| With the development of the equipment manufacturing industry and the diversification of market demand, the CNC technology went into an unprecedented rapid development. With the integration of computer technology, machinery technology and automation technology, the CNC technology is widely used in the aerospace, automotive, mold and other industries. In recent years, with the advancement of technology and the expansion of market demand, the demand for CNC machining of large and complex curved surfaces urgent increasingly. Large and complex curved parts having a curvature change free curved surface, it increasing the difficulty of surface information extraction and analysis, and put forward higher requirements to CNC machining, so that the sculptured surface of the tool path planning techniques is becoming one of the key technologies of CNC machining. The purposes of sculptured surface tool path planning is higher machining accuracy, faster processing speeds and better quality of the workpiece.In modern numerical control system, CNC machine can not processing directly from the NC code, the interpreter must be used on the NC program interpretarion. The interpreter can extract the relevant data into the corresponding processing command to control the machine for the actual machining of the workpiece. So, the interpreter is one of the core modules of the CNC system, and the efficiency and effectiveness of the interpreter have a direct impact to entire numerical control system.Above all, this paper make a depth study on the sculptured surface tool path planning, interpretater of numerical control system and other aspects, and obtained the following research:(1) With the problem of insufficient accuracy of tool path, a scallop-height high-precision tool path planning method is proposed. The method is for the special requirements of the finishing machining, which use the precision machining strategy. The method uses a reciprocating path pattern, the generated tool path with high precision can meet the constraints of the processing error and maximum residual height. With the problem of the judgment of concave and convex, we propose a fast method for the judgment of surface. In the process of tool path planning, the number of points on offset toolpath and bias tool path is the same, it cause the over-reliance on the current tool path, this problem and the problem of lack of precision is solved.(2) With the problem of insufficient speed of tool path, a high-speed spiral tool path planning method is proposed. The method is for the roughing and the special requirements of some workpiece’s efficiency machining. All the Generated tool path points is on the sculptured surface, which can make the surface information maximize fidelity and is conducive to get more precise machining surface. The use of the tool path smoothing techniques on the tool path planning process can make thetool path length is effectively increases which lead to the smoother surface finishing. Meanwhile, on the tool path planning process, the phenomenon of self-intersection is eliminated which can improve the processing speed and the surface quality.(3) With the problem of insufficient surface smoothness of tool path, a high surface smoothness tool path planning method is proposed. The method use surface quality priority processing strategies is for the high surface quality machining and the special requirements of some workpiece’s surface quality. Every cutter contact point on the initial tool path has the minimum tool attitude angle rate changes, which can ensure the generated tool path is smooth. Meanwhile, the smoothing algorithm for the bias tool path can maintain the consistency between the adjacent tool path, which can improve the irregularities between adjacent tool path and lead to smooth tool path. Finally, the problem is consider and solved:the sculptured surface boundary are not covered because of the implementation of the toolpath smoothing algorithm.(4) With the increasing demand for high-performance CNC interpreter, on the basis of the analysis of NC code format, the basic principles of the interpreter, function and the call module is described in detail. A interpreter structure model is proposed, the entire interpreter is divided into five parts:lexical analysis module, syntax analysis module, processing command storage structure, processing commands module and error handling module, and each module construction method is detaily descripted. With the combination of top-down analysis method, we use EBNF to describe the the NC code grammar rules, and modify the original grammar rules, eliminating the ambiguity of the NC code grammar. |
