In fabric production, one of the most common and confusing quality issues is “ barre . ” The factors that can do or lend to barre are varied and diverse. For this ground, when a barre job is detected, the accomplishments of a sleuth may be required to expose the job and extinguish its cause. Once a cause is identified, stairss can be taken to minimise or extinguish the barre , and better quality cloths can be produced. This treatment will focus on on knitted cloths.
The noun “ barre ” is defined by ASTM1 as an unwilled, insistent ocular form of uninterrupted bars and chevrons normally parallel to the filling of woven cloth or to the classs of round knitted cloth. In a warp knit, barre usually runs in the length way, following the way of narration flow. Barre can be caused by physical, optical, dye related differences in the narration, geometric differences in the cloth construction, or by any combination of these differences. A barre run can be one or several classs broad. A “ typical ” feature of barre is that it by and large consists of chevrons that repetition. Isolated or intermittent defects may or may non be barre .
1 ASTM D123-96a – Standard Terminology Relating to Textiles
Assorted facets of barre are of import for consideration and treatment. The first is the designation of barre . Second, how can barre be analyzed? What are the causes of barre , and eventually, how can it be prevented?
IDENTIFICATION OF BARRE
The first measure in a barre probe is to detect and specify the job. Barre can be the consequence of physical causes that can normally be detected, or it can be caused by optical or dyeability differences that may be about impossible to insulate in the cloth. Barre analysis methods that help to know apart between physical barre and barre caused by other grounds include Flat Table Examinations, Light Source Observation, and the Atlas Streak Analyzer.
Flat Table Examination
For a ocular barre analysis, the first measure is to put a full-width cloth sample out on a tabular array and position both sides from assorted angles. By and large, if the streaky lines run in the yarn way that is in the class way, evident colour differences can be seen by looking down at the cloth in a direct ocular line with the narration or class way, and the defect can be positively identified as a barre defect. Sing the cloth with a light beginning in the background will demo if the barre is physical.
Light Source Observation
After finishing an initial Flat Table Examination, a Light Source Examination may supply farther utile information. Full breadth cloth samples should be examined
under two surface illuming conditions, UV ( UV ) and fluorescent visible radiation. Observations that should be made while sing under visible radiations are:
1. the frequence and breadth of the barre ,
2. whether the runs are dark or light, and
3. the entire length of pattern repetition.
Ultraviolet visible radiation, normally referred to as “ black visible radiation, ” allows the presence of mineral oils to be more easy detected, due to their beaming energy ( glow ) . When observed under UV visible radiation, cloths with runs that exhibit glow suggest improper or deficient readying. A alteration in composing or content of oil/wax by the spinster or knitter without appropriate accommodations in scouring can make this job. Fluorescent illuming simulates the manner of observation that is common to most review tabular arraies in Millss and will foreground whether the barre is perceivable in an industry quality control scene.
Atlas Streak Analyzer
The map of the Atlas Streak Analyzer is to insulate barre caused by physical differences. A fabric swatch is combined with polystyrene sheet movie, and the Atlas Streak Analyzer produces a fictile feeling of a fabric surface by integrating specific conditions of force per unit area and heat. The absence of colour on the fictile feeling ensures that merely physical run effects will be seen. The fictile feeling is examined to find whether the streak alliance matches the
runs observed on the cloth. However, feelings made from spun narrations such as cotton can be hard to read due to the built-in narration fluctuation feature of spun narrations. Besides, a excessively rapid chilling of the trial specimen after doing an feeling can bring forth a moire form. From a valid plastic feeling, the barre beginning can be identified as:
1. physical with all runs demoing on the feeling,
2. optical or dyeability fluctuations where none of the colour runs are aligned on the feeling, and
3. a combination of physical and dyeability differences where some runs align with those on the feeling, and some do non.
Fabrics with combination causes present the greatest challenge for analysis.
If the run analyser indicates the same barre form as seen in the cloth, so the barre chevrons are physical in nature. This can associate to several physical causes such as yarn tensenesss, stitch length, narration count, turn differences, etc.
Yarn tenseness causes can be found by raveling next classs and mensurating the lengths of narration removed from each class. If all the lengths raveled from the cloth are the same, the pieces can be weighed to find if the narration counts are the same.
If the plastic reproduction shows no chevrons, so the barre is due to chemical causes or to light coefficient of reflection differences. Chemical causes relate to improper readying, and light coefficient of reflection differences relate to non-uniform dyestuff incursion or coefficient of reflection. The following measure is to take the colour and measure the stripped sample before re-dyeing to find if the remotion of dye was complete and if the barre is still present. An uneven or uncomplete denudation can bespeak an extra strip. If the colour is stripped uniformly and the barre is gone, so the sample should be re-dyed. If after depriving and over dyeing the cloth no longer has barre , so the barre was caused by improper readying. If the barre remains, so the job is related to optical or light coefficient of reflection jobs.
PHYSICAL BARRE ANALYSIS
When the cause of barre is determined or presumed to be physical in nature, physical cloth analysis should be done. Physical barre causes are by and large considered to be those which can be linked to yarn or machine differences. Methods of physical barre analysis include fabric dissection, microscopy, and the Roselon Knit Extension Tester.
To execute accurate fabric dissection analysis, a fabric sample that contains several barre repeats is required. First, the barre run boundaries are marked by the arrangement of consecutive pins and/or felt markers. Individual narrations are removed from light and dark run subdivisions, and twist degree, twist way, and cut length
weight findings are made and recorded. For dependable mean values to be established, informations should be collected from at least two light/dark repetitions. After digest of narration information, the Numberss can be compared separately to next narrations every bit good as by groupings of visible radiation and dark sunglassess.
Microscopic scrutiny is utile for verifying yarn-spinning systems. Narrations from different whirling systems can hold different light coefficient of reflection and dye soaking up belongingss ensuing in barre when assorted. Ring-spinning green goodss yarn that is smooth with all fibres twisted in a tight spiral. Open-end spinning produces yarn with wrapper fibres that form a belt around the diameter of the narration at irregular intervals. Air jet whirling green goodss yarn with more negligee fibres that form a uninterrupted gyrating set around the inner fibres that are more parallel to the axis of the narration. Microscopy can besides uncover a displacement in loop formation in knitted cloths when twist way ( S and Z ) differences are present.
Roselon Knit Extension Tester2
Barre produced by knitting machinery is comparatively common, is the easiest to see in the greige, and is the easiest to rectify. Often uneven yarn tenseness during knitwork may be a cause. To prove for uneven tenseness, the Roselon Knit Extension Tester can be used. For this trial, a fabric sample is cut and raveled to give yarn samples from light and dark run countries. The narration terminals are taped and clamped
2 Beginning: Spinlon Industries Incorporated, 18 S. Fifth Street, Quakertown, Pennsylvania 18951
to the examiner. As each narration is stretched to the maximal extension point, the points are plotted on graph paper. Comparisons are normally made visually instead than mathematically.
CAUSES OF BARRE
The varied and diverse causes of barre can by and large be summed up in one word – INCONSISTENCY. An incompatibility that leads to barre can arise in one or more of the undermentioned classs:
! fibre quality/raw stuff direction,
! yarn formation/supply direction,
! knitwork procedures, and
! readying and dyeing techniques
Fiber Quality/Raw Material Management
1. Failure to command fiber diameter ( micronaire or denier ) from laydown to laydown.
2. Too high a C.V. of micronaire in the laydown for a given factory ‘s opening line intermixing efficiency.
3. Failure to command the fibre colour in the mix ( grayness Rd, yellowness +b ) .
4. Failure to command maturity/fineness in a laydown
5. Most, if non all, fiber barre can be controlled by the above four points ; nevertheless, under certain unusual fortunes, it may be good to besides choose mixes utilizing ultraviolet coefficient of reflection information for each bale of cotton.
Average micronaire must be controlled within a laydown and from laydown to laydown. Controling mean micronaire in the laydown may non be sufficient to wholly extinguish barre . Other micronaire related causes of barre are:
! & gt ; 0.2 difference in micronaire.
! & gt ; 0.1 alteration in mix-to-mix mean micronaire.
! & gt ; 12.0 % CV of micronaire within the laydown.
It may be necessary to alter the laydown norms sporadically to do usage of all the bales in the warehouse. This must be done easy with no more than a 0.1 alteration in mix-to-mix norms. Figure 1 shows acceptable alterations in micronaire from laydown to laydown.
No barre from micronaire differences should demo in knitted cloths when narrations are mixed on the knitting machine from back-to-back laydowns. However, if laydowns vary more than 0.1 micronaire, for illustration laydowns # 1 ( 4.3 mic. ) and # 6 ( 4.6 mic. ) in Figure 1, so barre is much more likely to happen.
Figure 1: Decelerating Changing Micronaire Average in Laydown Acceptable Change in Micronaire From Laydown to Laydown18.104.22.168.83.94.04.14.22.214.171.124234567891011121314Laydown NumberMicronarie
Figure 2 shows a high CV % in the micronaire for bales within a laydown. The laydown shown has 24 bales with an norm of 4.1 micronaire and a CV % of 17.7. The alteration in micronaire from bale to bale is more than a 0.1 alteration. Besides, the CV % is more than 12.0 % and would likely ensue in barre . High Micronaire CV % in Laydown126.96.36.199.188.8.131.5223456789101112131415161718192021222324Bale NumberMicronaireAvg. 4.1 CV % 17.7 *
Figure 2: Consequences of Changing the Micronaire Average excessively Quickly
Max +/- 1.0 mic
Maturity and Fineness
Although micronaire gives an indicant of fiber adulthood, it does non straight step that belongings. Maturity and fineness related causes of barre include:
! Blending cotton from different growing countries or seed assortments.
! Immature fiber content such as white pinpoints, neps, etc.
Even with proper fibre choice to cut down natural stuff effects on barre , techniques in the gap, cleansing, blending, and teasing countries can hold an impact on barre . These fluctuations can happen at teasing where different sums of non-lint content remotion from card to tease can be a job. Poor blending of fibre from opening through finisher pulling can non be overlooked. In pealing spinning, the running of different types of spindle tapes and the usage of different fingerstalls or new and used fingerstalls assorted together on the same frame can make barre .
Faulty direction in the spinning works can ensue in the undermentioned narration related causes of barre :
1. Yarn count fluctuations.
2. Yarn twist fluctuation.
3. Incorrect yarn – size, colour, blend degree, twist way.
4. Assorted yarn tonss.
5. Assorted shipment day of the months of same dye batch.
6. Uneven waxing or oiling of narration
7. Improper conditioning.
Kniting Procedures and Yarn Management
The set-up and operation of a knitwork machine is complex and requires preciseness scenes to bring forth first quality goods. Machine related causes of barre include:
1. Different stitch scenes ( sew lengths ) .
2. Improper tenseness at a provender.
3. Faulty cylinder or dial Cam scenes.
4. Malfunctioning of storage or tape feeders.
5. Improper threading of narration.
6. Variations at take-down or spreader system.
7. Machine quiver.
8. Dirt, lint, and/or narration fragments in the camming system, fast ones, acerate leafs, or doughnuts.
9. Variation in oil content.
10. Worn acerate leafs, which by and large produce length way runs.
11. Uneven cylinder height acerate leafs ( wavy barre ) .
12. Worn cylinder and/or dial.
Even with a properly set-up machine, barre can still happen at knitting due to hapless yarn direction. Examples of hapless yarn direction at knitting include:
1. Blending narrations of different counts.
2. Blending narrations from different whirling systems.
3. Blending narrations with different blend degrees.
4. Blending narrations from different providers.
5. Blending narrations with different turn level/twist way.
6. Blending narrations with different grades of pilosity.
7. Blending narrations with different sums of wax.
8. Mercerization differences.
9. Excessive backwinding or scratch during this procedure.
10. If narrations are conditioned, so each batch must be uniformly conditioned.
Preparation and Dyeing Techniques
Normally, dyehouses have standard readying processs and expressions that work really good in footings of remotion of non-fibrous contaminations and natural fibre pigmentation. However, some cloths can exhibit barre that is caused by either optical or dyeability issues. Often, the barre is non created in dyeing, but can be highlighted. In this scenario, the dyeing is non the cause but the “ courier ” of the job.
Typically, barre is non a job in Whites, merely in bleached cloths. Therefore, if a cloth is known to hold barre , so that axial rotation should be processed into a white.
Preparation can assist “ dissemble ” barre , but can non and will non extinguish it. The cause of the barre must be eliminated for future axial rotations to be free of the defect.
The scour and/or bleach process can be intensified to dissemble the barre . This can be done by combinations of utilizing a higher temperature or longer treating times. Normally the chemical science will stay the same ; nevertheless, in some instances, it may hold to be increased or changed.
If any alterations are made in the readying process, the cloth and attendant shadiness will perchance alter in whiteness, strength, and visual aspect. In fact, the whiteness will about ever change. If whiter, the old dye expression will necessitate to be adjusted. The strength of the cloth may be affected to the point where it becomes a job. Finally, the surface of the cloth may alter so that it may non fit old tonss. As a consequence of more aggressive readying to cover barre , it is of import to measure such alterations on little samples in the lab or a sample machine.
Tension can play an built-in function in non merely the formation of the cloth, but besides during readying, dyeing, and completing. As with all variables, it must be controlled to cognize parametric quantities and be consistent. Any incompatibilities in tenseness could alter the morphology of the cotton ( i.e. during mercerization ) , degree of dye pick-
up, or surface visual aspect ( i.e. during mechanical coating such as brushing or sanding ) .
Prevention OF BARRE
As discussed in the text, barre is caused by incompatibilities in stuffs, equipment, or processing. To forestall barre from happening, consistence must be maintained through all stages of fabric production. Stock narrations should be decently and carefully labeled to avoid confusions. Fleeting shades and/or marked cones can be utile for accurate narration segregation. Inventory should be controlled on a first in/first out footing. All equipment should be decently maintained and sporadically checked. In whirling and knitting before get downing all-out production, sample dyeings can be done to look into for barre . Knit machine operators should be trained to look for barre as it occurs in the greige. If spotted, the machine should be stopped until the cause is eliminated.
Salvaging a cloth batch with a barre job may be possible through careful dye choice. Color differences can be masked by utilizing sunglassess with really low visible radiation coefficient of reflection ( navy blue, black ) or high light coefficient of reflection ( light yellow, orange, or finished white ) . Dye providers should be able to offer aid in this country. Besides, if the cause of the barre is an uneven distribution of oil or wax, a more thorough readying of the cloth before dyeing may ensue in more unvarying dye coverage.
With close cooperation between production and quality control forces, barre jobs can be successfully analyzed and solved. Recommendations to minimise barre include:
! Knit an full dye batch from the same knitwork machine.
! Use merely yarn from the same spinning batch.
! Use merely from the same cargo day of the month if possible.
! If yarn cargo day of the months must be assorted, so utilize back-to-back cargo day of the months.
! Determine through research lab analysis and experience if the readying processs are sufficient or can they be modified to extinguish the job.
! Determine if some sunglassess and dyestuffs are less susceptible to demoing barre , and apply those to job cloths.
! Make usage of yarn/fabric analysis systems such as CYROSA® .
! Identify those axial rotations within a dye batch that have mixed yarn cargo day of the months so that it is known when the cloths go through the dyehouse.
! Identify dye tonss that have axial rotations from different narration cargos before dyeing.
CASE STUDY IN BARRE
A 100 % cotton, ring-spun individual New Jersey manner T-shirt is knitting in production with a narration that does non hold a barre job. This manner has been knitting for legion yearss and no more of the narration is available for creeling on the machine as the narrations are knitting out. Some narration bundles are “ Skinners ” and others are full five-pound bundles. The machine is 24-inch diameter with 80 provenders.
When the new narration is creeled onto one of the 80 places, the commixture of yarn cargo day of the months begins to take topographic point. For this treatment, we will presume that this new narration will do barre when mixed with the old narration. Once all places are knitting the new narration, there will be no barre . How many axial rotations of cloth will hold barre when both these narrations are present in the axial rotations?
If the knitter is doing 50 lb axial rotations, so each narration bundle will provide 1/80th of the 50-pound axial rotation or 0.625 lbs of narration. Therefore, the new narration will do 8.0 axial rotations of cloth with barre ( 5-pound bundle divided by 0.625 lbs per bundle for a 50 lb axial rotation ) . It is of import to recognize that while this new bundle is knitting, other old narration places on the creel are besides being replaced by new narrations. By the clip the first new bundle has knitted out, all provenders will be utilizing the new narration. When the last old bundle is replaced and all places have new narration, the barre will vanish.
Frequently, many machines will be knitting the same manner. If 10 machines are knitting this manner and are utilizing the old narration and new narrations are placed on these 80 provender machines, so the entire figure of axial rotations knitted with barre will be 80. A sum of 4,000 lbs of cloth will be made with barre . If the manner in inquiry weighs 5.8 ounces per linear narration, so a sum of 11,035 paces of cloth will be made. Further, if it can be assumed that each pace of cloth can do 1.2 shirts, so a sum of 13,240 faulty Jerseies will be made. This is 1,103 twelve
garments. If the cost per shirt is $ 2.05 per unit, so a loss of $ 27,142 plus is realized.
If open-end narration was used for this instance survey alternatively of ring-spun narrations, so 8-pound bundles of narration could be used. This would ensue in 128 axial rotations incorporating 6,400 lbs and 17,655 paces of cloth. From this, 21,186 Jerseies ( 1766 tonss ) would hold been made. Based on a cost per shirt of $ 1.86, the loss would be $ 39,405. The consequence is that bigger bundles mean bigger losingss.
The best methods to cut down the possibility of this calamity are listed below:
1. When blending yarn shipment day of the months of merely one hebdomad, seek to cut down the figure of machines utilizing the old and new narrations.
2. As more machines are using the old narration, consolidate the old bundles to fewer machines. This means taking the narrations from one creel and utilizing them on other machines that are still knitting the old narration.
3. Knit dye tonss from a individual machine if possible.
4. When a axial rotation is known to hold assorted narrations, a research lab dyeing should be done on a swatch from the axial rotation to find if barre is present. If non, so proceed as normal. If barre is present, so the axial rotation should be processed in
sunglassess that are non known to be barre sensitive or prepared with more aggressive chemical science.
It is apparent that barre is a job that consequences from incompatibilities and is a consequence of hapless direction of fibre, narration, and/or related knitwork procedures. The spinster, the knitter, and the dyer must pass on and work as a squad to cut down the potency for barre to happen. A well planned and executed system of supervising the spinning, knitwork, dyeing, and completing systems in the factory can supply for defect free cloths.