Tuesday 30 December 2008

Degree of polymerisation of some fibres

Fibers and DP ( Degrees of Polymerisation)

Nylon 6 -120
Nylon 6,6-200
Polyester (PET)- 100
Polyacrylonitrile > 2000
Viscose Rayon- 150-350
Polynosic- 700-1100
Cotton- 4000-10,000
Wool- 60,000-100,000

Thursday 18 December 2008

Major Warping Defects

On Beam Warpers

1. Lapped Ends

The yarn's broken end is not tied to its end on the warp beam and overlaps the adjacent yarn. The bem is not properly braked, the signal hook fails to operate.

2. Bulges and yarn ends drawn from the midddle

The broken end has not been correctly found and pieced up to the adjacent yarn.

3. Broken ends on the beam

It is due to reasons mentioned in point 2. A group of ends is broken and tied as a bunch or worked-in with overlapping

4. Incision of yarn at the butts of the warp beam or slackness of extreme yarns

The reed is improperly set with respect to the warp beam flanges; deformation of the warp beam flange

5. The number of yarn ends of the beam is excessive or insufficient

Incorrect number of bobbins in warping

6. Conical winding on the beam

Incorrect load applied by the pressure roller

7. Slacks and irregular yarn tension

Improper threading of the yarn into the tension devices; ejection of yarn from under the disc of the yarn tensioning device, yarn tension devices of poor quality

8.Frequent yarn breakages at the beam edges

Burrs and nicks on the surface of the warp beam flanges

9. Improper length of warping

Malfunction of the counter, and the brakes of the measuring device and warp beams

10. Coarse Knots

Manual tying-up

11. Loose yarn winding

The pressure roller is lightly pressed against the warp roller

12. Working -in of fluff, oily ends and yarn of different density

Careless work of the operative, creeler and oiler.

13. Bulgy winding on the warp beam

Irregular laying of yarn ends in the reed, missing a dent and placing two ends in the adjacent one.

Wednesday 17 December 2008

Specific Gravity of Fibres

Acetate= 1.33
Camel hair=1.31
Silk Weighted= >1.60
Silk - B. Mori (raw)= 1.33
Silk Tussah=1.32
Wool= 1.31

shrinkage norms for 14.5 oz. denim

Length wise shrinkage--> after 3rd wash---> -1.2% to -2.8%
Width wise shrinkage --> after 3rd wash--> -2.5% to -3.5%

Hard waste % in denim industry

Hard Waste % in Denim Industry

Warping--> 0.7%
Unsized Yarn--> 0.4%
Sized Yarn--> 0.6%
Fringe--> 1.7%

All these  above are percentage of Hacoba Production

Knotting + Reknotting waste --. 0.7%
Extra ends--> 0.7%

All the above are as percentage of loom shed production

Total Hard Waste= 4.8%

Tuesday 16 December 2008

Impact of rotor machine variables on yarn quality

Impact of Rotor machine variables on Yarn Quality

On increasing rotor speed

1. Centrifugal force (g.tex) increases

= (w^2 x 0.981)/20000, w= pi x D x N
where D= Rotor dia in meters
N= rotor rev/second

so there is better fiber consolidation and better strength

2. Combing roll efficiency will reduce , fibres get deposited in rotor groove in bunches and not in single file and so strength reduces.

3. Hooks will get less time to straighten

4. Number of wrapper fibers will increase

5. Also yarn elongation decreases at higher rotor speed

On increasing rotor diameter

a. % wrapper fibres = l x 100/ pi x D
where l= effective length of fibres used
so as D increases, % reduces so strength increases

b. No of doublings inside the rotor
pi x D x TPI

so evenness and imperfection reduces, strength increases

c. Reduction in spinning in coeficient at higher rotor diameter. This leads to weaker yarn.

d. Higher power consumption

PC ( Watts) = K n^2.5 D^3.8

n--> rotor speed ( rev/min)
D--> rotor dia in mm
k--> a constant

e. Yarn elongation decreases at higher rotor diameter

On Increasing Draft

Increasing draft will increase fibers breakage due to increase in the value of carrying factor (ie. no of points per fibre) optimum should be 120-150

Combing roll speed should be around 6000-8000 rpm

Design of Doffer tube

Grooved tube permits yarn to be produced at lower twist factor but poor fiber orientation and high short term variability.

Affeect on Twist

Higher twist: Elongation increase, and abrasion decreases

Sunday 14 December 2008

Open End Yarn Properties Compared with Ring Yarn

Quality Characteristics of OE yarn as compared to ring yarn

Production- Increased 3-3.5 times
Package size- Increased 20 times
Tex Range- 20-60
Twist- 10-15% higher
Average Strength- 15-20% weaker
Variation in Strength- Less
Extensibility- 10% higher
Work of Rupture- same
regularity- 10-20% better
count variation- better
appearance- more uniform
bulkiness- sp. volume increased by 10%
hairiness- 20-40% less
cleanliness- better
nappiness- fewer neps
yarn faults- decreased by 80%
resistance to abrasion- 20-30% better
handle- harsher
structure- different
fiber blending- much better
take up of size- better ( less size required)
take up of dyes- better ( vivid colors)
End breaks in spinning- reduced 75%
Fly liberation- less

Characteristcs of OE yarn in use and of fabric made from them- comparison with ring spinning

Yarn made from OE spinning

End breaks- reduced by 50%
Knots (after winding)- decreased by 15-17/kg
warp breaks in weaving- decreased by 70%
weft breaks in weaving- decreased by 25%
tensile strength- reduced
tearing strength- reduced
bursting strength- reduced
appearance - more uniform
barring- much much better
cover- 10% better
cleanliness- better
neppiness- fewer neps
resistance to abrasion- 5-7% better
handle- harsher
thermal insulation- 10-15% better
air permeability- 15-25% better
Take up of dyes- better ( vivid colors, clear definitions)
Absorption of water- much better
shrinkage- same
raising- easier and more uniform

Friday 12 December 2008

Common Problems in Pigment Printing

Click here for common problems in pigment printing and their causes.

Thursday 11 December 2008

Jute Manufacturing Process

Please see the following link for jute manufacturing process

Tuesday 9 December 2008

Chemical Solubility Test for fiber identification

Please see here for Chemical solubility test for fiber idenfication.
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