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The three-dimensional model of the gear is reversed. This paper uses the new ActiveX automation interface technology (activeX5) to develop the Visual Basic software programming for AutoCAD [1], and uses the three-dimensional modeling function of AutoCAD to realize the reverse of the three-dimensional model of the gear. First, reference the AutoCAD object library in the VisualBasic programming environment, that is, select the reference in the project "menu bar", click the AutoCAD object library, and set the variable AcadApp to AutoCAD object with the statement SetAcadApp=CreateObject(AutoCAD.application"). , can refer to AutoCAD object methods, attributes, etc. for 2D and 3D solid modeling, display, editing.
The reverse thinking of the gear 3D model: the coordinates of the points of the tooth contour obtained in the previous section are drawn by the AddSpline spline curve method. The fitting point fitPoints of the spline curve is a three-dimensional array, where the Z values ​​are all zero. The fitting point does not necessarily take all the tooth contour points, and the value can be taken according to a certain number of actual effect intervals of the graphic. The tooth contour drawn by the spline curve is defined as the area by the AddRegion method, and then the area is stretched into a three-dimensional model according to the thickness of the gear by the AddExtrudedSolid method, that is, the three-dimensional model of the gear tooth is reversed, as shown in the figure. 2a, b are shown. The following are the main program implementation statements.
Draw the tooth contour spline curve Stretch 3D gear Set gear = MdS.AddExtrudedSolid(regionObj(0), Height, 0) To get the complete 3D reverse model of the gears with all the teeth, use the ArrayPolar method to complete the completed wheel The tooth is circularly arrayed, the center point of the circular array is the gear center obtained above, the number is the number of gear teeth, and then the three-dimensional entity of the gear core is constructed by AddCylinder method, and then Boolean sum operation is performed by BooleanacUnion method to form a gear whole. As shown in c. It should be noted that Boolean sum operations cannot be directly performed on array entities. The three-dimensional entities in the model space are traversed by statements, and only Boolean operations are performed on all 3D entities. The main program implementation statements are as follows: retObj=tooth. "Then gears. Booleanac Union, ObjNext finite element analysis results of the X-direction stress cloud and numerical display as shown, it is done by the finite element analysis module in MDT (mechanicaldesktop) software, the graphical interface method is the first three-dimensional generated in AutoCAD The entity is saved in the DWG format and opened in the MDT.
Application and Method of Reverse Model This method obtains reverse data and 3D model application as follows: a. Store the 3D inverse model generated in AutoCAD in STL file, which can drive the rapid prototyping machine to manufacture products or prototypes. b. Convert the coordinates of each point of the obtained tooth contour into a numerical control code, which can be used for gear numerical control machining. c. In the MDT, save the graphics as an IGS format file, and open and perform finite element analysis in almost all analysis and modeling software packages including Ansys. d. According to the comparison between the reverse data and the contour curve and the standard gear, the modified parts, numerical values ​​and other parameters of the gear are obtained. e. It is possible to simulate the motion of the gear.
Conclusion The three-dimensional model reverse method of spur gear is realized by computer programming, which is accurate, fast, simple and easy, and low in cost. The method is applicable to other similar planar parts with the same cross-sectional shape, such as a disc cam, and has high practical value.