How to control roving tension and elongation

　1. Roving tension and roving elongation

　 (1) Roving tension Tension refers to the pulling force acting on the axial direction of the yarn, and its expression is the tension of the yarn. During the roving winding process, in order for the roving to be wound smoothly on the bobbin, the winding speed of the bobbin must be slightly greater than the output speed of the front roller, so the yarn must be tense and produce tension. In the process of advancing, the yarn must overcome the friction resistance at the top sleeve of the flyer, the hollow arm, and the pressure palm. Therefore, the tension of each section of the yarn from the front roller to the bobbin is different. The winding tension from the pressure palm to the bobbin is the largest, followed by the tension at the hollow arm, and the spinning tension from the front roller to the flyer top tube is small.

(2) Elongation of roving When the tension on the yarn is large, the yarn will elongate due to the relative displacement between the internal fibers. The degree of elongation can be expressed by the elongation rate ε .

Where: l1 – the actual measured length of the bobbin winding (m);

l2 – the calculated length of the front roller output (m).

Since the spinning section is the yarn formation area, the twist is small and unstable. Although the tension in the spinning section is small, it is easy to stretch. Therefore, it is customary to call the yarn tension in this section the roving tension. . Small changes in the roving tension will sensitively affect the elongation, thereby affecting the uneven weight and evenness of the roving. Therefore, the roving tension is required to be maintained at an appropriate level during spinning, without destroying the uniformity of the output slivers. It is also necessary to ensure sufficient winding density.

(3) The relationship between roving tension and elongation The roving tension can be determined by visual observation of the spinning section. If the yarn is tight, the tension will be large, and if the yarn is loose, the tension will be small. Visual observation can only provide qualitative analysis but not quantitative analysis, so the elongation can be used to indirectly reflect the tension of the roving in production. Factors that affect the relationship between tension changes and elongation changes include raw materials, spinning varieties, flyer structure and materials, whether to use a false twister and the structure and materials of the false twister, machine cross-section size, winding size, process speed, and workshop temperature. Humidity, etc. When a certain false twisting method is used and the temperature and humidity of the workshop are normal, the roving elongation can be used as an indirect method to detect the roving tension. At this time, the elongation should be controlled within the range of 1.5% to 2.5%, and should not exceed 3%. The difference in elongation should be controlled within 1.5%.

In some cases, the change in elongation is not consistent with the change in roving tension, such as:

1. When the tension is normal and the spindle speed is increased, the roving will elongate. The rate will increase due to the intensification of jitter in the spinning section. If the roving twist coefficient is appropriately increased, the roving elongation can be reduced.

2. When the workshop temperature is high and the humidity is high, the friction resistance between the roving and the machine parts increases, the winding tension increases, the increment of the winding diameter decreases, and at the same time, the moisture regain of the fiber increases. As the cohesion force between fibers increases, the relative slip caused by bearing a certain external force will inevitably decrease, which is reflected in the relaxation of the yarn in the spinning section.At this time, the tension increases but the elongation does not necessarily increase.

3. When other conditions are constant, if a false twister is used in the front row, it will have no effect on the law that the roving tension is greater in the front row than in the rear row, but it will have a great impact on the elongation. When the false twister is not installed , the elongation rate of the front row is greater than that of the rear row. When a false twister is installed, the elongation rate of the rear row is greater than that of the front row.

Under the above circumstances, corresponding process adjustments should be made based on the reasons for the change in elongation.

2. Adjustment of roving tension

Under normal circumstances, when the tension of the spinning section is too small or too large according to visual inspection, or the test elongation exceeds the specified range, the roving must be adjusted. Tension adjustment.

On an intelligent roving frame, the setting parameters can be adjusted. On a roving frame with a forming device, a speed changer and a tension compensation device, if the small yarn tension is too large or too small, the tension of the cannon belt can be adjusted. starting position. Move the cannon belt toward the small end of the active cannon, the bobbin speed slows down and the tension decreases. Move the cannon belt toward the big end of the active cannon, the bobbin speed increases and the tension increases.

When the yarn tension is too large or too small, the forming conversion gear can be adjusted. When the number of teeth increases, the belt displacement decreases and the tension increases; when the number of teeth decreases, the belt displacement increases and the yarn tension decreases.

When the tension of small yarn and large yarn is adjusted appropriately, the tension of medium yarn will generally be appropriate. Only when the correction of the cannon curve is unreasonable, resulting in a high slippage rate of the belt in the middle of the cannon, or when the roving diameter increases layer by layer, or when the inconsistency coefficient of the differential device is not equal to zero, the middle yarn tension may exceed the specified range. At this time, you can Tension compensation is used to improve the middle yarn tension.

When processing chemical fiber, since the chemical fiber elastically retracts suddenly after being stretched, if the tension of the roving is too high, accidental drafting may easily occur and the evenness will deteriorate. Therefore, for chemical fibers with high resilience, when pure spinning or blended spinning, the spinning tension should be lower than that of pure cotton spinning. In principle, as long as the yarn from the front roller to the top of the spindle wing is kept from falling, use as low a tension as possible. Under normal circumstances, the tension elongation is negative when the yarn is full, and it is more appropriate to control the tension elongation in the range of +1% to -1.5%.

3. Other measures to improve the excessive elongation of roving

1. The increase in roving elongation caused by the increase in spindle speed is due to the increased vibration of the roving from the front roller to the top of the spindle flyer. The twist coefficient of the roving can be appropriately increased to increase the strength of the roving so as to reduce the elongation of the roving.

　2． The increase in roving elongation caused by high temperature and humidity is because the frictional resistance at the top of the spindle flyer and the pressure palm increases, causing the winding tension and the yarn tension in the hollow arm of the spindle flyer to increase. The number of winding turns of the roving at the top of the flyer and the pressure palm can be reduced to reduce the tension on these two sections of yarn. If the requirements are still not met, the twist of the roving can be appropriately increased to increase the strength of the roving to reduce the elongation of the roving. When taking the latter measure, the drafting device of the spinning frame mustThere must be enough pressure to prevent stretching and hard ends.

4. Other measures to reduce the difference in roving elongation

1. The difference in elongation between machines. Uneven temperature and humidity in the workshop and chaotic processes between machines may cause excessive differences in elongation between machines. Therefore, the setting parameters of each machine and the number of teeth of the conversion gear should be unified. On roving frames with cannon stepless transmission devices, the tightness of the cannon belt should be consistent. For individual machines whose elongation exceeds the specified limit, the starting position of the cannon belt can be adjusted and the forming gear can be changed to make it elongate. The rate is controlled within the specified range.

　2． The difference in elongation between the front and rear rows. Because the distance from the top of the spindle wing to the front roller is greater in the front row than in the rear row, the shaking and twisting phenomena in the front row are more serious, so the elongation rate of the front row is greater than that of the rear row. In order to reduce this difference, the following measures can be taken:

(1) Make the front row of yarn wrap 3/4 times around the top of the spindle wing, or wrap 3 times around the pressure palm, and wrap the back row of yarn around the top of the spindle wing. Wind the top of the spindle flyer 1/4 circle, or 2 circles on the pressing palm, thereby increasing the winding tension in the front row and reducing the spinning tension, which not only reduces the elongation of the yarn above the top of the spindle wing, but also increases the winding diameter of each layer of yarn tube. The increment is smaller to reduce the winding line speed, thereby reducing the elongation of the front row of rovings.

(2) When using large sliver cans for overhead feeding, if the rear row of slivers unexpectedly stretches too much, supply the rear row of spindles; if the front row of slivers unexpectedly drafts small, supply the front row of spindles. Reduce the difference in elongation between the front and rear rows of rovings.

(3) Adjust the specifications of the front and rear false twisters.

　3． The difference in elongation between spindles and spindles. This difference is mainly caused by abnormalities in the spindle, spindle wing, and bobbin. For example, individual spindles are bent and the two arms of individual spindle wings are unbalanced, causing the spindle to rotate and shake; the curvature of the pressing palm is inconsistent, and the yarn pressing force is different, resulting in a different winding diameter of the bobbin; the outer diameter of the bobbin is different, resulting in a winding linear speed The differences are: the inner holes of some bobbins are excessively worn and rotate and shake; the hollow arm channels of some flyers are not smooth and the friction resistance increases, causing the roving to elongate. The above reasons can increase the difference in elongation between ingots. In order to reduce this difference, the maintenance of spindles and spindle wings should be strengthened and the outer diameter of the bobbin should be consistent. If the inner hole of the bobbin is too worn, it should be replaced immediately. 1. Roving tension and roving elongation

(1) Roving tension Tension refers to the pulling force acting on the axial direction of the yarn, and its expression is the tension of the yarn. During the roving winding process, in order for the roving to be wound smoothly on the bobbin, the winding speed of the bobbin must be slightly greater than the output speed of the front roller, so the yarn must be tense and produce tension. In the process of advancing, the yarn must overcome the friction resistance at the top sleeve of the flyer, the hollow arm, and the pressure palm. Therefore, the tension of each section of the yarn from the front roller to the bobbin is different. The winding tension from the pressing palm to the bobbin is the largest, followed by the tension at the hollow arm, and the spinning tension from the front roller to the top tube of the flyer.Small.

(2) Elongation of roving When the tension on the yarn is large, the yarn will elongate due to the relative displacement between the internal fibers. The degree of elongation can be expressed by the elongation rate ε .

Where: l1 – the actual measured length of the bobbin winding (m);

l2 – the calculated length of the front roller output (m).

Since the spinning section is the yarn formation area, the twist is small and unstable. Although the tension in the spinning section is small, it is easy to stretch. Therefore, it is customary to call the yarn tension in this section the roving tension. . Small changes in the roving tension will sensitively affect the elongation, thereby affecting the uneven weight and evenness of the roving. Therefore, the roving tension is required to be maintained at an appropriate level during spinning, without destroying the uniformity of the output slivers. It is also necessary to ensure sufficient winding density.

(3) The relationship between roving tension and elongation The roving tension can be determined by visual observation of the spinning section. If the yarn is tight, the tension will be large, and if the yarn is loose, the tension will be small. Visual observation can only provide qualitative analysis but not quantitative analysis, so the elongation can be used to indirectly reflect the tension of the roving in production. Factors that affect the relationship between tension changes and elongation changes include raw materials, spinning varieties, flyer structure and materials, whether to use a false twister and the structure and materials of the false twister, machine cross-section size, winding size, process speed, and workshop temperature. Humidity, etc. When a certain false twisting method is used and the temperature and humidity of the workshop are normal, the roving elongation can be used as an indirect method to detect the roving tension. At this time, the elongation should be controlled within the range of 1.5% to 2.5%, and should not exceed 3%. The difference in elongation should be controlled within 1.5%.

In some cases, the change in elongation is not consistent with the change in roving tension, such as:

1. When the tension is normal and the spindle speed is increased, the roving will elongate. The rate will increase due to the intensification of jitter in the spinning section. If the roving twist coefficient is appropriately increased, the roving elongation can be reduced.

2. When the workshop temperature is high and the humidity is high, the friction resistance between the roving and the machine parts increases, the winding tension increases, the increment of the winding diameter decreases, and at the same time, the moisture regain of the fiber increases. As the cohesion force between fibers increases, the relative slip caused by bearing a certain external force will inevitably decrease, which is reflected in the relaxation of the yarn in the spinning section. At this time, the tension increases but the elongation does not necessarily increase.

3. When other conditions are constant, if a false twister is used in the front row, it will have no effect on the law that the roving tension is greater in the front row than in the rear row, but it will have a great impact on the elongation. When the false twister is not installed , the elongation rate of the front row is greater than that of the rear row. When a false twister is installed, the elongation rate of the rear row is greater than that of the front row.

Under the above circumstances, corresponding process adjustments should be made based on the reasons for the change in elongation.

2. Adjustment of roving tension

Under normal circumstances, when the visual inspection of the spinning section tension is too small or too large, or the test elongation exceeds the specificationWhen the range is reached, the roving tension must be adjusted.

On an intelligent roving frame, the setting parameters can be adjusted. On a roving frame with a forming device, a speed changer and a tension compensation device, if the small yarn tension is too large or too small, the tension of the cannon belt can be adjusted. starting position. Move the cannon belt toward the small end of the active cannon, the bobbin speed slows down and the tension decreases. Move the cannon belt toward the big end of the active cannon, the bobbin speed increases and the tension increases.

When the yarn tension is too large or too small, the forming conversion gear can be adjusted. When the number of teeth increases, the belt displacement decreases and the tension increases; when the number of teeth decreases, the belt displacement increases and the yarn tension decreases.

When the tension of small yarn and large yarn is adjusted appropriately, the tension of medium yarn will generally be appropriate. Only when the correction of the cannon curve is unreasonable, resulting in a high slippage rate of the belt in the middle of the cannon, or when the roving diameter increases layer by layer, or when the inconsistency coefficient of the differential device is not equal to zero, the middle yarn tension may exceed the specified range. At this time, you can Tension compensation is used to improve the middle yarn tension.

When processing chemical fiber, since the chemical fiber elastically retracts suddenly after being stretched, if the tension of the roving is too high, accidental drafting may easily occur and the evenness will deteriorate. Therefore, for chemical fibers with high resilience, when pure spinning or blended spinning, the spinning tension should be lower than that of pure cotton spinning. In principle, as long as the yarn from the front roller to the top of the spindle wing is kept from falling, use as low a tension as possible. Under normal circumstances, the tension elongation is negative when the yarn is full, and it is more appropriate to control the tension elongation in the range of +1% to -1.5%.

3. Other measures to improve the excessive elongation of roving

1. The increase in roving elongation caused by the increase in spindle speed is due to the increased vibration of the roving from the front roller to the top of the spindle flyer. The twist coefficient of the roving can be appropriately increased to increase the strength of the roving so as to reduce the elongation of the roving.

　2． The increase in roving elongation caused by high temperature and humidity is because the frictional resistance at the top of the spindle flyer and the pressure palm increases, causing the winding tension and the yarn tension in the hollow arm of the spindle flyer to increase. The number of winding turns of the roving at the top of the flyer and the pressure palm can be reduced to reduce the tension on these two sections of yarn. If the requirements are still not met, the twist of the roving can be appropriately increased to increase the strength of the roving to reduce the elongation of the roving. When taking the latter measure, the drafting device of the spinning frame must have sufficient pressure to prevent the draft from failing and causing hard ends.

4. Other measures to reduce the difference in roving elongation

1. The difference in elongation between machines. Uneven temperature and humidity in the workshop and chaotic processes between machines may cause excessive differences in elongation between machines. Therefore, the setting parameters of each machine and the number of teeth of the conversion gear should be unified. On roving frames with cannon stepless transmission devices, the tightness of the cannon belt should be consistent. For individual machines whose elongation exceeds the specified limit, the starting position of the cannon belt can be adjusted and the forming gear can be changed to make it elongate. The rate is controlled within the specified range.

　2． The difference in elongation between the front and rear rows. Because the distance from the top of the spindle wing to the front roller is greater in the front row than in the rear row, the shaking and twisting phenomena in the front row are more serious, so the elongation rate of the front row is greater than that of the rear row. In order to reduce this difference, the following measures can be taken:

(1) Make the front row of yarn wrap 3/4 times around the top of the spindle wing, or wrap 3 times around the pressure palm, and wrap the back row of yarn around the top of the spindle wing. Wind the top of the spindle flyer 1/4 circle, or 2 circles on the pressing palm, thereby increasing the winding tension in the front row and reducing the spinning tension, which not only reduces the elongation of the yarn above the top of the spindle wing, but also increases the winding diameter of each layer of yarn tube. The increment is smaller to reduce the winding line speed, thereby reducing the elongation of the front row of rovings.

(2) When using large sliver cans for overhead feeding, if the rear row of slivers unexpectedly stretches too much, supply the rear row of spindles; if the front row of slivers unexpectedly drafts small, supply the front row of spindles. Reduce the difference in elongation between the front and rear rows of rovings.

(3) Adjust the specifications of the front and rear false twisters.

　3． The difference in elongation between spindles and spindles. This difference is mainly caused by abnormalities in the spindle, spindle wing, and bobbin. For example, individual spindles are bent and the two arms of individual spindle wings are unbalanced, causing the spindle to rotate and shake; the curvature of the pressing palm is inconsistent, and the yarn pressing force is different, resulting in a different winding diameter of the bobbin; the outer diameter of the bobbin is different, resulting in a winding linear speed The differences are: the inner holes of some bobbins are excessively worn and rotate and shake; the hollow arm channels of some flyers are not smooth and the friction resistance increases, causing the roving to elongate. The above reasons can increase the difference in elongation between ingots. In order to reduce this difference, the maintenance of spindles and spindle wings should be strengthened and the outer diameter of the bobbin should be consistent. If the inner hole of the bobbin is too worn, it should be replaced immediately.