Influence Of The Slub-yarn Parameters To The Slub-yarn Strength And The Slub Distribution In The Slub-yarn Fabric

Two problems about the manufacture of the slub-yarn are discussed in the paper. The high ratio of broken ends and the uneven slub distribution in the slub-yarn fabric are the two difficult problems during the slub-yarn fabric manufacture, and both of them are closely associated with the slub parameters. The mathematic model and the image analysis method were carried separately to solve the two problems.First, the theoretical investigation and the practice of the slub-yarn are concluded in this paper. The slub-yarn is classified in this paper, and the characters in variety of controlling devices are explained and compared deliberately. The slub controlling device ZJ-5, used in the paper for all the experiments, is introduced in detail.Second, a model for the twist distribution in the slub-yarn is built as a tool for the analysis of the slub-yarn strength. The twist process is simulated as the common bar retorting process, and then the law of the twist distribution in the slub-yarn is carried out after a series of reasonable hypothesis. The calculating formula for the twist in slub yarn is deduced based on the theory of the conversation of twist. The range of application of the formula is discussed through the analysis to some factors and the validity of the formula is testified based on an indirect method.The analysis of the influential factors to the slub-yarn strength is carried on the model mentioned above. The experiment results proved that the slub-yarn with different linear density would have different breaking position. The thicker slub-yarn is easy to break at the slub part, while the thinner slub-yarn breaks at the base yarn part, although the two kinds of slub-yarns have the similar twist distribution. On the other hand, the slub length will increase the strength of the slub parts when it is shorter than the fiber principal length. Two efficient methods are necessary to increase the strength of the slub-yarn during its designg: one is to increase the twist in the slub part for the thicker slub-yarn; the other is to adjust the twsit in base yarn under the critical twist for the thinner slub-yarn.Third, the evenness for the slub distribution is discussed. An assessment method for the slub distribution is advanced at first. The indices in the image analysis, the center of mass P(x_m,y_m ) and the area As is taken as the new indices to assess the slub distribution. Some image samples are prepared through the scanner for the assessment, and the time domain method and the frequency domain method are carried separately to extract the slub parts from the fabric shading to acquire the binary images from the sample images. The distribution evenness is related to the CV% (coefficient value) of A_s in the sample binary images and the excursion extent D of the center of mass P to the geometric center O. The even distribution would lead less CV% and less D. The CV value of A_s in different samples can not exceed 10% and the maximum of D can not reach the 10% of the sample size in a slub-yarn fabric with even slub distribution.The simulating method is carried to acquire the binary image based on the slub-yarn parameters and the weaving parameters, which helps to shorten the slub-yarn fabric designing process. The influential factors to the slub distribution are tested through the simulation. The test result proved that, the change of the slub-yarn parameters influence the slub distribution little with the high slub-yarn ratio; while to the fabric with littile slub-yarn ratio, the slub parameters is sensitive to the slub distribution, and the smaller difference between the slub lengths in the non-periodic slub-yarn will increase the slub distribution evenness.