Parametric CAD design of ternary point element blade expansion scribing template (2)

4. In the drawing program, there is also a problem of connecting points into a smooth curve. The unfolding boundary of the ternary blade should be a smooth curve. In the drawing program, the "Pline" function is used to connect the points, and the connected lines are angular lines. The program also needs to trim the broken lines into a smooth curve to ensure three. Yuan expands the smooth transition of the template boundary. To trim the polyline into a smooth curve, the key is to determine the point at which the polyline is selected. Since the number of boundary points of the ternary expansion template is not equal, the length of the blade groove is also different - that is, the position of the break point of the blade expansion template boundary is different, so that it is very difficult to automatically determine the point of selecting the polygonal line in the program. In the present system, the method of selecting the blade boundary feature points and closing all the unrelated layers is used to determine the points at which the fold lines are selected to achieve the trimming of the fold lines.

5. In the drawing procedure of the ternary element expansion template, it is necessary to have the function of automatically determining the boundary curve breakpoint. The expansion of the ternary element is a method of simulating the expansion of the ternary straight line, but the boundary points and boundary points of the two are different in the four boundaries of the upper, lower, the inlet and the outlet of the blade, so the template is drawn. The specific methods in the process are also different. The upper and lower boundaries and the import boundary of the ternary element expansion template boundary are curved edges. This requires finding the inflection point of the upper boundary and the inlet boundary in the curve and the inflection point of the lower boundary and the inlet boundary, and these must be automatically in the program. carry out. In this system, the method of judging the change of the angle difference between the two line segments is used to find the intersection inflection point.

6. Since the size of the blade is not the same, the position of the programmed graphic in the drawing may not be suitable. Sometimes the graphic needs to be moved up and down and left and right in the frame by a certain distance. Therefore, the system is added when the drawing is completed. The function of human-machine dialogue can artificially change the insertion point of the frame to achieve the purpose of correcting the relative position of the graphic and the frame.

Third, the conclusion

The system has been applied in many times. In the actual production of several blowers and compressors such as 2477 and H319, the system was used to complete the design of the prototype. After repeated modifications, the system has been basically applicable to various types of point element product blades.

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