Introduction
As customers continue to improve yarn quality requirements, spinning enterprises must standardize production operations, pay attention to equipment maintenance, optimize process adjustment parameters, and strengthen quality control. , thereby effectively reducing yarn defects.
Classification of yarn defects
1.1 Classification based on the probability of occurrence of yarn defects
It can be divided into regular yarn defects and occasional yarn defects.
1.1.1 Frequent yarn defects
Common yarn defects include kilometers of neps and kilometers of thick places and kilometers of details. Frequent yarn defects are short, small, and numerous, and are difficult to remove thoroughly. Generally, they will not have a serious impact on the weaving production efficiency and fabric defective rate, but they will have a significant impact on the surface style of the fabric. Therefore, frequent yarn defects must also be controlled. The number of hairy yarn defects.
1.1.2 Occasional yarn defects
Occasional yarn defects are also called sudden yarn defects, which usually occur suddenly. , wider coverage and greater harm. Occasional yarn defects are mostly caused by poor production management, poor operation, poor operating status of equipment and parts, unreasonable process design, etc. They will have serious adverse effects on subsequent processes and fabric quality, so they must be eliminated.
In the production process, occasional yarn defects often appear suddenly as certain influencing factors change, quickly affecting some varieties or areas on the production line, causing certain quality indicators to appear. Larger fluctuations.
1.2 According to the nature of yarn defects and the hazard classification to fabrics, yarn defects can be divided into raw material yarn defects, drafting yarn defects and operation management There are three categories of yarn defects.
1.2.1 Raw yarn defects
Raw yarn defects are usually caused by poor performance of raw materials or poor opening and carding. For example, the fiber length uniformity is poor; the difference in linear density is too large; the short staple rate is high; the maturity is low; the content of neps, leaf scraps, cotton seed hulls, and fiber seed scraps is high; the separation and straightness of the fibers , parallelism difference, etc. Generally, yarn defects in raw materials are short and small, and they mostly appear as recurring yarn defects.
1.2.2 Drafting yarn defects
Drafting yarn defects are caused by unreasonable design of process parameters, such as The distance between the rollers is too large or too small, the draft ratio configuration in the rear area is unreasonable, the apron jaws are too large or too small, the rubber roller apron is too hard or too soft, the grinding cycle is unreasonable, and the carding parts are beaten, causing the fibers to bend. It is caused by poor hook straightness or poor fiber overlapping during the drafting process and is broken. Draft yarn defects are sporadic yarn defects, most of which appear as thick places and long details of 1 cm to 4 cm. They are more harmful to the fabric surface and are often called harmful yarn defects.
1.2.3 Operation and management of yarn defects
Mainly refers to long details and long slugs with a length greater than 4 cm. It involves many aspects such as equipment, technology, operation management, temperature and humidity, etc. For example, coarse details caused by poor joints of the turner; flying particles and velvet chips caused by the maintenance workers and the turner not cleaning the machine thoroughly. In addition, due to poor maintenance or poor operation by the operator, crooked spindles, crooked balloons, deflection of the ring plate, and hairy bobbin hair have resulted in large areas of hairy yarn; damaged rubber roller aprons or cotton yarn passages have caused hangovers. Details of bamboo sections, thick sections, etc. These two types of yarn defects are generally reflected clearly on the fabric. They are harmful yarn defects and need to be focused on control.
1.3 According to the process classification of yarn defects, they can be divided into semi-finished yarn defects and finished yarn defects.
1.3.1 Semi-finished yarn defects
Semi-finished yarn defects include velvet board flowers, oily flowers, dirty flowers, flying flowers attached or Bad sliver joint wrapping causes knotted slivers, thick and thin slivers, wool slivers, hanging flowers, foreign fibers mixed in, etc.
1.3.2 Finished yarn defects Finished yarn defects include regular slubs, yarn waste, flying flowers, poor threading, and oily yarn. , delooped yarn, poor bobbin formation, weakly twisted yarn, strongly twisted yarn, hairy yarn, uneven evenness, cotton yarn, slub yarn, detailed yarn, etc.
Correctly understand various yarn defects
Only every employee of the enterprise can understand the types, causes and causes of defects in this process. Preventive measures, especially operational management of yarn defects, can effectively prevent and control yarn defects and stabilize product quality.
2.1 Types of front yarn defects
Here are some common and most likely to occur Defects in roving must be caught in time during the spinning process to ensure that each roving is subject to strict quality control.
Figure 1 Flying flowers, velvet board flowers, and spindle wing hanging flowers
Figure 2 Cleaning flying flowers, dirty flowers and oily flowers
Figure 3 Foreign fiber clamping
Figure 4: Shabby yarn (rotten yarn)
2.2 Types of defects in the spinning process
2.2.1 Long segment coarse details
There are several main reasons for the formation of long segment coarse details:
1) Roving tailThe bar sags and is brought in, causing double feeding (as shown in Figure 5), falling off and floating (as shown in Figure 6), interrupting adjacent yarns and causing the rubber winding roller, and the roving end to bring in adjacent yarns when changing rovings, or the roving end is too long.
Figure 5 Double feeding of roving
Figure 6 The yarn tail falls off and floats
To prevent this kind of defect, workers who change roving should pay special attention to hanging it. The yarn tail of the roving cannot fall off or float. The tail must be glued first and then hung with roving.
2) The back roller spins around the roving. If the back roller continues spinning around the pattern, this spindle will produce long thick spots, and another spindle under the same cradle may also produce long thick spots due to insufficient pressure on the rear rubber roller. When the operator discovers this phenomenon, he must promptly remove the yarn defects produced on the two spindles.
3) The yarn guide stroke is too large and the roving deviates. In this case it is easy to produce thick yarn. If the operator discovers that the yarn guide travel is too large or the roving is off-track during his rounds, he must promptly notify the mechanic to repair and deal with it.
4) Block the flowers with fine yarn at the bell mouth. Flying flowers at high altitude in the spun yarn, flying flowers in the drafting part, and hanging flowers in the roving spindle wing will cause the flowers to be blocked at the bell mouth of the spinning yarn, resulting in uneven drafting of the spinning yarn and causing thick details.
2.2.2 Uneven dryness
The main reasons for uneven yarn dryness are as follows:
1) The rubber roller is bent eccentrically, the rubber roller is short of oil and is beating. When working, the lathe operator has to touch the rubber rollers one by one to promptly detect and replace any damaged or worn rubber rollers to ensure the stability of product quality.
2) The rubber roller is severely entangled, causing poor pressure on adjacent yarns and seriously affecting the stability of the fiber holding force of the holding jaws. Therefore, if you find that one rubber roller is winding while another spindle in the same gear is still spinning (see Figure 7), you must interrupt the adjacent yarn, pull out the uneven yarn, and then reconnect it to continue spinning. yarn.
Figure 7 Rubber roller winding
3) Regular Bad yarn. The rubber roller is seriously short of oil; the rubber roller and apron ring are severely beaten or damaged, and flying flowers are embedded in the rubber roller; the spun yarn is broken, the cotton suction flute is blocked, and the sliver floats into the adjacent yarn; the upper and lower aprons are wrapped around the roving head and the yarn is still spinning Yarn; accumulation of flowers in the drafting area and attached whiskers, etc. will cause regular yarn defects. Therefore, it is necessary to strengthen the inspection of damage to rubber rollers and aprons. In particular, damage to the lower apron is difficult to find, and special spot checks must be carried out.
2.2.3 Risky yarn
The main reasons for the occurrence of false yarn:
1) The position of the ring plate is too high or too low. When doffing and driving, be sure to pay attention to the position of the ring plate. For long-distance vehicles, it is more important to pay attention to whether the height of the ring plate at the front and rear of the vehicle is consistent.
2) The bobbin is uneven and the bobbin is not inserted to the bottom. When doffing and inserting the yarn, the doffer must insert the yarn bobbin to the bottom to avoid bobbin skipping, which may cause yarn backing on the spindle and lead to yarn head and foot yarn leakage (see Figure 8). For the colony long car, observe whether the tube is inserted to the bottom after collective intubation, whether the yarn is wrapped around the spindle, or whether individual spun yarn tubes are deformed and cannot be inserted to the bottom, etc.
Figure 8 Taking risks
2.2.4 Hairy yarn
The main causes of hairy yarn are: defective steel ring; worn, burned, and embroidered traveler; improper passage parts such as yarn guide hook and traveler Smooth; crooked spindle, crooked balloon, ring deviation, ring plate movement; wire ring touching the gauze plate too lightly, etc. It is necessary to let the machine operators understand the several situations that produce hairiness, so as to dynamically control product quality more effectively. Every time the operator pulls out the bobbin, he should pay attention to whether the bobbin is hairy. Once any abnormality is found, he should check it carefully and report it in time.
2.2.5 Collision of steel ring yarn
The main cause of collision of steel ring yarn: steel wire The loop is too light; the bobbin forming is too large (improper adjustment of process parameters or gears); the spindle belt is loose; overweight yarn; bobbin skipping, spindle shaking, etc. If the machine operator finds that the ring yarn is bumping, he should promptly find out the cause and find a machine repair or craftsman to solve it.
2.2.6 Oily yarn
The main causes of oily yarn: raw materials or cotton slivers, The roving itself is stained with oil; the bobbin is stained with oil when it falls to the ground; the oily hand joint or doffing tube is stained; the drafting parts after wiping the car with flat hands are stained with oil; the yarn loading container is stained with oil, etc. Therefore, it is strictly prohibited for car operators to operate oilers with their hands. Mechanics must pay attention to quantitative refueling to prevent contamination of semi-finished products or finished products.
2.2.7 Cross spinning of Siro spinning yarn
The two rovings of Siro spinning are When entering the front drafting zone, a certain distance should be maintained, otherwise it will affect the strand style of the yarn and increase hairiness. However, in the actual production process, cross-feeding sometimes occurs (see Figure 9), which must be corrected and dealt with in time. The lathe on duty must completely change the bad operating actions. After handling the rubber roller and roller winding, while pressing down the cradle, first separate the two rovings with hands or bamboo sticks, and then join them. This way, cross-spinning can be completely eliminated. yarn.
Figure 9 Siro spinning cross spinning
2.2.8 Defects in evenness caused by blockage of special-shaped tubes in Siro compact spinning and adhesion of grid circles
Siro Condensed spinning relies on the negative pressure effect formed by the special-shaped tube and the mesh circle to condense the fibers. Once the special-shaped tube is blocked and the mesh circle is sticky (see Figure 10), it will affect the cohesion of the fibers and thus the yarn. quality. Therefore, it is necessary to ensure that the negative pressure of the fan is maintained within the standard range and cycle management is strictly implemented. If the blocker finds that the special-shaped pipe is blocked or the mesh ring is stuck during the tour, it should be eliminated in time.
Figure 10 Flower accumulation and cotton blocking in special-shaped tubes
�Separate the two rovings and then join them together to completely eliminate cross-spinning.
Figure 9 Siro spinning cross spinning
2.2.8 Defects in evenness caused by blockage of special-shaped tubes in Siro compact spinning and adhesion of grid circles
Siro Condensed spinning relies on the negative pressure effect formed by the special-shaped tube and the mesh circle to condense the fibers. Once the special-shaped tube is blocked and the mesh circle is sticky (see Figure 10), it will affect the cohesion of the fibers and thus the yarn. quality. Therefore, it is necessary to ensure that the negative pressure of the fan is maintained within the standard range and cycle management is strictly implemented. If the blocker finds that the special-shaped pipe is blocked or the mesh ring is stuck during the tour, it should be eliminated in time.
Figure 10 Flower accumulation and cotton blocking in special-shaped tubes</p
