Analysis Of Common Problems In Quality Management Of Cotton Spinning Enterprises

At present, the spinning equipment of our enterprises is more and more advanced, but the quality of many enterprises is difficult to upgrade. The reasons are manifold. The quality problems are analyzed briefly. The main problems are raw materials, equipment, technology, air conditioning, management and so on. However, the simple management is not good enough, which is also the important reason why the quality is difficult to achieve the desired quality. This paper briefly analyzes the problems existing in daily management, and puts forward some suggestions for improvement. It has certain reference value for improving yarn quality and reducing yarn faults.

1 common problems and suggestions for improvement and management of raw cotton

1.1 raw cotton quality management is not in place.

On the management of raw cotton, many enterprises do not have enough reserves now, resulting in the shortage of raw cotton in batches and the large number of incoming batches, resulting in the problem of chromatic aberration. The amount of cotton reserves must be matched with the amount of production used so that the batch is normal. At the same time, we must strictly control the purchase of raw cotton, and some raw cotton is processed through processing, though the handle is good, but the spinning ability is very poor. Table 1 is the AFIS test data of two batches of real estate cotton used in a cotton mill in China. There is no obvious difference in the handle between the two cotton samples, but from the AFIS test data, we can see that there are obvious differences in the quality indicators. Although the sample 2 may be lower than the sample 1 at the purchase price, its high short staple rate and the number of Khmer knots will directly affect the yarn quality index.

Table 1 Comparison of quality indexes of raw cotton

　　 Although the AFIS test data may not necessarily represent the actual spinning effect, raw cotton with poor quality indicators will not produce high quality yarns. It is suggested that reference to part 2 of the Lida spinning manual can be referred to in the purchase of raw cotton.

Table 2 part standard of Lida spinning manual

　　 1.2 raw cotton bales and cotton bags are not handled properly.

There is no mildew or impurity on the outside side of the raw cotton (see Figure 1). Although most of the blowing carding units are equipped with a perfect foreign fiber cleaning machine and an impurity removal system, it is not possible to remove such dirty flowers and impurities by 100%. .

　　 Fig. 1 moldy or incidental material on the outside side of raw cotton

As can be seen from Fig. 1, the disposal of raw cotton in the pre disposal process is extremely inadequate, which is also a problem neglected by most enterprises.

1.3 raw cotton returning, unreasonable receipt

Some enterprises' receipt management is not in place, resulting in the quality of yarn being affected. The general principle of returning the flowers used in spinning mills is: for ordinary ring spinning, the ratio of reused yarn is generally not more than 5%, and the ratio of combed yarn reutilization is not more than 2.5%. During the use process, the density and placement of bales should be re examined. The packing density of the flower return slip is best close to or consistent with the density of cotton bags. The receipt must be broken before being reused, and the length of the draft is recommended to be less than 30cm. However, some enterprises in the actual use of the process can not be strictly limited, according to the amount of flower back to control the amount of consumption, how much the amount of use, resulting in the proportion of disused between the disc is inconsistent, and even the quality of reuse is also difficult to guarantee, such as a large number of flowers in the back of the rope, the receipt did not tear treatment, etc. (see Figure 2), the quality of yarn has a great impact. ( Network information )

　　 Fig. 2 the quality of returning flower is not qualified.

1.4 raw cotton is not reasonable, and spinning is not enough.

One of the reasons for missing cotton is that the height of packing is inconsistent. Now, Xinjiang cotton, especially the cotton in North Xinjiang and the cotton regain in the southern Xinjiang cotton field, have a great difference in moisture regain. The moisture regain of raw cotton can reach more than 10%, and the minimum is below 6%, resulting in a serious disagreement between the cotton bags after the raw cotton production. Another reason is that the reused flowers and the receipt are not packaged, and they are directly scattered in the package, resulting in the lack of components.

Raw cotton management is the first step in quality management. These problems in the management and use of raw cotton are important problems to be solved in quality management.

2 common management problems of flower cleaning and carding

The diameter and quantity of neps will directly affect the number of yarn neps and yarn defects, especially the number of small yarn defects. The short sliver rate will directly affect yarn strength, minimum strength, hairiness H value and warp breakage, so the cleaning and carding process should not only control the AFIS neps and short fiber percentage, but also consider the fiber's elongation, NEP diameter and fiber uniformity.

2.1 common problems and solutions of flower cleaning

The parameters of cotton grabbing are adjusted frequently, and the operation efficiency of the cotton picker is low. In many small and medium-sized enterprises, the speed of cotton pickup is constant for a long time, but the speed and depth of cotton grabbing are frequently adjusted. It is suggested that the speed of the beater is relatively low. The higher the speed of the driver, the greater the damage to the fiber, which will easily lead to the growth of neps and short fiber. The reciprocating grabbing machine recommends that the operation efficiency control should be over 95%, and the minimum should be over 90%. The depth and speed of grabbing can be determined according to the operation efficiency of the cotton catching machine, and the principle of grasping and running quickly should be grasps. After determining the speed and depth of the grab, the key is to ensure strict implementation, eliminate the operator's random adjustment of the cotton grasping parameters, ensure the continuous supply of cotton in the blowing carding process, and eliminate the empty warehouse phenomenon. Continuous cotton feeding in the cleaning process is the key to ensure the uneven weight of the carding sliver and the mixing effect of the raw materials. At the same time, it is also conducive to ensuring the stability of the cotton flow, ensuring the opening effect and cleaning efficiency of cotton and hetero fiber. According to the cotton distribution and seasonal variation, the speed of each single machine is adjusted in real time to control the growth rate of neps and lint, and ensure the effective removal of neps, impurities, short fiber and foreign fiber, so as to ensure the opening and loosening effect and mixing effect of raw cotton.

2.2 common problems and suggestions for carding

Some spinning mills tend to pay more attention to the removal efficiency of neps and short linen, but they do not pay much attention to the parallelism and carding degree of fibers, which results in better neps and short linen index, but the yarn quality is not satisfactory.

Maintenance of 2.2.1 special parts

The common equipment problems in carding process are mainly focused on special parts and maintenance. Carding process is basically done by combing the original parts, so the maintenance of the original running status is particularly important. Otherwise, even if equipped with high-quality special pieces, poor maintenance can not achieve the ideal carding effect.

It is a common problem for enterprises to extend the chain of the movable cover, chain is not flexible, wear on the heel and toe and the fluctuation of the cover. The cover chain is also a cyclical machine parts that need periodic replacement, but many enterprises do not pay enough attention to it, resulting in many problems in the cover chain.

Attention should be paid to the following main problems in the maintenance of the cover chain and the movable cover frame.

(1) the elongation of the cover chain should be controlled within 76.2mm, and the length difference between the two cover plates is controlled within 3mm. Secondly, we must ensure that the star guide plate is free from abrasion and distortion, and periodically correct the distortion and warping angle of the l4T axis of the star type guide plate.

(2) regular cleaning of the chain and refueling, according to the specified period to check the chain elongation, to ensure that the difference between the length of the two chain meets the requirements, and the shorter one will be used on the main transmission side to prevent the cover plate from running under the condition of not parallel.

(3) adjust the tension of the chain correctly. When adjusting, the middle supporting feet should be the main parts and the rear supporting feet should be supplemented to prevent the tension of the chain from being too large or too small, so as to ensure the tension of the two chains is consistent, while ensuring the horizontal state of the top surface of the cover.

(4) pay attention to the lubrication effect of the lead powder block of the movable cover, ensure that the lubrication condition is good, and prevent the excessive resistance of the cover plate due to poor lubrication, and the elongation of the chain.

2.2.2 cover plate Heel Toe wear and cover fluctuation

The main reason for the incorrect spacing is the abrasion of the heel and toe and the undulation of the cover. In many enterprises, whether the sliding friction cover or the bearing type rolling friction cover, there is a problem of the fluctuation of the cover.

(1) ensure good lubrication of lead powder blocks.

(2) ensure the installation accuracy of the equipment.

(3) ensure the good lubrication state and moderate tension of the movable cover plate chain.

Dust filtering management of 2.2.3 carding machine

Problems such as poor air suction in carding machine (see Figure 3), inadequate cleanliness and movable cover panel (see Figure 4) are also important factors causing poor quality of sliver. The test shows that when the suction tube of the carding machine is blocked, the AFIS neps will increase by more than 2 times than the normal conditions, so that the proper air flow and the ventilation system of the suitable carding machine should be ensured.

　　 Fig. 3 the suction of the carding machine is poor.

　　 Fig. 4 panel applique of carding machine

2.2.4 Carding Clothing Management

Carding Clothing is not only a periodic part, but also a fragile part. At present, the quality of card clothing manufacturing in China is constantly improving, and the use cycle of domestic card clothing is increasing.

(1) there is no perfect replacement cycle of card clothing. The use of clothing is seriously overextended. Some enterprises even use it for more than 6 years.

(2) the use of needles and wounds.

(3) replacing the card clothing without making records, replacing the card clothing without periodic plan, randomness is greater, and the management of card clothing is chaotic.

It is suggested that the management of clothing should be as follows:

(1) to calculate the service life of the card clothing according to the actual output, and to find the best combination points in combination with the use cycle and product quality requirements, so as to ensure the use time of the card clothing and the quality of the products.

(2) when changing the card clothing, we must carry out a strict evaluation. For the accidental damage of the clothing, we must find out the cause and prevent the two injury after boarding.

(3) set up the replacement account of the card clothing to reduce the randomness of the replacement of the needle clothing collar.

(4) constantly carry out the optimization test of the card clothing type. According to the actual situation of the enterprise, choose the brand and model of the card clothing that is suitable for the enterprise.

(5) enterprises with frequent changes in varieties and large changes in raw materials suggest that universal clothing should be selected to take into account the yarn quality level between different raw materials.

Only by fully understanding the performance of carding and cleaning equipment combined with the optimized configuration of special parts and technology can the carding quality and quality of carding be guaranteed, so as to ensure the stability of carding quality index.

3 common problems and suggestions for improvement

3.1 common problems and suggestions for improvement

Drawing frame plays two important roles. One is to achieve the union of slivers, and the other is to promote blending. The two is to clean the stripes. The union of the sliver can achieve the uniform distribution of fibers inside the strip, and increase the parallelism of the fibers. At the same time, the air suction device of the drawing frame can reduce impurities and short fibers in the stripes. Therefore, in the daily use and maintenance process, we must ensure the full play of the two aspects of drawing. At the same time, with the extensive application of self levelling drawing frame and the continuous progress of technology, the control ability of the drawing frame to the weight irregularity of the stripes is further improved, and the long segment irregularity of the yarn is effectively reduced.

Drawing process setting principle of 3.1.1 drawing frame

The number of head fits should be small and not suitable. The total draft ratio should be small and not suitable for large. The draft area in the back zone should be large enough to be small. It is recommended that the draft should be controlled at 1.7-1.8 times in the 5 stages.

It is recommended that the grip area should be small. It is recommended that the roller should be held on the basis of fiber length and appropriately increase 12-20mm to ensure that the fiber is straight and parallel.

The draft area of the rear zone should be small and not suitable for large ones. The drafting ratio of the front zone should be large and small. The greater the drafting ratio of the front zone, the better the straightening effect of the rear crooked hooks. Generally, the draft area is between 1.15 and 1.2, so that one draft can be concentrated in the front area. It is recommended that the draft control in the back zone be about 1.16 times when using the six leveling machine.

Common quality management problems and suggestions in 3.1.2 drawing process

Some enterprises after importing the self levelling drawing frame, because of the unfamiliarity with the equipment, the functions can not be brought into full play, and the expected results are not achieved. The common problem is that the parameters of the self leveling are not reasonable, for example, the slack alarm threshold is slack (see Figure 5), which results in a large A% margin and a large number of coarse nodes (see Figure 6), or inconsistent parameter settings, for example, the difference between the two eyes of the same car is quite different (see Figure 7). It can be seen that there are many problems in the quality monitoring function of the drawing frame used by the enterprises, which reflects that the enterprises have not seriously and effectively adjusted and optimized the monitoring parameters of the drawing frame. It is suggested that every day the enterprise monitor and record the indicators of the drawing frame for statistical analysis. Once the abnormal fluctuation of the monitoring indexes is found, we must find out the reasons for the analysis in time.

　　 Fig. 5 coarse pitch alarm threshold loosening

　　 Fig. 6 the A% range is too large and the number of nodes is too large.

　　 Fig. 7 the difference between the two eyes of the same car is 12mm

It is one of the common reasons that affect the leveling effect, which is inconsistent with the technological parameters of the varieties and even with the technological parameters of the machine. When using the self levelling drawing frame, there will be a uniform alarm in the enterprise. There are many reasons for the uniformity alarm. It is suggested that enterprises should pay attention to the following points in the production process.

(1) the voltage reference value of the self leveling displacement sensor and the concave and convex roller must be accurate.

(2) the leveling length, leveling strength and low speed leveling setting of the self levelling drawing frame should be reasonable and calibrated every 2 weeks to ensure that the above parameters can meet the requirements of production conditions such as raw materials, temperature and humidity.

(3) the setting of alarm values for A%, CV% and rough sections should be reasonable. It is recommended that the test results be set up and adjusted according to the monitoring results of the drawing frame. For combed cotton products, the alarm value of A% is set to be less than 2%. It is recommended that the length of the coarse joint should be set as the length of the cylinder, and the monitoring value will be set according to the actual roughness.

(4) carry out weight calibration test every 2 hours to ensure that A% fluctuation is within the prescribed control range.

(5) ensure clean and timely, stable temperature and humidity. Humidity change is also one of the causes of uniform alarm.

Some enterprises have problems in the operation and management of parallel drawing. The basic cleanliness of drawing frames is difficult to guarantee (see Figure 8), and even lead to the occurrence of defective bars (see Figure 9). At the same time, the operation management does not pay attention to the standardization of operation methods. There are a series of operational problems such as high bar, wool top, joint rubbing head and moving bar. In the operation management, it is necessary to standardize the operation management and realize the overall replacement, so as to ensure the cleaning state of the drawing is good. At the same time, it is necessary to standardize the operation techniques, reduce or even eliminate the stripes defects caused by improper operation (see Fig. 10).

　　 Fig. 8 drawing frame is seriously ill cleaned.

　　 Fig. 9 defects in cleaning work

　　 Fig. 10 defects caused by improper operation of joints

The non self leveling drawing frame should pay close attention to the offline quality monitoring result of the strip quality. According to the quality index of off-line monitoring, the state maintenance and operation quality supervision of the drawing frame should be carried out. The common quality problem of drawing frames is the crooked fibers caused by the poor parallelism between mechanical waves and fiber elongation. For this purpose, the gear engagement status of the drawing frame, the cot roller lubrication and the surface condition of the cots, the adhesion of the cots with flowers and the dust accumulation of the pressure bar are checked in time, and the parameters such as roller spacing and draft distribution are optimized.

3.2 combing common problems and suggestions for improvement

The main task of combing process is to remove short fiber, impurities and some neps. The factors that affect combing carding quality and their complexity are, in general, factors such as the quality of combing preparation process, feeding amount of cotton per clamp, feeding mode, separating distance, cylinder tooth number, insertion depth and bonding quality.

The combing preparation process includes pre drawing and striping. The main purpose of pre assembly is to increase fiber straightness. Problems such as poor cleanliness and poor compatibility often occur in combing preparation process (see Fig. 11).

　　 Fig. 11 unconformity

Combing common problems are combed cylinder, combed top comb, inlay and so on. Combing brush is an important component to ensure the cleanliness of combed cylinder. It is recommended that the insertion depth of comber brush be corrected once a month. According to the actual content of cotton rolls, the speed of brush can be set reasonably.

Combing top comb is an important part of ensuring combing carding effect. A strict combing and top comb handover system should be established to ensure the good condition of the top comb. For the problem of top comb insertion, it is suggested that the noil quantity of top comb and Xilin be tested separately, combined with the noil effect adjustment of carding process to ensure that carding can effectively remove impurities and eliminate the phenomenon of combed top comb.

The amount of combing drafting and small volume is also an important factor affecting combing carding quality. According to the arrangement of combing equipment and the varieties of cotton and spun goods, the bar and coil weight can be reasonably set to ensure the combing and carding effect. Figure 12 is the weight of the small coil of the new comber recommended by Lida.

　　 Fig. 12 small coil weight of the new comber recommended by Lida

The confusion of drafting cots and the poor cleaning of drafting areas are also important reasons for poor quality of combed strips. It is suggested that attention should be paid to detail management of combing, so as to ensure combing and carding and removal efficiency.

3.3 roving common problems and suggestions for improvement

Roving, as the last working procedure before spinning, plays a relatively important role in the rearrangement and straightening of fibers, and has a relatively important effect on yarn quality and yarn defects. So the quality of roving process will directly affect the yarn quality level.

Common problems in roving process are mainly reflected in detail management. Common problems in enterprises are mainly as follows:

(1) the cleaning is not thorough. The draft area is not clean, the upper and lower cleaners are not clean, and the guide bar is not clean. The cleanliness of roving process will directly affect yarn faults, especially the number of one hundred thousand meter cuts. A clean cycle and a supervision and inspection cycle should be established to ensure that the roving process is in good condition.

(2) the position of the cots and the upper pins of the same gear does not match, resulting in the holding interval and the size of the floating area inconsistent, resulting in abnormal yarn roving.

(3) the higher frequency of roving mechanical wave has great influence on yarn quality index. The main causes of mechanical waves in roving process are the poor operation of the drafting and twisting system, the damage of special parts such as cots and aprons, and cots, rollers, etc.

4 Conclusion

The quality of spun yarn determines the quality of yarn. Pre spinning must strictly control detail management, strictly control the balance between the three classes, and lay the foundation for stabilizing and improving the yarn quality.