Abstract : This paper discusses the basic principles of open CNC systems and their characteristics such as compatibility, interchangeability, portability, and scalability. The basic principle of the closed-loop CNC system for the CJK6132A lathe using a stepper motor as the servo motor—an improved time-division method—is introduced. The improved time-division method makes the implementation of a closed-loop CNC system using a stepper motor as the drive motor easier. The implementation of open CNC systems is studied: the openness of the system is achieved by formulating standards and protocols; a hierarchical modular design of the open CNC system is implemented: physical layer and software layer design. The characteristics and openness of the CIK6132A lathe closed-loop CNC system are introduced. This system has good compatibility and scalability, and low cost. Keywords : Open CNC system; OOP; Time-division method Since the 1990s, a new generation of open CNC systems based on PCs has emerged. Traditional closed-loop dedicated systems lack a strong architectural support, cannot perform reliable software expansion, and cannot meet the needs of user secondary development. Therefore, to adapt to personalized requirements such as CNC networking capabilities, creating a new, powerful, and open architecture is an inevitable trend in CNC development. In response to the challenges faced by CNC and the inevitable trend of open CNC development, some developed countries have launched their own open architecture specifications with the goal of designing and producing open CNC systems, such as the US NGC and OMAC programs, the EU's OSACA program, and Japan's OSEC program. In recent years, many domestic universities have conducted extensive research in the field of PC-based next-generation open CNC systems and achieved significant progress, but none have yet possessed the essential characteristics of an open CNC system. The architectures adopted by different systems are inconsistent, the platform issue of open CNC systems has not been resolved, and there is a lack of compatibility and interchangeability between them. To improve teaching and production practice, the Metalworking Practice Center of Sichuan University conducted closed-loop CNC retrofitting on a CJK6132A lathe and carried out extensive research on open CNC systems, achieving fruitful results. [b][align=center]For details, please click: Research on the Closed-Loop CNC System and its Openness of the CJK6132A Lathe[/align][/b]