What is reverse engineering 3D modeling? Are reverse engineering and 3D modeling one concept or different concepts? The concept of reverse engineering (RE) is a description of the product design process.
3D Reverse Engineering: Process, Applications, Development, Advantages & Disadvantages
In the general concept of engineers and technicians, the product design process is a process from scratch, that is, designers first conceive the shape, performance and approximate technical parameters of the product in their brain, then establish the three-dimensional digital model of the product by drawing drawings, and finally transfer the model into the manufacturing process to complete the whole design and manufacturing cycle of the product. Such a product design process is called “forward design” process. Reverse engineering product design can be regarded as a process of “from being to being”. In short, reverse engineering product design is the process of backward deriving product design data (including design drawings or digital models) according to the existing product model. In this sense, reverse engineering has been applied in industrial design for a long time.
The hull lofting design commonly used in the early shipbuilding industry is a good example of reverse engineering. With the wide application of computer technology in manufacturing field, especially the rapid development of digital measurement technology, product modeling technology based on measurement data has become the main object of reverse engineering technology. The spatial data of object surface obtained by digital measuring equipment (such as, laser measuring equipment, etc.) needs to use reverse engineering technology to establish the three-dimensional model of the product, and then use cam system to complete the manufacturing of the product.
Therefore, reverse engineering technology can be regarded as the general name of relevant digital technology and geometric modeling technology to transform product samples into three-dimensional models. The implementation process of reverse engineering is a collaborative process of multiple fields and disciplines. The whole implementation process of reverse engineering includes the process from measurement data acquisition and processing to conventional CAD / CAM system, and finally integrated with product data management system (PDM system). The implementation of the project requires a high degree of coordination and integration of personnel and technology.
Implementation principle of reverse engineering
The role of reverse engineering in CAD/ CAM system reverse engineering technology is not an isolated technology. It is inextricably linked with measurement technology and the existing CAD / CAM system. However, in the process of practical application, because most engineering and technical personnel do not understand the reverse engineering technology enough, they equate the reverse engineering technology with the existing one, and require the reverse engineering technology with the technical level of the existing CAD / CAM system, which often leads to people’s mistrust and misunderstanding of the reverse engineering technology. From a theoretical point of view, reverse engineering technology can reconstruct a three-dimensional model fully compatible with the existing CAD / CAM system according to the product measurement data, which is the ultimate goal of reverse engineering technology. However, we should see that the current technology, including engineering and pure theory (such as surface modeling theory), can not meet this requirement.
Especially for the popular large-scale “point cloud”, it is far from being directly applied in CAD system. Therefore, we believe that the relationship between the current reverse engineering CAD technology and the existing CAD / CAM system can only be a complementary relationship. After decades of development, the existing CAD / CAM system has been very mature in both theory and practical application. In this case, the existing CAD / CAM system will not and cannot change the bottom layer of the system in order to meet the special requirements of reverse engineering modeling.
On the other hand, a large number of modeling methods used in reverse engineering technology can learn from the existing CAD / CAM system without building a new platform. Based on this analysis, we believe that reverse engineering technology is in a subordinate and auxiliary modeling position in the whole manufacturing system chain. Reverse engineering technology can make use of the existing CAD / CAM system to help it realize the work that it cannot complete. With this understanding, we can understand why reverse engineering technology (including corresponding software) is not always the mainstream in the market, and most CAD / CAM systems contain reverse engineering modules or third-party software packages.
Application Of Reverse Engineering
Application of reverse engineering technology in mold industry from the concept and technical characteristics of reverse engineering, it can be seen that the application fields of reverse engineering are mainly mold related industries such as aircraft, automobiles, toys and household appliances. In recent years, with the development of biology and material technology, reverse engineering technology has also been applied in medical fields such as artificial biological bones. But its main application field is still in the mold industry. Because it is often necessary to repeatedly test punch and modify the die surface in the process of die manufacturing. If the mold that finally meets the requirements is measured and its digital model is obtained, this standby digital model can be used to generate the processing program when manufacturing the mold repeatedly, which can greatly improve the mold and reduce the mold manufacturing cost.
Reverse engineering technology, especially in areas and enterprises producing various automobile and toy accessories, has a very broad application prospect. These regions and enterprises often need to manufacture molds or directly process products according to the samples provided by customers. In these enterprises, measuring equipment and CAD / CAM system are essential, but the application of reverse engineering technology is not perfect, which seriously affects the accuracy of products and production cycle. Therefore, the combination of reverse engineering technology and CAD / CAM system is of great significance to the application of these enterprises. On the one hand, various mold enterprises welcome reverse engineering technology, but on the other hand, they suffer from the lack of necessary guidance and appropriate software products. This situation seriously restricts the promotion of reverse engineering technology in the mold industry.
Reverse engineering software the implementation of reverse engineering needs the support of reverse engineering software.
The main function of reverse engineering software is to receive product data from measuring equipment, obtain high-quality curve or surface models through a series of editing operations, and transmit these curve and surface data to the existing CAD / CAM systems through standard data format, so as to complete the final product modeling in these systems. Because it can not fully meet the needs of users for product modeling, reverse engineering is difficult to compete with the existing mainstream CAD / CAM systems, such as CATIA, UG and SolidWorks.
Many reverse engineering software become the third-party software of these CAD / CAM systems. For example, UG adopts Imageware as the software to complete reverse engineering modeling in UG series products, and ICEM surf as the supporting software of reverse engineering module. In addition, there are some independent reverse engineering software, such as Geomagic, which generally have diversified functions. For example, in addition to geometry, Geomagic can also process the modeling of tomographic interface data represented by CT and MRI data, so that the software has considerable competitiveness in the field of medical imaging.
In addition, as a part of the whole series of software products, some reverse engineering software, whether data model or geometric engine, are consistent with other components in the series of products. The advantage of this is that the model generated by reverse engineering software can directly enter CAD or cam module to realize the seamless integration of data. The representative of this kind of software is CopyCAD of Delcam company.
Comprehensive application of reverse engineering and rapid prototyping technology
The comprehensive application research of reverse engineering and rapid prototyping technology is the comprehensive application of rapid prototyping technology in the process of three-dimensional data measurement, data preprocessing, data reconstruction of three-dimensional model, data error analysis and corresponding format output of data, including the selection of rapid prototyping methods and equipment, data format conversion, rapid prototyping processing and precision control, This paper discusses the mutual influence and restriction in the process of comprehensive application.
Development trend of reverse engineering technology
There should be no mainstream products now. Each has its own advantages and disadvantages and its own market. For measurement and accuracy, it’s three coordinates. There’s no comparison with others, but it’s more difficult in work efficiency and maintenance. The market of laser scanning and photo scanning is relatively close. Laser has price advantage. Photo taking is a new generation of scanning products. The price will be higher and the average level of efficiency and scanning quality will be strong, but the price will be higher than laser. Look at your affordability and other considerations.
What are the methods of data measurement in reverse engineering, and what are the advantages and disadvantages
In the of products, the acquisition methods of product three-dimensional data can be basically divided into two categories: contact and non-contact. Because these two methods have their own advantages and disadvantages, and their combination can realize potential complementarity and overcome various difficulties in measurement, many reverse equipment manufacturers have developed reverse equipment with contact and non-contact scanning functions. It is a kind of contact measuring equipment. It has the advantages of high precision and good repeatability. Its disadvantages are slow speed and low efficiency.
The non-contact method uses a physical phenomenon that interacts with the object surface to obtain its three-dimensional information, such as light, electromagnetism and so on.
The non-contact method has the advantages of non-contact in the measurement process and rapid measurement. Its disadvantage is that it has strict requirements for the measured object materials. For example, when using laser measurement, the measured object materials are required not to be transparent and the surface is not too bright, and there are certain errors in the acquisition of straight wall and slope data. Data acquisition and processing in reverse engineering the amount of measurement data in reverse engineering is large, the scanned data points can reach hundreds of thousands, and the scanned data points are discrete. In order to effectively use these measurement data for CAD modeling, it is necessary to deal with the data cloud.
1. Data acquisition the process of data acquisition is: machine initialization – set the scanning datum (including z plane, coordinate axis, datum point, etc.) according to the object to be scanned – set and scan the 2D contour (this step can be selected according to the actual situation) – set the 3D surface scanning according to the 2D contour or coordinate area (including scanning direction and step, 3D space extreme value, allowable minimum error and chord error, probe radius, scanning speed, etc.) – data acquisition.
2. Data processing the purpose of data processing is to obtain correct data information, generate data files in corresponding formats (such as IGS, DXF, VDA, UG format, Cimatron format, format, etc.) and exchange data with famous brands such as UGII, surface, CATIA, etc., so as to use them for 3D model reconstruction.
In data processing, problems such as shape deformation, reduced accuracy and insufficient data points should be avoided. Generally, the following aspects should be carried out:
Generation of compensation point for contact scanning, since the measurement data obtained from the scanner does not really represent the coordinates of the contact point, but reflects the value of the center or top of the probe, these data should be compensated and converted into the coordinate value of the measured object surface. For the generation of compensation points, it is necessary to calculate the standard points first. Because there is no mathematical expression formula of the surface, the standard points cannot be calculated by the usual method. At present, a special algorithm has been developed to obtain the approximate standard value within the specified tolerance range.
Noise point deletion in the process of reverse engineering measurement, affected by the scanning measurement method, the type of measured object material, the accuracy of equipment and other factors, it is very easy to cause the generation of measurement data error points. This kind of error point is traditionally called noise point. In the first step of data processing, we should first use the noise point removal function provided by the system to select the appropriate denoising accuracy to remove the redundant error points and ensure the accuracy of the measured data.
Data point refinement in CAD system, it is necessary to carry out curve construction, curve fairing, surface reconstruction, surface smoothing, surface stitching and so on. Before these operations, set the appropriate end distance of the section and the distance between two adjacent data points according to the shape and volt characteristics of each part of the measured object, output the data file in the appropriate format by using the CAD data output function in the system, and then delete and splice the data points, so as to ensure that there are fewer data points where the curvature of the measured object is large, There are more data points in the places with small curvature and complex curvature.
Data acquisition methods and skills in physical measurement, various complex shapes will be encountered. In order to ensure the accuracy of the measured data and the integrity of the measured shape, the measurement method and measurement tooling are the key to data acquisition. The cylinder is the core component of gasoline engine. The accuracy of its shape and size directly affects the power of gasoline engine and the degree of environmental pollution.
According to the characteristics of gasoline engine cylinder, it is divided into two parts for scanning, namely airway and combustion chamber. For the combustion chamber, the cylinder can be scanned directly with the contact probe after the cylinder is properly cut and divided by the wire cutting machine; The shape of the airway is extremely complex and there are many details. Many details cannot be reached by the contact probe, so that the contact probe cannot scan. For this reason, the mold turning measurement method is adopted for the airway part, the airway of the cylinder is turned with silica gel, gypsum, resin and other materials, and then the contact probe is used to scan the turned model. Due to the excellent filling ability of Sixin, gypsum and resin and small deformation after filling, the shape of the original airway can be copied better.
Therefore, scanning the reproduced model can ensure the accuracy of scanning. Through repeated experiments, it is found that the turnover accuracy of gypsum in all materials is the highest, and the surface quality of the model is close to that of the original. When scanning with the contact probe, the contact probe has a certain contact force, and the contact probe (especially the small-diameter probe) can scratch the gypsum model, thus affecting the scanning accuracy. In order to ensure the scanning accuracy, the gypsum model is hardened with special adhesive (such as:). The selected adhesive should have two characteristics: one is that the adhesive can form a certain thickness of penetration layer on the surface of gypsum model and solidify the gypsum surface; Second, after the adhesive is cured, the surface of the gypsum model should be kept smooth to ensure the scanning accuracy.