Article 1 : Reasons for Lean Cops in Spinning

Mr.M.R. Surendran, Factory Manager, Nallam Maniam Textiles (P) Ltd., Vellakovil

“Cops which are produced by the spinners mending yarn with repeated ends down consistently
Ignoring the root cause of the breaks – “ are Lean Cops. Lean Cops may be classified into two
categories
1 .Lean cops due to lapses in process control
2. Lean cops due to lapses in maintenance process
When we consider lapses in process control the following relatively attributes to lean
cops .Too much count variation. Count abnormally on finer side. These are against the lapses
in process as briefed here below:
1. Singles in drawing silver due to creel stop motion failure and due to workers not adopting
end to End piecing.
2. Pneumatic suction excess in drawing and simplex. Clearer hoods are not set in position.
3. Split up silver both in draw frame and simplex creel stage and in drafting zone. Split up
roving in Simplex frame
4. Abnormal stretches in drawing and simplex creel stage and in drafting and simplex creel as
well as roving stretches.
5. Improper layering of silver in draw frame cans and projected rivets which causes sliver tear
out casing singles in case of mills where end less cans are not in use.
In the case of lapses in maintenance process the following are to be looked into:
1. Abnormal sliver and roving irregularities due to mechanical disturbances at drawing simplex
and spinning gear units and individual bearing points.
2. Jerky motion of bobbin holder and subsequent creel stretches.
3. Creel guide rods with peeled off coated portion.
4. Roving guide clogged with waste.
5. Jammed top rollers.
6. Channeled bottom and top aprons, which causes fibre plucking and breaks.
7. Spacer opening either too open or too close.
8. Very low top roller pressure.
9. Damaged flutes on bottom fluted rollers, Knife cut and pits on top rollers.
10. Lappet out of centre
11. Groove formation on lappet hook
12. Peeled off coated portion in ABC ring, Damaged separator if ABC rings are not provided.
13. Usage of worn out rings Travellers
14. Worn out rings and eccentric rings
15. Spindle Vibration and spindle out of centre.
16. Loose Tapes and Improper Jokey Pulley tensioning.
Like wise we can list out reasons for Lean cops. Accordingly we should take Remedial action
timely diagnosing reasons sensibly. If not lean cops arrested to zero, market complaint from
sources like warping – knitting –Sizing and other processing centers are given warm welcome.
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Spinning : Technology & The Future - M M Ahmed

After advent of compact spinning, yarn quality parameter has changed, especially in respect of hairiness, strength and in some respect Imperfection.

Here is a research work in respect of modified spacer and cradle in further improvement of yarn quality of compact yarn & conventional yarn. Today, the main goal of companies is to achieve improved yarn quality that will ensure better competitiveness and higher yarn prices. Current spinning technology developing is aimed at how to maintain higher productivity with effective quality control, by selecting suitable equipments and spinning conditions to match with the raw materials. So, modern developments of machinery, labor demand and increasing market competition compel the spinner’s to produce as satisfactory yarn as is economically possible. Abstract: The article presents the comparison of modified spacer and cradle VS normal. I have analyzed and compared the physical mechanical etc. parameters from the same cotton, cotton/polestar (CVC) roving and same spindles were performed, in different modern group mills with state of the art machines / normal machines are described within this work. The purpose of this study to determinethe influence of modified and normal spacers and cradles on yarn quality in compact and normal spinning and to compare the produced yarn, specially Imperfection (long/short).

Key Words
Conventional spinning, compact spinning, normal spacers, modified spacer, normal cradle, modified cradle yarns, imperfection (IPI),uniformity (U %).

Introduction and Motivations
In spite modernization and rapid technological development in the field of ring spinning, the mechanism ring-traveller spindle has remained almost the same until now. Furthermore, ring spinning remains the dominant spinning technology even today. The producers of modern spinning frames have been developing the machines with improved construction of different working elements and optimal spinning geometry, with a ring diameter of 36 mm, a tube length of 180 mm and spindle speed of up to 25,000/min.

Besides the conventional functions (spindle speed, delivery speed, productivity, twist, draft, machine efficiency), computer-based system control and enable the optimization of spinning conditions (formation of bobbins, position of ring rail, automated doffing and setting of empty tubes, cleaning and oiling of main machine parts). Construction improvements of different working elements of the ring-spinning frame and optimized spinning geometry of the continuous from of fibres (roving or sliver) enable increased productivity, better yarn quality, as well as flexibility and profitability of the process.

The irregularity introduced in drafting mainly depends upon the parameters of the drafting system, mechanical faults and quality of the input material. When mechanical faults are eliminated, drafting ir-regularities depend upon to control on the floating fibers in the drafting zone. Setting between the roller nips, distance between the apron at the nip, distance between the apron at the nip, and pressure on the top roller are some of the factors. The characteristics of the sliver fed to the drafting system also exercise considerable influence on the irregularities introduced and drafting system operated under the optimum conditions. Short fiber content, neps, trash and other impurities degree of fiber parallelization and number and extend of residual hooks in the fibers together with their direction of presentation are some of the important factors that characterize sliver quality and determine its behavior during drafting.

Nutter and slater examined the effect of hooked fiber on yarn strength and found that better strength is obtained when a fiber tip is presented to the drafting system than a hooked end. Grade, Wakanker and Bhaduri found better yarn regularity and strength when majority hooks are fed as leading. Simpson, Deluca and Flori also confirmed that feeding majority hooks as leading to the ring frame contributed to poorer yarn quality and more breakages, the effect being pronounced in case of fine yarns. Apart from hooks, the fiber parallelization may also effect on drafting irregularities.

The treatment given to raw material during spinning process throughvarious machines greatly influences not only the quality of spun yarn but also its quantum. Factory like setting betwe e n r o l l e r s, d r a f t distribution, Pressure on top
rollers, shore hardness of rubber cots, spacers, type/size of ring travelers, rings, relative humidity in the plant and mixing of raw material etc, contribute towards the quality and quantity of yarn. Moisture content in the raw material especially in cotton is very important because of its direct effect on yarn strength as well as elongation and neps in the yarn. Whereas the strength and elongation directly affect the performance of yarn in warping, the neps influence surface of finished cloth and dye take up.

Fiber breakage is a very important factor, because any increase in breakage can lead to additional fly waste and greater number of ends down. Fiber breakage is a function of two main factors; the ratch setting and the roving twist. To avoid breakages, it is necessary to set the ratch longer then the longest fiber, because a shorter ratch will break all fibers greater in length. For a given ratch the extent of machine control over the fiber depend on the length distribution; a wider distribution and a longer ratch lead to lesser fiber control. The strain and distortion imposed on fiber ends during drafting due to the initial pull, continually repeated at each operation also lead to an increase in breakages. It is to be expected, therefore, that fiber will be beheaded or be tailed as a result of this stress and fatigue, the effect being more pronounced in case of longer fibers.

Material and Methods Material
These studies were carried out in modern mills with state of art machines and normal spinning mills using the same mixing, whichmills were using for there regular production, on conventional and compact systems were using. Same mixing with same preparatory process and spinning parameters with same roving and on same spindles. In each mills spinning was done minimum one week and in 2 group mills spinning is performed more than two months and yarn is tested daily on the same doff position. Results are the average of all test results done in respective mill.

Yarn Testing
All testing are done in there own mills labotry, where experiments are performed.

Quality properties of produced yarn
Quality results observed in this study in respect of IPI (short/long) 40 to 60%, uniformity 6 to 10% improvement is noted, where as others quality parameters are also satisfactory.

Results & Discussion
1-Nip distance between front top roller to top and bottom apron nip nearly 12mm and this is the distance in which fiber less than 12mm float freely here and there and with out control, which causes high imperfection (IPI) to control less than 12mm fibre in front zone Modified Spacer are used instead of normal spacer, which helps to reduce long/short IPI in different counts 40 to 60% and uniformity about 6 to 10%, where as remaining results are same or better than normal spacer. Which was the aim of this research. Experiments are done in different locations (Punjab & Sindh) with medium and long cotton, even on CVC also and same trend is noted.

2-In ring spinning there are two drafting zone, one is front zone and second is back zone. In back zone Modified Cradle are used. The reason to use modified cradle was to aligned fiber more parallel and with less hook before entering between top and bottom apron, which also help to improve quality parameters like long/short IPI, uniformity etc.

3- Combination of modified spacer and cradle both. Improvement is also noted. For detail please see count Tex 9.84 (Ne 60)

Work in progress
For more detail work on above subject are still in progress on different count on different locations on different medium and long cotton, carded, semi-combed, combed and cotton blended yarn. Studies on Autocone cuts, classimat etc; are also in progress. Also studies are in progress in down stream processes.

Conclusions
On the basis of this study there is more room for improvement with different combination.

About the Author

• Presently involve in R&D (Research and development).
• Qualification: M.sc, C.Txet.ATI (Textile Institute Manchester, U.K), ICS Diploma in, “Carding & Spinning” from Pennsylvania (USA), ITC from, “City & Guild” London (UK).
• Training/Courses from, Germany, Italy, Japan, Switzerland & China.
• Management Training Course from, “The Association of Overseas Scholarship” (AOTS) Japan. Leadership Improvement & Communication in an Organization” (AOTS) Japan. “Kaizen Management, Cost & Profitability Analysis” (AOTS) Japan. “Auditor / Lead -Auditor” IQA-IRCA (U.K), “Introduction to ISO 9000:2000”.“Internal Quality Auditing for ISO 9000”.
• “Energy Conservation in Industry” (ENERCON), Training / Courses etc.
• Specialization in Compact Spinning.
• Mills experience 20 years in reputable groups and mills (Manager to Technical Director)
• Research experience 2 years as, “Senior Research Officer” (SRO) in,“Pakistan Institute of Cotton Research & Technology Karachi” (PICRT) Pakistan Central Cotton Committee (PCCC) “Ministry of Food & Agriculture, Government of Pakistan”
• Teaching experience 1 year in, “Institute of Leadership & Management” (ILM) Lahore
• Consultancy experience 12 years in, Group & Reputable Mills

Productivity Of A Spinning Mill By Gaurav Doshi

All spinners wish that the spinning productivity of their mill (ring frame production in gms/spindle shift) has the optimum level of efficiency. Though there are many aspects that limit the actual production ­like ring diameter and its age, lift, age and make of the ring frame, its maximum mechanical speed, type of spindle drive, lot size, fluctuating production program, poor control on RH, lower HP of main driving motor, greater percentage of untrained workers, impoverished technical knowledge of subordinates etc.

Today, there is a pressure from the management to decrease the conversion cost to its lowest possible level because of cut throat competition in both the local and export markets. Ring spinning contributes approximately 70 per cent to the total conversion cost. Hence it is possible to speed up the ring frames to its maximum speed mechanically possible ­considering that spinning preparatory can feed ring frames at high speed. Also, neither the spinning performance nor the yarn quality is adversely affected by such speeding up of the ring frames.

Currently many spinning mills in India are capable of managing their ring frames at actual great speeds quite successfully counts 30s-40s at 20/21/22,000 rpm and finer counts - 60s-76s at up to 24,500 rpm and yet maintaining identical breakage rate of 2-3 breaks/l00 spindle hrs that they were earlier performing at 15/16,000 rpm. Also, the yarn quality has not been affected.

Factors that affect spinning productivity

Many factors that affect spinning productivity/end breakages/ yarn properties/ yarn complaints are mentioned here. Increasing productivity is not just gearing up the ring frames but making many efforts such as arranging proper fibres bales to blowroom in a particular direction, maintaining product quality at spg preparatory machines, care of cots and aprons, QC checks, etc., to make sure that spinning breakages, winding breaks, vital yarn properties and quality of yarn at the looms should not deteriorate at all.

Polyester staple fibre associated factors

Change the fibre denier, if possible, to the next stage i.e. if a mill is using 1.4 Den fibre, they can use 1.2 Den. Several advantages here are 20­25 per cent higher number of fibres in the cross section giving to superior yarn strength, improvement in uster value, lesser imperfections and reduced hairiness - which in turn improves weaving performance up to 4-6 per cent with Sulzer weaving machines.

The 'compromise' cut length is 44 mm, though it is believed that in the next 5 years or so, mills will change to 38 mm as is the practice world wide.

Many fibre manufacturers give actual values of important fibre properties with each dispatch. How much the mill technicians consider these values provided by the fibre manufacturers is a debatable issue. It has been seen that most of the mill technicians do not have the proper knowledge to evaluate these values of fibre properties. Of course, it is a good idea if the fibre manufacturers provide the information.

In fact the actual values of the following fibre properties should be given with every dispatch:

. Actual denier

. CV% of denier

. Actual tenacity gms/denier

. Actual per cent elongation at break

. T10gms/denier

. Crimps / 25 mm

. Crimp stability

. Crimp take-up

. Actual oil pick-up and its variation. Actual Dry Heat Shrinkage (@ 180°C for 30 minutes)

. Fused fibres (in mg/10 kg of raw fibre)

. Over lengths/multi lengths - Number per 10 gms

. Actual b colour

Polyester fibre bales to blowroom

Most fibre manufacturers should make sure that dispatch of bales is done in serial order. The reason is that the bales are placed in the warehouse in that order. Today's fibre plants are highly productive. Limits sets in which it make about 120 tons/day, are common. Hence a truck load of bales get made in just 2 hrs or so.

The fibre properties do not vary within 2 hrs, but if it takes more days or say a week, many fibre properties do change some times even outside the set limits. So it helps day' variations are taken care of very well. This ensures smoother running of fibres and no problems of rings under UV and dye variation in the final fabric

It is noted that holding a stock of more than 4 or 6 trucks constantly involves blocking of capital, but

. Ensured no complain of dye variation - streaks warp way and bars weft way

. Ensured no problem of rings under UV lamps.

Hence the benefit received outweighs the extra financial burden. Many mills that have been pursuing this and have gained fully the 3 plus points privilege of above. In Indonesia, many mills utilize Blendomats where 36 bales are placed at one time, hence blending of fibres made on different days.

Performance at spinning preparatory machines

Check that all mechanical data ­total/break drafts, roller settings, TM (Twist Multiplier) etc, even trumpet diameter is completely matching on each and every machine working on one mixing. Changes in C.P (Change Pinion for change in draft) to be done on 'group' basis according to the material being used so as to have minimum machine variations.

Though blending for bales produced is important, it is likewise important to:

1. Number the card cans

2. Check that all cards working on a mixing are represented in the creel of the breaker draw frame

3. Use cans of two different colours at the two deliveries of breaker draw frame

4. Place 4 cans of each colour in the creel of the Finisher Draw frame.

In this way one will have intimate fibre to fibre blending.

Verify all stop motions at both breaker and finisher draw frame and check whether these are functioning well. Also check that the auto leveler is functioning properly.

Check winding tension on the roving remains identical throughout the build of the roving bobbin. Check this by getting 4 full roving bobbins - 2 from front row and 2 from back row; get at least 5 wrappings and work out the average. Place empty roving bobbins on the same 4 spindles and operate the machine until approximately 200 metres is wound up; then detach bobbins and verify wrappings. The variation between the average of wrappings of 'full' and 'empty' bobbins should be less than 2 percent.

Check that no roving bobbin with Uster U percent of greater than 3.5 is sent to ring frames. In order to verify this, check Uster U percent of each and every roving bobbin from a frame once every month. Spot out if there are any arms that are producing off spec bobbins. Get the top arms attended to and recheck the Uster U percent.

Check that the drafting device at the fly frame is only adding 'allowable' unevenness. By having Uster U per cent of finisher sliver, apply the following formula to envisage roving U per cent (U per cent of roving x 1.25)2 = (U per cent of Finisher drawing x 1.25)2 + K, K may be considered as 10.

If the actual roving U per cent is considerably greater than the expected U per cent value, then go for the drafting system, checking conditions of roll­ers, cots, aprons, roller pressure, setting, draft distribution etc. One feasible cause could also be that the total draft is too high. Also check by inspecting Spectrograms of rovings with greater U per cent that there is no interrupted work.

It is important to verify the condition of each and every cot and apron in the mill very frequently, which is practiced daily in Indonesia and once a week by a senior person in India; and any faulty cot/apron is right away put back.

It is noted that if the finisher drawing sliver's U per cent is 1.6; CV per cent of wrapping is 0.22 and the spectrogram proves no interrupted irregularity, then this sliver will function at fly frame with practically zero break; and this roving will function on ring frames with 2/3 breaks/100 spindle hrs at ring frame working at real high speed ­considering ring spinning is well managed but in real life - mainly in textile industry sometimes something else will happen and mill could end up with 10 breaks/100 spindle hrs at high speed.

Ring Frame control

Considering that a spinning mill has accepted all the steps mentioned above, even then the following points need to be focused upon:

Make sure that mechanical data is matching on all ring frames working on one mixing, changes in change pinion be done on 'group' basis. If the actual roving U per cent is considerably greater higher, then, go for the drafting system, conditions of rollers, cots, aprons, roller pressure, setting, draft distribution etc.

Cots and aprons should be tested daily - or at least once in 2/3 days. Also ring travellers should be altered on schedule.

To get a pulse on the functioning at ring frames, best is for the spinning manager himself to carry out snap round compromising all ring frames for number of spindles per frame not making yarn at various intervals of the day. This snap round does not bear much time. A worksheet to be maintained in the department with the following data:

. Date

. Time at start of Round

. Time at end of Round

. Dry Bulb degree Celsius

. Wet Bulb degree Celsius

. RH per cent

. Idle spindle report due to the below mentioned reasons:

1. Spindle break

2. Lapping: top roller, bottom roller

3. Roving: break
exhausted

4. Mechanical

5. Other

It is noted that taking snap rounds is up to 2 spindles not making yarn per frame is pragmatic in good Indian mills and as low as less than 1 spindle not making yarn per frame in good Indonesian mills. In general, if a mill has 2 spindle or less not making yarn/frame (irrespective of the no. of spindles/ frame) then the mill is performing well.

At last consider control on Relative Humidity. A lot of spinning mills still apply wet and dry bulb thermometers. (Many a times water is not placed in wet bulb). The perfection here is exclusively dependent on the perfect judgment of the person who notes down the temperatures. However meters with digital display of both temp and RH are offered, it is recommended putting thermo hygrographs note down temperature and RH continuously for say 24 hrs. Every morning the spinning personnel should check the shape of the trace mainly of RH and in this regards they have to maintain some kind of standardized RH in the department.

There was doubt that with high speed spinning, traveller temperature will increase to blend polyester fibres in the yarn. Luckily nothing like this has happened and blend spinners can carefully run their ring frames even at 25,000 rpm.

Conclusion

It is observed that if a spinning mill follows the steps recommend as above, they can function their ring frames at speeds up to 25,000 rpm (It appears that 25,000 rpm is still the higher limit even at ITMAA Singapore October 2005) without either rising the breakage rate weakening yarn quality. The recommendation provided here is based on experts' experience of functioning with many spinning mills in India and Indonesia increases spinning productivity.

PROCESS PARAMETER IN BLOW ROOM

With all harvesting methods, however, the cotton seed, together with the fibers, always gets into the ginning plant where it is broken up into trash and seed-coat fragments. This means that ginned cotton is always contaminated with trash and dust particles and that an intensive cleaning is only possible in the spinning mill.

Nep content increases drastically with mechanical harvesting, ginning and subsequent cleaning process. The reduction of the trash content which is necessary for improving cotton grade and apperance unfortunately results in a higher nep content level.

The basic purpose of Blow room is to supply

• small fibre tufts

• clean fibre tufts

• homogeneously blended tufts if more than one variety of fibre is used

to carding machine without increasing fibre rupture, fibre neps , broken seed particles and without removing more good fibres.

The above is achieved by the following processes in the blowroom

1. Pre opening

2. pre cleaning

3. mixing or blending

4. fine opening

5. dedusting

CLEANING EFFICIENCY:

Cleaning efficiency of the machine is the ratio of the trash removed by the machine to that of total trash fed to the machine, expressed as percentage

Cleaning efficieny % =(( trash in feed % - trash in del %) x 100) / (trash in feed%)

Following are the basic parameters to be considered in Blowroom process.

• no of opening machines

• type of beater

• type of beating

• Beater speed

• setting between feed roller and beater

• production rate of individual machine

• production rate of the entire line

• thickness of the feed web

• density of the feed web

• fibre micronaire

• size of the flocks in the feed

• type of clothing of the beater

• point density of clothing

• type of grid and grid settings

• air flow through the grid

• position of the machine in the sequence

• amount of trash in the material

• type of trash in the material

• temp and relative humidity in the blow room department

PREOPENING:

Effective preopening results in smaller tuft sizes, thus creating a large surface area for easy and efficient removal of trash particles by the fine openers.

If MBO (Rieter) or BOW ( Trutzschler) type of machine is used as a first machine

• the tuft size in the mixing should be as small as possible. Normally it should be less than 10 grams

• since this machine does not take care of long term blending, mixing should be done properly to maintain the homogenous blending

• the inclined lattice speed and the setting between inclined lattice and clearer roller decides the production of the machine

• the setting between inclined lattice and clearer roller decides the quality of the tuft

• if the setting is too close, the tuft size will be small, but the neps in the cotton will be increased due to repeated action of the inclined lattice pins on cotton.

• the clearance should be decided first to confirm the quality, then inclined lattice speed can be decided according to the production required

• the setting of inclined lattice depends upon the fibre density, fibre micronaire and the tuft size fed. If smaller tuft is fed to the feeding conveyor, the fibre tufts will not be recycled many times, hence the neps will be less.

• if the machine is with beater, it is advisable to use only disc type beater. Saw tooth and Pinned beaters should not be used in this machine, becasue the fibre damage at this stage will be very high and heavier trash particles will be broken in to small pieces.

• the beater speed should be around 500 to 800 rpm depending upon the rawmaterial. Coarser the fibre, higher the speed

• the setting between feed roller to beater should be around 4 to 7 mm

• this machine is not meant to remove trash , hence the fibre loss should also be less

• trash removal in this machine will result in breaking the seeds, which is very difficult to remove

• It is easier to remove the bigger trash than the smaller trash, therefore enough care should be taken to avoid breaking the trash particles

• this machine is just to open the tufts into small sizes so that cleaning becomes easier in the next machines.

• the fibre tuft size from this machine should be preferably around 100 to 200 milligrams.

• If tuft size is small, removing trash particles becomes easier , because of large surface area

If Uniflco11(Rieter) or Blendomat BDT 019(Trutzschler) is used as a first machine

• It helps to maintain the homogeneity of the long term blending

• cotton is opened gently without recyling as it is done in manual bale openers

• with the latest automatic bale opening machines, the tuft size can be as small as 50 to 100 grams without rupturing the fibres

• the opening roller speed should be around 1500 to 1800 rpm.

• the depth of penetration of the opening should be as minimum as possible for better quality

• It is better to use this machine with one mixing or maximum two mixing at the same.

• If the production per feeding machine is less than 150 kgs, then four mixings can be recommended

• production rate of this machine depends upon the no of mixings working at the same time

• production rate depends upon opening roller depth, traverse speed and the fibre tuft density

• in general , the machine parameters should be set in such a way that maximum number of take-off points are available per unit time.

• with the latest machines (Rieter -Unifloc A11), around 60% of take-off points are more compared to earlier machines

PRECLEANING:

Precleaning should be gentle. Since removing finer trash particles is difficult , seeds and bigger trash particles should not be broken. Finer trash particles require severe treatment in Fine openers. This will lead to fibre damage and more nep generation. Therefore, precleaning should be as gentle as possible and no compromise on this. If preopening and precleaning are done properly, consistency in trash removal by fine openers is assured. Dust removal should be started in this machine. Enough care should be taken remove dust in this process.

Rieter's Uniclean B11 and Trutzschler's Axiflow or Maxiflow are the machines which does this work

• the fibre treatment in this machine is very gentle because the fibres are not gripped by the feed roller during beating. Fibre tufts treated by the pin beater when it is carried by air medium

• all heavy trash particles fall down before it is broken

• cleaning efficiency of this machine is very high in the blow room line

• Mostly all heavy seeds( full seeds) fall in this machine without any problem

• around 50 pascal suction pressure should be maintained in the waste chamber for better cleaning efficiency

• beater speed, air velocity through the machine, grid bar setting and gap between grid bars will affect the cleaning efficiency

• higher the cleaning efficiency, higher the good fibre loss, higher the nep generaion and higher the fibre rupture

• the optimum cleaning means maximum cleaning performance, minimum loss of good fibres, a high degree of fibre preservation and minimum nep generation

• Rieter has a unique concept called "VARIOSET". With this machine, selective trash removal is possible. Waste amount can be changed in a range of 1:10.

fig: from Rieter which shows , degree of cleaning, fibre loss, neps, fibre damage.

• with normal machines like Monocylinder or axiflow, a lot of trials to be conducted to arrive at optimum beater speed, air velocity(fan speed), grid bar setting and grid bar gap.

• in general the beater speed is around 750 and minimum 50 pascal suction pressure to be maintained in the suction chamber

BLENDING:

• Barre or streakiness is due to uneven mixing of different cottons. Hence mixing technology is a decisive factor in spinning mill technology

• bigger the differences of cotton parameters like fineness, color and staple length, the greater the importance of mixing

• if the cotton has honeydew, the intenisive mixing of the rawmaterial is a precondition for an acceptable running behavior of the complete spinning mill

following fig is given by trutzschler for different mixing requirements

standard standar- plus high high-end

• Trutzschler's tandem mixing concept is an ultimate solution, if the mixing requirement is very high. This principle guarantees a maximum homogeneous of the mix

FIG.Tandem mixing concept from TRUTZSCHLER:

FINE CLEANING:

Fine cleaning is done with different types of machines. Some fine cleaners are with single opening rollers and some are with multiple opening rollers.

• If single roller cleaning machines are used, depending upon the amount and type of trash in the cotton, the number of fine cleaning points can be either one or two.

• If the production rate is lower than 250 kgs and the micronaire is less than 4.0, it is advisable to use single roller cleaning machines instead of multiple roller cleaning machine.

• Saw tooth beaters can be used, if trash particles are more and the machine is not using suction and deflector blades. i.e beater and regualar grid bar arrangements

• Normal beater speeds with sawtooth beater depends upon the production rate, fibre micronaire and trash content

TYPE OF COTTON	COTTON MICRONAIRE	PROUDCTION RATE kgs/hr	BEATER SPEED rpm
more trash	3.5 to 4.0	200 to 300 kgs /hr	600 to 750
less trash	3.5 to 4.0	200 to 300 kgs/hr	600 to 750
more trash	4.0 to 4.5	200 to 300 kgs	700 to 850
less trash	4.0 to 4.5	350 to 500 kgs	1000 and above

• the number of wire points depends on the proudction rate and trash.

• setting between feed roller and beater depends on the production rate and micronaire. The setting should be around 2 to 3 mm. Wider setting always result in higher rawmaterial faults, if carding does not take care.

• closer the setting between beater and moteknives, higher the waste collected. It is advisable to keep around 3 mm.

• If it is a Trutzschler blowroom line, it is better to use CVT1 ( single opening roller machine) if roller ginned cotton is used.

• CVT3 or CVT4 machines with 3 or 4 opening rollers can be used for saw ginned cotton.

• The cleaning points in CVT1, CVT3, CVT4 etc consists of opening roller, deflector blades, moteknives and suction hood. Trash particles released due to centrifugal forces are separated at the moteknives and continuously taken away by the suction. This gives better cleaning

FIG: trash removal concept in CVT cleaners:

• suction plays a major role in these machines. If suction is not consistent , the performance will be affected badly. Very high suction will result in more white fibre loss and less suction will result in low cleaning efficiency.

• The minimum recommended pressure in the waste chamber (P2) is 700 pascals. It can be upto 1000 pascals.

• material suction (P1) should be around 500 pascals

• Whenever the suction pressure is changed, the deflector blade settings should be checked

• Deflector blade setting can not be same for all the three rollers or four rollers. The setting for deflector blades in the panel looks like this 3, 12, 30 for 1st, 2nd and 3rd deflector blades.

• The deflector blade setting should be done in such a way that the setting should be opened till the fibres start slipping on the deflector blade.

• wider the deflector blade setting, higher the waste. If the setting is too wide, white fibre loss will be very high.

• for saw ginned cottons, the above concepts helps a lot because of constant suction concentrated directly at the moteknives, ensures much removal of dust from the cotton.

DEDUSTING:

Apart from opening cleaning of rawmaterial, dedusting is the very important process in blowroom process.

• normally dedusting starts with precleaning

• it is always better to have a separate machine like DUSTEX of TRUTZSCHLER for effecive dedusting

• dedusting keeps the atmospheric air clean

• dedusting in machines like unimix , ERM of Rieter is good

• stationary dedusting condensers can be used for this purpose

• in exhausts of unimix , condensers , ERM etc, positive pressure of 100 pascal should be maintained. Exhaust fan speed and volume should be accordingly selected

• DUSTEX should be installed before feeding to the cards, because better the fibre opening better the dedusting

• fine opners like ERM, CVT cleaners also help in dedusting

• It is always better to feed the material through condenser for a feeding machine of cards. Because condenser continuously removes the dust from a small quantity of fibres and the material fed to the feeding machine is opened to some extent.

• Since material is not opened well in Unimix, the dedusting may not be very effective, eventhough dedusting concept in Unimix is very good

• for rotor spinning dedusting is very important. It is better to use a machine like DUSTEX after the fine opener.

OTHERS:

• setting between feed rollers is different for different types. It should be according to the standard specified by the manufacturer. For Unimix it should be around 1 mm.

• it is advisable to run the fans at optimum speeds. Higher fan speeds will increase the material velocity and will create turbulance in the bends.This will result in curly fibres which will lead to entanglements.

• If the feeding to cards is not with CONTI -FEED, the efficiency of the feeding machine should be minimum 90 % and can not be more than 95%.

• if the cards are fed by CONTI-FEED system, the feed roller speed variation should not be more than 10%. If the variation is more, then the variation in tuft size also will be more. Hence the quality will not be uniform

• If two feeding machines feed to 10 cards and the no of cards can be changed according the requirement, then frequent changes will affect the tuft size which will affect the quality, if the line is fixed with CONTI-FEED.

• if contifeed system is tuned properly and there are no machine stoppages, continuous material flow will result in better opening and even feeding to the cards

• If the production rate per line is high, the reserve chamber for the feeding machine should be big enough to avoid long term feed variations.

• it is advisable to reduce the number of fans in the line.

• fan speeds, layout of machines should be selected in such a way that material choking in the pipe line, beater jamming etc will not happen. This will lead to quality problems

• all blowroom machines should work with maximum efficiency. The feed roller speeds should be selected in such a way that it works atleast 90% of the running time of the next machine.

• blow room stoppages will always affect the sliver quality both in terms of linear density and tuft size. Blow room stoppages should be nil in a mill

• heavy particles like metal particles, stones should be removed using heavy particle removers , double magnets etc, before they damage the opening rollers and other machine parts.

• Number of cleaning points are decided based on type of ginning (whether roller ginned or sawginned), the amount of trash, and the number of trash particles and the type of trash particles.

• machinery selection should be based on the type of cotton and proudction requirement. If the production requirement of a blowroom line is less than 200 kgs, CVT-4 cleaner can not be recommended, instead CVT-1 can be used.

• Since blow room requires more space and power, it is better to make use of the maximum production capacity of the machines

• material level in the storage chambers should be full and it should never be less than 1/4 th level.

• grid bars should be inspected periodically, damaged grid bars should be replaced.

• grid bars in the front rows can be replaced earlier

• if the cotton is too sticky, the deposits on the machine parts should be cleaned atleast once in a week, before it obstruct the movement of the fibre

• fibre rupture should be checked for each opening point. 2.5 % span length should not drop by more than 3% . If the uniformity ratio drops by more than 3%, then it is considered that there is fibre rupture.

• high fan speed, which will result in high velocity of air will increase neps in cotton

• nep is increased in the blowroom process. The increase should not be more than 100%.

• the nep increase in each opening machine should be checked with different beater speeds and settings, and the optimum parameters should be selected. But please remember that everything should be based on yarn quality checking. e.g. if nep increase in blow room is more and the beater speed or feed roller setting is changed, the tuft size will become more. This may result in bad carding quality. Sometimes if the neps are slightly more and the fibre is well opened, the neps can be removed by cards and combers and the yarn quality may be better. Therefore all trials should be done upto yarn stage.

No of neps and trash particles after different processes is given below.(an approximate value)

• Blow room machinery lay out should be desined in such a way that there should be minimum number of bends, and there should not be sharp bends to avoid fibre entanglements.

• fibre travelling surface should be smooth and clean

• temperature should be around 30 degrees and the humidity is around 55 to 60%.

A best blowroom can be achieved by selecting the following machines:

1.RIETER UNIFLOC- A11 ( pre opening)

2.RIETER UNICLEAN B11 ( pre cleaning)

3.TRUTZSCHLER MPM 6 + MPM6 ( two mixers for blending)

4.TRUTZSCHLER CVT-1 ( for roller ginned cotton) CVT-3 ( for saw ginned)

5.CONTAMINATION DETECTOR from either BARCO OR JOSSI

6.TRUTZSCHLER DUSTEX-DX ( for dedusting)

7.TRUTZSCHLER CONTI-FEED and others

But enough care should be taken to synchronise the machines for better performace , and to run the line without any electrical system breakdowns.

Source - Yahoo GeoCities

Spinning Technology - Cotton Stickiness

COTTON STICKINESS:

Stickiness occurs when excessive sugars present on fibers are transferred to equipment and interfere with processing. Sugars may be insect- or plant-derived. Though sugars are ubiquitous in lint, they usually occur at levels that pose no processing difficulties. This details the sources and components of problem sugars on harvested lint, the processing impacts of stickiness, and strategies for avoiding or mitigating stickiness.

Cottons contaminated with stickiness cause multiple problems in the spinning mills. The honeydew present on the cotton lint is able to contaminate all the mechanical instruments used in the transformation process from fiber to yarn, i.e. opening,carding, drawing, roving and spinning operations. These contaminants are mainly sugar deposits produced either by the cotton plant itself (physiological sugars) or by the feeding insects (entomological sugars), the latter being the most common source of contamination.

Honeydew, when present in sufficient quantity, is the main source of sugars that can result in sticky lint. Honeydew is excreted by certain phloem-feeding insects including such common pests of cotton as aphids and whiteflies. These insects are capable of transforming ingested sucrose into over twenty different sugars in their excreted honeydew. The major sugars in cotton insect honeydew are trehalulose, melezitose, sucrose, fructose and glucose.

Another source of stickiness is free plant sugars sometimes found in immature fibers. Cotton fiber is largely cellulose that is formed from sugars synthesized by the plant. Dry, mature cotton fibers contain little free sugar, while immature cotton fibers contain glucose, fructose, sucrose, and other sugars. If immature cotton fiber is subjected to a freeze, complex sugars may be broken down to release additional simple sugars. Less commonly, oils released by crushed seed coat fragments can also result in stickiness. In this case, raffinose is the characteristic sugar.

Sugars differ in their stickiness. For example, sucrose, melezitose, and trehalulose are all significantly stickier when deposited on fiber than are glucose or fructose. Further, trehalulose-contaminated fiber is stickier than fiber with an equivalent amount of melezitose. Mixtures of sugars, such as occur in honeydew, tend to be stickier than single sugars. Localized concentration of sugars like honeydew is at higher risk of causing stickiness than more evenly distributed sources like plant sugars.

Sticky cotton can reduce cotton gin output (in bales/hr) by up to 25%. At the textile mill, excessive wear and increased maintenance of machinery may occur even with slightly sticky cotton. In severe instances mill shutdown with a thorough cleanup is required.

COTTON APHIDS:

Aphids are slow-moving, soft-bodied insects. Adult cotton aphids are approximately 1/10 of an inch long and roughly pear shaped. They may possess wings or may be wingless. Cotton aphids have two color phases: yellowish or dark green.

The cotton aphid has two projections which arise from the upper side of the abdomen. These small tubes are called cornicles and are used to excrete defensive secretions.

Both the adult and immature stages (called nymphs) of the cotton aphid have stylet like mouthparts, which they use to suck juices from the host plant. Consequently, cotton aphids are sometimes referred to as plant lice.

STICKINESS MEASUREMENT:

‘Stickiness’ is the physical process of contaminated lint adhering to equipment . The degree of stickiness depends on chemical identity, quantity, and distribution of the sugars, the ambient conditions during processing—especially humidity —and the machinery itself. Stickiness is therefore difficult to measure. Nonetheless, methods for measuring sugars on fiber have been and are being developed. These measurements may be correlated with sticking of contaminated lint to moving machine parts. The physical and chemical attributes of the lint and sugars that are correlated with stickiness have been measured in many ways, each with differing efficiency and precision.

REDUCING SUGAR METHOD:

Some textile mills use reducing-sugar tests based on reduction of the cupric ion to screen for sugar contamination. These tests are relatively quick and inexpensive. However, some insect sugars are not reducing sugars, and some others are measured at different levels of efficiency by various reducing-sugar methods. Thus conventional reducing-sugar tests are best reserved for screening lint that potentially has high levels of plant sugars. In these cases and with the potassium ferricyanide (KFeCN) test, lint with reducing sugar levels below 0.3% may be processed without difficulty.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY:

High Performance Liquid Chromatography (HPLC) identifies and measures both reducing and nonreducing sugars. The main sugars of insect honeydew, trehalulose (from whiteflies) and melezitose (from aphids), and of plant sugars (glucose, fructose & sucrose) are all readily identified in this test. The benefit of HPLC analysis is the identification of the source of contamination (whitefly, aphid, or plant) which may help identify specific mitigiation measures

MINICARD METHOD:

The physical interaction of all sugars on lint with equipment can be measured by several types of machines. The primary difficulty with these physical tests is in standardizing the stickiness measurement. As with chemical testing, these tests must be correlated with measures of fiber processing efficiency in order to interpret the results. One of these tests, the minicard, is a physical test that measures actual cotton stickiness of the card web passing between stainless steel delivery rollers of a miniature carding machine. Modeled after a production carding machine, the minicard must be run under strict tolerances. A ‘0’ minicard rating indicates that no sticking was observed, while progressively higher numbers (on a 0–3 scale) indicate progressively greater amounts of sticking during the process. Cottons with high plant sugar contents evenly distributed along the fibers may fail to be measured as sticky in this test. The minicard test is slow and has been replaced as the international standard by the manual thermodetector.

STICKY COTTON THERMODETECTOR:

The Sticky Cotton Thermodetector (SCT) measures the physical sticking points transferred to aluminum sheets by a conditioned lint sample that is squeezed and heated (to 82.5°C for 12 sec.). Levels of stickiness are categorized according to the number of specks left on the two sheets of foild.Lower numbers of specks are preferable to higher numbers; however, a specific threshold over which all cotton will result in processing problems has not been defined. The SCT takes about 5 minutes to process each sample, requires smaller initial investment costs than the minicard, is more mobile, and its results correlate well with predicted stickiness from the minicard.

HIGH SPEED STICKINESS DETECTOR:

The High Speed Stickiness Detector (H2SD) is a quicker, automatic version of the thermodetector. The cotton sample is pressed between a heated (54°C for 30 sec.) and an unheated pressure plate. Sticky points are counted and point size distribution determined by image-processing computer software. Plates are automatically cleaned between samples. The H2SD is able to analyze a sample in 30 seconds.

FIBER CONTAMINATION TESTER:

Like the thermodetector and H2SD, the Fiber Contamination Tester (FCT) measures physical sticking points (at 65% RH). The instrument feeds a thin web between two rollers. Contamination of the rollers interrupts a laser beam, resulting in a recording. Because the cleaning and recording is automated, samples may be processed as quickly as one per 45 seconds.

While there is no reliable infield method for detection of stickiness predisposition, the insects responsible for honeydew deposits can be sampled and populations measured. Not all population levels of insects lead to sticky lint; however, chronic numbers of insects, especially during boll opening or an extended season, can lead to excessive insect sugars that result in stickiness. In addition, field factors associated with risk of excessive plant sugars are lateness of the crop, fiber immaturity, and freezing temperatures before harvest.

STICKINESS CONTROL:

The most efficient way now to prevent stickiness is by managing sugar sources in the field. Detailed integrated pest management plans (see references) for both aphid and whitefly. These honeydew-producing insects may be managed by avoiding conditions leading to outbreaks, carefully sampling pest populations, and using effective insecticides when populations reach predetermined thresholds.

The risk of having excessive plant sugars can be minimized by harvesting mature seed cotton. This may be accomplished through plant management tactics that include: early and uniform planting, nitrogen management according to plant growth and yield goals, high first-position boll retention, and timely chemical termination and harvest. If a freeze is imminent and immature bolls are present, the use of boll-opening chemicals can greatly diminish the problem of plant sugar contamination. All these measures work towards early harvest, before freezing conditions that contribute to excess plant sugars.

MITIGATING THE PROBLEM:

When field management of sugar sources is inadequate to prevent excess accumulation of sugars, mitigation tactics may be necessary to remove excess sugars from the lint. This mitigation may be achieved through both natural and managed processes; however, the specific impact of these processes on stickiness is variable and may depend on the initial level of contamination.

Natural processes include weathering, rainfall, and degradation by microorganisms. Since sugars are water soluble, rainfall will wash some honeydew from lint. If sufficient moisture is available, bacteria and molds living on the plants will decompose many honeydew sugars. Complex sugars are broken down to simpler sugars, and the simpler sugars, given sufficient time and moisture, are further broken down to carbon dioxide and water. Unfortunately, microbial action also leads to discoloration and to a weakening of the fibers as well as heating of cotton in modules that may result in reduced seed viability and problems in ginning.

Potential in-field mitigation techniques include supplemental oversprays of enzymes or water. Certain carbohydrate degrading enzymes when sprayed on sticky cotton can reduce honeydew to simpler sugars. Microbial activity on the fibers then further degrades these simpler sugars, resulting in a significant decrease in fiber stickiness. However, these enzymes require water for activity, and metering the proper amount of water for activity is a problem yet to be solved. In some areas of the world, overhead and in-canopy irrigation has been used to remove honeydew from open bolls. The frequency of this type of irrigation may be more important than the volume applied. Use of sprinklers has been limited in the Western United States, where furrow irrigation is prevalent.

If stickiness is a problem while ginning, the ginning rate of honeydew contaminated cotton can be increased by increasing the heat of the drying towers to reduce humidity. The potential for stickiness can be further reduced by lint cleaning. Both of these practices, however, can result in shorter fibers.

Conventional textile lubricants may also be used. Stickiness due to high levels of plant sugars can be reduced by storing the cotton for approximately six months.

However, storage of baled cotton will not appreciably reduce stickiness from insect sugars. At the textile mill, stickiness may be managed by blending bales and by reducing humidity during carding.

A lubricant in fog form may be introduced at the end of the hopper conveyor, and cardcrush rolls may be sprayed sparingly with a lubricant to minimize sticking.

REFERENCE:

THE ABOVE INFORMATION IS FROM THE UNIVERSITY OF ARIZONA PUBLICATION ON COTTON STICKINESS,

Spinning Technology - Cotton Mixing

MIXING

MIXING(COTTON)

Cotton is a hygroscopic material , hence it easily adopts to the atmospheric airconditions. Air temperature inside the mxing and blowroom area should be more than 25 degree centigrade and the relative humidity(RH%) should be around 45 to 60 %, because high moisture in the fibre leads to poor cleaning and dryness in the fibre leads to fibre damages which ultimately reduces the spinnability of cotton.

Cotton is a natural fibre. The following properties vary very much between bales (between fibres) fibre micronaire fibre length fibre strength fibre color fibre maturity Out of these , fibre micronaire, color, maturity and the origin of growth results in dye absorption variation.
There fore it is a good practice to check the maturity , color and micronaire of all the bales and to
maintain the following to avoid dye pick up variation and barre in the finished fabric.

BALE MANAGEMENT :

In a particular lot

• Micronaire range of the cotton bales used should be same for all the mixings of a lot
• Micronaire average of the cotton bales used should be same for all the mixings of a lot
• Range of color of cotton bales used should be same for all the mixings of a lot
• Average of color of cotton bales used should be same for all the mixings of a lot
• Range of matutrity coefficient of cotton bales used should be same for all mixings of a lot
• Average of maturity coefficient of cotton bales used should be same for all mixings of a lot

  Please note, In practice people do not consider maturity coefficient since Micronaire variation and
  maturity variation are related to each other for a particular cotton.

It the cotton received is from different ginners, it is better to maintain the percentage of cotton from different ginners throught the lot, even though the type of cotton is same.

It is not advisable to mix the yarn made of out of two different shipments of same cotton. For example , the first shipment of west african cotton is in january and the second shipment is in march, it is not advisable to mix the yarn made out of these two different shipments. If there is no shadevariation after dyeing, then it can be mixed.

According to me, stack mixing is the best way of doing the mixing compared to using
automatic bale openers which picks up the material from 40 to 70 bales depending on the length of
the machine and bale size, provided stack mixing is done perfectly. Improper stack mixing will lead to BARRE or SHADE VARIATION problem. Stack mixing with Bale opener takes care of short term blending and two mixers in series takes care of long term blending.

why?

• Tuft sizes can be as low as 10 grams and it is the best way of opening the material(nep creation will be less, care has to be taken to reduce recyling in the inclined lattice)
• contaminations can be removed before mixing is made
• The raw material gets acclamatised to the required temp and R.H.%, since it is allowed to stay in the room for more than 24 hours and the fibre is opened , the fibre gets conditioned well.

  Disadvantages:

• more labour is required
• more space is required
• mixing may not be 100% homogeneous( can be overcome by installing double mixers)

  If automatic bale opening machine is used the bales should be arranged as follows

  let us assume that there are five different micronaires and five different colors in the mixing,
  50 bales are used in the mxing. 5 to 10 groups should be made by grouping the bales in a mixing so that each group will have average micronaire and average color as that of the overall mixing. The
  position of a bale for micronaire and color should be fixed for the group and it should repeat in the
  same order for all the groups

  It is always advisable to use a mixing with very low Micronaire range.Preferably .6 to 1.0 . Because

• It is easy to optimise the process parameters in blow room and cards
• drafting faults will be less
• dyed cloth appearance will be better because of uniform dye pickup etc

  It is advisable to use single cotton in a mixing , provided the length, strength micronaire ,
  maturity coefficient and trash content of the cotton will be suitable for producing the required counts. Automatic bale opener is a must if more than two cottons are used in the mixing, to avoid BARRE or SHADE VARIATION problem.

  It is better to avoid using the following cottons

• cottons with inseparable trash (very small size), even though the trash % is less
• sticky cotton (with honey dew or sugar)
• cotton with low maturity co-efficient

  Stickiness of cotton consists of two major causes. Honeydew from Whiteflies and aphids and high level of natural plant sugars. The problems with the randomly distributed honey dew contamination often results in costly proudction interruptions and requires immediate action often as severe as discontinuing the use of contaminated cottons.An effective way to control cotton stickiness in processing is to blend sticky and non-sticky cotton. Sticky cotton percentage should be less than 25%.

Source - Yahoo Geocities. http://www.geocities.com/vijayakumar777/mixing.html