by
Dr. H.R. Sheikh
Professor, Textile Institute of Pakistan

Spinners always endeavour to achieve a very high standard of process efficiency and product quality at the preparatory stages, ring shed and in the cone winding department so that the final yarn package delivered to the end-user meets his stated specifications as well as performance criteria.
Modern automatic cone winding machines facilitate achievement of these objectives of the spinners by extracting all disturbing yarn faults and producing packages of constant length and after paraffin waxing of the yarn if required.

However, the end-users also require guarantees from the spinners that the packages delivered to them are free from ribboning or patterning effect! Freedom from ribboning is an extremely important requirement of the end-users because it confirms that the yarn can be unwound from the packages smoothly at high speeds and achievement of high standard of machine efficiencies is possible during warping, weaving and knitting.

1. How is ribboning or patterning produced? Most of the present day automatic winding machines incorporate grooved drums to traverse and wind the yarn onto the package. Ribboning is difficult to avoid when grooved drum is used. Suppose the drum shown in fig. 1 makes      revolutions per double traverse of the effective winding point and revolves at (N) R.P.M. The package revolves at (n) R.P.M. The diameters of the drum and the package are (D) and (d) respectively. Neglecting slippage between the package and the drum, the surface speeds of the two should be equal, i.e. PDN= Pdn or DN=nd -------------------(i)

Time taken by the drum for     revolutions per double traverse = minutes. During this time interval package will rotate =     / N

revolution now n/N can be substituted by D/d on the basis of (i).        Hence, during the time interval for one

double traverse, the package will rotate times -----------------(ii)         i.e. number of revolutions of the package which will be equal to the number of coils laid on the package per double traverse. In the above       & D equation are constant during the formation of any package but (d) increases continuously. Obviously there will be times when the number of coils laid on the package will be a whole number. In such situations coils of yarn will be wound one on top of the other or very close to each other. Surface of such a package will exhibit a ribboning or patterning effect leading to the following disadvantages.

. The density of the package will be uneven and therefore unsatisfactory for dyeing purposes.

. The package will have poor unwinding properties. On unwinding many coils will come off together i.e. slough off the package. Sloughing off of the coils from the package is a source of end-breakages in warping and weaving. In case of knitting machines, this may damage the needles.

Thus, it is obvious that pattern or ribbon breaking mechanisms, are an indispensable part of modern automatic winding machines. All major manufacturers of winding machines have developed `state of the art' machines, which include sophisticated devices to prevent ribbon formation and facilitate production of ribbon-free package. The operating principle and function of some of the pattern/ribbon breaking devices is described as under:

2. Propack® system Propack® is a new cradle anti-patterning system incorporated by Schlafhorst in the automatic package winding machine Autoconer 338 launched in 1997. The entire product range has been available since ITMA Paris in 1999. As already mentioned patterning occurs when the number of coils laid on the package per double traverse is a whole number. In other words, pattern zone is reached when the ratio between drum speed and package speed reaches a critical value.

The ratios between the drum and the package speeds are constantly determined by the highly precise winding unit computer of the propack system illustrated in Fig. 1.

The superior performance of the Schlafhorst Autoconer 338 has been accepted in terms of quality of the wound package and machine productivity world wide. There is an increasing trend in the spinning sector of the textile industry of Pakistan to replace the manual winding machines with Schlafhorst Autoconer 338.

4. Double pitch drum

Muratec Mach Coner, introduced in 1979, has been completely redesigned recently and is being marketed as Murata's new generation process coner. The anti-patterning device has also been redesigned. A new winding drum with two distinct pitches on the same drum eliminates patterning (ribboning) and facilitates high speed un-winding at the subsequent processes. Muratec claims that package wound on the process coner meets the final criterion of quality which is high speed unwinding property in the ribbon critical zone. Some of the other new devices incorporated in the new Murata Process Coner are Peral-A which contributes to energy efficient operation, Perala-D which reduces yarn hairiness, the

5. Anti-patterning modulation

"On-OFF" type electronic modulation is a regular device incorporated in all models of Orion automatic winders marketed by Savio. Drum and package speeds are constantly adjusted so that the speed ratios do not reach critical values and patterns on the package are minimised.

6. Computer Aided Package (C.A.P®)

C.A.P® is an electronic type modulation with computerised control of the drum package diameter ratio. It is offered as an optional device by Savio. It is claimed that with C.A.P® Orion winders produce perfect packages with- out patterns. Consequently, no unwinding speed limits are imposed in the subsequent processes of warping, knitting and dyeing. Some of the other devices which make Orion automatic winder, a `state of the art' machine, are Inspector Control, Tensor, Balloon Breaker, Booster (optional etc. The most prominent feature is the positioning of the Electronic clearer as the last device on the yarn path. Any long or moire defects are detected by the clearer and eliminated being sucked from the package.

7. Precision winding with counter-rotating blades: Two counter-rotating blades are used on the SSM-PSM-51 Precision winder Fig.-4 (a) and 4 (b) for traversing the yarn and deposit on the cylinderical package. The blades rotate at constant speed and traverse the yarn alternately to wind it on the package smoothly and gently. The required density profile of the package is achieved by correct choice of the wind ratio which remains constant. The wind ratio prevents the number of coils per double traverse reaching a whole number effectively from empty to full package. Consequently no ribboning or patterning is produced on the package. The crossing angle becomes progressively narrower as the package diameter increases. Fig. 4 (C). Some of the other advantages claimed for precision wound packages are:

· 20% more yarn on the package as compared to random wound packages

· Better dye penetration, less yarn breakages in subsequent processes, higher unwinding speeds are achievable.

· Packages can be used directly for dyeing without rewinding.

In conclusion, it may be stated that the foregoing account of the anti-patterning devices incorporated in their automatic winding machines by the major winding machinery manufacturers to produce ribbon-free packages is by no means exhaustive. Hitherto, the predominent automatic winding machine in the spinning sector of the textile industry of Pakistan has been the Murata Mach Coner, followed by Savio Espero and Orion winders. However, the latest trends is in favour of import, installation and commissioning of the Schlafhorst Autoconer 338 as part of the BMR programmes of the spinning mills on account of its overall superior performance.

Acknowledgement

Useful technical information received from M/s. Ahsan Bari, Arsalan Zahid Piprani, Sheharyar Aslam Khan and Hasan Anas (3rd year students) during the preparation of this paper is gratefully acknowledged.