Carding Technology Basics for Spinning Technicians
Carding Technology Basics
INTRODUCTION"Card is the heart of the spinning mill" and "Well carded is half spun" are two proverbs of the experts.
These proverbs inform the immense significance of carding in the spinning process. High production in carding to economize the process leads to reduction in yarn quality. Higher the production, the more sensitive becomes the carding operation and the greater danger of a negative influence on quality. The technological changes that has taken place in the process of carding is remarkable. Latest machines achieve the production rate of
60 - 100 kgs / hr, which used to be 5 - 10 kgs / hr, upto 1970.
THE PURPOSE OF CARDING:
1.
to open the flocks into individual fibres
2.
cleaning or elimination of impurities
3.
reduction of neps
4.
elimination of dust
5.
elimination of short fibres
6.
fibre blending
7.
fibre orientation or alignment
8.
sliver formation
TECHNOLOGICAL
POINTS IN CARDING
· There are two types of feeding to the cards
1.
feeding material in the form of scutcher lap
2.
flock feed system (flocks are transported
pneumatically)
· lapfeeding
1.
linear density of the lap is very good and it is
easier to maintain(uniformity)
2.
the whole installation is very flexible
3.
deviations in card output will be nil, as laps can
be rejected
4.
autolevellers are not required, hence investment
cost and maintenace cost is less
5.
transportation of lap needs more manual efforts(
more labour)
6.
lap run out is an additional source of fault, as it
should be replaced by a new lap
7.
more good fibre loss during lap change
8.
more load on the taker-in, as laps are heavily
compressed
·
flock feeding
- high
performance in carding due to high degree of openness of feed web
- labour
requirement is less due to no lap transportaion and lap change in cards
- flock
feeding is the only solution for high prouduction cards
- linear
density of the web fed to the card is not as good as lap
- installation
is not felxible
- autoleveller
is a must, hence investment cost and maintenance cost is more
·
Type of flock feed(chute feed)
- there are
two basic concepts of flock feed
- one
piece chute without an opening device
- two
piece chute with an opening system
- one piece
chute is simple, economical and requires little maintenance
- two piece
chute is complex, expensive, but delivers a uniform batt.
- One piece
chut is a closed system, i.e.excess flock returns to the distrbutor, if
too much material is present,
neps can be increased - one piece
chute is not flexible to run different mixings
- layout
restrictions are more with one piece chute
·
A feeding device is a must to feed the web to the Taker-in region and it
should perform the following tasks
- to clamp
the batt securely throughout its width
- to grip
the fibres tightly without slippage during the action of taker-in
- to present
the fibres in such a manner that opening can be carried out gently
·
The divertor nose(sharp or round) and the length of the nose(guide
surface) have a significant influence on quality and quantity of waste removed.
Shart nose divertor avoids fibre slippage but the opening action is not
gentle.If the length of the guide surface is too short, the fibres can escape
the action of the taker-in. They are scraped off by the mote knives and are
lost in the waste receiver.
·
Feed roller clothed with sawtooth is always better , because it gives
good batt retention. Thus the opening effect of the taker-in is more as it is
in combing
·
Rieter has devloped a "unidirectional feed system" where the
two feed devices(feed roller and feed plate are oppositely arranged when compared
with the conventional system. i.e. the cylinder is located below and the plate
is pressed against the cylinder by spring force. Owing to the direction of feed
roller, the fibre batt runs downwards without diversion directly into the teeth
of the taker-in(licker-in) which results in gentle fibre treatment. This helps
to reduce faults in the yarn.
·
The purpose of the taker-in is to pluck finely opened flocks out of the
feed batt, to lead them over the dirt eliminating parts like mote knives,
combing segment and waste plates, and then to deliver the fibres to themain
cylinder. In high production cards the rotational speed ranges from 700-1400
·
The treatment for opening and cleaning imparted by Taker-in is very
intensive, but unfortunately not verygentle.Remember that around 60% of the
fibres fed to the main cylinder is in the form of individual fibres.
·
The circumferential speed of Taker-in is around 13 to 15 m/sec and the
draft is more than 1000.It clearlyshows that fibre gets deteriorated at this
opening point. Only the degree of deterioration can be controlled by adjusting
the following
- the
thickness of the batt
- the degree
of openness of the rawmaterial
- the degree
of orientation of the fibres
- the
aggressiveness of the clothing
- the
distance between the devices
- the
rotational velocity of the taker-in
- the
material throughput
·
Latest TRUTZSCHLER cards work with three licker-ins compared to one
liker-in.The first one is constructed as needle roll. This results in very
gentle opening and an extremely long clothing life for this roll. The other
tworollers are with finer clothing and higher speeds, which results in feeding
more %of individual fibres and smallest tufts compared to single lickerin, to
the main cylinder. This allows the maing cylinder to go high in speeds and
reduce the load on cylinder and flat tops. There by higher productivity is
achieved with good quality. But the performance may vary for different
materials and different waste levels.
·
between the taker-in and main cylinder , the clothings are in the
doffing disposition. It exerts an influenceon the sliver quality and also on
the improvement in fibres longitudinal orientation that occurs here.
The effect depends on the draft between main cylinder and taker-in.The draft between main cylinder and taker-in should be slightly more than 2.0.
The effect depends on the draft between main cylinder and taker-in.The draft between main cylinder and taker-in should be slightly more than 2.0.
·
The opening effect is directly proportional to the number of wire points
per fibre. At the Taker-in
perhaps 0.3 points/ fibre and at the main cylinder 10-15 points /fibre.If a given quality of yarn is required, a corresponding degree of opening at the card is needed. To increase production in carding, the number of pointsper unit time must also be increased. this can be achieved by
perhaps 0.3 points/ fibre and at the main cylinder 10-15 points /fibre.If a given quality of yarn is required, a corresponding degree of opening at the card is needed. To increase production in carding, the number of pointsper unit time must also be increased. this can be achieved by
- more
points per unit area(finer clothing)
- higher
roller and cylinder speeds
- more
carding surface or carding position
problems. Hence the best way is to add carding surface (stationary flats). Carding plates can be applied at
- under the
liker-in
- between
the licker-in and flats
- between
flats and doffer
·
Taker-in does not deliver 100% individual fibres to main cylinder. It
delivers around 70% as small flocksto main cylinder. If carding segments are
not used, the load on cylinder and flats will be very high and cardingaction
also suffers. If carding segemets are used, they ensure further opening,
thinning out and primarily, spreading out and improved distribution of the
flocks over the total surface area.carding segments bring the following
advantages
- improved
dirt and dust elimination
- improved
disentanglement of neps
- possibility
of speed increase (production increase)
- preservation
of the clothing
- possibility
of using finer clothings on the flats and cylinder
- better
yarn quality
- less
damage to the clothing
- cleaner
clothing
·
In an indepth analysis, all operating elements of the card were
therefore checked in regard to their
influence on carding intensity. It showed that the "CYLINDER-FLATS" area is by far the most effective region of the card for.
influence on carding intensity. It showed that the "CYLINDER-FLATS" area is by far the most effective region of the card for.
- opening
of flocks to individual fibres
- elimination
of remaining impurities(trash particles)
- elimination
of short fibres( neps also removed with short fibres)
- untangling
the neps
- dust
removal
- high
degree of longitudinal orientation of the fibres
·
The main work of the card, separation to individual fibres is done
between the main cylinder and the flats Only by means of this fibre separation,
it is possible to eliminate the fine dirt particles and dust. When a flat
enters the working zone, it gets filled up very quickly. Once it gets filled,
after few seconds, thereafter , hardly any further take-up of fibres occurs,
only carding.Accordingly, if a fibre bundle does not find place at the first
few flats, then it can be opened only with difficulty.It will be rolled between
the working surfaces and usually leads to nep formation
·
In princile, the flats can be moved forwards or backwards, i.e. in the
same direction as or in opposition to the cylinder.In reverse movement, the
flats come into operative relationship with the cylinder clothing on the doffer
side. At this stage, the flats are in a clean condition. They then move towards
the taker-in and fill up during this movement.Part of their receiving capacity
is thus lost, but sufficientremains for elimination of dirt, since this step
takes place where the material first enters the flats.
At this position, above the taker-in, the cylinder carries the material to be cleaned into the flats. The
latter take up the dirt but do not transport it through the whole machine as in the forward movement system. Instead , the dirt is immediately removed from the machine. Rieter studies show clearly that the greater part of the dirt is hurled into the first flats directly above the taker-in.
At this position, above the taker-in, the cylinder carries the material to be cleaned into the flats. The
latter take up the dirt but do not transport it through the whole machine as in the forward movement system. Instead , the dirt is immediately removed from the machine. Rieter studies show clearly that the greater part of the dirt is hurled into the first flats directly above the taker-in.
·
Kaufmann indicates that 75% of all neps can be disentagled, and of these
about 60% are in fact
disentagled. Of the remaining 40% disentaglable nep
disentagled. Of the remaining 40% disentaglable nep
- 30-33%
pas on with the sliver
- 5-6% are
removed with the flat strips
- 2-4%are
eliminated with the waste
The intensity of nep separation depends on
- the sharpness
of the clothing
- the space
setting between the main cylinder and the flats
- tooth
density of the clothing
- speed of
the main cylinder
- speed of
the flat tops
- direction
of flats with reference to cylinder
- the
profile of the cylinder wire
·
The arrangement of the clothing between the cylinder and the doffer is
not meant for stripping action, It is for CARDING ACTION.This is the only way
to obtain a condensing action and finally to form a web. It has both advantages
and disadvantages.The advantage is that additional carding action is obtained
here and it differssomewhat from processsing at the flats.A disadvantage is
that leading hooks and trailing hooks are formed in the fibres , beause the
fibres remain caught at one end of the main cylinder(leading hook) and some
times on the doffer clothing(trailing hook).
·
There are two rules of carding
- The
fibre must enter the carding machine, be efficiently carded and taken from
it in as little time as possible.
- The
fibre must be under control from entry to exit
·
Carding effect is taking place between cylinder and doffer because,
either the main cylinder clothing rakes through the fibres caught in the doffer
clothing, or the doffer clothing rakes thro the fibres on the main cylinder.
Neps can still be disentangled here, or non-separated fibre bundles can be
opened a bit in this area and can be separated during the next passage through
the flats
·
A disadvantage of web-formation at the card is the formation of hooks.
According to an investigation by morton and Yen in Manchester , it can be assumed that
- 50% of
the fibres have trailing hooks
- 15% have
leading hooks
- 15% have
both ends hooked
- 20%
without hooks
·
Leading hooks must be presented to the comber and trailing hooks to the
ring spinning frame.
There must be even number of passages between card and comber and odd number between the card and ringframe.
There must be even number of passages between card and comber and odd number between the card and ringframe.
Key words:
Spun yarn technology for textile students, Carding technology basics, Carding theory in spinning mills, Carding machine basic knowledge for spinning technicians.
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