Key points of low cotton rotor spun yarn with weak twist（2/2)

According to the technical characteristics of rotor spinning weak twist yarn, in order to ensure the smooth spinning process, the rotor spinning process should adopt the technological principle of "low speed, small tension, medium pressure, reasonable negative pressure", and reasonably configure the relevant technological parameters.

Determination of twist coefficient: the twist coefficient of weak twist yarn is generally about 100 lower than that of normal yarn, mainly to ensure the smooth progress of twist and spinning. The greater the twist of rotor spinning design, the lower the twisting efficiency; the higher the rotor speed, the lower the twisting efficiency. Due to the low rotor speed and high twisting efficiency of rotor spinning, it should be noted that too high twist will affect the effect of low twist yarn. Generally, the twist coefficient is between 330 and 350.

Selection of stranding disc: generally, stranding disc is selected from the following aspects: first, arc curvature radius, small curvature radius, high twisting efficiency, large curvature radius and low twisting efficiency; R4 ceramic stranding disc with small arc curvature radius has better quality indexes than steel stranding disc and R10 stranding disc with large arc curvature radius; second, material, small friction coefficient of ceramic stranding disc It has strong self-lubricating ability, is not easy to stick cotton wax, has strong consistency, and has stable twisting efficiency. Thirdly, it has low false twisting efficiency when the diameter is small, and high false twisting efficiency when the diameter is large. The selection of large diameter anti twisting disc at the output end is conducive to reducing the end breakage. The R4 series ceramic stranding discs with small curvature radius and large diameter are selected for specific determination.

Determination of rotor diameter and speed: when determining the rotor speed, pay attention to the relationship between the rotor speed and the broken head. The rotor speed is high and the spinning tension is large. When the spinning tension is close to the spinning strength, the yarn is easy to break; at the same time, the rotor diameter is large, the centrifugal force is large, and the spinning tension is large and easy to break; the rotor speed is high and the twisting efficiency is low, and the twist unevenness is not easy to control. The diameter of the rotor is generally small, and the rotor speed is generally 5000 R / min ~ 100000 R / min lower than the normal yarn density.

Determination of the speed of the carding roller: the speed of the carding roller is mainly set according to the spinning raw materials, which depends on the factors such as the impurities in the raw materials, the evenness and strength of the yarn, the old and new degree of the sawtooth, etc. Due to the use of low-grade raw cotton, it is advantageous to increase the speed of the carding roller under the condition of considering air flow. 7100 R / min ~ 7500 R / min is used for specific selection. According to the above principles, the main process configuration of 36.4 tex rotor spinning weak twist yarn is as follows: rotor diameter is 54 mm, rotor speed is 45000 R / min, combing roller speed is 7500 R / min, isolation disc angle is 45 °, tension draft multiple is 0.97, rotor negative pressure is 4500 pa, R 4 (15 / 12 pink ceramic) twister.

Production process problems and control

The difference of CVB between pipes

There is a great difference in CVB between the weakly twisted bobbins in rotor spinning. The main influencing factors are rotor negative pressure and rotor running state. In rotor spinning, the combined coiling of fibers has certain influence on the inter spindle evenness. In the process of merging, whether the fibers are evenly and closely arranged depends on whether the movement of the rotor condensation tank is smooth and whether the rotor speed is stable. In the actual production, a large number of impurities are embedded in the coagulation tank. If they are not removed in time, the strip will deteriorate rapidly, resulting in a large number of regular or irregular rough sections and details. Strengthening the cleaning of the rotor coagulation tank has obvious effect on controlling the difference between ingots.

The difference of Twist Unevenness

There is a big difference of twist in rotor spinning. The main reason is that in spinning low twist rotor yarn, false twist and true twist are less than that of normal rotor yarn. The degree of uniformity of twist distribution in the same yarn section is related to the twist size. At the same time, due to the difference of rotor state, the twist difference is large. The main preventive measures are to strengthen the maintenance, to ensure the consistency of the rotor twisting transmission mechanism state, to ensure that the tension of the transmission belt is too large to grasp, and to ensure that the twisting effect is stable.

Control measures of 17 cm mechanical wave of weak twist yarn

The mechanical wave of 17 cm in weak twist yarn is a common problem in production, which is mainly caused by impurities accumulated in the rotor condensation tank. Specifically, the increase of the coarse pitch is more, and the wavelength of the curve is generally about 17 cm according to the rotor diameter of 54 mm. The preventive measures are to increase the cleaning degree of the rotor, shorten the cleaning cycle, increase the negative pressure properly to enhance the ability of dust removal and impurity removal, and reduce the accumulation of impurities in the rotor condensation tank.

Control negative pressure of rotor to reduce sudden yarn defects

When spinning rotor spun yarn with weak twist, it is easy to produce sudden coarse section, which is mainly caused by low negative pressure and poor discharge of impurities. In the production process of rotor spinning weak twist yarn, the small twist impurities are not easy to wrap in the yarn strip, and the impurities with insufficient negative pressure agglomerate in the rotor groove, resulting in the obvious increase of coarse and fine impurities. The preventive measures are to ensure the smooth ventilation of the process, to stabilize the rotor negative pressure, and to reduce the occurrence of sudden yarn defects.

epilogue

In order to make rotor spun yarn with low matching cotton, the process of opening, carding and drafting should be reasonably arranged according to the characteristics of low-grade cotton and cotton with more lint and high impurity content. The key technological parameters such as rotor diameter, speed, twist coefficient and anti twist disc should be optimized according to the spinning characteristics of weak twist yarn, and measures should be taken to reduce the difference of the evenness and twist between tubes and eliminate the mechanical wave In this way, the rotor spinning yarn with weak twist can be spun smoothly, the quality requirements can be met, and better economic benefits can be obtained.