Research on the application of the hottest CATIA i

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Research on the application of CATIA in tractor body surface design

the development of computer graphics is changing with each passing day, which provides great convenience for contemporary industrial design. At present, the design software using three-dimensional solid model has completely changed the traditional industrial design mode, and provided a new creative platform for industrial design to adhere to the established layout of the past few years. Through forward and reverse design, At the beginning of R & D and design, the product shape can be simulated by computer, and then it is virtual assembled. Before the end of production, a specific three-dimensional space three-dimensional model is presented for designers to compare and analyze, and then it can be modified arbitrarily to provide a variety of schemes

1 characteristics of CATIA software

catia is an extensive CAD (Computer Aided Design)/cam (Computer Aided Manufacturing)/cae (Computer Aided Engineering)/pdm application system of IBM company. Catta shape design and style design provide a wide range of integrated tools for designing parts. This system has a strong surface modeling function, so it can be used to design the tractor body surface. CATIA was defined on the basis of automobile body modeling at the beginning of its development, but with the progress of the times and the development of software, it has been basically applicable to the needs of 3D modeling of various equipment, such as molds. For the modeling of the tractor body surface with the oil return valve closed again, you can also refer to the CATIA method for the modeling of the automobile body surface, but the modeling design should adapt to the characteristics of the tractor's own modeling, such as the characteristics of a series of tractor bodies with low surface smoothness but high structural strength requirements. The tractor body structure modeling mainly uses the wireframe and surface design, freestyle and sketch tracker modules of CATIA software package

in the 1950s and 1960s, tractor body modeling mostly adopted the modeling method of excessive curved surface, curve and large arc; In the 1970s, there was an excessive modeling style of trapezoidal small rounded corners composed of straight lines and planes; With the development of modern industry and the continuous progress of audit concept, the shape of tractor body is gradually approaching the direction of automobile body modeling design, and large curved surface, small circular arc and wedge have gradually become the mainstream. Using CATIA software, we can establish an accurate 3D curved surface model of tractor body, which can accurately reflect the intention of the stylist, and realize the modern complex, beautiful and streamlined tractor curved surface designed by the stylist. This is also the purpose of introducing CATIA to design the tractor body curve

2 application in tractor body modeling

2.1 body surface design process

some complex contours of contemporary tractor body are composed of irregular three-dimensional surfaces. Body design is the most basic link in tractor model development system engineering. Tractor design includes body structure design and body shape design. Tractor modeling design is the initial step of body design and a comprehensive idea in the initial stage of locomotive design. It is a main work of body cad/cam design method, and provides the basis for finite element analysis, process design and mold manufacturing of body structure in the future. In order to better connect the two departments of design and manufacturing. The theory of tractor body surface design based on CATIA is proposed. The specific modeling design flow chart is shown in Figure 1

Figure 1 flow chart of body modeling design

fig.1 flow chart of module and design of body

2.2 body surface design and surface segmentation

tractor body refers to the general term of all parts of the tractor except the engine and chassis. The modeling design of tractor body is mainly based on some aesthetics, body composition, color and decoration methods, so that the outline of tractor body can reach a coordinated and unified design method. With the technological development of agricultural machinery and the demand of the domestic market after China joined the WTO, farmers have higher and higher requirements for the appearance of tractors. Modeling with beautiful curves can endow products with stronger competitiveness. Structural design is an industrial design to meet the requirements of modeling design. The specific structural design of each assembly should be determined according to the block of modeling surface surface. The so-called surface segmentation is for the convenience of computer drawing. According to the existing surface theory and the surface modeling characteristics of application software, combined with the actual shape of existing products, the tractor body engine panel surface and cab surface are divided into several relatively simple and easy to handle surface blocks. In the computer, these surface blocks are spliced and stitched according to the actual smoothness requirements, or connected with them with transition surfaces, Finally, the plastic design of the tractor body is completed to realize the overall shape of the tractor body. The so-called smoothness includes the following contents: curves and surfaces have second-order geometric continuity, that is, smoothness; There is no redundant inflection point; The curvature changes uniformly; Meet the subjective feeling requirements of designers. The theory of surface segmentation has been relatively mature in the surface design of automobile body. When dividing the surface of tractor body, we can refer to the curve of automobile body, but we should treat the small arc and wedge-shaped surface unique to contemporary tractors differently

2.2.1 reverse calculation of the three-dimensional drawing of the body shape

using the freestyle and sketch tracer modules of CATIA software, after determining the origin of the body coordinates, reverse the three-dimensional view of the large and small outline sketch of the actual body in CATIA window according to the tractor span, the whole vehicle (length, width, height) and a series of dimensions on the data, as the basis of redesigning the body curve and surface. Of course, you can also reverse the 3D view of the external plastic of the product by scanning the l:1 sludge model with cloud points

2.2.2 principle of surface segmentation

surface segmentation must be comprehensively considered according to the shape characteristics of the modeled parts, the type of the selected surface, the degree of the surface, etc. Some complex contours of the contemporary tractor body are composed of irregular three-dimensional surfaces, so it is difficult to build its three-dimensional mathematical model with a surface to ensure accuracy. In order to ensure the design accuracy of the model, it is usually necessary to block the tractor body. The tractor body can be divided according to the following principles:

1) on the basis of ensuring the flexible modeling function of drawing curves and surfaces, the number of blocks can be minimized

2) when the surface is divided into blocks, it can produce special-shaped surfaces, that is, all surfaces must be defined on the quadrilateral domain

3) the result of surface segmentation should be convenient for the application of CAD software, that is, it should be convenient for data input

4) surface segmentation should be compatible with the modeling functions and functions of existing CAD software

2.2.3 establishment of curves and surfaces

to complete the modeling of a complex tractor body panel surface with high quality, you need to have the basic knowledge of computer graphics, mechanical drawing, mechanism technology and so on, and have some application experience in cad/cam software. Specifically, we should first understand the construction methods of various surfaces, and then understand the drawings, and be able to divide the surfaces into basic surfaces and transition surfaces according to different technical requirements

preliminarily analyze the outline sketch of the tractor body to understand the body surface. Since the recovery of the international market of surfaces is generated on the basis of curves, generating correct spatial curves is the basis for obtaining surface boundaries and generating two-dimensional surfaces, and it is also the key in modeling work. It has a decisive influence on the fairing of surfaces

generate the third transition curve between two surfaces, which is also a common function in body design. Because the fillet of some transition surfaces of the tractor body may be small, and the shape is relatively narrow and long, it is extremely difficult to measure accurately. It can not be treated as the main surface when making plastic. Of course, it is not necessary to make the theoretical intersection line of two surfaces. The supply of waste plastic particles 1 is in short supply, but automatically generate the transition surface after fitting the two main surfaces. After modeling the body surface in blocks, assemble all parts together, and then sew the curves of all parts of the body first, and then sew the surfaces. Finally, the whole tractor body engine cover can be sewn

2.3 shape correction

at all stages of the body surface creation and design process and after the creation and design, corresponding methods should be used to analyze and check according to different objects. It is necessary to check the condition of the built surface at any time. Analysis and inspection runs through the whole design process and is an important means to ensure the quality of design accuracy

2.3.1 curve

curve mainly analyzes its smoothness, especially the tractor diesel engine grab cover requires not only continuous curve, but also continuous curvature change. Only curves with curvature analysis can be used to generate surfaces. Most tractor covers do not require as much smoothness as cars. Sometimes, it is enough to achieve first-order geometric continuity in the U and V directions

2.3.2 surface analysis

when constructing a surface, analyze the shape of the surface, analyze the quality of the surface, check the size of the slit between the surface or curve and its continuity, check the curvature changes of the curve and surface, and pay attention to the analysis of the smoothness, distortion and tangent changes of the curve and surface, and then modify them in time

2.3.3 rendering inspection

after all the surfaces of the car body are generated and spliced, the overall surface should be evaluated. CATIA software can be used to render the lighting effect and check the overall modeling effect. The smoothness of the surface splicing can be checked by changing the position of the light source, changing the color of the surface, changing the viewing angle and other methods, and then the smoothness of the surface can be judged according to the distribution law of the brightness of the processed image. If the image brightness changes evenly, the surface smoothness is good, and vice versa. After the body surface modeling is completed, the printer can be used to output color modeling drawings. Of course, the large screen projection equipment can also be used to project and display on the large screen. Then further check the smoothness of the stitching of the transition surface

3 conclusion

here is a new idea of tractor design based on CATIA reverse three-dimensional model of tractor body, that is, starting from the effect drawing of tractor reverse three-dimensional design, using CATIA's line architecture and surface design module surface modeling technology to design tractor body surface, which lays a foundation for product concurrent design in the future, simplifies the whole design process, and shortens the development cycle of new products

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