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The application of reverse engineering technology

imitation and imitation have become the fixed production mode of some enterprises in China. The imitation of popular products in the market is common, and the wide application of reverse engineering plays an important role in it. Therefore, some people often associate reverse engineering with illegal imitation, and even raise legal issues such as intellectual property protection. In fact, reverse engineering represents a very efficient product design idea and method. Starting from the concept of reverse engineering design, this paper expounds the concept of reverse engineering in modern manufacturing industry and the role of reverse engineering in mold manufacturing and other industries. This paper has certain significance for us to correctly understand reverse engineering technology

I. Introduction

in foreign countries, reverse engineering has been introduced into the design and development of new products as an advanced design method. Many enterprises in China also use reverse engineering technology to improve their competitors' products to avoid the difficult prototype design stage, which is a product redesign process. The so-called product redesign is to observe and test a certain product, initialize it, and then disassemble the product to analyze the composition, function, assembly tolerance and manufacturing process of individual parts one by one. The purpose of these works is to fully understand the product manufacturing process, and on this basis, optimize and design a better product at the subsystem and part level. Many engineering colleges in the United States have set up reverse engineering courses to teach students to use redesign instead of prototype design as a way to solve design problems. In recent years, reverse engineering technology has been increasingly used in the fields of automobile, electronic products and so on, partially replacing the prototype design method used for many years

II. The concept of reverse engineering

Reverse Engineering (RE) is a description of the product design process. In the general concept of engineering technicians, the product design process is a process from scratch: designers first conceive the product shape, performance and approximate technical parameters, and then use CAD technology to establish a three-dimensional digital model of the product, 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 can be called "positive design". Reverse engineering is a process from being to being. To put it simply, reverse engineering is a process that reversely deduces the design data (including design drawings or digital models) of products according to the existing product models

with the wide application of computer technology in the manufacturing field, especially the rapid development of digital measurement technology, product modeling technology based on measurement data has become the main focus of reverse engineering technology There is a protective cover around the experimental fixture of the reverse zigzag experimental machine. The spatial data of object surface obtained by digital measuring equipment (such as coordinate measuring machine, laser measuring equipment, etc.) need to be processed by reverse engineering technology to obtain the digital model of the product, and then transmitted to the cam system to complete the manufacturing of the product. Therefore, reverse engineering technology can be considered as the general term of "relevant digital technology and geometric model reconstruction technology for transforming product samples into CAD models"

the implementation process of reverse engineering is a collaborative process of multiple fields and disciplines. From Figure 1, we can see that the whole implementation process of reverse engineering includes the collection/processing of measurement data, the processing of cad/cam system and the integration into the product data management system. Therefore, reverse engineering is a multi domain and multi-disciplinary system engineering, and its implementation requires a high degree of coordination and integration of personnel and technology

III. application of reverse engineering in cad/cam system

reverse engineering technology is not isolated. It is inextricably linked with measurement technology and cad/cam technology

from a theoretical point of view, reverse engineering technology can establish a digital 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, with the current technology, including engineering and theoretical (such as surface modeling theory), it can not meet this requirement. Especially for the popular large-scale "point cloud" data modeling, it is far from being directly applied in CAD system

there are two methods to collect "point cloud" data: one is to use CMM to detect the part surface, and the other is to use laser scanner to scan the part surface. After the collected data is processed by cad/cam software, the digital model of the part and the CNC program for machining can be obtained. Figure 2 shows the point cloud diagram of sand mold exhaust duct of motorcycle engine measured by laser scanner

in practical work, the lacus150b laser scanner is used to collect millions of point data to form the outline of motorcycle engine sand mold exhaust duct, and then the surfacer reverse software is used to process from point to surface. Figure 3 shows the surface geometry of motorcycle engine sand mold exhaust duct generated by surfacer software

after data collection, users can use CAD software to speed up the process of reverse engineering. Ideally, CAD software can be used to:

■ input virtual geometric dimension data in any format

■ processing collected point data, sometimes even hundreds of millions of point data sequences

■ process the generated contour surface through modification and analysis

■ output the geometry to the next stage of processing

■ analyze the geometry and estimate the difference between the overall shape and the sample

the most important thing is that the software allows the user to display the workpiece in the form of three-dimensional perspective. It completely defines the shape of the workpiece, and does not require projection drawings from multiple perspectives. The designer can directly reprocess the surface contour, and the processing workers can use the electronic model to process the workpiece

the post-processing software shortens the time of reverse engineering by:

■ improving the quality of the surface by smoothing the continuous curve

■ saves the time to prepare processing documents

■ no prototype is required

■ use various analysis tools to improve product quality

it can be seen that using laser scanner to scan the data of sample collection points, and then using surfacer software to generate high-quality surfaces can save several weeks of development time compared with directly modeling surfaces in CAD system. In addition, the geometric data collected by the laser scanner can be used to generate files that conform to the industrial standard formats, such as IGES, vda-fs, isog code, DXF and the specified ASCII, cad/cam formats. The analysis software package can support at least one of these formats

it is a time-consuming and expensive process to manufacture machining tools and inspect them. Surfacer software can quickly and completely inspect samples of various complex shapes, thus making this key processing process pipelined. The user can accurately adjust the scanning data by referring to the three-dimensional model, so as to evaluate the difference between the sample and the workpiece to be processed, calculate the relevant variables, and display them in the form of color charts, so as to make a clear and complete explanation for the geometric dimension verification

surfacer software rapid prototyping module (RPM) can quickly use digital data or other system surface geometry to generate prototype, thus shortening the digitization cycle of the actual prototype. The new RPM rapid tool has greatly improved the level of rapid prototyping technology. Therefore, the author believes that reverse engineering technology and cad/cam system complement each other. 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 underlying structure of the system 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 fully learn from the existing cad/cam system, and there is no need to build a new platform. Figure 4 shows the entity of sand mold inlet and exhaust ports of motorcycle engine generated by SolidWorks 3D software

based on this analysis, we believe that reverse engineering technology is in a subordinate and auxiliary modeling position in the whole manufacturing system chain. It can make use of the unique appearance of existing cad/ca to give packaging more sense of design and recognition M system, and help it achieve its own work. 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 include reverse engineering modules or third-party software packages

IV. reverse engineering application example

Figure 5 shows the pump body of a Japanese brand automobile. In order to enhance the competitiveness and save development time, a domestic enterprise plans to redesign the pump body on the basis of the original design. Reverse engineering technology plays an important role in it

in the actual work, the pump body is taken as the direct replication object. The main steps of the whole replication process are as follows:

(1) acquisition of the original data of the geometric surface of the sample part. A lacuse150b laser scanner is used to obtain point data directly from the model in the form of CCD (photoelectric coupling). (2) Filter and correct the collected data to eliminate the errors caused by various factors and surface defects of the sample parts in the measurement process, so as to obtain the data for constructing the original geometric model of the sample parts. (3) The necessary mathematical fitting of the measured data provides basic data for further verification of the design and final production process. (4) Because the sample pump body has been used for a long time, some changes have taken place. Therefore, on the basis of fully understanding the application functions of the parts, the original data of the sample parts are modified through redesign, and a new geometric digital model of the pump body parts is generated. (5) The generated digital model is used to make the prototype of parts. (6) Check the geometry and application function of the hand board parts. If the effect is not good, manually improve the hand board parts with industrial sludge according to the actual situation, and then re acquire the model data with laser scanning. Repeat steps (3) and (4). (7) Carry out the processing and manufacturing of duplicate parts and molds, and use CNC machine tools to process complex curved surfaces. (8) After the mold is tested, the geometry and application function of the pump body parts are inspected

in the whole replication process, in order to ensure the accuracy and accuracy of replication, the following aspects are considered in the replication process: (1) from the perspective of part application, the data acquisition and the whole redesign process of sample parts are comprehensively considered to improve the replication accuracy and the efficiency of data acquisition and processing. (2) By comprehensively considering the measurement process and manufacturing process, various errors caused by the manufacturing process can be effectively controlled, so as to improve the accuracy of the whole replication process. (3) Due to the complexity of the sample parts, the inspection of the copied parts is a link that should be paid enough attention in the whole reverse engineering, and it is the key to success. (4) Only by fully understanding the working environment and functions of sample parts can we learn advanced things in the process of replication, improve and enrich ourselves

Figure 5 shows how to use surface after scanning with lacuse150b laser scanner

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