Compact spinning
system:
Why
does compact spinning technology require in the ring spinning process?
· The main reason of the fibres migration in the conventional ring spinning process is the tension difference between fibres during the yarn formation.
· When the twist is inserted into the ribbon like fibres bundle and the yarn formation takes place.
·The fibres at the edges of the fibres bundle face with tension and the fibres in the middle of the fibres bundle are subjected to compression unless there is excessive yarn tension.
· To
release the stress, fibres subjected to tension try to shorten their path
length in the yarn while fibres under compression try to lengthen it.
· As a
result of this, fibres leave their perfect helical path and migrate between
layers of the yarn.
· In the other words, a long spinning triangle results in a longer weak point, and thus more end breaks in the at ring frame.
· However, with a long triangle, fibres are better bound into the yarn.
Objectives
of compact spinning:
· The main objective of the compact
spinning is to eliminate the spinning triangle because the fibres migration problems is associated
with the size of the spinning triangle being formed in the conventional ring spinning process.
·The tension
difference among fibres during twist insertion is small in ring
spinning equipped with compact spinning system due to the almost elimination of the spinning triangle.
·Therefore fibre migration in compact yarns
could be expected to be less than that in conventional ring spun yarns.
· Klein
has found out that a short spinning triangle represents a short weak point
and thus fewer end breaks.
·If the spinning triangle is too short and the deflection of
the fibres on the edges has to be very sharp during the binding-in.
· This
is not possible with all fibres. Therefore a very short spinning triangle
results in some fibres on the edge not to be integrated into the yarn,
resulting in loose fibres or ‘fly’.
· Other
fibres on the edge might be bound-in at one end only, causing hairiness.
·Compact spinning produces a smoother yarn and less fly.
Different
types of compact spinning devices:
There are mainly three kinds
of compact spinning devices which are described as below:
Suessen
EliTe compact spinning system:
·This
system consists of an additional ‘drafting zone which is mounted on a standard
three-roll ring spinning machine.
·An air-permeable lattice apron runs over a suction tube in this drafting zone .
·The
suction tube is under negative pressure and there is a slot tilted in the
direction of fibres movement for each spinning position.
· When the fibres leave the front roller nip line, the lattice aprons guides the fibres over the openings of the suction slots.
·The fibres move sideways and condense due to suction air flow.
·The openings
of the suction slots get inclined to the direction of fibres flow.
·These suction slots inclination help to condensing by generating a transverse force on the fibres band during
their transport over the slot, causing the fibre band to rotate around its own
axis.
·The
lattice apron carries the fibres attached to it up to the delivery nip line.
·The
diameter of the delivery (driven) top roller is kept slightly bigger than the
diameter of the front bottom (driving) roller.
·The difference of diameter between delivery top roller the front bottom roller generates a tension in the longitudinal direction during the condensing
process.
·The tension ensures the straightening of curved fibres, and therefore supports the condensing effect of the negative pressure.
Rieter K44 ‘ComforSpin’ compact spinning system:
·The
compact spinning concept illustrated in the figure is the one represented by the
Rieter ‘ComforSpin’ process.
·Aerodynamic forces are used to laterally condense the drafted
fibres ribbon after the main drafting zone in this system.
·As a
result of the aerodynamic forces, the spinning triangle becomes so small or it gets almost eliminated.
·The Rieter K44 ComforSpin machine consists of a
three-roller, double-apron drafting system.
·The exit zone of this system is modified to allow fibre condensation.
·The exit roller is replaced by a perforated drum (1), within which is a stationary suction unit that is connected to the machine’s central extraction unit (2).
·The fibres delivered by the exit nip line of the drafting system are held on
the surface of the perforated drum, moving at the drum’s peripheral speed.
·In this way, the ComforSpin technology allows aerodynamic parallelization and condensation
of the fibres after the main draft.
·The
spinning triangle is reduced to a minimum in this compact spinning system.
·The compacting zone is the heart of the machine which consists of the perforated drum, suction
insert, and air guide element.
·The
positively driven perforated drum gets hard-wearing and resistant to fibres clinging.
·There is an exchangeable stationary suction insert with a specially shaped
slot inside each drum.
·This drum gets connected to the suction system of the machine.
·The
air current created by the vacuum generated in the perforated drum condenses
the fibres after the main draft.
·The
fibres are fully controlled all the way from the nip line after the drafting
zone to the spinning triangle.
·An
additional nip roller prevents the twist from being propagated into the
condensing zone.
· The compacting efficiency in the condensing zone is enhanced by a specially designed and patented air guide element.
Zinser AIR-COM-TEX 700® compact spinning system:
·This system also works on the basis of eliminating the spinning triangle.
·The conventional three cylinder drafting system is used in this technology.
·The
fibres emerge from the drafting system and get condensed under suction onto the
surface of a perforated belt.
·The
condensed fibre strand undergoes a substantial reduction in width prior to
twisting.
·This
reduction in the difference between the width of the fibres emerging from the
drafting system and the yarn diameter effectively eliminates the spinning
triangle.
·The
compacting zone can be adapted to the raw materials by the adjustability of the
additional feed, because the compacting zone between the two front cylinders
can be influenced by a lower speed of the perforated apron with maximum –4.0%.
For the cotton compact spinning process, from 0 to 4% additional feed is
required from a technological point of view.
· The machine can be optimally set to the most fibres with this spectrum .
·This
has a positive influence on the position of the individual fibres, since only
unstressed and parallelised fibres can be deflected and compacted.
Advantages of compact spinning:
·The
reduced hairiness level.
·Ability
to produce yarns of enhanced strength.
·Improved
elongation at break even with lower twist levels.
·Softer
feel due to low twist.
·The compact spinning process produces a new
ring-yarn structure which is close to the idealized staple fibre yarn
construction.
·Better
fabric appearance
· Improved performance in weaving stage.
·better utilization of the raw material.
· Higher delivery rates can be achieved.
· Cost savings in the downstream processing stages.
· Improves machine efficiency due to low end breakages rate.
·It is therefore possible to use low quality cotton while maintaining yarn strength equal to that of conventional ring spun yarn with the same twist level.
Limitations
of compact spinning:
·The
only limitation of compact spinning is that the rehabilitation from
conventional ring spinning to the compact system needs more investment.
·Importantly,
there are concerns about the negative influence of the low hairiness.
·A study pointed out that the reduced hairiness might lead to more frequent
traveler change, since hairs protruding from the yarn body provide lubrication
and a cooling effect on the traveler and thus reduce traveler wear.
·This
issue questions the economics of the compact ring spinning process.
·A study shows that it is effective only for longer (or combed) fibres (Kampen, 2000).
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AIRJET/ VORTEX SPINNING METHOD (A OPEN END SPINNING PROCESS)
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