Foreword
The spinning yarn cannot be drafted, commonly known as “hard ends”. The fundamental reason is that the drafting force is greater than the holding force. Anything that affects the drafting force and holding force A number of factors may lead to inability to stretch. The main factors include raw materials, technology, machinery, temperature and humidity, etc., which will seriously affect the quality of spun yarn and the production efficiency of spun yarn.
01 Roving twist coefficient
When the roving twist coefficient is large, the tightness of the roving strip increases, and the The resultant force is good, the friction resistance between fibers increases, and the drafting force response increases. Under the condition that the spacing distance of the back zone of the spun yarn and the drafting multiple of the back zone remain unchanged, the sliver cannot be effectively untwisted, and the yarn cannot be effectively untwisted. The twist enters the main drafting area, and the drafting failure occurs. However, the twist coefficient of the roving should not be too small. If it is too small, accidental drafting may occur when feeding the spinning machine, resulting in details and affecting product quality.
02 Spun yarn guide movement
When the spun yarn guide moves When the moving direction of the yarn guide is the same as the twisting direction of the yarn guide, the drafting force is the largest. If the holding force is less than the drafting force, the drafting will not occur. When the twisting direction of the yarn guide is opposite to the moving direction of the yarn guide stroke, the drafting force will be maximum. The force is small, which is beneficial to reducing drafting.
03 Roving ration
The roving ration increases, which means that the fine yarn pulls The drafting force increases during stretching. Under the same rubber roller state and under certain conditions of back zone draft multiple and roving twist coefficient, the spinning holding force required for heavy weight roving is greater than the holding force required for light weight roving. force, so the roving weight has higher requirements on the holding force of spinning yarn drafting. The ration of the roving should be adapted to the nip spacing to avoid drastic fluctuations in the drafting force of the yarn at the nip during the spinning process, which would affect the normal drafting of the spun yarn.
04 Spinning roller gauge
Small roller gauge is beneficial The control of floating fibers in the whiskers increases the drafting force of the whiskers during the drafting process, making it easy to fail to stretch. After the roller gauge is increased, the ability to control the floating fibers in the whiskers is weakened, so that the fibers can be well controlled and drafted normally, avoiding the phenomenon of unable to be drafted.
05 Drafting in the back area of spun yarn
Drafting in the back area of spun yarn After the multiple is increased, the number of fibers in the cross section of the sliver entering the main drafting area is reduced, and the drafting force is reduced, which is beneficial to the control of the fibers in the sliver by the drafting jaws and reduces the phenomenon of unable to be drafted. But in general, it is not conducive to the improvement of yarn quality. Nowadays, most production enterprises use a larger center distance between the back rollers of the spinning yarn, a smaller draft multiple in the back area, and a larger twist coefficient of the roving.
06 Spinning yarn jaw spacing
The smaller jaw spacing block is beneficial to Strengthen the apron jaw’s ability to control the drafted yarn, and have better control over the edge fibers of the yarn when the fiber speed changes, thereby improving the yarn dryness. After the distance block is increased, the control force of the apron jaws on the whiskers is weakened, which can reduce the phenomenon of draft failure, but it will have a certain impact on the quality of the yarn.
07 Spun yarn roller pressure
The roller pressure is small and the pull The stretching jaws have weak control over the fibers, causing the fibers in the strands to not be well controlled and unable to be drafted. After the roller pressure increases, the friction force of the drafting nip increases, so that the fibers in the sliver can be well controlled and drafted normally. The pressure of the front, middle and rear gears of the cradle should be distributed reasonably to avoid drafting failure in the rear area and resulting in failure to open.
08 spun yarn top roller
For new rubber rollers with a paint layer on the surface, the surface paint is thicker and the gripping force on the surface of the rubber roller is greatly weakened. During the drafting process of the rubber roller, the slippage rate is high, so that the yarn cannot be effectively Ground control, easy to hit hard. The paint layer on the surface of the old rubber roller is thin, and the friction factor on the surface of the rubber roller is large. The holding force of the rubber roller on the yarn sliver is greater than the drafting force of the yarn sliver, and the sliver can be stretched normally. If the rubber roller is not treated, there is no chemical treatment on the surface. The surface of the rubber roller can be in direct contact with the whiskers. The friction coefficient is large and the larger holding force can overcome the larger drafting force. It is an effective measure to solve the problem of unable to stretch. . In winter, due to the low temperature, the top roller will become hard if not treated, the slipperiness rate will increase, and hard heads will easily occur.
09 Raw material status
In daily production, raw materials are in constant In the changing state, the fiber quality length in the cotton sliver is lengthened (such as increasing the combed sliver content) or the length uniformity is good, the friction coefficient between the fibers in the sliver becomes larger, and the drafting force response increases during the drafting process, and in the spun yarn When the process remains unchanged, the drafting jaws cannot effectively control the fibers in the sliver, resulting in the sliver not being able to be drafted normally and the phenomenon of inability to be drafted. Other processes need to be adjusted.
10 Temperature and humidity
When the humidity in the workshop increases, the bar must be The friction coefficient between fibers becomes larger, and the frictional resistance response increases, which increases the drafting force of the whisker. When the spinning process remains unchanged, the drafting jaws cannot effectively control the fibers in the whisker, resulting in The phenomenon of inability to stretch. The workshop should reasonably control temperature and humidity according to seasonal changes, raw material conditions and other factors to ensure normal production and avoid drafting failure. </p
