
The USTER H value only gives an average,which is of limited use when analyzing the hairiness of the yarn.The Zweigle testing equipment gives the complete distributionof the different lengths of the hairs. The S3 value distinguishes between long and short hairiness, which is more informative than the H value.
Ten Fundamental Rules for Successful Operation of EliTe Ring Spinning Machines:
EliTe Q Spinning Machines produce yarn of supreme quality and come up to the expectations. Installation of the machine in the spinning mill EliTe Q Spinning Machines have a considerable air flow rate –a machine with .1008 spindles sucks in about 60 cubic meter of air per minute,i.e. it has the effect of a vacuum cleaner. The ambient air is sucked into machine and most of the fly and dirt contained in it is deposited on the EliTe Q Machine. Although EliTe Spinning Machines generate considerably less fly than standard ring spinning machines, they are soon covered with dust and fly if they are installed in the same room as conventional spinning machines. The fly has a negative effect on the yarn in the condensing zone and the smooth running of the lattice apron. As a result,the yarn is of substandard quality.
Rule .:EliTe Q Spinning Machines must be separated from conventional spinning machines.
Spinning room conditions: The fibres in the condensing zone are exposed to the room conditions without any protection. Our recommendations on the room conditions suitable for processing cotton and man-made fibres should be followed, therefore. If the air humidity is too high, there will be a higher tendency towards roller laps. If the air is too dry,t here will be more fly. If the room temperature is too high, there will be higher friction values and premature wear.
Rule 2:maximum room temperature:33 .C
humidity should be
max…,5 g water/kg air for cotton
min.9,0 g water/kg air for cotton
max..0,0 g water/kg air for synthetics
min.9,0 g water/kg air for synthetics
Position of the Eli Top in relation to the front bottom roller of the drafting system: If the setting is correct, the top edge of the suction slot in the Eli Tube is precisely set at the nip line of the delivery top roller. If the nip line cuts the slot, condensation is impaired. The hairiness of the yarn increases and the tearing strength is reduced. If the nip line is behind the slot, part of the spinning torsion may get into the condensation zone, resulting in an increased ends-down rate and damaged lattice aprons.
Rule 3:The front top roller is precisely 3.5 mm offset towards the operator in relation to the front bottom roller of the drafting system.
Traverse mechanism: The roving must run over the slot in such a way, that, from the operator ’s view, the fibres move from the top right to the bottom left. If the fibres run over the slot top from the L.H. side,they make an S-shaped movement causing a certain unsteadiness in the condensing zone. This has a negative effect on the yarn values.
Rule 4:The traverse mechanism for the sliver should be adjusted in such a way that the traverse motion at the front of the drafting system does not exceed 4 mm,and that the l.h.limit position of the sliver is level with the L.H..edge of the top of the slot.
Cleaning the Eli Tubes and lattice aprons :Eli Tubes and lattice aprons are the most important components of the EliTe Q Condensing System. Careful maintenance is an important prerequisite for optimum yarn values. In the centre area, where the suction is active, a permanent air flow keeps the lattice aprons clean. To the left and right of this area, the lattice apron can be clogged by fine dust. With the time, this results in a considerable increase of the friction between the lattice aprons and the EliTube. If this friction is too high, erratic running of the lattice apron and substandard yarn quality is the result. Therefore,lattice aprons and Eli Tubes should be removed from the machine from time to time and cleaned. This can be done when the machine is running. The time needed per box length is 5 min. The expenditure of time necessary for changing the EliTubes with lattice aprons is about 90 minutes for a machine with .1008 spindles, which corresponds to a loss of production of 90 minutes. For yarn count Ne 40, the production loss involved is less than 370 g. The cleaning frequency varies depending on the portion of fine dust of the cotton. As an average value, 500 operating hours may be taken into account. The aprons are cleaned in a washing machine or in an ultrasonic cleaning device.The EliTubes are cleaned using a damp piece of cloth. Damaged lattice aprons must be replaced. On EliTubes with considerable traces of wear, the inserts must be replaced.
Rule 5:Lattice aprons and Eli Tubes must be cleaned from time to time.
Measures to be taken in the case of laps at the front top roller Laps may occur in the case of unsuitable room conditions or damaged or inappropriately buffed cuts, or if the fibre material used is prone to the formation of laps. Large laps may block the delivery and front rollers and damage the cot of the blocked roller. If spinning is continued with damaged cots,periodic yarn faults will be the result. Consequently, a blocked Eli Top must be replaced by a new Eli Top and repaired in the service room. For this purpose,all operators should carry a spare Eli Top with them.
Rule 6:EliTops with blocked top rollers must be replaced by new top rollers.
Buffing the EliTe Q Top Rollers : The cots of the EliTe Q Top Rollers are subject to wear and should be buffed from time to time.The tension draft in the condensing zone –6 %as a general rule depends on the difference in diameter between the front top roller and the delivery top roller. Changed tension drafts may result in changed yarn parameters.
Rule 7:Make sure that the difference in diameter of the front top roller and the delivery roller corresponds precisely to the desired tension draft.
Checking the partial vacuum As a general rule,continuous control of the vacuum pressure is not necessary. When the whole machine is cleaned, we recommend, however,to remove also the connecting hoses between the suction tubes and the fans and to clean them.
Rule 8:Clean the connecting hoses with regular frequency.
Maintenance of the fans: Fans may be clogged after a time,which has a negative effect on the suction.
Rule 9:The fans should be removed from the machine and cleaned once a year.
Spinning speed: In the case of EliTe Q Spinning Machines, return on investment is not based on higher production, but on the production of yarn of supreme quality. The Suessen recommendations concerning traveller speeds and running-in speeds for rings and travellers should be followed, therefore. Not the ultimate increase in speed, but the yarn quality leads to success.
Rule 10:Yarn quality is more important than quantity.
“Card is the heart of the spinning mill” and “Well carded is half spun” are two proverbs of the experts.These proverbs inform the immense significance of carding in the spinning process.High production in carding to economise the process leads to reduction in yarn quality.Higher the production, the more sensitive becomes the carding operation and the greater danger of a negative influence on quality.The technological changes that has taken place in the process of carding is remarkable. Latest machines achieve the production rate of 60 – 100 kgs / hr, which used to be 5 – 10 kgs / hr, upto 1970.
flock feed system (flocks are transported pneumatically)
· lap feeding
linear density of the lap is very good and it is easier to maintain(uniformity)
the whole installation is very flexible
deviations in card output will be nil, as laps can be rejected
autolevellers are not required, hence investment cost and maintenance cost is less
transportation of lap needs more manual efforts( more labour)
lap run out is an additional source of fault, as it should be replaced by a new lap
more good fibre loss during lap change
more load on the taker-in, as laps are heavily compressed
· flock feeding
high performance in carding due to high degree of openness of feed web
labour requirement is less due to no lap transportation and lap change in cards
flock feeding is the only solution for high production cards
linear density of the web fed to the card is not as good as lap
installation is not flexible
autoleveller is a must, hence investment cost and maintenance cost is more
· Type of flock feed(chute feed)
there are two basic concepts of flock feed
one piece chute without an opening device
two piece chute with an opening system
one piece chute is simple, economical and requires little maintenance
two piece chute is complex, expensive, but delivers a uniform batt.
One piece chute is a closed system, i.e.excess flock returns to the distributor, if too much material is present, neps can be increased
one piece chute is not flexible to run different mixings
layout restrictions are more with one piece chute
· A feeding device is a must to feed the web to the Taker-in region and it should perform the following tasks
to clamp the batt securely throughout its width
to grip the fibres tightly without slippage during the action of taker-in
to present the fibres in such a manner that opening can be carried out gently· The diverter nose(sharp or round) and the length of the nose(guide surface) have a significant influence on quality and quantity of waste removed. Short nose diverter avoids fibre slippage but the opening action is not gentle.If the length of the guide surface is too short, the fibres can escape the action of the taker-in. They are scraped off by the mote knives and are lost in the waste receiver.
· Feed roller clothed with sawtooth is always better , because it gives good batt retention. Thus the opening effect of the taker-in is more as it is in combing
· Rieter has developed a “unidirectional feed system” where the two feed devices(feed roller and feed plate are oppositely arranged when compared with the conventional system. i.e. the cylinder is located below and the plate is pressed against the cylinder by spring force. Owing to the direction of feed roller, the fibre 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.
· of The purpose the taker-in is to pluck finely opened flocks out of the feed batt, to lead them over the dirt eliminating parts like mote knives, combing segment and waste plates, and then to deliver the fibres to the main cylinder. In high production cards the rotational speed ranges from 700-1400
· The treatment for opening and cleaning imparted by Taker-in is very intensive, but unfortunately not very gentle.Remember that around 60% of the fibres fed to the main cylinder is in the form of individual fibres.
· The circumferential speed of Taker-in is around 13 to 15 m/sec and the draft is more than 1000.It clearly shows that fibre gets deteriorated at this opening point. Only the degree of deterioration can be controlled
by adjusting the following
the thickness of the batt
the degree of openness of the raw material
the degree of orientation of the fibres
the aggressiveness of the clothing
the distance between the devices
the rotational velocity of the taker-in
the material throughput
· Latest TRUTZSCHLER cards work with three licker-ins compared to one liker-in.The first one is constructed as needle roll. This results in very gentle opening and an extremely long clothing life for this roll. The other two rollers are with finer clothing and higher speeds, which results in feeding more %of individual fibres and smallest tufts compared to single lickerin, to the main cylinder. This allows the maing cylinder to go high in speeds and reduce the load on cylinder and flat tops. There by higher productivity is achieved with good quality. But the performance may vary for different materials and different waste levels.
· between the taker-in and main cylinder , the clothings are in the doffing disposition. It exerts an 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 2.0.
· The opening effect is directly proportional to the number of wire points per fibre. At the Taker-in perhaps 0.3 points/ fibre and at the main cylinder 10-15 points /fibre.If a given quality of yarn is required, a corresponding degree of opening at the card is needed. To increase production in carding, the number of points per unit time must also be increased. this can be achieved by
more points per unit area(finer clothing)
higher roller and cylinder speeds
more carding surface or carding position
speeds and wire population has reached the maximum, further increase will result in design and technological problems. Hence the best way is to add carding surface (stationary flats). Carding plates can be applied at
under the liker-in
between the licker-in and flats
between flats and doffer
· Taker-in does not deliver 100% individual fibres to main cylinder. It delivers around 70% as small flocks to main cylinder. 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.carding segments bring the following advantages
improved dirt and dust elimination
improved disentanglement of neps
possibility of speed increase (production increase)
preservation of the clothing
possibility of using finer clothings on the flats and cylinder
better yarn quality
less damage to the clothing
· In an indepth analysis, all operating elements of the card were therefore checked in regard to their influence on carding intensity. It showed that the “CYLINDER-FLATS” area is by far the most effective region of the card for.
opening of flocks to individual fibres
elimination of remaining impurities(trash particles)
elimination of short fibres( neps also removed with short fibres)
untangling the neps
high degree of longitudinal orientation of the fibres
· The main work of the card, separation to individual fibres is done between the main cylinder and the flats Only by means of this fibre separation, it is possible to eliminate the fine dirt particles and dust. When a flat enters the working zone, it gets filled up very quickly. Once it gets filled, after few seconds, thereafter , hardly any further take-up of fibres occurs, only carding.Accordingly, if a fibre bundle does not find place at 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
· In principle, the flats can be moved forwards or backwards, i.e. in the same direction as or in opposition to the cylinder.In reverse movement, the flats come into operative relationship with the 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.
· Kaufmann indicates that 75% of all neps can be disentangled, and of these about 60% are in fact disentangled. Of the remaining 40% disentaglable nep
30-33% pas on with the sliver
5-6% are removed with the flat strips
2-4%are eliminated with the waste
The intensity of nep separation depends on
the sharpness of the clothing
the space setting between the main cylinder and the flats
tooth density of the clothing
speed of the main cylinder
speed of the flat tops
direction of flats with reference to cylinder
the profile of the cylinder wire
· The arrangement of the clothing between the cylinder and the doffer is not meant for stripping action, It is for CARDING ACTION.This is the only way to obtain a condensing action and finally to form a web. It has both advantages and disadvantages.The advantage is that additional carding action is obtained here and it differs somewhat from processing at the flats.A disadvantage is that leading hooks and trailing hooks are formed in the fibres , because the fibres remain caught at one end of the main cylinder(leading hook) and some times on the doffer clothing(trailing hook).
· There are two rules of carding
The fibre must enter the carding machine, be efficiently carded and taken from it in as little time as possible.
The fibre must be under control from entry to exit
· Carding effect is taking place between cylinder and doffer because, either the main cylinder clothing rakes through the fibres caught in the doffer clothing, or the doffer clothing rakes thro the fibres on the main cylinder. Neps can still be disentangled here, or non-separated fibre bundles can be opened a bit in this area and can be separated during the next passage through the flats
· A disadvantage of web-formation at the card is the formation of hooks. According to an investigation by Morton and Yen in Manchester, it can be assumed that
50% of the fibres have trailing hooks
15% have leading hooks
15% have both ends hooked
20% without hooks
· Leading hooks must be presented to the comber and trailing hooks to the ring spinning frame. There must be even number of passages between card and comber and odd number between the card and ring frame.