Research On Rough Machining Tool Path Planning For Large Nuclear Power Head

With the development of nuclear power industry in China,the demand for nuclear power equipment is getting higher and higher.Large nuclear power head is a key component of nuclear pressure vessel.The shape of the part is complex and the size is large,which lead to the difficulty of processing.Therefore,it is of great significance to solve the manufacturing problem of the nuclear power head by reasonable planning of machining technology and NC machining tool path.In this paper,based on the analysis of the process of the large nuclear power head,the tool path planning problem of the multi connected region which appears when the outer surface of the large nuclear power head was rough machined is studied.The main research work of this paper is as follows:Firstly,the structural characteristics,processing requirements and key problems of NC machining process of the large nuclear power head are analyzed,Which includes the analysis of the types of blank,the process datum,the processing method,the cutting tool and the fixture.Finally,the processing route of the outer surface of the nuclear power head is developed.Aiming at the problem that the tangent plane area appeares when the outer surface of the large nuclear power head was rough machined is multi-connected domain,the contour parallel topology of the tool path is determined.In order to solve the problem of low efficiency and large computation caused by the traditional direct offset method to generate contour parallel tool path,the tool path planning method based on Voronoi diagram is discussed.Firstly,the basic equations of Voronoi diagram are deduced.Then,according to the characteristics of multiply connected domain,a Voronoi diagram generation algorithm based on the theory of separation and wavefront-propagation is presented.On the basis of the above,the processing area of plane figure is divided.Then,in each processing area,the tool path is generated based on contour offset.On the basis of the above theory,several key technologies of VC++ programming are studied in order to realize the automatic generation of tool path.First of all,the interface between UG and VC++ program based on DXF file format is established to obtain thedata of each section of the 3D nuclear power head model in UG.Secondly,the construction of Voronoi digram is realized by using object-oriented data structure of double linked list.the data structure of double linked list.And the automatic generation of contour parallel tool path is completed based on the Voronoi diagram.Finally,the data structure of NC code is analyzed,and the DXF format tool path file is converted into NC code for simulation verification.Based on VC++ programming,a prototype system of tool path planning for rough machining of nuclear power head is developed.The system uses MFC multi document application programming technology,which can realize the function of graph reading,tool path generation,file output,NC code conversion and so on,thus to verify this algorithm is effective and available.