Analysis of automatic tension detection and adjust

2022-10-03
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Analysis of roving frame tension automatic detection and adjustment system

the newly developed FA481 and FA425 roving frames in China replace the cone wheel speed change mechanism, tension fine adjustment device and forming mechanism with modern frequency conversion and speed regulation technology, programmable logic controller (PLC) and electronic roving tension detection and adjustment system, which greatly simplifies the structure of roving frames and represents the highest level of modern suspension roving frames in China, The intensity of the process adjustment and maintenance of the roving frame is greatly reduced, and the roving frame is basically automated. The high-precision CCD sensor can automatically detect the roving tension state at random, and can always maintain the best value of roving tension for different spinning varieties, creating good conditions for improving roving quality

1 defects of tension control of roving frame of cone wheel speed change mechanism

if the front roller jaw of roving is set, the parameters of material such as yield strength, tensile (compression, bending) strength, elongation, non proportional strength, elastic modulus, etc. can also be detected. The sliver speed is V, the roving winding diameter is DX, the spindle speed is N0, and the bobbin speed is NX, then there are: nx=n0 + v/2 π dx

generally speaking, The thickness of the roving winding layer increases from the inner layer to the outer layer according to the equal difference series. When the cone pulley belt moves at equal intervals each time, the cone pulley shape curve of the roving machine is designed into a double curve. Due to the unreasonable process design and unstable raw materials, the spinning tension is unstable, and the roving elongation and its difference at one doffing and between stages are quite different. Although the pre-set fine adjustment compensation device for roving spinning tension is adopted, the roving cone pulley belt changes from equal spacing movement to variable spacing movement according to the spinning situation, which reduces the roving elongation and its difference and end breakage rate to a certain extent, and improves the yarn evenness. However, when factors such as feeding raw materials fluctuate, roving tension instability, roving elongation and their differences will still occur. In addition, the technical difficulty and workload of the initial spinning and daily adjustment of roving tension have a great impact on the product renovation

2 working principle of roving tension automatic detection and adjustment system

2.1 roving tension control system

the size and stability of roving tension completely depend on the winding speed of the front roller jaw, and what are the advantages of Jinan assay impact sample broaching machine? The relationship between bobbin speed, spindle speed and Longjin lifting speed. Through the detection of roving tension detection sensor and the transmission of its information to the single chip microcomputer, the PLC control system can achieve the predetermined spinning tension requirements. The roving tension detection adopts a high-precision CCD linear displacement image sensor - electronic eye, and its measurement accuracy is up to 0.1mm. The roving tension detection device judges whether the roving tension is appropriate or not by detecting the roving position state at a specific position at an instant. Its detection principle is shown in Figure 1

2.2 the relationship between the position of the roving section and the tension of the spinning section

2.2.1 the situation when the roving frame is spinning

generally speaking, when the roving frame is spinning, its spinning tension is whether the spinning is normal or not, It can be divided into three cases:

the first case is that the roving in the spinning section is straight and accompanied by severe jitter, that is, the roving spinning tension is too large. Due to the force on one side of the spindle wing, the rotating spindle is in an unbalanced state. Coupled with the dynamic balance state of the spindle wing and the coaxiality of the spindle and the bobbin movement, the spindle swings, the roving in the spinning section is straightened and vibrates violently. At the same time, the length of the roving twisting triangle fluctuates, which is not conducive to the stability of roving elongation and makes the roving elongation fluctuate greatly

in the second case, the roving in the spinning section is seriously relaxed, the tension is small and extremely unstable, and the twisting triangle is long and unstable, even "fried dough twist". As the twist triangle area increases, the fibers in it are loose and the connection between them is weakened, which is not conducive to the transmission of roving twist back to the twist triangle area, and also leads to excessive and unstable roving elongation

in the third case, the roving in the spinning section is tight without straightening and oscillation, and the falling can make the twisting triangle area twist back and stable. In this way, the tension of roving spinning section can be stabilized, and the roving elongation is relatively stable and its fluctuation is small

2.2.2 spinning condition of suspension roving frame

because the center and upper and lower positions of the suspension roving frame are fixed, when the tension of the roving section is too large, it is impossible to have violent shaking of the roving section, such as that of the supporting roving frame during spinning. The reason why the roving in the spinning section of the suspension roving machine vibrates violently should be that the upper end face of the false twister at the upper end of the spindle is not in the same horizontal plane when it rotates, resulting in the change of the contact point between the roving and the false twister, which makes the roving in the spinning section vibrate violently, which belongs to the installation quality problem of the false twister. Therefore, it is difficult to distinguish whether the roving tension in the spinning section is large or appropriate from the position and state of the roving in the detection area. Of course, the roving elongation is different, but the elongation difference is not much different in theory, and should be relatively stable; The situation when the spinning tension is small is the same as the above. Using this principle, the position of roving is detected by CCD displacement sensor, and compared with the control position, the judgment of whether to adjust the bobbin speed is made, so as to ensure that the roving in the spinning section is in the required position area, and realize the stability of spinning tension and roving elongation. Theoretically, it is difficult to make a difference between too large spinning tension and relatively appropriate spinning tension, but it should be able to react to too small spinning tension

3 factors affecting roving tension

3.1 configuration number of CCD displacement roving tension detection device

due to the extremely limited configuration number of CCD displacement roving tension detection device, the detection data is poorly representative. Suppose that the average roving tension detected by CCD is x, and the average roving tension of the whole roving machine spindle is y. when the absolute value of (Y-X) is closer to 0, the CCD displacement roving tension detection device reflects the spinning situation of the whole roving machine more truly, and the roving tension control is more effective; When the absolute value of (Y-X) is very large, the error of CCD displacement roving tension detection device in reflecting the spinning situation of the whole roving machine is very large, that is, X cannot fully represent y, so it is inevitable that the roving tension system of the roving machine adjusts the roving tension unrealistically, which may cause the roving tension of most spindles of the whole roving machine to lose control. Since it includes a modern TPE manufacturer, the number of CCD is very important for roving tension detection. To achieve effective roving tension control, a considerable number of CCD displacement roving tension detection devices must be configured, otherwise there are still great limitations

3.2 the weight unevenness of feeding cooked sliver

the size of the weight unevenness of feeding cooked sliver or the quantitative variation coefficient of feeding cooked sliver determine the effectiveness of the data collected by the CCD displacement roving tension detection device. If the cooked sliver weight is uneven or the quantitative variation coefficient is small, the quantitative difference of roving whiskers is smaller. During twisting and winding, the roving tension can be smoothly reduced by the self-adjusting ability of winding tension and the self-adjusting ability of variable winding volume If the weight of the sliver is uneven or the quantitative coefficient of variation is too large, the absolute value of (Y-X) may be too large, which will make the tension control of the whole car roving out of control. Therefore, the key to give full play to the superior performance of the new generation of roving frame is to strictly control the weight of the sliver. In addition, the weight deviation will not affect the effectiveness of the tension device sampling

3.3 the long segment of the cooked sliver is seriously uneven

the long segment of the cooked sliver is seriously uneven, which will make the roving tension tight and loose. Due to the randomness of the long segment unevenness, the tension control of the whole roving frame will be relaxed when the roving at the detection spindle position becomes thicker, and tightened when the roving at the detection spindle position becomes thinner. At the same time, the winding diameter of each layer of the roving will be unstable, which may lead to the breakage of the roving and the deterioration of the roving winding structure. To ensure the stable and smooth implementation of the control of spinning tension, it is necessary to improve the positive coiling rate and the longitudinal uniformity of the cotton roll. A higher positive coiling rate and the longitudinal uniformity of the cotton roll are good, it is possible to achieve a lower sliver weight unevenness, sliver weight unevenness and long segment unevenness CV value. At the same time, it is necessary to strictly control the falling rate of the carding machine. In addition, the blowing carding unit is used, and the self leveling device is configured at the same time, so that the weight unevenness of sliver and the CV value of long segment are small

3.4 effect of false twister installation state on the stability of roving tension and elongation

the installation state of false twister is extremely important to the stability of roving tension and elongation. If the upper end face of the false twister at the upper end of the spindle does not rotate in the same horizontal plane, the position of the contact point between the roving and the false twister will change, causing the roving in the spinning section to vibrate violently, which is extremely detrimental to the control of roving elongation and its difference, especially at high speed. Therefore, it is necessary to strengthen the daily maintenance of the roving machine to make the installation state of the false twister have a better level

3.5 effect of the number of turns on the flyer pressing palm leaf of coarse yarn on the tension and elongation of roving and their differences

it is generally believed that if the number of turns of roving on the flyer pressing palm handle is large, the friction resistance of roving on the flyer pressing palm handle is large, resulting in an increase in the winding tension of roving winding section and a relative decrease in the winding diameter of winding package. At the same time, considering the extension of roving in the winding section, Make the speed of roving entering the spindle wing and pressing the palm petiole to the winding area slow down, and finally make the roving tension in the spinning section relatively reduce. On the contrary, if the number of turns of the roving on the spindle wing pressing palm petiole is less, the tension of the spinning section is relatively larger. In addition, the roving spinning tension has the ability of automatic adjustment. When the tension of the spinning section becomes larger, the spinning tension of the roving will not increase abruptly by increasing the elongation of the roving and reducing the winding diameter. Similarly, when the tension of the spinning section becomes small, the spinning tension of the roving can be reduced greatly by reducing the elongation of the roving and increasing the winding diameter, so as to ensure that the spinning tension of the roving changes smoothly. Therefore, in order to ensure that the roving tension detection system is more effective in controlling the roving tension and elongation, the roving tension of the whole car should still be adjusted by observation during the trial spinning to make it at a relatively appropriate level, so as to ensure that the roving tension detection system works in a relatively effective state, so that the roving tension, roving elongation and their differences are controlled within a relatively good range

4 conclusion

(1) in order to keep the roving tension relatively stable, a sufficient number of roving tension detection devices must be equipped to make the sampling signal of the roving machine spinning tension detection device representative. Otherwise, if the absolute value of (Y-X) is very large, the error of CCD displacement roving tension detection device in reflecting the spinning condition of the whole roving machine will be very large, that is, X cannot represent y, so it is inevitable that the roving tension system of the roving machine will adjust the roving tension unrealistically, which may cause the roving tension of most spindles of the whole roving machine to lose control

(2) in order to make the roving tension control system play its due role, the weight unevenness of the cooked sliver fed into the roving machine must be strictly controlled within a certain range

(3) the evenness CV value of roving should be small, which is very beneficial to roving winding and controlling the difference of roving elongation. Therefore, in the spinning process, self leveling devices should be equipped on the carding machine or drawing frame as far as possible

sample preparation (4) ensuring that the false twister is installed in a good state is the basis for controlling the difference in roving elongation

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