class 2.ppt
- 1. Blow room is the first step of yarn production in the spinning mills. Basic operations in the blow-room: opening cleaning mixing or blending micro-dust removal uniform feed to the carding machine Blow room
- 2. Blow room installations consist of a sequence of different machines to carry out the above operations. Moreover, since the tuft size of cotton becomes smaller and smaller, The required degree of processing necessitates different machine configuration. Cont.…. Opening separates the compressed masses of staple into loose tufts and removes the heavier impurities. Opening
- 3. Cont.. The working hypothesis of opening is illustrated by calculation of the theoretical tuft weight curve starting from the bale, up to the cylinder of carding. How?
- 4. Cont.….
- 5. It is necessary to open more & more surfaces by opening devices Then remove the impurities from the newly created surfaces. Various types of grid bards are used for this purpose. In addition, air flow is also used to separate the trash from fibers. Suction devices are also used for separation of trash and dust. Various types of cleaning devices are: Cleaning by Grid Cleaning by Air Cleaning
- 6. Cleaning by Grid Cleaning by Air Cont.….
- 7. Some Technological points connected to opening and cleaning The larger the dirt particle, the better they can be removed. Higher the degree of opening results in higher the degree of cleaning. Higher roller speeds give a better cleaning effect, but also more stress on the fiber. The degree of cleaning is strongly dependent on the TRASH %. It is also affected by the size of the particle & stickiness of cotton. Therefore cleaning is always an important basic operation in modern blow-room.
- 8. opening device fiber alignment speed of the opening device degree of penetration thickness of the feed web density of the feed web size of the flocks in the feed area of the grid surface and grid settings ambient R.H.% and ambient temperature etc. General factors which affect the type of degree of opening , cleaning and fiber loss are:
- 9. Amount of trash in raw cotton – Trash in lap D.C = …………………………………………… * 100 Amount of trash in raw cotton Degree of cleaning(D.C) of the machine is the ratio of the trash removed by the machine to that of total trash fed to the machine, expressed as percentage. Degree of cleaning Mixing or Blending Blending: When different fibers of same/ different grades are kept together, then it is called blending. Mixing: If different grade of same fibers are kept together, then it is called mixing.
- 10. Almost all manufacturers of blow room machinery now offer dust-removing machines or equipment In addition to opening and cleaning machines. The dust is mainly removed, due to high fiber to metal friction or high fiber to fiber friction. Micro-dust removal Uniform feed to the carding machine Finally, the blow room must ensure that raw material is uniform deliver to the carding.
- 11. Magnetic extractors: This is used in order to remove ferrous metals mixed with material. Fire eliminators: This consist spark detector & eliminating device. Foreign matter detectors: It would intercept or prevent foreign matter in the opening and cleaning line, beginning of the spinning process in order to prevent fibrous contaminants. Associated equipment
- 12. Some general recommended process conditions in blow-room It is advisable to run the fans at optimum speeds and reduce the number of fans in the line All blow-room machines should work with maximum efficiency. Number of cleaning points are decided based on type of ginning. Machinery selection should be based on the type of cotton and production requirement. Grid bars should be inspected periodically, damaged grid bars should be replaced. Fiber rupture should be checked for each opening point
- 13. Carding In the yarn manufacturing process, carding comes after opening and cleaning of fibers at blow room. Carding process is considered, so important that carding is often called “the heart of spinning”. Individualization of fibers Elimination of impurities Elimination of dust Reduction in neps Fibre mixing/blending & Sliver forming Objectives of Carding
- 14. Individualization of fibers Carding is done primarily to individualize fibers. Blow-room machines open fibers in the form of flocks and A card will be a finishing operation of opening by individualizing them. Elimination of impurities The degree of cleaning of card is achieved up to 80-90 % in the modern carding machine. The over-all degree of cleaning achieved by the blow room and the carding together is as high as 95-99 %. But, card sliver still contains 0.05-0.3 % of trash and other foreign matters.
- 15. Reduction in Neps Number of neps in fibres increases in the blow-room. In carding, neps are drastically reduced. This can be attributed largely to the un-entanglement of neps rather than removal of neps during carding action. Elimination of Dust Dust removal requires significant fiber/metal and fiber/fiber friction; since, both are available in carding. Fiber Blending There is a repeated rotation of fibres in the card cylinder before it is removed by the doffer, the time spent is very small. So, there is not much longitudinal blending in carding. However, sufficient transverse blending takes place when web is condensed in to a sliver.
- 16. Sliver Formation Card forms a bulky sliver of overlapping and partially aligned fibres. The linear density of card sliver has hank from 3 ktex (new spinning processes) to 6 ktex. General, the hank lies b/n 4 and 5.5ktex in the spinning mills. Functional Zone of carding Generally there are four functional zone of carding Feeding zone - feed roller Cleaning zone- licker-in Carding zone- cylinder & flat Sliver formation zone-doffer
- 17. Draw frame Draw frames are used after carding in yarn manufacturing process. In the case of combed yarn manufacturing, draw frames are used before as well as after combing. Objectives Improvement in material evenness Parallelizing fibers Blending Dust removal Improving Evenness It is done in two stages; at breaker and at finisher draw frames. Therefore, two passages of drawing with eight ends (sometimes six) each time would produce a single sliver consisting.
- 18. Parallelization To achieve an optimal value for the strength of yarn, fibers must be arranged parallel to each other & along the axis of yarn. Draw frame fulfills this task by way of the drafting rollers. Mixing and Blending Drawing is the final stage of quality improvement in a spinning plant before yarn is spun. This is by providing the degree of compensation of raw material variation by blending. This result is exploited in particular, in the production of blended yarns consist of cotton/synthetic blends.
- 19. Dust removal Draw frame is a machine where a very high degree of fiber/fiber friction takes place in the drafting zone; so it lead separating dust. Many modern draw frames have appropriate suction removal systems; more than 80% of the incoming dust can be extracted. Elements of the draw frame Creel (sliver feed) The drafting system Delivery and coiling
- 20. Combing Elimination of a precisely pre-determined quantity of short fibers. Elimination of remaining impurities after blow-room and carding. Elimination of large proportion (not all) of the neps in the fiber To straighten the fibers Formation of a sliver having maximum possible evenness.
- 21. Roving frame Objective Attenuation: drafting the sliver into roving. The drafting arrangement in the roving frame attenuates the slivers with a draft between 5-20. Twisting: Twist of 30-65 per meter is usually provided in the roving frame. Winding: the twisted roving on a bobbin.
- 22. In cotton yarn production there are two main spinning systems which are used for the production: Ring spinning system, OE rotor spinning system Apart from these systems, there are new yarn spinning systems Friction spinning systems Air jet spinning systems Spinning The final stage of producing yarn.
- 23. Functions of Ring frame The ring spinning machine is designed to : To attenuate the roving until the required fineness is achieved. To imparting strength to the fiber strand by inserting twist. To wind up the resulting yarn in a suitable for storage, transportation and further processing. The main spinning arrangements are: 1- Drafting arrangement 2- Spindle 3- Ring and traveler
- 24. OE rotor spinning Tasks of rotor spinning machine Opening almost to individual fibers (fiber separation) Cleaning Combining (forming a coherent linear strand from individual fibers) Ordering (the fibers in the strand must have an orientation as far as possible in the longitudinal direction) Homogenizing to improve evenness Imparting strength by twisting and Winding to a cylindrical(weaving) or conical(knitting)cross-wound packages
- 25. Cont.….
- 26. Post-spinning processes Winding Bobbins from a ring frame contain too little yarn to be useful in modern fabric making equipment and, It is necessary to rewind the yarn onto larger packages. It is very important that the yarn which is to be sold or used in a subsequent process should be ‘put up’ into the correct sort of package–usually cones, cheeses, or occasionally, hanks. The transfer of yarn from the ring tube to the cheese or cone provides an opportunity to remove yarn faults.
- 27. Winding is carried out for the following purposes: To change the type of wind. To change the package density. To remove yarn faults. To create a package which is not influenced to damage. Plying For sewing threads, as well as certain speciality and industrial yarns, it is necessary to ply (i.e. to double or fold) the yarns to give them a smoother and less hairy character. Doubling improves the evenness; plying balances torque if carried out correctly and binds some of the hairs on the component yarns.
- 28. When, smooth cotton yarns are required, as in sewing thread, they are sometime singeing (or ‘gassed’) to remove the hairs. Such yarns are often two-ply; long-staple cottons are frequently used to give maximum strength and resistance to abrasion. Singeing Waxing It is applied in some machine specially winding in order to reduce the effect of friction on yarns, Ex Candle. Oil is applied through a device located on spindle head and comprising/consist a tank and a bush that, by capillary action, allows the oil to rise, reaching the yarn contact zone.