PROCESS PARAMETERS IN SIMPLLEX
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PROCESS PARAMETERS IN SIMPLEX
IMPORTANT PARAMETERS
1.Feed hank
2.Delivery hank
3.Roving tension
4.Break draft
5.Type of drafting
6.Bottom roller setting
7.Top roller setting
8.Spacers
9.TM
10.End breakages rate
DRAFTING SYSTEM
With 4 over 4 drafting system, the toal draft can be
upto 13, whereas in the case of 3 over 3 drafting system , the draft can not be
more than 11.
The
Roving thickness and Roving hairiness(yarn hairiness) will be less with 4 over
4 drafting system compared to 3 over 3 drafting system.
In
4 over 4 drafting system, since the fully drafted material is just condensed in
the front zone, if the stikiness in case of cotton or static in case of
synthetic is high, then the lapping tendency will be very high on second top
roller or second bottom roller. But in case of front roller, since the twist is
penetrating upto the nip, lapping on the front bottom or top roller will be
less.
As long as stickiness, honey dew in
cotton and static in synthetic fibres is less, 4 over 4 drafting system with
front zone as condensing zone, will give better results upto even 51 mm
fibre.Of course the humidity conditions should be good
3
over 3 drafting system is good for fibres longer than 51 mm. 30 or 32 mm bottom
roller diameters will be used with this system. Feed hank depends upon the
total draft in speed frame. The drafts mentioned in the above table can be
consdiered as a guide line. While processing 51 mm synthetic fibres, if the
delivery hank is coarser,and the delivery speed is
verh
high, the break draft and the back zone setting to be widened. Break draft and
break draft setting does not depend only on T.M and fibre properties, it
depends on the total production also. If the total production is very high,
with low break draft and closer setting, roving breaks due to undrafted strand
will increase.
Therefore,
for very high production rate , higher break draft and wider break draft
setting is required. This will result in very high "H" and
"I" classimat faults(long thin faults). Therefore the breakage rate
in
spinning
will increase.
Break draft setting and break draft
should be nominal. Abnormal break drafts and wider break draft settings
indicate that there is a major problem in the process
KINKS IN DRAW FRAME SLIVER
SLIVER
Some
times draw frame coiling is a very big problem with synthetic fibres . If kinks
are formed in the sliver, the kink has to be removed before entering the draft
zone.
Kinks in the
drawframe sliver depends upon
1. drawframe
delivery speed
2. delivery
can diameter
3. coiler
type
Higher
the delivery speed, more the chances for kinks to be formed in the sliver.
Lower the can diameter more the kinks. If a coiler which is meant for cotton is
used, the kinks in the sliver will increase in case of synthetic fibres.
While
processing synthetic fibres if kinks are more, it would be better if the creel
is stopped. Sometimes it would be recommeded to use a rod between top arm and
the first creel roll, so that the sliver takes a 90 degree bend before entering
the top arm. This will help to remove the the kinks in the sliver. Otherwise,
slubs in the roving will be more and the breakage rate in speed frame due to
undrafted strand in the drafting zone will be more.
ROVING TENSION
The
roving tension depends on the delivery rate and the difference between
peripheral speeds of flyer and the bobbin. If the delivery length and the
peripheral speed difference are same, then the tension is ideal.If
delivered
length is more than the difference in peripheral speed , then the roving
tension will be loose.
If
the delivered length by the front bottom roller is less than the difference in
pheripheral speeds of flyer and the bobbin, the roving tension will be tight.
Roving
tension can be of three types
1. Roving tension at the starting. It depends
upon the Bare bobbin diamter and the Cone drum belt position
- Roving tension during build-up. It depends upon the Ratchet wheel and lifter wheel. The difference between peripheral speeds of flyer and bobbin should be same and it should be slightly more than the length delivered by the front roller.
2. Roving
tension during up and down movement of the bobbin rail should be same. It
depends upon the half tooth movement of the ratchet. If it is not exactly half
tooth, then the tension will be different during up and down movement of the
bobbin rail
3.
With modern machines, cone drum is
removed. Bobbin speed, bobbin rail speed and flyer speed is determined by the
computer depending upon the tension settings.In some machines, it can be
programmed and the tension sensor helps to control a bit.In some makes, the
tension setting totally depends upon the sensing by sensors.
The
sensing accuracy depends upon the twist cap type, twist cape fixing, oil on top
of twist cap etc. If only one roving tension is different due to various other
reasons, then the entire machine tension will be altered. This is very
dangerous. Enough care should be taken to avoid this problem.
4. If
lifter wheel is changed, then tension during build up will also change, the
ratchet has to be selected accordingly. For a particular roving hank, ratchet
wheel depends on Lifter wheel also.
5. If
the tension is low but unfiorm through out the bobbin, then the bobbin will be
soft. Bobbin content will also be less. Chances of roving damages will be high.
6.
If the roving tension is more, then the stretch on
the roving will be more, thin places will be more.
But
it is better to increase the TPI little bit and increase the roving tension so
that the bobbin content is more, roving damages are less, and creel stretch in
the ring frame will also be less, because of higher TPI in the roving
OTHER FACTORS
It
is better to adopt group creeling in speed frame. Because every piecing of
sliver will result in a
thin
and thick place. Therefore it is preferable to change 30 upto 60 cans together
and remove the sliver piecing from the roving. Care should be taken so that no
sliver piecing and roving piecing enters the ringframe and results in yarn.
This
yarn always results in thin and thick places from .6 to 2 meters length. This
will not be cut by the yarn clearers if the difference in size is less.
Roving
Breaks in speed frame should not be more 1 to 2 per 100 spindle hours.If it is
more than that, the reasons should be analysed and corrective action should be
taken immediately.
Spacers should be
as small as possible, to improve yarn quality. If slubs and roving breaks due
to
undrafted
is more, it would be better to use a bigger spacer(distance clip) instead of
increasing the break draft and break draft zone setting to an abnormal level.
It is better to
use good quality apron and rubber cots , since the quantity produced by one
apron and
top roller is
very high compared to ringframe. If the apron breaks and top roller damages are
under control,
It
is always better to use the best apron and rubber cots available in the market.
One should not think about cost saving in this machine. Cost saving for apron
and cots can be considered for ringframes.
Buffing
should be done once in 3 months and the top roller shore hardness is around 80
to 85 degrees. After buffing, it is better to treat with acid or some special
liquids which are being supplied to reduce lapping
Bottom and top
clearers should rotate and should touch the top and bottom roller properly.
While
processing cotton combed material, flyer speed is very critical. When the
bobbin diamter is big, because of the centrifugal tension, surfact cuts will
increase. i.e. roving breaks may occur at presser
or
in strand that have just been wound on the top surface of the package. To avoid
this problem, it is better to use inverter drive system, to reduce the flyer
speed, when the bobbin diameter is big. Otherwise the overall speed should be
less for the entire doff, this will reduce the production of speedframe.
Sometimes, higher Twist will also reduce the surface cuts
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