Concurrent Process Planning for Machined Parts

TSINGHUA SCIENCE AND TECHNOL0GYISSN 1007-0214 10/22pp481 - 487Volume 7，Number 5，October 2002Concurrent Process Planning for Machined Parts'WU Dan (吴丹)** ，WANG Xiankui (王先逵), LI Zhizhong (李志忠)Department of Precision Instruments and Mechanology，Tsinghua University, Beijing 100084，ChinaAbstract: Detailed manufacturing information about the parts can help designers produce better designs.Detailed manufacturing information is conveyed to the designer through micro. circles within the concurrentdesign process for machined parts, focusing on instantaneous product design and process planning. Theprocess has three key elements: a hier archical architecture design of the concurrent process planning system ,modeling and reengineering of the concurrent process planning, and modeling of information. The approach issuccessfully implemented and applied for concurrent design and process planning of some complicated parts.Key words: concurrent engineering; concurrent design; process planningand employment of design for X tools, such asIntroductiondesign for manufacturing， design for assembly,Development of a product undergoes a sequence ofdesign for cost， and design for serviceability. Inlife-cycle phases including design，process plan-the concurrent design， as the evaluations of thening，manufacturing，inspection， andmain-downstream productdevelopment aspects atenance. In the past，these product developmentcarried out instantaneously at the early designactivities were organized in a sequential manner :stage,this approachincreasesindustrialfrom design to downstream life-cycle phases. Ascompetitiveness by reducing the number of costlythe design engineers tend to generate designs withredevelopments，shortening product developmentexcellent functional performance， these designslead-time and providing high quality products.usually require excessive manufacturing efforts;Concurrent design is actually modeled bytherefore, leading to a high production costl1.21multipleiteration sub-processes called designTo reduce the gap between design and othercircles, for the gradual generation and addition ofdownstreamproductdevelopmentaspects，design information. Analyzing concurrent designconcurrent design has been extensively studied[3-8].shows that the iteration processes have to beConcurrent design is a method which incorporatesdesigned at different levels of macro- and micro-theconsiderationindow nstreamcircles. The macro circle emphasizes the roughdevelopment aspects into the design stage tosimultaneity of design withproduce a design with the best overall product life-development aspects at the level of a part， whilecycleperformance.Concurrentdesign isthe micro-circle focuses on the detailed informationcharacterized by early involvement of differentfeedback between design and downstream activitiesfunctional disciplines， parallelism and rational-at the feature level of the part. The existence ofization of sequential product development activities中国煤化工ffective increase in the .desMYHC N MH Ghich will shorten theproduct development per1od. With the goal ofReceived : 2001-04-26; revised: 2002-03-27* Supported by the State High- Tech Development Plan ofreflecting the essence of concurrent design， it isChina (No. 863-511- 9842- 011)necessary to make full use of the approach to*￥Towhom correspondence should be addressed. .micro-design circles from the point of both processE-mailm. tsinghua. edu.cn;and information. Based on the analysis of productTel: 86-10- 62773270development process involving design， process482Tsinghua Science and Technology, October 2002，7(5): 481 - 487planning, and other relevant aspects, an optimizedThe research in this paper aims at developing anprocessanddetailedinformation flow areapproach to instantaneous concurrent design andsubsequently reengineered to identify when andprocess planning focusing on the formation ofhow every sub-process runs， and what kind ofconcurrent design micro -circles and the provisioninformation flows among sub -processes.of detailed manufacturing information to help theIn concurrent design， downstream manufactur-designer to formulate appropriate manufacturinging information should be provided to make properspecifications and to yield the best product design.decisions at the design stage. Since process1 Architecture of Concurrentplanning is the stage of production preparationthrough product development aspects， it canProcess Planning Systemprovide detailed manufacturing information to theThe proposed system provides a concurrent processdesigner and play a crucial role in concurrentplanning environment for parts to be machined.design. Therefore, concurrent process planning isDuring the process planning stage， the plannerviewed as one of the most important areas ofshould be able to access design information andconcurrent design which deserves extensiveresearchE9-151.However，the framework of adesigner for manufacturability assessment.Theconcurrent process planning system at the micro-architecture of the system is designed in fourcircle level of concurrent design has not yet beenlayers: information， function， control andfully addressed.application, shown in Fig. 1.User interfaceApplication layerExecution and controlModeling ofControl layerof concurent processconcurrent pro--个-ETechnological decision-Definition ofmakingfunection modelFunction layer二二土一一一二一个二------Definition of information modelInformation layer| linformationlinformationJlinformationlinfommationFig.1 The architecture of the proposed concurrent process planning systemSince the information model is the basis of the .for making different technological decisionsconcurrent process planning system, the bottom ofaccording to various kinds of decision logic andthe architecture is designated as the informationproducing detailed manufacturing information.layer including information of parts， technologicalBasedonthedecision-makingengineknowledge，manufacturing resource， etc. Theinformationmodel，the function modelinformation model specifies the methodforsubsequently defined. As a result，heterogeneousinformation description and data representation.cor中国煤化Ting functions can beThere are two sections in the function layer: onecar:YHCNMHGs the decision making engine based on thelayer aims to manage,knowledge information model， the other is theexecute and control all functions of concurrentfunction modelincludingconcurrent processprocess planning. It starts with the modeling ofplanning relevant activities. The decision-makingthe concurrent process. Since process planning is aengine wogks翳eunified implementation engine offundamental constituent of the product and processprocess planning Tunctions，and therefore, allowsdevelopment，the establishment of aWUDan (吴丹) et al: Concurrent Process Planning for Machined Parts483planning system that is able to support concurrentfunction. The part characteristics include batchproduct and process development should be basedsize，weight， material and its properties， parton the interactions between process planning angeometry, accuracy of size and shape, and surfaceother development activities.Hence，afterquality.After the rough design， the designconventionalprocessplanning andrelevantengineer can further define detailed featureactivities are analyzed and represented as an as-isattributes of a part. According to functionalmodel, a concurrent process planning model is thenrequirements of every feature involved in the part,developed based on the concept and principles ofthe feature attributes including shape, accuracy ofconcurrent engineering. The process model givessize and shape, surface finish，relevant accuracy ofdetailed descriptions of the interactions andsize and position between features are designedrelationshipsbetween processcorrespondingly.relevant activities involving product design,2.1.2 Process planningassessment of manufacturability， fixture design，Conventional process planning is performed aftergeneration of numerical code (NC)， simulation ofthe product is designed. Isystematicallytool path, production planning and control, etc.determines the detailed method by which the highAccording to the interactions， the relationshipsquality product can be manufactured economicallybetween these activities are classified as beingwith competitiveness. Usually， process planningeither concurrent or serial. All the activities arecontains tasks of information input , manufacturingcontrolled and executed to provide effectivemethod selection， tool selection， setup plansupport for concurrent design.selection，cuttingparameteroptimization，The top layer of application provides a user-manufacturing process sequencing， and processfriendly interface for the running of multipledocumentation output.application embodiments.However，the analysis of concurrent processplanning procedures shows that process chains for2 Concurrent Process Modelingmanufacturing a product have to be designed atThe purpose of concurrent process modeling is torough planning and detailed planning according tofully understand the characteristics of concurrentdifferent planning phases. The rough processproduct design and process planning，including theplanning focuses on the optimized adjustment ofactivities and tasks involved, their constraints andthe manufacturing process with respect to thesupporting resources, as well as information flowproduct shape and the applied material. Therefore ,in the proces， and the interaction among thea broad process spectrum can be taken intoproduct and process development activities.consideration for the generation of differentTherefore，the focus of this section is fourfold :manufacturing alternatives in early phases of(1 ) decomposing concurrent product and processproduct design. Subsequently, the detailed processdevelopment activities into the task levels; (2 )planning includes three levels: (1) feature processanalyzing and identifying the relationships andplanning，(2) overall optimization and sequencinginteractions among these tasks; (3) adjusting theof manufacturing process， and (3) single processprocess sequence based on the input and output todesign. F eature process planning aims at thind from each task; and ( 4 ) developing ageneration of various manufacturing methods ，concurrent process model based on the abovesetupplans,andmanufacturingresourceresults and concurrent engineering principles.alternatives according to the feature informationand technological knowledge. The machine tools ，2.1Decomposition of concurrent processcutting tools and measurement tools are involved inplanning and other relevant activitiesthe manufacturing resources.2.1. 1 Product designidentifiedfeatre.DrocessplanningBecause each part is a combination of multiplema中国煤化工n be generated after thefeatures，the part design is viewed as a series ofimMYHCN M H Gining and optimizingfeature designs. Feature-based design is actually amanutacturing resource alternatives and setupkind of mapping process from function feature tcplans. A multicriteria-analysis method is applieddesign feature， which contains rough design andto select the best-suited manufacturing sequence. .detailed feature design. In the rough design, theAfter the selection of the preferable manufacturingengineer s际方数据ough elements or attributes of asequence,individual processes aspartofpart，which are significant for the fulfilment of itsmanufacturing sequence can be designed and484Tsinghua Science and Technology, October 2002，7(5): 481 - 487optimized at a further level. This optimizationassessment are immediately carried out. At theincludes the computation of machining time, thelevel of the part， process planning focuses on theoptimization of cutting parameters， and the .evaluation and optimization of the overall processanalysis of machining cost.plans of the part.2.1.3 Design for manufacturabilityAnalysis of design manufacturability here is2.3 Concurrent process modelinglocated in a phase immediately prior to the processBased on the identification of every developmentplanning.' This approach is a novel way oactivity task and the analysis of the input with theoptimizing the design quality before it is sent to theoutput of each task， the concurrent designprocess planning system， to avoid the waste ofmanufacturing process sequence is formedresourcesinvolved irprocessplanning of. linking the input with the output. The newlyunavailable designs. The design evaluation isdeveloped concurrent process model is shown incarried out in two aspects. The first aspect isFig.2，in which different legends are employed torelated to the manufacturability of the part,distinguish process planning and other relevantwhereas the second aspect is about theactivities to give a clear representation ofmachinability of the features of the part. Therelationships among these activities.former evaluates the layout, material, fabrication,3 Information Modelingand design criterion of the part， while the latterassesses the dimension， tolerance， and surfaceIn the concurrent process planning system， thefinish of the features.information model is developed as the basic2.1.4 Other relevant activitiesconstruction of the system.Therefore，thThe fixture design progresses in two steps asinformation model has to provide the integratedpreliminary design and detaileddesign.Thedefinitions of various attributes of the informationpreliminary fixture design seeks to design a roughobject. To keep the integration ability ，fixture structure，while the detailed design of theadaptability and scalability of the information，ifixture focuses on the verification of the fixturemethod named information element is proposed tostrength and accuracy. The design of NCconstruct the information model of the concurrentmachining includes tasks of generating NC codeprocess planning system-16].The informationand a cutting path.element method avoids the detailed characteristicsof the object and is independent of specific2. 2 Identification of the relationships betweenapplications.process planning and other relevantactivities3.1 Modeling and extraction of part informationThe relationships and interactions between processIn the presented concurrent process planningplanning and other relevant development activitiessystem，feature- based design is adopted. Featureinclude four aspects: ( 1 ) extracting the designmodelscarry .sufficientinformationforinformation from the design activity; (2) providingmanufacturabilityassessmentandthe information of manufacturability assessment toplanning. The part information includes generalthe designer; ( 3 ) providing the necessarycharacterizations，geometrical descriptions andinformation to otherdevelopment activitiestechnologicalspecifications.Generalcharacinvolving fixture design， machining simulation,terizations involve part name, material property,etc; (4) obtaining the information of the processweight，and batch size.Amonggeometricalplan evaluation from other activities.descriptions are feature shapes， dimensions andThe design and process planning of a part arefeature relationships. Examples of technologicaltwo key aspects in the concurrent design. Therespecification are the tnlerance and surface finish.are many frequent information flows betweenMc中国煤化工n is also based on thedesign and process planning. To timely detect theinfHC N MH G. The developed model .potential manufacturing problems at the earlyis shown in Fig. 3 (where FK is abbreviated fromdesign stage, the manufacturability assessment has“foreign key").to be designed at two levels. At the feature level，To instantiate the part information model, datadesign and process planning activities proceedare retrieved from the CAD model of the part. Theinstantane万时数据hamely，after the design of aretrieved data include details about surfaces, edgesfeature is performed， process planning andand vertices as well as the technologicalWU Dan (吴丹) et al: Concurrent Process Planning for Machined Parts485Roughprocess planningFunctionalPreliminary( Detail designDetail manufacturabilityrequirement analysis_ designof featuresassessment of featuresmanufacturabilityassessmentMachining methodselectionachineCuting toolsMeasurementselection) ( tools selectionSetup combinationRough fixtureGeneralGeneral designand optimizationdesignOperationRough analysissequencingof NC machiningResource combinationand opimizationDetail fixtureParametersCutting timeDetailedPlans outputoptimizationcomputationeconomyDetail analysis ofLegend:NC machiningProcessOtherplanming_ )activitiesFig. 2 Modeling of concurrent processPartPart numberHaving| HavingFeaturePart information elementFeature relation( Feature number.( Part information element numberFeature relation numberPart number(FK)| Feature typeInformation element number(FK)( Father fealure numberHavi| CorrespondingFeature infion information elementInformation element( Feature information element number( Feature relation information element numberFeature number(FK)Infomation element number HFeature rlation number(FK)Pant number(FK)Cores-Corres-| Part number(FK)pondingponding Information element number(FK)Fig. 3 The part information model based on the information element methodspecification for the entities. The Pro/ EngineerCAD model is too complex to obtain proper andCAD system provides a user-defined feature- basedinformatinn, a novel approach tdesign environment that obviates the need forfea中国煤化工osed which focuses onrecognition of standard features. Functions forcapMHC N M H Gnation instantaneously.geometrical reasoning are then invoked to performWhen a feature design is performed， itsfeature type recognition and feature specificationinformation is got whenever the designer selects it.identification. The prototype concurrent designThe development toolkit of Pro/Engineer and Pro/and process planning system is constructed usingDevelop is used for accessing the CAD modelPro/ Engin方数据database and reasoning about feature type andBecause automated feature recognition from theattributes. The generated feature information is486Tsinghua Science and Technology, October 2002，7(5): 481 - 487saved and provided to the process planner. Thisplanning，.planning result output， planningapproach provides effective support for the real-schedule management， andknowledge basetime concurrent design and process planning at themaintenance. The system is integrated with thelevel of micro circle.product design system, the computer-aided fixturedesign system, the computer-aided NC machining3.2 Modeling and control of knowledgesystem，and the machining simulation system.The technological knowledge is critical to decision-Theseforma computer-aidedconcurrentmaking in process planning. To make theenvironment for product and process developmentconcurrent process planning systemhas highwithinone advancedconcurrent engineeringcapabilityof know ledgedescriptionandresearch project. A demonstration of themanagement，the technological knowledge iscapabilities of the prototype system is carried oumodeled with the attributes of relationship,with examples of three parts with complicatedmathematic representation and special key wordsconfiguration.of the information element. Since the relationship5 Conclusionsproperty of information element has importantinfluences on its capability of description andThis paper presents a new approach to concurrentmanagement，114 types of relationships have beenprocess planning focusing on the formation ofsummarized and implemented in the developedmicro circles within a concurrent design.concurrent process planning system.system is designed as four layers: information,In the real world, the technological knowledge isfunction, control and application. The hierarchicaleither experience- based or handbook- presented.architectureprovides a general guideline andAll knowledge can be represented as processframework for the research and implementation ofplanning rules. According to the process planningthe system. By analyzing the development process,tasks and their interactions with other developmentespeciallythe relationships and interactionsactivities，the process planning knowledge isbetween process planning and other developmentsorted into a knowledge hierarchy, within whichactivities，the concurrent process planning hasknowledge units correspond to the tasks andbeen modeled to offer the basic and key support foractivities of the process model.Each knowledgethe implementationofprocessunit is represented in the form of a knowledgeplanning. In addition， the information modelsobject as the abstraction of the rules. Theprovide a natural way for the data exchangepresented knowledge hierarchy helps users t(between concurrent activities and facilitate thorganize and employ technological knowledgeeffective use of knowledge. The proposed approacheffectively according to the characteristics of thehas substantially reduced the number and durationpart to be machined, the production environment,of changes in the design and manufacturingand the necessary process planning function. Theprocesses，and greatly shortened the productefficiencyof decision- makingthedevelopment lead- time. .maintainability of the knowledge are greatlyimproved. The objective of knowledge control is toReferencesfacilitate the management andemployment of[1] Merabti M，Colquhoun G，Hanneghan M. Amassive process planning rules and to generateviewpoint analysis reference model for concurrentmanufacturing plans rapidly and properly. Its basicengineering. 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