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| Issue date:01/06/2007 |
| ATA Journal for Asia on Textile & Apparel - Jun 2007 Issue |
| Source:Journal for Asia on Textile & Apparel |
| by Sandra Edalat-Pour |
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Slub yarns have penetrated into many domains of the textile industry. As a result, test system developers, machine manufacturers and slub yarn producers have been working to deal with the quality characteristics of slub yarns and how to measure them effectively. Uster Technologies has recently developed an innovative software for the Uster Tester 5, called Uster Fancy Yarn Profile which permits the accurate measurement of slub yarns.
Various parties would like to improve the reproducibility of slub yarns and to standardize the spinning process. As well, weavers, knitters, traders and retailers need a reliable measurement of slub yarns to be able to evaluate the delivered yarn according to their individual requirements.
The new software by Uster provides a tool for daily quality control to compare the reproducibility of the slub yarn production. It also gives detailed analysis of the slub yarn so as to provide information for the spinner to create and develop a slub yarn.
With the results of the measurement, users are able to draw crucial information as follows:
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?
Definition
The Uster Fancy Yarn Profile adopts a set of specific terms for the ease of communication.
Reference level: value on the level of the base yarn
Ideal slubs: orange marks in the diagram represent how the slubs are detected by the software
Mass increase: mass increase in percentage between the base and the top of the orange trapezoid
Slub length: defined at half of the height of the slub
Slub populations: separated evaluation of slub groups with regard to different mass increase, slub length or combinations of both
Slub distance: length between the end of a previous slub and the start of the subsequent slub
Mass increase: mass decreases within a distance of 3cm and a mass decrease of -30% before or after a slub are evaluated
Percentage slub length / slub distance / mass increase: 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: separation of the count of the slubs and the count of the base yarn
Ratio T/B: ratio of the length at the top of the slub mark to the length at the bottom of the mark
Length bottom: length of a slub at the bottom of the slub mark
Fancy Yarn Configuration: This is the overall definition. It refers to 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
Outliers: slubs that are located above the defined boundary, but do not belong to any population, if populations are defined
Measurement 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.
Numeric 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:
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.
Graphical evaluations of slub yarns
The Uster Fancy Yarn Profile offers a wide range of graphical data to evaluate the yarn by separating the base yarn and the slubs, which means now it is possible to have separated graphs with the base yarn and the slubs respectively. The boundaries and populations set in the configuration are also visible in the reports.
Mass diagram
Figure 1 |
The mass diagram serves as the basis for all calculations. The measurement of the yarn is shown over the x-axis of Figure 1. The y-axis gives the mass increase of the yarn. With the zoom function, the slubs are analyzed in detail. When zooming in, the trapezoids of the ideal slubs become visible. Along the x-axis, the detected mass decreases before and after the slubs are indicated as orange marks.
Figure 2 |
In Figure 2, the slubs are removed to show the base yarn only. This gives the opportunity for a user to evaluate the yarn without slubs. This is of particular interest when additional mass variations are produced by a ring-spinning frame, for instance. When irregularities, slow changes of the mean value or jumps are shown in the diagram, it is easier for the user to detect the reasons behind or faults from the spinning process.
Scatter plot
Figure 3 |
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 displayed in gray. They belong to the regular mass variation and are not taken into account for any slub calculation. The colors indicate the sequence.
When the slubs occur: the blue dots are the first 20% of all slubs, followed by turquoise, green and then pink dots. The last 20% of all dots are indicated in red. The scatter plot shown in Figure 3 exhibits two populations, which are evaluated separately in the sub-sample table.
Sequence diagram
Figure 4 |
The sequence diagram is made to make the sequence patterns of the slub easily visible. Figure 4 shows the exact sequence of the slubs separated in terms of slub distance and slub length. 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.
As well, it is possible to zoom into the diagram. By placing the cursor above a graphline in the graph, the position of this slub in regard of the measurement in meter is shown in a tool tip. This facilitates the user to locate a particular slub in the mass diagram.
Histogram
Figure 5 |
With the help of the histogram (Figure 5), the user is able to single out a particular parameter of a slub yarn to make a separate evaluation. The distribution and the range of the parameters can be analyzed. Histograms are available for the slub length, the slub distance as well as the mass increase.
3D-plot
With 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 and the slub size (slub length and mass increase). In effect, it combines the information of the scatter plot with that of the histogram. The 3D-plot is 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 serves as a tool to quickly analyze the distribution of the slubs. The Uster Fancy Yarn Profile provides a standard classification matrix that gives fixed classes in regard to the slub length and the mass increase. As there are numerous kinds of slub yarns, the user can create his own classification matrices based on individual requirements of different slub yarns. The number of slubs in different classes can be calculated as slubs per meter or slubs per kilometer, as well as in absolute values for the whole test length.
Spectrogram
The spectrogram is suitable to check various aspects of a slub yarn, such as potential repeated patterns, periodic or nearly faults occurred 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 by the Uster Fancy Yarn Profile, which offers three kinds of spectrograms to the user (Figure 6):
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 third spectrogram 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 13cm to 60cm.
Applications
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
Notably, 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 other factors including the raw material, the staple length, the twist and the yarn guiding elements. 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 adjusted individually.
Performance on weaving machine
In a weaving mill, a slub yarn is used for the weft. Suppose there are two looms. One has many weft breaks, while the other has no performance problems. When the yarns produced by the two looms are tested by the Uster Tester 5, the measurement will reveal that the poor-performing weft yarn has a considerably higher amount of mass decreases before and after a slub in the mass diagram. The result can also be traced in the numeric data of the sub-sample table.
Additional mass variations on the ring spinning machine
Figure 7
Figure 8 |
As mentioned earlier, additional mass variations on the ring spinning machine are sometimes adopted with the regular slub yarn device so as to produce highly irregular slub yarns. In this case, the Uster Fancy Yarn Profile is used to separate the base yarn and the slubs and provides an accurate analysis of these deliberate disturbances. The mass variation data can be shown in a mass spectrogram. Figure 7 shows the spectrogram of a base yarn of a yarn produced without any additional variations, whereas Figure 8 displays the spectrogram of a base yarn of a yarn with additional mass variations on the spinning frame. By comparing the two spectrograms, the additional disturbances are visible in the area of drafting waves between 40cm and 90cm.
Simulation
In order to "preview" the produced slub yarn, it is possible to simulate the yarn in different weaving or knitting patterns or as a simple yarn board. Patterns are thus previewed and adjusted to provide the best possible appearance of the yarn.
Source: Uster Technologies AG
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| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
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| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
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