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Computer-Aided Design 42 (2010) 10851094Contents lists available at ScienceDirectComputer-Aided Designjournal homepage: /locate/cadComputer aided fixture design: Recent research and trendsHui Wanga, Yiming (Kevin) Ronga,b, Hua Lib, Price ShaunbaDepartment of Precision Instruments and Mechanology, Tsinghua University, Beijing, 100084, ChinabComputer Aided Manufacturing Laboratory, Worcester Polytechnic Institute, MA, 01609, USAa r t i c l ei n f oArticle history:Received 7 April 2009Accepted 15 July 2010Keywords:Computer aided fixture designLiterature surveyTrenda b s t r a c tWidely used in manufacturing, fixtures have a direct impact upon product manufacturing quality, pro-ductivity and cost, so much attention has already been paid to the research of computer aided fixturedesign (CAFD) and many achievements in this field have been reported.Inthispaper,aliteraturesurveyofcomputeraidedfixturedesignandautomationoverthepastdecadeis proposed. First, an introduction is given on the fixture applications in industry. Then, significant worksdone in the CAFD field, including their approaches, requirements and working principles are discussed.Finally, some prospective research trends are also discussed.2010 Elsevier Ltd. All rights reserved.1. IntroductionA fixture is a mechanism used in manufacturing to hold a work-piece, position it correctly with respect to a machine tool, and sup-port it during machining. Widely used in manufacturing, fixtureshave a direct impact upon product quality, productivity and cost.Generally, the costs associated with fixture design and manufac-ture can account for 10%20% of the total cost of a manufactur-ing system 1. Approximately 40% of rejected parts are due todimensioningerrorsthatareattributedtopoorfixturingdesign2.Fixture design work is also tedious and time-consuming. It oftenheavily relies on fixture design engineers experience/knowledgeand usually requires over 10 years manufacturing practice to de-sign quality fixtures 3. Traditionally, the design and manufactureof a fixture can take several days or even longer to complete whenhuman experience in fixture design is utilized. And a good fixturedesign is often based on the designers experience, his understand-ing of the products, and a try-and-error process.Therefore, with the increasingly intense global competitionwhich pushes every manufacturer in industry to make the besteffort to sharpen its competitiveness by enhancing the productsquality, squeezing the production costs and reducing the lead timeto bring new products to the market, there is an strong desirefor the upgrading of fixture design methodology with the hopeof making sound fixture design more efficiently and at a lowercost. The development of computer-aided fixture design (CAFD)technology over the past decades can be attributed to the fulfillingof this goal.Corresponding author.E-mail address: wanghuisx (H. Wang).As an important field in manufacturing, research and applica-tions of fixture design has been paid much attention over pastdecades 4,5. Many academic and applications papers have beenpublished in this area. In this paper, we will focus on an investiga-tion of computer aided fixture design research in the past decade.The following sections will give a survey on the state of the art oftheseresearches.Someconclusionsonresearchtrendsarealsodis-cussed.2. Fixtures in manufacturingA fixture is designed to position and hold one or more work-piece(s) within some specifications. It is widely used in man-ufacturing, e.g. machining (including turning, milling, grinding,drilling, etc), welding, assembly, inspection and testing. The fol-lowing Figs. 19, are some real fixture design cases in manufactur-ing. Fixtures can be classified with different principles. However,comparedwiththepublicationsofCAFDresearchinmachiningfix-ture field, only a few 616 have been focused on other importantmanufacturing fields, for instance, assembly fixtures and weldingfixtures.2.1. Welding fixturesWelding is essential to a high dollar volume of manufactur-ing processes, including national defense industries. According toEconomic Impact and Productivity of Welding, Heavy ManufacturingIndustries Report, by American Welding Society and Edison Weld-ing Institute on June 2001, The contribution of welding to the USeconomy in 1999 via these industries was no less than $7.85 bil-lion.Thisfigurerepresented7%oftotalexpendituresbythesefirmsin 1999 17,18. So there are significant technical and commercial0010-4485/$ see front matter2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.cad.2010.07.0031086H. Wang et al. / Computer-Aided Design 42 (2010) 10851094Fig. 1. Machining fixtures (IMAO corp.) 19.Fig. 2. Machining fixtures of aircraft-used bearing housing.Fig. 3. Grind fixture for turbine blades (aerocad design, inc.) 20.advantages in the developmentanddeploymentofweldingfixturedesign systems.There are obvious differences between machining fixture de-sign and welding fixture design. As in the following:Fig. 5.Automotive stud weld fixtures on a trunion frame, (DBM innovationinc.) 22.The workpiece in a welding process is usually an assembly ofseveral parts, while workpieces undergoing a machining pro-cess contain only one part.Usually, the accuracy requirement in a welding process is lessthan in machining.Fixing forces and machining forces in a welding process com-monly are smaller than in machining.Thermal reactions in welding should be seriously considered.Furthermore, these factors also should be paid some attention inwelding fixture design cases:Electrical conductivity is critical for arc welding stability.In addition to thermal conductivity, when selecting fixture ma-terial thermal expansion properties also should be considered.Refined welding waveforms require an optimized welding cir-cuit to maintain short arc lengths while reducing spatter, stub-bing, arc flare, and arc outages to maximize travel speeds.More complex applications may require a dedicated fixture.The design and installation of a dedicated fixture frequently in-volvesinstallingandroutingwiringandpneumaticorhydrauliclines.In the past decade, only very limited CAFD research and appli-cations have been reported in the welding sector. In this field, dueto the importance of welding for sheet metal assembly in automo-bile and aerospace industries, the assembly and welding of sheetmetal has received some special attention. A weld fixture is of-ten developed to reduce the deformation of each workpiece dueto heat and residual stress in the welding process and, hence, toreduce the dimensional variation of the assembly. Therefore, somemethods of offline or online deformation analysis were developedto enhance the fixtures ability on deformation controlling 8,9. InFig. 4. Assembly fixture to locate shelves for assembly of cabinets (pioneer industrial systems LLC.) 21.H. Wang et al. / Computer-Aided Design 42 (2010) 108510941087Fig. 6. Robot weld fixture (IMPROVE solutions LLC.) 23.abFig. 7. Pin-array fixture application 29.Fig.8. Modularfixtureforapartfortheconstructionmachinery(BLUCOcorp.)30.Fig. 9.Dedicated fixture for a part for the construction machinery (BLUCOcorp.) 30.sheet metal assembly with laser welding fixtures also should en-sure a fit-up of the mating surfaces to ensure proper laser beamweld operation and laser weld quality. As a result, a traditional3-2-1locatingschemeisextendedtoamixedlocatingidea,totallocating and direct locating for welds 1013. The total locatingscheme is used to locate the entire assembly, and the direct locat-ing scheme is used to locate the weld joints to meet the metalsfit-up requirement.2.2. Applications of modular fixtures and dedicated fixturesAccording to the fixtures flexibility, fixtures also can be clas-sified as dedicated fixtures and general purpose fixtures (e.g.reconfigurableandconformablefixtures,modularfixtures).Recon-figurable and conformable fixtures 2426 can be configured toaccept parts of varying shapes and sizes. Particularly, conformablepin-arrayfixturetechnology27iswidelyusedinmanyfixturede-signsbecausesomecomponentscontaininternalvariablesthatcanbe adjusted to meet the different features of workpieces (as Fig. 7).And phase-change materials-related fixtures also are used in someprecision manufacturing. For instance, in the aerospace industry,low melting-point metals are used to enclose turbine blades andproduce well-defined surfaces for part location and clamping forgrinding operations.The most important and widest used within the general pur-pose fixture classifications are modular fixtures. As the flexiblemanufacturing system has been adopted by more and more man-ufacturers who are trying to remain competitive in this rapidlychanging market by running production with short lead times andwellcontrolledcost,modularfixtureshavegainedinpopularitybe-cause of its performance on easy usage, versatility, and its adapt-ability to product changes.1088H. Wang et al. / Computer-Aided Design 42 (2010) 10851094Fig. 10. A dedicated tube bending fixture (Winton machine company) 31.Modularfixturesallowawiderflexibilitybymakinguseofstan-dard workholding devices and components. Their flexibility is de-rivedfromthelargenumberofpossiblefixtureconfigurationsfromthe different combinations of fixture components. The applicationofmodularfixturescontributesconsiderablytoshorteningtheleadtime and reducing the cost in small-volume production with ver-satile products. However, it also has some limitations 28:Only limited combinations can be achieved from these compo-nents, meaning that it is possible that no suitable combinationcan be built for some workpieces with irregular or complex ge-ometries.Structural properties of modular fixtures are sometimes diffi-cult to be maintained. Structural properties of modular fixturesinclude locating accuracy, stiffness, stability, loading and un-loading, operating speed, etc. It is common that using modularfixtures may not achieve an optimal fixturing quality.Not suitable for mass production, e.g. automotive productionand its components manufacture.For comparisons sake, Fig. 8 shows a modular fixture used fora part for the construction machinery, and the same part also usedin Fig. 9, where a dedicated fixture solution is given.The dedicated fixtures are also important in manufacturing,particularly, for advanced, sophisticated and precise part or massproduction. Because a dedicated fixture is designed for a specificproduct, the designer can carefully tailor the design to not onlymeet the basic fixturing requirements such as the locating ac-curacy, stability, stiffness, but also optimally facilitate the oper-ational requirements such as loading/unloading convenience andefficiency, and effective chip disposal etc. And Fig. 10 is a dedicatedtube bending fixture.Compared with modular fixtures, dedicated fixtures are de-signed carefully according to workpieces design and manufac-turing requirements. So there are more uncertainties imposed ondedicated fixture design tasks. In modular fixture design, there is acomponent library with pre-designed and dimensioned standard-ized fixture components. Thus, the modular fixture configurationdesign is actually to assemble the fixture components into a con-figuration.Due to its extensive use in current manufacturing and stan-dardized production, in many reported CAFD researches and ap-plications, modular fixturing principles are employed to generatefixture designs 3243. Early CAFD in modular fixtures merelyusedthedraftingcapabilitiesofaCADsysteminassembly.Modularfixture elements such as baseplates, locators, supports and clampsare stored in a database. Based on the fixturing idea, first, the de-signer specifies the primary locating surface (point) and its locatorpositions, the suitable clamping surfaces and positions, and thenselects and places the appropriate fixturing components in the de-siredpositions.AlthoughthereisareductioninthetotaltimetakenFig. 11. The basic elements of the fixture design process.to produce a fixture assembly, the final design depends largely onthedesignersexperience.Thustheyonlyprovidefixtureengineerswitha simpletool todofixture designmanuallybased onsome ex-tended functions of commercial CAD software. As a result, currentindustrial applications of CAFD are very limited even though thereare many reported research achievements.Over the past decade, much focus has been put on intelligentmethods for computer aided fixture design to seek a technicalbreakthrough in embedding more design knowledge into semi-automatic or automatic CAFD systems. A detailed discussion willbe done in the following sections (Table 1).3. State of the art3.1. Intelligent and automatic fixture design methodsTypically, fixture design involves the identification of clamps,locators,andsupportpoints,andtheselectionofthecorrespondingfixture elements for their respective functions. There are four mainstageswithinafixturedesignprocesssetupplanning (D1),fixtureplanning (D2), fixture unit design (D3) and verification (D4), asFig. 11 illustrates 48,63. Setup planning determines the numberof setups required to perform all the manufacturing processes,the task for each setup, e.g., the ongoing manufacturing processand workpiece, orientation and position of the workpiece in eachsetup. A setup represents the combination of processes that canbe performed on the workpiece by a single machine tool withouthaving to change the position and orientation of the workpiecemanually. During fixture planning, the surfaces, upon which thelocators and clamps must act, as well as the actual positions ofthe locating and clamping points on the workpiece, are identified.The number and position of locating points must be such thattheworkpieceisadequatelyconstrainedduringthemanufacturingprocess. In the third stage of fixture design, suitable units, (i.e., thelocating and clamping units, together with the base plate), aregenerated. During the verification stage, the design is tested toensure that all manufacturing requirements of the workpiece canbe satisfied. The design also has to be verified to ensure that itmeets other design considerations that may include fixture cost,fixture weight, assembly time, and loading/unloading time of boththe workpiece and fixture units 50.Currently, even though numerous techniques concentrating onfixture design have been proposed and made some achievements,H. Wang et al. / Computer-Aided Design 42 (2010) 108510941089Table 1Current CAFD literature.MethodLevel of detailApplicationD1D2D3D4Shen, et al. 6Reconfigurable fixtures, Automotive enginemachining and assemblyLiu, et al. 7Assembly fixture fault diagnosis, sheet metaljoining processLien et al. 8Integrated measurement in clampingsystemsOn-line correction of welding paths, Roboticwelding of thin-walled aluminum structuresSikstrom, et al. 9Superelement (SE) fixture modeling,Coupled thermalmechanical analysisFixture design in fusion weldingZheng, et al. 32Precise modular fixturePeng, et al. 3335Desktop virtual reality technologyModular fixture design and simulationKumar, et al. 36CAD-based collision detectionModular fixturesMervyn, et al. 38Evolutionary search algorithmIMAO modular fixturesSubramaniam, et al. 44,45Multi-agent system, Geneticalgorithms and Neural networksFan, et al. 46,47XML based informationrepresentation, Case based reasoningmethodWua, et al. 37Linkage mechanism theory: a four-barmechanism and linkage curveModular fixtureHou, et al. 39Modular fixturesGirish, et al. 40Tabu searchFixture elements managementModular fixture elementsLin, et al. 41Modular fixtures for measurementKakish, et al. 42Knowledge-based modelingUniversal modular jigs andfixtures information modelingUniversal modular jigs and fixturesCai, et al. 43TRIZ evolution technologyTRIZ-based evolution study for modular fixtureBoyle, et al. 48,49Case based reasoningWang, et al. 50Case based reasoningModular fixtures for weldingChen, et al. 51Case based reasoningWardak, et al. 52,53Finite element methodDrilling fixturesKrishnakumar, et al. 54,55Finite element method, GeneticalgorithmMachining fixturesSubramanian, et al. 56,57Genetic algorithmHamedi 58Artificial neural network, Geneticalgorithm, Finite element methodChoubey, et al. 59Genetic algorithmMachining fixturesKaya 60Finite element method, GeneticalgorithmMachining fixtureAoyama, et al. 61Genetic algorithmLi, et al. 1013Finite element method, GeneticalgorithmSheet metal assembly with laser weldingDing, et al. 14,15Fixture fault diagnosis, assembly processesKang, et al. 6265Amaral, et al. 66Finite element analysisZheng, et al. 6769Finite element analysisFor fixture stiffness,Hurtado, et al. 7072Finite element method, modeling offixture-workpiece contactsMachining fixturesRatchev, et al. 73Finite element methodThe prediction of part-fixture deformation andtoleranceAsante 74Finite element-basedLoad and pressure distribution calculationWang 7579Tolerance analysis in fixture-workpiece systemEstrems, et al. 80Fixtures in machining processesBansal, et al. 81An integrated fixture planning system forminimum tolerancesLi, et al. 16Multiobjective OptimizationTolerance allocation, assembly fixtureWu 28Geometry generation of fixtureNote: Setup planning (D1), fixture planning (D2), fixture unit design (D3) and verification (D4).mature and commercial CAFD applications also are very limited.Fixture design still continues to be a major bottleneck in thepromotion of current manufacturing. This work currently, isimplemented by a typical designer-centered pattern, that is, allfixturedesignrelatedworkisheavilydependantontheexperienceand knowledge of fixture designer. This situation hampers theimprovement of productivity, requires a long time to cultivatean experienced fixture designer and make the fixture design jobweak with a major bottleneck. Thus, new intelligent or automatictechnologies on synthesizing traditional geometric design tools,design knowledge, and past design cases have attracted muchinterest in both academic institutions and industries. The effortsoverpastdecadesinthisfieldhaveresultedinnumerouscomputeraided fixture design (CAFD) applications using various intelligentmethods, such as expert system, case based reasoning, and geneticalgorithm (GA), etc.In essence, developing fixture design methodology needs tocleartwocrucialproblems:howtorepresentfixturedesignknowl-edge in a computer and how to implement the problem solvingprocedure.At the initial stage of CAFD two decades ago, expert systemswere often used as a heuristic tool, which can enlighten fixturedesigner to a complete fixture design solution, particularly, fixtureconfiguration design in an interactive environment 82. In mostof these methods, design knowledge is modeled as a set ofmany IF-THEN rules. Then, during the interactive fixture designprocess, the design solution would be concluded by a series ofquestioninganswering actions based on these rules. However,1090H. Wang et al. / Computer-Aided Design 42 (2010) 10851094Table 2Some CBR methods in CAFD.Case representationCBR procedureChen,et al. 51Define fixture design byattributes templateInteractive mode: Designerselects some importantattributes to match currentdesign case with stored casesFan,et al. 46,47XML and UMLBoyle,et al. 48,49Divide fixture designinformation into twolibraries: conceptual designlibrary and fixture unitlibraryCombination of the searchresults from two caselibrariesSun,et al. 83Using MOP (MemoryOrganization Packages)method to define classesCases matching according tofour basic objects relevant toworkpiece and fixturesWang,et al. 50XML and semantic objectsmodelingInteractive mode: Three tiersCBRs (rough indexing, solutionconfiguration and physicalform determination)+designer intervenedifficulties on building an enough completed rule set and the logictree for reasoning procedure have an obvious impact on the designefficiencyandthequalityoftheresult.Furthermore,theinteractivemode also makes the reasoning procedure very boring.In comparison, Case based reasoning (CBR) does not requireso much complicated domain knowledge system as the expertsystem. It is mainly concerned on how to create a new solutionby imitating past cases, based on the assumption that similarworkpiece will have a similar fixture design solution. So first, itfocuses on structuralizing fixture design cases and to emphasizesomecrucialdatawhichwillbethefocusinmeasuringsimilarities.Then, the final solution will be generated by modifying thebest similar design case according to case comparison. The CBRtechnique gives the possibility to avoid time-consuming andexpensive experiments and is able to propose a good starting pointfor the detailed design (physical form) without many complicatedcalculations.Table2givesacomparisonamongsomeCBRmethodsin the past decade.Two techniques remain necessary and crucial in CBR. One isfor an efficient method to refine, model and utilize fixture designdomain knowledge (fixture design cases), and the other is for aneffective technical system which can assist the fixture designernot only by simplifying the design process, but also by generatingdesign ideas.The prevailing methods on case modeling are based on anattribute set. For example, Chen 51 used a case template tostructuralize all fixture design cases, and Fan divided fixturedesign data into three attribute groups, part representation, setuprepresentation and fixture representation. However, there are fewguidelines on defining and choosing appropriate attributes. So thismostly relies on the designers experience: The designer selectssome important attributes which he thinks are important to thecurrent design case and use these attributes as a vector to computeandmatchstoredcases.Thus,itresultsinademandforsystemizingfixturedesigndomainknowledgetoclarifythedesignrequirementin CAFD. Therefore, Boyle 48,49 developed a methodology toclassify fixture design information into two libraries: conceptualdesign information and fixture unit information. Furthermore, Huire-organizedfixturedesigninformationintothreetiers:workpiece(design requirements), fixturing plan (fixture configuration)and fixture units.The fixture design domain knowledge representation has acrucial impact on the CBR procedure. Actually, a single CBR systemusing attribute similarity often has not a good performance onaccurate results. Sometimes, the attributes which the designerdetermined this time do not fit the next timefor case indexing, or ahigh similarity between cases does not necessarily result in a casethat can be easily adapted.The CBR procedure in most of those articles is similar, a cy-cle such as Aamodts classic model . But as a typical experiencedbased design process, after one cycle of CBR (without a designersinteraction), current fixture design does not have a good perfor-mance on obtaining a good solution. That is why we proposedinteractive multi-tier CBRs for a fixture design system 50. Multi-level CBRs, from rough indexing, solution configuration to physicalform determination, each cycle the result can get a chance to up-date and become more close to the ideal result. Each time, afterone CBR process completes case indexing and retrieval, the systemwill presentthedesigner witha selectionof casesfor adetailed de-cision, rather than just one that is preferred more than any other.And the designer is required to select the preferred case(s) and de-termine what changes need to be made to solve the new case andhow this change can be achieved. Hence, this is an interactive de-sign process, that requires multiple rounds of CBR reasoning andhuman intervention before approximating the final solution.3.2. Generating optimal fixture configuration layoutsThe research of generating optimal fixture configuration lay-outs has received much attention in the CAFD community 5861,1015.Theselayoutsspecifytheoptimumpositionswherethefix-tureshouldcontacttheworkpiecebeingmachined.Themainideasare similar in these typical fixture layout optimization researcharticles (as Fig. 12). The first step is the application of the machin-ing process analysis method to predict the machining forces ex-erted on the workpiece. This analysis is typically carried out fora large sample of cutting tool positions and orientations through-out the machining cycle. The second step is the deformation anal-ysis of the fixture-workpiece system, utilizing the pre-determinedload cases. Typically deformation analysis is based on the finiteelement method (FEM). The loads and the shape of the machinedsurface are calculated, and hence, the deformation of workpiece,under a given locating and clamping scheme, will be analyzed asto whether or not it is in an acceptable region. In general, if consid-eringtheclampingandmachiningforcesovertheentiremachiningprocess, by simulating the dynamic machining process, the analy-sis on workpiece deformation will be more accurate 54,55, witha cost of time-consuming computation. Finally, it will employ anoptimization process (GA is mostly used) to search for a potentialsolution space and determine the locations of the fixtures withinacceptable candidate regions with a minimized workpiece defor-mation 56,57.Mostofrelevantworksassumedsomeconditions:treatfixture-workpiece contact as point contact 5457, the workpiece isdeformable while the tools and fixtures are rigid. So one limitationof these methods is that they usually give a list of coordinatesspecifying where the fixture should be located, without providingthe actual physical form of the fixture unit. Even though byconsidering more relevant factors, e.g., using the workpiece andprocess information, some performance criteria (ease of loadingunloading, cost and rate of production), in the design process 44,45, fixture unit information also is a high level concept that onlyspecifies its basic type and the nature of its components. Currently,thedesignofaphysicalformoffixtureisgeometricbasedandthereis a long way to go before systemizing the research on automaticor intelligent fixture physical design.Oneinterestingmethodisusing therequiredheightasthecriti-cal dimension for fixture unit generation, then to complete the de-tailed fixture shape. Particularly, this method is useful for modularfixture unit design where a fixture unit is usually assembled withseveral existing modular fixture components. So the fixture heightcanplayacrucialroleonsearchingpotentialelementstoassemble.H. Wang et al. / Computer-Aided Design 42 (2010) 108510941091Fig. 12. Typical FEM based fixture design solution analysis framework 73.Fig. 13. Overview of fixture verification system 6265.3.3. Fixture design verificationFixture design verification is the technique to verify exist-ing fixture design by analyzing its geometric constraining ability,achieved tolerance, the deformation and stability of fixture-workpiece system, and fixturing accessibility, etc., and to providerelated improvement suggestions on the design 6265. Fixtureverification is an integrated part of the design process and mustallow for the detection of any interference that may occur dur-ing the fixtures construction. Verification of a fixture design solu-tion is necessary for the following reasons: (1) there are too manyfactors involved in the design process; it is very difficult to estab-lish accurate analysis models in the process. (2) Design constraintsare considered individually; some contradicting constraints maybe produced when they are considered together. (3) Fixture designhas a close relationship with other activities (such as Computer-Aided Process Planning, and Computer-Aided Manufacturing) ina manufacturing system; the design solution needs to be verifiedas practicable for the whole manufacturing system. Verification ormonitoring is also needed in the use of a fixture system to justifywhether the system is in a good condition. As the Fig. 13, Kang andRong have developed a methodology concept of computer aidedfixture design verification to unify various verification aspects intoa framework.In this field, the stability of the workpiece-fixture system, par-ticularly, the deformation and accuracy of the system, alwaysattracts most of the attention. Research on the stability of thefixture-workpiece system, can provide a mechanism for the defor-mation and error chain in the workpiece-fixture system which willguide the user to choose perfect fixtures, adjust suitable fixturingforces and fixture positions to generate adequate contact forces tokeep the workpiece in an accurate position during machining. Bycontrast, due to the fact that most research focuses on machiningfixtures where there is only one workpiece, seldom does researchput attention on the degree of freedom and geometric constraintsof whole system, even though this problem also is important in as-sembly related fixturing situations.Typical research on the stability of a workpiece-fixture systemneeds to model workpiece boundary conditions and applied loadsduringamachiningprocess,beforetheanalysisonthedeformationof a workpiece, as the work by Amaral et al. 66. However,they only considered the positions of locators and clamps, anddid not consider the deformation of fixtures in this process. Thetolerances are defined based on surface sample points, and theworkpiece-fixture system is assumed to be rigid. This kind ofworkpiece-fixture system for fixtures of rigid bodies and of pointcontacts without friction has been well described and studied inthe literature.However, in machining, particularly, in precision and ultra-precisionmanufacturing,theunderstandingofthesensitivitychar-acteristics of workpiece-fixture system could be of particularbenefit to the manufacture of intricate and/or precise parts ofcomplex shapes. So in the analysis and numerical simulation pro-cess, the stiffness of fixtures should be considered, and the contactmodel of the workpiece-fixture system also needs to be more ac-curate.Some significant efforts have been done in the modeling ofworkpiece-fixturecontact.Ratchevetal.73usedspringelementsto represent the point contact between the fixture and workpiece.And Asante 74 presented a surfacesurface contact model ofthe workpiece-fixture, and also considered the friction betweenthese surfaces, with the assumption that the contact interfacebetween the workpiece and locator/clamp obeys the laws of linearelasticity and so elastic deformation is the linear summation ofthe influence of all forces in the normal and tangential directionacting on the contact interface. Assuming a case of only singleworkpiece-fixture contact, Satyanarayana 71 have presenteda comparative analysis of the different boundary conditions contact elements (nodal and surface-to-surface), nodal boundaryconditions (nodal displacement constraint and nodal force) available for sphericalplanar and planarplanar contact models.However, they also regarded the fixture as a rigid body. Un-derstanding the stiffness model of the fixture unit is very useful1092H. Wang et al. / Computer-Aided Design 42 (2010) 108510946769, particularly when predicting the contact load and pres-sure distribution at the contact region in a workpiece-fixturesystem. Thus, this can help the designer very much in the detaileddesign of a fixture (including its shape, material, etc.), even thoughcurrently, the physical form of the design of the fixture usually de-pends on the geometric analysis from the designers experience.3.4. Deformation and error analysis of workpiece-fixture systemFixture positioning error has a direct impact on the machiningerrors of a workpiece. In this field, two problems have usually beendiscussed: one is the forward problem that involves predictingthe tolerance deviation resulting at a feature from a known setof errors on the locators and another is its inverse problem thatinvolvesestablishingboundsontheerrorsofthelocatorstoensurethat the limits specified by geometric tolerances at a feature arenot violated. So the essential problem is how to represent therelationship between the machining error, fixturing error and thedeformation of the workpiece-fixture system.Locator positional errors, locator surface geometric errors, andthe workpiece datum geometric errors can result in a localizationerror of the workpiece, which in turn yields a relational form errorin a machined feature. Fixture positioning error (or fixel error, byM.Y. Wang) comes mainly from three sources. (1) A variation inthe position of a locator is a direct contribution to the fixel errorof the locator (Asada and By, 1985; Wang, 2000). The variation isusually specified in the locators position tolerance defined duringthe fixture design. (2) Another source of fixel error is the variationin the geometric shape of the locator, such as profile tolerancespecified for a spherical locator. During operation, mechanicalwear and tear of the locator will also contribute to the fixel error.(3) The third source is related to geometric variations that mayexist in the physical datum features of the workpiece. The datumgeometricvariationswillhaveanequivalentresultoffixelerrorsinthereferenceframeembeddedintheworkpiecebody.Theprimaryobjectiveofafixturingschemeistoreducethemanufacturingerroras related to the three types of fixel errors that are essentiallycaused by the positional and geometric variability of the locatorsand the geometric variability of the workpiece itself.Inaccuracies in a fixtures location scheme result in a devia-tion of the workpiece from its nominal specified geometry (posi-tion and orientation of datum references). For a workpiece, thisdeviation must be within the limits allowed by the geometrictolerances specified. Various methods on controlling the manufac-turing errors have been suggested, for instance, (1) using stiffnessoptimized machining fixtures (and configuration layout) to ensurethe tolerance limit specified for the machined part surface 70;(2) during the manufacturing process, clamping forces of activefixtures can be adjusted according to the FEA analysis result tocompensate for machining errors 73, or (3) adjust suitable clampforces to generate adequate contact forces and pressure distribu-tion at the contact region to keep the workpiece in position duringmachining 74.However, modeling of a workpiece-fixture and the manufac-turing process using sophisticated FEM is usually affected by sev-eral basic sources of error which can lead to improper results:(1) poor input data due to the lack of information about the pro-cess, (2) unreasonable simplifications, idealization and assump-tions of the manufacturing process, (3) improper modeling of theboundary conditions, (4) numerical round-off (in solving the si-multaneousequations),(5)discretizationerrorand(6)errorsasso-ciated with re-mapping. Besides those sources, in the research ofthe relationship between machining error and fixture positioningerror, some assumptions on modeling the workpiece-fixture sys-tem also can affect the validity of the results. For instance, assum-ing that the workpiece-fixture system is a rigid body 76,70, andthe workpiece-fixture contact as a theoretical non-friction pointcontact 76.4. Conclusions and future researchRecent achievements in the development of computer aidedfixture design methodologies, systems and applications have beenexamined in this paper. Various novel papers in the computeraided fixture design field have been published in recent years, upto 2010. However, current design and automation theories andtechnologies are still not mature. Most current commercializedfixture design tools in manufacturing are traditional geometric-based,forinstance,thetoolingandfixturedesignfunctionsinsomeCAD systems, e.g., Unigraphics and Pro/Engineer, the software bysome fixture components manufacturers, e.g., Bluco Corp., JergensInc. They only provide engineers with a fixture component libraryor simple modules to do fixture design manually based on someextended functions of commercial CAD software. Fixture designstill continues to be a major bottleneck in the promotion of currentmanufacturing, though numerous innovative CAFD techniqueshave been proposed. Those techniques also need time to be testedand evaluated in real manufacturing environments and integratedwithotherproductandprocessdesignactivities.Therefore,severalresearch aspects are promising and challenging.4.1. To develop intelligent techniques for computer aided fixturedesignIt is already recognized that developing a computerized fixturedesign can result in high efficiency, stable accuracy, short set-uptime, and low cost. But the real performance of a computerizedfixture design system is rooted in a powerful ability of the sys-tem to replace or exceed that which is done manually by a fix-ture designer. For instance, an increasing research interest is usingvarious meta-heuristic methods to obtain optimal fixture layoutsolutions 5861, which often requires much precise calcula-tions in geometry and mechanics. Actually, computer supportedintelligent algorithms can have a better performance on thiskind of work. Meanwhile, deploying a multi-sensor network intoa workpiece-fixture system and using online intelligent controltechniques can adjust fixturing contacts and forces adaptively ina machining process to keep an optimal fixture-workpiece situa-tion 8486. That is an important reason for the rapid progress ofintelligent techniques on fixture design applications over the pastyears.Furthermore, recent achievements on some new knowledge-related techniques, such as knowledge modeling, data mining, ma-chine learning, and so on, indicate a more promising and fruitfulfutureforthedevelopmentofadvancedcomputeraidedfixturede-sign. In many manufacturing companies, the technical knowledgeof experienced fixture designers, a huge amount of technical filesandmanygooddesigncasesareaveryvaluableresourceforfixturedesign.Usingnewtechnologiesintheknowledgeengineeringfieldto refine, model and utilize fixture design domain knowledge as aninformation base for intelligent and automatic systems can assist afixturedesignernotonlybysimplifyingthedesignprocess,butalsobygeneratingdesignideas.Forexample,someinterestingprogresson using XML technology as a fixture knowledge representationtool to support case-based reasoning in the fixture design processis attractive, despite the reality that it need more effort on the sys-temization of intelligent techniques in fixture design 47,50.4.2. Integrated fixture design system for manufacturingIn essence, fixture design only is a partial process in manufac-turing, and it should obey to the total objective of workpiece man-ufacturing requirements which often are related with productionresources, equipment, cost and machining processes, etc. There-fore, it is necessary to put the fixture design task into an overallmanufacturing process to obtain best fixture design solution.H. Wang et al. / Computer-Aided Design 42 (2010) 108510941093Many researchers have accepted the viewpoint of integrationof CAFD systems with other manufacturing related technologies,even though many early researches are very limited in obtainingthe manufacturing requirements from and send the result offixture design to other systems, e.g. PDM or PLM systems. Futureresearch should emphasize the importance of more efficientintegration of fixture systems with other manufacturing systems.Particularly, view the fixture design as one node in a whole chainof manufacturing process. So we have to consider the impactof fixture design result on the cutting center and machiningtoolpath, and meanwhile, we also may find a necessary redesignof the fixture solution due to various conditions of cutting tools,production amount and cost, etc.Another important research is on the integration of varioustechniques directly used in computer aided fixture design. Aswe know, an optimal fixture solution is a hybrid result of manydifferent considerations, such as tolerance configuration, stiffnessconfiguration, machining process, etc. Thus more attention shouldalsobepaidontheestablishmentofasystematicwayofintegratingvarious techniques, such as FEM methods for workpiece-fixturesystem stiffness analysis, advanced mathematical analysis ontolerance design, 3D path planning and collision detection analysison the cutting toolpath.4.3. Applications in more wide manufacturing fieldsIt is apparent that almost all the literature is focused onmachining fixtures field beside a few on welding fixture research.This puts a question of the theoretical value of fixture researchin other industrial fields and a more rigid comparative study offixture design among those fields and the traditional machiningfield. In fact, besides the traditional machining field, there is awide usage of fixtures in other industrial fields, e.g., welding,assembly. And as we have motioned in Section 2.1, there existobvious different requirements. There is a clear demand for moreresearch in computerized fixture design in such fields.Another attractive field is fixture design in Micro and Nanoma-chining. Because nanometric machining has a very different phy-sics from conventional machining 87, e.g. in the manufacturingprocess, material and physical phenomena, existing fixture designmethodologies cannot handle the meso-scale fixturing problem.With respect to this, micro and nano scale fixturing technology ap-pears promising. Additionally, trends in manufacturing flexibilityand customized small production also suggest more deep compar-isons, analysis and research on the applications of computerizedmodular fixtures and dedicated fixtures.AcknowledgementsThe author would like to thank the anonymous referees whomade valuable comments that considerably improved the finalpaper. We also gratefully acknowledge the support from ShanghaiKey Lab of Mechanical Automation & Robot, Shanghai University.This research is supported in part by National Natural Sci-ence Foundation of China (Grant U0834002), the Fundamental Re-search Funds for the Central Universities in South China Universityof Technology (Grant 2009ZM0172 and 2009ZM0121), and Gov-ernment Research Program of Guangdong Province, China (Grant2008B010400005).References1 Bi ZM, Zhang WJ. Flexible fixture design and automation: review, issues andfuture direction. International Journal of Production Research 2001;39(13):286794.2 Nixon F. Managing to achieve quality. McGraw Hill: Maidenhead; 1971.3 RongYiming(Kevin),HuangSamuel.Advancedcomputer-aidedfixturedesign.Boston (MA): Elsevier Academic Press; 2005.4 Nee AYC, Whybrew K, Senthil Kumar A. Advanced fixture design for fms.London: Springer-Verlag; 1995.5 Cecil J. Computer-aided fixture designa review and future trends. Interna-tional Journal of Advanced Manufacturing Technology 2001;18(11):7903.6 Shen C-H, Lin Y-T, Agapiou JS, et al. Reconfigurable fixtures for automotiveengine machining and assembly applications. In: Dashchenko AI, editor.Reconfigurable manufacturing systems and transformable factories. Berlin:Springer Heidelberg; 2006. p. 15594.7 Liu YG, Hu SJ. Assembly fixture fault diagnosis using designated componentanalysis. Journal of Manufacturing Science and Engineering 2005;127(2):35868.8 Lien TK, Lind M. Instrumented fixtures for on-line correction of welding paths.In: The 41st CIRP conference on manufacturing systems. 2008. p. 4358.9 Sikstrom F, Ericsson M, Christiansson A-K. et al. Tools for simulation basedfixture design to reduce deformation in advanced fusion welding. In: The 1stInternational conference on intelligent robotics and applications. Part II. 2008.p. 398407.10 Li B, Shiu BW, Lau KJ. Principle and simulation of fixture configuration designfor sheet metal assembly with laser welding. Part 1: finite element modelingand a prediction and correction method. International Journal of AdvancedManufacturing Technology 2001;18(4):26675.11 Li B, Shiu BW, Lau KJ. Principle and simulation of fixture configurationdesign for sheet metal assembly with laser welding. Part 2: optimalconfiguration design with the genetic algorithm. International Journal ofAdvanced Manufacturing Technology 2001;18(4):27684.12 Li B, Shiu BW, Lau KJ. Fixture configuration design for sheet metalassembly with laser welding: a case study. International Journal of AdvancedManufacturing Technology 2002;19(7):5019.13 Li B, Shiu BW, Lau KJ. Robust fixture configuration design for sheetmetal assembly with laser welding. Journal of Manufacturing Science andEngineering 2003;125(1):1207.14 Ding Yu, Gupta Abhishek, Apley Daniel W. Singularity issues in fixturefault diagnosis for multistation assembly processes. Journal of ManufacturingScience and Engineering 2004;126(1):20010.15 KimPansoo,DingYu.Optimaldesignoffixturelayoutinmultistationassemblyprocesses. IEEE Transactions on Automation Science and Engineering 2004;1(2):13345.16 Li Z, Izquierdo LE, Kokkolaras M, et al. Multiobjective optimization forintegrated tolerance allocation and fixture layout design in multistationassembly. Journal of Manufacturing Science and Engineering 2008;130(4):044501-5044501-6.17 Rippey William. We need better information connections for weldingmanufacturing. NIST whitepaper; October 2004.18 American welding society and Edison welding institute. Economic impact andproductivity of welding. Heavy manufacturing industries Report. 2001.19 /.20 /.21 /.22 /.23 /.24 US Patent 7480975, Reconfigurable fixture device and methods of use./7480975.html.25 US Patent 5732194 Computer controlled reconfigurable part fixture mecha-nism. /5732194.html.26 US Patent 5249785 Reconfigurable holding fixture./5249785.html.27 Munro Chris, Walczyk Daniel. Reconfigurable pin-type tooling: a survey ofprior art and reduction to practice. Journal of Manufacturing Science andEngineering 2007;129(3):55165.28 Wu Yufeng. Geometry generation for computer-aided fixture design. Masterthesis. USA: Southern Illinois University at Carbondale; 2006.29 Wang Yan, Moor John, Wang Zhijian. Reconfigurable and ConformableFixtures.http:/www.nottingham.ac.uk/nimrc/research/new/advanced-manufacturing/ReconfigurableFixture.pdf.30 /index.php.31 /.32 ZhengY,QianW-H.A3-Dmodularfixturewithenhancedlocalizationaccuracyand immobilization capability. International Journal of Machine Tools andManufacture 2008;48(6):67787.33 Peng GL, Liu WJ. A novel modular fixture design and assembly system basedonVR.In:The2006IEEE/RSJinternationalconferenceonintelligentrobotsandsystems. Beijing (China); 2006. p. 26505.34 Peng GL, Wang GD, Chen YH. A pragmatic system to support interactivemodular fixture configuration design in desktop virtual environment. In:The 2008 IEEE/ASME international conference on advanced intelligentmechatronics. Xian (China); 2008. p. 1924.35 Peng GL, Wang GD, Liu WJ, et al. A desktop virtual reality-based interactivemodular fixture configuration design system. Computer Aided Design 2009;doi:10.1016/j.cad.2009.02.003.36 Senthil Kumar A, Fuh JYH, Kow TS. An automated design and assemblyof interference-free modular fixture setup. Computer-Aided Design 2000;32(10):58396.1094H. Wang et al. / Computer-Aided Design 42 (2010) 1085109437 Wua YG, Gao SM, Chen ZC. Automated modular fixture planning based onlinkage mechanism theory. Robotics and Computer-Integrated Manufacturing2008;24(1):3849.38 Mervyn F, Senthil Kumar A, Nee AYC. Automated synthesis of modular fixturedesigns using an evolutionary search algorithm. International Journal ofProduction Research 2005;43(23):504770.39 HouJL,TrappeyAJC.Computer-aidedfixturedesignsystemforcomprehensivemodular fixtures. International Journal on Production Research 2001;39(16):370325.40 Girish T, Ong SK, Nee AYC. Managing modular fixture elements with tabusearch in a web-based environment. International Journal of ProductionResearch 2003;41(8):166587.41 Lin ZC, Huang JC. The fixture planning of modular fixtures for measurement.IIE Transactions 2000;32(4):34559.42 Kakish Jamil, Zhang PL, Zeid Ibrahim. Towards the design and developmentof a knowledge-based universal modular jigs and fixtures system. Journal ofIntelligent Manufacturing 2000;11(4):381401.43 Cai Jin, Liu Hongxun, Duan Guolin, et al. TRIZ-based evolution study formodular fixture. In: Yan Xiu-Tian, et al., editors. Global design to gain acompetitive edge. London: Springer Press; 2008. p. 76372.44 Senthil Kumar A, Subramaniam V, Seow KC. Conceptual design of fixtures us-ing genetic algorithms. The International Journal of Advanced ManufacturingTechnology 1999;15(2):7984.45 Subramaniam V, Senthil Kumar A, Seow KC. A multi-agent approach to fixturedesign. Journal of Intelligent Manufacturing 2001;12(1):3142.46 Fan LQ, Senthil Kumar A, Mervyn F. The development of a distributed case-basedfixturedesignsystem.In:JapanUSAsymposiumonflexibleautomation.Colorado (USA): Denver; 2004.47 FanLQ,SenthilKumarA.XML-basedrepresentationinaCBRsystemforfixturedesign. Computer-Aided Design and Applications 2005;2(14):33948.48 Boyle Iain. CAFixDa case-based reasoning method for fixture design. Ph.D.dissertation. USA: Worcester Polytechnic Institute.49 Boyle Iain, Rong Kevin, Brown DC. CAFixD: a case-based reasoning fixturedesign method. Framework and indexing mechanisms. Journal of Computingand Information Science in Engineering 2006;6(1):408.50 Wang Hui, (Kevin) Rong Yiming. Case based reasoning method for computeraided welding fixture design. Computer-Aided Design 2008;40(12):112132.51 Chen GF, Liu WJ. Variant fixture design with CBR. in: 2002 Internationalconference on machine learning and cybernetics. Harbin (China); 2002.p. 14659.52 Wardak KR, Tasch U, Charalambides PG. Optimal fixture design for drillingthrough deformable plate workpieces. Part I: model formulation. Journal ofManufacturing Systems 2001;20(1):2332.53 Wardak KR, Tasch U, Charalambides PG. Optimal fixture design for drillingthrough deformable plate workpieces. Part II: results. Journal of Manufactur-ing Systems 2001;20(1):3343.54 Krishnakumar K, Melkote SN. Machining fixture layout optimization using thegenetic algorithm. International Journal of Machine Tools and Manufacture2000;40(4):57998.55 Krishnakumar K, Satyanarayana S, Melkote SN. Iterative fixture layoutand clamping force optimization using the genetic algorithm. Journal ofMa