Analyze how to design plastic mold with tool center trajectory software

The dynamic simulation of the tool center trajectory and the realistic modality display of the curved surface ensure the accuracy of the processed plastic molds; the advanced C-Bzier surface modeling theory has the advantages of simple algorithm, easy parameter selection, accurate shape expression, and avoidance of the NURBS method. In the modeling process, there are problems such as the difficulty in selecting the right application, and the complexity of calculation. The system design method and surface modeling technology can be applied to the development of other Windows-based small and medium CAD/CAM systems.

(1) Accurately expressing the dimensions of the product's corridor. Figure 3 shows the design of the cone surface of the track-type cone. According to the symmetry, the surface is divided into four parts. Each section of the corridor contains a section of straight line and four sections of arc. These shapes have dimensional requirements on the drawings. Surface modeling with C-Bzier can accurately represent these shapes. The traditional Bzier and B-spline modeling methods can only be expressed approximately.

(2) The algorithm is relatively simple Through the analysis of the surface, it is determined that the u-direction and w-direction G1 of the two C-Bzier surface patches are spliced ​​to form a 1/4 cone surface. The C-Bzier surface patch G1 has a continuum concept, clear geometric meaning, and simple splicing conditions between surfaces. If NURBS is used for surface modeling, although the shape of the curved surface can be expressed accurately, the selection right should be complex and the splicing between surfaces is difficult.

(3) The parameterization of curved surfaces is particularly important for machining surfaces with numerical control machines. C-Bzier retains many of Bzier's strengths. Each 1/4 cone surface is determined by a total of 32 control vertices. The surface mesh is uniform and the convex hull properties are good.

(4) Easy shape control According to the C-Bzier theory, the adjustment of the surface shape can be achieved by modifying the control vertices, modifying the control parameters, or both. According to the actual production, it is determined that the shape of the curved surface is adjusted by adjusting the position of the control vertex at the joint of the two surface patches. That is, through the shape factor, the degree of fatness and thinness at the corner of the racetrack surface is determined.

If the system adopts NURBS method, the shape control is not intuitive, and it is often necessary to modify the position of the control point, the node vector, and the weighting element interactively, so as to obtain a curved surface shape that meets the requirements. The operation system of the example of the basin mold CAD/CAM software programming is Windows98, and the software development platform is MicrosoftVisualC++610. It is a small Windows-based CAD/CAM system developed by using MFC (MiscomsoftFoundationClass) and OpenGL. The requirements for software operation are: more than CPU586, more than 16 megabytes of memory (32 megabytes recommended), 600 megabytes of hard disk capacity, and Windows 95/98 operating system. The following is an example of a runway type paper bowl punch face milling. The input of the part parameters can be directly read into the part parameter file in the part parameter dialog box, or the parameters can be input directly through the dialog box. After confirmation of the parameters input, the system displays the two-dimensional part drawing of the cone surface.

At this point, the dimension of the part can be further modified according to the two-dimensional part drawing until the part meets the design requirements. After the part parameter is modified and saved, you can read the process parameter file through the process parameter dialog box or enter the process parameter directly in the dialog box. After the input of the process parameter, save the file; select the processing type through the curved surface processing menu, and the system asks you to answer some questions. The machining selection dialog box, after the system generates the CNC command file, displays the tool center trajectory for machining the part; the trajectory can be further rotated and amplified by the tool center trajectory menu. At the same time, through the surface display menu, the shape of the surface of the part is realistically displayed dynamically to ensure that the part meets the design and processing requirements. If you find that there is something that does not meet the requirements in the tool path display or the surface realism display, you can go back to the Part Parameters and Process Parameters dialog box and interactively modify the corresponding parameters until a satisfactory result is achieved.