Irregularity Of Sliver Research Articles

A study on the dynamic motion of floating fibers in the double apron drafting process

Double apron drafting is an important unit in yarn spinning; the motion of fibers during the double apron drafting zone directly determines the quality of the final yarn. In this research, we sought to study how the motion of the fibers and the irregularities introduced during the double apron drafting process were affected by the processing settings and fiber properties. The fiber acceleration point under different drafting conditions was investigated using the tracer fiber technique. The results showed that both the drafting parameters as well as the input sliver properties have a certain influence on the fluctuation of fiber acceleration points, but the difference is small. In addition, the irregularity caused by the fluctuation of the fiber acceleration point during the drafting process (CVFAP) was also calculated under the same drafting conditions based on the irregularity of the input sliver and that of the spun yarn. By comparing the relationship between the CVFAP and fiber acceleration point fluctuation, it was found that the trend of the change between the two is in fairly good agreement. This is consistent with theoretical research and practical experience, and it can prove the accuracy of the fiber acceleration point test results from another aspect as well. Studying the dynamic motion of floating fibers during the double apron drafting process sheds light on the correlation between spinning conditions and yarn quality, which can provide a reference for process optimization.

Drafting force measurement: A New method to Optimize Drafting Process

This study is focused on the optimization of drafting process through measuring drafting force and short term irregularities of fiber strand. Drafting force is the instinctive factor initiated by the frictional forces between slow moving and fast moving fibers during attenuation. Drafting force can be a good source of information regarding dynamic fiber behavior and reflects combined effect of multiple fiber and process parameters, for a particular materiel. The interaction between break draft and drafting force and how these in turn affect the irregularity of sliver has been analyzed by utilizing data from online drafting force device. The results showed that dynamic drafting force increases with the increase in break draft around 1.4 and then decreases with further increase in break draft. Short term sliver irregularity decreases up to 1.4 break draft and then increases as break draft increases. Furthermore, the region where drafting force reaches its maximum corresponds to the minimum sliver unevenness. Optimum break draft setting can be achieved at a point where the drafting force reached its maximum along with minimum short term sliver irregularity.

Study of drafting force variability and sliver irregularity at the break draft zone of a draw frame

To produce an evener fiber assembly, it is important to understand fiber dynamic behavior during the drafting process. Drafting force and its variability is an alternative approach to understand the fiber’s velocity–friction characteristics, representing a combined effect of multiple fiber properties. In this study, online drafting force and its variability was measured with different break draft ratios and back roller gauges to analyze its effect on sliver short-term evenness. Drafting force variability well correlated with sliver evenness with correlation coefficient R2 = 0.81. The coefficient of variation (CV%) of drafting force was highest (2.3%) at low break draft 1.1–1.2, and then reduced gradually to its minimum value (1.5%) around a break draft of 1.6–1.7. The minimum variability of drafting force well corresponds with lower irregularity of sliver at certain break draft ratios. This indicates that a stable drafting force promises better fiber distribution along the sliver length. The variability of drafting force and sliver irregularity also increased as the back gauge increased from 43 to 51 mm. Furthermore, the impact of short fiber content on the drafting force was investigated at three back gauges. The increase in short fiber content gives higher magnitude of drafting force. Drafting force was also compared with the number of neps and change in fiber length in sliver for each break draft. Better nep opening and improved fiber lengths were also found around (1.6–1.7) break draft and follow the same trend of variability of drafting force as the break draft changed.

Evaluating the Performance of a Thickness Tester to Measure Sliver/Roving Irregularity

This paper reports on the working principles of an instrument designed and built to measure the irregularity of sliver or roving. To verify the results of this instrument, the same roving is tested by the Uster II and Uster IV, and their results are compared with the new instrument. This paper also reports the effects of parameters such as the weight used to compress the sliver/roving passing between the groove-tongue disks of the instrument and the measuring speed and measuring length of the sliver or roving in the tests. The results indicate that these parameters do not considerably affect the results.

ギル機におけるニップゲージがスライバむらに及ぼす影響

In this research, we discussed the effect of nip gauge on the irregularity of the sliver. Initial experiments were done on an intersecting gill. Various nip gauges were adjusted on the gill-box and the irregularity of the produced slivers were measured. Generally, in the most of the current reports, it was thought that the irregularity of the sliver increases as the nip gauge increases. The results of our experiments on the gill box do not show a significant change in irregularity of wool sliver when the nip gauge was changed. To investigate more detail about this result, we prepared an experimental apparatus with higher variable nip gauge than that of the gill-box. The withdrawing test was done for various distance between the first faller and withdrawer jaws. As a result, we found that the effect of nip gauge on the irregularity of the sliver depends on the fiber length distribution. In case of wool sliver, because of the fiber length distribution, the effect of nip gauge on the sliver irregularity is not significant in a conventional gill-box with its limited nip gauge range.

Computer Modeling of the Product Spun from Chemical and Wool Fibres

The effect of the average length of Lavsan fibres in blending with wool lots with a low average fibre length on the average length and quadratic irregularity of fibres over the length in blended slivers is investigated. Recommendations are made for reducing the irregularity of the blended sliver and improving the conditions in successive transfers—in the combing, roving, and spinning segments of manufacture of worsted yarn.

Minimum Variance Control in Leveling Slivers

This paper presents procedures to design a minimum variance control for leveling slivers in a double-zone drafting process. We model a random sliver and consider the drafting model as a stochastic system with a zero-mean white noise process and a constant sequence representing the input-sliver mean thickness. Such a model enables the proposed control algorithm not only to smooth out the irregularity of the output sliver, but also to regulate the mean thickness at the desired value. We develop the minimum variance control applicable to our stochastic model based on an optimal predictor. Since some parameters and the noise process are not exactly known, identification is used to refine the model, and the control law is thus designed based on the identified model. The simulation results demonstrate that the algorithm can achieve goals by adjusting the speed of either the back or front roller.

画像処理によるギルスライバの混合むらの解析 第２報 面積間変動曲線の適用

Although the mean and standard deviation of blend ratio are a good approximation in blend sliver, the size of fiber aggregation may be different as well. In our research, block and stripe models were set up and these models were photographed by a CCD camera. Their adequacy for variance-area curve were investigated using a general-purpose image processing analyzer. Blend irregularity of sliver consisted of black and white fibers made of various kinds of processing conditions were analyzed by variance-area curve and then the change of size of fiber aggregation were studied.The number of pixels at 1/3 of total variance was almost similar to area of both models. It is desirable that both models are estimated by variance-area curves. In sliver blending, as the number of gilling stages is increased, the size of fiber aggregation in sliver decreases. Also, the blending of long-fiber-sliver is better than that of short-fiber-sliver. In case of reverse direction feeding, the size of fiber aggregation in sliver is smaller than that of forward direction feeding. In addition of these, the smaller size of fiber aggregation will be achieved at the stock blending process compared with sliver blending process.

Changes of Sliver Irregularity in Two-Zone Roller Drafting

A theoretical calculation is made to simulate the effect of drafting upon the sliver irregularity in two-zone drafting of three-over-three roller system. Two types of slivers, i.e., random sliver and optional sliver are considered. The effects of sliver count, staple fiber length, fineness of fiber, draft distribution between two drafting zones, maximal moving distance and distribution type of speed changing point are calculated on a computer. Furthermore, we have a try for clarifying the relation between irregularity of the supplied sliver and irregularity due to the movement of speed changing point upon irregularity of sliver after drafting.The results are as follows:(1) When the maximal moving distance of speed changing point is 0, the number of fiber ends in every increment remains unchanged, but the sliver thickness is reduced by the drafting action. Therefore, the coefficient of variation in the drafted sliver increases by the square root of the draft ratio.(2) When the maximal moving distance of speed changing point is not 0, sliver irregularity vary with the increase in this distance. The increase ratio of sliver irregularity decreases with the increase of British count of sliver, fineness of fiber and staple fiber length. And the staple fiber length has the strongest influence on it. Furthermore, the coefficient of variation varies with the draft distribution and the moving condition of speed changing point on two drafting zones. It can be seen that there is an optimal draft distribution which makes the coefficient of variation minimum, and that the range of the first drafting ratio is about 1.5-3. When the distribution type of moving distance is the same one in each drafting zone, the difference between the maximal and the minimal value of coefficient of variation is the smallest one.(3) It is also found that the correlation between the irregularity of the supplied sliver and the irregularity due to the movement of speed changing point is almost always a negative value on each drafting. On the first drafting and the second drafting in which the moving distance of speed changing point is 0, those correlations are regarded as independent of each other because of the small value (Max. -0.2). However, on the second drafting in which the moving distance of speed changing point is not 0, the correlation is not regarded as independent because of the large value (Max. -0.7).

Changes of Sliver Irregularity in Two-Zone Roller Drafting

A theoretical calculation is made to simulate the effect of drafting upon the sliver irregularity in two-zone drafting of three-over-three roller system. Two types of slivers, i.e., random sliver and optional sliver are considered. The effects of sliver count, staple fiber length, fineness of fiber, draft distribution between two drafting zones, maximal moving distance and distribution type of speed changing point are calculated on a computer. Furthermore, we have a try for clarifying the relation between irregularity of the supplied sliver and irregularity due to the movement of speed changing point upon irregularity of sliver after drafting.The results are as follows:(1) When the maximal moving distance of speed changing point is 0, the number of fiber ends in every increment remains unchanged, but the sliver thickness is reduced by the drafting action. Therefore, the coefficient of variation in the drafted sliver increases by the square root of the draft ratio.(2) When the maximal moving distance of speed changing point is not 0, sliver irregularity vary with the increase in this distance. The increase ratio of sliver irregularity decreases with the increase of British count of sliver, fineness of fiber and staple fiber length. And the staple fiber length has the strongest influence on it. Furthermore, the coefficient of variation varies with the draft distribution and the moving condition of speed changing point on two drafting zones. It can be seen that there is an optimal draft distribution which makes the coefficient of variation minimum, and that the range of the first drafting ratio is about 1.5-3. When the distribution type of moving distance is the same one in each drafting zone, the difference between the maximal and the minimal value of coefficient of variation is the smallest one.(3) It is also found that the correlation between the irregularity of the supplied sliver and the irregularity due to the movement of speed changing point is almost always a negative value on each drafting. On the first drafting and the second drafting in which the moving distance of speed changing point is 0, those correlations are regarded as independent of each other because of the small value (Max. -0.2). However, on the second drafting in which the moving distance of speed changing point is not 0, the correlation is not regarded as independent because of the large value (Max. -0.7).

Effect of Mechanical Processing Variables in Drawing on Sliver Irregularity

The present work examines the influence of draft distribution at the drawframe upon sliver irregularity under varying conditions of drawframe processing. The investigations were made at the first and second passage of drawing in carded mixings and at post-combed drawings in combed mixings, on slow-speed drawframes with Shirley draft distribution and high-speed Whitin drawframes. Eccentricity of top roller is shown to be one of the causes of slippage and sliver irregularity in slow-speed drawframes. Increasing the top roller loading is helpful in overcoming to some extent the deterioration in irregularity caused by an eccentric top roller. Roller slip at the front position caused by eccentricity in the roller has the most detrimental effects on sliver irregularity. Use of lower break draft under these conditions increases the sliver irregularity considerably. Eccentricity in the top roller in the second and third position causes more slippage, but the effect on irregularity of sliver is only marginal. Reduction of break draft increases slippage of front, second, and third top rollers even when they are true, but it does not affect sliver irregularity. The optimum roller setting at the front zone in conventional and high-speed drawframes depends upon the break draft and lies at a higher level at lower break draft. Thus, at close front zone setting, higher break draft gives a more regular sliver, while at wide setting, lower-break draft gives better results. The sliver irregularity at the optimum setting is, however, not much affected by the break draft.

CONTROL OF DRAFTING BY AIR FALSE TWISTER (II)

In the preceding paper (I), the ability of air twister tube as a substitute for usual twister tube of woollen ring spinning frame was studied.The effects of draft ratio, air pressure and tube dimension on false turns were experimented.The same testing apparatus as in the preceding paper was used in this experiment. The relation between irregularity of sliver and drafting condition-tube position, ratch, thread angle, etc-was investigated. The experimental results suggest the capability of the high drafting of condensed slubbing.The results obtained are as follows.1. The irregularity of slubbing drafted by using air twister tube has the same order as usual false twister. (Figs. 3, 4) These results substantiate the possibility of air twister.2. The tube setting should be decided by fiber length of the condensed slubbing. Each curve of Figs. 5 and 6 has a minimum value at the point of the longest fiber. Getting the ratch short, the irregularity is slightly reformed, and so, the long ratch as the woollen mule spinning is not necessarily reasonable. (Fig. 7)3. Applying air false twister, drafting with 2_??_3 zone is able to draft higher the woollen slubbing than usual single zone. In this case, the draft ratio of each zone should be limited within the range of CVa/CVb<1.

CONTROL OF DRAFTING BY AIR FALSE TWISTER (1)

In the preceding paper (I), the ability of air twister tube as a substitute for usual twister tube of woollen ring spinning frame was studied.The effects of draft ratio, air pressure and tube dimension on false turns were experimented.The same testing apparatus as in the preceding paper was used in this experiment. The relation between irregularity of sliver and drafting condition-tube position, ratch, thread angle, etc-was investigated. The experimental results suggest the capability of the high drafting of condensed slubbing.The results obtained are as follows.1. The irregularity of slubbing drafted by using air twister tube has the same order as usual false twister. (Figs. 3, 4) These results substantiate the possibility of air twister.2. The tube setting should be decided by fiber length of the condensed slubbing. Each curve of Figs. 5 and 6 has a minimum value at the point of the longest fiber. Getting the ratch short, the irregularity is slightly reformed, and so, the long ratch as the woollen mule spinning is not necessarily reasonable. (Fig. 7)3. Applying air false twister, drafting with 2_??_3 zone is able to draft higher the woollen slubbing than usual single zone. In this case, the draft ratio of each zone should be limited within the range of CVa/CVb<1.

STUDIES ON THE RANDOM SLIVER (V)

The article describes the results of experiments dealing with the irregularity of rayon draftcut sliver (two zone draft-cut system).The theory described in previous reports (Part III and IV), was tested and proved by these expriments the method for experiment used is idential with the case where irregularity of carded sliver was studied.Chief results obtained are as follows: (a) the draft-cuting of sliver caused unevenness to it quite pertinent to the “stational and normal stochastic process”. (b) in the long and the short term irregularity, each serial correlation and the relation between variance and length of sliver were obtained. (c) tuft length distribution and biased length distribution were required for the fiber which constructed the sliver. From the above results, it is recongnized that irregularity of draft-cut sliver belongs to the type of the “random sliver”.

Some Theoretical Considerations on the Irregularity of Drafting

In the following article the author describes, from a statistical viewpoint, three methods of analyzing the irregularity of drafting by evenness of sliver: (1) the method of curve analysis of evenness by utilizing the “time series” theory, (2) the method of obtaining the variation-length curve of long-term irregularity of sliver by using the “stochastic process”, and (3) the method of obtaining the variation-length curve of short-term irregularity by utilizing “probability.” Inter-relations among these methods are also explained.