Normally double yarns are being used in warp and weft in suiting to improve durability of fabrics as double yarn strength is more than double the strength of summation of component threads. It adds doubling cost to yarn cost and which ultimately adds to final cost of fabrics. The use of single weft with high twist will reduce manufacturing cost without affecting much of fabric quality and now a days, use of single yarns in weft is gradually gaining popularity.Following are the some precautions required during spinning these single weft yarns.

 

Twist Multiplier: The name of high twist yarn itself indicates that it requires higher twist multiplier during spinning.Normally 30% higher twist multipliers are used for the yarns used as single weft in weaving. For example, use of 4.52 twist multiplier for 33Ne high twist yarns in ring frame will give better appearance and lesser imperfections in fabric when we use as single weft in weaving compared to 3.48 twist multiplier for same count when we use as double warp in weaving. The twist multiplier should increase with increase of viscose percentage in the blend also. The use of 0.5 higher twist multiplier for viscose rich blend (55% Viscose) than the twist multiplier required for same count having 35% viscose in blend. Sometimes designer took decision of deciding twist multipliers alone in large organizations and when some thing goes wrong into the fabric, then start looking towards spinners for yarn quality. The decision of twist must be a combination of designer and person who knows about impact of twist on production, yarn and fabric quality. The loss of production due to higher twist can be compensated very well by increasing spindle speeds in ring frame with improved yarn quality compared to normal yarns of same count.

 

Steaming: The main cause of snarling of yarns is the twist and intensity of snarling increases with increase in twist. Hence high twist yarns will have higher snarling tendency. Such yarns require steaming after auto clearing before delivering to weaving. The steaming eliminates all snarling related issues in weaving.

 

Production Cost: In production calculation, twist comes in denominator. It decides not only productivity level, but also strength of yarns. Higher the twist in the yarn, lower the rate of production of ring frame and higher the strength. This loss of production can be compensated by skipping doubling and using high twist single yarns in weft directly. Also high twist helps in increasing spindle speeds to recover the loss of production, if mill is interested in high speed spinning, but unionized mills have to take care of probable issues of unions.

Breakages of yarns: The breakages are influenced by amount of twist in the yarn. The higher twist helps in keeping breakages in ring frames at bare minimum. The higher twist in the yarn reduces spinning triangle and more twist will flow to nip of front drafting rollers. The operators of machines enjoy their work on high twist machines due to low breakage rates. In case you are running considerable number of ring frames on high twist, you may have to look for increase of workload by giving more spindles to operators, if working atmosphere permits.

 

Amount of Draft: The twist contraction is more in high twist yarns and yarn produced is coarser. The higher draft than required in ring frame to produce required count while spinning high twist yarns.

 

Rewinding of Single Weft: Earlier, single weft ring frame cops were directly used in loom as weft even without removing objectionable faults. Now a days modern high speed winders with electronic clearing and availability of auto-tense facility, one should always go for rewound weft instead of direct weft. The use of rewound weft will improve overall fabric quality.

 

Winding Speeds: The fabric appearance made out of single yarns is inferior compared with appearance of fabric made out of double yarns of equivalent counts. There fore it is better to wind the yarns at lower speed on auto winding by about 5 to 10%, if required as already use of higher twist is taking care of yarn appearance. The winding of single weft on modern auto winders with auto tensor facility is preferred. The winding speeds will not affect yarn quality, but for shutting down the mouth of people who do not know real phenomena. The single yarn appearance at ring frame stage affects more of fabric quality rather than single yarn appearance of auto cleared yarns. The fibers segregated on the yarn surface during winding will not be permanent in nature and wiped out easily from the surface as they are on surface only, not embedded into the yarn structure.

 

Closer Settings in Auto Winding: When doubling the yarn, the imperfection level drastically reduced, but single yarns will have higher imperfections and using single yarns directly in weaving affect fabric appearance.. The closer settings will help you to remove faults to great extent on auto winding, if required based on mills own trial, but not necessary to use closer settings. The contamination is a great concern while spinning dyed high twist single yarns. It is better to have wind such yarns on Siro Clearers except contrast shades in which one of the shade component is of white.

 

Fibres in Cross-Section: The high twist in the yarn helps for better quality of yarns even at higher speeds if we use fine and short fibers. It is advisable to go for finer denier and shorter length fibres for high twist single weft yarns as higher twist multiplier already used in yarn for single weft is helpful even at higher speeds.

Roving Twist: The use of slightly higher twist multiplier in roving not only reduces the thin places in yarn, but also helps in reduction of hairiness in the yarn. But it is possible only when you are running more number of ring frames for long period with separate hank for single weft quality.

 

Traveller Clearer Settings: The traveler clearer settings must be kept closer as yarn diameter is lesser due to more binding of fibers due to higher twist. This is possible only when you are fixing machines for high twist yarns of same count for longer time.

 

Traveller Weight: High Twist yarns require heavier traveler than same count of normal twist. The spinner has to keep stock of travelers accordingly. This is because of lower delivery speed of front roller and lower speed of traveller which reduces tension in the yarn.

 

Count of High Twist Single Weft: The decision of count must be a combination of views of designer and person who knows more about twist and its effect on production, yarn and fabric characteristics. Some times designers over look such decisions without consulting production team also and start blaming production team for anything goes wrong with yarn quality. Ideally single weft count should be about or equal to resultant count of double yarn to be used in warp in the fabric. In this case, the effect of production is much more than the production loss due to higher twist multiplier used in single weft yarns.

 

Use of double yarn with single weft: Even if we use single weft with higher twist multiplier, the strength is less than double yarn. Therefore the use of higher twist multiplier of double warp yarn which is to be used with single weft is preferred to maintain overall strength of fabric. The 20 to 25% higher twist multiplier will work better in double warp to be used in fabric with single weft.

 

The higher twist multiplier, Steaming, higher speeds in ring frame, lower breakages, higher draft, lower winding speeds, closer clearer settings, contamination clearers, higher fibre in yarn cross section, Closer traveler clearer settings and heavy travelers etc are some of the technological requirement in spinning high twist PV dyed yarns.

 

The author is Senior Manager & HOD Spinning PV, Raymond Limited, Textile Division, Chhindwara, Madhya Pradesh.