The document discusses the significance of yarn evenness and its effect on fabric quality and production costs in the textile industry. It details how variations in yarn diameter can lead to defects in finished fabrics, inefficiencies in knitting processes, and ultimately impact profitability for manufacturers. Moreover, it emphasizes the importance of using quality specifications and instrumental grading to improve yarn evenness and manage quality-related expenses.

1. Yarn Evenness and Imperfections
By : Ravikeerthi Rao

3. YARN EVENNESS
Yarns of different quality levels result in fabrics of distinctly
different quality levels, leading to problems in processing or
variations in final value (of the fabric / garment).
These differences impact on prices and affect the costs and
profitability of both fabric & apparel manufacturer.
There is an unavoidable link between quality and cost.

4. YARN QUALITY
• Statistics tell us that yarn accounts for a major share of the total
‘quality cost’ of a garment.
• That includes not only direct price of the yarn, but also extra
costs caused by substandard quality or wrongly-specified yarns,
which may also have a knock-on economic effect through
weaving or knitting and even into dyeing and finishing.

5. YARN EVENNESS
Increased quality costs may be caused not only by wrong selection
of the yarn for a certain article but also by poor performance of the
yarn.
One of the most effective ways of managing increased quality costs
and its related implications is to provide a better quality
specification for yarns.
The most important parameter (specification) to be taken care is the
yarn evenness.

6. YARN EVENNESS
Yarn evenness is a measure of the level of variation in yarn diameter
along its length.
In other words, it refers to the variation in yarn linear density or
mass per unit length of yarn.
A yarn with poor evenness will have thick and thin places along
yarn length, while an even yarn will have little variation in mass or
diameter along length.
It is the evenness of staple spun yarn that is of concern here.
Continuous filament yarns have virtually no variation in linear
density, so, evenness is not an issue for those yarns.

7. YARN EVENNESS
Uneven fabric appearance is one of the most disturbing and most
noticeable effects in a garment.
Irregular yarns and high imperfection levels in the yarn are the
causes behind an uneven fabric appearance and to some extent, the
mass variation of fabric (GSM).
It results in a cloudy surface which is considered off-quality and
absolutely not acceptable.
By no means can this be hidden or mended once the fabric is
produced.

8. YARN EVENNESS
Effect on Productivity
The yarn defects / imperfections such as thick places, thin places,
slub, loose fluffs, etc. create difficulty during the process of knitting.
Any diameter higher than the average yarn diameter may create
problem in performance of knitting due to the insufficient space
available in between two sinkers.
In order to run a knitting machine smoothly the yarn should be of
uniform diameter though out its lengths.

9. YARN EVENNESS
Effect on Productivity ( Cntd….)
With the use of even yarn the efficiency in Weaving and / or
Knitting will be improved leading to higher productivity because of
the lower incidence of weak places. Fewer end breaks are
encountered with regular (more even) yarns.

10. YARN EVENNESS
Effect on Quality
Fabric defects and rejections are critically influenced by irregularity
of yarns.
Periodic and quasi periodic irregularities in yarn result in warp way
streaks and weft bars in woven fabrics and a non-periodical yarn
irregularity gives cloudiness in the woven or knitted fabric, leading
to fabric rejections.
Defects such as streaks, stripes, barre (moiré effect), or other visual
groupings clearly apparent to eye and are usually compounded when
the fabric is dyed or finished.

11. YARN EVENNESS
Effect on Quality ( Cntd…)
An irregular yarn will also vary in strength along the yarn.
More regular the yarn, better will be the appearance and aesthetic
value of the product. As a result, better sale value can be achieved.

12. YARN EVENNESS
Effect on Quality ( Cntd…)
Regularity contributes to a smoother feel.
In apparel and most of other textiles, smoothness is most desired
characteristic. Sale value of fabric is dependent, among other things,
on smoothness.
Other fabric properties such as abrasion or pill-resistance, soil
retention, drape, absorbency, reflectance, or luster may also be
directly influenced by yarn evenness.

13. YARN FAULTS
Effect on Quality ( Cntd…)
Faults like spinners doubles are difficult to determine in the yarn,
with the naked eye.
On the other hand, they can produce quite fatal results in the
finished product.
A spinners double in the warp or in yarn for circular knitting can
downgrade hundreds of meters of woven , or knitted fabric.

14. YARN FAULTS
Effect on Quality ( Cntd…)
Neps
•Apart from the strong influence on the optical appearance of
textile surface structures, neps from a certain size upwards also lead
to problems in the knitting machine sector.
•In woven fabrics, the second most important yarn characteristic
after yarn tenacity is the level of neps, since this adversely affects
fabric appearance
•Not only the size but also the number of neps are decisive criteria
as to whether the yarn is usable or not.

15. IMPERFECTIONS
• Imperfections referred to as frequently occurring smaller yarn
faults or irregularities.
• These can be subdivided into bellow three groups:
These are the conventional criteria that are considered in the
evenness measuring equipment.

16. IMPERFECTIONS

17. IMPERFECTIONS
•Typically, thin and thick places can be of up to one-inch length.
•Neps are typically of 3 to 10 mm length.
•Thick places exceeding the 100% limit are determined using the
Classimat method.

18. YARN FAULTS
•It is still not possible to produce a yarn without faults for various
reasons.
•Stickiness of cotton can contribute to the formation of thick and
thin places.
•Fly liberation in Ringframe department is one of the major reasons
for short faults in the yarn because of the fly gets spun into the
yarn.
•Hence it is not possible to have fault free yarn from ring spinning

19. YARN FAULTS
•Depending upon the raw material, the machinery set up,
production and process parameters, there are about 20 to 100
faults over a length of 100 km yarn which do not correspond to the
desired appearance of the yarn.
•This means that the yarn exhibits a yarn fault every 1 to 5 km.
These faults are thick and thin faults, foreign fibers and dirty places
in the yarn.

20. YARN FAULTS
It is obvious that the appearance of faults in a (grey) fabric depends
on various items:
The cross-section of the fault compared to the mean value
The length of the fault
The count of the yarn
The yarn density in the fabric
The type of fabric (weaving or knitting)

21. YARN EVENNESS
Judging the yarn evenness through visual
examination
The yarn has to be wound on black boards with help of suitable
mechanical device and compared with the standard yarn appearance
board for Grade (ASTM standard Yarn Appearance board).

22. YARN APPEARANCE BOARD WINDER

23. YARN EVENNESS
ASTM standard test method describes the yarn appearance into five
grades – Grade A, B, C, D & E.
The appearance grade of yarn is based on the composite evaluation
of several factors, such as unevenness, fuzziness, and neppiness.

24. STANDARD YARN BOARD

25. YARN EVENNESS - ASTM GRADES
Grade A:
No large neps, very few small
neps, must have very good
uniformity, less fuzziness.

26. YARN EVENNESS - ASTM GRADES
Grade B:
No larger neps, few small neps,
less than 3 small pieces of
foreign matters per board,
slightly more irregular and fuzzy
than A.

27. YARN EVENNESS - ASTM GRADES
Grade C:
Some larger neps and more
smaller neps, fuzziness, foreign
matters more than B, more
rough appearance than B.

28. YARN EVENNESS - ASTM GRADES
Grade D:
Some slubs (more than 3 times
diameter of yarn). More neps,
larger size neps, fuzziness, thick
and thin places, foreign matters
than Grade C yarn. Overall
rougher appearance than C.

29. YARN EVENNESS - ASTM GRADES
Grade E:
Below grade D, more defects
and overall rougher appearance
than grade D yarn.

30. YARN EVENNESS
-INSTRUMENTAL GRADING
The grading the yarn evenness based on visual examination lost its
relevance with advent of instrumental grading, which is less prone
to judgmental errors and the results are repeatable.
It is now become normal and more acceptable trade practice to
declare the instrumental values, such as U% & CLASSIMAT values.

31. YARN EVENNESS
-INSTRUMENTAL VALUES
There are two methods to numerically express irregularity or
unevenness :
1.The Irregularity U%
2.The Coefficient of Variation ( CV% of Count).
Note:
I had already explained the influence of count CV% in earlier PPT

32. YARN EVENNESS
-INSTRUMENTAL VALUES
• Obviously the higher the CV% value, the more irregular the yarn
is.
• Mass variations in a yarn CV% were measured by using the Uster
evenness tester.

33. USTER %
Uster Technologies AG, Switzerland (USTER) created a numeric
value to describe the level of yarn unevenness, the so-called U%,
deriving from the German word ‘Unregelmässigkeit’, which means
irregularity.

34. USTER %
Uster Eveness in % (U%)
Uster% (U%) is a measure of unevenness of yarn.
Actually, this is a measure of variation in weight (in gms) of
approximately 1 cm. of yarn.
U%, the statistical value representing the percentage variation of a
yarn.
Lower the value the better the yarn, because less imperfections exist
in the yarn.

35. USTER® CLASSIMAT
Infrequent yarn faults are long thick places, long thin places, thick
ends, spinners doubles, etc. and are rare and hence a longer length
of yarn needs to be analysed.
The classimat system enables a quick and objective estimate of these
types of faults.

36. USTER® CLASSIMAT
The Uster Group is the leading high-technology instrument
manufacturer of products for quality measurement and certification
for the textile industry.
In 1968 USTER launched USTER CLASSIMAT, which classified
yarn defects into classes – the CLASSIMAT values

37. USTER® CLASSIMAT
The instrument “USTER CLASSIMAT” classifies /categorize the
yarn defects according to their size and length into 23 standard class
and designated as A0, A1, A2, A3, and so on ….
The latest instrument “USTER CLASSIMAT 5” detects and
quantifies unevenness for periodic faults, evenness, imperfections
and hairiness, in addition to critical thick and thin places.

38. USTER® CLASSIMAT
Now a days, the classification of yarn defects according to their size
and length into 23 standard classes is used extensively to certify yarn
quality ( and to compare the quality of different suppliers).
As a buyer, we need to determine & define the values to a specific
amount and range, in which the yarn tests must match.

39. USTER® CLASSIMAT
The 23 classes of yarn faults classified according to their length and
cross-sectional size is given here

40. USTER® CLASSIMAT

41. Here is the pictures of the faults corresponding to the previous chart

42. CLASSIMAT FAULT
Classimat Faults refers to no. of faults / 100km (CMT3)
Objectionable faults/100 km CMT3
(H2+I2)/100 km CMT3
(E+F+G)/100 km CMT3
(i.e. Imperfection / km) UT4
Similarly other imperfections like Thin place, Thick place and Neps
also quoted per Km (UT4)
Objectionable faults are: (A4B4C3D3C4D4)
(It is the sum of tested yarn values)

43. EXAMPLE OF
SPECIFICATION

44. EXAMPLE OF
SPECIFICATION

45. YARN EVENNESS
It is impossible to set out general rules or directives to determine
from yarn test results how the final fabric structure will appear -
because of the decisive influence of subsequent yarn processing
stages.
In addition, the woven fabric structure, the yarn count in weft and
warp, the number of picks and ends down and the knitted fabric
structure are all variables which affect fabric appearance.
In a similar way, the dyeing and finishing processes also have a
major impact on fabric appearance.

46. YARN EVENNESS
However, it is proven that testing of some of the most important
physical characteristics of a yarn can give a good indication of the
appearance of the finished fabric.
For example, a very uneven yarn can never result in a perfect fabric,
at least as far as appearance is concerned.

47. YARN EVENNESS
One can optimize the costs in the supply chain by defining the
specific needs with respect to quality parameters according to the
quoted values, compare yarns from different suppliers.
With this information in hand, we can optimize the portfolio of the
yarn producers and classify them into quality groups & pay the right
price for the right quality.

48. YARN EVENNESS
• The retailer will always be aware that consumers expect a certain
quality level, which is related to the brand image and reputation.
• Implementing Yarn Quality Profiles into the sourcing process is
very important in reducing quality costs and strengthening the
brand reputation.

49. UNDERSTANDING YARN QUALITY
– A WAY TO PROFITABILITY
Knowing the basics of raw material, yarn production process and
the other factors influencing quality will put the sourcing manager
at the same eye level as a spinner /supplier when negotiating quality
issues.
As a consequence this puts the sourcing manager in the position to
pay the right price for the corresponding quality level.
This kind of know-how supports a retailer enormously in his efforts
to establish a reliable supply chain which is based on mutual
understanding.

50. Note: This is an internal training document