Free-form Surface Modeling And Cnc Machining

In this paper, aimed at the part Known model points, the freeform surfacesculpting and numerical control (NC) machining idea of calculating the control pointsof the Double Cubic B-Spline Surface in reverse and fitting is put forward. The DXFfile, the DWG document and the NC program file of the surface are created.Firstly, the databases are created dynamically with DAO program interface, thedata is inputted using the data control method, the Data control and the DBGridcontrol are customized to establish the visible data-imported interface and thesimplification of introducing the repeated data and the successively-changed datathrough programming.Secondly, the tri-diagonal equation is solved using the chasing and drivingmethod and the control points are reckoned on the contrary with the bi-curvecalculated in reverse from the surface model points. Afterwards DXF file whichentities section is mostly made up of the model points and the control points is builtand the DWG document is set up, then the surface designed is showed.Lastly, the length and the distance of the tool-moving are ascertained and thefreeform surface is fitted. Then the tangent vectors in the two directions are figuredout to gain the normal vector of the fitted points and the coordinates of the centerpoints of the tool are received after the radius of the tool is decided. And the data inthe database that consists of the center points of the tool are manipulated using theSQL sentences according to the tool-moving path. The NC machining programcreated is revealed by transferring WORD with the OLE automation technology andthe tool-path is simulated dynamically in the end.According to the development desktop of Win98 and making use of Visual Basic6.0 for taping tools, the application software for sculpting and NC machining freeformsurface is authorized. The functions of shaping freeform surface and creating NCprogram can be accomplished interactively. And the surfaces have been displayed andthe tool-path has been simulated dynamically by utilizing ActiveX Automationtechnology to cannibalizing the AutoCAD software.