Wire Cutting CAD/CAM Technology Based on AutoCAD

In recent years, single-machine numerical control systems have gradually been replaced by microcomputer-based group control systems (DNCs). Manual programming has evolved from a graphical to an automatic process, and CAD/CAM technology has become widely integrated into modern manufacturing. Due to the powerful drawing and editing capabilities of AutoCAD software and its open DXF data interface, it has become a key component in graphics input platforms and automatic programming. However, many current AutoCAD-based automatic programming systems rely on predefined processing sequences without incorporating automatic tool path compensation, requiring users to manually set machining directions. For complex parts, this often involves tedious manual parameter adjustments, which can be time-consuming and error-prone. This paper presents a solution using ARX development technology and Visual C++ 6.0 to perform secondary development on AutoCAD. The goal is to integrate graphic input, editing, automatic tracing, NC programming, and master-slave communication within the AutoCAD platform, ultimately achieving seamless CAD/CAM integration.

2 System Structure

The system operates in a master-slave control mode, where the host uses a mid-range microcomputer, while the slave is based on a single-chip computer system that directly controls the wire-cutting machine. Through the RS-485 interface, the host can manage multiple slaves, leveraging the microcomputer’s strong computing power for tasks such as graphic input, output, and database creation for cutting process parameters. The host's automatic programming module converts graphic data into NC machining instructions, which are then sent to the slaves for execution. At the same time, the slaves provide real-time feedback to the host, supporting functions like real-time control, automatic tracking, and database updates. The host software includes six core modules: graphic input, process parameter processing, automatic programming, simulation, tracking, and communication (see Figure 1).

3 Automatic Programming Technology

The automatic programming module focuses on solving issues such as automatic tracing, direction discrimination, and tool path compensation, aiming to achieve full CAD/CAM integration. The process flow is illustrated in Figure 2.

Figure 2 Automatic Programming Software Flow Chart

3.1 Get Graphical Data and Generate Basic Process Closed Loop

The system uses the DXF file generated by AutoCAD to extract feature information through a feature-based modeling approach. It only needs to read and process the ENTITIES section of the DXF file to obtain geometric data, forming the topological relationships between the part’s outline and its elements. Since CAD drawings are stored in the order they were created, not according to the machining sequence, the system reorders the endpoints to form a closed loop. This separation of drawing and processing simplifies the input process, allowing users to focus on design rather than sequence. The system uses a double-linked list structure to store entity information, which is efficient and well-documented in literature.

3.2 Judging the Processing Direction

This paper employs a vector-based method to determine the machining direction. An example of a closed-loop shape (Figure 3) is used to illustrate the algorithm. By traversing the doubly-linked list, the system identifies the endpoint closest to the X or Y axis as the starting point. From there, vectors AB and BC are analyzed to determine the original figure's direction. This method simplifies the judgment process and ensures accurate tracing. The direction determination is shown in Figure 4, where each quadrant is classified based on the vector orientation.

3.3 Forming the Actual Machining Path

When generating the actual machining path, factors such as the shape of the workpiece, the diameter of the molybdenum wire, the discharge gap, and the machining direction must be considered. The tool path compensation amount is calculated based on these factors. Assuming the radius of the molybdenum wire is r and the unilateral discharge gap is δ, the offset value is f = r + δ. Adjustments are made to arcs and straight lines by modifying their radii or moving them along the normal direction. This ensures precision and reduces errors caused by tool parameters. Additionally, transitional arcs with a radius greater than or equal to f are added at sharp corners to prevent issues like wire breakage and short circuits, improving both safety and efficiency. After all entities are adjusted, the system performs interpolation and sends the commands to the slave system, completing the CAD/CAM integration process.

4 Conclusion

The AutoCAD-based CAD/CAM technology described in this paper has been successfully implemented in our institute’s precision instrument factory, enabling technical upgrades and group control management for the CKX-1 and DMK6732 CNC wire-cutting machines. Users only need to understand basic drawing operations and follow design requirements, without worrying about the machining process. All complex calculations and tool path compensations are handled automatically, separating graphic input from processing. Once the drawing is completed, the host directly controls the machining, achieving full CAD/CAM integration. The system supports precise machining of complex contours and features a user-friendly interface that is easy to operate. It reliably performs automatic tracing and tool path compensation, reducing the operator's workload and significantly improving processing efficiency.

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