The precise length determination of the roving machine can greatly improve the work efficiency of the spinning and doffing workers to collectively change the roving, and reduce the need for the doffing workers to patch up and deal with the remaining roving yarn due to the large difference in the remaining length of each bobbin after the spinning is unwound. It reduces labor intensity, effectively improves product manufacturing rate and reduces production costs.
Because these potential advantages can bring tangible economic benefits, the precision of roving frames has increased in recent years. Determining long-term technology has received widespread attention.
01 Actual length of doffing
Ideal roving length The standard is that the roving doffing length is consistent with the set length, and after the spinning process is unwound, the remaining length difference of each roving sliver is very small (should be controlled within the range of 30 m). After production practice, we analyzed the impact of actual roving doffing length, roving elongation, high-efficiency false twister and temperature and humidity control on the precise length determination of the roving frame, and proposed countermeasures.
The roving doffing length is consistent with the theoretical length, which is very important to ensure the accurate length determination of the roving frame. Nowadays, the new domestic computerized roving frames are roughly divided into two situations: one is that the HY492A, B, and C roving frames are designed with a program function of automatically changing direction to find the doffing parking position when the yarn is almost full (about to reach the designed fixed length), which belongs to The doffing length is accurately determined; the other type of computerized roving frame, HY491 and HY492, is not a doffing length-determined type. The actual doffing length of the roving frame often depends on the temperature and humidity of the workshop, spinning tension, and false twist. Fluctuations occur due to changes in the twisting effect of the machine and the weight of the roving sliver, requiring technicians to adjust parameters such as forming length, parking position, and winding density in a timely manner.
The setting procedure of non-computerized roving frames is often that after the length gauge reaches the preset length, if it is not at the doffing position, the bottom rib must continue to rise to the middle doffing position. The doffing procedure can be carried out after the position is reached, which will cause an error of 1 m to 100 m.
By implementing the technical innovation of partial full yarn doffing, the non-computerized roving frame can meet the requirements of doffing as long as the yarn reaches the preset length when the rib is rising or falling. Position for doffing. It is best for roving manufacturers to cancel the control of the forming cone wheel transmission device, use microelectronic control technology, frequency conversion speed regulation technology, and input setting operations through touch screens to achieve better production results.
At the same time, the workers in the roving workshop should establish the idea of serving the next process, carefully and truly keep records, and resolutely put an end to forcibly doffing in advance before the set length is reached. Or the delay exceeds the set length and the phenomenon of doffing occurs.
When the spun yarn is modified or the same variety is expanded for loading, semi-roving yarn needs to be spun for spun yarn loading. The roving stopper must have a high sense of responsibility and carefully do the fixed-length doffing of semi-roving to ensure the accuracy of the semi-roving fixed-length and reduce the fluctuations in table differences and row-length fixed lengths.
Maintenance personnel should also make timely adjustments based on the actual length changes recorded in the doffing records, so that the doffing length of the HY491 and HY192 roving frames is controlled within the range of 2 m, and the ASFA411 machine Control within 5m.
Due to car repairs and other factors, it is necessary to drop the roving in advance, the quality department’s test work uses roving for experiments, and the remaining roving for joints after wiping the car is different from the set long roving length. Larger, they are all used as yarn handles on the spinning machine table. All these require the shift leader to hand over the operations of the roving process and the spinning process.
02 Controlling roving elongation
Roving elongation is an important indicator that indirectly reflects the tension of roving. It will affect the precise length determination of the roving frame in many aspects. Roving elongation is usually expressed as the ratio of the difference between the actual length of the winding on the bobbin and the calculated length output by the front roller nip to the calculated length output by the front roller nip at the same time.
It has a great influence on the evenness unevenness, weight unevenness and end-breakage rate of roving and spun yarns. Therefore, regular testing of roving elongation can provide a timely understanding of the trend of roving tension changes and make corresponding adjustments. According to the actual elongation measured in the test, we can optimize and rationally configure each winding tension parameter to reduce the elongation difference between large and small spindles, front and rear rows, and tables.
For doffing precision length-determining machines, the test data of roving elongation can be input directly on the touch screen. If it is not a machine with a certain length of doffing warp, it can be measured by the roving elongation test method.
Because the front roller rotates quickly and the opening and closing time is difficult to grasp, the calculated length of the front roller jaw output is based on the measured number of revolutions of the rear roller, and then based on Calculate the mechanical reach ratio.
In production, we can also use the average weight difference rate of large and small yarns measured by the weighing method to indirectly and quickly reflect the elongation difference rate of large and small yarns. The weight difference rate is expressed as the percentage of the difference between the average weight of small yarns and the average weight of large yarns to the average weight of large yarns.
To control the elongation of roving, we must first ensure that the cohesion between the fibers of the roving is the same. This is very important to maintain stable production, improve yarn quality, and control the consistency of the remaining yarn sliver after the roving is unwound.
We generally require that the difference rate should not be greater than 0.5%.��In terms of differential control of elongation, the elongation of the front row of rovings with unequal height flyers (equal yarn guide angles) is slightly greater than that of the rear row. The slivers of the front row of cans behind the machine can be matched to the front row of rovings. On the spindle flyer, the slivers of the rear row of cans correspond to the rear row of spindle flyers, so that the tension of the front and rear rows of slivers behind the machine and the front and rear rows of spinning tension in front of the machine can complement each other. For equal-height flyers (different yarn guide angles), false twisters with different false twisting effects in the front and rear rows can be used to reduce the difference in elongation of the rovings in the front and rear rows.
03 Preferred false twister
The actual doffing length of non-precisely determined computerized roving frames fluctuates mainly with changes in the temperature and humidity of the workshop, the false twisting effect of the false twister, and the weight of the roving sliver.
The high-efficiency false twister optimized through experiments can improve the false twisting effect of the roving sliver, and the fluctuation of the roving elongation can be effectively controlled. The false twisting effect of the false twister also plays a great role in reducing and stabilizing the roving elongation and its difference. The false twisting effect of the false twister is mainly related to the type of fiber being spun, the roving quantity, the material, specifications and shape of the false twister.
Tests show that a false twister with poor false twisting effect will reduce the strength of the roving, cause the roving sliver to sag, increase the elongation, and worsen the evenness; on the contrary, in Under the effect of good false twist effect, the roving is tensioned and its elongation is also effectively controlled.
After many roving elongation tests, we found that: when the new cotton roving frame adopts four-roller drafting and uses a high-efficiency false twister, under a certain Using a larger winding tension within the range will not increase the elongation; on the contrary, the false twisting effect will increase due to the increase in winding tension, and the untwisted triangle area at the nip of the front roller, which is most prone to accidental elongation, will be reduced.
When the roving spinning section is basically straight and the jitter is small, the twist of the roving in the spinning section increases. It seems that the spinning tension is very high, but due to the use of large tension to tighten the winding The winding spinning process actually does not increase the elongation of the roving, and can give full play to the effectiveness of the high-efficiency false twister and achieve the effect of increasing the winding density.
If a smaller spinning tension is used, some roving slivers will float. At this time, the false twister has completely lost the false twisting effect and the roving will elongate. On the contrary, the rate is higher. After long-term use of the false twister, the sharpness of the tooth shape will be reduced and the false twisting effect will be reduced. However, the new false twister generally has better false twisting effect and the elongation can also be effectively controlled.
Therefore, false twisters of the same specification should be replaced regularly and old false twisters are not allowed to be mixed on the same machine.
When the temperature and humidity in the workshop change greatly, it will affect the moisture regain of the raw materials, causing the friction coefficient of the roving channel of the whole machine to change.
This has a greater impact on the spinning tension and roving elongation of the roving. Since the working environment of the textile factory changes with the weather, sometimes the differences in temperature and humidity during the day shift, middle shift and night shift will cause changes in the roving elongation.
The 432 spindles (or 444 spindles) of the short spinning car and the 1104 spindles of the long car are replaced by two and three sections respectively, which requires that each roving frame doffing is done well. Time mark to ensure that the difference in elongation of the rovings replaced in each period is minimal. </p
