法年研究逆向工程中的应用工程技术[PDF]@中英文翻译@外文翻译

Journal of Materials Processing Technology 139 (2003) 472475Research into the engineering application of reverseengineering technologyYu ZhangCIMS Application and Research Center, School of Mechanical and Automation Engineering, Kunming University ofScience and Technology, Kunming 650093, Yunnan, PR ChinaAbstractBased on previous research on reverse engineering (RE) technology, the engineering application of RE is explored in this paper. Theapplication environment of RE is built with coordinate measurement machine (CMM) and CAD/CAM software. Taking a core die of theinlet of a diesel engine as an example, this paper describes the processes of RE, from object digitization, CAD model reconstruction toNC machining. Measurement data are acquired by scanning the physical object using a three-dimensional CMM. Through processing ofmeasurement data, the authors succeed in creating a CAD model of the die and machining the die, gaining a good result. 2003 Elsevier Science B.V. All rights reserved.Keywords: Reverse engineering; Product development; CAD/CAM1. IntroductionNowadays, competitive pressure has reached the point,where rapid product design and optimization need to beembraced within the product development cycle. A shortlead-time in product development is strongly demanded tosatisfy needs, resulting from the globalization of manufac-turing activities and the changes in market requirements. Inengineering areas such as aerospace, automotives, shipbuild-ing and medicine, it is difficult to create a CAD model ofan existing product that has a free-form surface or a sculp-tured surface. In these cases, reverse engineering (RE) is anefficient approach to significantly reduce the product devel-opment cycle.RE refers to the processes in which designers acquire adesign concept of a product from digitization of a physi-cal model, and create the CAD model to realize approx-imation to the physical model: the model created can bereused, modified and optimized 5. By RE technology, thegeometric shape of an existing part or product is measured.Based on this measurement data a complete and complexCAD model is created. RE has two key technologies, i.e.digitization of a physical model and creation of its CADmodel.E-mail address: (Y. Zhang).2. Working processes of REDiffering from the traditional design idea and method, REtechnology enables one to start a design from an existingproduct model by combining computer technology, measure-ment technology and CAD/CAM technology. RE has beenof interest in many different branches such as automotives,shipbuilding, electronics, and medicine. It is often used incases such as the following 3:(i) Where a prototype of the final product has been mod-eled manually and therefore no CAD model of theprototype exists, e.g. clay model in automotive in-dustry.(ii) Where a CAD is introduced in a company and all exist-ing products must be modeled in order to have a fullydigital archive. Particularly, the CAD model of a com-plex shaped part is modeled because it is difficult tocreate its CAD model directly.(iii) Where complex shaped parts must be inspected andtherefore the RE model created will be compared to anexisting CAD model.The RE process can principally be seen as a process chainthat is composed of three main operations as follows 5:(i) Digitization of the object: The three-dimensional shapeof the product is acquired by any appropriate measure-ment method.0924-0136/03/$ see front matter 2003 Elsevier Science B.V. All rights reserved.doi:10.1016/S0924-0136(03)00513-2Y. Zhang / Journal of Materials Processing Technology 139 (2003) 472475 473Fig. 1. Working processes of RE.(ii) Processing of measured data: The three-dimensionaldata acquired is processed in order to fulfill the require-ments of the following operation.(iii) Creation of a CAD model: A complete CAD modelof the product must be built in order to represent allrelevant data of the product.Fig. 1 shows the working processes of RE. The wholeprocess of RE should be computer aided.3. Engineering application of REBased on principle of RE technology mentioned above,the authors applied RE technology in the design and manu-facturing of the die of a diesel engine. Taking the core dieof the inlet of a diesel engine as an example, this paperdescribes the RE processes, from object digitization, CADmodel reconstruction to NC machining.The inlet is the key part in a diesel engine. It influences thecharacteristic of the diesel engine to a great extent. Becausethe inlet has very complex shape (see Fig. 2), it is difficult tocreate a digital model of the inlet, as well as to manufacturethe core die of the inlet. The authors have therefore takenit as an example to research the engineering application ofRE technology.Fig. 2. The 3D model of the inlet.3.1. Environment of REThe environment of RE is a local area network (LAN),which is built with two work-stations, two NT work-stations,three sets of PC, a coordinate measurement machine (CMM)and three NC machines. The hardware platform uses leveldisposition of work-stations and PCs. The main applicationsoftware utilized is the Unigraphics CAD/CAE/CAM inte-grated system and KUM measurement software providedby the zess company. The operating systems utilized areHP-UX 10.2 on work-stations and Windows NT on PCs.Fig. 3 shows the environment of RE. With computer net-work, the RE processes, i.e. object digitization, processingof measurement data, creation of a CAD model, and NCmachining, are realized in a integrated environment on com-puters.Fig. 3. Environment of RE.474 Y. Zhang / Journal of Materials Processing Technology 139 (2003) 472475Fig. 4. NC measurement and surface reconstruction of the core die of the inlet.3.2. Digitization of the dieGenerally, the methods of measurement of three-dimensional geometry product data are divided into twoclasses, i.e. tactile measurement and optical measurement.The CMM is a general tactile measurement device, and isbeing widely used in industrial enterprises 1,2. The au-thors measure the geometric shape of the die and acquiremeasurement data using CMM and KUM measurementsoftware with a linear scan mode. The physical model ofthe die is scanned on CMM using a 5 mm diameter probewith a step-over across the model of 5 mm in the first areaand 1 mm in the complex area (see Fig. 4a). The number ofmeasurement points is automatically determined by CMMaccording to the curvature change of the surface measuredon the tactile point. In order to avoid track slip, the probestarts to measure the surface at 4 mm away from the bound-ary of the surface being measured. On average, there areabout 1600 measurement points acquired for each scancurve.3.3. Processing of measurement dataThe result of a mechanical tracing process is a structuredpoint sequences with a large number of points and a linestructure 4. The output data of the CMM are coordinatevalues of the center of the probe and normal vectors in theX, Y and Z direction at the position of the tactile point. Addi-tionally, the output format of the measurement data does notaccord with the demands of the creation of a CAD model.Thus one must process the measurement data. The authorhave self-developed a program to realize the transformationof the format of the measurement data.First, the format of the measurement data output must betransformed into a format that can be accepted by Unigraph-ics software. Then the measurement data out of the controltolerance must be filtered out and interactively processed ina visualized way. The data processed can be used directlyfor the creation of a CAD model of the die.3.4. Creation of a CAD model of dieThe CAD model is created directly from measurementdata using Unigraphics CAD/CAE/CAM software after pro-cessing of measurement data and transforming of the dataformat.There are two ways in the creation of the CAD modelfrom measurement data using free-form feature modeling.One is called the curve mode. In this way, the constructioncurves are generated from measurement data first, and thenthe surface can be created through the construction curvemesh generated. Another one is called the surface mode, thesurface is generated directly from measurement data 2.Because the measurement data output are the coordinatevalues of the center of the probe, the surface generated frommeasurement data is a surface offset for distance, whichequals the radius of the probe, away from actual surfacemeasured. Thus one has to offset this surface.The surface generated is analyzed through a shading sur-face and surface analysis function in order to check its con-tinuity and smoothness, as well as the errors between thesurface generated and the measurement points. The maxi-mum error is 0.2 mm, which is acceptable.3.5. NC machining of the dieAfter the CAD model of the die is created completely,one can determine the NC machining process planning andgenerate the cutter location for a manufacturing applica-tion. Further machining codes are generated through NCpost-processing. Finally, the die is machined by an NC ma-chine tool using its CAD model created.Fig. 4 shows the results of NC measurement and surfacereconstruction of the core die of the inlet, whilst Fig. 5 showsthe generated CAD model of the core die of the inlet.Fig. 5. The generated CAD model of the core die of the inlet.Y. Zhang / Journal of Materials Processing Technology 139 (2003) 472475 4754. ConclusionBased on previous research on RE technology, the authorshave explored the engineering application of RE technol-ogy in the design and manufacturing of a complex product.Taking a die of the inlet of a diesel engine as an example,they have described the whole processes, from object digi-tization, CAD model reconstruction to NC machining, andhave gained a good result. RE is an efficient approach tosignificantly reduce the product development cycle and en-sure product quality kin the design and manufacturing