1. Management of Quality in Knitting Part 1: Fabric Appearance & Knitting Efficiency
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2. Fabric Appearance is influenced by Fibre Quality Yarn Type
Count Variation & Evenness
Imperfections & Faults
Twist Variation
Hairiness
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3. Fibre Properties The two most important are Fibre Fineness
- average linear density
Fibre Maturity
- relative degree of thickening
of the fibre wall
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4. Micronaire Value is a function of Fineness and Maturity
indicates fibre specific surface area
is governed by
Fibre Perimeter (surface area)
Cell Wall Thickness (amount of cellulose)
indicates dyeing performance
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5. Micronaire & Dyeing Efficiency
C.I. Direct Red 81 : 1% o.w.f.
Colour depth K/S 90 80 70 60 50
Nineteen different cottons
US cottons
African cottons
Micronaire Value
2.0
3.0
4.0
5.0
2.5
3.5
4.5
5.5
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6. Barré in Weft Knitted Fabrics
due to variation in Micronaire
Source: Uster® Technologies AG
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7. Effect of Micronaire Fibre Micronaire affects Colour Yield
Cost of Dyeing
Uniformity of Dyeing
NEVER MIX YARN DELIVERIES
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8. Yarn Count Variation within and between packages, can cause Stripes
Bars
Streakiness
across the fabric width
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9. Variation Within Packages
Source: Uster® Technologies AG
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10. Variation Between Packages
Source: Uster® Technologies AG
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11. USTER® World Statistics 2007
Count Variation CVcb% : Ne 30
between bobbin variation
50%
25%
combed ring
~1.5
~1.1
carded ring
~1.6
~1.2
carded rotor
~0.9
ISO 2060
Source: Uster® Technologies AG
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12. Mass Variation (Yarn Irregularity)
within package variation causes
all-over effects
moiré effects
cloudiness
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13. Periodic Mass Variation
Source: Uster® Technologies AG
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14. USTER® World Statistics 2007
Mass Variation CVm% : Ne 30
measured on bobbins
50%
25%
combed ring
~12.3
~11.4
carded ring
~15.2
~14.3
carded rotor
~14.9
~13.8
CV% = 1.25 x U% (approx)
Source: Uster® Technologies AG
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15. Yarn Imperfections are defined as Thin places (-50%)
Thick places (+50%)
Neps (+200%)
can cause
Blemishes on fabric surface
White specks in dyed fabrics
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16. Thin Places
Source: Uster® Technologies AG
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17. Thick Places
Source: Uster® Technologies AG
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18. Fibre Nep
Source: Uster® Technologies AG
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19. Seed Coat Nep
Source: Uster® Technologies AG
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20. Biological Nep Undyed white specs caused by
clumps of immature (dead) cotton fibres
Low magnification
High magnification
Source: Uster® Technologies AG
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21. Neps
Source: Uster® Technologies AG
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22. USTER® World Statistics 2007
Imperfections : Ne 30 (50% level)
measured on bobbins
Thin
Thick
Neps
carded rotor
~28.5
~116.2
~30.4
carded ring
~11.9
~191
~232.8
combed ring
~0.9
~20.3
~36.7
NB For Rotor Yarns Neps +280%
Source: Uster® Technologies AG
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23. Classimat Defects are classified according to length & diameter
Source: Uster® Technologies AG
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24. Classimat Defects Exceptionally long thick and thin places cause
Periodic stripes
Blemishes
Needle damage
holes
needle lines
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25. Classimat Defects Classimat defects are removed during
winding & clearing
according to a clearing profile
A3, B3, C2, D1 profile
will remove the most serious faults
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26. Hairiness and Twist Variation is the problem Surface appearance
Abrasion resistance
Colour variation
Stitch clarity
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27. Effect of Difference in Twist
Band of “rogue” yarns with high twist
Source: Uster® Technologies AG
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28. USTER® World Statistics 2007
Hairiness : Ne 30
measured on bobbins
combed ring
carded ring
carded rotor H S
4.6
1.0
5.0
1.2
4.1
1.1
5.8
1.4
4.7
1.3
50%
25%
NB measurements on packages may be higher
Source: Uster® Technologies AG
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29. TESTEX Twist Statistics 1997
Twist Variation CV%: Ne 30
measured on bobbins
50%
25%
combed ring
~3.3
~2.9
carded ring
~3.5
~3.0
carded rotor
~2.8
~2.3
ASTM D Untwist-Retwist
Source: Testex
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30. Hairiness and Yarn Type
Combed yarns less hairy than carded
Rotor yarns less hairy than ring
Rotor yarns develop less hairiness
during wear and laundering
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31. Knitting Efficiency Can be affected by Strength Uniformity
Irregularity
Imperfections
Faults
Fibre Fly
Friction
Twist Liveliness
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32. Strength Uniformity Average strength is usually good enough
Variation is the key
weak places cause the problems
Elongation must be adequate
at least 5% extension at break
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33. USTER® World Statistics 20077
Yarn Strength : Ne 30 (50% level)
measured on bobbins
cN/tex
CV%
El%
carded rotor
~12.1
~8.7
~5.8
carded ring
~17.8
~8.0
~5.95
combed ring
~17.2
~7.3
~5.1
Source: Uster® Technologies AG
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34. Yarn Uniformity Slubs and Knots cause Needle damage Fabric holes
Yarn breaks
Yarn should be properly cleared
Spliced yarn better than knotted
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35. Can reduce knitting efficiency
Fibre Fly
Can reduce knitting efficiency
by up to 25%
Control is Important
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36. Amount of Fibre Fly Depends on Fibre quality Yarn structure
Twist multiple
Yarn finishing
Moisture content
Yarn friction
and, especially, the speed of knitting
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37. Fibre Fly: Effect of Yarn Construction
Carded ring, 23 mm
Fibre Fly g / Kg yarn
2.2
1.8
1.4
1.0
0.6
0.2
Combed ring, 25 mm
Combed ring, 28 mm
Carded OE rotor
Twist Multiple
2.8
3.2
3.6
4.0
4.4
4.8
5.2
Source: ITV Denkendorf
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38. for efficient knitting
Yarn Friction
Large tensions can be generated
because of friction
Low Friction is essential
for efficient knitting
Coefficient of friction against steel
must be below 0.2
Knitting yarns must be waxed
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39. Friction and Yarn Tensionq T2 T1
T2 = T1 . e mq
knitting zone
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40. Wax Application & Coefficient of Friction
Combed cotton ring yarns
Coefficient of Friction
0.4
0.3
0.2
0.1
Wax add-on %
0.2
0.4
0.6
0.8
Source: Savio
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41. Yarn Waxing Optimum level Uniform application Wax quality Yarn storage
Easy removal
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42. High Yarn Twist Liveliness Causes
Snarling
Fabric Faults
Yarn Breaks
Good yarn control required
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43. Minimising Knitting Faults
Yarn Quality
Machine Set Up
Fibre Fly
Machinery Maintenance
Good Housekeeping
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44. Yarn Quality Yarns properly waxed Damaged cones Yarn storage
temperature & moisture content
Yarn identification
no mixing of yarn lots
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45. Yarn Input Tension Should be monitored using
appropriate instrumentation
Excessive tensions can cause
Schmidt ZEF
stitch distortions
fly generation
yarn breaks
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46. Yarn Input Tension Excessive tensions can be caused by
badly adjusted or sticking stitch cams
damaged yarn packages
creeling
faulty waxing
faulty feeding units
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47. Fibre Fly is generated at Yarn package Yarn guide elements
Yarn furnishing installation
Knitting point
25% of all knitting faults
can be attributed to fibre fly
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48. Control of Fibre Fly Enclosed creels to humidify and filter air
Feeder tubes
Yarn speed
Regular cleaning
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49. Control of Fibre Fly Enclosed creel with lint filters and tube feeds
Source: Memminger-IRO
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50. Effect of Yarn Speed on Fibre Fly
Carded 30 Ne
Fibre fly g /Kg yarn
2.8
2.4
2.0
1.6
1.2
24g, 30", 10 rpm
24g, 30", 50 rpm
Yarn speed m/min 50
150
250
350
450
Source : ITV Denkendorf
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51. Knitting Faults Holes Stains Missed stitches Needle lines Sinker lines
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52. Control of Knitting Faults
Yarn detectors
Memminger-Iro: UFW
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53. Control of Knitting Faults
Yarn detectors
Knot & Slub catchers
Memminger-Iro: MPF_L
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54. Control of Knitting Faults
Yarn detectors
Knot & Slub catchers
Needle detectors
Memminger-Iro: Needle detector
Latch openers
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55. Control of Knitting Faults
Yarn detectors
Knot & Slub catchers
Needle detectors
Latch openers
Fabric fault detectors
Memminger-Iro: LMW-3
Record and analyse faults, identify sources
e.g. yarn supply or machinery maintenance
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56. Preventive Maintenance
Regular cleaning of machines
Clean working areas
Efficient lubrication systems
Regular flushing of needle bed
Checks for wear and rough places
Service positive feed units
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57. Preventive Maintenance
needles and sinkers
using high quality spares
Regular proactive replacement of
Ad hoc replacement inevitably means
variations in quality and efficiency
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58. STARFISH Workshop