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Drafting Of Yarn


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This presentation is about yarn drafting and its process and its type...

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Drafting Of Yarn

  3. 3. Drafting is the reduction of mass per unit length of the sliver
  4. 4. This process include passing of sliver over a series of rollers. The rollers rotates at specified constant angular velocities, each faster then the older If all the draw is introduce in one step , in a single step of feeding and take-up rollers. This single draw can results in fiber breakage so it is compulsory to involve more then one drawn processes
  5. 5. Break Draft Main Draft Tension Draft Processes in drafting……
  6. 6. The draft at the back zone is called as back draft. The main object of the break draft is to enhance the fiber orientation instead of drafting itself. In the main draft execution take place but for an optimum draft the fiber orientation is very important.
  7. 7. Main draft is the drafting zone where the real drafting taken place. In here a high magnitude is taken place. For good fiber control many methods are used such as aprons , pressure bars. The total draft is the product of main and break draft.
  8. 8. The main object of the tension draft is to visualize better and adequate tension to the sliver.
  9. 9. 0 2 4 8 10 12 14 10 20 30 40 50 Time (S) Back Roller NIP 2nd Roller NIP 3rd Roller NIP Front Roller NIP
  10. 10. This also consist of three pairs of rollers similar to an ordinary drafting system It works on exceptionally slow speed It is known fact that slower the operation of drafting is performed the better result. The slowness of speed is that it may take two minutes for the back roller to make one single revolution. After the first drafting set the second one is gathering device which put certain amount of FALSE twist Between front roller and gathering device there is a controller which controls the speed and manage the draft
  11. 11. A roving frame is an intermediate b/w draw frame and ring frame. It insert small amount of twist into the roving. Wind the roving on the bobbin.
  12. 12. Time=1 sec (nip to nip) Roller Diameter=3cm Winding rate=120 rev/min Ratch =? (distance b/w two consequence roller) Circumference = 2 pie r = d pie => 3.14x 3 = 9.42 cm or 0.0942 m W roller (Angular velocity) = 120 rev/min = 120 pie x d /60 Surface speed or roller after drafting = 0.1884 m/s Surface speed or roller = After / Before = Draft after drafting =0.1884/x= 8 => so, x = 0.02355 m/s Vf=vi+at 0.1884=0.02355+a(1) => a= 0.16m/s2 S=vit+1/2at2 0.02355(1) + ½ (0.16) (1) => 0.1059 m Ratch is 0.1059 m
  13. 13. Fiber change their appearance More closely the molecules compact together , grater the strength Increase chemically stability due to compactness Lower moisture absorption
  14. 14. Bibliography: From the lecture of Sir Mazhar Jamil From book Modern Drafting In Cotton Spinning (Available in Library) From the slides of Dr.Yousuf lecturer of BANGLADESH GREEN UNIVESITY