2. INTRODUCTION TO COMBING
combing process removes predetermined level of
short fibers from the group of cotton fibers.
It is well known that the cotton fibers have
distribution of fiber lengths starting from long to very
short fibers.
For getting high quality of yarn, one extra process is
introduced which is called combing process.
The short fibers shorter than 12mm do not
contribute to the strength of the yarn, but increase
the hairiness of the yarn which effect the
appearance and other properties of the yarn.
3. Combing involves additional processing steps and
also certain amount of fibers are removed as waste.
Hence, combed yarn is more expensive than the
conventional carded yarn.
Combed yarn is softer than the carded yarn
because it is free from short fibers and all dirt and
impurities have been removed from the yarn.
The garments made with combed cotton yarns an
excellent choice of garments than the carded cotton
yarn since it is gentle against the skin.
The combed yarn are finer and smoother and more
uniform due to removal of short fibers as compare
to carded yarn
4. TYPES OF COMBER
The major types of combers include:-
Rectilinear comber (with stationary or oscillating
nippers),
Circular combers (English worsted process),
Rotary comber (production of Schappe spun yarns)
and
Hackling machines ( bast fibers).
5. SHORTCOMINGS OF THE COMBING
MACHINE
On the other hand, one has to keep in mind the
following shortcomings of having an additional
combing section in the yarn manufacturing system.
The combing section is an insertion of mostly three
machines into the normal spinning process
between card and draw frame.
It serves as an installation to improve yarn quality if
the carded yarn does not meet requirements. There
is no doubt that this process with three additional
machines increases the cost of the yarn.
A further increase in cost results from the design of
the comber itself, which is not very satisfactory due
to intermittent processing.
6. OPERATIONS IN COMBING PROCESS
Elimination of a precisely predetermined quantity of short fibers
Elimination of short fibers improves the stable
length of the combed cotton.
This also result in improves the fineness of the raw
material. The short fibers removed in combing
process is called noil. It is usually referred as a
percentage of the total amount of material feed to
the comber.
Noil percentage= weight of noil produced/total
weight of cotton fed*100
7. The amount of noil removed depend upon the
industry and the needs ranging from 8 to 25 %.
Elimination of remaining impurities
Although most of the larger and finer trash particles
and foreign material already removed in blow room
and carding operation, still some fine dust particles
are found to present in the carded sliver. which are
removed during combing operation.
8. Elimination of neps in the fiber material
Due to improper settings and conditions in carding
operation, some of the neps still remain in carded
sliver.
In the combing process, these neps get either
removed or straightened due to action of the
combing needles or inter fiber rubbing and sliding.
Formation of sliver having maximum possible fiber parallelization
It should be noted that in combing, fiber
parallelization increases. Please note that this is a
side effect which is not an advantage always.
9. . The high degree of parallelization might reduce
inter-fiber adhesion in the sliver to
such an extent that the fibers slide apart while
pulled out of the can. This may lead to sliver breaks
or false draft
Combing is the process which is used to upgrade
the raw material. It influences the following yarn
quality.
Yarn evenness
Strength
Cleanliness
Smoothness
Visual appearance
10. TYPES OF APPLICATION
Combing improves the quality of the yarn at the
cost of removing some amount of expensive raw
material with additional cost involving machinery,
energy and labour.
Hence the decision to use comber and remove
certain amount of noil for a particular application is
more of techno commercial one. Correspondingly,
basic distinctions are drawn between three major
groups of spinning mills using combing:
11. Fine count spinning mills :
These organizations use best quality, expensive
cotton of high strength, containing a low proportion
of short fibers and trash.
The final product is usually a fine to very fine yarn
of best quality. This puts highest demands on the
know-how and skills of operating personnel.
It also needs modern machines with best designs
and technology with proper maintenance of the
machines. In these cases, yarn production rate is
less of a concern, with high generation of noil to
ensure the best quality for yarns.
12. Medium count spinning mills :
In this case, cotton of medium properties with
varying quality parameters are spun into medium
and fine yarns of acceptable quality at reasonable
economic production costs.
This is becoming a more widely used process in
practice. Noil extracted is in the medium range and
the production rate is quite high.
This is a highly competitive process in the sense
that it has to yield high standard of quality at high
production rate with low cost.
This can be attained only with very stringent work
practices with well trained personnel.
13. Coarse to medium count spinning mills :
In this case, combing is an optional process to
upgrade the yarn cleanliness, smoothness and
strength.
This may use the same raw material used for
producing carded of the same count. Because of
additional combing process, in comparison with a
carded yarn, the combed yarn exhibits better yarn
properties.
Again in this case the production rate and cost of
production is not compromised with improved
quality with removal of noils in range of 8 to 18%.
In case of fine counts combing is an essential
process in order to get the minimum number of
fibers after removing certain amount of short fibers,
where as in this case it is only optional.
14. DISADVANTAGES OF COMBING
Short term unevenness.
sliver breaks at coiler.
The cost of additional expenditure on machine.
The cost of additional expenditure on material due
to loss of material as noil.
Floor space.
More energy is required.
Effect fineness of raw material.
The micronaire value is higher than the feed stock.
15. Combing sequence/ cycle
comber sequence is given below:
Lap feeding by feed roller
Lap nipping by the nipper
Combing by the cylinder
Nipper opening and forwarding
Detaching roller backward movement
Piecing
Combing by the top comb
Detaching roller forward movement
Starting a new cycle
Cleaning of cylinder comb
16. WORKING PRINCIPLE OF COMBER
The lap to be used is unrolled through the lap feed
rollers and lap sheet is introduced into the feeding
roller. The nippers and the feeding roller perform a
backward and forward motion. during the forward
motion, the upper part of the nippers opens and
during the backward motion closes again. As a
result of this movement, the feeding rollers are
driven and the feed lap sheet step by step over the
end of the bottom nippers. The nippers clamp the
lap sheet, which is combed from below by the
circular comb. Short fibers, which are no longer
clamped between the nippers, cling to the circular
comb.
17. The brush cleans the circular comb of the clinging
fibers, which are then pulled off by the suction.
The long fibers will be taken over by the forward
and backward motion of the detaching roller. The
web produced is formed into a sliver in the
condenser of the calendar rollers. All slivers from
the eight combing positions are then guided into the
draft system coiled into the can.
18.
19. TYPES OF FEED
In general there are two types of feed:
Forward feed: The material is fed whilst the nippers
is rocking towards the detaching rollers.
The major operational sequence is :
Combing Detachment Feed Combing
Backward feed: The material is fed during the
return of the nippers. The operational sequence is:
Combing feed Detachment combing
