Moreover, the NC+PC mode typically does not offer a secondary development environment. It provides only basic interface reconfiguration and parameter settings, along with PLC programming functions and tools—often just simple switch configurations. While some PC-based open CNC products allow users to adjust the number of control axes or channels by adding or removing interfaces, they also provide libraries for users to build their own system configurations. However, this level of openness demands advanced secondary development skills from users, making the process less user-friendly and less accessible. This paper addresses these challenges by focusing on the hierarchical structure of open systems, the network activation mechanism for condition monitoring, and the intelligentization of the secondary development platform. 2 The Hierarchical Structure of Open Architecture The goal of adopting a hierarchical design is to enhance system scalability and configurability—two key indicators of system openness. Scalability allows the system to flexibly add hardware interfaces to expand functionality and improve performance. Configurability enables the use of existing low-level modules through configuration and compilation without changing the hardware, allowing for customized software solutions. The hierarchical architecture centers around modularity but differs from traditional modular approaches. It considers not only the functional relationships between components but also their roles and status within the overall system. It clarifies the inheritance and derivation relationships between components, using these as standards for defining system elements rather than relying solely on functional criteria. This hierarchical approach can be applied at all levels of the system's internal and external structures. When components are subdivided according to functional and performance requirements, the same inheritance and hierarchical standards apply to each substructure. As shown in Figure 2, the hierarchical CNC system includes a base layer 0, which contains all the essential components for basic control functions and the necessary hardware and software interfaces for general expansion. Layer 0 serves as the core structure and must have well-defined internal and external interfaces to ensure smooth communication between components and maintain the system's stability and security. Additional layers built on top of layer 0 extend the system’s functionality and improve control performance by adding hardware and open software interfaces. There are two types of additional layers: supplementary expansion and parallel expansion. Supplementary expansion involves opening new interfaces based on existing components to configure different control software forms, thus expanding the system's functionality. Parallel expansion adds equivalent functional components to meet special control requirements or to open new control channels. Distinguishing between these two types of expansion allows for the full utilization of structural and interface inheritance. Supplementary expansions follow interface inheritance and are embedded as function points within the system’s interface level, making it easier to standardize individual function extensions and meet user customization needs. Parallel expansion follows structural inheritance, replicating entire functional groups to create parallel control schemes with the original hierarchy, thereby enhancing the integrity of the open structure. The motion control module is the core of the CNC system, and open-structured motion control components must support both parallel and supplementary expansions (see Figure 3). Parallel expansion is used to increase the number of axes, such as deriving four-axis and five-axis components from a basic three-axis control system. Supplementary expansions are used for adding special functions, which are user-defined and implemented via interfaces. Both the basic components and those derived from parallel expansion share the same supplementary extension interfaces. Figure 3 illustrates a basic three-axis motion control assembly expanded into four-axis and five-axis components, with each motion component additionally supporting three special functions: complex curve interpolation, position error compensation, and vibration condition monitoring. 3 Intelligent Development Mechanism of Secondary Development Platform As shown in Figure 5, the secondary development platform model adopts a guided development approach. Using pre-defined information bases, user functional requirements are translated into combinations of specific strategies in the database. These strategies are then compiled using a code compiler compatible with the CNC system’s microcontroller core and sent to the simulation development interface via the computer’s parallel port. A dedicated storage area exists within the CNC system for online verification of user-customized function codes. This area is isolated from the normal NC program storage area to ensure the safety of secondary development. The verification strategy and evaluation mechanism return the performance metrics of the secondary development. The secondary development environment offers two methods: language description and guided setup. The language description method uses a structured functional mechanism, pre-defining the algorithm structure of system extensions. Users simply need to describe their functional requirements according to the algorithm prompts. The secondary development platform provides an independent structured description language (grammar structure shown in Figure 6), which uses object-oriented concepts to fully describe the working state of a CNC component as a functional object group. This language-based approach allows for deep customization of the system’s internal software configuration and is suitable for tailoring the system’s underlying policy schemes. The guided setup method uses a development wizard (as shown in Figure 7) to customize user expansion requests through a graphical query interface, typically used for simpler extension development. Combining these two mechanisms creates a hierarchical secondary development structure. 4 Conclusion    The open CNC system constructed using the hierarchical structure scheme and micro-control core represents a significant breakthrough in system architecture. The hierarchical thinking is embedded in every component of the system, and an intelligent secondary development strategy is introduced. The hierarchical structure framework will link the development, use, and maintenance of the CNC system, making it truly open throughout the entire lifecycle of the CNC equipment. Transparent Plastic Tube Cutter,Mtc-A Plastic Multiline Clamp,Mtc-B Plastic Multiline Clamp,Translucent Plastic Tube NINGBO AIHUA AUTOMATIC INDUSTRY CO.,LTD , https://www.iwapneumatic.com
The research and demonstration of open control systems, both domestically and internationally, have primarily focused on the development of PC hardware and software. These applications essentially represent a dedicated use of PCs for I/O interfaces and human-machine interfaces (see Figure 1). However, both the structure and performance are highly limited. First, there is no independent open architecture specifically designed for CNC machining control. While the openness of a computer is inherent in its design, it is not tailored for the specific needs of numerical control. This approach relies entirely on the existing computer system framework, which lacks the necessary hardware and operating system support for precise CNC processing, making it difficult to build a reliable and efficient CNC platform. Second, the real-time performance and reliability of industrial PC (IPC)-based open CNC systems are often compromised. Since these systems use general-purpose operating systems, they consume significant system resources, and non-NC-related tasks may interfere with the timely response of the system, reducing the speed at which control events are handled and increasing the risk of instability. Third, the cost of IPC-based CNC systems remains high. A PC capable of handling CNC processing requires a motion control card that can cost several thousand dollars, making it expensive. In contrast, an embedded microprocessor costs just a few hundred yuan, and a programmable device chip is about $100. With free open-source real-time operating systems, there are no additional software licensing fees, leading to a significant cost reduction. This makes the system more affordable while maintaining good performance. Fourth, the network functionality of current IPC-based open CNC systems is limited. These systems rely on standard computer networks, which are not optimized for the transmission of large signal data streams required for CNC processing and condition monitoring. As a result, their remote network capabilities are mainly limited to program transfers between systems. 
1 Research Background