Abstract: This paper introduces the characteristics and advantages of open CNC systems and analyzes the application of Intranet networks in enterprises. Combining these two aspects, the concept of Direct Computer Numerical Control (DCNC) networks is proposed, and an application model is given, analyzing its workflow. Keywords: Openness; CNC system; Enterprise network; Direct Computer Numerical Control (DCNC) network. Open CNC systems, with their significant advantages, have become the future trend of CNC systems. The rapid development of computer technology, especially PC technology, has brought them boundless vitality. Network technology has also made great strides in recent years, making the expansion of Intranet networks in enterprises inevitable. Integrating multiple open automated machining equipment within an Intranet environment to form a Direct Computer Numerical Control (DCNC) network gives enterprise equipment such as CNC machine tools great flexibility, controllability, and reconfigurability. This will greatly improve the enterprise's ability to adapt to a changing market. 1. Open CNC Systems Previously, due to the limitations of computer technology, the performance of general-purpose microprocessors was poor and could not meet the requirements of CNC machine tools. To improve the performance of CNC systems, dedicated computer chips had to be designed, such as integrating interpolation calculations directly into very large-scale integrated circuits. This led each CNC manufacturer to design dedicated hardware systems and develop dedicated software systems. From then on, CNC systems followed a closed path. Currently, global CNC system production is concentrated in a few large manufacturers such as Fanuc, Siemens, and All, and their CNC systems are generally closed. This prevents third-party manufacturers from developing related applications; and the latest computer hardware and software technologies cannot be applied to CNC systems. With the rapid development of computer technology, open CNC systems are gaining increasing attention. The concept of openness was first proposed by American scholars as early as 1987. Open CNC systems use general-purpose software and hardware support systems, making the system platform open. Openness allows multiple manufacturers to provide reusable components, which can be seamlessly combined to form high-performance, low-cost CNC systems. Open CNC systems offer perfect support for the TCP/IP protocol, which has become a global industrial standard. Currently, CNC systems generally employ two open solutions. The first maintains the original NC kernel while adding a PC front-end, providing a user-friendly interface and other functions. This is essentially a semi-open system, a compromise proposed to protect the interests of existing CNC manufacturers. The second solution involves the PC completely controlling the operation of the entire CNC machine tool, using a general-purpose high-performance computer and a general-purpose operating system. This runs a CNC system with open characteristics on a completely open hardware and software platform. This is a fully open solution and has become the mainstream of future CNC system technology development. Using a PC as the core of the CNC system to form an open CNC system has significant advantages. First, it allows the use of the latest computer hardware and software technologies. Due to the compatibility of general-purpose microcomputers, a higher-performance PC can replace an older one as the core of the CNC system. Second, it significantly reduces the development costs of CNC systems. Because closed CNC systems have proprietary hardware systems and operating systems, their development costs are extremely high. With an open strategy, the computer hardware system uses a general-purpose PC, requiring only the design of corresponding interface modules. The Windows operating system platform on a PC offers extremely high performance and provides many powerful application development tools, such as Visual C++, Wildcard C++, Delphi, Visual Basic, and JAVA. These development tools allow for the rapid and efficient development of powerful CNC system software, significantly reducing software development costs and time. Third, both hardware and software prices are reduced. The high performance-to-price ratio of general-purpose microcomputers and operating systems significantly lowers the price of the cN12 system. Fourth, it enhances the performance of the CNC system. Previously, due to limitations in computing speed, many CNC functions were implemented in hardware; now, these functions can be implemented in software. This increases system upgrade capabilities and allows for the implementation of functions that were previously impossible in software. Fifth, it greatly improves the scalability, maintainability, and ease of use of the cN12 system. The use of general-purpose PC hardware and software makes the expansion, maintenance, and use of the CNC system as simple as a regular application. The development of computer technology has given open CNC systems a powerful vitality. A typical microcomputer can now achieve a computing speed of 500 MIPS (500 million instructions per second), which is comparable to the performance of a mid-range computer in the past. Furthermore, according to the famous Moore's Law, computer performance doubles every 18 months while its price halves. Increasingly powerful general-purpose computer systems enable open CNC systems developed on top of them to fully match or surpass the performance of dedicated systems. 2. The Rise of Intranets Intranets are internal networks or enterprise networks. They can be defined as: Internet networks used within enterprises. Intranets developed alongside the popularity of the Internet, possessing all the characteristics of the Internet. Simultaneously, because they are used within enterprises, their security and reliability are enhanced. The Internet is based on the TCP/IP protocol. Thanks to this protocol, all computers worldwide can be interconnected. Therefore, the TCP/IP protocol can be considered the core of the Internet. Countries around the world have invested heavily in Internet network technology, making the technology very mature. Numerous network products support TCP/IP, offering high performance-to-price ratios. The TCP/IP protocol has also become a globally recognized industry standard. Within enterprises, there has always been a strong demand for networking to enable the free flow of information, thereby improving management and enhancing enterprise competitiveness. This is a crucial foundation for concepts like CIMS and agile manufacturing. The emergence and rapid development of Internet technology provided excellent opportunities for enterprise network applications, leading to the application of Internet technology within enterprises and the formation of Intranets. Currently, Intranet applications mainly include: www (Global Times), FTP (File Transfer Protocol), E-MAIL (Email), newsgroups, and BBS (Blog Board System). These applications are suitable for marketing, market research, information dissemination, and correspondence. In an Intranet environment, a large amount of useful information can circulate freely within the enterprise, allowing various management departments to obtain the necessary information promptly and efficiently, enabling them to analyze and make decisions, which plays a vital role in improving enterprise management. Enterprise networks also have significant implications for the realization of FMS, CIMS, and agile manufacturing concepts. A key foundation for these concepts is a good network environment that allows for the free flow of information. However, both FMS and CIMS are costly and technically challenging. One reason for this is the lack of unified protocols and the lag in network technology. In the early 1980s, General Electric (GM) developed the Manufacturing Automation Protocol (MAP), and MAP 3.0 was released in 1988. However, due to various reasons, the MAP protocol did not develop into a global standard. Many network protocols coexisted within enterprises, making the establishment of a unified network both costly and difficult. This problem was only solved after the TCP/IP protocol became the de facto industry standard. Another reason is the closed nature of CNC systems, which makes it difficult to interconnect machine tool systems from different manufacturers, and it is almost impossible for third parties to develop related applications. The open approach completely solves this problem. General-purpose software and hardware platforms have perfect support for TCP/IP, allowing third-party development and integration. Any open system can connect to an Intranet and integrate software and hardware products from different manufacturers, thus leveraging the resources of many manufacturers to build a high-performance, low-cost automated machining system. 3. Application Model of Open CNC Systems in Intranets Considering open CNC machine tool systems as the smallest production unit, and using an Intranet network environment as a foundation, directly connecting multiple open automated devices constitutes a Direct CNC Networking (DCN). This will be an important approach for future automated production systems. DCN is built on a unified network environment, Intranet, using the TCP/IP protocol as its core. This unified network environment allows any two networked devices to exchange information, providing significant flexibility in device management. TCP/IP is a set of protocols with a physical and data link layer at its core. It can utilize various network products such as Ethernet, Token Ring, Token Bus, Fibre Channel, and ATM. These network products are technologically mature and offer high performance-to-price ratios, making Intranets built with these new products relatively inexpensive. For a very common Ethernet network like 10Baae-T, its bandwidth can reach 10 Mbps, meaning it can transmit 10 megabytes per second. This bandwidth ensures real-time data transmission. For example, a complex 3D surface might generate a 200MB NC code file after modeling. Considering multiple devices coexisting on the network, with an actual transmission rate of 1 Mbps, transmitting a 200MB file would only take 200 seconds. However, machining this surface on a high-performance CNC machine tool might take several hours. In other words, the data transmission time is far less than the actual machining time. Furthermore, 100M Ethernet technology is now mature, and there are even higher bandwidth options such as Ethernet, FDDI, and ATM. TCP (Transmission Control Protocol) also provides comprehensive reliability guarantees, employing connection management, acknowledgment and timeout retransmission mechanisms, and flow control technologies. These technologies effectively ensure reliability. Not all devices can join the DCN network; only devices with open characteristics can efficiently connect to the DCN. Open systems use general-purpose operating systems and have perfect support for TCP/IP, enabling networking at minimal cost. Open systems can provide a wealth of timely and valuable information accessible to any device on the network, such as machine tool operating status, various cutting parameters, tool condition, and current work progress. Networked management and control computers can query this information at any time, utilize expert and management systems for judgment and calculation, make decisions, and issue corresponding instructions. The open system then adjusts the machine tool's operation based on the received instructions. DCN also allows the inclusion of various CAD/CAPP/CAM systems. Since most such systems support the TCP/IP protocol, once these systems join the Intranet, their calculation results can be directly transmitted to any networked system. Therefore, various open systems can be easily integrated in a DCN environment. Figure 1 shows a DCN system model consisting of four open CNC machine tool systems and two workstations. They are interconnected via an Intranet. One workstation runs large software systems such as CAD/CAM/CAPP, called the auxiliary computer, whose function is to generate CNC code based on the product design. The other workstation runs management, scheduling, and monitoring software, called the control computer. It is the center of the entire system and its function is to monitor the operation of each device and coordinate the operation of other devices in the system. The other four are open CNC systems, running on PCs based on the Windows platform. They execute machining tasks, send machine tool operation information to the control computer, make certain requests to other devices on the system, respond to commands sent by the control computer, receive NC code from the auxiliary computer, and execute it. In a typical DCN system, the workflow is as follows: 1) The CAD system in CAD/CAM/CAPP designs the product, CAPP creates the process flow, and the CAM system generates the corresponding NC code. 2) The control computer analyzes the working status of each CNC machine tool system and instructs the auxiliary computer to transmit the corresponding CNC codes to each CNC machine tool system. It also instructs the CNC systems to prepare. 3) The CNC machine tools execute the received NC codes and send the machine tool status during machining to the control computer. If any abnormalities are encountered during machining, the control computer is requested to handle them. 4) After machining is completed, the CNC system sends a machining end signal to the control computer and requests a new machining task. 5) After all machining is completed, the control computer notifies each system to stop working and perform appropriate post-processing. In these processes, steps 2), 3), and 4) are repeatable because each machine tool system may need to receive multiple NC code files and execute multiple machining tasks. It can store the NC code files on the hard drive and call them during machining, or it can transmit them directly from the network during machining. The system adopts a client/server computing structure, with the control computer as the client, the auxiliary computer and the four CNC systems as servers. The servers receive requests from the clients, respond accordingly, and return the results to the clients. Once a connection is established, both sides can send and receive requests to each other. Information transmission between any two devices on the network is bidirectional, making them essentially client/servers to each other. Each open CNC system in the system is an autonomous system. It can automatically execute commands and handle various situations during machining. Especially in emergencies, such as tool collisions, the system needs to react within milliseconds. The CNC system can automatically handle emergency situations, whereas computers on the network cannot transmit information and perform related actions in such a short time. The CNC system automatically handles emergencies, while the control computer handles less urgent events. Information transmitted over the network is command-level, such as downloading NC code, transmitting machining status, and monitoring equipment. This ensures reliability and security while reducing the amount of data transmitted over the network. An enterprise can have multiple DCN systems. These systems are connected via an Intranet, forming a unified whole with the enterprise's MRP II system, MIS system, etc., as shown in Figure 2. These management systems can obtain relevant information from the control computer in the DCN system or obtain more detailed information directly from the open machine tool system. In such a unified network, the DCN system and other management systems can be seamlessly connected, providing ample and useful information for use, thereby effectively improving management efficiency. Because the DCN system is built on a unified network, its hardware costs are low, and because it uses a general-purpose operating system, they all support the TCP/IP protocol, making the software support environment extremely easy to establish. No redevelopment is required; the only software to be developed is the network application within the system. This is an excellent choice for Chinese developers who have limited network hardware experience but are skilled in application development, significantly reducing development costs. Open CNC systems can provide a wealth of internal machine tool operating information for use by computers, greatly improving management efficiency. The Intranet is an integral part of the enterprise and is also connected to the Internet. Any devices connected to the Intranet or Internet can be grouped together to form a DCN system, eliminating geographical limitations. Devices from different workshops or even different factories can form a DCN, providing excellent conditions for agile manufacturing. The reconfigurability of the DCN is also excellent; once a DCN system completes a processing task... The equipment can be immediately reassembled into a new system to complete new tasks. This does not require physical reorganization. The corresponding network program can be run on the corresponding control computer, and information can flow in an orderly manner within the new I)CN system. The DCN system composed of open CNC system and Intranet has the advantages of low hardware cost, low software development cost, good performance, high flexibility and good reconfigurability. It has high application value for realizing the idea of ​​agile manufacturing. It will play an important role in enterprises responding to the rapidly changing market. [References] [1] Todd J. Sehuett. Beyond DNC Modem Machine Shop 1996, (1): 146-154 [2] Mark Albert. Software Is The CNC. Modern Machine Shop. 1997, (II): 134-144 [3] Rick Dove. Agile Machines and Agile Production Production. 1995, (9): 15-19 [4] Wang Shilong, Liu Fei. Development of DNC integration technology. Chinese Journal of Mechanical Engineering, 1998, (2): 8-10 [5] Zhao Wansheng, Ma Jun, Wang Bo, et al. The role of open architecture in the future development of electrical discharge machining (EDM) CNC systems in my country. Electrical Discharge Machining, 1995. (3) 2-6 Author's biography: Shi Xuming (1972-), male, from Shanghai. Lecturer at Shanghai Industrial and Commercial Foreign Language School, PhD. Application of PC-based open CNC system in Intranet: PDF