Research And Implementation For Tool Path Generation Of Free Form Surfaces Machining

With the continuous development of manufacturing, the Computer Numerical Control (CNC) technology has become one of the most important technologies in the machinery manufacturing industry. At present, the application in product surface parts are more and more widely, especially the large complicated surface parts for CNC machining, it also puts forward a higher demand. The tool path without interference generation of the surface parts is one of the key technologies in Numerical Control (NC) machining field, and consideration to the efficiency and the surface quality is also a difficult problem.There are many advantages in the process of application of five-axis flats cutters machining, but also there are many obvious insufficient, such as the motion complex and cannot avoid interference well. Therefore, the three-axis ball-end machining in practical application is still widely used. The three-axis ball-end surface machining tool path generation algorithm and interference algorithm is studied in this paper. Based on ACIS platform and VC++6.0, build a small machining system, which is capable of simulating machining surface process, generating surface without interference, and the tool path can output standard tool path files.Through analyzing many kinds of curved surface machining methods, such as the APT method, the iso-parametric method, the method of curves of cross sections, the polyhedral machining method, the projection method and the method of offset surface, the constant scallop-height method is proposed as tool path planning of the surface machining method. The constant scallop-height method keeps the same scallop-height between the tool paths by controlling the distance between adjacent paths. At the premise of a known path, cutting tool radius and allowable scallop-height, calculate the next tool path. At finishing stage, the use of constant scallop-height machining with ball-end tool can make the scallop-height of surface of post-machining parts uniform, the machining quality better, improve machining efficiency. In the calculation of next path, the Newton iterative method is proposed to search in this paper, as a result from the fast convergence rate of the Newton iterative method. It can shorten the search time. So using the Newton iterative method as tool path generation search method can improve the efficiency of the machining.The tool paths interference is divided into the global intervention and the local interference. This paper lists the interference detection methods of these two interferences, and focus on dealing with the local interference of the tool paths. By using the polyhedral interference detection algorithm, it puts the machined surface discrete into a series of triangle surface with the accuracy of surface, and simplifies the judgment of the tool and the surface position relation into the judgment of the tool and the triangle surface position relation. For three axis machining, it is only to judge the tool and the triangle surface position relation, which fall on the tool projection region. This interference detection algorithm which based on polyhedral model can effectively eliminate the overcut interference.The small machining system that based on ACIS platform and VC++6.0, can prove the instance results. The small machining system interface is friendly in the choosing of a variety of geometric shape and inputting of the machining parameters and so on. The comparison results show that the case machining method in this paper that machining quality effectively improve the machining efficiency. It can show the generated interference-free tool paths, besides it can generate and output the standard Cutter Location (CL) paths files.Finally summarize the work done, obtain some useful conclusions, and propose some further research problems.