Abstract: The Swiss-made RSB series drawing frames feature a self-leveling system and sliver monitoring technology, and can automatically adjust the draft ratio online, resulting in excellent performance. Many RSB series drawing frames have been imported into China, significantly improving the quality of sliver and yarn. This article introduces the performance and usage of this type of drawing frame. Keywords : Transmission system, self-leveling, sliver detection technology, automatic online draft adjustment. The quality of sliver produced by drawing frames is crucial to the quality of yarn and fabric. In recent years, the RSB series self-leveling drawing frames developed by Rieter AG of Switzerland, along with their earlier models, the RSB951 imported to China in its early stages, and the RSB-D30 and RSB-D35 introduced since the late 20th century, have made significant progress in further improving sliver quality and have undergone substantial changes in processing technology. This article introduces the structural characteristics and usage of the RSB series self-leveling drawing frames. I. Structural Features The RSB series drawing frame uses a three-up, four-down roller drafting system (RSB951 uses a three-up, three-down roller drafting system). It has a simple structure, is easy to adjust, easy to clean and maintain, highly adaptable, and can process various types of fibers and spin slivers of various weights. The pressure bars maintain good control over the fibers during drafting in the main drafting zone, controlling short-segment weight deviations within a specific range. The RSB series drawing frame's drafting system is equipped with a negative pressure dust extraction device, ensuring the entire drafting area is under continuous negative pressure suction to reduce impurities and lint content in the sliver. This is a crucial technical measure for further processing high-quality pure cotton yarn in rotor spinning. Besides effectively removing impurities from the sliver, the negative pressure suction system also keeps the drafting working area of ​​the drawing frame clean. It is reported that the cleaning cycle of the RSB series drawing frame can be increased up to 10 times. 1. Drawing Frame Drive The RSB series drawing frame uses a flat belt drive instead of the traditional toothed belt drive. 1. Eliminates sliver errors caused by impurities accumulating on the belt, reducing noise. 2. Sliver Feeding Section: The sliver feeding section of the RSB series drawing frame consists of a feed frame and actively driven feed rollers. Using actively driven feed rollers for sliver feeding is advantageous for the self-leveling sizing system, especially when processing slivers with poor cohesion (such as combed slivers and fine slivers fed to air-jet spinning). The sliver feeding speed is very high, and the effect on the sizing system is even more beneficial under overload conditions. The machine also offers different frame and feed guide roller sizes to fully utilize workshop space for optimal arrangement. 3. Sliver and Ladle Structure: The sliver output from the drawing frame must have a tight and dense shape to prevent false drafting or fiber slippage in the next process. Therefore, the production of a dense and smooth sliver is required during the sliver forming process. Thus, the web guiding elements, sliver bundlers, and sliver channels (slanted tubes) are crucial to the structure and shape of the sliver. The dimensional design of the guide elements is particularly important for the production of fine slivers. In the RSB series draw frame, the sliver passage (skew tube) and coiler are made of stainless steel and are suitable for various types of fibers. 4. Leveling Mechanism of the Draw Frame The leveling mechanism designed on the draw frame is mainly to eliminate spinning weight deviations caused by the feeding sliver. There are many types of levelers, and in practical applications, the open-loop leveler is the most widely used. The open-loop leveler can control and correct minute weight deviations in the fed sliver. In the open-loop control system, a pair of grooves and spring rollers detect the thickest part of the sliver entering the feed roller and store the test value. Until the moment the measured part reaches the draft point of the main drafting zone, the draft ratio is changed instantaneously by a pneumatic servo motor. It is also necessary to detect extremely small deviations, such as the splice point of the combed sliver. The open-loop self-regulating leveler can detect large fiber bundles at relatively low movement speeds in the sliver feeding section. This precise testing method yields better results than the closed-loop leveling method that tests sliver size at the draw frame output. This is because the sliver linear velocity at the output is high, and the weight of the fiber bundle is significantly reduced after drafting. After leveling, the CV% values ​​for 1-meter, 3-meter, and 5-meter slivers reach 0.3%, 0.2%, and 0.1%, respectively, with weight deviations around 0.5%. Furthermore, the accuracy of using a high-power servo motor to directly adjust the draft ratio depends on the precise measurement of sliver weight deviation, which also relies on the error-free self-leveling results. On the RSB series draw frame, all passing slivers are continuously scanned by a detector at a distance of 1.5 mm and a detection frequency down to the millisecond level, leveling slivers within a ±25% range to within ±1%. The accuracy of weight deviation testing remains the same regardless of the sliver feed speed. Because the leveling system maintains a constant interval between sliver tests, the sliver length between test signals increases as the sliver speed increases. Therefore, the weight deviation of the sliver is related to the evenness process. When the RSB series drawing frame has an output speed of 800 m/min, the corresponding feed speed is 130 m/min, and the test signal distance is approximately 25 mm or 4 times the length. 5. Monitoring Technology for Sliver Thicknesses To avoid defective slivers, the sliver is continuously monitored at the output of the drawing frame, providing accurate actual operating data. The actual data is compared with normal values, and the machine automatically stops if any exceedance occurs. The monitor can monitor the following parameters: ① A% limit (Adjustable limit); The A% limit is set to +15% to +25% in 1000 meters of sliver. Below 15% has no significant impact on yarn quality, while 25% and above significantly affect yarn quality, triggering an automatic alarm and stopping the machine for further processing. ② Evenness CV% limit; ③ Spectral limit of typical periodic defects (these defects cause printing defects). The sliver monitor provides a condensed summary of production technology data, and the CV% value of the output sliver is displayed on the fluorescent screen. A brief report will be printed, including: the number of machine stops and stop times within 8 hours, the efficiency of the 8-hour operation, and the changes in the CV% value. The start and end times of machine operation and power failures will also be recorded. Detailed reports, including some information such as the current spectrogram and A% curve for the entire 8 hours, can be printed as needed. [b]II. Production Usage 1. Determining the Number of Output Heads[/b] Self-regulating levelers can operate on one or two output heads simultaneously. Levelers used to be more common on double-head drawing frames, but there has always been controversy regarding investment costs and floor space requirements. Currently, the application of any type of leveler on single-head drawing frames is increasing year by year. Currently, RSBD-30, RSB-D35, and RSB-D40 are all designed as single-head drawing frames. Practice has proven that the application of self-leveling slivers on single-head drawing frames has the following advantages: (1) Increases efficiency by 10%; (2) Is most suitable for automatic transport systems; (3) Is suitable for automatic connection of spinning production lines; (4) The structure of the self-leveling sliver is smaller and more streamlined, making it easier for operators and maintenance personnel to understand and master. 2. Self-leveling slivers in production lines Efficient self-leveling and good fiber control in the drafting system have formed the principle of placing them on the last drawing frame. The benefits of doing so are: (1) Sliver defects occurring between the first and last drawing frames can be corrected and compensated by the self-leveling device; (2) The doubling effect of the first drawing frame reduces the sliver weight deviation, thereby also reducing the workload of the self-leveling sliver. 3. Number of drawing frames In short fiber spinning, high-performance drawing frames and efficient self-leveling equipment can appropriately reduce the number of drawing frames. In carded ring spinning, two drawing frames are generally used, which is the standard arrangement in the spinning process. However, in combed spinning, due to Rieter's self-leveling technology, one drawing frame is widely used. Only in ring spinning for producing blended products is a three-drawing frame used to achieve uniform sliver blending. In rotor spinning, two drawing frames can be used to complete the blending task. In most cases, rotor spinning is used to produce coarse-count yarns. Especially when product quality requirements are not high, one drawing frame is sufficient. Denim yarn is an exception, as it requires high-strength, high-quality yarn, and usually uses two drawing frames to help remove impurities from the sliver during the drawing and drafting process. Compared to carded spinning, combed spinning uses one drawing frame to obtain better yarn quality because the high degree of straightening and parallelism between fibers in combed or high-count fine yarns is already achieved on the combing machine. Excessive drafting causes fibers to become too straight and parallel, reducing the cohesion of the sliver and increasing the likelihood of unexpected drafting errors. This can lead to separation in the production of coarse yarns and rotor-spun yarns due to poor cohesion. For these reasons, using a drawing frame is appropriate and feasible. III. Summary 1. The Swiss RSB series drawing frames are equipped with an open-loop self-regulating leveler. Under fiber speed conditions, it can detect larger fiber bundles with high sensitivity, providing better detection results than closed-loop high-speed extraction. 2. The test data shows that, in addition to improved yarn evenness, the most significant improvements are in the ideal CV% weight unevenness per 100 meters and weight deviation. The yarn weight unevenness is 1.8%, and the weight deviation per 100 meters is only 0.3%, which is unmatched by other drawing frames. 3. It saves a significant amount of sampling and testing work for controlling weight unevenness and deviation. With the self-adjusting leveling device controlling the drawing frame itself, weight deviation and unevenness are automatically controlled online. Essentially, manual adjustment and checking of the self-adjusting leveling range of the drawing frame only needs to be done once a day or per shift. This eliminates the need for offline sampling tests of sliver weight in the laboratory and the frequent, ineffective work of changing teeth. 4. Because the drawing frame itself is equipped with a monitoring device for the feeding and output sliver, if the weight or evenness of the fed sliver exceeds the limits, the machine will automatically stop and display a report awaiting further processing. Therefore, sliver quality is effectively guaranteed and controlled. 5. The RSB drawing frame with its self-adjusting leveling device serves as the final drawing, while a new domestic drawing frame serves as the first drawing. They complement each other. The semi-finished sliver from the first drawing reduces the leveling burden on the final drawing, and problems in the first drawing can be compensated for by the self-adjusting leveling of the final drawing. 6. To fully utilize the superior performance of the RSB drawing frame, high-performance equipment must be selected for both the upstream and downstream processes. Newly built spinning workshops generally pay attention to this, employing carding systems such as the DK760, DK803, DK903, TC-03C51, and C60 before the RSB drawing frame, and importing Qingze 660 and 670 roving frames. The combing machines, ring spinning machines, and drawing frames are all domestically produced new equipment, ensuring high-quality semi-finished sliver fed to the RSB drawing frame and guaranteeing the quality of yarn in downstream processes, thus effectively utilizing the self-leveling drawing frame. 7. To complement new spinning machines, the new drawing frame uses rectangular sliver cans, increasing sliver capacity by over 40%. It is anticipated that in the future, traditional spinning systems may also change the sliver cans supplied to roving frames to rectangular shapes. In conclusion, the Swiss-made RSB series drawing frame is a high-tech piece of equipment with advantages such as automatic open-loop sliver leveling, online sliver monitoring, and automatic online adjustment of draft ratio. It can serve as a reference for the research and development of drawing frame machinery in China. Based on the technology of the Swiss RSB drawing frame, China has accelerated its research and development, and has already manufactured domestically produced high-tech single-eye drawing frames for the market.