Abstract This paper takes the shape of a complicated turbine axial flow runner as an example, and studies the method of geometric design of complex shape parts by combining AutoCAD and UNIGRAPHICS. It points out that using AutoCAD to do the preliminary work and equipped with large CAD/CAM software. The unit's external cooperation to complete the design is an effective measure for the company to save money and time and improve design quality.
Key words complex shape parts; AutoCAD; UNIGRAPHICS; geometric modeling
Chinese Library Information Classification Number TP 39.72
A STUDY OF THE GEOMETRIC MODELING OF THE
COMPLEX CONTOUR PARTS WITH CAD/CAM
Wang Sui
(Dept. of Engineering Graphics, Guangdong Industrial Univ.)
Abstract Taking the complex contour wheeling-rotating as an example, the paper studies the geometric modeling of the complex contour parts by means of both AutoCAD and UNIGRAPHICS. It points out that the use of AutoCAD in the first phase of the design work should be carried out in close cooperation with those units which contains large CAD/CAM graphic software so as to produce design. Such an approach is an effective measure to reduce expenses and save time. Moreover, it improves the quality of design for the enterprise.
Key words complex contour part; AutoCAD; UNIGRAPHICS; geometric modeling
In the design and manufacture of electromechanical products, many parts have complex shapes, inconvenient mathematical descriptions, and the two-dimensional maps are not easy to be clear, which poses certain difficulties for design expression and processing programming. CAD geometry modeling of complex shape parts has always been a difficult research topic, and general mechanical CAD software is not easy to do. Such as the use of UNIGRAPHICS, Pro / E, EUCLID, CATIA, I- deas and other large CAD / CAM software geometry modeling system and complex profile design features, you can carry out the geometric shape of complex shape parts, but this kind of software and its Matching computer workstations or high-end microcomputers are expensive, and can be undertaken by non-official enterprises. Collaborative design with qualified enterprises is more expensive. Therefore, using AutoCAD to do the preliminary work, through data conversion and cooperation with the unit equipped with large CAD / CAM software to complete the design and CNC machining programming, is a practical measure to save costs and time and improve design quality. This paper takes the turbine axial runner blade parts as an example to discuss the feasibility of the design method combining AutoCAD and UNIGRAPHICS.
1 data input and conversion
The turbine axial flow runner is composed of a blade and a runner body with an upper crown and a lower ring. The blade is usually a complex curved surface. The profile and profile must be designed strictly according to requirements to ensure that the unit has a higher Dynamic and economical. The traditional design mostly uses wood formwork, but the amount of data drawn by the wood form drawing is limited, and a large error occurs during measurement and processing. The use of computer-aided design related functions to achieve the shape of the blade can greatly improve the design quality. The basis of the design of the part is derived from the raw data of the sample measurement, which is described by a sectional view. The height of the different sections defines the Z coordinate, and the X and Y coordinates are defined by the section. Therefore, the primary problem is to solve the data input. In the design, the AutoCAD function function is used to read these spatial points, and the B-spline curve is respectively formed in AutoCAD according to the spatial section line, and the DXF or IGES interface file is generated by AutoCAD DXF or IGES interface to complete the data conversion. These curves were read using UNIGRAPHICS software. The process is shown in Figure 1.
Figure 1 data transfer process
Fig. 1 Fhe process of data transmiting
2 part modeling
2.1 Three-dimensional modeling of the blade
2.1.1 Establishing the blade section curve
1) Run UNIGRAPHICS;
2) Read the cross-section data of the DXF or IGES interface file generated by AutoCAD conversion;
3) Establish a third-order B-spline for the front and back of the blade, and use the front and back spline breakpoints of the blade cross-section and the fillet radius measured by the sample to establish the fill-in edge;
4) Repeat steps 2) and 3) until the full section curve of the blade is established in the UNIGRAPHICS environment, as shown in Figure 2.
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