Clearing of slub yarns 12

Main Contents

12. Clearing of special yarns .................................................................... 12.1

12.1 Introduction to fancy yarns ...................................................................................................... 12.1

12.2 Clearing of fancy yarns ............................................................................................................. 12.1
12.3 Clearing of slub yarns ............................................................................................................... 12.3
12.4 Clearing of yarns with nep or loop effects .............................................................................. 12.5
12.5 Melange yarns ............................................................................................................................ 12.6
12.6 Core yarn .................................................................................................................................... 12.7

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12. Clearing of special yarns

12.1 Introduction to fancy yarns

Fancy yarns are used in the textile industry for various applications. Therefore, fancy yarn manufac-
turing is not a niche market anymore. Up until now, it was not possible to determine the quality char-
acteristics of fancy yarns in detail which are needed for a quality management. This can be done in
the laboratory with the USTER® TESTER 5.

An accurate determination of slub yarn characteristics is also required for negotiations and specifica-
tions between fancy yarn spinners and weavers, knitters, traders and retailers.

12.2 Clearing of fancy yarns

Slubs, neps, thick and thin places are noted as yarn faults and are considered as degrading features
of yarn quality. During various processes, efforts are taken to minimize their occurrence. However, in
fancy yarn production these features are introduced in the yarn in order to give visually attractive dif-
ferences to the other fabrics [1].

Fancy Yarn is a yarn that differs from the normal construction of single and ply yarns by way of delib-
erately produced irregularities from the normal construction. These irregularities relate to an increased
input of one or more of its components, or to the inclusion of random effects, such as knops, loops,
curls, slubs, or the like. [6]

There are various names which are used to describe the different yarn effects. Table 12-1 shows
eight basic profiles of fancy yarns. These yarn effects can be made by plying a number of yarns to-
gether or, with modified spinning techniques, most can be spun from sliver or roving [1].

Basic yarn profile Designations

Spiral Mock spiral, mouline, jaspe

Gimp Frise, caterpillar, onde

Slub Ground slub, injected slub, injected flame (also called tear- off flame)

Knop Knot, nep, noppe, button, reverse caterpillar, flake

Loop Boucle, frotte, pong, mock-spun chenille

Cover Twisted flame

Chenille Woven chenille, plied chenille

Snarl

Table 12-1 Various fancy yarns [1]

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Fig. 12-1 Examples of effect twist fancy yarns [1]

There are also several classifications for fancy yarns. Table 12-1 gives one of these classifications
according to the employed production methods. Here mainly two production methods are employed:
Produced effects are based on twisting or doubling of yarns together to create the fancy yarn effect
from already spun yarns. Spun-effect yarns are fancy yarns spun directly from fibers fed to the spin-
ning system [1].

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Yarn (produced) effects Spun yarn effects

Controlled discontinu- Controlled

Regular effects Regular effects
ous effect discontinuous effect

Spiral Reverse caterpillar Spiral Button

Mouline Neps Mouline Slub

Loop Knots Loop Caterpillar

Boucle Knop Boucle Combinations

Gimp Slub Gimp

Onde Onde
Snarl Chenille

Cover

Chenille

Table 12-2 Classification of fancy yarns [1]

If fancy yarns have to be cleared on winding machines, the following recommendations have to be
taken into consideration:

All the fancy yarns have a regular pattern (pseudo-random formation). If faults occur, the regular pat-
tern is disturbed and can be recognized in the scatter plot (YARN BODYTM). Such faults can be elimi-
nated accordingly.

In this chapter we will concentrate mainly on slub yarns.

12.3 Clearing of slub yarns

A slub yarn is a yarn in which slubs may be created to produce a desired effect. Generally, slub yarns
are divided into two classes: (i) spun slubs, and (ii) plucked (or inserted) slubs. Spun slubs may be
produced by an intermittent acceleration of one pair of rollers during spinning or by the blending of
fibers of different dimensions. Plucked slub yarns are composed of two foundation threads and short
lengths of straight-fiber materials that have been plucked from a twistless roving by roller action [6].

As the range of applications is very wide for slub yarns, there are also different types of slub yarns.
They are usually called slub yarns, multicount yarns and multitwist yarns.

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Table 12-3 below explains the differences between these three yarn types.

Term Twist αe Mass Slub length

Any length up to
Slub yarn constant variable variable
2 meters
Any length over
Multicount variable constant variable
2 meters
Multitwist variable variable constant any

Table 12-3 Definition of different slub yarn types

It is also possible to distinguish between structured slub yarns and slub yarns with distinctive slubs.
Structured yarns can be characterized as very uneven yarns without any clear slubs. Fig. 12-2 shows
an example of a distinctive slub yarn on a blackboard.

Fig. 12-2 Slub yarn with short slubs on a blackboard

Setting of a clearing limits for slub yarns

With the USTER® QUANTUM 3, there is a special setting for slub yarns. For this, we can use the ra-
dio buttons to switch from NSL thick places to Slub Yarn settings window. The aim of this feature is to
define the clearing limit to prevent the clearing of desired thick places in slub yarn. The events in the
defined slub area should not be cut because this is a characteristic of the yarn. In order to clear slubs,
instead of standard setting points P, we have the special setting points K1 to K3 to zone out areas
where slubs should not be cut. For example: Set point K1 = 700% / from 10.0 cm to 25.0 cm. This
means the slubs between 10.0 and 25.0 cm are not cut.

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It is possible to assign up to 3 K areas where slubs should not be cut Fig. 12-3.

Fig. 12-3 Slub yarn setting. No clearer cuts up to +700% from 10 to 25 cm.

Characteristic yarn faults in slub yarns

The clearing of slub yarns should achieve the following: Specifically generated "thick places" should
remain in the yarn, disturbing yarn faults have to be cleared.

Slub yarns consist of at least 2 single yarns, i.e. if one of them is missing, the yarn clearer has to de-
tect this. The existence of each single yarn has to be monitored.

Faults in the single yarns have to be eliminated, in order to avoid any unevenness in woven or knitted
fabric.

12.4 Clearing of yarns with nep or loop effects

Fundamentally, it can be said:

• The desired effect has to be monitored. If the effect is missing, a cut has to follow.
• Each single yarn of the ply yarn has to be monitored.
• Possible yarn faults in the single yarn must be monitored.

Fig. 12-4 Yarn fault in a bouclé yarn

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In summary, it can be said, that all irregularities of the visual impression of the end product have to be
monitored.

12.5 Melange yarns

Melange yarns are produced by blending a certain percentage of fibers of different colors. Blending
can be done in a very early stage of the process. This means, for example, mixing of multi-colored
fibers in the opening line, feeding of slivers of different colors at the drawframe or directly at the spin-
ning machine.

Characteristic yarn faults in melange yarns

For melange yarns it is of particular importance that the blending effect, i.e. the blend of multicolored
fibers is as regular as possible. If too many fibers of one component are missing, it is possible that
stripes of a particular color occur in the end product.

Fig. 12-5 Melange yarn / Blending problems / Fig. 12-6 Melange yarn / Blending problems
Blend of black and white fibers 100% cot-
ton, Ne 30 (20 tex), OE rotor

Choice of the measuring head

It is not possible to monitor uneven color effects with a capacitive measuring head. The increase or
decrease of one fiber component is less than the normal mass unevenness of a yarn.

With the USTER® QUANTUM 3 iMH-O30, it is possible to monitor the proportion of blending.

For the clearing of long color deviations, it is necessary to set the CC-channel accordingly. The de-
fined length must correlate with the expected fault length. If necessary, the set length must be short-
ened and the diameter must be increased in 2%-steps.

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12.6 Core yarn

Core yarns are usually made of a filament core and a cover yarn made out of staple fibers. The main
problem with core yarns (with respect to yarn clearing) is the detection of the missing core. When a
core is missing, it causes a marginal change in diameter however it causes a higher change in mass.
The capacitive clearer has, therefore, an advantage for this application. The change in mass is pro-
portional to the fineness of the core.

The USTER® QUANTUM 3 has a new capacitive sensor technology which has an even better signal
ratio and therefore a higher possibility to detect the missing core. The detection is mainly possible
when the change in mass due to the missing core is higher than 13%.

Clearing of core yarns (CY)

For the production of corespun yarn the UQ 3 provides a special yarn type setting named Core yarn

Fig. 12-7 Yarn type Core yarn

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Core yarn monitoring; detects the break of the core while yarn is running. A cut takes place if mass
change suddenly drops over a certain length. The setting parameters are:

Tolerated decrease in %.
This setting is only active when the yarn type is core yarn.
Sensitivity: 0% = Clearing channel inactive

Fig. 12-8 Core yarn setting (CY)

A missing core can only be detected if the mass of the core is higher compared to the normal mass
variation of the yarn.

Clearing of a yarn with missing cover

Besides normal thick places, a missing cover is also disturbing. Therefore, a partly or completely
missing cover must be monitored. For these events the normal clearing limits NSL T as well as the
CC channel over longer reference length will help to detect yarn with missing cover.

In case of sewing threads, a classification of short neps is required. Neps are considered as disturb-
ing events if they are occurring in high numbers. The frequency of such neps is an indicator for the
running behavior of the yarn on the sewing machine.

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