As we all know, the DR curve and DR value have a good correlation with the appearance quality of the cloth surface, and the comprehensive analysis of the DR value series index with other quality index charts of yarn (such as unevenness curve, spectrogram, yarn defect classification chart, linear density histogram, etc.) can be used to evaluate the influence of yarn quality index on the appearance quality of the cloth surface more comprehensively, which has strong practical significance in yarn quality control.
1. Analysis of the characteristics of the two DR curve characterization methods
At present, there are two main ways to characterize DR curves:
(1) In the bilinear coordinate curve diagram represented by the Changling strip stem instrument, the abscissa and ordinate are linear coordinates, and the ordinate scale and abscissa scale are equal (see Fig. 1).
Fig.1 Coordinates of the DR curve of the Changling strip dryer
(2) The linear-logarithmic coordinate curve represented by the Premei strip dryer graph, on the DR curve graph, the abscissa adopts linear coordinates, and the ordinate adopts logarithmic coordinates, the scale of the abscissa is equal, and the scale of the ordinate adopts the logarithmic series (see Fig. 2).
Fig.2. Coordinates of the DR curve of the Premei strip dryer
Due to the different coordinate setting methods of the two DR curves, there are obvious differences in the morphology of the DR curves.
In addition, the length thresholds of the two DR curves were also different, and five length thresholds of 1cm, 10cm, 20cm, 50cm and 1m were selected for the Changling strip stem instrument. The Preh Strip Dryer selects four length thresholds of 1cm, 10cm, 1.5m and 10m.
Although the two DR curves choose different coordinate representation forms, the two graphs can be converted to each other through calculation.
2. The principle and special morphological analysis of the two types of DR bending
2.1 Principle of DR curvature morphology
In order to explore the principle of the formation of the two DR curve shapes and analyze the yarn quality problems reflected by some special DR curve patterns, we used the function of inserting automatic charts into the excel table to display the simulated line charts of DR values under the same set of different threshold values (see Table 1) by using bilinear coordinates and linear-logarithmic coordinates respectively to compare the differences between the two.
Table 1 Simulated data of DR values at different thresholds
Fig.3. Simulation curve of DR value of bilinear coordinates
Fig.4. Simulation curve of DR value for linear-logarithmic coordinates
From the comparison of the data in Table 1 and the curve morphology in Figure 1 and Figure 2, it can be seen that in the case of the same set of data, the shape of the DR value simulation curve is completely different when different coordinate systems are used.
2.2 Analysis of the morphological differences between the two DR curves and their causes
In the case of a given length threshold (L), with the change of the absolute value of the amplitude threshold (x) from small to large, the DR% (L,+x) and DR% (L,-x) decrease sharply in numerical value, so the morphological differences between the two DR curves appear in the following aspects:
(1) For the DR curve of bilinear coordinates, a curve with a "concave" shape will be formed; For the DR curve plot with linear-logarithmic coordinates, a curve with an "convex" pattern is formed.
(2) With the change of the absolute value of the amplitude threshold (x) from small to large, the change of DR value is reflected in the DR curve graph, which is the change of graph shape, and the larger the change of DR value, the straighter the curve shape; The smaller the change in the values, the more obvious the radians of the "concave" and "convex" (see the comparison of the curves of DR value (L1, ±x) and DR value (L2, ±x) in Fig. 1 and Fig. 2).
(3) Due to the different coordinate systems, the difference in DR value with small absolute value of amplitude threshold (x) is more obvious on the DR curve of bilinear coordinates, while the difference of DR value with large absolute value of amplitude threshold (x) is more obvious on the DR curve of linear-logarithmic coordinates (i.e., on the DR curve of bilinear coordinates, the difference in the proportion of coarse details with smaller thickness and longer length is more obvious from the graph; However, on the DR curve of linear-logarithmic coordinates, the difference in the proportion of coarse details with larger thickness and shorter length is more obvious from the graph. That is, the DR curve of linear-logarithmic coordinates is more conducive to reflecting the change of defect thickness, while the DR curve of linear-logarithmic coordinates is more conducive to reflecting the change of defect length).
(4) On the DR curve of linear-logarithmic coordinates, the minimum value of the ordinate is 0.1 because the ordinate adopts a logarithmic scale, while on the DR curve of bilinear coordinates, the minimum value of the ordinate is 0.
(5) On the DR curve of linear-logarithmic coordinates, the DR curves with large length thresholds such as 1.5m and 10m are displayed, which is conducive to detecting and controlling the influence of each process of pre-spinning on the DR value.
(6) On the DR curve diagram of linear-logarithmic coordinates, because the minimum value of the ordinate is 0.1, and the two length thresholds of 1.5m and 10m selected by the Premei strip dryer are larger, the length of the spinning yarn is calculated according to the general measurement of the strip dryer is 200m or 400m, and the total length of the coarse knots or details represented by the minimum ordinate value of 0.1 is 0.2m or 0.4m respectively, so under the two measurement lengths of 200m or 400m, according to the calculation principle of the DR value, 1.5m, The 10m DR curve can never reach the minimum value of 0.1 of the ordinate, so on the DR curve, the DR curves of 1.5m and 10m are always in a suspended state.
(7) The use of linear-logarithmic coordinates of the DR curve is more conducive to the analysis and solution of the quality problems caused by the spinning process, and the use of the linear-logarithmic coordinates of the DR curve is more conducive to the analysis and solution of the quality problems caused by the pre-spinning.
2.3 Morphological requirements for normal DR curves
From the relationship between the DR value and the appearance quality of the cloth, it can be seen that in order to make the appearance of the cloth surface smooth and clean, and the texture is clear, it is necessary to ensure that the fluctuation of the yarn is in a normal distribution form, and the number of coarse details on the yarn is small, and the thickness and length are basically equal. Manifested in the DR curve, the graphic form must have the following characteristics:
(1) The DR curves with different length thresholds are basically symmetrical on both sides of the 0 axis of the abscissa.
(2) The DR curves with different length thresholds converge at the coordinate point (0,50%).
(3) The lower end of the DR curve with different length thresholds is narrow, and the area surrounded by the curve is small (i.e., the shape of the curve is narrower and thinner).
(4) The DR curves with different length thresholds are smooth, and there are no horizontal segments, bumps, steering points, etc.
(5) There is no crossover and convergence in the middle of the DR curve with different length thresholds.
(6) For the DR curve diagram of linear-logarithmic coordinates, the position of the overhang point of the DR curve of 1.5m and 10m should be low, the distance between the overhang point and the 0 axis of the abscissa is small, and the overhang point is basically symmetrical.
(To be continued)
Source: Wang Xueyuan, Hangzhou Jingsha Information Technology Co., Ltd., Wang Zanlin, Laohekou Runfa Cotton Textile Enterprise Co., Ltd
Editor: China Yarn Network New Media Team
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