YARN PRODUCTION

Principles and machinery for yarn production.Spinning preparatory processes A spinning mill employs a number of processes

to convert the fibres into yarn or thread. These processes contrive to clean the fibres, straighten and align them, and then bind them together as a strand by means of twist.

Spinning preparatory processes

Bale opening. Removal of contamination particles Dust removal Disentanglement into fiber flocks. Homogenization of raw material. Mixing

Bale opening

Bale opening consists of opening of bales and converting them to single fiber flocks . The quality of opening the fibers help in better contamination and impurities removal the more intensely opening is done the better will be the contamination and dust removal . By modern bale opening systems up to 80 bales are aligned up and flocks are separated with the help of series of beaters and transported by air streams through pipelines

Opening and cleaning

The main function of opening and cleaning machines are the further opening of fiber flocks and removal of contamination particles and dust from the cotton. Single roller or double roller opening and cleaning machines are in practice . Working principle is based on interaction of forces of acceleration and inertia .contaminating particles can be removed by the effect of centrifugal force and gravity through grid bars

The degree of cleaning (Rg) is the measure of the cleaning effect of machine

And is defined as

Rg = T ro - T r1.100% T roT ro = trash content before cleaningT r1= trash content after cleaning

Mixing

Mixing may take place during which batches of fibres from a number of similar types of bale are mixed together. Mixing serves to minimise the effect on the raw material of slight variations between the bales; this commonly occurs with natural fibres such as cotton.

Carding To separate the fibers from each other and to remove as much as possible of the remaining impurities. This is achieved by passing the fibers between closely spaced surfaces clothed with opposing sharp wire teeth in a process known as carding. The fibers are assembled into a loose strand (sliver or tow) at the conclusion of this stage.

Major objectives of carding Removal of dirt particles .Disentanglements of flocks into single fibers.Parallelizing of fibers .Mixing thoroughly Sliver formation and delivery

Action in Carding Machine :The following actions take place in a carding machine.

Combing action. Carding action. Stripping action. Doffing action. i. Combing action :

Combing action takes place feed roller & taken in. Here the pin directions of two surfaces are the same. Combing is the straightening & paralleling of fibers & the removal of short fibers & impurities by using a comb or combs which is assisted by roller & brushed.

ii. Carding action :Carding action takes place between flat & cylinder.

In carding action, Directions of wire in two surfaces are opposite. The moving directions of roller are also opposite. One roller is slower & other is faster. So carding action is known as “Point against point” action.

iii. Stripping action :

Stripping action takes place between,

a) Taker in and Cylinder &b) Doffer and stripper.

In stripping action, Wire direction will be the same. Roller moving direction will be the same. One roller will be faster than another. So stripping action is known as “Point back point” action.

iv. Doffing action :

This action takes place between cylinder & doffer. In this place fiber is transferred from cylinder to differ. Low speed doffer is called fiber form of high speed cylinder & makes a condensed web for formation of sliver.

Draw framesAfter carding process usually there are one or two drawing passages performing following tasksDoubling of multiple slivers and drafting for mixing and homogenizing .Removal of dust from slivers.Production of homogeneously mixed slivers for example 4 cotton and 2 polyester slivers . The drafting zone consists of 3 pairs of rollers continuous sliver is drafted Between these and homogenized sliver is produced and stored in storage cans.

Combing Combing is a process which is introduced into the spinning of finer and high

quality yarns from cotton. The carded materials (sliver) contain certain amount of short fibers, neps, fine kitty and leaf particles. Short fibers are a hindrance to spinning of finer counts where the number of fiber in the cross section of the yarn is less. The short fibers cause thick and uneven places in the yarn length and the yarn looks hairy. Apart from this, very short fibers do not contribute any thing to yarn strength. Short fibers below a certain pre-determined length can be easily separated out by using comber. 

Objectives of Comber: To remove the short fibers below a pre-selected length so that the spinner enable to produce finer or better quality of yarn that can not be possible in carding state.

Elimination of remaining impurities. Elimination of large proportion (not all) of the neps in the fiber. Formation of sliver having maximum possible evenness. To straighten the fibers.

Contribution of Comber to Yarn Quality: 

To improve the uniformity and strength Improve the spinning value of fiber. Reduce the neps in the yarn. Improve smoothness and luster of yarn. Produce much clear yarn. Improve the efficiency of the next process. Reduce the hairiness of the yarn. Improve better twist distribution in the yarn

Spinning systems

Ring spinning. Open end spinning . Ring spinning The most popular and extensively used spinning process. Almost 80% of the yarn manufactured is by ring spinning A method that provides better and even yarn.

Ring spinning is a two step process1 Flyer spinning frame (simplex)In the first step the drawn sliver is pre-drafted in the flyer spinning frame while it is also twisted slightly to prevent wrong drafts . This safety twist is not fair enough to give the yarn strength and optimum twist level required twist for manufacturing of fabrics the end product of this step is roving. So the next level of twist is associated with

Ring spinning machine

In the second step the flyer roving is pulled of the flyer bobbins and are fed to the ring spinning machine.

First the sliver is drafted to the final yarn twisting zone via double apron drafting unit . The essentially untwisted yarn exits the drafting field and is twisted by the each rotation of the traveller , the yarn is twisted once with each rotation of the cop drags the ring traveller with it . Hence yarn is twisted with each revolution of ring traveller .

Winding The produced yarn is in the form of small ring bobins or rotor in case

of OE spinning is further fed to the cone winding machine and yarn packages of desired length and weight are prepared with better yarn quality by removal of major spinning faults and waxing. The machine in practice for this purpose is auto cone winder.