The NURBS method is built on the B-spline method, which better realizes the unification of analytic geometry and free-form surface, and becomes the mainstream of surface mathematical expression in CAD/CAM software. Such surfaces can be formed using four-sided parametric surface interpolation, stretching, rotation, Lofting or Skinning, Sweeping, Blend, and four-boundary construction. A complete set of surface extensions (such as intersection, clipping, transformation, splicing, and smoothing algorithms. However, this method can only be obtained when the measurement point data satisfies the requirements of tensor product distribution and data change is not too severe. Smooth surfaces are not suitable for surface reconstruction of large-scale scattered data.
With the deep research of reverse engineering and its CAD reconstruction theory, the commercial application of its results has been paid more and more attention, and a large number of commercial reverse engineering CAD modeling systems have emerged. At present, there are dozens of softwares that provide reverse modeling on the market, but they can be roughly divided into two categories: one is dedicated reverse software, such as Imageware, Geomagic, Polyworks, CopyCAD, ICEMSurf and RE-Soft; The second is to provide forward CAD/CAM software for reverse processing module, such as PTC's Pro/Scan-tools module and UG's Point cloudy function.
The reverse engineering software adopts NURBS or triangular domain surface modeling. It has strong point cloud processing function, but it is difficult to identify features, relying on the experience of operators; at the same time, the function provided when performing surface fitting modeling Not as advanced as forward CAD/CAM software. The forward CAD/CAM software mostly uses the B-spline or NURBS method for surface modeling, and has a strong surface modeling function. For the processing of point cloud data, although there are specialized modules, the processing function is not rich and powerful compared with the reverse software.
At present, the application of CAD reconstruction technology in reverse engineering is still a very professional work. How to choose the reverse construction suitable for the enterprise's own needs according to the actual situation (such as the level of model reconstruction personnel, the characteristics of enterprise products, etc.) The modular software system still has practical significance. The literature compares the reverse software currently commercialized on the market, but focuses on the basic operation of the software, the data from the point processing, curve and surface fitting, editing and quality. In the aspects of evaluation, processing and engineering analysis, the reverse engineering function of commercial CAD/CAM software is compared and evaluated. The literature is based on the surface modeling technology in reverse engineering, and the commercial reverse software (module) is analyzed. Whether it is a dedicated reverse software or a forward CAD/CAM software that provides a reverse module, the entire reverse engineering CAD model construction does not have excellent and ideal general processing capabilities, and the current reverse CAD modeling. In combination with the reverse characteristics of different needs in practice, special reverse modeling software is provided on the basis of forward CAD software. Processing method popular.
2. Application examples
The process of constructing the surface model of the car surface in Imageware is as follows: Firstly, the point cloud data processing function of I}nagew is used to construct the feature line to segment the point cloud data. Reuse image. The facet function, based on the feature line and the point cloud of the slice, constructs the final surface model.
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Flange Nut
Hebei Qianmu Fastener Manufacturing Co., Ltd
Flange Nut
Hebei Qianmu Fastener Manufacturing Co., Ltd , https://www.qmjgjfasteners.com