Research on cadcam geometric modeling of the hotte

Research on cad/cam geometric modeling of complex shape parts

Abstract Taking the axial-flow runner of hydraulic turbine with complex shape as an example, this paper studies the method of combining AutoCAD and Unigraphics to carry out geometric modeling design of complex shape parts, and points out that using AutoCAD to do relevant preliminary work, and cooperating with units equipped with large-scale cad/cam software to complete the design, It is an effective measure for enterprises to save money and time and improve design quality

keywords complex shape parts; AutoCAD； UNIGRAPHICS； Geometric modeling

Chinese graphic data classification No. 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 Co. there are some advanced tensile machines on the market. In addition to the above items, plex 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 possess 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 manufacturing of mechanical and electrical products, there are many parts with complex shapes, inconvenient mathematical descriptions, and difficult two-dimensional drawings, which cause certain difficulties in design expression and processing programming For a long time, the CAD geometric modeling of complex shape parts is a difficult research topic, which is not easy to be achieved by general mechanical CAD software For example, using the geometric modeling system and complex surface design characteristics of large cad/cam software such as Unigraphics, pro/e, Euclid, CATIA, I-DEAS, etc., the geometric modeling of complex shape parts can be carried out. However, such software and its matching computer workstation or high-end microcomputer are expensive, which can be borne by non ordinary enterprises, and the cost of computer operation is also relatively expensive when engaging in collaborative design with qualified enterprises Therefore, using AutoCAD to do relevant preliminary work and cooperating with units equipped with large-scale cad/cam software to complete the design and NC machining programming after data conversion is a practical measure for enterprises to not only save expenses and time, but also improve the design quality Taking the blade parts of the axial-flow runner of the hydraulic turbine as an example, this paper discusses the feasibility of the design method of combining AutoCAD and Unigraphics

1 data input and conversion

the axial-flow runner of hydraulic turbine is composed of blades and runner body with upper crown and lower ring. The blades are usually complex sculptured curved bodies, and their profile lines and surfaces must be designed in strict accordance with the requirements to ensure that the unit has high power and economy The traditional design mostly adopts the wood model diagram, but the amount of data drawn by the wood model diagram is limited, which will produce large errors in measurement and processing Using the relevant functions of computer aided design to realize the modeling of blades can greatly improve the design quality The modeling design of the part is based on the original data from the sample measurement, which is described by the section diagram. The Z coordinate is defined by different section heights, 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 is used to read these spatial points, make B-spline curves in AutoCAD according to the spatial section line, and use the DXF or IGES interface of AutoCAD to generate DXF or IGES interface files to complete the data conversion Then use Unigraphics software to read these curves The process is shown in Figure 1

Figure 1 data transmission process

Fig.1 fhe process of data transmission

2 part modeling

2.1 three dimensional modeling of blade

2.1.1 establish blade section curve

1) friction forces will be generated between the working piston and the working cylinder when running unigra

2) read in the section data of DXF or IGES interface file generated by AutoCAD conversion

kostron has rich experience and strong strength in the development, utilization and application of composite materials. 3) establish third-order B-splines on the front and back of the blade respectively, and use the spline breakpoints on the front and back of the blade section and the fillet radius measured by the sample to establish the fillet of the water inlet edge

4) repeat steps 2) and 3) and their eyes will focus more on experienced and practical talents until all the sectional curves of blades are established in the Unigraphics environment, as shown in Figure 2

2.1.2 establish blade surface

Figure 2 blade curve described by section

fig.2 the vane curve described by section

1) in this example, because there are many section curves, double patches are used to construct the surface, and a surface is established for the above blade section spline by using the through curves option and the parameter modeling method in create → free form feature

2) use the water outlet endpoint of each section spline to establish two curves on the front and back of the blade respectively, and use the ruled option of create → free form feature to establish the ruled surface

3) use create → Fe