The quality of cotton laps (cotton flow in the blowroom and carding union) is the basis of cotton yarn quality. It should have length and weight that meet the specified standards, uniform thickness, less impurities, good opening, and smooth appearance. Failure to meet this requirement constitutes a defect.
Lap weight unevenness and elongation
Cotton roll weight unevenness includes longitudinal unevenness and transverse unevenness. In production, the longitudinal unevenness is mainly controlled, because it directly affects the weight unevenness of carded slivers and the weight deviation of spun yarns. The transverse weight unevenness of cotton laps represents the transverse weight difference of cotton laps. It mainly affects the uniformity of the cotton layer’s transverse holding by the cotton feed roller of the carding machine, thereby affecting the carding quality of the carding machine. Therefore, cotton lap weight unevenness is an important indicator of cotton lap quality. The following are the main factors affecting the uneven weight of cotton rolls and their solutions.
Raw material properties
Whether raw cotton or chemical fiber, in order to prevent fiber Due to uneven mixing caused by differences in properties, it is necessary to minimize the property differences of various fibers in the mixed components. Special attention should be paid to reducing the differences in fiber linear density, length, initial modulus, and differences in packaging density and fiber hygroscopic properties.
Reasonable control of the moisture regain of raw materials is an effective measure to ensure a uniform and stable blending ratio. For example, polyester/viscose (T/R) blending, the moisture regain of viscose fiber fluctuates with the changes in outdoor air, raw material warehouse and workshop temperature, and there is a hygroscopic hysteresis phenomenon, and the error is 1.8% to 2.0%; at the same time, viscose fiber The moisture regain may be too large (>17%) or too small (<9%), and different moisture release conditions may also lead to systematic fluctuations in the total viscose fiber content. Because the general cotton distribution is mostly based on sampling inspection of moisture regain, the deviation of sampling inspection representativeness due to raw material package differences and position differences directly causes fluctuations in the blending system. When encountering the above situation, it is best to use the method of inspecting packages one by one, allocating cotton according to the actual moisture regain, and controlling the amount of viscose fiber that is too large or too small for moisture regain to be below 7%.
Process Factors
1) Improvement of the arrangement of cotton catching beaters
For example, if the number of teeth of the beater blade of a cotton plucker is changed from the inside to the outside, the inner group is from the 1st to the 12th blade, with 9 teeth on each blade; the middle group is from the 13th to the 20th blade. Each piece has 12 teeth; the outer group is the 21st to 31st pieces, each piece has 15 teeth. This arrangement can compensate for the difference in weight of the beater’s radial cotton grabbing blocks and achieve fine cotton grabbing.
In addition, two cotton picking machines grab fibers at the same time, and use the segmentation method of two cotton picking machines with different bale heights to reduce the friction between the upper and lower layers of the cotton pile. Blending differences.
2) Process parameters
The speed and spacing of each machine part in the cotton box should be appropriate , the feeding amount and output amount of the front and rear machines per unit time should maintain a certain relationship. Generally, the feeding amount is slightly greater than the output amount. For example, the output of the porcupine opener should be about 20% greater than the total output of the cleaning machine. If the difference between the feeding amount and the output amount is too large, the operating efficiency of the cotton picking machine will be reduced, and the amount of cotton in the cotton box will fluctuate greatly, which will not only affect the opening and impurity removal, but also cause uneven cotton output. Under normal circumstances, the operating efficiency of the cotton picking machine should be 80% to 85%, and the operating efficiency of the cotton box machine should be 85% to 90%. Therefore, when the cotton cleaning machine output, cotton lap ration, and raw cotton density change, the output of each machine needs to be adjusted to balance the output of the cotton cleaning machine. Such as adjusting the speed of the brad curtain of the cotton mixing machine, the distance between the brad curtain and the cotton equalizing roller, the thickness of the cotton storage box of the porcupine cotton opener and the rotation speed of the cotton feeding roller, etc. As long as the output is met, the cotton picking machine “grabs more often and less”, and adopts a smaller spacing between the razor curtain and the cotton leveling roller, which can increase the operating rate and facilitate the uniformity of the cotton rolls.
The cleaning machine should choose an appropriate beater type. The fan speed is 10% to 25% higher than the beater speed. The cotton collection ratio of the upper and lower dust cages is 7:3; at the same time, the balance The adjusting device should be in normal condition and move sensitively.
Bale arrangement
The cotton bales are mixed cotton from the cotton picking machine The unit is also called the blending component. Each time the disc-type cotton picking machine rotates, a blending unit is completed. With a reciprocating cotton picking machine, if the cotton bales are arranged properly, a blending unit can be completed in one single pass. On the contrary, It takes one round trip to complete a cotton blending unit. It is required that the various cotton proportions in each cotton mixing unit be kept to a minimum, and the various components are captured evenly. The composition between each blending unit must be stable.
The bale arrangement diagram of the disc-type cotton picking machine should be based on the principle of “axially staggered and circumferentially dispersed” for cotton bales of the same composition in the beater. At the same time, the bale arrangement should be at different axial positions of the beater. The difference in the average grade of each ingredient should be minimized so that the car can avoid repeated grabbing of the same ingredient and the average grade of the raw materials grabbed at each position is close to each other. The amount of cotton mixing units of the reciprocating cotton picking machine is much larger than that of the disc type, so its own “reasonable arrangement and even grabbing” is particularly important. It seems impossible to require that the packaging composition of each cross-section be exactly the same, but it should be done as reasonably as possible.
There are many factors that affect the different elongation rates of cotton rolls. The main reasons are the different depths of the roll roller grooves between the machine tables and the different pressurization weights; the surface of the brake leather parts Worn or stained with oil, poor contact between the leather block and the brake disc, improper position of the brake lever weight, etc.; the full roll automatic stop device is poorly installed or the parts are worn out; the cotton roll is bent; the cotton distribution or process difference between the machines is too large ; The temperature and humidity in the workshop fluctuate too much; the unwinding is not timely after full roll; the fixed-length system gears are used incorrectly, etc. In this regard, it should be added��Maintenance and inspection.
The impurity content of cotton rolls
In both cleaning and combing In the process, cotton cleaning generally removes large impurities, such as cotton seeds, seed cotton, infertile seeds, broken seeds, etc.; carding removes small impurities and short lint, such as fibrous seed scraps, soft seed epidermis, etc. The individual machines of the combined blowroom and blowroom machines have different structural characteristics and different impurity removal efficiencies. Therefore, the strengths of each machine should be fully utilized to achieve the purpose of reducing yarn impurities and neps and saving cotton.
Cotton box technology
The cotton box machine adopts multi-pulling and loosening process to weaken the adhesion between impurities and fibers. The first cotton box stripping beater is equipped with a larger dust rod spacing to create conditions for cotton seeds, seed cotton, large broken seeds and other large impurities to fall off early and fall before they are broken, and fall out more frequently. .
Raw materials with different properties
Use different processes to treat infertile seeds More raw cotton should give full play to the role of various beating machines to reduce its residual amount in the cotton roll (otherwise, impurities and short fibers in the sliver will increase after carding). For raw cotton with soft seed skin and a lot of fibrous seed scraps, the role of the carding needle beater should be fully utilized, and for the main beaters such as porcupine beaters and six-cylinder beaters, smaller dust rod spacing, less air supply, and full dead boxes should be used Wait for the cleaning up of fine craftsmanship. For raw cotton with high impurity content and roller cotton with an impurity rate exceeding 5% or containing a lot of large impurities, they should be pretreated separately before mixing. However, sawtooth cotton containing a lot of fine impurities cannot be pretreated because sawtooth cotton has more neps and is more likely to produce neps after pretreatment, which is detrimental to improving quality and saving cotton. For raw cotton with too high water content, the method of exposing, drying and loosening the cotton should be used, and then mixing it after drying; for raw cotton with too low water content (less than 7%), it is generally wet first and left for 24 hours before mixing. For long-staple cotton, the process principle of “loose, beat lightly, and reduce tumbling” should be adopted. If the process of fine-staple cotton is still used, it will easily cause fiber damage and increase the bundles in the cotton roll, affecting the quality of the cotton roll; low-grade cotton is generally used Separately into strips, parallel strips and blended. The blowroom process adopts the “more loosening, less blowing, slow speed, less recovery” process. The porcupine beater speed is selected from 400r/min to 450r/min, and the carding beater speed is selected from 700r/min to 900r/min to reduce fiber damage. . </p
