The main function of the draw frame is to combine and draft the card slivers spun by different carding machines to reduce the external unevenness of the card sliver. However, during the drafting process of the draw frame, chimney-shaped mechanical waves will appear due to various reasons and cause major quality accidents. Therefore, eliminating the generation of harmful mechanical waves in the draw frame has become an important research topic for every cotton spinning enterprise. This article starts from several aspects such as replacing concave and convex rollers and coiling parts, changing process gears and draft multiples, and overhauling transmission roller gears to eliminate harmful mechanical waves in the draw frame.
01 Replace the concave and convex roller and coil components
Eliminate mechanical waves above 2.6 m and about 20 cm
Our company uses FA322 draw frame with USG type autolevelling device. Through years of experience Production practice has found that convex and concave rollers, coil tension, pressure rods, etc. can cause typical drawing mechanical waves.
The circumferential surface of the concave and convex rollers is stuck, embedded, damaged, incorrectly installed, and has gaps or looseness in the shaft, etc., which will cause periodic uneven thickness of the yarn. When the bearings on the concave and convex roller shafts are severely worn due to lack of oil and other reasons, and the clearance is too large, not only mechanical waves will be generated, but also the displacement error signal detected by the displacement sensor will be too large, and an alarm will be generated when the A·S% monitoring limit is exceeded. . In actual production, the 6305 bearing in the convex roller shaft part is damaged. When the A·S% alarm occurs, multi-column mechanical waves such as 2.6 m, 4 m, and 8 m will appear.
The coiling tension is the tension on the output bar caused by the centrifugal force generated by the high-speed rotation of the coiling disc. Its function is to make the sliver straight and smoothly formed. Mechanical waves can be generated by wear and looseness of some parts of the coil transmission. For example, pulley L generates mechanical waves of 18 cm to 19 cm due to wear and looseness of the keyway. When the main motor flat belt has one or more defects, the pulley rotation will be unstable. The flat belt rotates once, causing one or more sudden changes in the coiling tension between the coiling disc and the front pressure roller, thereby generating mechanical waves.
The pressure rod is placed in the main drafting area as an additional part, which can make the whiskers generate a surrounding arc on the surface of the pressure rod and strengthen the friction boundary in the middle of the main drafting zone. , enhance the control of floating fiber movement, make the friction boundary in the main drafting area extend forward to the jaw, move the fiber speed change point forward and concentrate, reduce the displacement deviation after drafting, and improve the quality of the yarn after drafting . However, when the sliver does not pass through the normal channel, the friction boundary effect is weakened, the floating zone becomes longer, and the control of the floating fiber is weakened. The fiber is easy to change speed in advance and the speed change points are dispersed. The shift distance deviation after drafting increases, and the yarn sliver Additional unevenness increases, forming drafting waves. If the operation is improper, the front draft wave will be generated when the sliver passes over the pressure rod.
02 Change the process gear and draft ratio
Eliminate the 5cm mechanical wave of the draw frame
In order to solve the problem of 5 cm mechanical waves in the FA326 draw frame, tests and investigations were conducted from both the equipment and process aspects. Starting from the process gears, draft multiples, etc., the M gear was changed from 47 The teeth were changed to 49 teeth, and the N gear was changed from 24 teeth to 28 teeth, thereby eliminating mechanical waves. Theoretically, changing the front tension gear reduces the tension draft between the pressure roller and the front roller; strengthening equipment maintenance and improvement and tracking of the process can effectively improve uneven roving and eliminate roving and drawing. Mechanical waves effectively improve yarn quality.
Starting from aspects such as process gears and draft ratio distribution, the M gear was finally changed from 47 teeth to 49 teeth, and the N gear was changed from 24 teeth to 26 teeth, that is, the pressure roller The draft tension to the front roller decreases, and the draft ratio in the rear area increases from 1.2 to 1.3. After the adjustment of the front tension gear, the cohesion between fibers has been significantly improved, which solves the problem of overcooked and rotten slivers and is beneficial to the improvement of roving slivers.
After the adjustment, the wave spectrum on the display screen of the draw frame immediately changed, and the mechanical wave of about 5 cm disappeared. Although the CV value of the cooked sliver remains at about 1.9%, and the mechanical wave disappears 10 cm in front of the spectrum, the fixed drum and spindle tracking tests were carried out on the roving frame, and the CV value of the roving changed from the original 4.01% to 3.68%. The data changes show that the measures are taken properly, and the roving spectrum shows that the mechanical waves are gone. This is very beneficial to improving the evenness CV and mechanical waves in subsequent processes and improving the quality of the yarn.
After taking the above measures, the mechanical wave front and back-spun CJ 7.3 tex yarns were eliminated. The average quality index of 20 packages spun by the corresponding winding machine. It can be seen that after the process gear replacement, the quality indicators of the yarn have improved.
03 Repair the transmission roller gears and bearings
Eliminate the 13cm~15cm mechanical wave of the draw frame
When our company used a capacitive evenness analyzer for daily quality inspection, it was found that obvious mechanical waves appeared in the spectra of two varieties of multi-tube spun yarns. The mechanical waves were analyzed. And processing based on analysis eliminates mechanical waves and stabilizes product quality.
The types of mechanical waves found are CJ 14.6 tex woven yarn and CJ 27.8 tex knitting yarn, which are supplied by a roving frame. Since mechanical waves appeared in both varieties at the same time, and the wavelength of the mechanical waves was larger, the possibility of the spinning process can be ruled out, and the preliminary diagnosis was that the defective parts were in the drawing process.
Check the gears and bearings that drive the first roller, and found that the first roller shaft head gear 28T gear has…The �� tooth is broken. Since no abnormality was found in the daily quality inspection the day before, it is speculated that there are scars inside the gear, and a sudden tooth explosion occurred after long-term transmission. Replace the 28T gear, and inspect and inspect the adjacent gears and bearings. Refuel, drive again and check, the mechanical wave disappears on the spectrum.
It can be seen that the draw wavelength calculated from the CJ 14.6 tex spun yarn spectrum and the actual draw wavelength are slightly different, while the draw calculated from the CJ 27.8 tex spun yarn spectrum The wavelength is almost equal to the actual wavelength. This may be caused by the different draft ratios of the two varieties in the spinning process. The draft ratio of CJ 14.6 tex is large, and the farther back the mechanical wave wavelength on the spun yarn spectrum is, the less accurate it is. We found that the draw frame wavelength calculated from the CJ 14.6 tex spinning yarn spectrum is slightly different from the actual draw frame wavelength, while the draw frame wavelength calculated from the CJ 27.8 tex spinning yarn spectrum is almost equal to the actual draw frame wavelength.
This may be caused by the different draft ratios of the two varieties in the spinning process. It can also be seen from the spectrogram that the span of the three parallel columnar mechanical waves is about 25 m to 35 m, with an average value of 30 m, which is the wavelength value of the highest columnar mechanical wave; and the viscosity coefficient of the woven yarn is large, forming Wavelength is even less obvious. In comparison, the draft ratio of CJ 27.8 tex yarn is small, and the mechanical wave wavelength on the spectrum is very clear. Based on this, the draw frame wavelength calculated based on this is relatively reliable.
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