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Typical application of CATIA surface reconstruction technology

CATIA is playing an increasingly important role in product reverse modeling. On the one hand, its powerful surface modeling function, combined with its rapid surface reconstruction module and point cloud module, can easily complete the reverse modeling of products. On the other hand, due to the high integration of CATIA itself, a series of follow-up work such as mold design, processing and analysis can be carried out directly after the completion of modeling, avoiding the trouble of data loss caused by data exchange between different software. Therefore, reverse modeling with CATIA will bring a lot of convenience

the following are typical examples of CATIA applications

first, modeling parts with complex surfaces, such as toys, car shapes, car interiors, daily-use plastic products, sculptures, etc. these products are characterized by complex appearance and basically surface modeling. In CATIA, we can use its powerful surface function to reconstruct the final surface through construction lines

Figure 1 reverse process with complex surfaces

second, another case is that the product has typical large surface characteristics, and the surface transition is a kind of product completed by chamfering, which is more popular in household appliances, such as vacuum cleaners, TV back covers, washing machine appearance, etc. This kind of products do not require high accuracy of products, but have high requirements for external surfaces

Figure 2 reverse product process with large curved surface characteristics

third, mechanical products often have obvious geometric features, such as plane, round hole, spherical surface, fillet, etc., such as aviation sheet metal parts, mechanical connectors, etc

the above situations are typical applications, but the actual reverse process may require the comprehensive application of various methods according to different requirements and shape characteristics. The following is a toy modeling to illustrate the reverse modeling process of CATIA products and several problems that should be paid attention to

after inputting the point cloud in CATIA, we first need to analyze this product and find that the toy shape is mainly based on the surface, and the surface is relatively complex, with many surface features. It is a symmetrical shape, and the symmetrical plane is already a defined coordinate plane. In addition, because it is a toy plastic product, the accuracy requirement is not very high. To this end, we have a general process

1. Establish triangle lattice:

triangulation of point cloud is a very important step in the reverse process. Scanning point clouds are often large, and some large point clouds have millions or even millions of points. If you do not generate triangles for simplification, it will be difficult for current computer hardware equipment to operate them; Another important reason is that after triangulation and simplification, it can be very convenient to prepare for the future line formation auxiliary surface. There are several problems to pay attention to here. After the point cloud is imported, the point cloud should be processed. Generally, the adaptive method is selected to filter the point cloud. The advantage of this is that more points can be retained where the curvature changes greatly, and less points can be retained where the curvature changes little. Another is that when triangulating, the selection of neighborhood parameters should be appropriate. If it is too large, the quality of the generated triangle is poor; if it is too small, there are too many holes. Generally, according to experience, it is judged that if the triangle is not innovated, it will have backward quality, and the remaining individual holes can be repaired with repair tools. Another problem to pay attention to is that after the point cloud is generated, we should use the mesh cleaner function to clear some errors in the point data

2. Establish the curve structure:

this part is a very cumbersome work, but the quality of the curve oil return valve when loading the sample directly determines the quality of the surface generated later, so we should do this part carefully

it should be done in several parts, such as dividing the toy's ear into parts and eyes into parts. Use the function of curve projection to the point cloud to generate the characteristic intersection line. First use the curvature analysis function to analyze the curvature change line, and then use the function of curve projection or spline generation on the point cloud to generate the curve fitting with the point cloud. After completion, use the planarsections function to make the section intersection line with the point cloud along the characteristic curve

Figure 5 line architecture process of toys

3. Establishment of surface architecture:

catia provides a good surface tool, surface network. This function requires that a closed curve area be established by using curvesnetwork, and then the surface can be quickly assisted. It's best to select all tangent continuity for auxiliary surfaces, so as to ensure the quality of auxiliary surfaces

the space point cloud curves we generated earlier are non intersecting. At this time, if we want to deal with them in other surface modules in CATIA, we need to re break and connect these curves into intersecting curves, which can also be completed by using various surface commands, but this is time-consuming and the surface accuracy is insufficient. The surface lattice tool provides us with great convenience. It can define the intersection and interruption of spatial curves according to a certain precision setting, and then connect them to the point cloud curvature analysis spatial 3D curve establishment curve projection to the point cloud to complete the curve construction, continue to generate other curves, and generate section lines along the curve to form a "closed" spatial curve. Here we should pay attention to setting the accuracy of the curve lattice. If the accuracy of the curve made in front is high, we can set a very high accuracy here to produce a closed surface. Therefore, every step of CATIA reverse is interrelated and will have an impact on the final result

after making each surface, use the surface blend function in the advanced surface module to connect the surfaces. One thing to pay attention to is that when the elongation accounts for the original length when symmetry breaks, do not directly use the combined surface for symmetry. If it is directly symmetrical, the curvature continuity of the surface at the symmetry plane will not be guaranteed. Our practice is to offset a plane with the symmetry plane (the distance cannot be too large), then cut the surface, and then symmetry, Finally, the blend function is used to continuously combine the selected curvature of the symmetrical two surfaces (as shown in the red surface part in the figure). The surface quality obtained in this way will achieve curvature continuity and meet the requirements

after surface modeling, the distance analysis function in CATIA can be used to automatically save the model experimental results for point cloud error analysis. The analysis results show that the maximum error is 0.552mm and the minimum is 0.332mm. The maximum error is generally generated at the surface transition, because the surface transition is completely completed by relying on the surface function, which is separated from the point cloud itself, so the error will be larger than that in other places. But this is also for the modeling of the model itself. Fish and bear's paw cannot have both. If you want the model to be beautiful, you must abandon some accuracy requirements. For this model, such accuracy has fully met the requirements

summary: This paper analyzes and summarizes the typical application process of CATIA in reverse products, and explains the problems and methods that should be paid attention to in CATIA reverse combining with the actual reverse modeling process of products. We look forward to more and better ways to communicate with you. (end)

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