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Causes and analysis of common yarn defects in spun yarn

Update:30-04-2020
Summary:

Spinning process equipment factors have a great impact […]

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

1 The types and characteristics of Polyester Sd Yarn defects caused by equipment factors in the spinning process

There are generally two types of Polyester Sd Yarn defects in spun yarn processes: normal yarn defects and sporadic yarn defects. Frequent yarn defects are generally sliver CV, kilometer thick knots, kilometer details and kilometer neps; occasional yarn defects are mainly 100,000 meters of harmful yarn defects, with emphasis on long thick knuckles and long details, and can be clear Qualitative yarn defects. Yarn defects caused by equipment factors are between the two. They have frequent features and occasional manifestations. They are mainly caused by mechanical defects during mechanical ope

ration. They are common and sudden, and are not easy to detect and control. Harmful, affecting yield and quality. The specific types are: spinning without aprons, uneven mechanical waves, thick knuckles, staggers caused by mechanical variation, hairy yarn defects, etc.

2 Causes and analysis of common Polyester Sd Yarn defects in spun yarn

Morphological comparison

Spinning without aprons is caused by the out-of-control of equipment maintenance and operation management during the production process. It produces regular 7-8 cm mechanical waves, which has a great influence on the fabric and is not easy to find in actual production.

Mechanism analysis

During the drafting movement of the spun yarn, the upper and lower aprons form elastic jaws, which hold the fibers in an orderly shift and focus on the forward jaws. When spinning without aprons, only the aprons control the fibers, the slip ratio of nitrile rubber and steel roller increases, and the diamond-shaped pattern of the middle and lower rollers reduces the ability to hold the fibers, resulting in fluctuations, resulting in yarn The influence of mechanical periodic motion produces regular unevenness.

Causes and prevention

Reasons for spinning without aprons:

(1) The operation of the lower apron pin is inflexible and offset, causing the apron to run off or fall off;

(2) The inner wall structural layer and supporting layer of the apron are worn, resulting in breakage and deformation, which causes damage to the apron; (3) The temperature and humidity are too large, and the apron is wrapped, hung, and wounded, causing the apron to be damaged and broken. Aprons.

Prevention methods:

(1) Strengthen maintenance, regularly check the quality of the apron, and replace it if it is found to be unqualified;

(2) Strengthen basic management, ensure the temperature and humidity during operation, and reduce the phenomenon of entanglement, hanging and winding;

(3) Strengthen the education of the operator's sense of responsibility, and replace it in time when damage is found.

2.1 Polyester Sd Yarn defect shape

 

When the top roller is in contact with the cradle, the control spring in the cradle device locks the top roller to maintain the elasticity and stability of the top roller during operation. After the upper pin spring is broken, the fiber movement in the drafting zone is unstable, causing serious uneven yarn defects, and the CVb between the tubes is significantly increased.

 

2.2 Mechanism analysis

 

Spinning cradle is one of the key components of yarn formation, and it is also the point of force application of the parallel force between the upper roller gauge and the lower roller gauge. After the upper roller snap spring breaks, the position of the upper roller loses control and is affected by motion vibration. The indefinite forward or backward movement of the center distance causes fluctuations in the running process and instability of the fiber movement, which in turn affects the difference in yarn sliver.

 

2.3 Causes and prevention of Polyester Sd Yarn defects

 

Reasons for formation:

(1) Incorrect disassembly method, twist and tear when removing the top roller;

(2) Excessive pressure on the cradle;

(3) The circlip is deformed and the assembly position is not correct, so that the upper roller shaft and the circlip shaft are strongly compressed.

 

Prevention methods:

(1) Adopt the correct disassembly and assembly method, release the pressure against the elastic point of the circlip by hand, and take off the upper roller naturally, instead of using a rigid pulling and twisting method;

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

(3) Master the correct assembling method during assembling to prevent the circlip from being crushed.

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