Research And Practice Of Process Trajectory Optimization Algorithms For Complex Contours:Area-Chord Constraints And Double-Headed Snake Algorithm

The machining quality and efficiency of complex contour parts is an important reflection of the processing capability and level of CNC machine tools.The processing process of ordinary machine tools is mainly with the help of CAD/CAM software to discrete complex curves into continuous micro-line segments or micro-arc segments,and then through the linear and circular interpolation function of the CNC system for processing.However,this continuous micro-line segment processing method can not guarantee processing efficiency and surface quality because its tool trajectory is not smooth,the amount of NC code,and frequent acceleration and deceleration of the machine tools.Therefore,this paper takes the generation and optimization of tool trajectory as the entry point to carry out research,innovatively proposes a new curve discretization and tool trajectory smoothing and compression algorithm,develops a CAM system with intelligent optimization of complex contour tool trajectory,and realizes the function of "click output" of CNC code.The specific research contents are as follows:(1)To address the problem that the existing single-constraint curve discretization algorithm lacks flexibility between quality(contour accuracy)and efficiency(number of trajectory segments),this paper innovatively proposes an area error-chord error double-constraint method to realize curve discretization with adaptive curvature variation characteristics,and by adjusting the size of the double-constraint value,it can keep more points in the large curvature region to ensure accuracy and fewer points in the small curvature region to ensure efficiency.The influence of micro-segmentation on the curve is deeply analyzed,and the mathematical model between the number of trajectory segments and the contour error and the constraint value and the contour error is established,and the correctness of the model is verified by the "heart-shaped" curve.(2)To address the problems that the local smoothing strategy of tool trajectory can hardly insert transition curves between adjacent trajectory segments and cannot reduce the number of trajectory segments and the global one is not applied to medium and low-end CNC machine tools,this paper creatively designs a double-headed snake(DHS)tool trajectory optimization algorithm based on the least squares method with the help of heuristic concept,which can transform complex curves into a smooth combination of linear and circular segments.The experiment proves that the DHS algorithm can reduce the number of trajectory segments by more than 70% under the same error constraint,reduce the contour error by more than 90% under the same number of trajectory segments,and the tool trajectory is smoother,which greatly improves the machining efficiency and quality of complex parts compared with the commercial software Master CAM built-in algorithm.(3)Given the dependence of the current computer-aided process design and manufacturing system on foreign software,this paper practically embeds the proposed DHS algorithm into the sheet metal CAM system(Sheet CUT＿CAM V1.0)developed by the group,builds a curve optimization function module to realize the complex curve and tool trajectory drawing and CNC code "click output" function.The feasibility and efficiency of the curve optimization module are verified through the actual processing of the "dolphin" pattern,which greatly enhanced the intelligence and practicality of the sheet metal system,and further improved the machining quality and efficiency of irregular contour parts on economical CNC machines.