REDUCTION OF YARN BREAKAGES IN WEAVING

Objective:

The purpose of this project is to study the factors which causes and influence the yarn breakages also the practical step needed to reduce the breakages of both warp and weft yarns on the loom.

1. Importance of yarn breakages in weaving process

In the weaving industry it is always emphasized to increase production and maintain quality of woven fabric so the mill can meet the demands of both national and international quality familiar consumers and markets. Also Competitiveness is the main feature of the textile industry in future. The main issue is able to compete at international levels. It is clear from many international exhibitions that the competition will be very brutal in the coming years. Nowadays many mills are able to produce similar quality of the woven fabric. Therefore the main issue is the cost of grey cloth per meter. In order to lower the production costs per meter of woven fabric the yarn breakages are essential to be reduced at every stage of manufacturing the woven fabric. In weaving industry one of the most frequent facing problems is breakages of both warp and weft yarns which not only reduce the production rate and also deteriorate the quality of the produced fabric. These breakages on the preparatory processes and also on loom produce lots of problems and become labor intensive. Lesser the number of yarn breakages lesser will be the defects. So by reducing these breakages of both warp and weft yarns not only increase the productivity of the processes involved to the production of fabrics including warping, sizing etc maintain quality of the woven fabric can be increased but also reduces wastages of yarn, and energy ultimately the cost per meter/yard of the prepared fabric reduces.

1.1. Effect of yarn breakages on efficiency:It is generally observed and the analysis of the loom stoppage revealed that one breakage per loom per 100,000 picks looses considerably efficiency and at every loom stop there is a chance for a defect to come. So it is very important to note that the end breakage rate cone winding, weft winding, warping, sizing and finally onto the loom has to be controlled as minimum as possible. In order to control end breakage rate different quality control measures are taken in each process. Analysis of the requirements of the weaving mill show that no more than one stop per 100,000 m of weft yarn should occur. As soon as two or more stops per 100,000 m of yarn are available in the high production weaving mill, costs will increase as a result of a reduction in efficiency. If one takes as an example a ring-spun yarn with a yarn count of 20 tex (Ne 30) and a cop weight of 50 g, then at the most one weak place every 41 cops (which could result in a stopping of the machine) would be acceptable. Today, less than 0.4 stops per 1,000 warp threads and 100,000 picks are considered acceptable.

1.2. Benefits of reduction of yarn breakages

1.2.1. Cost Reduction:

When we reduce the yarn breakages the loom, the cost is also reduced. If there are stoppages at the loom because of any yarn breakages problem than it will be repaired and some cost will increase in this manners. When we entangled this problem which cause the loom to stop, the cost automatically goes down.

1.2.2. Man Power

After resolving the problem which cause loom to stop man power will also b reduced. If there is problem of yarn breakage constantly at the loom than a person will be required to handle this situation, and when we solve this problem than there will be no need of person constantly at the loom.

1.2.3.   Effect on Production:

When there is problem of yarn breakage or problem in the mechanical part of loom, the loom will stop to work. In this way the productivity of loom will be affected and when we solve these problems production will also be increased.

1.2.4.   Quality of Fabric:

Yarn breakages on the loom also affect the quality of fabric. When there is constant breakage of yarn and there is definite knotting for this problem. It will damage the quality of fabric. When these problems are solved the quality will also be improved.1.2.5. Wastages of Yarn:

Constant yarn breakages on loom due to different problems also cause the wastage of yarn .This problem will also be solved by reducing the yarn breakages on the loom.
1.2.6. Loom Efficiency:

When the yarn breakages occur because the looms to stop are reduced the loom shut down will also be reduced. This will affect the efficiency of loom and it will increase.
1.2.7. Department Efficiency:

When there are some problems in weaving department and suppose 10 looms out of 100 looms are not working, it will affect the department efficiency and it reduced 10% straight away and when the different problems are solved out the department efficiency will also increase.

1.2.8. Reduction of Start Mark:

Start Mark is a sign which comes on the surface of the fabric when a loom is restarted after a shut down. When there is any problem due to which loom gets off again and again it will leave a “Start Mark” at the surface of fabric and it effect the fabric very badly. After solving the problem this effect will also be reduced and a good quality fabric will obtain.

1.2.9. Convenience for post-weaving operations:

The reduction of yarn breakages will produce lots of convenience for the post weaving operations like wet processing etc

1.3.        Types of loom stoppages:

The loom stoppages occur due to the following reasons.

1. Breakages of warp yarn

2. Breakages of weft yarn

3. Malfunctioning of some important of mechanisms of loom or basic loom motion.

4. Temperature and humidity of weaving depart

1.4.        Factors influence the reduction of yarn breakages:

There are many factors which influence the yarn breakages on loom, though their contribution rations are quite different respectively

• Quality of yarn
• Preparation of warp beam & weft package
• Condition of loom (mechanical, electrical, electronic)
• Atmospheric condition of weave room

1.5.        Loom stoppages measuring units:

Loom stoppages can be calculated in stoppages per unit length of the fabric or per unit time of production. But the most suitable way to describe is stoppages/no of picks and usually no of picks are taken in the unit are 100,000 picks. Different styles of fabric have different value of weft density or no of picks per certain length of fabric such as picks/inches, pick/meter or picks/yard etc. Weft yarn value or pick density gives the exact value of length of fabric wherever it is to be mentioned. So the stoppages per 100,000 are commonly being use determine the stoppages of machines.

1.6.        Practical measures for the reduction of yarn breakages:

There is need of implementation of following practical steps to reduce the yarn breakages.

• Ensure that the yarn coming from spinning must have the suitable characteristics of strength, hairiness, thick places, thin places, neps, and elongation according to the standards for different yarn counts.
• Prepare the report of yarn breakages in each preparatory process so the feed back may provided to the beck process for instance to spinning mills etc.
• Ensure the proper sizing with different chemicals by appropriate add on percentage.
• Study the yarn breakage due to different mechanical, electronic, and electrical parts of the loom and rectify them.
• Compare the yarn breakage rate of different looms and position them either they are effective or not.
• Study and prepare report of loom stoppages on the different loom having same qualities or not so better awareness may obtain about machine.
• Prepare & access the report of loom stoppages on the same type of looms having same qualities or not so better information regarding yarn breakages may obtain about loom.
• Study and define the defects, quality deterioration cases cause by the yarn breakages

2. Properties of yarn selection for weaving:

The choice of the yarn for weaving will necessitate purchase of yarn with CSP in the range of 2000 - 2500 depending on count even though yarn with a lesser CSP will also run. It is better to invest a little more in better raw material and benefit by lesser loom stoppages, better loom efficiency and reduced fabric damages. Yarn stoppages particularly warp yarn stoppages are attributable mainly to raw material quality and/or its preparation for weaving. It is therefore essential the right quality of yarn is purchased for the weaving. The selection of the yarn for production of fabric is a very sensitive matter because this selection affects the efficiency of different process for the production of fabric like weft winding, warping, and sizing and different loom operations. Ultimately the quality of the produced fabric is influenced by the selection of yarn. The selection of the yarn is done according to the requirements of finished fabric. In order to reduce yarn breakage, increase productivity of both machines and labor also the quality of the produced fabric it is essential to select the appropriate yarn for the production of fabric. The selected yarn should meet the predefined standards of yarn strength, yarn hairiness, yarn imperfections (thin, thick places and neps), twist per inch (TPI), yarn elongation and the most important factors. The yarn should be composed of good raw material like cotton of good staple length, maturity, fineness etc. There are different standards for different counts of ring spun yarns (carded/combed) which are given below. For each yarn count there are different standard values of factors e.g. yarn strength, Twist per inch, elongation, hairiness, thin places, thick places and neps.
During selection of yarn the following properties are needed to consider in order reducing breakages of yarns. These are as follows Twist in yarn Tensile strength

• Single yarn strength
• Lea strength
• Elongation
• Hairiness
• Yarn imperfection ( thin, thick places and neps)

2.1. Twist in yarn:

There are two types of twist i.e. Z-twist or clockwise twist and other one is S-twist these directions of yarns have not any effect on the strength of yarn, elongation, lusture, compressibility and compactness but affect the appearance the fabric.
Twist per inch can be calculated by T.P.I=T.F √cotton (Ne)2.1.1. How the yarn strength is affected by the number of twists?

The strength of the yarn increases with the increase in TWIST FACTOR (T.F) so it reduces the yarn breakages but after certain limit this increment in the twist will reduce the strength of the yarn as shown in the graph. Ultimately the yarn breakages rate will be high. So in order to reduce the yarn breakage there should be appropriate twist in the yarn. Staple yarn cannot be spun below a certain value of T.F. At low T.F yarns breaks mainly as result of fiber slippages. However, the T.F increases the angle of the fiber to the yarn axis increase as the strength of the yarn will decrease and yarn breakages rate will be high.

2.1.2. How the yarn elongation is affected by the twist of yarn?

Twisting of fibers contraction in length when yarns twisted some of these tends to recover when the yarn faces tension so the elongation tends to increase with this twist factor. The strength of the yarn in increased and elongation is reduced by an increase in spinning tension, presumably because this produces a more compact and cohesive yarn. This reduction in elongation is not good when such yarns are subjected to the weaving. The rate of ends thus will increase and productivity and quality will be affected. So to reduce the breakages rate the appropriate T.F is used which does not affect the elongation.

2.1.3. How the yarn absorption is affected by the twist of yarn?

The twist of the yarn also affects the absorption the yarn in different processes like sizing. The no of twist in yarn is inversely proportional to the absorption of yarn i.e. high the twist less will be the absorption. This factor is most important before the selection of the yarn other wise the yarn will not get the sizing paste into its core and yarn strength also other purposes of the sizing will not obtain. Ultimately the yarn breakages rate will be high.

2.2. Strength of yarn:

This is one of the most important factor which influence yarn breakages. It is the force in gms weight or pound required to break the yarn. It is calculated either by one of the following method.

·                     Single yarn tensile strength

·                     Lea strength

2.2.1 Single yarn tensile strength:

In weaving the yarn of each yarn is important because every yarn has to withstand high stress strain during different processes. The yarn should have good strength otherwise it will affect the efficiency of machine and quality of the fabrics. CV% of single yarn strength influences warp stoppages more than any other factor. Higher the single yarn strength lesser will be the yarn breakages. Single yarn strength variability should not exceed 8 % and variability of single yarn twist should not exceed 6% if optimum performance is required

2.2.2. Lea strength:

Lea strength is strength of 120 yards of yarn made on warp reel his lea is tested on the strength tester. Lea strength is also considered during selection of the yarn for the manufacturing of fabric. Higher the lea strength lesser will be the yarn breakages. It can be calculated by the following formula

Lea strength (C.L.S.P) = count × weight in lbs

2.3. Elongation:

The factor of elongation plays a very critical role in reduction of the yarn breakages. The elongation depends upon the length of the fiber and also on T.P.I. different yarns have individual values of elongation. For instance cotton has elongation of 6-7% which gives good power to the yarn against breakages. The elongation of yarn play part in each of the preparatory process e.g. cone winding, warping, sizing and weaving on loom. The sized warp sheet of cotton yarn always should have 4-5% elongation to avoid breakages on loom.

2.4. Hairiness:

The yarns which are spun from the higher percentage of short or medium staple length have high ratio of hairiness. The yarn used for the weaving should also have very low hairiness and uniform distribution of hairs throughout the length of yarn. The remaining hairiness of the yarn is sticked onto the yarn with the help of sizing paste. The yarns with minimum hairiness have low yarn breakage and quality of the fabric is also good. So during selection of yarn this factor should be considered and hairiness of the yarn should be tested on the hairiness determining apparatus, so breakages may control and quality of the end product may consistent. Yarn unevenness affects fabric appearance and should preferably be around 12% - 15 %, U% depending on whether we are using combed yarn or carded yarn. Doubled yarns should have significantly lesser U% and lesser number of yarn defects

2.5. Yarn imperfections (thick places, thin places & neps)

The yarn imperfection includes thin places, thick places and neps which have great influence on the yarn breakage and quality of the fabric. It is generally observed that all thick and thin places in the yarns are weak places, because at think place there is no T.P.I and at thin place more T.P.I than normal while neps in the yarn are either due to presence of immature fibers or due to poor carding operation. Neps tend to create FUZZ during shedding due to their breakage of protruding fibers by interfiber friction. Another quality affecting fabric appearance is yarn imperfections - particularly “neps”. These should not exceed 1000 - 1200 per km for carded yarns and 300 per km for combed yarns. The neps/unit length are measured on the apparatus known as “YARN IMPERFECTION TESTER”

3. Reasons of warp stoppages:

Today, less than 0.4 stops per 1,000 warp threads and 100,000 picks are considered acceptable. Only when one considers that (in each case according to the style) 20,000 m of yarn can be available in the weaving zone for 5 to 10 minutes, does the severity of this requirement really become comprehensible. Yarn hairiness, an important warp characteristic, has always been a factor which has influenced the appearance of the cloth, which was true even long before it could be measured. Varying yarn hairiness, e.g., from package to package, results in weft stripes in a woven fabric. Hairiness is also increasing in importance with respect to the running conditions at all processing stages subsequent to spinning. A high amount of hairiness of the warp yarns can negatively influence the movement of the weft yarn through the shed with air-jet weaving machines, and the weft transfer with rapier weaving machines. The result is usually a stop as a result of a warp. Hairy yarns and structure faults in the yarn, such as neps, often produce threads which cling to each other, particularly with the much smaller shed openings in modern weaving machines. If one increases the warp tension in order to avoid these clinging fibers, more end breaks can result due to weak places. The result of this is that hairiness, as well as hairiness variation and particularly periodic hairiness variation, is of increasing importance with warp yarns, especially with respect to their application on high-production weaving machines.

3.1. Selection of cones/spools for the weft yarn:

In order to produce the sheet of warp yarn cones are used as supply package for warp beam similarly the beams after sizing are brought on the looms for weaving. Meanwhile the weft packages don’t require the preparatory processes like warping and sizing. The cones of yarns are directly brought to the loom so the interlacement of weft and warp yarn may do to produce the woven fabric. Weft insertion rate is high and unwinding is intermittent on shuttle less weaving machines. Hence it is necessary to have a hard wound package. It is essential to have anti patterning device to prevent slough-off on the fabrics. For spun yarns, parallel wound package with core diameter of package of 95 mm and a traverse of 90 mm give a good performance. Smaller core diameter of package increases the unwinding tension and enhances the possibility of high weft breakage. Weft accumulators are to be used on high speed weaving machines when the weft insertion rate is above 1000 m/min. The yarn used for the weft insertion should also free from defects so the yarn breakages may not take place. There should be proper cleaning of the yarn during winding on the looms so defects may remove at this stage. If the yarn defects are not removed at this stage then these defected cone and yarn will increase breakages at loom as result the reduction in the production rate and quality of the fabric will also deteriorate. So in spinning process there should be authentic checks on the removal of yarn defects and also production of a good shaped cones having adequate compactness. Similarly when the bags of cones arrive in the weaving premises concern depart should also test the defects of yarn and cones. The report should be made and also send to the spinning mills so they may take practical steps and preventions to avoid these problems. The yarn should have strength, elongation, minimum hairiness, and minimum neps, thick and thin places. The better the yarn selection for the weft yarn better will be the quality of the produced fabric and minimum the rate of yarn breakages.

3.2. Weft yarn properties:

3.2.1. Importance of Automatic Pirn Winding:

In shuttle weaving the size of the shuttle will determine the maximum size of the pirn that can be used and we should use the pirn that has the longest length so that replenishment, which can cause damages, is less frequent. If the yarn breaks and is not sensed in time or if the pirn runs out and the feeler does not actuate stoppage or transfer in time a potential fault occurs and hence pirns must be wound to maximum density and in a shape that will permit tension free and or uniform tension withdrawal. It will, therefore, be necessary to use suitable automatic pirn winding equipment if we are not using shuttleless looms. This problem is compounded further if multi colour weft is used. In addition to the production of proper pirns it will be necessary to have them colour graded properly. This is essential as it is usual to have some shade variation between the end and beginning of the dyed cone or cheese when package dyeing is used for the dyeing operation. Hank dyed yarn can show still greater variation between

lots and has to be guarded against.

3.2.2. Effect of Winding Tension:

Tightly wound pirns with material content of about 25 gms in the case of spun yarns and 15 gms in the case of filament yarns will have to be used in the interest of reduced transfers. In the case of filaments, excess winding tension can caused elongation and result in bright picks which are fabric defects. In earlier years it was usual to be satisfied with yarn of poorer quality characteristics for weft in view of the lesser tensions involved during the process of weaving. Modern high speed weaving machines and methods require higher tensions on both warp and weft, hence they do not permit the use of low quality of yarn. These modern looms also require that yarn quality characteristics for warp and weft must be similar.

3.2.3. Yarn Quality and Type of Loom:

As the weaving industry starts modernizing and installing more modern automatic looms in place of the old non-automatic looms the choice of raw material becomes more critical as the higher investment necessitates keeping the looms running round the clock at efficiencies greater than 90% and this will be possible only with proper raw material quality selection. We cannot afford to take the risks that might have been taken so far as these more expensive looms with their greater production potential can cause greater losses also if they are kept idle or allowed to produce faulty fabric. Modern looms have suitable safeguards to prevent warp breakages and weft breakages from causing defects in the fabric but if the raw material is not selected properly there is a loss in efficiency, which can be costly and has to be avoided

3.3. Requirements of weft yarn for weaving:

In contrast to earlier considerations, a weft yarn today must have a requirement profile as high as that of a warp yarn in order to satisfy the requirements of high-production weaving machines. According to the scientifically-based investigations, a weft yarn must exhibit at least the following quality characteristics as indicated in Table. What have become particularly important, for instance, are the yarn elongation as well as the variations in breaking force and elongation. The Classimat faults can also be considered as weak places, because a thick place fault usually contains less twist than the rest of the yarn, and can easily break when a tensile force is applied. It should be mentioned here that, with a higher variation (i.e., a higher coefficient of variation value of elongation), this can only be compensated by a elongation at break value in order to achieve equivalent running conditions. In terms of the spinning process, this means “Better raw materials, higher yarn twist, etc., certainly result in increased yarn manufacturing costs

4. Effects of yarn conditioning in the reduction of yarn breakages

Moisture in atmosphere has a great impact on the physical properties of textile fibers and yarns. Relative humidity and temperature will decide the amount of moisture in the atmosphere. High relative humidity in different departments of spinning is not desirable so before starting preparatory processes for weaving yarn can be conditioned. But on the other hand, a high degree of moisture improves the physical properties of yarn. Moreover it helps the yarn to attain the standard moisture regain value of the fiber. Yarns sold with lower moisture content than the standard value will result in monetary loss. Therefore the aim of CONDITIONING is to provide an economical device for supplying the necessary moisture in a short time, in order to achieve a lasting improvement in quality. In these days there is a dramatic change in the production level of weaving machines, because of the sophisticated manufacturing techniques. Yarn quality required to run on these machines is extremely high. In order to satisfy these demands without altering the raw material, it was decided to make use of the physical properties inherent in the cotton fibers. Cotton fiber is hygroscopic material and has the ability to absorb water in the form of steam. It is quite evident that the hygroscopic property of cotton fibers depends on the relative humidity. The higher the humidity more will be the moisture absorption. The increase in the relative atmospheric humidity causes a rise in the moisture content of the cotton fiber.
The relative humidity in turn affects the properties of the fiber via the moisture content of the cotton fiber. The fiber strength and elasticity increase proportionately with the increase in humidity. If the water content of the cotton fiber is increased the fiber is able to swell, resulting in increased fiber to fiber friction in the twisted yarn structure. This positive alteration in the properties of the fiber will again have a positive effect on the strength and elasticity of the yarn ultimately lesser will be the yarn breakages

4.1. Yarn conditioning process by XORELLA:

The standard conventional steaming treatment for yarn is chiefly used for twist setting to avoid snarling in further processing. It does not result in lasting improvement in yarn quality. The steaming process may fail to ensure even distribution of the moisture, especially on cross-wound bobbins (cheeses) with medium to high compactness. The thermal conditioning process of the yarn according to the CONTEXXOR process developed by XORELLA is a new type of system for supplying the yarn package. The absence of Vacuum in conventional conditioning chambers prevents homogeneous penetration. The outer layers of the package are also too moist and the transition from moist to dry yarn gives rise to substantial variations in downstream processing of the package, both with regard to friction data and strength. Since the moisture is applied superficially in the wet steam zone or by misting with water jets, it has a tendency to become re-adjusted immediately to the ambient humidity level owing to the large surface area. Equipment of this king also prevents the optimum flow of goods and takes up too much space.

4.2.        Principle of working:

Thermal conditioning uses low-temperature saturated steam in vacuum. With the vacuum principle and indirect steam, the yarn is treated very gently in an absolutely saturated steam atmosphere. The vacuum first removes the air pockets from the yarn package to ensure accelerated steam penetration and also removes the atmospheric oxygen in order to prevent oxidation. The conditioning process makes use of the physical properties of saturated steam or wet steam (100% moisture in gas-state). The yarn is uniformly moistened by the gas. The great advantage of this process is that the moisture in the form of gas is very finely distributed throughout the yarn package and does not cling to the yarn in the form of drops. This is achieved in any cross-wound bobbins, whether the yarn packages are packed on open pallets or in cardboard boxes.

4.3.        Advantages of process:

• Saturated steam throughout the process
• Even penetration of steam and distribution of moister
• Lowest energy consumption with XORELLA ECO-SYSTEM
• Short process time
• Absolute saturated steam atmosphere of 50 degree C to 150 degrees C.
• No additional boiler required, the steam is generated in the system
• Minimum energy consumption(approx. 25 KWh for 1000 kgs of yarn) No tube
• buckling in case of mad-made yarns
• Treatment of all natural yarns, blends, synthetics and microfiber yarns.
• low installation and maintenance cost
• Preheating for trolleys and plastic tubes to avoid drops (Wool)
• Standardized sizes
• Length up to 20 meters (66 feet) and max. temperature deviation of 1°C
• Various loading and unloading facilities
• No contamination of the treated packages
• Energy recovery option offered by indirect heating system using steam or hot water
• No special location required the systems can be operated next to the production machines.

Other benefits achieved out of conditioning for weaving

• up to 15% fewer yarn breaks due to greater elongation and Less fly, resulting in a better weaving quality
• Increased strength Increased take-up of size,
• enhanced level of efficiency in the weaving plant
• Softer fabrics

4.4.        Comments:

Yarn conditioning is not carried out in all the weaving mills although the results of conditioned yarns play a vital role in the reduction of yarn breakages both warp and weft yarn. So yarn conditioning should be considered but keep in mind the additional cost of conditioning machine and cost of steam and other auxiliaries.

4.5.        Conclusions:

The choice of the yarn for efficient single yarn weaving will therefore necessitate purchase of yarn with CSP in the range of 2000 - 2500 depending on count even though yarn with a lesser CSP will also run. It is better to invest a little more in better raw material and benefit by lesser loom stoppages, better loom efficiency and reduced fabric damages. Tests should be taken on the yarn for CV% of lea count and CV% of lea strength and yarns, not exceeding 2.5 % for the former and 6% for the latter, can be expected to perform satisfactorily. Similarly single yarn strength variability should not exceed 8 % and variability of single yarn twist should not exceed 6% if optimum performance is required. Whilst these factors affect loom performance, yarn unevenness affects fabric appearance and should preferably be around 12% - 15 % U% depending on whether we are using combed yarn or carded yarn. Another quality affecting fabric appearance is yarn imperfections - particularly “neps”. These should not exceed 1000 - 1200 per km for carded yarns and 300 per km for combed yarns. Doubled yarns should have significantly lesser U% and lesser number of yarn defects. Doubled yarn CSP in the range 2500 -3300 will provide proper weaving performance. The future of the weaving sector of Pakistan will depend on its ability to meet the quality demands of the domestic and export markets. In both markets by reason of fashion changes smaller runs and larger assortments are becoming the rule. For this purpose better looms have to be installed - Shuttle, Automatic and Shuttleless Looms - and these have to be operated round the clock at over 90% efficiencies and utilization. This will be feasible only with the use of good quality yarn which conforms to specifications for efficient weaving on the basis of low variability in count, strength, low unevenness and with minimum defects which affect performance and fabric visual appearance. Proper material handling has to be insisted upon, so that the material moves from spinning mill to warping / sizing and, thereafter to looms without damage to material, if one has to meet the stringent quality demands. As blend yarns acquire oil stains easily and fabric can be damaged it is essential that proper weft and warp handling procedures are followed at all stages.