1Introduction

Slub yarns have penetrated into many domains of the textile industry. As a result, many discussions have started between test system manufacturers, machine manufacturers and slub yarn producers. The most important discussions deal with the quality characteristics of slub yarns which have to be measured to simplify the discussions among the above mentioned partners. In addition, the partners have the intention to improve the reproducibility of slub yarns and to standardize the spinning process. But also weavers, knitters, traders and retailers are interested in a reliable measurement of slub yarns in order to be able to evaluate the delivered yarn according to their individual requirements. Further processing of a slub yarn as well as the appearance of the yarn can be assessed.

Uster Technologies has developed a sophisticated software for the USTER TESTER 5 which permits the accurate measurement of slub yarns. This optional software is called USTER FANCY YARN PROFILE.

The goals of the USTER FANCY YARN PROFILE measurement follow mainly two directions:

Providing a tool for daily quality control in order to be able to compare the reproducibility of the slub yarn production to compare machine settings, etc.
Giving detailed analysis of the slub yarn in order to provide information for the spinner to create and develop a slub yarn.

Based on the results of the measurement, the most important questions about a slub yarn can be answered, like e.g.:
Which slubs are produced?
How many slubs per length unit are produced?
What is the slub distribution?

What is the individual size of the slubs, their distance and the mass increase?
What is the correlation between the settings of the slub yarn device and the resulting yarn?
Are there any disturbing mass decreases before or after a slub?
Is the sequence of the slubs correct and/or is there a repeating pattern?
Comparison of machines and batches?

2Definition of slub yarn types

In the textile industry there are various definitions for the different slub yarn types. In order to avoid any misunderstandings and mix-ups, the definitions of the different slub yarn types according to Uster Technologies AG are given in Table 1:

Simulation

In order to get a first impression of the produced slub yarn, it is possible to simulate the yarn in different weaving or knitting patterns or as a simple yarn board (Fig. 14). Thus, patterns can be revealed and settings of the slub yarn device can be evaluated in respect of the appearance of the yarn.

8Conclusion

The accurate measurement of slub yarns became more and more important in order to improve the reproducibility and to simplify the variety of slub yarns. Therefore, there were various requirements in the textile industry to improve the measurement technology of slub yarns. Uster Technologies has implemented sophisticated software into the newly developed USTER TESTER 5 to offer a better tool for slub yarn measurement.


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The measurement of the slub yarns with the USTER TESTER 5 is performed with the capacitive sensor CS. Therefore, the evaluation of slub yarns concentrates mainly on slub yarns with a variation of the mass.

3Definition of terms

The USTER FANCY YARN PROFILE uses certain terms to describe a slub yarn. These terms are described in the following chapter in order to create a clear picture of the ability of this measurement method.

Reference level

The reference level is a value, which is on the level of the base yarn. All slub yarn calculations are based on this reference level. This level is set automatically by the software, but can be modified if required, in the setting of the Fancy Yarn configuration. The reference value of this reference level is 0%.

Ideal slubs

The ideal slubs are marked in orange in the mass diagram. It shows how the software substitutes the real slub by an ideal slub to avoid calculation errors. Based on this orange trapezoid the slub length, slub distance, and mass increase are calculated. The ideal slubs are required to produce re-producible results.

Mass increase

The mass increase is the increase in percent between the base and the top of the orange trapezoid.

Slub length

The slub length is defined at half of the height of the slub. This definition is selected to level out various kinds of ramps for different slub yarn types.

Slub populations

Slub yarns can be designed to have two or more populations. This means that there are at least two different slub sizes regarding e.g. different mass increases or slub lengths or combinations of both in one slub yarn (see Fig. 1). These different populations can be evaluated separately. This means that the statistical values of the individual populations in the sample table are given separately.

Slub distance

The slub distance is measured between the end of a previous slub to the start of the subsequent slub. All slub distances plus all slub lengths together will add up to the overall test length. If two or more populations are defined, the slub distance is defined within the same population. If required, the mean slub distance between consecutive slubs can be evaluated.

Mass decrease

Mass decreases before and after a slub can lead to severe weak places in the yarn. They are often related to the settings of the slub yarn device used and / or the spinning machine. Therefore, this parameter is an important quality characteristic of a slub yarn as it can lead to severe problems in the further processing of the yarn. For this evaluation, only mass decreases within a distance of three centimeters and a mass decrease of -30% before or after a slub are evaluated. The starting points of this distance are at the ends and the beginning of the slubs.

Percentage slub length / slub distance / mass increase

This value is equivalent to the percentage of the slub lengths and slub distances compared to the overall length of the measured yarn or the mass increases of the slubs compared to the overall mass of the yarn.

Count of slub / base yarn

Usually, the nominal count of a slub yarn consists of a mean value of the overall mass per unit length. With the USTER FANCY YARN PROFILE, it is possible to separate the count of the slubs from the count of the base yarn, in order to describe the yarn more accurately.

Fancy Yarn Configuration

This is the overall definition, how a slub yarn should be evaluated regarding the reference level, the setting of a limit to separate slubs from random thick places (boundary) and the definition of populations. This configuration is done in the settings of the USTER TESTER 5 by the operator depending on the appearance of the slub yarn and the aim of the evaluation. In the Fancy Yarn Configuration dialog it is possible to adjust the reference line if required, to define boundaries, to mark populations, to save and to change configurations and apply them to a tested sample.

Outliers

These are slubs that are located above the defined boundary, but do not belong to any population, if populations are defined. If no populations are defined, no outliers can be analyzed.

4Measurement of slub yarns

Slub yarns can be measured reproducible on the USTER TESTER 5 with a speed up to 800 m/min in the Fancy Yarn mode. For the slub yarn evaluation the sensor CS is used. The optical sensors like the sensor OH for the hairiness measurement, the sensor OM for the optical evaluation of a yarn, the sensor OI for the evaluation of the trash and dust as well as the foreign matter sensor can be used at the same time for other evaluations of the yarn. As slubs can be distributed randomly a test length of 1000 m is recommended.

5Numeric evaluation of slub yarns

The USTER FANCY YARN PROFILE offers a wide range of numeric data for a detailed analysis of a slub yarn. These are:

Number of slubs per [1/ km or 1/m or absolute number]
Slub distance mean [cm]
Slub distance min [cm]
Slub distance max [cm]
Slub length mean [cm]
Slub length min [cm]
Slub length max [cm]
Mass increase mean [%]
Mass increase min [%]
Mass increase max [%]
Mass decrease right [1/ km or 1/m or absolute number]
Mass decrease left [1/ km or 1/m or absolute number]
Percentage slub distance [%]
Percentage slub length [%]
Percentage mass increase [%]
Count slub, equivalent to the selected count system
Count base, equivalent to the selected count system
Outliers [1/ km or 1/m or absolute number]

For comparison reasons, the results of the Fancy Yarn Profile are only given in the metric system. The measurement however, can be carried out in yards.

6Graphical evaluations of slub yarns

Besides the numeric evaluation of the slub yarn, the USTER FANCY YARN PROFILE offers a wide range of graphical possibilities to evaluate the yarn. Furthermore, the separation of the base yarn and the slubs is realized, which offers more possibilities to evaluate the yarn. This means, that it is additionally possible to separate many graphs into the base yarn as well as into the slubs. Also, the boundaries and populations set in the configuration are visible in the reports.

Mass diagram

The mass diagram is the basis for all calculations. In this diagram, the measurement of the yarn can be followed over the x-axis. The y-axis gives the mass increase of the yarn. The reference level is set to 0% (see Fig. 2). With the zoom function (see Fig. 3), the slubs can be analyzed in detail. When zooming in, the trapezoids of the ideal slubs get visible. On the x-axis, the detected mass decreases before and after the slubs are indicated as orange marks.

In order to analyze the base yarn without the slubs, it is possible to remove the slubs from the diagram by a double click on the word Original on top of the diagram. The diagram of the base yarn only appears (Fig. 4). This gives the opportunity to the user to evaluate the yarn without slubs. This can be of special interest, when additional mass variations are produced by the ring-spinning frame besides the regular slub yarn device. Irregularities, slow changes of the mean value or jumps in the diagram become visible that might not be related to the production of the slubs, but to faults created in the spinning process.

Scatter Plot

Each point in the plot represents a slub defined by the slub length (x-axis) and the mass increase (y-axis). The points below the boundary are gray. They belong to the regular mass variation and are not taken into consideration for any slub calculation. The colors indicate the sequence, when the slubs occurred: the blue dots were the first 20% of all slubs, turquoise dots were following, then green, then pink and then the last 20% of all dots are indicated in red. The scatter plot below (Fig. 5) also indicates, where the boundary (grey line) was defined, which separates the slubs from the mass increases of the yarn body. Also, two populations are marked, which will be evaluated separately in the sub-sample table.

With this kind of scatter plot, it is possible to see, if all slubs are distributed evenly or if any slub kind occurred earlier or later in the measurement. This can be of special interest, when a whole bobbin or cone is tested. A slub yarn without a fault in the slub yarn program should have the different colored dots on top of each other like shown in Fig. 5 below.

Sequence diagram

The purpose of the sequence diagram is to make patterns in the sequence of the slub easily visible. This diagram shows the exact sequence of the slubs separated in slub distance and slub length (Fig. 6). Depending on the requirements of the analysis the order of the slub length and slub distance in the graph can be altered. The x-axis shows the number of the slubs, whereas the y-axis shows the lengths of the slub (orange) and the distances (blue) between the slubs. Also, it is possible to zoom into the diagram. By placing the cursor above a line, the position of this slub within the measurement in meter is shown as a tool tip. This makes it easy for the user to find the respective slub in the mass diagram.

Histogram

With the help of the histograms, it is easy to evaluate a single parameter of a slub yarn separately. The distribution and the range of the parameters can be analyzed. Three kinds of histograms are available:

Histogram for slub length
Histogram for slub distance
Histogram for mass increase

3D-plot

In the 3D-plot, the user can analyze the distribution and the frequency of the slubs, i.e. in which area most of the slubs occur. Thus, it combines the information from the scatter plot with the information from the histogram. The 3D-plot can also be very helpful if the slubs are small and embedded in the normal mass variations of a yarn.

Classification Matrix

The classification of the slubs in a matrix is a tool to quickly analyze the distribution of the slubs. The USTER FANCY YARN PROFILE provides a standard classification matrix with fixed classes for the slub length and the mass increase (Fig. 9). As there are numerous kinds of slub yarns, it is also possible to create own classification matrices based on the individual requirements of the different slub yarns. The number of slubs in the different classes can be counted as slubs / m, slubs / km as well as absolute values for the whole test length.

Spectrogram

The spectrogram is an ideal tool to check various aspects of a slub yarn:

Is there a repeat pattern of the slubs?
Are there any periodic faults in the yarn?
Are there any nearly-periodic (drafting) faults in the yarn?

With the possibility to separate the base yarn from the slubs, the base yarn can be evaluated separately. Deliberate disturbances on the spinning machine or unexpected faults can be detected separately from the slubs. Thus, the USTER FANCY YARN PROFILE offers three kinds of spectrograms to the user (Fig. 10):

Slubs only: only slubs are assigned to the respective frequencies
Slubs removed: only the spectrogram of the base yarn is shown
Spectrogram mass: spectrogram of the measured yarn including the base yarn and the slubs

The spectrogram mass combines the spectrogram with slubs only and the spectrogram with slubs removed. The repeat pattern of the slub length and the slub distances can be found in the range of 13 to 60 cm.

7Application

In the following a few examples for the applications of the slub yarn measurement on the USTER TESTER 5 are described.

Comparison with machine settings

It must be pointed out that the measured slubs do not necessarily coincide with the settings at the slub yarn mechanism of the spinning machine. The resulting slub yarn does not only depend on the settings at the spinning machine, but is also influenced by the raw material, the staple length, the twist, the yarn guiding elements, etc. This indicates that an absolute comparison between the settings at the fancy yarn control box and the real results is not recommended. It is rather a trial and error method when the fancy yarn is produced for the first time. Correlations between the results of the USTER TESTER 5 and the machine settings must be found individually.

Performance on weaving machine

In a weaving mill, a slub yarn was used for the weft. The performance of the loom however was poor due to many weft breaks. On another loom the same slub yarn was used, but without any performance problems. Thus, both yarns were tested on the USTER TESTER 5. The measurement revealed that the poor performing weft yarn showed a considerably higher amount of mass decreases before and after a slub in the mass diagram (Fig. 11). The result can also be traced in the numeric data of the sub-sample table.

Additional mass variations on the ring spinning machine

In order to produce very irregular slub yarns, it is possible to add additional mass variations on the ring spinning machine besides the regular slub yarn device. As the USTER FANCY YARN PROFILE is able to separate the base yarn and the slubs it is possible to analyze these deliberate disturbances accurately. These mass variations become visible especially in the mass spectrogram that can be divided into the slubs and the base yarn. Fig. 12 shows the spectrogram of a base yarn of a yarn produced without any additional variations. Fig. 13 in comparison shows the spectrogram of a base yarn of a yarn with additional mass variations on the spinning frame. The analysis of the two spectrogram shows that the additional disturbances become visible as drafting waves between 40 and 90 cm.