PROCESS PARAMETERS IN SPINNING

PROCESS PARAMETERS IN SPINNING

 IMPORTANT POINTS TO BE CONSIDERED IN RINGFRAME

1.Draft distribution

2.Settings

3.Spindle speed & Travellers used

4.Lift of the machines

5.TM & TPI

6.Raw materials used

DRAFTING:

The break draft should depend upon the following,

fibre type

fibre length

roving T.M

main draft

 1.13 to 1.20 break draft is used

 for100%cotton , Poly/cotton blend, 100% synthetic roving T.M. upto 1.3 for cotton and .80 for Poly/cotton blend, 0.5 to0.7 for synthetic ring frame back zone setting of 60mm for fibres upto 44mm and 70mm for fibres upto 51mmtotal draft in ringframe upto 35

1.24 to 1.4 break draft is used for

100%cottton, poly/cotton blend, 100%synthetic fibre strongly twisted roving i.e higher than the above mentioned T.M. total draft from 33 to 45, back zone setting(R.F) around 52mm for fibres upto 44mm and 60mm for fibres upto 51mm-

 If the total draft is more than 45 or the fibre length is more than 51 and the fibre is a fine fibre(i.e more number of fibres in the cross section)with a very high interfibre friction, break draftmore than 1.4 is used.

Please note that for most of the application, lower break draft with wider setting is used. With higher break drafts, roller setting becomes very critical. Higher the break draft, higher the chances for thin places

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Higher draft with improper back zone setting will lead to thin places and hence more end breaks even though more twist flows into the thin yarn

MAIN DRAFT ZONE:

Mostly for cotton fibres, short cradles are used in the top arm. Front zone setting is around 42.5 mm to 44 mm depending upon the type of drafting system. The distance between the front top roller and top apron should be around 0.5to 0.7mm when correct size top roller is used.

This is normally taken care of by the machinery manufcturer. If a technician changes this setting, this will surely result in more imperfections, especially with karded count the impact will be more. Therefore when processing cotton fibres, care should be taken that the front zone setting should be according to the machinery manufacturers recommendation.

For synthetic fibres upto 44 mm , it is better to use short cradles. Even with 42.5 mm bottom roller setting, 44 mm fibre works well without any problem. Because, the clamping distance will be around 52 mm or 50 mm. The imperfections and U% achieved with short cradle is better than with medium cradle

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If a mill has got a problem of bottom roller lapping, the apron damages are extremely high, it is better to use short cradle for 44 mm fibre and widen the setting by 1 or 2mm. This will minimise the complaints and improve the basic yarn quality also.

Please note that if the bottom apron breakages are high, then the mill is working with a lot of bottom apron which is defective and with a lot of top roller which is defective. Both the defective parts produces a defective yarn, which can not rejected by older version of yarn clearers, and improperly set new type of clearers.

This yarn will very badly affect the fabric appearance. Therefore it is always advisable to use a wider front zone setting upto 2mm , if the mill faces a problem of excessive bottom roller lappings.

Please note that the defective bottom apron and top roll will not only affect the quality, but also the production, because the defective bottom apron and top roll make the spindle a sick spindle which will be prone to end breaks. A wider front zone setting will increase the imperfection and uster, but there will not be major deviations of yarn quality.

Nose bar height setting is very important. Depending upon the design, it is 0.7mm or .9 mm. Variation in height setting will affect the yarn quality and the apron movement. The distance between nose bar and middle bottom roller should be less than apron thick ness or more than 3 mm to avoid apron buckling if there is any diturbance in apron movement

RING AND TRAVELLER:

Ring diameter, flange width and ring profile depends upon the fibre, twist per inch, lift of the machine,spindle speed etc.

Operating speed of the traveller has a maximum limit, because the heat generated between ring and traveller should be dissipated by the low mass of the traveller with in a short time available.

If the cotton combed yarn is for knitting, traveller speed will not be a limiting factor. Since yarn TPI is less, the yarn strand is not strong enough. Therefore the limiting factor will be yarn tension

Following points are some guidelines

1. for 10s to 20s , 42mm ring with 180 mm lift can be used

2. for 20s to 34s, 40 mm ring with 180 lift can be used

3. for 34s to 60s , 38 mm ring with 170 mm lift can be used

4. for 70s to 120s, 36 mm ring with 160 mm lift can be used.

5. If winding is a problem, it is better to go for reduced production with bigger ring dia.

6. Anti-wedge ring profile is better, because of better heat dissipation

7. Elliptical traveller should be used, to avoid start-up breaks in hosiery counts

8. Suitable type of travller clearer can be used to avoid accumulation of fibre on the  traveller as traveller with waste does not perform well during start-up

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For polyester/cotton blends and cotton weaving counts yarn strength is not a problem. The limiting factor will be a traveller speed. For a ring diameter of 40 mm, spindle speed upto 19500 should not be a proble

 ORBIT RINGS

 will be of great help, to work 100% polyester at higher spindle speeds. Because, of the tension, the heat produced between ring and traveller is extremely high. But one should understand, that ,the yarn strength of polyester is very high. Here the limiting factor is only the heat dissipation.

Therefore ORBIT RINGS with high area of contact will be able to run well at higher spindle speeds when processing 100% polyester.

While running 100% cotton, the fibre dust in cotton, acts like a lubricant. All the cottons do not form same amount of lubricating film. If there is no fibre lubrication, traveller wears out very fast. Because of this worn out or burn out travellers, microwelding occurs on the ring surface,which results in damaged ring surface, hence imperfections and hairiness increases in the yarn.

Traveller life depends upon the type of raw material, humidity conditions, ringframe speeds, the yarn count, etc. If the climate is dry , fibre lubrication will be less while processing cotton.

Traveller life is very less when Viscose rayon is processed especially semi dull fibre, because of low lubrication. Traveller life is better for optical bright fibres

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Traveller life is better for Poly/cotton blends, because of better lubricatiion between ring and traveller.

Because of the centrifugal force excerted by the traveller on the yarn, the particles from the fibre fall on the ring where the traveller is in contact. These particles act like a lubricating film betweenring and traveller.

RUBBER COTS AND APRON:

For processing combed cotton, soft cots (60 to 65 degree shorehardness) will result in lower U% & less thin and thick places.

When softer cots are used, buffing frequency should be reduced to 45 to 90 days depending upon the quality of the rubber cots, if the mill is aiming at very high consistent quality in cotton counts

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If the lapping tendency is very high when processing synthetic fibres for non critical end uses, It is better to use 90 degree shore harness cots, to avoid cots damages. This will improve the working and the yarn quality compared to working with 85 degree shore hardness.

If rubber cots damages are more due to lapping, frequent buffings as high as once in 30 days will be of great help to improve the working and quality. Of course,one should try to work the ringframe without lapping

The basic reasons for lapping in the case of processing synthetic fibre is

End breaks

Pneumafil suction

rubber cots type

fibre fineness &  department temprature and humidity

Almost all the lappings orginate after an end break. If a mill has an abnormally high lapping problem the first thing to do is to control the end breaks,

If the pressure applied on the roller is more, then lapping tendancy will be more. Hence fine and longer fibres will have more tendency for lapping because of high top roller pressure required to overcome the drafting resistance.

If the pneumafil suction is less, the lapping tendency will be more both on top and bottom roller.

The closer the setting between the suction nozzle and the bottom roller, the higher the suction efficiency and lower the lapping propensity.

Higher roving twist will reduce the lapping tendency to some extent. Therefore it is better to have a slightly higher roving twist, provided there is no problem in ringframe drafting, when the lapping tendency is more

With Softer rubber cots lapping tendency will be more due to more surface contact.

The most minute pores, pinholes in the rubber cots or impurities in the cots can cause lapping. Therefore the quality of buffing and the cots treatment after buffing is very important. Acid treatment is good

Electrostatic charges are troublesome especially where relatively large amount of fibre are being processed in a loose state e.g drawframe, card etc.Lapping tendency on the top roll increaseswith increasing relative humidity.

TWIST:

The strength of a thread twisted from staple fibres increases with increasing twist, upto certain level.

Once it reaches the maximum strength, further increase in twist results in reduction in yarn strength

Coarser and shorter fibres require more Twist per unit length than finer and longer fibres.

Twist multiplier is a unit which helps to decide the twist per unit length for different counts from the same raw material.This is nothing but the angle of inclination of the helical disposition of the fibre in the yarn.

Some examples;

For 40s combed knitting application, if the average micronaire of cotton is 3.8 and the 2.5% span length is around 29 mm, Twist multiplier of 3.4 to 3.5 is enough .

 If the average micronaire is around 4.3, it should be around 3.6 to have better working in Ring frame.

cotton combed knitting T.M. = 3.4 to 3.6

cotton combed weaving T.M. = 3.7 to 3.8

cotton carded knitting T.M. = 3.8 to 4.0

cotton carded weaving T.M. = 3.9 to 4.2

The above details are for cottons of 2.5% span length of 27 to 30 mm and the average Micronaire of 3.7 to 4.4. For finer and longer staple, the T.M. will be lower than tha above.

In general for processing poly/viscose , the T.M. is as follows

51 mm, 1.4 denier fibre : T.M. = 2.7 to 2.9 for knitting application

51 mm, 1.4 denier fibre : T.M. = 2.9 to 3.1 for weaving application

44 mm, 1.2 denier fibre : T.M. = 2.9 to 3.0 for knitting application

44 mm, 1.4 denier fibre : T.M. = 3.0 to 3.1 for knitting application

38 mm, 1.2 denier fibre : T.M. = 3.1 to 3.3 for knitting application

OTHERS:

The following ROVING parameters will affect the ring frame process parameters

Roving T.M.

Bobbin weight

Bobbin height

Higher the roving T.M., wider the back bottom roller setting or higher the break draft in ring frame.

For combed material the creel height should be as low as possible in ringframe.

Very long creel heights in ringframe, lower roving T.M. and heavier roving package will result in many long thin places in the yarn.

In general 12 x 6 " bobbins are used. This helps to increase the spare rovings per machine with higher creel running time. Therefore one should aim at increasing the bobbin weight as well as increasing the number of spare rovings in the ring frame.

Normally 6 row creels are used in modern ring frames. Six row creels will accomodate more spare rovings compared to 5 row creels.

 Creel height should be as low as possible for cotton combed counts.Spare rovings will improve the operators efficiency.

For cotton , polyester/cotton blends, poly/viscose,number of spindles upto 1200, should not be a problem. But maintenance is more critical compared to shorter machines.

For synthetic fibres with very high drafting resistance, it is better to use shorter machines, because the load on break draft gears and on second bottom rollers will be extremely high.

 If long machines are used and the maintenance is not good for such application, the bearing damages, gear damages, bottom roller damages etc. will increase. This will result in coarse counts, higher count C.V., long thin and thick places.

If spindle speeds is high for cotton counts, every end breaks will result in more fluff in thedepartment due to the free end of the yarn getting cut by the traveller when the distance between traveller and the bobbin with the yarn is less.

 Higher the delay in attending the end break , higher the fly liberation.If the number of openings of return air system for a ringframe is less and the exhaust air volume is not sufficient enough, then fly liberation from an end break will increase the endbreaks and thereby will lead to multiple breaks.

 End break due to a fly entering the traveller will get struck with the traveller and will result in heavier traveller weight and that particular spindle will continue to work bad.

Multiple breaks are very dangerous, as it will result in big variation in yarn hairiness and

the ringframe working will be very badly affected due to heavier travellers because of the fluff in the traveller.
PROCESS PARAMETERS IN SPINNING