2. • Objects of jute drawing frames:
• Straightening of fibres in the silver
• Parallelization of fibres in the silver
• To reduce the weight per unit length of sliver
• To reduce the thick & thin places in the sliver
3. ⮚Main functions of drawing frame:
▪ Drawing. The regular & uniform elongation of the
sliver is called drawing. Drawing takes place
between retaining roller & drawing roller.
▪ Doubling: To produce one sliver from two or more
sliver is called doubling.
▪ Drafting: Ratio of the surface speed of deliver
(drawing) roller & feed (retaining roller is called-
drafting.
4. • Desirable features is any type of drawing frame:
• An ideal method of pinning the slivers that is the gill pins must
enter and leave the sliver as nearly perpendicular as possible.
• Small lead of gills or fallers to avoid undue tension on the sliver
between the faller bars and retaining rollers.
• Shortest possible nip to give maximum possible control of
fibres in drafting
• Freedom of movement of fibres in the drafting zone.
• Reliability of the working parts.
• High speed of fallers permitting maximum production.
• Less noise of fallers when working.
5. A. Reach: The distance between the center of the front back roller (retaining) to the bite of
the front (drawing) & front pressing roller is known as reach of the drawing frame. The
reach should be slightly longer than the longest fibre in the sliver.
B. Nip: the distance between the foremost gills where the pins leave the sliver and the bite
of the front pressing roller is called “Nip”. The distance should be as short as possible.
C. Pitch of faller: the distance between the one rows of pins of one faller bar to pins of next
faller bar is called pitch of faller.
D. Lead%: The difference in the surface speed of fallers over surface speed of retaining
roller to give sufficient tension to the sliver is known as lead percentage. This lead should
not be more or less.
S.S. of faller - S.S. of retaining roller) X 100%
Faller bar lead % =
S.S. of retaining roller.
7. • Figure shows the general outline of a jute drawing frame. The slivers
feed through two retaining rollers and a self-weighted jockey roller and
then pass through the gill pins.
• The gill pins are carried on a series of faller bars which move forward
and follows a rotational path. As the slivers leave the nip of the back
retaining roll, a faller bar with its sharp pins strike upwards into it and
the slivers are carried forward to the front of the machine in a
controlled manner like a continuous layer over the faller bars. When the
faller bars are close to the drawing rollers they drop out of the sliver
and travel back underneath the sliver in preparation for another strike
upwards.
• The relative surface speed of the drawing roller and retaining roller
determines the draft. The linear speed of the gill pinned fallers is 10 to
15% higher than that of retaining rollers to maintain the required
tension and is known as lead%.
8. • The doubling plate is a cast iron plate having slots with rounded edges
at an angle of 45° to the line of the frame through which the sliver
can pass so as to change their direction. In this doublings one sliver
comes straight and the other slivers are turned through 45°.
• After doubling, slivers are crimped to increase the cohesiveness
between fibres and then crimped fibres are gathered at sliver can.
9. Crimping Box in Draw Frame:
• In 2nd and 3rd drawing frame of jute we see that there is a crimping
box after the sliver emerges out the delivery rollers.
• Necessity Of Crimping Box:
• In case of cotton we see that cotton has some natural convolutions.
So it needs not to be crimped. But in case of jute we see that jute has
no natural crimp. So as the draw sliver of jute comes out from flaw
frame its count is reduced and it becomes mare and more fragile
when it emerges out from the finisher draw frame. So to overcome
this problem, the sliver is crimped to give a certain amount of
cohesion and strength to the strand. This crimping is imparted to the
draw sliver by crimping box.
10.
11. • Crimping Process: In this figure below a crimping box is shown which
is attached to the delivery of a finisher drawing frame.
• The sliver leaves the nip of the drafting rollers and passes down the
sliver plate into the nip of a pair of fluted delivery roller. The upper
roller is spring loaded and positively driven through a wide pitch gear
from the lower one.
• The sliver is driven into a box where it meets a metal finger or lid
which is hanging down into the box. The finger hinders the motion of
sliver and the box is filled quickly. When more sliver enters the back
of the lid of the box. The sliver is forced up by the mass of sliver inside
the box. So the sliver at the front of the box comes out.
12. • This is a continuous process. During its processing in the box the
fibers of the sliver take on a permanent crimp or wave.
• The time of staying the sliver inside the box can be regulated by
means of a small weight which can be added to the finger. A heavy
weight on the finger required greater mass of sliver to lift the finger
up and hence develops greater amount of crimp in the fibers.
13. Difference among 1st , 2nd and 3rd draw frames
Sl.
No.
Topics 1st D/F 2nd D/F 3rd D/F
1. No of head 2 3 5
2. No of sliver feed/head 4 6 8
3. No of delivery /head 2 2 4
4. Doubling ratio 2:1 3:1 2:1
5. Deliver sliver weight 3-5 5-7 7-9
6. Crimping arrangement Absent Present Present
14. Sl. No. Topics 1st draw frame 2nd draw frame 3rd draw frame
7. 7. Concentrated can
packing arrangement.
Absent Present Present
8. 8. Faller bar pitch. ½” ½” 3/8”
9. 9. Production/ hour/m/c 600-650 lbs 600-650 lbs 400-450 lbs
10. 10. Auto stop motion. At both feed and
delivery end
At feed end. At delivery end.
11. 11. Change pinions in
m/c.
Surface change,
draft change,
variable v-pulley.
Surface speed
change, draft
change.
Surface speed
change draft
change.
