1. Introduction Numerical control (NC) systems and related automation products are mainly used to support CNC machine tools. CNC machine tools are mechatronic products formed by the penetration of new technologies, represented by CNC systems, into the traditional machinery manufacturing industry. Machine tools equipped with CNC systems greatly improve the accuracy, speed, and efficiency of parts processing. These CNC machine tools are one of the important material foundations for national industrial modernization. The concept of numerical control (NC) is to convert the requirements of the machined mechanical parts, such as shape and size, into numerical data command signals and transmit them to an electronic control device. This device then controls the movement of the machine tool cutting tool to process the parts. In traditional manual machining, these processes all require manual operation of the machine, making it difficult to meet the processing requirements of complex parts, especially for multi-variety, small-batch parts, resulting in low processing efficiency and poor accuracy. In 1952, MIT and Parsons Corporation collaborated to invent the world's first three-axis CNC milling machine. The control device consisted of more than 2,000 electron tubes and was about the size of an average laboratory. The servo mechanism uses a small servo motor to change the swashplate angle of the hydraulic motor to control the speed of the hydraulic motor. Its interpolation device uses a pulse multiplier. The successful development of this NC machine tool marked the beginning of NC technology and a new era of numerical control in mechanical manufacturing. Modern CNC systems have greatly improved functionality and performance, with a failure rate reduced to 0.01 times/(month·unit). For example, the FS15 system developed by FANUC in 1991 was only one-tenth the size of the FS220 system developed in 1971. 2. CNC Standards The introduction of CNC standards, as NC becomes an important piece of equipment in automated machining, necessitates unified terminology, technical requirements, symbols, and graphics for both management and operation—that is, unified standards—to facilitate global technical exchange and trade. The development of NC technology has led to several internationally recognized standards: namely, ISO (International Organization for Standardization) standards, IEC (International Electrotechnical Commission) standards, and EIA (Electronic Industries Association) standards. The earliest standards included coordinate axes and motion directions for NC machine tools, coded characters for NC machine tools, program segment formats for NC machine tools, preparatory and auxiliary functions, dimensions of CNC paper tapes, and CNC terminology. The establishment of these standards played a normative and driving role in the development of NC technology. Recently, based on user needs and predictions for information technology in the next five years, ISO is developing a new standard, "Data Structures for CNC Controllers." It focuses the content of AMT (Advanced Manufacturing Technology) on two main levels and the connections between them: Level 1, CAM, for the workshop and its production machinery; Level 2, the higher level, for the data generation system, consisting of CAD, CAP, CAE, and NC programming systems and related databases. 3. Development of Servo Technology Servo devices are an important component of CNC systems. In the early 1950s, the world's first NC machine tool used hydraulic drive for its feed. Because the force generated per unit area in a hydraulic system is greater than that generated by an electrical system (approximately 20:1), with lower inertia and faster response, many NC systems at that time used hydraulic systems for their feed servos. In the early 1970s, due to the oil crisis, coupled with the environmental pollution caused by hydraulic systems and their bulky and inefficient nature, the American company Gettys developed a DC high-inertia servo motor. This motor boasted high static torque and starting torque, and excellent performance. FANUC quickly introduced it in 1974 and applied it to NC machine tools. From then on, open-loop systems were gradually replaced by closed-loop systems, and hydraulic servo systems were gradually replaced by electric servo systems. The early stage of electric servo technology was analog control, which was noisy and prone to drift. With the adoption of microprocessors, digital control was introduced. It has the following advantages: ① No temperature drift, good stability. ② High accuracy based on numerical calculation. ③ Reduced adjustments through parameter settings. ④ Easy to implement as an ASIC circuit. The greatest breakthrough in servo technology for modern CNC systems can be summarized as: AC drive replacing DC drive, digital control replacing analog control, or software control replacing hardware control. In the 1990s, many companies also developed linear motors driven by fully digital servos, which have high rigidity and good frequency response, thus achieving high speeds. 4. Adoption of Automatic Programming There are two methods of programming: manual programming and automatic programming. Statistical analysis shows that, using manual programming, the programming time to machine tool processing time for a single part is approximately 30:1 on average. To improve efficiency, computers or programming machines must be used to replace manual programming. Automatic programming requires an automated programming language, among which the APT language developed by MIT is the most typical CNC language, significantly improving programming efficiency. Image-based CNC programming technology, which emerged in the 1970s, effectively solved problems related to geometric modeling, displaying part geometry, interactive design, modification, toolpath generation, simulation display of the tool path, and verification, thus promoting the integration of CAD and CAM. 5. Introduction and Development of the DNC Concept The DNC concept has evolved from "direct numerical control" to "distributed numerical control," and its connotation has also changed. "Distributed numerical control" indicates that one computer can control multiple CNC machine tools. This expands machining from a single-machine automated model to flexible production lines and computer-integrated manufacturing systems. In terms of communication, a DNC interface can be added to the CNC system to form a manufacturing communication network. The most significant characteristic of a network is resource sharing. Through DNC functionality, a network can achieve: ① Uploading or downloading part programs. ② Reading and writing CNC data. ③ Transmitting PLC data. ④ Memory operation control. ⑤ System status acquisition and remote control, etc. 6. Adoption of Programmable Logic Controllers Before the 1970s, NC controllers and machine tool power sequence control mainly relied on relays. Semiconductor logic elements appeared in the 1960s, and in 1969, DEC in the United States developed the world's first programmable logic controller (PLC). PLCs quickly demonstrated their superiority: their graphical design is similar to relay circuits, making them intuitive and allowing for convenient display, editing, diagnosis, storage, and transmission of programs; PLCs do not suffer from the drawbacks of relay circuits such as poor contact, contact welding, wear, and coil burnout. Therefore, they were quickly adopted in NC machine tools. Currently, the instruction execution time on NC machine tools can reach 0.085µs/step, with a maximum number of steps of 32,000. Furthermore, using PLCs can significantly reduce system space requirements and improve system speed and reliability. 7. Development of Sensor Technology When an NC system is integrated with a machine, the geometric accuracy it can control is influenced not only by mechanical factors but also, and more importantly, by the sensors used, especially position and speed sensors. These include linear and circular induction synchronizers, linear and circular gratings, magnetic scales, and sensors utilizing magnetoresistive properties, which measure linear displacement and rotational angles. These sensors consist of optical, precision mechanical, and electronic components, typically with a resolution of 0.01–0.001 mm and a measurement accuracy of ±0.02–0.002 mm/m, while machine tool table speeds are below 20 m/min. With the continuous improvement of machine tool accuracy, higher demands are placed on sensor resolution and accuracy. This has led to the emergence of high-resolution sensors with "microstepping" circuits. For example, encoders developed by FANUC can achieve a resolution of 10⁻⁷ r through microstepping. High-precision CNC systems constructed using these sensors have created conditions for ultra-precision control and machining. 8. The Emergence of Open Technology In 1987, the U.S. Air Force published the famous "NGC (Next Generation Controller)" program, first proposing the concept of an open architecture controller. One of the key components of this plan was the proposal of the "Open Systems Architecture Standard Specification (SOSAS)". The U.S. Air Force defines an open architecture as one that allows multiple manufacturers to sell interchangeable and interoperable modules in a competitive environment. Machine tool manufacturers can add hardware and software to an open systems platform to create their own systems. Currently, there are basically two structures for open systems on the market: ① CNC + PC motherboard: A PC motherboard is inserted into a traditional CNC machine. The PC board mainly performs non-real-time control, while the CNC mainly performs real-time control based on axis motion. ② PC + motion control board: The motion control board is inserted into a standard slot in a PC for real-time control, while the PC mainly performs non-real-time control. To increase openness, mainstream CNC system manufacturers often adopt solution ①, which adds a PC board without changing the basic structure of the original system, providing a keyboard so that users can connect the PC and CNC, greatly improving the functionality of the human-machine interface. A typical example is FANUC's 150/160/180/210 system. Some manufacturers also refer to this device as a fusion system. Due to its reliable operation and open interface, it is increasingly welcomed by machine tool manufacturers and has become one of the development trends of NC technology. 9. Development of Manufacturing Technology The development of CNC machine tools is based on NC technology, mechanical structure technology, and manufacturing technology. The progress and development of these three technologies also promote each other. Moreover, the development of NC itself is also based on the development of mechanics. ① The increase in machining speed and precision requires the continuous expansion, improvement, and perfection of NC system functions. In particular, the requirements of high-speed and high-precision machining have led to the development of high-speed and high-precision control systems, including rapid program input, high-speed and high-precision interpolation, control, and output. ② The simplification and improvement of mechanical structures and the perfection of new machining functions require increasingly complex NC software functions and increasingly higher component performance. For example, the use of wide-range speed adjustment, high-speed, high-torque feed systems and high-power spindle systems simplifies mechanical structures and improves the machining efficiency and precision of machine tools. ③ The continuous operation, connection, and coordination of machining require the continuous improvement of NC system reliability. Machining and system information can not only be controlled, processed, transmitted, and managed, but also shared through networks. 10. Conclusion Currently, China's machine tool industry is gradually transforming from a major producer to a leading power, primarily reflected in the continuous development and improvement of the technological level and quality of CNC machine tools. In particular, the reliability of CNC systems and CNC machine tools has been continuously enhanced. Due to adjustments in product structure, new CNC products are constantly emerging, such as the successful development of multi-axis linkage, high-speed, and high-precision CNC machine tools. As a domestic CNC system manufacturer and sales company, Beijing FANUC Electromechanical Co., Ltd. has a responsibility to provide more reliable and feature-rich CNC products to meet the needs of China's machine tool industry.