Application of CNC Lathe in Multilevel Throttle Valve Processing of Control Valve
**Abstract:** This paper presents the calculation of the machining program and the challenges encountered during the programming process when manufacturing multi-stage throttle stems for control valves using a CNC lathe. With the rapid development of numerical control technology in recent years, CNC machine tools have become widely used in the machinery manufacturing industry. Their ability to perform multi-axis linkage enables the machining of complex curves and surfaces that are difficult or impossible to achieve with conventional machines. The multi-stage throttling control valve produced by our company enjoys a significant market share due to its stable performance and precise regulation. However, the complexity of the multi-stage throttle stem makes it challenging to machine. Traditionally, single-board lathes were used, which required extensive manual programming with binary code, leading to high workload, errors, and difficulty in modifying parameters. By contrast, CNC lathe programming allows for quick and accurate preparation of machining programs, ensuring high precision and efficiency. This article takes the CK0620 CNC lathe (a two-axis system with dual 8031 as the main controller) as an example to illustrate the steps involved in programming a multi-stage throttle valve. The data for the throttle shape line is provided in Table 1, where H represents the travel distance, and X and Z represent the coordinates along the radial and axial directions, respectively. To simplify programming, incremental coordinates are used, with U representing the X-axis increment and W the Z-axis increment. After calculating the machining coordinates based on the given data, Table 2 shows the corresponding U and W values. It is important to ensure that each relative coordinate change remains small to maintain smooth surface finish after machining. The program for the multi-stage throttle stem follows a similar structure, but the first stage involves an arc transition, while the subsequent stages may differ slightly. These differences are handled separately, and the loop instruction G22 LXXXX...G80 is used to repeat the processing of specific sections. The program starts at the first level of the throttle arc R20, with an initial offset of 5mm from the starting point. The detailed programming sequence includes commands such as G00, G01, G02, and G03, with appropriate feed rates and tool movements. The use of cycle instructions significantly reduces program length, improves readability, and minimizes errors. Adjustments in the program are made based on measured results during fine-tuning to ensure compliance with tolerance requirements. Additionally, the direction of the arc commands (G02 and G03) differs from standard systems like FANUC and SIEMENS, requiring careful configuration. The program can be repeated multiple times to gradually approach the desired dimensions, completing both rough and finish machining. In conclusion, CNC lathe machining of multi-stage throttle stems improves positioning accuracy, repeatability, and overall part quality. It also reduces human error and enhances productivity by maintaining consistent feed rates even for complex shapes, thereby improving efficiency and reducing costs. The method ensures that the valve meets design specifications and performs reliably in real-world applications.
**References**
[1] Liu Xiongwei. *Numerical Control Machine Tool Operation and Programming Training Course* [M]. Beijing: Mechanical Industry Press, 2003.
[2] Dai Shu. *Metal Cutting Machine* [M]. Beijing: Mechanical Industry Press, 2001.
[3] Fang Yi. *CNC Machine Tool Programming and Operation* [M]. Beijing: National Defense Industry Press, 1999.
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