About Textile

               Process control and product control on fabric in textile

Introduction

When processing goes out of control the amount of waste and the number of seconds increases ,costs go up , and very often temperature too. Higher end- breakage in spinning and winding departments and excessive loom stops due to warp or weft breaks affect the operatives as well as production. A plan of production requires certain standard level to which materials in process must conform . Since it is impossible to maintain a chosen standard absolutely limit on either side of the standard level are calculated and materials whose characteristics fall within these limits are allowed pass forward to next process.

Process Control

Process control is an integral stage of textile manufacture; it involves controlling and predicting process variables such as time, temperature, pH, streaks and broken filaments. Using process control therefore reduces any defects and thereby reduces waste, minimizes costs and reduces the environmental impact.

THE MAIN FUNCTIONS OF PROCESS CONTROL ARE AS FOLLOWS:

1)      Obtaining and maintaining optimum process condition.

2)      To minimize the wastage during process and form reproducible results.

3)      Establishing correct operating procedure.

4)      Carrying out adequate machinery maintenance.

5)      Controlling production yield and waste.

6)      Setting up of testing sequence.

7)      Providing thorough documenting system

8)      Accessing the department’s effectiveness.

The most important function of process control lab is to reduce the cost, by ensuring the production with required quality, with the help of standard specification.

Product control

Quality systems that focus on sorting and isolating defective product are generally called product controls. Because the process generates defective product, efforts are made to identify, sort, and segregate the defective product.

The end product of a process should be fulfill the desired quality, Thai is
count, TPI, GSM, fastness property etc.

Objective of production planning and control:

      To deliver quality goods in required quantities to the customer in the required delivery schedule to achieve maximum customer satisfaction and maximum possible cost.

      To ensure maximum utilization of all resources.

      To ensure production of quality products.

      To minimize the product through put time or production and manufacturing cycle time.

      To maintain optimum inventory levels.

      To maintain flexibility in manufacturing operation.

      To co-ordinate between labor and machines and various supporting departments.

      To plain for plan plant capacities for future requirements.

      To remove bottle neck at all stages of production and to solve problems related to production.

      To ensure effective cost reduction and cost control.

Process Control in Textile Manufacturing

Complex manufacturing processes and delicate raw materials mean the textile industry is particularly dependent on integral process control to produce consistent, efficient results. Controlling and predicting process variables during the textile manufacturing process reduces defects and deviation in product quality, thereby minimizing waste, costs and environmental impact. Process control in textile manufacturing provides a vital overview of the fundamentals and applications of these important methods.

Part one introduces key issues associated with process control and principles of control systems in textile manufacturing, before part two goes on to consider control in fiber production and yarn manufacture. Finally, part three explores process control in the manufacture, coloration and finishing of knitted, woven, non woven, dyed and printed textiles, with additional focus on process control in apparel manufacturing.

Key Topics Covered:

Part 1 General issues: Basics of process control in textile manufacturing

- Basic principles of control systems in textile manufacturing

- Testing and statistical quality control in textile manufacturing.

Part 2 Process control in fibre production and yarn manufacture: Process and quality control in cultivating natural textile fibres

- Process control in the manufacturing of synthetic textile fibres

- Process control in blowroom and carding operations

- Process control in drawing, combing and speed frame operations

- Process control in ring and rotor spinning

- Maintenance of yarn spinning machines.

Part 3 Process control in fabric manufacture, colouration and finishing: Process control in knitting

- Process control in weaving

- Process control in nonwoven production

- Process control in dyeing of textiles

- Process control in printing of textiles

- Process control in finishing of textiles

- Process control in apparel manufacturing.

Woven Fabric Manufacturing Process Flow Chart

Filament/Yarn From Spining Section

↓
Doubling and Twisting

↓
Winding(Two Type-Warp Yarn+Weft Yarn)↓
{                     Warp Yarn(One Side)                           

↓
Bobbin/Cone/Spoll

↓
Creeling

↓
Warping

↓
Sizing

↓
Drowing-In(Looming)

↓
Denting(Looming)

Weft Yarn(other Side)

↓
                               Pern/Cone/Spoll                               }

Weaving

↓
Fabric Checking

↓
Calendaring and Folding

↓

Process control in weaving in textile industry

Steps Involved During Weaving Operation

Selection of yarn for warp and weft purposes

            Sizing

            Winding

               - Spool winding (for warp)

               -Pirn winding (for weft)

            Preparatory Processes for Sectional Warping

               -Creeling

               -Hecking

               -Denting in section guide reed

               -Leasing

            Warping on horizontal drum warping machine

            Beaming

            Drafting arrangement

            Denting

            Gait-up the loom

            Tie up the loom

            Weaving

Selection of Yarn for Warp and Weft Purposes

•         Proper selection of yarn by the technical supervisor at the institution for   warp and weft.

•          Clear instructions to the weaver (Material handling, faults etc)

•          Job instruction sheet for a particular design should be provided.

                                                  Sizing      

Objectives

-To reduce the end breakage rate by improving the abrasion resistance and also the tensile strength of the yarn.

-To enhance the weavability.

Precautions

•         Use of digital balance.

•         Add cold water to the sizing agent.

Sequence of size preparation

-Mixing the adhesive component of size with cold water.

-Addition of wetting agent to the adhesive component.

-Mixing the lubricating agent with boiling water and then adding it to the mixture of sizing and adhesive component.

-Addition of antiseptic agent to the above.

Boiling all the mixed ingredients on slow fire with continuous stirring.

-Continuation of boiling till the sizing paste becomes transparent and of constant viscosity. It is checked by lifting the liquor with the help of a stick.

-The paste is then cooled with continuous stir.

-It is then filtered through fine muslin fabric.

-The boiled and filtered paste is diluted with cold water to the required volume as per the liquor to material ratio of 10:1.

Confirmation of the readiness of the size paste

Lift the size paste between the thumb and the forefinger and smudge it for some time. Separate out the two fingers. Tackiness should be felt while separating the fingers.

Take small amount of size paste and spread it on a clean glass. Allow it to dry. A formation of thin film on drying indicates the good preparation of the size paste.

The absence of tackiness and film formation indicates that the size paste is not properly prepared.

Hank preparation for Sizing

Wetting (use of wetting agent-TRO), Washing and Cleaning.

Conformation of proper wetting

Over and under-squeezing of hanks should be avoided.

Use of hank shaker for squeezing

Sizing operation

Ø  Use of cross bars to hang the hanks for sizing.

Ø  Squeeze the sized hank by using hank shaker.

Ø  Over and under-squeezing should be avoided.

Drying of sized hank

• Drying under direct sunlight should be avoided.
• Avoid spreading the hank on the floor.
• Change the position of hanks time to time.
• Avoid over and under drying of the hanks.
• Give jerks by both the hands to prevent entanglement.
• Do not store the sized hanks one over another.
• Hang in a wooden sticks.

                                                     WINDING

Spool Winding (For warp)

Ø  Locate the first and the last end of the hank.

Ø  Proper use of swift stand.      

Ø  During winding the thread should come out from the top side of the swift.

Ø  Location of swift and spool should be parallel and right direction with respect to each other .

Ø  The threads should be uniformly distributed in the spool and the bobbin should be tightly wound.

The filled bobbin should be stocked one over the other in a rectangular container in vertical

Clockwise unwinding of hank from swift

Pirn Winding (For Weft)

      Proper selection of pirn.

      Pirns should be clean and empty.

      The metallic portion of the pirn (head & nose) should be rust free.

      Knotting of the thread to the pirn should be avoided.

       Pirns should be uniformly and tightly filled up.

      The broken ends should be joined by piecing. Knotting should be avoided.

      Over filling of pirn should be avoided.

      Last weft end of the pirn should be crossed around the filled pirn.

                                  Sectional drum warping

Preparatory processes

a) Creeling

            -The end of the thread from each bobbin should be released from the top.

            -In order to prevent the entanglement of the broken ends of the thread tie a strong cord    in tight condition on the center of each section vertically.

            -Use of over filled warp bobbin should be avoided.

            -All the filled bobbins should be of equal weight and size.

b) Hecking

-The threads of the creel should be divided in odd and even series (all the odd numbered threads should be drawn in to the eye of the heck heald and all the even numbered threads should be drawn in to the dent of the heck).

c) Denting in section guide reed

-Denting in reed (threading) should be according to the weave pattern so that the total width of the warp in the warp beam should tally to the width of warp in the actual weaving reed.

  d) Selection of appropriate counting device

  e) Leasing    

       -Use of leasing reed for cross formation.

       -Insertion of the two lease cord in to the section should be formed after half metre distance.

Warping

     -Tension of all the ends in each section must be uniform and constant at the time of withdrawal from the supply package. Use tension device.

     Spools should be properly aligned in the creel.

   -Maintain the proper sequence of ends by aligning the spool in the creel.

- Routine checking of any interruption in the path of warp ends between creel to section guide.

-Cleaning of complete warping set at regular intervals.

-Tension of all sections should be moderate.

-Too soft or too tight warping should be avoided.

-Warp beam along with its flanges should be carefully handled.

-The yarn should not be subjected to sharp abrasive action to avoid the size removal.

-Spreading of the yarn throughout the whole width of warping must be as uniform as possible.

-Predetermined length of warping should be strictly observed for every section, beam, ball or journey of mill warping, as the case may be.

Drafting

If a new type of fabric is to be woven, calculate the total number of heald shafts required.

-The total number of heald eyes required in each heald frame should be calculated according to design patern.

-All the frames should be parallel to each other.

-Filled warp beam should be fitted just over the heald shafts.

-Proper selection of heald hook required as per the need of the heald gauge.

Denting

-Appropriate reed count should be selected according to the yarn count and the total number of ends per centimeter.

-The denting order should be according to the design pattern.

-The surplus portion of the reed should be equally divided in both the sides.

-Use of reed hook as shown below is required instead of heald hook.

Steps involved in weaving

            1.Shedding

            2.Picking;

            3.Beating-up;

            4.Let-off motion      

            5.take up motiom

Shedding

Appropriate shedding device should be selected.

-Connecting cords for the shed formation should be even and strong.

-The cords should not be directly linked with the heald shafts. In lieu of this the use of loop cord is suggested through which the connecting cord should pass and should be tied by slip knot to either side of the heald shaft.

-Connecting cord from the central bottom of the heald shaft to the paddle should also be tied by slip knot to the loop cord.

-Before weaving it is important to check the formation of uniform shed.

Instead of using two heald shafts use four heald shafts.

The defective shed formation may be due to:

      Incorrect selection of heald wires such as length and gauge;

      Imbalance connection\on of connecting cords;

      Wrong drafting of the warp threads;

      Damaged healds;

      Broken ends of warp;

      Use of undesirable high count of reed;

      Uneven tension of the warp threads;

      Improper fitting of back rest;

      Improper fitting of the reed in to the grooves of the sley;

      Imbalance level of the shuttle rest board;

      Undesirable distance of lease rods;

      Uneven pressure through the paddle; and

      Improper selection of the shuttle .

PICKING

•         Picking should be uniform.

•         Too early and too late picking should be avoided.

•         All connections of the picking cord should be well balanced

•         The picking cord should be even and strong

•         The picking handle should be comfortable.

•         Direct connection of picking cord to the picker should be avoided. In lieu of this the use of loop cord with picker is suggested.

•         For proper picking the loom width should be according to the width of the fabric to be woven.

•         The length of the reed should be equal to the distance between sley arms and the reed should be fitted parallel to the sley arms.

•         For even picking proper selection of shuttle is necessary.

•         The weft thread pirn should not be too tight or too loose.

•         The pirn dimensions (length and circumference) should be such that the pirn is properly fitted in to the shuttle.

•         Shuttle board (Shuttle race) should be smooth and even.

•         Shuttle holder should be properly fitted to the picker. It should not too narrow, too high or too thin.

•         The use of proper shuttle eyelets is necessary for getting desired pick supply.

•         The use of fur in the inner wall of shuttle is necessary for every fine and smooth weft thread.

•         The knots in weft thread should be as minimum as possible.

Beating-up

•         Uniform beating force should be applied.

•         The beating should be in right angle to the fabric. In this regard it is necessary that the distance of both side-hanging noses of the sley should be in equal distance from the cloth guide roller.

•         Trembling force should be avoided.

•         The beater should be held centrally during beating.

•         Far shed beating should be avoided.

•         Open shed beating should be avoided. In lieu of this cross pick beating is suggested.

•         The weaver should hold the sley cap from the center while giving beating force to the fabric.

Let-off Motion

•         Too much or too little release of the warp threads should be avoided.

•         The release of warp threads should be uniform.

•         The tension on warp threads should be uniform.

•         The let off motion device should be in both sides of the warp beam.

•         The arrangement should be such that the let off motion operates automatically.

•         The let off and take up motions should match with each other.

•         Leasing rods should function smoothly.

Take-up motion

•         Winding of the woven fabric should not be too tight or too loose.

•         After weaving the winding of the fabric should be carried out at regular intervals.

•         Take up motion device should be easily approachable to the weaver.

•         If too tight fabric is to be woven, the use of tooth wheels for both take up motions and let off mechanisms necessary. Otherwise, for normal weaving the use of weight system is most appropriate.

Checking the Loom for Errors

The mistakes are:
            -A missed heald eye
            -A missed warp yarn.
            -Crossed drafted and dented threads
            -Too many yarns either in a heald eye or        in a      dent reed.
            -Missing dents of the reed

Selection of Shuttle

Select shuttles taking in to account the weave pattern, count of warp and weft, loom make and reed width.

Avoid the use too old shuttle.

Avoid the use of shuttle made of fibrous wood.

Avoid the use of blurred and bended nose shuttles.

The tongue of the shuttle should tightly grip the pirn.

Shuttle eye should not project outside. It should be within the grip of the wood.

The center of gravity of the shuttle should be towards the shuttle eye. It can be checked by holding the shuttle nose across the grip of the two forefingers. So that it tilts towards the shuttle eye let.

Knitting:

A method of constructing fabric by interlocking series of loops of one or more yarns. The basic element of knitted structure is the loop intermeshed with the loops adjacent to both sides and below and above it.

Knitted fabrics are divided into two main groups-

                                             1. Warp knitted fabric.

                                             2. Weft knitted fabric.

Process flow chart of knitting:

Fabric manufacturing methods are divided into three types- they are weaving, knitting and non weaving. Yarns are to produce different types of fabric. Knitted fabrics are one of them. Knitting technology is one of interesting methods for producing knitted fabric.

Yarn in cone form

Feeding the yarn cone in the creel

Feeding the yarn in the feeder via trip tap positive arrangement and tension device

Knitting

Withdraw the rolled fabric and weighting

Inspection

Numbering.

Knit fabric manufacturing process:

In the knitting industry, planning will typically focus on production, as it can account for up to 80% of the skill and resources required. However, the capacity constraints of supporting areas also have to be assessed. In particular, the pre-production events must be planned to ensure that production begins on schedule.

Centertex is a textile factory manufacturing and marketing a wide range of knitted fabric (cotton, viscose and other fibers, as well as fabric mixes), since more than 30 years. Centertex follows the whole manufacturing process, from planning to production and finally to quality control, in order to supply the customers with end products meeting the needs of the latter. Centertex's products consist of different articles: knitted fabric, interlock fabric, sweatshirts, ribbed articles, piqué, chenille, sponge cloth, pile fabric. Steady or stretch fabric which can be manufactured as garment dyed but also in mélange and/or yarn dyed. The fibers we utilize are: viscose, modal, micro modal and fiber or wool + silk mixes.

Knitted fabric, interlock fabric, sweatshirts, ribbed articles, piqué, chenille, sponge cloth, pile fabric marketed by Centertex undergo internal checks carried out by our skilled technicians, as well as external tests carried out in a laboratory specializing in analyses of textile materials. The reliability and competence of Centertex make a textile company manufacturing knitted fabrics of high quality, a factor that can satisfy all needs of its clients advanced, leading companies in the apparel industry for men, women, and child.

Control of knit fabric quality:

Once a knitting machine has been set up to the specification and an initial sample been checked, the machine should continue to produce satisfactory goods. However, drift, for one reason or another, can set in. Quality Control measurements related to loop length will monitor this and can be incorporated into the overall quality control scheme in the department. Even so; this is not complete, and other control measures for quality are required, both during and after knitting.

Example                                               

Data: -

Test fabric: -

Mass of 5 circles - 7.765g

Area of 5 circles - 5 x 100 sq. cm, i.e. 500 sq. cm

Wales per 3 cm 42, 43, 42.5, 41, 43.5 (AV = 42.4)

Courses per 3 cm 54, 56, 55.5, 53.5, 53 (AV =54.4)

Specification: -

Mass/Sq. Meter 145g

Wales/3 cm 43.5

Courses/3 cm 49.5

Wt/sq. meter: stitch density constant 0.6370 - 0.5764

Setting up the knitting control system:

The need for yarn tension: Because yarns for apparel are highly flexible materials, the only way of keeping them under control is by keeping them taught. In the absence of tension the yarn is uncontrolled and would fail to locate in the needle hook and to knit.

Yarn Length Counter: Generally the reading of a yarn length counter will not drift. However, once in a while it is as well to confirm it. The positive feed checks the knitting: the instrument checks the positive feed; the unproved course length checks the instrument. While no individual check is totally reliable, one can trust the total system of checks.

 Use of a count testing wrap-reel: If a wrap-reel is at hand, a much simpler procedure is available as follows: - Place a cone of yarn being knitted on the count tester's creel, threading-up as for count testing, and adjust the reeling tension to that used in course length tests by adjusting the reeling tensioners and checking the tension with a tension meter.

Loop length with positive feed: Even is positive feed is used, problems can sometimes arise in maintaining loop-length control. Lack of care in controlling yarn tension. Failure to control this could lead to the development of very high tension and could cause one or both of two things to happen: - increase in yarn breaks and machine down time yarn slippage through the positive feed High yarn tension can arise from: - incorrect threading up or dirt and fluff in the yarn path - i.e. poor house keeping

Inspection of the knitting head: Ensure that the needle detectors are correctly positioned and in working order. Ensure that lint dispersion devices, if fitted, are functioning. Fiber 'fly' should be carefully controlled. In some cases it may be advisable to encase machines in polythene 'tents' to prevent 'fly' migration between machines. Ensure that oilers, if fitted, are functioning correctly.

Checking machine speed: Excessive machine speed for certain yarns can result in high yarn tension and yarn breakage.

Checking the revolution counter: Correct functioning of the revolution counter ensures the accurate control of piece weights and the correct recording of machine running times for wages payment purposes. The following checks are suggested: - Faults to seek: - Check for uneven fabric - the result of irregular yarn or faulty yarn run-in rates. Check patterning of colored jacquard fabric. Ensure that the correct take down tension and stretcher board dimensions are used.

Ensure that stretcher board and take down rollers are not causing snagging, undue creasing or fabric bowing. Inspect fabric for excessive oil stains caused by incorrect setting of automatic oil feed or by leaking oil reservoirs. Ensure fabric is lint and 'fly' free - poor cleaning methods or setting of machines can result in fiber migration between machines. This can involve an expensive burling operation at a later stage.

Conclusions:

From the work developed it is possible to draw the following conclusions. The controlling and scheduling areas are underdeveloped (considering the visits made) in the knitting industry as compared to other industries (e.g. automotive, and electronics) where it is possible to see state of the art solutions implemented. Companies are usually using in-house, developed solutions, which  are tailored to the needs and the processes involved in the planning and scheduling activities, although tailored made solutions are a good way of responding to real world every day needs of a company, the fact that these are not based on scientific understanding of the system, will prevent from reaching an optimal or best possible result, as well as will impair the long term view of business and industry evolution.

References:

R. Marks, F.T.I., Principle Lecturer, Bolton Institute of Technology & A.T.C. Robinson, M.Sc.Tech., F.T.I., Former Head of the Department of Textiles, Bolton Institute of Technology, The Textile Institute Manchester, 1976. Principle Of Weaving, pages 1 & 8.

Billie J. Collier, University of Tennessee & Phyllis G. Tortora, Queens College. Understanding Textiles, (Sixth Edition), pages 279,280,281 &282.

. http://www.bbtex.com/textiledictio nary, Bbtex.com, August 23.

 http://www.dyeingmaster.com/newsviews/page3.

http://www.karlmayer.de/english/index.html, KARL MAYER Textile maschinenfabrik GmbH, August 22

. Knitting Technology (1999) “ITMA’99 – Innovations for Knitted Fabric Finishing”, Knitting Technology, 21 (5), 30-

 http://www.krantz-textil.com/PDF/0001de.pdf, August 2235.

http://www.krantz-textil.com/PDF/0003e.pdf, August 22.

http://www.sci-pak.org/LinkClick.aspx?fileticket=FrVfDlejgjE=&tabid=76