Tuesday, October 28, 2014

QUALITY ASSURANCE PROCEDURE OF TEXTILES

Introduction:

The Quality assurance Department is assigned to maintain consistently uniform quality of the material in process and various stages of its manufacturing.

Quality of Raw Material:

1. Cotton

2. Water

3. Dyes & chemicals

Cotton:

Quality of raw cotton selected by spinner:

Staple length, fiber fineness, fiber strength, fiber maturity, fiber cleanness, fiber elongation etc.

Sources of raw material:

1. CIS cotton (commonwealth of independent states ; Uzbekistan, Kazakhstan, Tajikistan origins)

2. Indian cotton

3. BCI cotton: it is a long term multi-stakeholder initiative that develops and promotes good firm practices, reduce water and chemical use to reduce the impact of nature and environment.

Raw Cotton Parameter:

CIS cotton:

Staple length: 28-32

MIC value: 3.3-4.6

Indian cotton:

Staple length: 26-30

MIC value: 4.0-4.9
Water:
Standard water quality for dye house:

                            Parameter
            Permissible concentration
                              Color
                                Color less
                             Smell
                             No bad smell
                     Water Hardness
                                <5 ppm
                        PH value
                                7-8(Neutral)
                        Dissolve solid
                                 <1 ppm
                          Inorganic salt
                             <500 ppm
                            Iron (Fe)
                              <0.1 ppm
                        Manganese (Mn)
                               <0.01 ppm
                          Copper (Cu)
                              <0.005 ppm
                         Nitrite (NO3)
                               <50 ppm
                          Nitrate (NO2)
                              <5 ppm

Quality of Dyes & chemicals:

Ionic nature of dyes, Molecular size of dyes, Diffusion of dyes, Fastness Properties, Versatility of Shade, Concentration of Chemicals.

Quality control and Assurance:

In spinning:

List of testing equipment:

USTER HVI Spectrum:

To measure MIC, Maturity, SCI, Length, Uniformity, Strength, Short Fibre Index, Elongation, Moisture, Rd, +b, Color grade, Trash Content, Trash Area, Trash Grade, UV.

Length & Strength

Working Principle

· For length— Photo-electric cell or Electro-optical method

· For strength—Pneumatic or Mechanical break

· Fibro-comb and Fibro-sampler are used to prepare sample. A test sample is prepared with Fibro-comb by Fibro-sampler.

Mean length = mean fiber length

Upper half mean length = mean length by weight of the longer 50% of fibers

Uniformity Index = length uniformity of the fibers.

Strength [g/tex]: Breaking force of the fiber bundle divided by fiber fineness

Micronaire

Color & trash

The color of cotton is determined by the degree of reflectance (Rd) and yellowness (+b). Reflectance indicates how bright or dull a sample is, and yellowness indicates the degree of color pigmentation.

Trash is a measure of the amount of non-lint materials in the cotton, such as leaf and bark from the cotton plant.

Uster AFIS Pro:

Neps
Neps are determined as entanglement of fibres. They are formed under mechanical treatment.
The seed coat neps are fragments of cotton seeds with remaining fibres. They are mainly produced in ginning when the fibres are separated from the cotton seeds.


Characteristics
Unit
Description
Weight
[g]
Sample weight
Nep
[μm]
Mean nep size
Nep
[Cnt/g]
Number of neps per gram
SCN
[μm]
Mean seed-coat nep size
SCN
[Cnt/g]
Number of seed-coat neps per gram

SFC (n,w): Short fiber content, percentage of fibers shorter than ½ inch or 12.7 mm

UQL (w): Upper quartile length = length exceeded by 25% of the fibers

Fiber length is measured according to staple diagram:


            Fig: Staple diagram


Trash
Characteristics
Unit
Description
Total
[Cnt/g]
Total number of particles per gram
Mean size
[μm]
Mean particle size
Dust
[Cnt/g]
Dust particles per gram (<500 μm)
Trash
[Cnt/g]
Trash particles per gram (>500 μm)
V.F.M.
[%]
Visible foreign matter

Uster Tester :
1. Thin -50% /km

2. Thick +50% /km

3. Neps +200% /km

4. U%

Quality parameters :

a) Unevenness (U%, CV % at different cut length)

Cut length –

ü For sliver : 20mm

ü For roving : 12mm

ü For yarn : 8mm

b) Imperfections

ü Thin place/km: at -30%, -40%, -50% &- 60% sensitivity

ü Thick place /km: at +35%, +50%, +70% & +100% sensitivity

ü Neps/km: at +140%,+200%,+280%&+400% sensitivity

c) Hairiness (at different cut length and CV% of hairiness)

Irregularity U%: It is the percentage mass deviation of unit length of material and is caused by uneven fiber distribution along the length of the strand

a) Index of Irregularity: Index of irregularity expresses the ratio between the measured irregularity and the so-called limiting irregularity of an ideal yarn.

Imperfection Index= Thick (+50%)/km + Thin (-50%)/km + Neps (+200%)/km

Hairiness:

The hairiness H corresponds to the total length of protruding fibers divided by the length of the sensor of 1 cm. The hairiness is, therefore, a figure without a unit

Bale Management

Bale management is an important task of quality department. It may be defined as the choice of cotton bales according to the fiber characteristics in order to achieve acceptable & economical processing conditions & a consistent yarn quality.

In knitting section:

QUALITY ASSURANCE SYSTEM:

All rolls are kept in front of the inspection m/c time to time and are inspected over the grey inspection m/c visually in a pre-set speed against light. For any major or minor faults like thick-thin, barre marks, fall out, contamination, fly, holes, oil lines, needle lines, slubs, etc are recorded in grey inspection report to classify the fabric based on the four point system.

Collar & cuff are inspected visually under light box, any major & minor faulty collar/cuff like having wrong ply, hole, needle lines, slubs, wrong design, first line problem etc properly counted and recorded.

FOUR POINT GRADING SYSTEM

FOUR POINT GRADING SYSTEM
Size of defects
Penalty
3 inches or less
1 point
Over three inch but not 6 inch
2 point
Over 6 inch but not 9 inch
3 point
Over 9 inch
4 point








QUALITY Pts / 100 square Yards = (Total point * 100*0.9144*36)/ [Inspected Fabric Length (m)* Fabric Width (inch)]

Quality inspectors seal on the fabric rolls as ‘CHECK-1’, ‘OK’ & ‘REJECT’ as according as quality classification.


Quality Control system mainly two types:

1. Online QC

2. Offline QC


1. Online QC

Online quality control comprises with the raw material quality control and the process control.

Raw material control:

As the quality of product depends on the raw materials quality so we must provide the best quality raw material with an economical consideration. The fabric must be fault-free, with proper absorbency, whiteness as per requirement of the subsequent process. The Grey inspection report gives the condition of the raw fabric.

Process control:

The method chosen for the process must be provided with the necessary accurate parameters. Here the specific gravity, water level, residual hydrogen per oxide etc. at each stage is checked.

Laboratory:

Lab is the important part of a textile industry. Higher precision in a trial can aid easily to achieve the goal of the organization. Before bulk production a sample for the approval from industry is sent to the buyer. As per the requirement of the buyer the shade is prepared in a lab considering the economic aspects.

Lab line:

1. Standard sample: It is obtained from buyer. The sample is measured by the CCM to get the recipe.

2. Lab trial: Getting the recipe the lab officer produce lab trial and match with standard according to buyer requirement.

2. Offline QC

Off-line tests: All the Offline tests for finished fabrics can be grouped as follows:

A. Physical tests

B. Chemical tests

Physical Tests:

Ø GSM test

Ø Shrinkage test

Ø Spirality test

Ø Tensile strength

Ø Abrasion resistance

Ø Pilling resistance

Ø Button Strength Testing

Ø Crease resistance

Ø Dimensional stability

Ø Bursting strength test

Chemical Tests:

Ø  Color Fastness to washing.
Ø  Color Fastness to light.
Ø  Color Fastness to heat.
Ø  Color Fastness to Chlorinated water.
Ø  Color Fastness to water spotting.
Ø  Color Fastness to perspiration.
Ø  Color Fastness to Sea-water.
Ø  Fiber analysis.
Ø  PH test.
Ø  Spray test (water repellency).

Following faults are found in (off-line quality control) the grey fabric:

Problem
Reason
Remedy
1.     Hole
Broken needle head
Change the needle
2.     Missing yarn
Missing of one end of double yarn
Careful observation and instant stop when fault found
3.     Needle line
Bent needle latch
Replace the needle
4.     Thick & thin yarn
Yarn fault
Replace the yarn cone to a more uniform yarn cone
5.     Slubs
Yarn fault
Replace the yarn cone to a more uniform yarn cone
6.     Drop needle
Needle fail to receive the yarn while knitting, needle missing
Reset the needle
7.     Barrie mark/patta
Irregular tension of take down roller
Adjust the take down tension or synchronize the take down speed with knitting
8.     Pin hole
Due to missing stitches or loop
Concentrate on needle and latch
9.    Line pin star
Due to missing several loops at a course for broken needles & sinkers
The broken needles & sinkers must be replaced.
10.  Sinker mark
Cause for broken sinker or improper setting of sinkers.
The broken sinkers should be replaced; the correct setting of sinkers.
11.   Lycra out
Tear off the lycra during knitting of fabric.
Awareness about the lycra yarn during knitting.
12.   Filament problem
Presence of filament yarn i.e. lycra without knitting for missing of needle.
Proper setting of needles & feeders.
13.    Loop missing

Cause for miss of yarn
Ensure yarn for every feeder & needle.
14.     Crease mark
Irregular tension of take up roller
Adjust tension of take up roller with cylinder speed.
15.     Oil line
Improper lubrication
Proper lubrication
16.   Fly contact
Fly coming from the adjacent m/c
Separate one m/c from others
17.    Oil stain
Dirty m/c and improper handling of fabric
Proper lubrication and clean m/c


Dyeing Faults:
Dyeing faults are given below:

1. Patchy Effect:

Reason:

-Entanglement of fabric

-Faulty injection of alkali

-Faulty color addition

-Due to hardness of water

-Due to impure salt solution

Remedies:

-By partial or full stripping of dyed fabric.

2. Roll to roll variation / Meter to meter variation:

Reasons:

-Yarn lot to mix

-Faulty heat setting.

-Faulty m/c speed

3. Dye-stain:

Reasons:

-No dissolved of caustic particle in bath

Remedies:

-By partial or full stripping

4. Crease Mark:

Reasons:

-If pump pressure & reel speed is not equal

-Due to high speed m/c running

5. Rub Mark:

Reasons:

-Due to reel cranking

-Due to sharp point of nozzle

-Due to sharp delivery roller

6. Nozzle to Nozzle Variation

Reasons:

-Pump pressure & reel speed is not equal.

Rejection criteria for body & Rib:
Following table shows common body & rib faults and response by grey inspection section.

No.
Faults
Response
1.
Needle marks
Major needle line is rejected.
2.
Stripe
  Major needle line is rejected.
3.
Barre marks
Rejected
4.
Slubs
1 point 
5.
Wrong design
Rejected
6.
Pin holes
1 point
7.
Fly & contamination
Acceptable for color but not for white
8.
Sinker marks
Do
9.
Uneven tension
Discuss with manager
10.
Missing yarn
Use 4 point
11.
Crease line
Do
12.
Uneven tension
Discuss with manager
13.
Oil stripe/line
Do
14.
Thick-thin place
Rejected


Rejection criteria for collar & cuff: Following table shows common collar & cuff faults and response taken by grey inspection section.

No.
Faults
Response
1.
Wrong ply
Reject
2.
Hole
Reject
3.
Needle line
Reject
4.
Slubs
Reject
5.
Wrong design
Reject
6.
Wrong tripping
Reject
7.
Fly & contamination
Acceptable for color but not for white
8.
First round problem
Reject
9.
Uneven tension
Discuss with manager
10.
Missing yarn
Reject
11.
Crease line
Reject
12.
Rust line
Reject
13.
Oil stripe
Reject
14.
Thick-thin
Reject
15.
Wrong tube
Reject

Different defects of fabric found in Garments industry:

• Bad selvedge

• Broken ends

• Broken pattern

• Broken picks

• Holes in clothes

• Mildew

• Mixed weft

• Reed marks

• Shading

• Shuttle marks

• Stains

• Rough surface cloth

• Thick and thin place

Quality Control of Sewing Thread:

Following Features of Sewing thread are considered-

• Thread Construction/Ticket number

-Thread count

-Thread Ply

-Number of twist

-Thread balance

-Thread Tenacity

-Thread Elongation

• Sewability

• Imperfection

• Thread finish

• Thread color

• Package Density

• Winding

• Yardage

Quality Control in Zipper:

Following factors are considered-

• Proper dimension of zipper

• The top and bottom end should correctly sewn

• The tape and color of zipper should be uniform

• Slider has to be locked properly

• The slider should move properly

Quality control in sample section:

• Maintaining buyer Specification standard

• Checking the sample and its different issues

• Measurements checking

• Fabric color, gsm, Fastness etc properties required checking

• SPI and other parameter checking

The various Steps of Garments manufacturing where in-process inspection and quality control are done are mentioned below-

• In- Marker making section

• Inspection in fabric spreading section

• Inspection in fabric cutting section

• Inspection in fabric sewn section

• Inspection in pressing & Finishing section

Quality control in Marker making:

• To check notch or drill mark

• Fabric width must be higher than marker width

• Fabric length must be higher than marker length

• Matching of grain line

• Check pattern size and dimension

• Matching of check and stripe taking into consideration

• Considering garments production plan

• Cutting table length consideration

• Pattern direction consideration

Quality control in Fabric Spreading:

• Fabric spreading according to correct alignment with marker length and width

• Maintain requirements of spreading

• Matching of check and stripe

• Lay contains correct number of fabric ply

• Correct Ply direction

• To control the fabric splicing

• Tension control

Quality control in fabric Cutting:

• The dimension of the pattern and the cut piece should be same and accurate

• Cut edge should be smooth and clean

• Notch should be cut finely

• Drill hole should made at proper place

• No yarn fraying should occur at cut edge

• Avoid blade deflection

• Maintain cutting angle

• More skilled operator using

Quality control in sewing section:

• Input material checking

• Cut panel and accessories checking

• Machine is in well condition

• Thread count check

• Special work like embroidery, printing panel check

• Needle size checking

• Stitching fault should be checked

• Garments measurement check

• Seam fault check

• Size mistake check

• Mismatching matching of trimming

• Shade variation within the cloth

• Wrong placement of interlining

• Creased or wrinkle appearance control


No comments:

Post a Comment