The cause analysis and control of the cross bar of knitted yarn(3/4)

3.4 control of rungs caused by twist difference in spinning process

In the spinning process, if the equipment foundation management and operation are not good, the spindle speed will be different, resulting in uneven twist of long segments; unevenness of sliver will cause uneven twist of short segments. The speed of spinning spindle is affected by many factors, such as lack of oil or wear of spindle, irregular beating of spindle belt, gathering and rewinding in bobbin or not being inserted to the bottom, misplacement of spindle belt by operators when cleaning spindle drum, long, short or running up and down deviation of spindle belt, which are easy to cause the difference of spindle speed and twist. There are also tight twists caused by the abnormal rotation of cots, and tight twists caused by the non conformity of the spinning value machine tool joint with the operation requirements. Generally, the spindle speed difference is within the range of 150 rpm and the twist difference is within the range of + / - 2 twists / 10cm, which is normal. If it is beyond this range, it is easy to cause cloth crosspieces. It has been proved from our experiments that when the spindle speed is different, the twist is also different at the same time. In this way, due to the decrease of spindle speed, the weak twist yarn is caused, and the yellow white separation phenomenon is reflected in the fabric color.

3.5 control evenness of strip to reduce accumulation of details and unevenness of weight

(1) as the knitted grey fabric is woven from each yarn separately into a coil string, when there is a significant difference in the thickness of the adjacent two yarns, the fabric will show shadows, so it is necessary to strictly control the 100 meter weight CV% of the yarn, which is generally required to be controlled within 2.0%. To control the CV% value of 100 meters weight, it is important to control the unevenness of the weight of the cotton reels and the carding sliver. At the same time, the production efficiency of the carding and carding machine should be more than 85%, the pressure in the carding air duct should be uniform, the stability of the feeding and cotton flow in the cotton box, the self leveling effect and the fluctuation range of the sliver, the control of the speed ratio between the roller and the cylinder, and the unevenness of the weight of the sliver should be well controlled The phenomenon of strip missing. In the roving process, it is necessary to control the pressure failure of the stick and the leather roller and the even tension control from small to large. At the same time, the roving twist coefficient should be adjusted in time and reasonably according to the differences of raw materials, environmental changes and varieties. Especially in the spinning of chemical fibers, the control of the winding tension and elongation in the roving process is particularly important. In the spinning process, it is necessary to prevent the drafting failure and slippage in the back area and the spindle hoisting Unexpected draft caused by poor rotation, etc.

(2) the deviation of yarn count directly affects the specification and weight of knitted grey fabric. Due to the strong elasticity of knitted fabrics, the different expansion rates of different specifications of knitted grey fabrics, and the different weight loss rates of different colors, the actual count of knitted yarn should be controlled according to the different specifications and dyeing of knitted grey fabrics. Compared with the woven yarn, the knitting yarn is generally required to be coarser and controlled within the range of + 2.5% - 0%.

(3) the CVM% value of yarn evenness is uneven, which has a great influence on knitted fabric. It will cause the loop shape of single yarn is inconsistent and the grain is unclear. When the CVB (%) of yarn evenness is large, it will cause the loop shape difference between different lines, and the fabric surface will be streaked. Generally, CVB (%) of ingot difference is controlled within 2.5.

(4) the influence of details on knitted fabric is fatal. If the raw material causes the fabric to rise from the rung, the fabric can also be used by dyeing light color. However, the difference of strip and dry, especially the influence of details on the fabric surface, cannot be saved. When the details are 20% thinner than the original yarn, there will be shadow details on the knitted fabric surface. When the details are 35% thinner than the original yarn, there will be obvious details on the knitted fabric surface. When the details are 50% thinner than the original yarn, there will be "one circle of fine" details on the knitted fabric surface. If the details accumulate, there will be obvious rung phenomenon. From the current practical experience, it can be concluded that the details of long segment or short segment can be effectively removed by using the advanced model of foreign user company or Swiss LOFI company. Therefore, the configuration of the fourth generation of foreign advanced high-efficiency automatic winder and its electronic cleaner is an ideal detail checking equipment 。

3.6 controlling CV% of yarn hairiness is an important means to reduce rungs

The CV% value of hairiness is also one of the main reasons for the knitted fabric to cross. Especially 3mm hairiness is harmful to yarn line drying and fabric quality. When there is a large difference in the number or type of hairiness between adjacent yarns, the fabric surface effect and dyeing performance will be different, resulting in the fabric horizontal. The factors that affect the formation of hairiness are relatively complex. To control hairiness and its CV% value, in addition to the indexes such as short fiber rate, fineness, neps and impurities of raw materials, it is also necessary to control the fiber damage rate and short fiber removal rate of the pre spinning production link. For example, when spinning chemical fiber raw materials, the blowing process should avoid over striking the raw materials, and the key point of the post spinning spinning process is to reasonably grasp the applicability of steel wire ring to varieties The girth and service cycle shall be guaranteed to ensure the good condition of the ring and the matching use of the steel ring and the ring, especially to reduce the hairiness caused by the too large air ring in the process of skew spindle and yarn winding against the spacer plate. The dynamic control shall be focused on the control of the air ring for the winding of the yarn and fruit. In the process, the draft in the rear area shall be controlled not to be too large and the spacer block shall be reasonably configured. To control the winding speed of winding process, the speed of chemical fiber varieties should be lower than that of pure cotton varieties, so as to reduce the scraping of yarn channel (such as inserting spindle for centering, control of winding tension, smooth yarn channel, etc.). At present, in order to reduce the hairiness of ring spinning, in addition to the measures of speed reduction and steel ring application, the spinning equipment is reformed. Siro spinning and compact spinning are also effective ways to reduce the hairiness.