Nonlinear Phenomena in
High-Speed Yarn Spinning
Introduction
Yarn rotates at high speeds in many textile
manufacturing systems as spinning, overend unwinding and twisting.
Thesurface of rotation generated by the spinning yarn forms a 'yarn
balloon'. The balloon shape characteristics andoperating speeds
govern the yarn tension. Yarn strength limits the maximum tension
and therefore the operating speedand productivity of the system.
Accurate models and physical understanding of the balloon dynamics
lead to optimized yarn manufacturing and handling systems that
minimize the tension and the tension variation and
maximizeproductivity.
Research activity
Research being done is an experimental study of
the yarn balloon. A yarn balloon test system(YBTS), constructed
inthe lab, generates yarn balloon and measures the yarn tension and
balloon shapes. The YBTS comprises of fourcomponents: The test
stand, signal interface box, PC and power amplifier. A four bar
linkage mechanism rotates yarn at constant speed, without twisting,
to produce a yarn balloon. Operatingspeed varying from 0-10,000 rpm
are controlled by the operator. The test system accurately measures
and records fourquantities: rotation speed , upper eyelet tension,
yarn length and balloon shape. Length of yarn in the system
iscontrolled by the yarn length motor. Power to drive the two
motors is generated by the amplifier. All controls and datasignals
pass through the signal interface box. The PC is host to a high
speed digital signal processing board whichperforms all controls
and data acquisition functions.
Experimental analysis: A variety of experiments
are done using the YBTS. The experimental results are then
comparedwith the theoritical results.
1. Low speed experiments: A heavy nylon string
with linear density of 1.215 gms/m is used for the experiments.Yarn
is rotated at 1000-1300 rpm. The model neglects air drag and yarn
elasticity. The string is approximatelyinelastic in the tension
region of the experiments. Low rotation speed and high yarn linear
density yield low ornegligible air drag. Eyelet tension and yarn
length are converted to non-dimensionalised parameters. Figure 1
showsthe experimental and theoritical results of plot between the
nondimensionalised parameters tension (Pe) and yarnlength (delta)
at three different speeds. It is seen that after a particular value
of delta, the eyelet tension startsincreasing.
FIGURE 1
2. High speed experiments: These experiments
neglect the yarn elasticity but do take the air drag into
account.Dacron continuous filament polyester (POY) is used in the
experiments. Data is collected for one, two, three and fourstrand
i.e different linear densities of POY at 3000, 5000 and 7500 rpm.
Figure 2 shows the experimental andtheoritical curves of Pe versus
delta for single strand dacron at the three specified speeds. The
downward pointingarrows show the jumps in tension corresponding to
the collapse of the balloon from a single loop to a double loop
andfrom a double loop to a triple loop. The upward pointing arrows
show the jump of balloon from triple to double andfrom double to
single loop as yarn is being removed from the system.
FIGURE 2
Figure 3 shows the theoritical and experimental
curves for 2 strand POY at the specified speeds. A lot of flutter
(intension) is seen in the region where the balloon jumps from a
double loop to a single loop, as yarn is removed fromthe system.
(Please see the flutter experiments for detail).
FIGURE 3
3.Air drag experiments: In these experiments the
air drag characteristics of POY are analyzed. The effects of
spinningspeed and yarn linear density on the non dimensionalised
yarn air drag coefficient, Dn, is studied. The coefficient of
airdrag is calculated and compared to drag characteristics of a
cylinder in a fluid cross flow.
4. Be on the look out for "ELASTICITY
EXPERIMENTS".
