1. Testing Methods
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2. Testing Procedures Must be Consistent Reliable Reproducible
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3. Conditioning Standard conditions: 20 °C and 65% RH
Measurements affected by moisture content
Fabric weight
Courses & Wales
Yarn count
Stitch Length
Strength
Shrinkage
STARFISH assumes standard conditions
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4. Relative Humidity & Moisture Regain
Scoured cotton at 25 °C 24 20
Absorption 16
Desorption
Moisture Regain % 12 8 4 20 40 60 80
100
Relative Humidity
Source: Shirley Institute 1930
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5. Yarn Testing Yarn quality is a key control factor
Spinners do extensive testing
Develop relationship with spinner
Ask for his test data
Learn what they mean
Knitter should at least monitor yarn count
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6. Test Methods for Yarns Count : ISO 2060 ASTM D 1907 Twist :
Friction :
ASTM D 3108
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7. Yarn Count 20 skeins per sample 1 skein per package 1 package per box
Number of samples
established supplier : 1
new supplier : 5
CV% within and between samples
Use Quality Control Charts
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8. Yarn Twist a a Difficult test - should be automated
Spinner's data may be more reliable
... especially for OE rotor yarns
Use the same samples as for count
= turns per inch / sqrt (Ne) e a
= turns per cm . sqrt (tex) a
tex
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9. Yarn Friction Should not be a problem ... with a good supplier
New suppliers
... should be checked
Friction coefficient
... between 0.10 and 0.15
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10. Other Yarn Testing Regularity, Evenness, Hairiness visual assessment
blackboard wrappings
ASTM Grade standards
knitting test
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11. Knitting Test Small diameter single-feeder machine
Include standard yarn
fabric appearance
dyeing behaviour
neps / specks
spirality / barré
Lawson-Hemphill: FAK Lab Knitting Machine
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12. Knitting Test Small diameter single-feeder machine
Include standard yarn
fabric appearance
dyeing behaviour
neps / specks
spirality / barré
Source: Uster® Technologies AG
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13. Fabric Testing Routine Quality Control
check process control systems are working correctly
tests required by customer
Minimum testing because product performance is guaranteed by correct design and precise process control
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14. Fabric Testing Quality Assurance check new yarn batches OK
check instrumentation OK
check testing procedures OK
calibrate process machinery
More detailed testing because this is how we ensure that control systems are working properly
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15. Fabric Testing STARFISH test methods Stitch Length Yarn Count
Course & Wale densities
Weight per unit area
Shrinkage
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16. Stitch Length Technique
Usually measure consecutive courses
Identify different tape drives
Identify different courses in pattern
Identify different yarns
All technicians using the same technique
NB. Accurate marking, Visible wales
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17. Measuring Stitch Length
100 wales
inside marks
Cut inside marks
for exactly 100 wales
at least 2 specimens
at least 10 courses
at least 5 repeats
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18. Measuring Stitch Length
Sodemat: Maillemeter 3: LFA
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19. Measuring Stitch Length
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20. Measuring Stitch Length
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21. Yarn Count In conjunction with Stitch Length cut inside the marks
remove 100 threads
repeat at least twice
calculate total length in metres
determine weight in grams
tex = Weight / Length
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22. Course & Wale Density are Key Process Control Parameters
Courses are counted along a wale
Wales are counted along a line
perpendicular to the wales
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23. Courses & Wales Technique
Identify a specific point in the loop
Establish a technique
for estimating part - loops
Estimate the last stitch
to at least one quarter of a loop
Make use of the structural cell
All technicians - identical technique
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24. Counting Loops cm Choose a specific place in the loop1 cm
Choose a
specific place
in the loop
to start counting
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25. Counting Loops 3 Estimate the fraction of a repeat in the last
part - loop
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26. Structural Knitted Cell
Use with complicated constructions
when some courses are not visible
e.g. Double Crosstuck
One cell equals four courses
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27. Course and Wale Density
Accurate determination of courses and wales
Can reduce the need for routine shrinkage testing
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28. Measured vs Calculated Shrinkage30
Each data point is the mean of 5 replications 25 20
10 fabric types 20 test procedures 15
Calculated Shrinkage 10 5
y = x R2 = 0.95 -5
-10
-10 -5 5 10 15 20 25 30
Measured Shrinkage
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29. Area Weight
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30. Area Weight NOT a Key Process Control Parameter
Important to customer and producer
fabric yield and cost
loss of weight in preparation
Accurate determination needs technique
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31. Weight Measurement Problems
Weight is affected by moisture content
… errors of up to ~ 4 %
Circular cutters not always accurate
… if in doubt check area of specimen
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32. Area Weight Technique Avoid distortion errors
Change blades & boards regularly
Cut one specimen at a time
Cut at least three specimens
Allow specimens to relax
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33. p Area = * a * b / 4 a = 11.3 b = 11.3 area = 100.3 a b 12 10 8 6 4 2
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34. p Area = * a * b / 4 a = 10.8 b = 11.5 area = 97.5 error = 2.5 % a b6 8 10 12 b a
a = 10.8
b = 11.5
area = 97.5
error = 2.5 %
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35. Spirality Direction & Sign
Negative
Positive S Z
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36. Spirality Measurement
wale line
spirality angle 90
course line
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37. Spirality Technique Mark a wale line Mark a course line
Place protractor at intersection
Measure the angle
between the wale and the perpendicular
Repeat at least four more times
Use an eyeglass when marking lines
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38. Shrinkage Testing NOT a Key Production Control Parameter
Not a very reliable parameter
Try to eliminate from routine testing
May be needed for calibration purposes
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39. Shrinkage Measurement
ISO 3759 1 2 3
Single layers, square 1
Square template 2
Align with the wales 3
Clear datum points
Remeasure distances
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40. STARFISH Reference Relaxation
1. Full wash programme at 60 °C
2. Tumble dry (completely dry)
3. Rewet on rinse cycle
4. Tumble dry (completely dry)
5. Repeat 3 and 4 three more times
6. Condition
Fabric is now in the "Reference State"
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41. Tumble Dryer Exhaust Temperature
Plain Jersey, Mercerised 70 60 50
Exhaust Temperature, °C 40 30 20 40 60 80
100
Drying Time, min
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42. STARFISH Shrinkage Method
Each Sample
five specimens 70 x 70 cm
measuring area 50 x 50 cm
Each Specimen
three marks for length
three marks for width
Average all 15 measurements
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43. Routine Shrinkage Measurement
Reference method too expensive
Use the 2 : 2 : 2 Method
Two specimens
Two pairs of marks
Two cycles
Other conditions the same
Establish relationship to Reference Method
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44. Confidence Limits in Shrinkage Testing
20 different fabrics
200
400 tests
5 specimens per test
length & width shrinkages
150
Frequency
100 50
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Confidence Limit
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45. Factors Affecting Shrinkage
Specimen size
Number of specimens
Conditioning
Number of cycles
Drying conditions
Previous laundering history
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46. Specimen Size Measuring Area Standard Deviation 50 x 50 cm 0.6 to 1.1
Use 5 specimens for 50 x 50
Use 6 specimens for 25 x 25
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47. Conditioning and Length Shrinkage
Interlock, Winch Dyed 21 19 17
Average Length Shrinkage, % 15
Before Conditioning
After Conditioning 13 11 50 60 70 80 90
100
110
Total Time in Tumble dryer, min
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48. Conditioning and Width Shrinkage
Interlock, Winch Dyed 13 12 11
Average Width Shrinkage, %
Before Conditioning 10
After Conditioning 9 50 60 70 80 90
100
110
Total Time in Tumble dryer, min
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49. Effect of Test Conditions
Line drying
... generates less shrinkage
Tumble drying
... is more reproducible
Length shrinkage
... increases with number of cycles
Width shrinkage
... may reduce with number of cycles
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50. Reproducibility Typical STARFISH laboratory results Accuracy Target %
Minimum
Specimens
CV%
Courses & Wales
2.0 6
Stitch Length
0.5 6
Weight
2.0
3.0 4
Accuracy = t * CV / sqrt ( N )
t is the Student's t statistic
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51. Quality Control of Testing
Testing is expensive
It must be dependable
Systematic, random sampling
Monitor reproducibility
Internal consistency checks
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52. Internal Consistency Checks
Standard statistics
Control Charts for CV%
Calculation checks
Weight
Courses & Wales
Blind check-tests
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53. Calculation Checks When full tests have been carried out
e.g . calibration, product development
Fabric Weight is calculated from
courses, wales, tex, stitch length
Reference courses & wales from
shrinkages and as del. courses & wales
Measured and calculated values should agree
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54. STARFISH Workshop