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Reverse Engineering in the application of product design
The application that is in expatiate contrary engineering in the product design with develop the term, effectively of solution shape design with follow-up engineering design, manufacturing link mutually the problem that become disjointed, put forward on sowing in adopt in the product design process the Pro/Designer have no with Pro/Engineer to sew to connect method, design for the industry product shape with the in the late engineering makes of linking up and developing a new path, the process of its design process is a line of for valid measure that product design systematize to provide, from but shortened the product design development, period, realizes the product shape design of systematize.
1 reverse engineering of the content and scope of application
With the development of computer technology, CAD technology has become a product design staff an important tool for research and development, of which three-dimensional modeling technology has been widely used in manufacturing products and mould design, program evaluation, automated processing and management of all aspects of maintenance. In the actual development of the manufacturing process, design staff to receive technical information may be all kinds of data types of three-dimensional model, but a lot of time, it is from the upstream manufacturers have the physical product model. Designers need to adopt a certain way, this kind of information into the CAD model, which applied to reverse engineering (Reverse Engineering). The so-called reverse engineering, refers to a means of measuring the physical model or measured, according to survey data 3D modeling methods through physical reconstruction of the CAD model of the process.
Reverse engineering technology and traditional design is very positive difference. And reverse engineering is starting from a prototype and then obtain three-dimensional digital model of the product, make it possible to further use of CAD / ACE / CAM and CIMS and other advanced technology to process.
In general, reverse engineering products, including the shape reverse, the summation of the anti-reverse, and several other materials, in the industrial field in the practical application, including the following:
(1) the design of new parts, mainly for the product imitation or modified design.
(2) Have been parts of the copy, reproduce the original intent of the design of the products.
(3) damaged or worn parts of the reduction.
(4) digital model of detection, for example, the deformation of product testing, welding quality, as well as a model for comparison.
Reverse engineering technology for the rapid design and manufacturing provided a good technical support ，it has become an important manufacturing information transmission and concise way. And the traditional product design, market research in general, the development requirements table after the plane started to sketch the idea of forming a little integrity of the program, started drawing three-dimensional map, then completely stereotyped as required draw results map, three view or create a simple model. In the process of design, engineering and technical personnel needs, product modeling staff and workers work together, using samples physical model to express the idea of designers, but for every kind of a program have produced samples, to pay a lot of labor, There is a low accuracy, modify adjustment difficulties, the design cycle length and cost of higher issue.
2 CAD technology in product design issues.
The development of computer technology, brought about the third wave of technological revolution, computer-aided design (computer aided design, referred to CAD) technology is the computer industry in the area of application of the most active one. It sets numerical simulation, geometric model of processing, graphics, database management systems, and other aspects of technology integration, the abstract, flat, separation of the specific object of design, visualization, it can through the "virtual reality" technology The product of the shape, texture, color, and even brought process demonstrated, and can product design process, through data management, and systematic, standardized, and this is industrial design and integration of CAD technology will inevitably the basis.
Reverse engineering software implementation of the conditions
At present, relatively commonly used generic reverse engineering software Surfacer, Delcam. Cimatron to Strim. The specific application of reverse engineering system is mainly the following: Evans for the development of machine parts to identify the reverse engineering system; Dvorak development of the imitation parts of the old reverse engineering system: HHDanzdeCNC CMM system. These systems to reverse the practical problems in the design process, greatly facilitate the design staff. Besides,
Some large CAD software is gradually provided for reverse engineering design module. Such as Pro / E and the ICEM Surf Pro / SCANTOOLS module can accept and orderly points (measurement line), can also accept the point cloud data. UG as other software, with versions of the increase, reverse engineering module is gradually enriched up. These software reverse engineering for the development of the implementation of the software conditions. These software and despite some relatively high-end design software, already the product of complex design and modeling exaggerated features, but the art designers to master and use of such software, so far is not an easy task. So in the structural design of the major designers who are mechanical engineers, design and way of thinking completely different from the modeling designer, their thinking is a fully consistent with the design of mechanical design standard way of thinking.
So, how will the two designs in the design of the products are in combination, and receive better integrate and better processing from design to completion of the conversion process ?of our product design to consider the issue.
3 product design - CAD reverse engineering technology
(1) Pre / E of the design parameters of the project
Parametric Design (Parametric) (also known as drive size Dimension-Driven) is in the practical application of CAD technology in the subject, it will not only CAD system is an interactive graphics capabilities, but also with automatic mapping capabilities. Currently, it is the application of CAD technology in the field of a major, Judai further study the issue. Use of the design parameters of the development of the means for product design system will enable designers from the large number of heavy and trivial mapping out relief work, can greatly improve the design speed, and reduce the storage of information. Parametric design, the key is to extract the geometric constraints and expression, and the parameters of constraint solving geometric model of the structure. 1988, the United States launched the first technology companies parameters of the design parameters of CAD system Pre / Engineer (referred to Pre / E) to give full expression to their common in many parts, components, the simple design of the advantages. Its main features are: Feature-based, full-size constraints, all data related to the size of drive to amend the design.
So that we can use PTC: the company's industrial design software Pre / Designer (referred to Pre / D) of surface design, the Pre / D and Pre / E is using the same database, is the seamless connection between the two, thus Design modeling designers and structural engineers can better collaboration
(2) Pre / D surface design capabilities for industrial designers and those who want to build surface model for the engineering staff, Pre / I] is precisely the tools they need, Pre / D can build high-quality free surface model, and Can easily switch to the other based on the manufacturing engineering CAD system. Pre / D to create a true and accurate geometry, the use of the more easily it can create a model to shorten the design cycle. Pre able to use visual aesthetic requirements and die manufacturing process in the engineering requirements combined with a very good, this point in the creation of free surface model now in the process was particularly notable.
(3) Pre / D and Pre / E of the rumored pumped Pre / Designer and Pre / Engineer data exchange between
There are two ways: one is with the Pre / Engineer direct exchange of data and another is a way to document and the Pre / Engineer data exchange.
(4) three-dimensional modeling complex product design for the CAD application form decorative strong, especially products containing complex surface, you can use the Pre / D and Pre / E combination, modeling designer in the Pre / D inside do ID, so Surface modeling, directly from the Pre / I] started in the Pre / E, the data lead to the Pre / E designers from the structural design of the structure of the entire design process of structural design or even all done, the customer's request or designer Local to the program to make changes, then only in the Pre / D changes inside, to better keep good again after the original name given to Pre / E, then Pre / E has also been changed, but do not have to redo the structure (of course, to amend For structural conditions for the existence of, the father of characteristics that it will not be a problem).
Over the years, the development of the traditional industrial products are to follow strict form of research and development process: from the idea of demand for products, features and specifications of the expected target identification, then to the various components for the design, manufacture, assembly, testing performance. Each component is retaining the original design, the design usually to CA]] in the form of documents to save. This development model known as "scheduled mode" (Pre-scriptive Model), the development of such projects also known as "positive work" (Forward Engineering). However, with the level of industrial technology upgrading and improving the standard of living, Any GM products in the consumer demand for high-quality, functional needs of the market has ceased to be competitive to win the only condition. Products not only to advanced features, and more focused on modeling the appearance of products, this is not the traditional mechanical engineers to the competent. Designers to shape the way through the manual model, for example: wax model, wood model, cast, clay model, engineering plastics, etc.-and then three-dimensional measurement methods generate free surface of the CAD file, which is the so-called "Reverse engineering" (Reverse Engineering, RE). Then put in front of the designer and manufacturer of the physical kind, will need physical model into a CAD model, as product information model is the realization of CAD / CAM technology seamlessly create the key.
Reverse Engineering (Reverse Engineering) in the absence of design drawings or design drawings incomplete and not the CAD model and in accordance with the existing parts of the model (or sludge prototype model), the use of digital technology and CAD technology re-structure the CAD model And cloning to create physical products or processes. Project is positive from the CAD model to the physical model into the process, and reverse engineering is from the physical model to the CAD model of the transformation process, both the design process just the opposite, reverse engineering and forward the application of different areas, with the Digital measurement of the rapid development of technology, reverse engineering in the manufacturing sector of the increasingly widespread and mature, on the reverse engineering of CAD has also become one of the hot areas of research.
4 modeling technology, including reverse engineering from the measurement data to the CAD model of a set of technical steps can be summed up in the following several aspects of key technologies:
(1) measurement data processing - As the number of measurement equipment by the wider use of massive data point (in millions of orders of magnitude) access to a very easy matter. 1000000 data regardless of the person or read data, and other aspects of reconstruction model for us is very inconvenient, and in need of reconstruction CAD model before the measurement data pretreatment.
(2) grid model construction – three grid model of reverse engineering is commonly used in the model that way. three grid model can easily express complex shape of the object's surface, while grid model for the reconstruction surface model is a very good foundation model.
(3) basic model surface structure - reverse engineering modeling is the ultimate goal of universal CAD system to provide a valuable basic surface model, in the final completion of GM products in the CAD system model of reconstruction. So reverse engineering of the basic surface model for the Reconstruction of high-quality reconstruction of the CAD model is very important.
(4) model of quality - reverse engineering model is based on measurement data in the reconstruction CAD model. In the reconstruction process because of the various data (such as compression) so that data back to the inevitable errors. The ultimate CAI] model is in error to allow the evaluation of the accuracy of reconstruction is an important indicator of the quality of model one.
Following this will be a few aspects of the systems described.
4.1 Data pretreatment technology
Now with three-dimensional scanning equipment development, the measurement data are also increasing the number of points, with millions of data points measured in the paper is already very common. So many data points, the benefits are obvious, able to model all the characteristics of the small acquisition, but processing system, it is a lot of obstacles. This will not only greatly increase the system's capacity, but also reduces efficiency, which will affect the whole process of reverse engineering modeling. Therefore, the measurement data pretreatment reverse engineering modeling now become an important aspect of technology. Survey data preprocessing, in addition to the large amounts of data compression, but also to remove the noise generated in the scan data. No matter how advanced measuring equipment, the impact of noise is always inevitable. Although not much noise points, but the impact of noise or great, the work of removing the noise generated model can greatly improve the quality. Because the shape of certain models more complicated, often unable to get a scan all the data. In this way, a model of the measurement data have many pieces, so in model building, must be multi-block data connection, integration into a model. The process works in reverse as in the Register, that is re-positioning data.
4.2 grid model construction
Grid model in the reverse engineering of a wide range of applications. Measured data points we generally referred to as point cloud. Point cloud data does not include any topology information, in order to reconstruction surface model and rapid prototyping (Rapid Prototype Manufacture, RPM), and other processing needs we need to point cloud data constructed on the basis of triangular grid model. 1.30 Mesh topology contains a wealth of information that can be used, such as special Reconstruction of the levy, such as surface divided post-processing Club. grid can also show a real model of the shape, can achieve good visual effects. In addition, the triangle enough detailed grid can be directly used for processing parts. According to deal with the object and the use of different measuring techniques and tools, reverse engineering CAI] modeling content can be divided into two aspects: one is to examine the entire body of CAD modeling, the other to deal with a complex of the main characteristics of CAD surface modeling. It also determines the triangular grid model of the construction method has two main categories. The whole body of the CAI) modeling, mainly in the field of medical image visualization applications. This kind of research more and relatively deep, is generally used CI, access to facilities such as the organ section contour, and then from these contour triangular grid structure, and its main difficulty is the handling of the "bifurcation" and "Holes" The model. According outline cross-section of this structure of the triangular grid model algorithm is now very mature and can achieve high efficiency. Modeling a large number of mechanical parts, are generally dealt with rehabilitation of the surface of the CAD modeling. Many aspects of this method, but the effect is not very satisfactory, algorithms are from a seed triangle, traverse around the point, to build triangular grid. Now is the algorithm needs to be raised the efficiency and quality of the grid. Most of the triangulation method is not the original data points of the interpolation algorithm, which caused a triangular grid model with the original data points of error, this error will be accumulated up to the surface reconstruction.
4.3 Surface Reconstruction
Free surface model in reverse engineering products play an important role modeling, because of free-form shape of a flexible, in aviation, aerospace, automotive, mould and other industries a large number of applications, at the same time, these industries are also reverse engineering applications in important areas, based on free Surface Reconstruction has been a model of reverse engineering CAD important area of research. Surface Reconstruction (also known as surface modeling) through modeling can be separated from the measurement data for changes in the reconstruction surface, surface fitting interpolation, including surface and surface approximation, surface Interpolation demands Interpolation the surface strictly Through the data points; surface approximation is based on the data structure of a discrete surface, so that these points in some sense the most close to the surface by the structure. Based on different forms of surface topology, the common surface reconstruction in two ways. Bezier surface to 1.30 based on the tripartite domain surface construction method, and B-spline [101 NURBS surface and based on the four sides domain surface constructed. Based on the 1.30 Bezier surface of the triangular domain surface constructed. Dealing with the basic idea is to be dealt with the original number considered as a whole. First constructed in accordance with point cloud summer triangular grid and building a triangular grid, the use of 1.30 Bezier surface in the grid on the basis of constructing smooth surface [121. 1.30 Bezier surface interpolation in the triangular grid of each triangle on the initial structure of the three variables 1.30 Bezier patch, and then each triangle patch up to four bands, and then each patch for CT (clough - tocher) segmentation, and then adjust each patch of the control points, so that the entire surface to a combination of geometric order (GCI) a row.
4.4 Based on the characteristics of the model reconstruction
Since reverse engineering is the subject of dealing with three-dimensional space data, how the reconstruction process in the surface model and accurately reproduce the characteristics of products, reverse engineering is the product model can comprehensively CAD system in general an important symbol. Now the reverse engineering, especially in the Reconstruction of general machinery parts, one after another to automatically extract model characteristics. Not only automatically extracted from the characteristics of products, such as bevel, the transition surface, Geng Shiba based on the characteristics of the thinking of food to the various aspects of reverse engineering, reverse engineering feature extraction as a supplementary means of modeling. In the reconstruction of the main features of the redevelopment There are two