The "PC + motion control card" type CNC system will be a milestone in open CNC systems. This system supports user customization of motion control strategies, embodying a core-level open philosophy. From this system onwards, CNC systems will enter a "completely open" era. In 1952, MIT and Parsons collaborated to invent the world's first three-axis CNC milling machine. Its control unit consisted of thousands of vacuum tubes, and its interpolation device used pulse multipliers. The successful development of this machine tool marked the beginning of NC technology and a new era in the machine tool manufacturing industry. Since the first CNC milling machine, with the development of electronic component technology, computer technology, and servo technology, modern CNC systems have greatly improved in terms of functionality, performance, stability, and processing speed. As the core component of CNC machine tool control, the CNC system plays a significant role in promoting the development of CNC technology. Its development can be roughly divided into the following stages: [align=center] [/align] Figure 1 As machining accuracy and speed increase, the development of CNC systems demands continuous expansion, improvement, and perfection of their functions. In particular, the requirements for high-speed, high-precision machining have led to the development of high-speed, high-precision control systems, including rapid program input, high-speed, high-precision interpolation, control, and output. Furthermore, the simplification and improvement of mechanical structures and the enhancement of new machining functions require increasingly complex NC software functions. Moreover, the continuous and coordinated operation of machining demands continuously improving the reliability of NC systems, requiring machining and information systems to not only control, process, transmit, and manage, but also share data via networks. For these reasons, PC-based open CNC units have begun to be widely used in the CNC field. 1. Open CNC Systems An open system architecture is defined as a module that allows multiple manufacturers to exchange and interoperate with each other in a competitive environment. Machine tool manufacturers can add hardware and software to an open system platform to create their own control systems. Currently, there are two main popular open CNC architectures: 1. CNC + PC motherboard: A PC motherboard is inserted into a traditional CNC machine. The PC motherboard mainly runs non-real-time control, while the CNC mainly runs real-time control based on the coordinate axes. 2. PC + professional motion control card: A motion control card is inserted into a standard computer slot for real-time control, while the PC is mainly used for non-real-time control. Option 2, in particular, fully utilizes the advantages of fast computer processing speed and a user-friendly human-machine interface, making it increasingly popular among machine tool manufacturers and becoming the mainstream of open CNC development in China in recent years. 2. Hardware Structure of Open CNC Systems The following section uses the MPC01 motion control card, independently developed by Step-Servo, as an example to introduce an open CNC system with a "PC + professional motion control card" structure. This system adopts a master-slave control structure: the PC is responsible for managing the human-machine interface and real-time monitoring of the control system (e.g., displaying system status, sending control commands, etc.); the slave device uses the Step-Servo MPC01 series motion control card to handle all control details, including pulse and direction signal output, automatic lifting processing, and detection of origin and limit signals, etc. The industrial PC's CPU and the dedicated motion control chip on the MPC01 control card constitute a dual-CPU hardware structure of "PC + MPC01," with DOS or Windows as the operating system. 2.1 Control Method and Characteristics of the MPC01 Series Motion Control Card Step-Servo Co., Ltd. is a technology-driven professional motion control company. It is one of the major manufacturers of motion control cards in China. The MPC01 series motion cards use imported dedicated chips, are highly integrated, stable, and reliable; they are also equipped with a rich and powerful motion function library that can be called in C/C++ or VB environments, and communicate with the computer via a bus. Furthermore, due to its use of VXD virtual driver technology, it effectively utilizes Windows' underlying interrupt calls, enabling real-time multitasking. This significantly reduces the burden on the host and programming in terms of processing time and task switching, improving the overall operating speed and control accuracy of the control system. 2.2 Control Structure of the Control System The control system is based on the MPC01 industrial PC and uses a Panasonic digital AC servo system to form an open CNC system. Utilizing the MPC01... The multi-axis motion control function connects the AC servo system to the pulse output channel of the DMC to output the motor speed signal. It can also accept feedback signals from the photoelectric encoder to achieve full closed-loop control. Additionally, through the DMC's DB15 interface, it can receive inputs of motion control-related I/O quantities from the machine tool, such as signals from the machine tool origin and limit switches. The motion control card must communicate with a PC to complete the machine tool control tasks. Through the PC's peripherals, it can input and edit machining programs, set parameters, and monitor the real-time status of the machine tool. Furthermore, leveraging the powerful graphics and data processing capabilities of the PC, the system's DNC function can be easily implemented. [align=center] [/align]Figure 2 Control System Block Diagram 3. Software Structure of the Open CNC System [align=center]Figure 3 Software Structure of the Open CNC System[/align] This system fully leverages the advantages of abundant PC software resources and fast data processing speed, incorporating features of CAD/CAM. After generating part drawings using modeling software, the DXF format files of the drawings are converted into machining G-code. The G-code is then interpreted into motion control functions on the control board. Finally, by calling interpolation motion functions from the MPC01 motion function library, the machine tool control is achieved. 4. Conclusion: The "PC + Motion Control Card" CNC system will be a milestone in open CNC systems. This system supports user customization of motion control strategies, embodying a core-level open philosophy. From this system onward, CNC systems will enter a "completely open" era.