YARN TESTING

PROCESS PARAMETER IN SPINNING

INTRODUCTION:
Ringframe Technology is a simple and old technology, but the production and quality requirements at
the present scenario puts in a lot of pressure on the Technologist to select the optimum process parameters
and machine parameters, so that a good quality yarn can be produced at a lower manufacturing cost.

Following are the points to be considered in a ringframe.

Draft distribution and settings

Ring and travellers

spindle speed

Twist

lift of the machine

creel type

feed material

length of the machine

type of drive, above all

Raw material chracteristic plays a major role in selecting the above said process parameters

Technical information and guidelines are given below based on the learnings from personal experience
and discussions with Technologists. This could be used as a guideline and can be implemented
based on the trials taken at site. Some of this information can be disproved in some other applications,
because many of the parameters are affected by so many variables. A same machine or rawmaterial cannot
perform in the same way in two different factories. This is because of the fact that no two factories can
be identical.

DRAFTING:

The break draft should depend upon the following,

fibre type

fibre length

roving T.M

main draft

Some examples are given below,

Normally 1.13 to 1.18 break draft is used for

100%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 51mm

total 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.s

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 draft
more 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
i.e. H1 classimat faults.

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(52mm setting).

Instead of using medium cradle for processing 44mm synthetic fibre, it is always better to use
short cradle with 1 or 2mm wider setting than the recommended to avoid bottom apron damages.
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
heigh 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,maximum spindle speed, winding capacity 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 to be considered

for 12s to 24s , 42mm ring with 180 mm lift can be used
for 24s to 36s, 40 mm ring with 180 lift can be used
for 36s to 60s , 38 mm ring with 170 mm lift can be used
for 70s to 120s, 36 mmring with 160 mm lift can be used.
If winding is a problem, it is better to go for reduced production with bigger ring dia.
Anti-wedge ring profile is better, because of better heat dissipation
Elliptical traveller should be used, to avoid start-up breaks in hosiery counts
special 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.

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 problem. Rings like Titan(from Braecker), NCN(bergosesia) etc, will be able to meet the requirements.

For spindle speeds more than 20000 rpm, ORBIT rings or SU-RINGS should be used. As the area of
contact is more with this rings, with higher speeds and pressure, the heat produced can be dissipated
without any problem. Normal ring and traveller profile will not be able to run at speeds higher than
20000 to produce a good quality yarn.

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.

Lubrication is good with west african cottons. It may not be true with all the cottons from
West africa. In general there is a feeling, cottons from Russia, or from very dry places, lubrication
is very bad. If the fibre lubrication is very bad, it is better to use lighter travellers and change
the travellers as early as possible.

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.

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 between
ring and traveller.

RUBBER COTS AND APRON:

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

There are different types of cores (inner fixing part of a rubber cot)available from different manaufacturers.
Aluminimum core,PVC core,etc. It is always better to use softer cots with aluminium core.

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.

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 83 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

Oil content(electrostatic charges)

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,

after doffing
during speed change
during the maximum speed

by optimising the process paramters.

It is obvious that fine fibres will have a stronger tendency to follow the profile of the roller.
Therefore lapping tendency will be more.

If the fibre is fine, the number of fibres in the cross section will be more, therefore lapping frequency
will be more.

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.
But the pneumafil suction depends on the fan diamater, fan type, fan speed, duct design, length of the
machine, profile of the suction tube etc. If any one of the above can be modified and the suction can
be improved, it is better to do that to reduce the lapping.

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
for synthetic fibres and Berkolising is good for cotton.

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 increases
with increasing relative humidity. The frequently held opinion is that processing performace remains
stable at a steady absolute relative humidity, i.e. at a constant moisture content per Kg of dry air.

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. This is normally expressed as

TWIST PER INCH = TWIST MULTIPLIER * SQRT(Ne)

If the two yarns are to have the same strength, then the inclination angles must be the same.

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

The above detail is self explanatory

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.(especially in combed hosiery counts)

In general 16 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.(around 150 rovings for 1000 spindle machine.) Creel height should be as low
as possible for cotton combed counts.Spare rovings will improve the operators efficiency.

Shorter machines are always better compared to longer machines. But the cost per spindle will go up.
For cotton , polyester/cotton blends, poly/viscose(upto 44mm length), number of spindles upto 1200,br> 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.

Four spindle drive is always better compared to Tangential belt drive. Because small variation in
machining accuracy of bolster , spindle beam etc will affect the spindle speeds, thereby the twist
per inch. Waste accumulation between contact rollers, bent contact rollers, damaged contact rollers,
oil spilling from any one spindle etc. will affect the spindle speeds and thereby TPI. The spindle
speed variation between spindles in a 5 year old ringframe will be verh high incase of tangential belt
? drive compared to 4 spindle drive.

Noise level and energy consumption will be low in 4 spindle drive compared to Tangential belt drive.

Compared to Contact rollers, Jockey pully damages are nil. I have worked with 20 year old ring frames with
Jocky pulleys,but the variations in spindle speed between spindles is very less compared to a 5 year old
ringframe with Tangential belt drive. I have made this comment based on my personal experience.

When processing coarse counts at higher speeds, the air current below the machine is a big problem
with 4 spindle drive . This is due to the more running parts like tinrollers and jockey pullys. This
will lead to more fluff in the yarn, if humidification system is not good enough to suck the floating ,br> fluff.

If spindle speeds is high for cotton counts, every end breaks will result in more fluff in the
department 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.

Dry atmosphere in ringframe department will result in more yarn hairiness, more fly liberation
and more end breaks.

It is a good practice to change spindle tapes once in 24 months.Worn out spindle tapes will result
in tpi variations which is determinetal to yarn quality.

IF YOU WANT TO DISCUSS
PLEASE CONTACT

HOME PAGE