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Automated design system for drawing diesBor-Tsuen Lin*, Shih-Hsin HsuDept. of Mechanical and Automation Engineering, National Kaohsiung First University of Science and Technology,Kaohsiung 824, Taiwan, ROCAbstractThis paper describes an automated design system for drawing dies. Taking advantage of pre-built design knowledge base and data-base, this system is able to output designs of the main components of a drawing die, such as upper dies, lower dies and blank holders,upon users input of design information of blank lines, die faces, punch open lines, press data, and types of subcomponents such ashooks, guides, and stopper seats. This die design system is built on top of CATIA V5, and makes use of its built-in modules, includingPart Design, Automation and Scripting, and Knowledge Advisor. Our system also includes an inference engine, and user interfaces. Weuse drawing dies for trunk lid outer panels and engine hood outer panels as concrete examples to showcase the power of our system.Experimental results show that our system can improve the design quality and reduce the design time and cost.? 2007 Elsevier Ltd. All rights reserved.Keywords: Drawing dies; Design system; CAD; Knowledge base; Parametric modeling1. IntroductionPress parts, such as frames, bodies, and doors, arewidely used in the automotive industry. In order for a man-ufacturer to survive in todays competitive market, thedevelopment process of a vehicle needs to be carried outin an efficient and effective way in order to meet customersexpectation. Die design is part of the critical path of theentire development process. There are three categories ofstamping dies, based on their functionalities: drawing dies,trimming dies, and bending dies. Since most stamping diesfor automotive sheet metals are big and complex, thestamping die design process is very time-consuming.Recently, as a result of the fast development of com-puter technology and of 3D CAD software, 3D CAD soft-ware has been widely used in designing drawing dies. Asolid model offers users an intuitive and concrete view ofthe die in design, which fundamentally reduced design time.However, most 3D CAD software only provides users withgeometric modeling functions for constructing a solidmodel, but fails to offer a powerful design knowledge base,which is essential to assist engineers in accomplishing thedesign task.As a result, the developments of automated, knowledgebase and intelligent design systems are studied by research-ers from around the world. Myung and Han (2001) devel-oped an expert system based on a configuration designmethod. This system allows users to design mechanicalproducts in a 3D environment. Roh and Lee (2006) pro-posed a hull structural modeling system for ship design,which was developed using C+ and built on top of 3DCAD software. Lee, Hsu, and Su (1999) developed a para-metric computer-aided die design system for cold forgingusing Auto-LISP. In order to make the modeling processmore efficient, Kong et al. (2003) developed a Windows-native 3D plastic injection mold design system based onSolid Works using Visual C+. Chu, Song, and Luo(2006) developed a Computer aided parametric design sys-tem for 3D tire mold production in CATIA using CAA.In the stamping die design area, Cheok and Nee (1998)developed a knowledge based strip layout design system inAutoCAD. Taking advantage of neural network and CAD0957-4174/$ - see front matter ? 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.eswa.2007.01.024*Corresponding author. Tel.: +886 76 6011000; fax: +886 7 6011066.E-mail addresses: bt_lin.tw (B.-T. Lin), u9314805.tw (S.-H. Hsu)./locate/eswaAvailable online at Expert Systems with Applications 34 (2008) 15861598Expert Systemswith Applicationssoftware, Pilani, Narasiman, Maiti, Singh, and Date (2004)proposeda methodforautomaticallygeneratinganoptimal die face design based on die face formabilityparameters. Ismail, Chen, and Hon (1996) developed a fea-ture-based progressive press tool using cheap CAD soft-ware. Based on sheet metal operations, Singh and Sekhou(1999) developed a punch machine selection expert system,which was built in AutoCAD and used AutoLISP. Tisza(1995) developed an expert system for detail process plan-ning of metal forming in AutoCAD.Though the design process of drawing dies is extremelycomplex and requires a great deal of professional knowl-edge, the purpose of this paper is to develop an automateddesign system for drawing dies. Taking advantage of well-organized die design knowledge base and database and anintegrated 3D CAD environment, our system is able to out-put designs of the main components of a drawing die, suchas upper dies, lower dies and blank holders, upon usersinput of design information of blank lines, die faces, punchopen lines (POL), press data, and types of subcomponentsU-grooveTriangle Rib GuideStopper Seat HookAuxiliary Plate Dieface Thickness Lower Die Size HookGuideCushion Pin Seat Stopper Seat Blank Holder Size Panel Guide Seat Avoid StructureSafety Area GuideSafety Area Cushion Pin HoleStopper Seat HookU-grooveKey-grooveAuxiliary Plate Triangle Rib Dieface ThicknessLower Die Size Avoid StructureFig. 1. Structure of main components for a drawing die. (a) Upper die. (b) Blank holder. (c) Lower die.B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615981587such as hooks, guides, and stopper seats. Experimentalresults show that our system can generate high qualitydesign of main components of a drawing die in an efficientway.2. Drawing die design2.1. Drawing die configurationDrawing is a process of cold-forming a flat precut metalblank into a hollow vessel without excessive wrinkling, thin-ning, or fracturing (Wick, Benedict, & Veilleux, 1984). Typ-ically, there are two sets of components in a drawing diedesign configuration. The first set of components is calledstandard components, and includes sliding panels, position-ing tools, and grip blocks, which can be ordered from thirdparty. The other set of components is called main compo-nents, and includes upper dies, lower dies, and blank hold-ers, as shown in Fig. 1. Main components differ from onestamping die to another. They are also very sensitive to cli-ents requirements. Therefore, this paper focuses on thedesign of main components of drawing die.POLBlank Line Binder Face Product form Draw Bead AddendumFig. 2. Graphic data of a drawing die for engine hood panel. (a) POL and blank line. (b) Dieface.Fig. 3. Design standards of bolt type hook.1588B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615982.2. Designing main components of drawing diesMost drawing dies are one-off. Therefore, designersmust take both the technical requirements and the budgetinto consideration in order to offer an optimal die designto meet clients expectations. Most die structures are verycomplex, and the design process of main components ofdrawing die consists of three stages: die design information,skeleton structure design, and feature structure design.Die design information is a minimum set of informationrequired by the design system, including the blanking lines,die faces, punch open lines, and press data. Blanking line is the around lines of raw materials.Although the shape of most raw materials is rectangu-lar, there are raw materials that are of irregular shapein order to save cost or to improve its formability. Thedimension of a die is determined based on its blank lines. Die faces and punch open lines: as shown in Fig. 2, diefaces include product forms, addendums, draw beads,and binder faces. The product forms are the ultimategoal of the stamping process, while the addendums, drawbeads, and binder faces. are used to facilitate the drawingprocess. Moreover, punch open lines divide the die faceinto two parts, which serve as the surface forms for thelower die and the blank holder, respectively. Press data is the press machine-related data that isrequired by the die design process, which includes theworking strokes of press machine, lower dead point ofUser Interface Graphic Data Interface Alphanumeric Data Interface Inference Coordinator Subcomponent Selector Shape Calculator Model Generator Inference Engine DatabaseSubcomponent Design Standards Press Machine SpecificationsKnowledge Base ProceduralKnowledgeHeuristicKnowledgeCATIA V5 Part Design Module CATIA V5 Knowledge Advisor Module CATIA V5 Automation & Scripting Module CAD Software Fig. 4. System structure.Die Structure AnalysisDesign Process StandardizationSample Die ConstructionVariable SettingsProgrammingInterface BuildingFig. 5. Procedures for constructing system.B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615981589the slider, size of the bolster, the dimension and positionof T slots, stroke of cushion pins, the diameter and posi-tion of cushion pin holes. T slots can be used as posi-tioning points. The purpose of cushion pin holes is toallow the cushion pins to push the sheet metal out ofthe die when the forming process is finished.Die skeleton design: in this stage, the major structures ofmain parts are determined, which includes size, the thick-ness of die face, avoid structure, panel guide seat and ribstructures for the upper die, lower die, and/or blank holder.Taking the design of rib structures as an example, itsdesign guidelines are given below. Spaces between any two ribs shall not exceed 300 mm. Ribs shall not be placed on the T slots of the bolster. Ribs must be placed under each stopping seat. Ribs shall not interference with any cushion pin holes.Following are the design specifications: The thickness of outer ribs and ribs for punch open linesis 40 mm. The thickness of inner ribs is 30 mm.Feature structure design: all supporting subcomponentsis determined in this stage, including guides, cushion pins,hooks, stopper seats, safety areas, U grooves, auxiliaryplates, triangle ribs and key grooves on the blank holder,lower die and/or upper die. Taking the design of blot typehooks as an example, its design guidelines are given below: Four hooks shall be placed on the upper and lower die,and blank holder. The moving stability of the die shall be taken into con-sideration. Therefore, hooks shall be placed on cornersof the part.DrawingDieLower Die POL Blank Line DiefaceBHUpper Die SkeletonStructureFunctionalStructureSkeleton StructureFunctionalStructureSkeleton StructureFunctionalStructureBH Size Dieface ThicknessAvoid Structure Panel Guide SeatRibLower Die Size Dieface ThicknessAvoid Structure RibUpper Die Size Dieface ThicknessRibGuideHeel Guide Guide Post SeatCushion Pin Seat HookBolt Type Cast-in Type Stopper Seat Circle Type Square Type Safety Area GuideHeel Guide Guide Post SeatCushion Pin Hole U-grooveHookBolt Type Cast-in Type Auxiliary Plate Triangle Rib Stopper Seat Circle Type Square Type Safety Area Key-grooveGuideHeel Guide Guide Post SeatAuxiliary Plate U-grooveTriangle Rib HookBolt Type Cast-in Type Stopper Seat Circle Type Square Type Safety Area Fig. 6. Organization diagram of supported features.1590B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 15861598 Each hook for upper dies and blank holders should sup-port a minimum 55% weight of the component. Each ofthe three hooks of the lower dies should support a mini-mum total weight of the die.Fig. 3 shows its design specifications.3. System componentsAfter receiving all required design information andappropriated types of subcomponents from the user, thissystem is able to finish the design of main components ofthe die based on design guidelines and specifications.Fig. 4 illustrates the architecture of our system, whichincludes a design knowledge base, a design database, aCAD software, an inference engine, and user interfaces.Each of the components is detailed below:3.1. The user interfaceThe user interface offers users a way to interact with thesystem effectively and efficiently. The user interface of oursystem allows users to input both alphanumeric and gra-phic information. This interface also shows the final designto users. The interface for inputting alphanumeric informa-tion is used to select the types of press machines, guidemechanisms, hooks, and stopping seats, while the interfacefor inputting graphic information is used to change diefaces, punch open lines, and blank lines.3.2. The inference engineThe inference engine is the core of our system. It isresponsible for generating the solid structure design ofthe main components based on users input. The infer-ence engine consists of four units: a model generator, asubcomponent selector, a shape calculator, and an infer-ence coordinator. Instead of being input by the user viaan interactive way, the parameters of solid models areautomatically calculated by the design system. Therefore,solid models are generated by the 3D CAD system auto-matically. In case any error occurs during the modelingprocess, the system will send an error message to theuser. The subcomponent selector is used to determine thequantity, position, and size of a subcomponent basedon design constraints and formulas derived from the ini-tial design information. The subcomponent selectorused in our system has 227 constraints and formulas. The shape calculator is responsible for determining theshape of a subcomponent. After the type and size(independent parameters) of the subcomponent aredetermined, the shape calculator is able to out putthe shape of the subcomponent based on design tables.The shape calculator used in our system has 328 typesof shapes. The model generator is responsible for generating 3Dsolid models of a subcomponent based on its designparameters, such as type, quantity, position and size,as well as geometric operations used in the modelingprocess. The calculator used in our system has 42 differ-ent modeling operations and 135 features. The job of the inference coordinator is to coordinate theotherthreeunitsintheinferenceengine.Afterusersinputof the design information, the inference coordinatorstarts to design the main components of drawing diesbased on their design process. For each of the subcompo-nents, the type of the subcomponent is either specified bytheuserordeterminedbythesubcomponentselector.Thesubcomponent selector is also responsible for determin-ing the quantity, position, and size of the subcomponent.Then, the shape calculator starts to calculate the shape ofthe subcomponent, and triggers the model generator tofinish the solid model design of the subcomponent.Upper Die Lower Die Blank Holder Design Process of Drawing Die BH Size RibSafety Area Stopper Seat HookPanel Guide Seat Cushion Pin Seat GuideAvoid Structure DiefaceThicknessLower Die Size DiefaceThicknessHookU-grooveAvoid StructureGuideCushion Pin HoleTriangle Rib Stopper Seat Safety Area RibKey-grooveUpper Die Size RibSafety Area Stopper Seat HookTriangle Rib U-grooveAuxiliaryPlateGuideDiefaceThicknessAuxiliaryPlateFig. 7. Design process of drawing die.B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 1586159815913.3. The knowledge baseThe knowledge base includes both design processes anddesign guidelines. The design processes outline the designand modeling process for each of the subcomponents.The design guidelines are used to determine the quantity,positions and size of each of the subcomponents.In the design knowledge base, dies are systematicallyclassifiedintocomponentsandsubcomponents;33categories subcomponents with 42 different types are listedin our system. The understanding of the relationship amongvarious subcomponents is vital to obtain an appropriatedesign process for each of the subcomponents. Detailedmodeling processes for each subcomponent, as well as geo-metric operationsused insuchprocesses, areavailableintheknowledge base. Also, design guidelines and 3D diagramswith design parameters, itemized text, and formulas arestored as e-books for training, debugging, and referencepurposes.3.4. The design databaseThe design database offers subcomponent specificationsand press machine specifications. The subcomponent spec-ifications specify the sizes of each of the subcomponents,while the press machine specifications specify size of thebolster, maximum and minimum of the die height, maxi-mum die width, positions and sizes of T grooves and cush-ion pin holes, and cushion pin strokes.The design database has 44 types of subcomponentdesign specifications, which fall into 33 categories. Thedesign specifications for each of the subcomponents areillustrated in 2D diagrams. In addition, each diagram isaccompanied by a table that summarizes the related shapeparameters and standard sizes. The design database offersfour sets of press machine specifications, which are pre-sented in 2D diagrams. All information in the design data-base is stored as e-books for easy access.3.5. CAD softwareOur system is developed based on CATIA V5 CAD soft-ware in the Windows XP operating system. This system isdesigned to be used in a PC, and is developed using theCATIA softwares built-in modules. The Part Design mod-ule is responsible for controlling and executing the processof constructing 3D models. Therefore, this module is usedto build the inference coordinator. The Knowledge AdvisorFig. 8. The layer tree of drawing die.1592B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 15861598module allows users to embed related knowledge into thedesign, which increases the productivity of design engi-neers. The subcomponent selector takes advantage of theFormula Editor and Rule Editor functions, while the shapecalculator uses the Design Table function. The Automationand Scripting module offers a user-customized interface forCAD software. The model generator makes use of VisualBasic for Application (VBA) to develop programs for gen-erating solid models. The user interface also uses VBA toconstruct alphanumeric and graphic input interfaces.4. Modeling process of the automated design systemThis system is built on top of the CATIA CAD system,and takes advantage of various CATIA built-in modules.Upon users input of the design information, our systemFig. 9. Sample die.Fig. 10. Program design.B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615981593is able to automatically generate the solid model design ofmain components of a drawing die in an efficient and flexi-ble way. Fig. 5 shows the modeling process. Each step of themodeling process is detailed in the following sections.Fig. 11. Interface for replace procedure of graphic data. (a) Load a graphic data. (b) Active replace window. (c) Ready for update.1594B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615984.1. Die structure analysisDrawing dies for the automotive industry are very large,and have very complicated structures. Moreover, each sub-component has its own functionality. Therefore, beforedeveloping the design system, we collected various struc-tures of drawing dies for automotive sheet metals, and ana-lyzed their architectures and functions. Fig. 6 shows aclassification of the subcomponents of a typical drawingdie based on their functionality.The parameterized die design system treats the change-able dimensions of a die as parameters, and generates thefinal design by assigning appropriate values to each ofthe parameters based on design formulas, constraints andtables derived from the design guidelines and specifications.However, certain data and subcomponents, such as pressmachines, hooks, guides, and stopper seats, cannot bedesigned simply by changing the design parameters becauseof the diversity of their structures. Therefore, we pre-buildthe interfaces and structures of a sample die for all subcom-ponents that share the same functionality based on designguidelines and specifications.4.2. Design process standardizationThe purpose of design process standardization is to pro-vide a systematic way of designing dies. Since the CAD sys-tem has its own modeling process, the size and position ofdesign subcomponents cannot be determined until the sizeand position of certain subcomponents are fixed. A stan-dardized design process, as shown in Fig. 7, is generatedbased on the design guidelines and specifications of eachof the subcomponents, as well as the cause-and-effect rela-tionships among these subcomponents. This standardizedprocess is used to guide the design of main componentsof sample dies, such as their structures and initial sizes,as well as the initial sizes and positions of each subcompo-nent on a main component.4.3. Sample die constructionOnce a standardized design process is obtained, a fea-ture layer tree and sample dies are developed based onthe design process, as shown in Figs. 8 and 9. A typicaldie face consists of thousands of surfaces. In order toensure the stability of a sample die, simple die faces areused to construct sample dies. Since various subcompo-nents of a drawing die can share a common functionality,all possible subcomponent structures of a function mustbe pre-constructed when constructing sample dies. Whenconstructing a solid model of a die, only the selected sub-components should be activated. All unselected subcompo-nents should be deactivated.When constructing sample dies, design engineers shouldmake use of all available parameters and pre-set sizes. Thenumber of parameters has adirect impact on the design flex-ibility. In most cases, the number of parameters decreases inthe design process, which makes programs more concise.Therefore, appropriate number of parameters is vital tothe entire design process. All of the changeable dimensionsare treated as parameters, whose values can be changedbased on design requirements. Since the values of thedimension parameters cannot be non-positive, all possiblesituations should be taken into consideration to avoid anypotential problems, especially when there are cause-and-effect relationships among the various subcomponents.4.4. Parameter settingsThere are hundreds of parameters in our automaticdesign system, which demands a systematic naming schemaso that parameters can be well managed to facilitate codingand debugging. The name of a parameter used in our sys-tem consists of two parts: the name of the part to which theparameter belongs, and the name of the dimension.Based on the parameters functionality, they can bedivided into shape parameters and position parameters.Shape parameters can be further classified as dependentparametersandindependentparameters.IndependentFig. 12. Alphanumeric data interface.B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 158615981595parameters only need to meet the design guidelines, whiledependent parameters are determined by both the designspecifications and any relevant independent parameters.Taking the bolt type hook shown in Fig. 3 as an example,the diameter of the hook bolt, d, is an independent param-eter, while the other measures, such as Y, X, r, t, l, and R,are dependent parameters.4.5. ProgrammingOnce the parameters have been identified, the relation-ships among various parameters need to be formulatedbased on design guidelines and specifications. These rela-tionships are further converted into programs. Programsare divided into three levels in order to facilitate the designprocess.Taking the bolt type hook as an example, the purpose ofthe first level is to select subcomponents based on designguidelines. This level of program takes advantage of twobuilt-in modules of CATIA V5, Rule Editor and FormulaEditor, to convert design guidelines into constraints andformulas respectively, which are used to determine thequantity, position and size of subcomponents, as shownin Fig. 10a and b.The second level of the program is responsible for calcu-lating the values of shape parameters of the die. This leveltakes advantage of the built-in modules of CATIA V5 toconstruct the design table of the die based on the designspecifications of each subcomponent, so that this level ofthe program can use the design table and related indepen-dent to determine dependent parameters, as shown inFig. 10c.The third level of the program is used to construct of themodel. Written by VBA, this level of program is used toprovide a modeling procedure of subcomponents basedon determined the type and size of aforementioned two lev-els, as shown in Fig. 10d.4.6. User interfacesUser interfaces allow users to accomplish the designprocess in an intuitive and interactive way. The user inter-faces used in our system can be classified into twocategories.Fig. 13. Design process of the proposal system. (a) Sample die. (b) Graphic data interface. (c) Alphanumeric data interface. (d) Drawing die for trunk lidouter panel.1596B.-T. Lin, S.-H. Hsu / Expert Systems with Applications 34 (2008) 15861598The first category is used to input graphic information,suchasblanklines,diefacesandPOLs.Thissetofinterfacesis using Replace, which is a built-in function of CATIA V5.Following are the procedures for replacing sample graphicinformation. First, start the automated design system, andload the desired graphic information into the design envi-ronment. Click on the layer tree representation of the sam-ple graphic information, as shown in Fig. 11a, and openthe Replace window, as shown in Fig. 11b.Select the desiredgraphic information of the die and click OK. The color ofthe die turns to red when it is being updated, as shown inFig. 11c.The second category is used to input alphanumericinformation, such as types of press data, guide mechanism,and hooks and stopper seats, as shown in Fig. 12. Imple-mented using VBA, a drop-down menu allow users toselect the appropriate types of subcomponents for thedie. Design engineers only need to select the desired pressmachine and types of subcomponents, and click OK; thesystem is able to automatically complete the design.5. Case studyWe use the design of drawing dies for a trunk lid outerpanel as a concrete example to showcase the power of oursystem. A standard structure diagram of sample dies is dis-played when the system starts, as shown in Fig. 13a. Uponreceiving graphic information from the user, our systemuses CATIAs built-in Replace function to replace the gra-phic information using the layer tree of the sample die, asshown in Fig. 13b. Then, users begin to input alphanumericinformation, such as the types of press machines, guidemechanism,hooks,andstopperseats,asshowninFig. 13c. After users click OK, our system begins to gener-ate the design based on the design processes, guidelines andspecifications. The final design of the drawing die is shownin Fig. 13d.Fig. 14 presents a comparison of two different drawingdies, a drawing die for trunk lid outer panels and a drawingdie for engine hood outer panels, to show that our systemcan handle a wide range of designs.6. Conclusions and future worksThis paper presents an automated design system fordrawing dies, which is built on top of CATIA CAD soft-ware. Upon receiving the initial design information fromdesign engineers, such as blank lines, die faces, POLs,and press data, as well as the types of hooks, guide mech-anism, and stopper seats, the