Simplex
Simplex | Objects and operations of
simplex
Simplex: In yarn manufacturing system,
simplex frame is situated after the comber. The sliver which is produced from
the comber that is thicker and it is not suitable to feed into the ring frame
directly to produce yarn. For this reason, drawn sliver is treated before
entering into the ring frame. The commonly used simplex machine for cotton is
flyer frame or speed frame. There are three basic steps in the operation of the
roving frame – drafting, twisting and winding. These three basic steps are
exactly the same as the basic steps required in spinning.
The
machine where the sliver is subjected to one or more attenuating process and
the attenuated sliver receives a small amount of twist and is then wound on
bobbins suitable for creeling at next process.
In
this process drawn sliver is input and fine roving is output. The roving is
feed into ring frame for yarn production. It is noted that, simplex is
essential for the production of cotton yarn in case of ring spinning by ring
spinning system.
Other names of simplex machine:
a) Fly frame.
b)
Roving frame.
c) Speed frame.
Objects or functions of speed frame:
- Attenuation of drawn sliver to form roving of required count by drafting.
- Insert small amount of twist to give required strength to roving.
- Wind the twisted roving onto the bobbin.
- Build the roving in full length of bobbin in such a form which will facilate handling, transfer and feeding to ring frame.
The main operations or functions of
simplex machine:
Various
types of objectives are achieved by simplex machine. Followings are the main
functions of simplex machine –
- Creeling: Creeling is the first objective of simplex frame arrangement. By the creeling, small amount of draft is applied to the drawn sliver.
- Drafting: Attenuation of drawn sliver to produce required amount of roving by drafting. Thick drawn sliver is converted into thin roving by drafting system.
- Twisting: Small amount of twist is inserted in the drafted stand of fibres by the twisting. The amount of twist is very low.
- Building: Build the roving on to bobbin such a form which will facilate unwinding, handling and transfer to the next process.
- Winding: Produced or twisted roving is wound on the bobbin by the winding process. This bobbin is feed to the ring frame and this bobbin accelerates the next process. So, it is important.
- Doffing: It is the optional function of speed frame. Doffing could be done manually or automatically.
So,
simplex frame plays an important role in the spinning process. Various types of
yarn faults could be appear for the wrong drafting or twisting. For this
reason, the operator should be careful during the process.
Suppose,
a certain hank is made on a machine and it is desired to change to a higher
count. The same sliver or roving is used in the creel. The necessary changes
are as follows –
Draft: This must be altered in order to
make the delivery roving finer. The draft change pinion (D.C.P) will therefore
be made smaller in order to drive the back roller more slowly.
Lifter change wheel: A smaller lifter change wheel slows
down the lifter shaft without altering the bobbin speed and thus decreases the
spacing of the coils.
Ratchet wheel or Spur wheel change
building motion: The
finer roving also requires that the ratchet wheel should be entangled (i.e.
greater no. of teeth) in order that a lessened movement be given to the rack at
each up & down lift. There will be more layer/inch of diameter for the
finer than for the coarser roving, therefore each action of the lift must give
a shorter traverse to the rack which moves the cone drum strap in short steps.
With
the spur-wheel change build motion, a finer hank will require either a larger
wheel in the top position or a smaller wheel in the bottom position.
Bottom cone-drum change or winding
wheel: A smaller
wheel (if it is driver one) will be required to correct winding on the bobbin
as the front roller delivery will be less for the finer hank.
Twist change pinion: A finer roving requires more
twist/inch into it than a coarser one. Twist wheel is changed for this purpose
and by making it smaller, the speeds of the front roller is reduced but since
the speed of the spindles is not altered, more twist will be put into the
roving.
From
this change, it will be noticed that the speed of the cone drum is also
changed, which is a necessary consequence of changing of the speed of the front
roller to slow, the bobbins must have the same reduction in the speed in order
to wind on the smaller amount of roving that is delivered to them.
The
differences between apron and roller drafting system are as follows –
Apron
Drafting
|
Roller
Drafting
|
Poor
or no control of short fibres movement
|
|
Better
yarn quality with a given draft
|
Poor
yarn quality for the same draft
|
Regularity
of material is better
|
Regularity
of material is poor
|
Less
influenced by changes in staple length and length distribution.
|
More
influenced by changes in staple length and length distribution.
|
Higher
range of draft
|
Lower
range of draft
|
Smoother,
durable and reliable running.
|
Less
smoother, durable and reliable running.
|
Lower
end breakage rate and roller lapping.
|
Higher
end breakage rate and roller lapping.
|
Automatic
clearer increases yarn cleanliness.
|
No
such clearer and thus poor yarn cleanliness.
|
Higher
production.
|
Lower
production.
|
Higher
spindle speed.
|
What
are the different drafting systems used in speed frame?
The
following drafting systems are used in speed frame –
-
4 - over - 4, two zone drafting
system.
-
Two-zone apron drafting, (4 - over
4), aprons are adjusted on 2nd top and bottom roller, better fibre control and higher drafting can be
attained with this drafting system at the speed frame.
-
2 – over – 3 drafting system, this
gives effective grip on the fibre, usually suitable for synthetic fibre, less
slippage of fibres in this drafting system.
-
4 – over – 4 graduated roller
drafting system.
-
3 – over – 3 drafting system.
-
Casablancas – 2 – zone system.
-
Casablancas U – 3 system.
-
Platt special 3 – line drafting
system.
-
S.K.F PK 400 system.
-
Toyodas 3 – over – 3 two zone
system.
-
Toyodas 4 – over – 4 three zone
system.
-
Toyodas FL 2 (D type one zone
system).
Describe
a modern drafting system
Description of Casablancas two-zone
drafting system
–
The
Casablancas two-zone drafting system is widely used for cotton on speed frame. The back zone draft takes the place between two pairs of
roller, after which follows a zone with practically no draft, in which a
special condenser is placed to fold the fibre strand upon itself for
consolidation prior to finally drafting it once again in the front zone.
The
front zone is composed of the casablancas double apron unit followed by a
congenital pair of front rollers. The draft in this zone about three times that
in the back zone. Between the Casablancas bands and the front pair of rollers
there is a second condenser, the “collector” which incorporates the stray
fibres into the bulk to prevent the creation of excessive amount of fly. The
Casablancas weighing arrangement consists of a saddle assembly, which receives
weight through a single hook and lever.
Ratching
It
is defined as undesired stretching of the roving to make it finer and it
produces a high count variation.
Causes: Larger lifter wheel, or winding
wheel, or ratchet wheel, or starting with half layer.
Remedies: This defect can be cured by using a
correct smaller lifter wheel, winding wheel and ratchet wheel or rack wheel. At
the start of a new doff the bobbin rail should be taken up or down to start
with a full layer instead of a half layer which will produce uneven tension
during winding the next layer on the bare bobbin.
Unequal tappers
This
defect will occur if the pocker rack is not perfectly level when the pressure
eye is at the middle of the lift. To equalize the tappers, mark the exact
centre of the barrel portion of a bobbin and place the bobbin and a flyer in
their working position. Mark the top rail until this is in the centre of the
pressure eye and then level the two bars and the rack pocker by spiraled level.
Reset the adjusting screws in the pocker bracket so that they operate the
motion catches correctly at the top and bottom of the lift.
Stretched roving
Stretching
is due to the difference in surface speed between the bobbin and the pressure
eye being greater than the surface speed of the front roller. It occurs
throughout the build, reduces the bobbin speed by using a smaller bottom cone
drum change wheel.
If stretching gets progressively worse in
the bobbin build up, building motion ratchet wheel to be with fewer number of
teeth or the spur wheel change building motion to be adjusted to give the same
effect. This will make the cone drum belt along the cone drums at a higher rate
and thus gives a greater reduction in bobbin speed as the package diameter
increases.
Too small a lifter change wheel can cause
this defect through adjusting coils tending to ride on one another. This wheel
is to be made larger.
An accumulation of waste in the legs of
the flyers will lead to stretching the individual spindles. In this case the
roving will be slack between the front rollers and the affected flyers.
Sloughing
Causes:
-
Sloughing at the bobbin ends may be
due to reversing bevels which are badly worn or too shallowly meshed.
-
Motion catches with worn ends.
-
Insufficient taper on the bobbins.
-
Balance weights not fitted correctly
or touching the floor.
-
Hesitation at the change over either
the building motion or the reversing mechanism resulting from dirt, tightness
or incorrect setting.
Remedies:
-
The worn bevels should be replaced.
-
Correct shape of the motion catches.
-
Correct tapper of bobbins.
-
Proper setting of the related parts.
Incorrect tapper
This
defect can be rectified by changing the tapper wheel. Reduce number of teeth in
the tapper wheel reduces the tapper and vice-versa.
Ridgy bobbins
Faulty
movement of the top rail results in ridgy bobbins at the bobbin ends.
Causes:
-
Tight or badly worn lifter shaft
bearings.
-
Dirt on the top rail sides.
-
Worn revering bevels.
-
Slack lifter shaft pinions.
-
If the balance weight touch the
floor when the rail is at the top of its lift.
-
Foul the chain pulleys at the bottom
of the lift.
Remedies:
-
Faulty bearing should be removed.
-
The top rail should be cleaned.
-
Worn bevel should be removed.
-
Lift shaft pinion should be properly
secured.
-
Correct setting of the balance weight.
Soft bobbin
Causes:
-
Too quick reducing of the bobbin
speed as the package builds up in bobbin leading frame.
-
Too high speed of top rail, giving
excessive spacing of the coils.
-
Individual soft bobbin may be due
to: Incorrect threading of the roving round the flyer tap. Insufficient number
of turn of the roving round the pressure arm. Lifting bobbin wheel. Removal of
the long length of thick or single roving.
Remedies:
-
Large ratchet wheel or same effect
with spur wheel change building motion.
-
A smaller top lifter change wheel.
-
Correct threading adjustment and
piecing up.
Single and double
Single
may be due to –
-
Slubs in the material being fed may
prevent in passing through the back guide and results in the formation of
single.
-
By piecing the full bobbins to the
wrong end when creeling.
-
By lapping due to rough places or
oil on the roller.
Doubles
may be due to –
-
Broken end at the front lasting into
an adjustment end and being carried forward with it.
-
Long piecing with creeling.
Any
single or double in the previous process may also cause this effect.
Remedies:
Care
must be taken for the above reasons of single and double so that they might not
occur.
Cut roving
Causes:
-
Too close setting between two lines
of drafting rollers.
-
A strained bottom roller.
-
Broken teeth in the draft gearing.
-
Roller gearing set too deeply in
mesh.
-
Badly worn cap bar slides.
-
Loose sections of bottom rollers.
-
Badly pieced roller coverings.
Remedies:
We
should maintain the proper settings of the machine parts.
Slubs
Causes:
-
Waste from the creel or clearers
passing forward with the materials.
-
Loose fly accumulating on top of the
creel bobbins and being incorporated into the roving.
-
Waste gathered in the top and hollow
legs of the flyers.
-
Infrequent or insufficient cleaning
of any port that comes into contact with the material being processed.
-
A broken end at the front, lasting
into an adjacent end, can also produce this defect.
Remedies:
Actions
should be taken accordingly.
Snapping
Snapping
is a severe form of stretching and usually means that the roving being
subjected to excessive tension due to too high a bobbin speed in relation to
the spindle speeds. The roving generally breaks at each pressure eyes.
Causes and remedies:
-
If snapping occurs at an
intermediate stage in the bobbin build, it will probably be caused by
interference to the moment of the cone drum belt. This can be recognized by the
fact that the lift is not being reduced. Check for the waste on the long rack
and ensure that the long rack bowls revolve freely and that the rack pinion is
firmly secured to the upright shaft.
-
If snapping occurs at the end of the
build, it indicates that the ratchet wheel is too large. Thus giving
insufficient movement to the cone drum belt or that the gear train in the spur
wheel type building motion is producing the same effect. This has a cumulative
action, stretching progressively increasing as the bobbin build up until
finally occurs.
-
Too tight cone drum belt can produce
this fault.
Dirt or oil strained roving
Causes:
-
Excessive oiling of rollers,
spindles or bobbin driving wheels may be the main cause of this fault.
-
Cracked or broken bobbins, use of
dirt boxes for transporting roving and oil on the top rail or clearer can also
be lead to stained roving.
Remedies:
Correct
oiling, cleaning etc.
Slack ends
Slack
ends may always be caused by slack winding, a slipping cone drum belt, binding
top rail slides, long collars clogged with waste and dirt, or too many turns of
the roving round the pressure arm.
Incorrect twisting
Poor
twist cause breakage prior to spinning and excess twist cause not to unwind
during spinning in the break draft zone of the ring frame.
Excessive ends down
Causes:
-
Cut drawing.
-
Bobbin jumping.
-
Broken teeth in head stock.
-
Improper humidity.
-
Loose coupling of spindle pinions on
spindle shaft.
-
Cone drums belt slipping.
-
Traverse motion not properly set.
-
Wrapping round bottom and top
roller.
-
Hollow, rough and worn out gearing.
-
Slubs in roving.
-
Cut roving.
-
Improper pressure on the top roller.
-
Waste accumulating in the pressure
eye.
-
Very badly keeping the under and top
clearers.
Remedies:
Steps
should be taken accordingly.
Irregular roving
Causes:
-
Irregular sliver feed to the
machine.
-
Roller lapping.
-
Groove in the top roller.
-
Incorrect distribution of draft in
the drafting zone.
-
Tension draft.
-
Incorrect weighting of the top
roller.
-
Incorrect roller setting.
-
Single instead or double when used.
-
Lack of proper maintenance, oiling,
and cleaning.
Cone drum
As
each layer of roving is added to the bobbin in the speed frame, its diameter is increased. In flyer leading and bobbin
leading frame, it is necessary to increase or decrease the bobbin rpm
respectively to maintain a constant surface speed on the bobbin surface as each
layer is added to its diameter so that the delivered roving can be wound on the
bobbin always at a constant rate. For this purpose bobbin speed is increased or
decreased by moving the belt on the cone drum. Top cone drum is driver and
bottom cone drum is a driven one. Bobbin driving shaft is connected with bottom
cone drum. In case of flyer leading or bobbin leading frame, the belt on the
top cone drum is moved a short step from smaller to larger diameter or larger
to smaller diameter to increase or decrease the bobbin rpm respectively.
Flyer
The
functions of the flyer are as follows –
Twisting
and winding: The roving delivered by the front roller is twisted by the flyer.
The flyer being driven by the spindle is projected through the centre hole of
the bobbin. As the strand of fibres held by the front roller at one end
and the flyer is revolved with the strand round the bobbin at a different speed
so, twisting and winding take place.
Building:
It guides the roving through central hole of the flyer top and a eye at the
flyer gives pressure to a specific place on the bobbin so that, successive
coils are wound on the bobbin without lapping throughout the build of the
bobbin package. The pressure of the flyer applies a certain amount of tension
to the roving as to build a firm bobbin.
Bobbin Tapper
The
function of the bobbin tapper is to produce conical shape of the bobbin being
built up at both ends. As the bobbin build up progressively its lift is
shortened at each reversing of the bobbin rail.
Differential motion
Differential
motion transmits motion from the bottom cone drum to the bobbin with increasing
diameter of the bobbin with the regular change in speed with the instant
movement of the belt on the cone drum. Thus the roving can be wound on the
bobbin without stretching or slackness. This motion acts as a media to transmit
the changing (increasing or decreasing for flyer leading or bobbin leading
frame respectively) speed of the bottom cone drum to the bobbin in a steady
manner with the changing of bobbin diameter and moment of belt on the cone
drum.
The
roller weightings generally applied to the top rollers by weight hung below the
roller beam are about 20 lbs for a double boss front roller, 14 lbs for middle
roller and 10 lbs for back roller, the middle and back rollers may be suddle
weighted (spring weighted) and in this case the applied weight is about 20 lbs.
Heavier weightings are helpful to deal with the occasional thick ends and
piecing in the creeled material to make even material.
Top
roller weighting are very important in all the cases where the roller drafting
are employed due to –
Over weighting contributes in the:
-
Production of roller – Jam between
the drafting rollers.
-
Excessive ends down.
On the other hand under weighting
produces:
-
Irregular material (sliver, roving
and yarn).
-
Insufficient parallelization of the
fibres.
-
Insufficient straightening of the
fibres.
-
Slubs in the material.
-
Waves in the sliver.
The advantages of spring weighting
and top arm over dead weighting are as follows:
-
The roller beam is feed from the
multiplicity of weight wires and hook and is therefore easier to keep the
machine clear.
-
The top rollers are positioned more
exactly over the corresponding bottom rollers.
-
The top rollers are held by top arms
and can be swung out of the way easily.
-
The pressure applied is independent
of the roller setting.
-
The weighting is commonly even
greater with synthetic rubber covering top roller than that in the old method
of weighting in order to avoid from stoppages by bad drafting.
What
are the Objects of Speed Frame?
-
To insert small amount of twist to form strand known as roving. The
twist being adequate to held the fibre together.
-
To wind the twisted strand or roving
on to an upright bobbin suitable for creeling at the next process.
The
package so produced is tapered or conical at each end and made sufficient firm
so that it can be transferred without damage to the roving and yet will unwind
readily at the next machine.
What
are the operations involved in Speed Frame?
The
following operations are involved in speed frame –
-
Drafting: The draw frame sliver feed to the speed frame is reduced in
size by the action of drawing and drafting. So that, the reduced size of the
roving is within the drafting range of the ring frame.
-
Twisting: Spiraling the fibres around each other about the axis of
the strand so to bind themselves together to impart sufficient strain, to
enable it to build-up in the form of a suitable package, convenient to handle
from one process to another. Here, the amount of twist used should be just
sufficient to hold the fibres together but it should preclude drafting in the
ring frame.
-
Laying out: To put the coils on the bobbin in regular arrangement so that,
no over lapping or excess spacing between the coils can occur. The coils are
laid side by side throughout the build of the bobbin. This operation is done by
alternate reversing motion of the bobbin rail.
-
Winding: To put successive layers of roving on the bobbin at a proper
rate of speed. The speed being governed by the building motion with the help of
differential motion.
-
Building motion: Shortening of successive layers of roving to make conical
ends of the package with the help of building mechanism.
Roller
setting is a very important task in the spinning department. Incorrect settings
lead to creation of various problems and hampers spinning conditions. The speed
of the leading roller is always greater than the preceding roller. Incorrect
setting leads to the variation of weight/unit lengths. If the setting between
two pairs of drafting roller is closer, than that required, the leading end of
the fibres will caught by the front pair of roller and back end by the
preceding pair of rollers, results in fibres breakage. The broken fibre is
naturally shorten in length & create drafting wave irregularity in the
material and frequently ends down in speed frame & ring frame. Closer setting produces slubs in
roving, yarn, roller laps, and gum between the drafting rollers. On the other
hand wider setting produce irregular motion of fibres mostly short fibres which is a cause
of irregularity. Too wider setting also fails to bring the fibres in parallel
and regular arrangement so, produce roving yarn of poor strength and
appearance.
To obtain efficient drafting, immediately
the tailing end of a fibre is released by one pair of roller,
its leading end should ideally be gripped and accelerated by the succeeding
faster pair of rollers obviously, this is not possible if the roller setting is
greater than the fibre length.
In
roller setting the following factors must be kept in mind –
Length
of the fibre:
The
space between two pair of rollers must be slightly greater than the average
length (modal length) of the fibre under processing.
Bulk
of the materials:
As the bulk increase the distance between the
drafting roller increase and vice-versa. Otherwise the top rollers will strip
and introduce irregularities.
Frictional
properties:
If
the frictional properties of fibre are higher for the same staple length and
bulk, the roller setting need to be increased. For irregular fibre length the
best setting is a compromise between the longest and shortest fibre.
The setting becomes progressively closer
in passing from the sluber through the intermediate to the roving frame. In a 3
– line roller system, the setting between the back and middle pair of rollers
is not important in the view of the small draft applied at this stage. This
setting is usually about 1(5/8)th inch for the short staple and 2 inch for the
long staple. On the other hand, magnitude of the setting between the middle and
front roller is important. At the sluber, the setting is about 1/8 th inch to
3/16 th inch in excess of the effective length of the fibre; at the
intermediate frame 1/32 th inch less than that at the sluber and at the rover
1/32 th inch less than that at the intermediate frame. On the two zone simplex,
the setting used for the two zones are about the back zone and the same as
those on any intermediate at the front zone.
The simplex/roving frame is a necessary evil
The simplex/roving/speed/fly frame is used as necessary evil or Reasons for using simplex
The simplex or roving frame is a modern
form of speed frame. It is also known as fly frame. It is capable of imparting
higher draft to material (up to 25). One of the noticeable features of this m/c
is to absence of sound & noise. The higher speed of this m/c (spindle speed
about 1500 r.p.m) results in increased production up to 50%. It also offers
higher output package capacity.
Draw frame produce a sliver which have all the features for creating a yarn such as an orderly, clean strand of fibres lying parallel to each other. But this sliver is not used as feed material in ring spinning frame.
In fact, the roving machine is a
complicated one, liable to faults, causes defects, adds to production costs and
delivers a product that is sensitive in both winding and unwinding. Yet speed
frame is used mainly for two major reasons –
a. The first reason is to
insert required draft to sliver. Drawn sliver is a thick and untwisted strand
of fibre which needs 300~500 draft to be changed to yarn. But yet there is no
machine to impart such great amount of draft to the sliver. Again if, this draft
can anyway be imparted, the sliver will eventually break and create
irregularity.
b. The second reason is
that, D/F can represent the worst form of material to feed in ring spinning
frame.
Moreover, if we consider the task of
a roving frame/simplex, then we can see that it performs three main tasks –
a. Attenuation (draft) of
the sliver (the chief task).
b. Insertion of twist to
hold the fibres in the sliver &
c. Winding the roving
into a package that can be transported stored & feed to the spinning frame.
The third task has no contribution
directly to spinning. Furthermore, it is the winding operation that makes the
roving frame a relatively complex and a trouble plugged m/c. This winding
motion requires in addition to the spindle & flyer, a cone-drive
transmission (or variable gear), a different gear and a builder motion.
Again, the twist inserted in the
roving should be removed first in the next process prior to final attenuation
which also adds further complication.
For this reason, for years together
the textile engineers are trying to subtract speed frame from spinning process,
but still not fully successful. So, the speed frame is used as necessary evil.
Different changes take place in the speed/roving/simplex frame and affects in yarn count. Now we are discussing about it –
Draft change pinion (D. C. P): A large wheel reduces the draft and
so gives a coarser hank (where the D. C. P is a driven one).
Draft constant change pinion: The larger the draft constant
change wheel, the greater the draft constant.
Twist change pinion (T. C. P): A large wheel reduces the turns per
inch (T. P. I) by increasing the both front roller delivery and the bobbin
speed without affecting the spindle speed.
Twist constant change wheel (T. C.
C. W): The
larger the twist constant change wheel, the greater the twist constant.
Lifter change wheel (L. C. W): A large top lifter change wheel
speeds up the lifter shaft without affecting the bobbin speed and thus increase
the spacing of the coils. This wheel determines the number of coils/inch on the
bobbin.
Bottom cone drum change wheel: This wheel is changed to obtain
correct winding on the empty bobbin. A large wheel gives tighter winding. The
winding wheel determines the initial bobbin speed.
Spur wheel change building motion: This can be used instead of ratchet
wheel. With the spur wheel change building motion a finer hank requires either a
large wheel in the top position or a smaller wheel in the bottom position.
Ratchet wheel: The finer the hank, the greater the
number of teeth in the ratchet wheel. The ratchet wheel controls the bobbin
speed after the initial speed of the bobbin.
Tapper change pinion: A large pinion gives more tapper to
the bobbin.
Spindle speed change wheel: The larger the spindle speed change
wheel, the slower the spindle speed.
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