- Basic operations in the blowroom:
mixing or blending
uniform feed to the carding machine
Recycling the waste
Blow room installations consists of a sequence of different machines to carry out the above said
operations.Moreover Since the tuft size of cotton becomes smaller and smaller, the required intensities of processing necessitates different machine configuration.
TECHNOLOGICAL POINTS IN BLOWROOM
Opening in blowroom means opening into small flocks.Technological operation of opening means the volume of the flock is increased while the number of fibres remains constant. i.e. the specific density of the material is reduced
The larger the dirt particle , the better they can be removed
Since almost every blowroom machine can shatter particles, as far as possible a lot of impurities should be eliminated at the start of the process.Opening should be followed immediately by cleaning, if possible in the same machine.
The higher the degree of opening, the higher the degree of cleaning. A very high cleaning effect is
almost always purchased at the cost of a high fibre loss. Higher roller speeds give a better cleaning effect but also more stress on the fibre.
Cleaning is made more difficult if the impurities of dirty cotton are distributed through a larger
quantity of material by mxing with clean cotton.
The cleaning efficiency is strongly dependent on the TRASH %. It is also affected by the size of the particle and stickyness of cotton. Therefore cleaning efficiency can be different for different cottons with the same trash %. There is a new concept called CLEANING RESISTANCE. Different cottons have different cleaning resistance.
If cotton is opened well in the opening process, cleaning becomes easier because opened cotton
has more surface area, therefore cleaning is more efficient
If automatic bale opener is used, the tuft size should be as small as possible and the machine stop time should be reduced to the minimum level possible
If Manual Bale openers are used, the tuft size fed to the feed lattice should be as small as possible
Due to machine harvesting , cotton contains more and more impurities, which furthermore are shattered by hard ginning. Therefore cleaning is always an important basic operation.
In cleaning, it is necessary to release the adhesion of the impurities to the fibres and to give hte particles an opportunity to separate from the stock. The former is achieved mostly by picking of flocks, the latter is achieved by leading the flocks over a grid.
Using Inclined spiked lattice for opening cotton in the intial stages is always a better way of
opening the cotton with minimum damages. Ofcourse the production is less with such type of machines.
But one should bear in mind that if material is recyled more in the lattice, neps may increase.
Traditional methods use more number of machines to open and clean natural fibres.
Mechanical action on fibres causes some deterioration on yarn quality, particularly in terms of neps .
Moreover it is true that the staple length of cotton can be significantly shortened .
Intensive opening in the initial machines like Bale breaker and blending machines means that shorter overall cleaning lines are adequate.
In a beating operation, the flocks are subjected to a sudden strong blow. The inertia of the impurities
accelerated to a high speed, is substantially greater than that of the opened flocks due to the low air resistance of the impurities. The latter are hurled against the grid and because of their small size, pass between the grid bars into the waste box, while the flocks continue around the periphery of the rotating beater.
By using a much shorter machine sequence, fibres with better elastic properties and improved
spinnability can be produced.
Air streams are often used in the latest machine sequence, to separate fibres from trash particles
by buoyancy differences rather than beating the material against a series of grid bars.
There are three types of feeding apparatus in the blowroom opening machines
two feed rollers( clamped)
feed roller and a feed table
a feed roller and pedals
Two feed roller arrangements gives the best forwarding motion, but unfortunately results in greatest
clamping distance between the cylinders and the beating element feed roller and pedal arrangement gives secure clamping throughout the width and a small clamping distance, which is very critical for an opening machine In a feed roller and table arrangement, the clamping distance can be made very small. This gives intensive opening, but clamping over the whole width is poor, because the roller presses only on the highest points of the web.
Thin places in the web can be dragged out of hte web as a clump by the beaters
Honeydew(sugar) or stickiness in cotton affect the process very badly. Beacause of that production
and quality is affected. Particles stick to metal surfaces, and it gets aggreavated with heat and pressure.
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