Terry fabrics are used in various fields
because of their water absorption properties. Looms for the production of
terry fabrics operate with two warp systems. The highly tensioned warp for
the base fabric is processed in conjunction with loosely running warp pile,
which is fed to the base warp at a certain ratio. As an additional warp yarn
is inserted into the base fabric, a third dimension, the pile height is
formed. The fabric volume increased in this manner leads on the one hand to
a bulky and soft handle and, on the other hand, to an increased surface area
of the fabric. Absorbancy and heat retaining capacity are thus improved and
are, among other factors, decisive for the further processing into bath
robes, leisure, sports & baby wear.
Weaving is a critical process in terry
manufacturing as it requires a well prepared material, trained personnel,
and a complex weaving mechanism. A well structured quality control system
which gives due importance to the above requirements can only ensure the
production of a fabric of expected quality consistently. In this paper,
various quality control measures that are required in different stages of
terry fabric production are discussed in detail.
Strip of three pix.
Yarns for terry weaving
Yarns for weaving may be:
(i) Grey yarns
(ii) Processed yarns (bleached yarns, mercerised yarn, dyed yarn)
Terry fabrics must be produced at a certain weight per square metre, using
mostly 100% cotton yarns as Pile, ground and weft. Yarn counts that are
normally used for pile warp yarns are: Ne 10, Ne12, Ne16, Ne 2/20, Ne 2/24,
Ne10 + Ne 60 PVA, etc.
Yarns made out of PVA fibres can be doubled with cotton yarns for the
production of super soft Terry fabrics. PVA fibres will be dissolved out at
processing stage, leaving a fluffy soft terry structure.
Count ranges used for ground warp yarns are:
Ne10, Ne11, Ne 2/20, Ne2/24 etc.
Count range for weft yarns are:
Ne 2/20, Ne1/14, Ne1/12, Ne 2/24, Ne 2/16, etc.
It is the pile yarns that contribute to more than 60% of total fabric
weight. Mostly ring spun yarns are used as pile yarns. OE yarns also can be
used as pile yarns and it depends upon customer requirements. Typical yarn
quality requirements for pile warp yarn are given in Table 1.
Table - 1
Count Cv %
Strength Cv %
Rkm Cv %
(Data given above shows only the minimum
quality requirement. However, a mill can set its own quality standards as
per its achievable quality level.)
Beam warping or direct warping is the preferred route for
producing piece dyed terry fabrics while sectional warping is opted for yarn
dyed fabric production.
(a) Control on incoming material (cones)
To ensure the production of a quality beam at sizing it is very
essential to have a strict control on the incoming material. Apart from
testing the cones for quality parameters (Table 1), the following measures
have to be adopted.
A regular check on the lot number of
cones in the carton boxes and the presence/absence of identification mark on
cones shall be established. Mixing up of yarns of different counts and cones
of different lot numbers will lead to shade variation after dyeing.
Check the weight of cones on sample basis and find out the weight variation
of cones. A report on Cone weight variation shall be maintained.
Cone density may also be checked periodically
Proper material handling procedures has to be set and should be followed
(b) Warping stage
Quality control measures:
Speed of warping should be almost constant throughout the winding of the
beam. Of course, running the machine at slower speeds during the initial and
final phase to control end breaks is allowable. Sort details (count, type of
yarn, no. of ends/creel) and labeling on beam is to be checked for
identification and traceability.
Proper working of stop motions has to be checked to avoid missing ends in
the beam. An end break study has to be done for each lot of material and the
reason for end breaks has to be recorded and investigated.
Packages causing repeated machine stops should be immediately replaced by
the worker. Single end tension can be measured at different positions in the
creel, ie. near the headstock, at the farthest creel position, in the left
side of the m/c, and in the right side of the m/c.
Beam density can be checked at the left, centre and right side of the beam.
Percentage of bottoms generated (Remnant %) has to be calculated for every
creeling. For efficient warping operation, the remnant should be less than
Temperature & RH conditions are to be maintained inside the department.
Though the present day machines have mechanisms that automatically regulate
the yarn tension, pressure on drum for beam density as per requirements, a
random check on these parameters is must to produce a quality warpers beam.
The importance of sizing is well known and a proper sizing only
can ensure loom efficiency and production of quality fabric. The percentage
of size add-on depends on quality of yarn, ends/inch in the fabric, loom
speed, etc. But the real performance of sized yarn is assessed by the
incidence of end breaks in loom. End break study in the loom shed will give
a clear picture on the quality of sizing. Sizing of pile yarns for terry
weaving usually requires a low size add-on of 1 to 5% compared to 8 -14% of
warp yarn for ordinary weaving. Ground yarns also require low size add-on
especially if they are doubled yarns.
Still, the operation of sizing is very
critical as poor sizing causes variety of production and quality problems in
loom shed. If yarns are not properly covered by the size, on exposure to
abrasive actions in loom, the fibres from the yarn body will be pulled out,
leading to the problem of “linting” in terry fabrics. Linting is a major
Nowadays, pre-blended sizes are used as
sizing material which may contain, modified starch, PVA, wetting agents,
antifoaming agent, etc. Application of more size or other secondary
ingredients to yarn is based on the performance of yarns in weaving.
Quality control measures at sizing
Check the quality of size materials
Check the viscosity (using viscosity cup) and solid content (using
refractometre) of size paste in both the cooking stage and also in sow box.
Sizing quality study has to be done for full beam, at least once in a shift
for every machine and the incidence of lappers and migratory ends has to be
Check the creel tension, braking pressure of creel beam, feed tension of
yarn before sow box, sow box temperature, nip pressure (squeezing), drying
zone temperature, beam pressing pressure, winding tension and % stretch.
These parameters are automatically regulated in automatic sizing machines as
A random check on % moisture in the sized beam is essential even for
automatic sizing machines that have automatic control.
Every sized beam has to be weighed and % size add-on is to be calculated
& recorded. Tensile testing of sized yarn may also be carried out to
ascertain the improvement in strength.
As mentioned earlier, the production of terry fabrics require the
use of two beams, one beam for the ground structure and the other for pile
structure. Generally warp density varies between 10-15 ends/cm in ground and
as well as pile. In denser construction it ranges between 15-18 ends/cm. The
pile ratio of 1:4 to 1:8 is used depending on the end use of terry fabrics.
Pile ratio is the length of pile yarn to the length of terry fabric.
Quality control measures at loom shed
A typical loom card data for production of a terry towel fabric is shown
in Table 2 and the formation of a three pick terry structure is shown in
Figure1. Formation of a three pick
Grey size (cm)
Finished size (cm)
Ground yarn count
Pile yarn count
Picks per cm
Pile height (cm)
Towel weight (g)
145 x 85
137 x 76
a) First Piece Inspection
For every new sort, on production of few metres of fabric, the fabric
has to be inspected for the following against the customer requirements.
Weight per square metre (GSM)
Dimensions (length, width, size of design portion, etc)
Loops/sq inch, and
(b) Control on weight per square
metre of terry fabrics
Terry fabrics are sold on weight basis and hence a control on fabric
weight is of paramount importance. Weight/square metre (GSM) of terry
fabrics are generally in the range of 360-670 grams. Companies mainly use
standard warp and weft yarn counts as well as warp density. For required
terry weight per square metre, the weft density and pile length are the
parameters to be adjusted. The length of pile in relation to the length of
terry fabric is measured in terms of pile ratio.
The pile ratio, pile height and weft density (picks/cm) are related by the
Pile height (in cm) = (Pile ratio/Picks
per cm) x 0.5 x Type of terry
(c) Online and offline inspections
On-line inspection in looms should ensure that defects are identified
and rectified in the loom stage itself. In fact, on loom inspection gives a
clear idea not only on the defects, but also on the quality of warp beams,
quality of weft yarn, condition of m/c, operator skill, etc.
Off-line inspection, which is grey inspection of fabrics, is normally
carried out on sample basis and the defects are to be properly identified
and recorded. 100% Grey inspection is necessary only if the online
inspections are not effective in controlling the defects. The doff weight
and dimensions of relaxed fabrics are checked in grey inspection stage.
The list of mendable and non-mendable
terry weaving defects is given in Table 3.
Defects can also be classified as Major
and Minor depending on its intensity.
For example, temple mark that is visible as thin lines in grey inspection
stage may not show up after processing stage. This can be considered as a
minor defect. However, if the lines are very prominent and had disturbed the
loop structure, it is certain that they will show up well after processing.
Then it should be considered as a major defect. In this regard, training of
quality personnel about various types of defects in fabrics and its
implication on the final quality of the product is a must.
Identification of quality elements, developing it into system,
effective system implementation, and continual improvement of the system are
the ingredients of a successful Quality Management System. Since the market
of terry fabrics has undergone a phenomenal change in recent years, a
comprehensive and stringent quality control system is very essential to
deliver a product that consistently meets the ever-increasing customer
Note: For detailed version of this
article please refer the print version of The Indian Textile Journal July
K S R College of Technology,
Tiruchengode, Tamil Nadu.