With the development of market globalization, the market demand for manufacturing systems suitable for small-batch processing, with good flexibility and multi-functionality, has exceeded the demand for large-scale, single-function manufacturing systems, thus requiring manufacturing to have strong market responsiveness. This trend has led to the emergence of a new concept: modular, reconfigurable, and expandable software and hardware systems, also known as open CNC systems. This system can not only quickly and economically adapt to new processing needs, but also provides manufacturers with the possibility of integrating their technology or products with third-party technologies or products. Currently, countries around the world are committed to researching open CNC systems, such as OSACA in Europe, OMAC in the United States, and OSEC in Japan. The concept of openness in CNC systems emerged in the late 1980s and early 1990s, proposed by European and American countries to adapt to new changes in the machine tool manufacturing industry in terms of technology, market, and production organization. According to the IEEE definition, an open control system should provide the ability to fully implement applications running on various platforms of different vendors on the system, interact with other system applications, and have a consistent user interface. Therefore, an open system refers to a CNC system that can run on multiple different platforms, interoperate with applications from other systems, and provide users with a consistent style of interaction. In other words, it introduces the openness of a PC into a CNC machine tool. According to this definition, an open CNC system is a modular architecture with both open interfaces and open functionality. It should possess the following characteristics: Openness: Providing a standardized platform environment that allows software and hardware modules from different developers and with different functions to integrate. Interoperability: By providing standardized interfaces, communication, and interaction mechanisms, different functional modules and standard application programming interfaces can run on the system platform and achieve equal interoperability and coordinated operation. Portability: The system's functional software is device-independent, meaning it uses a unified data format, interaction model, and control mechanism, allowing the various functional modules that make up the system to originate from hardware platforms provided by different developers. Scalability: The system's functions and modules can be flexibly configured and easily modified. Hardware or software can be added to create a more powerful system, or its functionality can be reduced to suit lower-end applications. Interchangeability: Functional modules with different functions and reliability can be substituted for each other without affecting the coordinated operation of the system. How to make traditional dedicated, closed systems more open? Different system developers and research institutions have proposed several solutions. These can be divided into three approaches based on the level of openness, with varying levels of openness, difficulty, and the resulting openness effects. One approach allows users to construct or integrate their own modules into the human-machine interface. This method provides users with a flexible way to customize operating interfaces and procedures to suit their specific requirements, and is generally used in systems based on PCs as graphical human-machine interfaces. Another approach, in addition to the openness of the above methods, allows users to add their own special modules to the control core module. Through the open system's core interface, users can add their unique control software modules to the pre-reserved kernel interface according to certain specifications. The open architecture solution is a more thorough approach. It attempts to provide comprehensive openness from software to hardware, from the human-machine interface to the underlying kernel. Guided by open architecture standards and a series of specifications, people can configure as needed a complete system with varying levels of functionality, performance, and price, without relying on a single vendor. In terms of specific structural implementation, PC-based open CNC systems can be divided into four types: NC-connected type; PC-embedded NC type; NC-embedded PC type; and fully software type. The following discussion focuses on the NC-embedded PC type open CNC system. The performance of the PC-embedded system is primarily determined by the motion control card. The main solutions for constructing the motion control card include three types: microcontroller-based, dedicated control chip-based, and digital signal processor (DSP)-based. DSP-based motion control cards can implement complex control algorithms and functions. Compared with the previous two types of motion controllers, it has the advantages of high DSP processing speed and the ease of implementing an open structure on the PC platform. It is a new type of motion control card with high precision, high speed, multi-axis linkage, small size, and high integration, which can meet the requirements of high-performance control systems such as multi-axis CNC machine tools. Building an open CNC system hardware platform based on a PC and motion control card is convenient and quick. Because motion control cards are standardized and modular products, users or manufacturers only need to select appropriate PCs, motion control cards, and execution unit modules according to specific requirements, and connect the hardware system to quickly complete the hardware platform construction of an open CNC system. Its structure is shown in Figure 2. In the NC embedded PC-type open CNC system structure, a motion control card with processing capabilities is used. The computer system CPU can utilize the computer's rich software resources to focus on weak real-time and non-real-time tasks such as human-machine interface, input/output, preprocessing, and command sending; real-time tasks such as compensation processing, speed control, and position control can be implemented by the DSP processor on the motion control card without occupying the computer's resources. Based on the requirements of the CNC system and referring to the Windows 2000 operating system architecture, Visual C++ is used as the development tool. The software system architecture of the CNC system based on this is shown in Figure 3. Open CNC systems are an inevitable trend in the development of CNC technology. PC-based open CNC systems offer strong flexibility. In open CNC systems built by combining motion control cards with PCs, the motion control card performs real-time tasks such as interpolation calculations, position control, and speed control, while the PC provides a user-friendly human-machine interface, flexible system configuration, and enhanced external software interfaces. Simultaneously, it can fully utilize the rich hardware and software resources of PCs to develop high-performance, intelligent, open, and networked CNC systems, further adapting to the requirements of high efficiency and high automation. (References: You Youpeng, Dong Weijie, Zhang Xiaofeng, Wang Min. Open CNC System—The Mainstream of the New Generation of NC [Z]. Special Article on Advanced Manufacturing Technology at the 1999 China International Machine Tool Exhibition. Zhao Chunhong, Qin Xiansheng, Tang Hong. Research on PC-based Open CNC System [J]. Mechanical Science and Technology. Han Quanli. Open CNC System [J]. Mechanical Design and Manufacturing Engineering. Zhang Jian, Yin Sumin. Development of Open CNC System Based on Motion Control Card [J]. Machine Tool and Hydraulics. Guo Changwang, Zhu Guoli, Gong Shihua, Duan Zhengcheng.) Research on Open CNC System Based on Component Technology [J]. Journal of Huazhong University of Science and Technology. Click here to download materials : PC-based Open CNC System. Editor: He Shiping