Renovation of cotton combing machine drafting system
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In recent years, the manufacturing technology of domestic cotton combing machines has progressed rapidly, and its operating speed has been greatly increased to 500 nip/min. The actual process speed is about 400 nip/min. At the same time, the failure rate of high-speed equipment has also increased significantly, affecting combing production efficiency. Among them, the failure rate of the drafting system has become one of the important issues affecting the efficiency and quality of cotton combing machines.
1 Cotton combing machine drafting system failure
1.1 Air leakage in drafting cylinder
The drafting rubber roller of the cotton combing machine adopts a stable pneumatic pressurization method, which can easily adjust the pressure. It has a dedicated pneumatic pressurization switch and a pressure release switch, which can be operated manually. Generally speaking, the pressure adjustment range on the drafting rubber roller is 491.0N ~ 687.4N. However, due to the high operating speed of the cotton combing machine and the high operating speed of the rubber roller, the air film in the rubber roller and cylinder is subject to The pressure increases accordingly. During long-term use, the air film ruptures and causes air leakage, causing the cylinder to fail to work normally. Insufficient drafting pressure of the rubber roller also causes the sliver to not be drafted, resulting in sliver dropping and sliver swelling problems, causing the sliver to be stretched. The thickness fluctuation is too large, which directly affects the quality of combed sliver, and the drafting system cannot operate normally. The six rubber roller pressurizing cylinders of the drafting system must be shut down and checked. If the air leakage is found in the cylinder, the air film must be replaced – this The complex process seriously affects combing production efficiency.
1.2 Drafting head rubber roller wrapping
When the running speed of the drafting head rubber roller is too high, the contact surface between the drafting head rubber roller and the cleaning piece is easy to accumulate lint. After long-term accumulation, it is easy to cause the drafting head rubber roller to become tangled. It may even occur due to too much lint on the drafting head rubber roller. stuck” problem.
This kind of problem of tangling of the drafting head rubber roller occurs more frequently, resulting in an increase in the tassel return rate, a reduction in equipment operation efficiency, an increase in the labor intensity of the lathe operator, and the processing of the tangling of the opposite rubber roller is troublesome and takes a long time to directly Affects the output of combed sliver.
2Renovation plan
2.1 Cylinder
2.1.1 Causes of cylinder air leakage
The cause of air leakage in the drafting cylinder is the rupture of the air film. Figure 1 shows the structure of the drafting cylinder, and Figure 2 shows the air film of the cylinder. The working principle of the drafting cylinder is to pressurize the gas, and the air film is deformed under pressure, pushing the piston head to relax. The position of the piston head in Figure 1 is the working position of the cylinder, and it remains in this state for a long time. The air film has two functions: one is to seal and fix, use screws to deform the O-ring at the upper end of the air film to fix and seal the cylinder head and the cylinder body to prevent air leakage in the cavity; the other is to pressurize the air and push the air film through deformation The piston head is relaxed, and the air film returns to its initial state after the pressure is relieved.
Long-term observation and statistics found that the location of the air film rupture is at the connection between the 3mm diameter O-ring and the air film thickness of 0.5mm. The main reason is that the deformation of the O-ring is usually unchanged after the seal is fixed, and the diameter is large and is not easy to be damaged. Although the air film thickness is relatively thin at 0.5mm, it is made of oil-resistant rubber material. , can fully withstand the pressure of 0.40MPa ~ 0.55MPa. During long-term use, the air film is pressurized and depressurized multiple times. The connection between the 3mm diameter O-ring and the air film thickness of 0.5mm has been in a strong and loose state, and it is easily connected to the inner wall of the cylinder. Friction at rounded corners will cause surface wear or cracks when the number of cycles is too many. In response to this problem, the author has adopted methods such as using better air film materials, thickening the air film, and completing the filleting of the inner wall of the cylinder to solve it, but there has been no substantial breakthrough, and the problem of air film rupture still exists.
2.1.2 Cylinder seal modification
The O-ring sealed cylinder is a standard cylinder type with long service life and the O-ring is not easily damaged; therefore, the O-ring sealed cylinder is used instead of the air film cylinder. The specific modification plan is as follows.
The structure of the cylinder head and piston head has been improved to enable the installation of O-rings, and then the O-ring 1 is installed in the middle of the piston head to form a seal with the inner wall of the cylinder body; use screws to deform the O-ring 2 to fix the sealed cylinder. cover and cylinder body to prevent air leakage in the cavity. The working principle of the modified cylinder is that gas directly pressurizes the piston head, pushing it to relax to the working position and maintain the state; after the pressure is relieved, the piston head is not subject to gas pressure, and rebounds through the pressure relief of the rubber roller, returning to the non-working state. s position.
2.2 rubber rollers
2.2.1 Reasons why the rubber roller is entangled
The cleaning device of the rubber roller of the drafting head of the raw cotton combing machine is only suitable for medium and low speed operation (200 clamps/min~320 clamps/min); its working principle is to place a soft plastic sheet for cleaning under the drafting rubber roller. The thrown flowers generated by the operation of the machine can be promptly and effectively blocked by the cleaning sheet, and then removed by the air suction device. However, when running at high speed, the floating fibers of the cotton sliver, that is, the thrown fibers, increase per unit time, and the floating fibers scraped off by the cleaning blade also increase. When the floating fibers accumulate to a certain extent, they will be accumulated under the cleaning blade, and the original suction The wind device cannot absorb these floating fibers in time and thoroughly, causing the friction between the floating fibers and the head rubber roller to increase, and the generated static electricity to increase, which can easily cause the cotton sliver to wrap around the head rubber roller; when the cotton sliver wraps around the head rubber roller to a certain extent When the combing machine drafting mechanism is wrappedThe winding auto-stop device works to stop the machine; when the speed is 400 clamps/min, the average length of the cotton web wound on the rubber roller using the new drafting mechanism auto-stop device is 1.7m. In this process, the weight of the sliver is affected, thereby affecting the quality of the sliver. At present, many domestic manufacturers use rubber rollers with excellent anti-winding and anti-static properties to reduce the frequency of such failures; however, the production cost has increased significantly, and the results under different cotton textile processes are not ideal.
2.2.2 Cleaning device modification
In order to solve the above problems, the original cleaning device is changed into an automatic cleaning device for the drafting head rubber roller, that is, a driving mechanism is installed on the drafting head rubber roller cleaning piece. When a large amount of floating fibers scraped off by the cleaning blade accumulate on the cleaning blade, under the action of the driving mechanism, the cleaning blade leaves the surface of the rubber roller at a certain height and shakes a certain number of times to shake off the scraped floating fibers and make them more durable. It is easy to be removed by the air suction device and solves the problem of tangled flowers on the rubber roller. The amount of expansion and contraction of the drive mechanism and the number of jitters can be set on the touch screen of the combing machine according to the requirements of different cotton textile processes.
Specific modification measures: One side of the rubber roller of the drafting head is equipped with a cleaning sheet for scraping away the floating fibers on the surface of the rubber roller, and the cleaning sheet expands, contracts and shakes under the action of the driving mechanism so as to appear or separate from the surface of the rubber roller. Or in the closed state; the driving mechanism is an electromagnet combination, including an electromagnet, a telescopic rod and a spring, and the spring is sleeved on the telescopic rod. At the same time, there is an air suction device on the side of the drafting head rubber roller. The air suction device has a section of extension tube, and the air inlet of the extension tube is close to the drafting head rubber roller and cleaning piece. Connect the connector 3 to the drafting wall with a pin. on the board, so that it can rotate around the pin, and the electromagnet coupling part is fixed on the air suction device; the cleaning piece coupling part is fixed on the connecting piece 3 with screws, and the connecting piece 1 is fixed on the cleaning piece with screws, and is connected with the connecting piece 2 are connected with pins and can rotate with each other, and the connecting piece 2 is connected with the end of the telescopic rod of the electromagnet binding member with pins. The connecting piece 3, the cleaning piece and the connecting piece 1 are fixed together as one rod in the crank slider mechanism, and the remaining three rods are connecting rods composed of the connecting piece 2, the electromagnet combining piece and two fixed points respectively.
When the electromagnet is not energized, the telescopic rod of the electromagnet coupling part stretches greatly under the action of its spring and gravity. At this time, the cleaning piece is just close to the surface of the rubber roller of the drafting head, and plays the role of scraping dust and cleaning the drafting head. The function of the rubber roller is shown in Figure 4a). When the electromagnet is energized, the telescopic rod of the electromagnet combination is quickly sucked back along the track. Driven by the telescopic rod, the cleaning piece is lifted to a height of about 5mm to 12mm and leaves the surface of the rubber roller of the drafting head, as shown in Figure 4b) shown. During this process, the floating fibers and impurities on the cleaning piece are removed close to the air suction port; when there are too many floating fibers and impurities accumulated on the cleaning piece and cannot be completely removed in time, the power can be turned on and off repeatedly to shake the cleaning The blade allows floating fibers and impurities to be shaken off, making it easy to be completely cleaned and removed. After the power is turned off, the working position of the cleaning blade is restored, as shown in Figure 4a).
The entire action of the automatic cleaner is realized through PLC and human-machine interface control, that is, the electromagnet is controlled to close at a certain time point to be determined. On the human-machine interface, set the cleaning blade scraping time, lifting time and shaking interval time to achieve cleaning operations in different processes and environments.
3 Production practice verification
The modified drafting system was tried out on a cotton combing machine, and the effect was very good; the drafting system was optimized and modified on multiple cotton combing machines in several fabric factories, and production practice showed that its use effect was better. To be significant.
3.1 Comparison of usage effects
Under the same conditions of machine, machine speed and process, a comparative test lasting 1a was conducted. After the transformation, there were no shutdown problems caused by air leakage in the drafting cylinder and entangled rubber rollers in the drafting head, and the operating efficiency of the entire vehicle was greatly improved.
3.2 User reviews
The new drafting cylinder has been running for more than 1 year, and no air leakage problem has been found. It has greatly reduced the maintenance workload, reduced the number of shutdowns, improved production efficiency, and steadily improved quality, and has been unanimously praised by users; the new type The use of the automatic cleaning device for the rubber rollers of the drafting head effectively solves the problem of downtime caused by the entanglement of the rubber rollers of the drafting head, reduces the labor intensity of the operator, effectively reduces the number of shutdowns, and greatly improves the efficiency of combing. The production efficiency of the machine has been recognized by users.
4Conclusion
The improvement of the drafting system of the cotton combing machine has been verified by many fabric factories for a long time. It shows that the improvement of the drafting system of the cotton combing machine has good effect, the faults are significantly reduced, the quality index of the combed sliver is good, and the quality index of the combed sliver is effectively improved. Improved combing production efficiency. This improvement plan can be widely used in cotton combing machines.
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