Abstract: The development of modern CNC systems aims to improve the productivity of CNC machine tools. Based on the analysis of the latest products and technical documents from world-renowned CNC companies, this paper discusses the main development directions and problems to be solved in modern open CNC systems. Keywords: CNC; CNC machine tool; open CNC system 0 Introduction The development of modern CNC systems revolves around improving the productivity of machine tools, namely, improving the machining performance, efficiency, and information acquisition capabilities of machine tools. This paper discusses the development of modern CNC systems from these aspects, focusing on improving system control performance, adopting new drive technologies, and using open structures, as well as the problems to be solved by PC CNC systems. 1. Improving Machine Tool Performance Besides being influenced by the machine tool's structure and the performance of the cutting tools, the performance of CNC machine tools is significantly affected by the functionality of the CNC system. Specifically, this includes the following aspects: 1.1 Control Capability of the CNC System The control capability of a CNC system refers to the number of control axes, the number of linked axes, control resolution, program segment preprocessing time, interpolation time, and other software capabilities. The number of control axes refers to how many independent motion axes the CNC system can drive. It depends on the system's hardware control capability and software processing speed. More control axes, besides directly participating in machining, can also be used to complete auxiliary machining functions such as workpiece transport and tool management. This improves the performance and effectiveness of the machining system. Modern high-end CNC systems mostly provide control capabilities of 10 or more axes, allowing users to configure according to their needs. The number of linked axes refers to the number of motion axes that the system can control simultaneously in the machining preparation command. A higher number of linked axes means the machining system can process various complex surfaces, enabling multi-dimensional machining. Modern CNC systems provide interpolation algorithms for spatial straight lines, spatial circular arcs, helices, and spline curves; some also provide specialized surface interpolation algorithms. Clearly... These improvements have significantly enhanced the adaptability and machining capabilities of CNC machine tools. Control resolution depends on the upper frequency limit and mathematical processing capability of the displacement detection circuits in the mechanical transmission system, displacement detection system, and CNC system, thus limiting the machining accuracy of the CNC machine tool. Within the same system, it is mutually constrained by the system's maximum machining speed. Modern CNC systems employ high-precision displacement sensors (high-resolution encoders, linear scales) or digital subdivision in the circuitry to improve sampling resolution, increase the operating frequency of the interface circuits, and improve the processing speed of the controller to resolve the contradiction between control resolution and motion speed. Modern high-end CNC systems can achieve resolutions of 0.1 or even higher. Program preprocessing refers to converting standard CNC code into the internal format of the CNC system for use in tasks such as interpolation. Preprocessing time is the time spent on these tasks. Since this work is performed on each program segment, the preprocessing time directly determines the minimum movement distance of the program segment that the system can process under a given machining speed, and vice versa. When the workpiece being machined determines the minimum movement distance of the machining program, it becomes a bottleneck for improving machining speed. Modern CNC systems, due to the use of high-performance processors, can achieve speeds as low as 1 mm per program segment. Achieving machining speeds of hundreds of meters per second. The interpolation cycle is the time interval between the main CPU of the CNC system sending displacement commands to the axis CPUs. During this interval, the main CPU must complete the preprocessing of the machining program, tool compensation and interpolation calculations, and other auxiliary tasks. This indicator is determined by the system architecture, the processing power of the main CPU, and the complexity of the interpolation function. Together with the preprocessing time, it determines the possible machining speed and accuracy of the machine tool. Modern CNC systems employ two methods to improve the interpolation cycle and preprocessing time: a) adopting a multi-CPU architecture to reduce the burden on the main CPU; b) improving the performance of the main CPU. Modern CNC systems can achieve interpolation cycles of 4ms or less. Modern CNC control software also provides new control functions to improve the machining accuracy and performance of machine tools. For example, it provides built-in adaptive control software and other robust control software to adapt to changes in machining materials, tools, and mechanical properties. This results in better machining quality; provides control algorithms to improve the impact of mechanical crawling in the zero-speed zone during the acceleration and deceleration of motion axes on the machining quality of arcs and other curves; and provides control algorithms combined with servo systems to achieve zero-following error control. Providing a high-speed interface for the servo system is also a characteristic of modern CNC systems. A high-speed digital interface allows the CNC system's CPU to instantly access the necessary control data from the servo system, enabling the use of more advanced control algorithms. This improves machining quality without affecting machining speed. 1.2 Performance of Servo Drive Systems CNC machine tool feed drive systems include stepper motor systems, DC servo systems, analog AC servo systems, hybrid AC servo systems, fully digital AC servo systems, and linear servo motors. Stepper motor systems employ advanced technologies such as microstepping and smoothing, combined with closed-loop feedback, resulting in significantly improved performance. High-end stepper motor systems have control resolution and torque/speed characteristics comparable to ordinary DC servos. Furthermore, due to the use of electronic damping and other measures, the resonant frequency range is greatly reduced, making them widely used in low-speed applications and single-phase power supply situations. However, due to their low starting and stall torque, they may experience step loss, limiting their application in high-speed, high-precision applications. The development direction of servo systems is towards fully digital AC servos and linear servos. Compared to traditional analog servo systems that use ±10V analog speed signals for control, fully digital servos connect to the CNC system via a communication bus. Internally, a high-speed DSP is used to complete the closed-loop control algorithms for the position loop, speed loop, and even the current loop. It has the following characteristics: a) It uses digital setpoint and digital feedback, eliminating the impact of interference on system performance in these two channels; b) It connects to the CNC system via a digital bus, allowing the CNC system to obtain more information from the servo system, which is beneficial for the implementation of various control methods and system monitoring; c) The fully digital servo uses computer control, which can employ various advanced control algorithms to improve the tracking accuracy of the servo system, even achieving zero-error tracking, greatly improving the machining accuracy of the machine tool; d) The fully digital servo can use PWM signals from the computer system to control the power devices driving the motor, isolating the control system from high-voltage electricity, which helps improve the system's anti-interference capability and reliability; e) It uses a light encoder feedback system with power-off protection. After power-on, it feeds back the machine tool position data to the CNC system, eliminating the need for a return-to-reference-point action; f) It can automatically adjust the optimal control parameters for different controlled objects, making system installation and adjustment easier. The linear motor consists of a magnet attached to the bed and a steel bar with coils attached to the moving parts. Because there is no contact between mechanical parts... Therefore, it has the following advantages: a) It can be used in high-speed machining applications, with a movement speed of 3-4 m/s, which is 6-8 times that of traditional motors. b) Fast response time: The response time of the traditional servo motor and ball screw drive system is about 100ms, while that of the linear servo is 10-20ms. c) High acceleration: The acceleration of the linear motor drive system can reach 2-10 m/s², which is more than 10 times that of the traditional drive system. d) High reliability: The linear motor system reduces mechanical system wear and has a high reliability of up to 5000 hours, which is 5-10 times that of the traditional system. 2. Improving the effectiveness of machine tools The effectiveness of machine tools is determined by their reliability and the speed and convenience of maintenance. Modern CNC systems achieve the above requirements from the following aspects: 2.1 Improving the reliability of system components and parts: In addition to using the latest electronic technology to improve their own reliability, modern CNC systems also use other technologies to improve the overall reliability of machine tools. For example, using linear motors reduces mechanical wear, and using its own software and displacement detection system to eliminate the need for reference point return and overtravel protection switch actions increases machine tool reliability. 2.2 Built-in Fault Diagnosis and Location System Modern CNC systems, in addition to utilizing various advanced electronic and artificial intelligence technologies to locate faults when machine tool malfunctions occur, can also provide early warnings when potential faults appear but do not affect machining, enabling timely repairs and preventing greater damage. 2.3 System Structure and Component Universality To quickly obtain replacement parts for damaged CNC machine tools, modern CNC systems mostly adopt modular and structured system architectures. Connections between various components use standard connectors and electrical protocols, making identical functional components interchangeable between different series of the same product or between different products. 3. Enhancing Machining Information Acquisition Capabilities Modern open CNC systems, especially those based on computer platforms compatible with personal PCs, have excellent information acquisition capabilities, mainly reflected in the following aspects: 3.1 User-Friendly Human-Machine Interface Modern CNC systems often adopt graphical user interfaces and touchscreen operation functions similar to personal computers, greatly facilitating operation. Many open CNC systems also provide the function of customer-customized user interfaces, allowing users to design their preferred human-machine interface according to their needs. 3.2 Excellent Integrability Modern CNC systems offer a variety of serial communication protocols and network protocols for users to choose from, allowing for easy connection to various networks or systems to share information and exchange data. Industrial PC-based CNC systems also allow users to develop their own applications to process CNC data. 3.3 Built-in CAD/CAM Systems Modern CNC systems, coupled with multi-user real-time graphical operating systems and continuously enhanced CPU capabilities, make it possible to integrate graphical program input systems or simple CAD/CAM systems into CNC systems. This allows for design work without affecting machining, changing the monotonous and rigid pure instruction input method of older CNC systems. 4 Problems to be Solved in PC-Based Open CNC Systems The above discussion outlines the characteristics and requirements of modern CNC systems in terms of improving the machining performance, efficiency, and information acquisition capabilities of CNC machine tools. Clearly, utilizing existing PC software and hardware research results is an effective means to achieve these requirements. The key areas requiring in-depth research include the following: 4.1 Standardization of Motion Control Cards Currently, hundreds or even thousands of motion control cards based on the PC bus are available on the market. However, because they only use the same hardware bus standard and lack corresponding software standards, they are not suitable for the requirements of modern CNC systems. A software standard for motion control cards, similar to a PC's "plug-and-play" standard, should be researched to enable instant replacement of different motion control cards. 4.2 Real-time and Simplified Windows NT Operating System Windows NT is a robust multi-tasking graphical operating system, but its task scheduling method lacks real-time performance, and its excessive functionality and large size make it unsuitable for real-time applications. Improvements must be made in these two aspects to create a practical and reliable CNC software platform. 4.3 Standardization and Chip-based Development of Control and Interface Software To facilitate users in developing their own interface and control software, object-oriented design methods should be adopted. Standards for CNC control and interface software should be researched, and standard CNC control and interface software libraries or software chips should be developed, allowing users to develop and improve upon these standards. 5 Conclusions Modern CNC systems utilize the latest achievements in electronic and computer technologies and are developing towards high openness, high reliability, high speed and high precision. We should seize this opportunity, utilize our talent advantages, and combine the software and hardware products provided by open systems to develop modern high-end CNC systems suitable for our national conditions, so as to promote the development of CNC industry and manufacturing industry. References [1] Selecting a CNC System. Factor Impacting MachineTool Productivity [z]. GE Fanuc CNC Technica Brief. [2] High speed Machining with GE Fanuc Linear Motors [z]. GE Fanuc CNC Technical Brief. [3] Performance Improvement with Digital Drive Technology [Z]. 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