active ribbon breaking in random winding

8/3/2019 Active Ribbon Breaking in Random Winding

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When the package is subsequently used as raw material to a textile production

process, it is important that the yarn unwinds with uniform ease. In order to achieve

this, the winding operation should maintain a constant level of tension in the

yarn being wound, as well as achieve a uniform spacing between successive turns of

yarn.

The grooved drum type yarn winder, shown schematically by Fig. 2 is widely usedin the textile industry. The main feature of the winder is the cylindrical winding

drum, which has a continuous helical groove. The yarn package is driven by contact

with the drum surface and the yarn being wound is guided by the groove under the

winding tension given to the yarn. As the drum rotates, the groove provides the

traverse movement to the yarn, so as to give the package its width. The surface speed

of the package and hence the yarn winding speed remains practically constant as the

drum speed is kept constant. Due to its mechanical simplicity, this type of winder is

very reliable in operation and is commonly used in the winding of most types of

yarn, except those having continuous filaments which are prone to damage by

friction.The wind ratio w is a useful parameter applicable to a random winder, defined as

follows.

w Np

Nd

k

which can be written, assuming no slip between the drum and package, as

w kDd

Dp

Fig. 2. Basic random winder.

Fig. 1. Cylindrical cross-wound yarn package.

1226 G. Durur, P. Bandara / Mechatronics 12 (2002) 12251238


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where Np is package rotational speed, Nd is drum rotational speed, Dp is package

diameter, Dd is grooved drum diameter and k is the number of drum rotations re-

quired to produce a complete traverse cycle (i.e. a double traverse) of yarn. For a

grooved drum, k is an integer, usually in the range 16.As seen from the above relationship, on a grooved drum winder, w gradually

diminishes as the package diameter increases during winding. This has the effect that

the circumferential spacing between the yarn turns of two successive double traverses

has a continuous variation. As a result the yarn visible on the package surface seems

to be randomly spaced with respect to one another. For this reason the grooved

drum winder is often referred to as the random winder. The wind ratio may be as

high as 12 at the beginning of winding a package, and could become 1 or less as the

package diameter becomes large.

The constantly diminishing wind ratio as indicated above causes a winding

problem. Each time the wind ratio passes though an integer value, a double traversefinishes at the same position on the yarn package as where it started. So successive

coils of yarns coincide with one another, and this effect persists till the package di-

ameter increases sufficiently as further yarn is wound. This overwinding causes the

package shape to distort as well as make the unwinding of the yarn from such places

more difficult. The effect persists for longer as the package diameter increases.

The overwound turns of yarn tend to form a hard band, and hence the problem is

termed ribboning or patterning. Some noticeable ribboning occurs even when the

wind ratio differs from an integer by one half, one third etc., but this effect is less

severe, when compared to major ribboning corresponding to an integer value of

wind ratio.There are several techniques applied on random winders to diminish the intensity

of ribbon formation. These achieve ribbon breaking by causing a small amount of

slippage of the package on the winding drum at frequent intervals thereby dispersing

the yarn that otherwise tend to bunch together. However this mechanically effected

action can be called passive, in that the moments of its application are simply

periodic and not coincident with those when ribboning occurs. The effectiveness of

ribbon breaking achieved is therefore not optimum.

2. Research objectives

The research work reported in this paper was intended to investigate means of

improving the effectiveness of ribbon breaking on a standard random winder by

applying such action precisely at the times when ribboning actually occurs during

winding. For this reason it was necessary to provide the winder with the capability of

detecting the onset of major ribboning, whenever it occurred.

3. Experimental apparatus

The detection of ribboning can be based on reading the rotational position of the

package when the drum starts a double traverse. If the package rotational position

G. Durur, P. Bandara / Mechatronics 12 (2002) 12251238 1227


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were to be found much the same at each successive arrival of the yarn at the same

reference position of traverse, then clearly there is overwinding of successive yarn

turns which causes ribboning.

A Schlafhorst Autoconer type GKN winding unit was modified [2] by the addi-tion of several sensors and actuators to enable its control by a PC. An 8-bit shaft

encoder was attached to the winding drum as well as to the package spindle. 8-bit

resolution was found adequate to detect the rotational position of the grooved drum

and the package for the detection of ribboning. On this winder, the drum diameter

was 90 mm. The traverse length was 125 mm and the drum rotated 3 turns to

produce one double traverse of the yarn (i.e. k 3).

The package radius was sensed using a light, 25 mm wide roller carried on an arm

attached to a conductive plastic track potentiometer, as shown by Fig. 3. An LVDT

was mounted on the winder frame to provide a reading of the height of the package

spindle. Since some pressure is maintained between the package and the drum usinga weighted arm, the radius of the package at the driving point on the grooved drum

is slightly reduced. The LVDT was calibrated to indicate this compressed radius.

This basic winder is fully mechanical in operation and ribbon breaking is achieved

by use of a clutch, which is used to briefly disconnect the drive to the grooved drum

every few seconds. At each power disconnection the drum and the package slow

down a little. The re-engagement of the clutch accelerates the drum faster than the

package so producing some slippage of the package on the drum. The ribbon

breaking action is due to the resulting dispersal of the yarn that would otherwise

bunch together. Since the ribbon breaking action takes place continually whether

ribboning is present or not, this ribbon breaking action may be considered passive.Since the occurrence of ribboning could be detected by the PC according to the

method indicated above, it followed that ribbon breaking action could be made to

coincide with those intervals, under PC control. Two methods of investigating this

Fig. 3. Configuration of the modified winder.



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possibility were provided for. One of these was the replacement of the standard drive

motor by a DC-brushless motor [1] which could be driven as to produce sharp

changes of drum speed when so required, under software control. The other was to

provide a package lifting arm attached to a geared stepper motor, which could beused to lift the package minutely off the drum at rapid intervals when required.

Yarn winding tension could be set on the winder using a disc type tensioner. The

actual tension level was set with reference to an electronic single yarn tension probe.

This device had a range of 0100 g and a bandwidth of 2500 Hz. It provided an

analogue voltage output, and was also used in yarn unwinding trials described later.

All the above devices were interfaced to the PC for data acquisition and control

purposes. These modifications resulted in a random winder that offered considerable

scope for its mechatronic control.

4. Experimental work and results

The experimental work undertaken on the modified winder, and the results ob-

tained were as follows.

4.1. Study of the rotation of the package on the drum

The rotation of the package was of interest as the package was likely slip on the

winding drum, possibly in a random manner, as the winding is done against thetension of the yarn being wound, with the drive to the package being provided by

friction with the drum. The two shaft encoders provided on the winder enabled the

tracking of the rotational position of the drum and the package at a fast rate so as to

show any slippage present, as described below. In this study, a wool yarn of ap-

proximately 30 Tex (linear density in g/km) was used, which was wound at a speed of

450 m/min. At this winding speed each double traverse took about 140 ms. The

reading of the shaft encoders by the PC, even with error checking to eliminate oc-

casional incorrect readings due to electrical noise, took only about 1.7 ls per reading

and allowed the above procedure to be satisfactory.

The apparatus was first used to study the winding process with no ribbon

breaking applied. It quickly became apparent that by plotting the binary value of

angular position of the package spindle at each successive start of a double traverse

on the VDU of the PC, a characteristic diagram was obtained. This was found to be

useful for following the progress of the winding operation and was referred to as the

angle at double traverse (ADT) diagram.

By rotating a package of constant diameter at the normal speed (i.e. a package on

which no additional yarn is wound), a very regular dot pattern is shown by the

diagram (Fig. 4). The dots correspond to the package spindle position at the start of

over 500 successive double traverses. The inclination of the straight line formation ofthe dots depends on the particular value of wind ratio corresponding to the package

diameter.



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The constant vertical spacing between successive points on this diagram (this is

the separation between a point and the one almost vertically below it, corresponding

to the next double traverse) shows that the package rotational speed is highly con-

stant. Even with some mechanical drag introduced on the package spindle by use

of a light aluminium pulley and weighted cord, the pattern remained unchanged.

Slippage took place only when the level of drag was increased to a level considerably

higher than that corresponding to the normal winding tension. Theoretically, a small

amount of loss of rotation seems possible due to the deformation of the package

surface under the pressure maintained between the drum and the package [4], but the

diagram shows that any such effect has no random character.

When winding a package normally i.e. with its diameter gradually increasing, but

with ribbon breaking measures still disabled, the slope of the lines gradually

changes, as seen from Fig. 5.

Fig. 4. Rotation of constant diameter package with no drag (diameter 80 mm, wind ratio 3.4).

Fig. 5. Winding of package at wind ratio 3.3.



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Depending on the actual value of wind ratio reached, the dots form a single peak

or several of them. Where a single peak is seen, the wind ratio has an integer value at

that package radius; where three peaks are seen, the wind ratio is an integer plus 1/3

etc. When the ratio is an integer, the ribboning that takes place is most undesirable(major ribboning). Ribbon breaking is mostly required at these intervals. Where the

ratio is high, and not an integer, any ribboning that takes place (minor ribboning)

quickly disappears. When the wind ratio descends to values such as 3 and 2, even

minor ribboning tends to persist longer.

4.2. The effectiveness of different ribbon breaking methods

It is actually major ribboning that causes significant difficulties with unwinding,

and hence that requires dispersal. The moments of major ribboning can be detected

by software using the package diameter and shaft encoder readings, and ribbon

breaking can be effected actively as compared with the passive ribbon breaking

normally applied. The scheme of detecting ribboning by software, and of imple-

menting the ribbon breaking by the package lifting method described later, are given

in the Appendix A.

The ADT diagram was used as an aid to show the effect of the three different

ribbon breaking methods tried out in this work. The basic method of interruption of

the drive to the drum, as provided on the basic winder was the first method tried.

Next, the DC-brushless motor provided on the winder was used to introduce speed

variations to the drum directly, during those intervals when major ribboning is de-tected. Finally, the drum was driven at a constant speed and the package lifting arm

arrangement was used to lift the package off the drum surface repeatedly during

intervals of major ribboning. The winding was carried out at a speed of approxi-

mately 450 m/min.

Fig. 6 shows the variation to the package formation introduced by the use of the

standard ribbon breaking arrangement using the clutch, at the wind ratio value of 3.

Fig. 6. Effect of normal ribbon breaking at wind ratio 3.0.



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Some dispersal of the yarn coils is evident from the diagram. The examination of the

package showed this but the level of remnant ribboning was quite distinct.

The drum was then driven directly by the motor, with the mechanical declutching

action stopped. When major ribboning was detected, the motor was controlled by

software to drop its speed to half its normal value for a brief period, and then back

to the normal value for a longer duration. These actions were applied repeatedly till

the wind ratio fell sufficiently below the integer value concerned. Fig. 7 shows the

results of this method of active ribbon breaking. There is more effective ribbondispersal, in comparison with Fig. 6, and this was confirmed by examining the

package. However the operation was noisy due to the sharp speed fluctuations

produced by the motor, which was undesirable.

The method of briefly lifting the package off the drum surface using the lifting arm

was then tried. The action was repeatedly applied, as with the previous method. The

operation was much quieter, and the more effective ribbon breaking due to this

method is shown by Fig. 8. Examination of the package showed the greater thinning

out of the ribboning, that was achieved.

4.3. Evaluation of the ribbon breaking methods

The ADT diagrams above provide a visual evaluation of the three ribbon

breaking methods tested, indicating that active ribbon breaking by lifting the

package provides greater effectiveness.

As a yarn package is only an intermediate product in textile processing a more

meaningful measure of the goodness of winding a package is the uniformity of un-

winding tension obtained, when yarn is withdrawn under some specified conditions

[3].

A number of similar yarn packages were prepared under the same winding con-ditions using each of the above three ribbon breaking methods. These were unwound

using the apparatus shown by Fig. 9. The tension of the yarn during unwinding it at a

Fig. 7. Effect of active ribbon breaking by fluctuating motor speed at wind ratio 3.0.



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speed of 480 m/min was recorded using a single yarn tension meter placed as shown in

the figure. The unwinding tension arises from the rotation (ballooning) of the yarn as

well as the movement of the yarn between the front and the back of the package. The

yarn will experience an increased drag when it is removed from places where rib-

boning is present. The tension meter had a natural frequency of 2.5 kHz, and tension

readings were recorded as 8-bit data values, to provide some 1 M readings per

package. The leaf tensioner was adjusted to provide a minimum level of tension of the

yarn. All settings of the apparatus were kept the same during this unwinding trial.The results obtained for each type of package were averaged, and were used to

construct a histogram of withdrawal tension, as shown by Fig. 10. Unwinding

Fig. 9. Apparatus for measuring unwinding tension.

Fig. 8. Active ribbon breaking by lifting the package at wind ratio 2.0.



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tensions vary over a range of values as can be expected. The graphs show that active

ribbon breaking by lifting the package provided the lowest modal tension.

5. Conclusions

The ADT diagram is a useful visual aid in the study of random winding of yarn by

the grooved drum method. The studies carried out showed that no irregular slipping

of the yarn package takes place under the normal winding tension values applied,

despite the indirect (friction) drive applied to the package. The ADT diagram was

particularly useful in studying the effectiveness of the three ribbon breaking methods

reported in this work.

As the standard ribbon breaking methods provided on random winders are not

based on the detection of ribbon formation, it was felt that active ribbon breaking as

described above would prove to be more effective. This was in fact found to be the

case by comparing the unwinding tension measured on similar yarn packages pro-

duced by the three methods attempted.

The standard grooved drum random winder will continue to be used by the textile

industry due to its rugged simplicity and its suitability for use in automatic winders

[5]. As the cost of microprocessor control has become relatively low, methods of

active ribbon breaking similar to those reported here will prove to be useful in

producing better yarn packages.

The method of lifting the package off the drum for brief intervals was found to bethe most effective for ribbon breaking, when used actively as described. This

method has a disadvantage due to the increasing package radius as winding pro-

Fig. 10. The results of unwinding yarn tension.



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gresses, as the lifting arm has to constantly follow the rising package arm position. In

this work an arm attached to a geared stepper motor was successfully used to im-

plement the procedure. This was effective, but a simpler mechatronic solution is

desirable.

Appendix A

Key to Symbols used in flowcharts for software program:

k drum rotations within double traverse (02)

y number of double traverses produced

l no. of double traverses for diagram (0500)

rib variable to indicate stage of ribbon breaking (0 no action required)

(16 stages of arm movement)

lift_step, stop_step time duration of arm movements expressed in double traverses



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References

[1] DC Brushless Motor DM-20 and BRU-200 Servodrive. Electro-Craft Ltd., Fourth Avenue, Crewe,

UK.

[2] Durur G. PhD thesis. University of Leeds, UK, 2000.

[3] Nobauer H, Baumeler M. Measurement of unwinding resistance of yarn packages using the package

performance analyser. Textile Praxis International 1992;November:103440.

[4] Osawa G, Koyama T. On the slippage between yarn-package and grooved drum during winding.

J Textile Mach Soc Jpn 1972;25(6):T11323.

[5] Rebsamen A. Modern package building. Textile Asia 1988;September:1306.


active ribbon breaking in random winding

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