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The equipment factors of spinning process have a great influence on the quality. Strengthening the control of the equipment factors in spinning process can reduce the influence on the processing quality of the subsequent products, so as to achieve the purpose of improving the quality.

1. Types and characteristics of yarn defects caused by spinning process equipmentAnalysis and control of yarn defects caused by technical spinning equipment

There are two kinds of yarn defects in spinning process, i.e. frequent yarn defects and occasional yarn defects. The common yarn defects are sliver CV, kilometer thick knot, kilometer detail and kilometer NEP; the occasional yarn defects are mainly harmful yarn defects of 100000 meters, with the emphasis on long thick knot and long detail, as well as yarn defects that can be clearly identified. The yarn defects caused by equipment factors lie between the two, which have the characteristics of frequent occurrence and occasional occurrence. They are mainly caused by the operation of machinery. They are common and sudden, not easy to detect and control, great harm, and affect the output and quality. The specific types are: no apron spinning, uneven mechanical wave, slug, wrong branch caused by mechanical variation, feather yarn defects, etc.

2 causes and analysis of common yarn defects in spinning

2.1 spinning defects without lower apron

2.1.1 form comparison

The spinning without lower apron is caused by the out of control of equipment maintenance and operation management in the production process. It produces regular 7-8 cm mechanical waves, which have a great impact on cloth surface and are not easy to find in the actual production,

2.1.2 mechanism analysis

In the drafting motion of spinning roller, the upper and lower leather rings form an elastic jaw, holding the fibers in order to change speed, and focusing on the front jaw to change speed. When there is no lower apron spinning, only the upper apron controls the fiber, the slip rate of NBR and steel roller increases, and the holding capacity of the middle and lower roller rhombus decreases and fluctuates, resulting in the regular irregularity of the yarn under the influence of the mechanical periodic motion during the output.

2.1.3 causes and Prevention

Reasons for spinning without lower apron:

(1) the lower leather ring pin is not flexible and deviated to make the leather ring deviate or fall off;

(2) the inner wall structure layer and support layer of the leather ring are worn, resulting in fracture and deformation, resulting in damage to the leather ring; (3) excessive temperature and humidity, wrapping, hanging and wrapping of the leather ring, resulting in damage and fracture of the leather ring, and the lower leather ring is not replaced in time.

Prevention methods:

(1) strengthen the maintenance, check the quality of leather ring regularly, and replace the unqualified ones in time;

(2) strengthen the basic management, ensure the temperature and humidity in the operation process, and reduce the phenomenon of winding, hanging and winding;

(3) strengthen the sense of responsibility education for operators, and replace the damaged ones in time.

2.2 mechanical wave caused by fracture of upper pin circlip

2.2.1 yarn defect form

When the upper roller is in contact with the cradle, the control spring in the cradle device plays a locking role on the upper roller to maintain the elasticity and stability of the upper roller during operation. After the upper pin spring breaks, the fiber movement in the draft area is unstable, which leads to serious yarn evenness defects, and the CVB between the tubes increases significantly.

2.2.2 mechanism analysis

The spinning cradle is one of the key components of yarn forming, and it is also the application point of the parallel force between the upper roller spacing and the lower roller spacing. The center distance moves forward or backward indefinitely, which causes the fluctuation of the running process and the instability of the fiber movement, and then affects the yarn evenness difference.

2.2.3 causes and prevention of yarn defects

Causes:

(1) incorrect disassembly and assembly method, twist and tear when disassembling the upper roller;

(2) too much pressure of cradle;

(3) the circlip is deformed and the assembly position is not correct, which causes strong extrusion between the upper roller shaft and the circlip shaft.

Prevention methods:

(1) use the correct disassembly method, hold the spring point of the circlip by hand to release the pressure, and take down the upper roller naturally, instead of using the method of hard pulling and twisting;

(2) when the spring adjusts the pressure of the cradle, use the standard positioning gauge to adjust, and prevent the non-standard trial adjustment based on experience;

(3) master the correct assembly method during assembly to prevent the jamming of the circlip.

2.3 spinning machine 6-8cm thick knot yarn defect

2.3.1 yarn defect form

Generally speaking, the 6-8 cm slug defect in spinning process is caused by the slug wrap joint or the slug joint. However, it is found in production that it is actually caused by machinery and air blowing. Its form is 4-5 consecutive slug defects, with a maximum length of 40 cm. It has strong continuity and no regularity. There are fiber cores in the slug defects, hairy outer ends and small twist, which seriously affects the production efficiency of winding drum.

2.3.2 mechanism analysis

Mechanical cause: the key slot is loose due to the shifting wear of roller driving gear, leading to the phenomenon of leading and lagging in the transmission process, resulting in the fiber aggregation in the draft movement of roller to form the coarse yarn defects; blowing and suction cleaner cause: in the middle of blowing and suction, the suction nozzle directly blows the twisting area, resulting in the weak ring in the twisting area, and the air flow directly blows to affect the twisting of the yarn body, and the fiber exposed to form the coarse yarn defects.

2.3.3 causes and Prevention

Mechanical reasons:

(1) the machinery is in disrepair, the standard of flat cleaning car is not high, and the requirements are not strict. Wear the keyway;

(2) the bearing is damaged and the gear engagement is too large, causing abnormal wear;

(3) the adjustment position of the blowing and suction cleaner is not correct, and it is not adjusted according to the regulations when changing.

Prevention methods:

(1) strengthen the mechanical maintenance to ensure that the engagement of the gear meets the standard;

(2) the flat cleaning car shall repair the key slot and key nails in time, and correctly adjust the air blowing and suction position in the installation and twisting area.

2.4 feather and gauze defects caused by hanging of steel wire ring

2.4.1 yarn defect form

Hairiness is one of the important yarn defects that affect the quality evaluation, which usually occurs in the triangle area of drafting and twisting. In the actual production, the hairiness caused by the hanging flower of the steel wire ring not only affects the quality, but also is not easy to find in the detection. Specific shape: the hairiness is concentrated and fine, the appearance is hairy and hairy, the binding layer of winding layer in the bobbin is indistinct, and the hairiness index of 1-9 mm is increased in varying degrees

2.4.2 analysis of formation mechanism of yarn defects

The speed of steel ring is in direct proportion to the front roller speed. When the steel ring is hung or the cleaner is accumulated, the friction between the steel ring and the steel ring increases, and the air flow shape formed by the movement changes, resulting in the pulling movement between the fibers and the formation of hairiness. At the same time, with the increase of the temperature rise of the steel ring and ring, it is not easy to dissipate the heat of the flower bound steel ring, and the air viscosity is large, which affects the polymerization of the fiber; the speed of the steel ring hanging the flower again is not stable, and the tension from the spinning section to the winding section is affected, which increases the diffusion of the edge fiber, and is easy to cause hairiness.

2.4.3 causes and prevention of yarn defects

Causes:

(1) the steel wire ring is rough and has poor quality;

(2) the surface of the ring is rough, which increases the wear of the steel ring and forms hairiness;

(3) the interval between the steel wire ring and the cleaner is too large or does not work, resulting in the poor function of the cleaner and the formation of hairiness;

(4) the relative humidity in the workshop is too low and there are too many flying flowers. It is easy to attach into the steel ring with the movement of the steel ring, forming the hanging flower of the steel ring.

Prevention methods:

(1) different kinds of yarn are separated by different wire ring cleaners. The practice shows that the distance between the wire ring and the cleaner is 1.45 mm, 18.2-22.4 tex is 1.6 mm, 27.85 tex is 1.7 mm, which can effectively prevent the feather defects caused by the hanging flowers of the wire ring. At the same time, the wire ring cleaner must work well. The wire ring without cleaner will hang flowers again after cleaning for 2 hours;

(2) strengthen the operation management, and clean up the hanging flowers once for each yarn falling;

(3) control the flying flowers and relative humidity in the workshop. 

2.5 variation of yarn fineness caused by the fracture of drafting transmission shaft after spinning

2.5.1 yarn defect form

The transmission shaft of FA series spinning frame is long, the transmission load is too large, it is easy to break, and it is not easy to find after breaking. During the detection, the yarn is seriously deviated, and the serious deviation can be determined as grade reduction. In the actual production, the variation of 14.6 tex yarn is 17 tex, 18.2 tex yarn is 19.5 tex, 22.4 tex yarn is 24.6 tex, etc., which will cause the problems of large area of cloth cross and uneven dyeing when flowing into the later process.

2.5.2 analysis of formation mechanism of yarn defects

The rear roller drive bears the buffering and decomposing function of spinning draft distribution. The rear roller draft is an important support point to improve the front draft ability. The main function of the back draft is to prepare for the front area, so that the yarn in the front area of the feeder has a uniform tightness of the structure, at the same time, to ensure the friction boundary distribution in the front area, to form a stable draft area, so as to give full play to the role of the leather loop in controlling the fiber movement, to achieve the purpose of reducing the coarse section and improving the appearance quality of the cloth. When the back area roller loses the original active control of draft multiple, it will be pulled by the inertia force generated by the collective feeding of yarn sliver, and the draft multiple will be reduced. The total draft is the product of all drafting multiples. The change of the back draft multiples causes the change of the total draft. The decrease of the back draft multiples causes the decrease of the total draft multiples and the increase of yarn quantity.

2.5.3 causes and prevention of yarn defects

Reason:

(1) after the rear roller breaks, the front roller drives normally, and the rear roller continues to drive through the roving bar, but the drafting ratio is not controlled, resulting in yarn fineness variation;

(2) the equipment is in disrepair, the maintenance cycle is too long, the transmission shaft is not replaced in time, and the equipment is in fatigue operation;

(3) the position of the front wall panel is twisted;

(4) the test cycle is too long.

Precautions:

(1) when the flat equipment is installed, it is necessary to strictly correct the vertical and horizontal separation distance between the front wall panel and the pagoda base. The longitudinal direction is required to be 11 ± 0.50 mm. The horizontal direction is corrected with special tools, and the 0.10 mm micrometer is taken as the standard; the center line of the wall panel must be controlled within the tolerance of 0.30 mm;

(2) ensure the quantitative deviation of daily test regardless of variety size;

(3) strictly determine the supply of units to prevent expanding the tracking range and reducing the loss in case of problems;

(4) replace the transmission shaft in 5-6 years to prevent fatigue operation;

(5) paint the color mark on the rear roller and check it regularly.

3 conclusion

The main reason for yarn defects caused by spinning equipment factors is that maintenance is not timely at ordinary times. Strict maintenance system shall be adopted to prevent yarn defects caused by equipment factors. The maintenance standard shall be based on the implementation of process requirements of each part. By taking measures, the yarn defects caused by equipment factors can be reduced to a certain extent to ensure the continuous improvement of product quality