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Computer aided fixture design: Recent research and trendsHui Wanga, Yiming (Kevin) Ronga,b, Hua Li b, Price Shaunba Department of Precision Instruments and Mechanology, Tsinghua University, Beijing, 100084, Chinab Computer Aided Manufacturing Laboratory, Worcester Polytechnic Institute, MA, 01609, USAarticleinfoArticle history:Received 7 April 2009 Accepted 15 July 2010Keywords:Computer aided fixture design Literature survey TrendabstractWidely used in manufacturing, fixtures have a direct impact upon product manufacturing quality, productivity and cost, so much attention has already been paid to the research of computer aided fixture design (CAFD) and many achievements in this field have been reported.In this paper, a literature survey of computer aided fixture design and automation over the past decadeis proposed. First, an introduction is given on the fixture applications in industry. Then, significant works done 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 reserved1. IntroductionA fixture is a mechanism used in manufacturing to hold a workpiece,position it correctly with respect to a machine tool, and support it during machining. Widely used in manufacturing, fixtures have a direct impact upon product quality, productivity and cost. Generally, the costs associated with fixture design and manufacture can account for 10%20% of the total cost of a manufacturing system 1. Approximately 40% of rejected parts are due to dimensioning errors that are attributed to poor fixturing design 2.Fixture design work is also tedious and time-consuming. It often heavily relies on fixture design engineers experience/knowledge and usually requires over 10 years manufacturing practice to design quality fixtures 3. Traditionally, the design and manufacture of a fixture can take several days or even longer to complete when human experience in fixture design is utilized. And a good fixture design is often based on the designers experience, his understanding of the products, and a try-and-error process. Fig. 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.) Fig. 4. Assembly fixture to locate shelves for assembly of cabinets (pioneer industrial systems . Fig. 5. Automotive stud weld fixtures on a trunion frame,Therefore, with the increasingly intense global competition which pushes every manufacturer in industry to make the best effort to sharpen its competitiveness by enhancing the products quality, squeezing the production costs and reducing the lead time to bring new products to the market, there is an strong desire for the upgrading of fixture design methodology with the hope of making sound fixture design more efficiently and at a lower cost. The development of computer-aided fixture design (CAFD) technology over the past decades can be attributed to the fulfilling of this goal.As an important field in manufacturing, research and applications of fixture design has been paid much attention over past decades 4,5. Many academic and applications papers have been published in this area. In this paper, we will focus on an investigation of computer aided fixture design research in the past decade.The following sections will give a survey on the state of the art of these researches. Some conclusions on research trends are also discussed.2. Fixtures in manufacturingA fixture is designed to position and hold one or more workpiece(s) within some specifications. It is widely used in manufacturing,e.g. machining (including turning, milling, grinding,drilling, etc), welding, assembly, inspection and testing. The following Figs. 19, are some real fixture design cases in manufacturing.Fixtures can be classified with different principles. However,compared with the publications of CAFD research in machining fixturefield, only a few 616 have been focused on other important manufacturing fields, for instance, assembly fixtures and welding fixtures.2.1. Welding fixturesWelding is essential to a high dollar volume of manufacturing processes, including national defense industries. According to Economic Impact and Productivity of Welding, Heavy Manufacturing Industries Report, by American Welding Society and Edison Welding Institute on June 2001, The contribution of welding to the US economy in 1999 via these industries was no less than $7.85 billion.This figure represented 7% of total expenditures by these firms in 1999 17,18. So there are significant technical and commercialadvantages in the development and deployment of welding fixture design systems.There are obvious differences between machining fixture design and welding fixture design. As in the following: The workpiece in a welding process is usually an assembly of several parts, while workpieces undergoing a machining process contain only one part. Usually, the accuracy requirement in a welding process is less than in machining. Fixing forces and machining forces in a welding process commonly are smaller than in machining. Thermal reactions in welding should be seriously considered. Furthermore, these factors also should be paid some attention in welding fixture design cases: Electrical conductivity is critical for arc welding stability. In addition to thermal conductivity, when selecting fixture material thermal expansion properties also should be considered. Refined welding waveforms require an optimized welding circuit to maintain short arc lengths while reducing spatter, stubbing, 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 involves installing and routing wiring and pneumatic or hydrauliclines.In the past decade, only very limited CAFD research and applications have been reported in the welding sector. In this field, due to the importance of welding for sheet metal assembly in automobile and aerospace industries, the assembly and welding of sheet metal has received some special attention. A weld fixture is often developed to reduce the deformation of each workpiece due to heat and residual stress in the welding process and, hence, to reduce the dimensional variation of the assembly. Therefore, some methods of offline or online deformation analysis were developed to enhance the fixtures ability on deformation controlling 8,9. In sheet metal assembly with laser welding fixtures also should ensure a fit-up of the mating surfaces to ensure proper laser beam weld operation and laser weld quality. As a result, a traditional 3-2-1 locating scheme is extended to a mixed locating idea, total locating and direct locating for welds 1013. The total locating scheme is used to locate the entire assembly, and the direct locating scheme is used to locate the weld joints to meet the metals fit-up requirement.2.2. Applications of modular fixtures and dedicated fixturesAccording to the fixtures flexibility, fixtures also can be classified as dedicated fixtures and general purpose fixtures (e.g. reconfigurable and conformable fixtures,modular fixtures). Reconfigurable and conformable fixtures 2426 can be configured to accept parts of varying shapes and sizes. Particularly, conformable pin-array fixture technology 27 is widely used in many fixture designs because some components contain internal variables that can be adjusted to meet the different features of workpieces (as Fig. 7).And phase-change materials-related fixtures also are used in some precision manufacturing. For instance, in the aerospace industry,low melting-point metals are used to enclose turbine blades and produce well-defined surfaces for part location and clamping for grinding operations. Fig. 6. Robot weld fixture (IMPROVE solutions LLC.) Fig. 7. Pin-array fixture application 29.Fig. 8. Modular fixture for a part for the construction machinery (BLUCO corp.) 30.Fig. 9. Dedicated fixture for a part for the construction machinery Fig. 10. A dedicated tube bending fixture (Winton machine company) 31.The most important and widest used within the general purpose fixture classifications are modular fixtures. As the flexible manufacturing system has been adopted by more and more manufacturers who are trying to remain competitive in this rapidly changing market by running production with short lead times and well controlled cost, modular fixtures have gained in popularity because of its performance on easy usage, versatility, and its adaptability to product changes. Fig. 11. The basic elements of the fixture design process.Modular fixtures allow a wider flexibility by making use of standard workholding devices and components. Their flexibility is derived from the large number of possible fixture configurations from the different combinations of fixture components. The application of modular fixtures contributes considerably to shortening the lead time and reducing the cost in small-volume production with versatile products. However, it also has some limitations 28: Only limited combinations can be achieved from these components,meaning that it is possible that no suitable combination can be built for some workpieces with irregular or complex geometries. Structural properties of modular fixtures are sometimes difficult to be maintained. Structural properties of modular fixtures include locating accuracy, stiffness, stability, loading and unloading, operating speed, etc. It is common that using modular fixtures may not achieve an optimal fixturing quality. Not suitable for mass production, e.g. automotive production and its components manufacture.For comparisons sake, Fig. 8 shows a modular fixture used for a part for the construction machinery, and the same part also used in Fig. 9, where a dedicated fixture solution is givenThe dedicated fixtures are also important in manufacturing,particularly, for advanced, sophisticated and precise part or mass production. Because a dedicated fixture is designed for a specific product, the designer can carefully tailor the design to not only meet the basic fixturing requirements such as the locating accuracy, stability, stiffness, but also optimally facilitate the operational requirements such as loading/unloading convenience and efficiency, and effective chip disposal etc. And Fig. 10 is a dedicated tube bending fixture.Compared with modular fixtures, dedicated fixtures are designed carefully according to workpieces design and manufacturing requirements. So there are more uncertainties imposed on dedicated fixture design tasks. In modular fixture design, there is a component library with pre-designed and dimensioned standardized fixture components. Thus, the modular fixture configuration design is actually to assemble the fixture components into a configuration.Due to its extensive use in current manufacturing and standardized production, in many reported CAFD researches and applications,modular fixturing principles are employed to generate fixture designs 3243. Early CAFD in modular fixtures merely used the drafting capabilities of a CAD system in assembly. Modular fixture elements such as baseplates, locators, supports and clamps are stored in a database. Based on the fixturing idea, first, the designer specifies the primary locating surface (point) and its locator positions, the suitable clamping surfaces and positions, and then selects and places the appropriate fixturing components in the desired positions. Although there is a reduction in the total time takento produce a fixture assembly, the final design depends largely on the designers experience. Thus they only provide fixture engineers with a simple tool to do fixture design manually based on some extended functions of commercial CAD software. As a result, current industrial applications of CAFD are very limited even though there are many reported research achievements.Over the past decade, much focus has been put on intelligent methods for computer aided fixture design to seek a technical breakthrough in embedding more design knowledge into semiautomatic or automatic CAFD systems. A detailed discussion will be 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, and support points, and the selection of the corresponding fixture elements for their respective functions. There are four main stages within a fixture design processsetup planning (D1), fixture planning (D2), fixture unit design (D3) and verification (D4), as Fig. 11 illustrates 48,63. Setup planning determines the number of setups required to perform all the manufacturing processes, the task for each setup, e.g., the ongoing manufacturing process and workpiece, orientation and position of the workpiece in each setup. A setup represents the combination of processes that can be performed on the workpiece by a single machine tool without having to change the position and orientation of the workpiece manually. During fixture planning, the surfaces, upon which the locators and clamps must act, as well as the actual positions of the locating and clamping points on the workpiece, are identified.The number and position of locating points must be such that the workpiece is adequately constrained during the manufacturing process. In the third stage of fixture design, suitable units, (i.e., the locating and clamping units, together with the base plate), are generated. During the verification stage, the design is tested to ensure that all manufacturing requirements of the workpiece can be satisfied. The design also has to be verified to ensure that it meets other design considerations that may include fixture cost, fixture weight, assembly time, and loading/unloading time of both the workpiece and fixture units 50.Currently, even though numerous techniques concentrating on fixture design have been proposed and made some achievementsmature and commercial CAFD applications also are very limited.Fixture design still continues to be a major bottleneck in the promotion of current manufacturing. This work currently, is implemented by a typical designer-centered pattern, that is, all fixture design related work is heavily dependant on the experience and knowledge of fixture designer. This situation hampers the improvement of productivity, requires a long time to cultivate an experienced fixture designer and make the fixture design job weak with a major bottleneck. Thus, new intelligent or automatic technologies on synthesizing traditional geometric design tools, design knowledge, and past design cases have attracted much interest in both academic institutions and industries. The efforts over past decades in this field have resulted in numerous computer aided fixture design (CAFD) applications using various intelligent methods, such as expert system, case based reasoning, and genetic algorithm (GA), etc.In essence, developing fixture design methodology needs to clear two crucial problems: how to represent fixture design knowledge in a computer and how to implement the problem solving procedure.At the initial stage of CAFD two decades ago, expert systems were often used as a heuristic tool, which can enlighten fixture designer to a complete fixture design solution, particularly, fixture configuration design in an interactive environment 82. In most of these methods, design knowledge is modeled as a set of many IF-THEN rules. Then, during the interactive fixture design process, the design solution would be concluded by a series of questioninganswering actions based on these rules. However, difficulties on building an enough completed rule set and the logic tree for reasoning procedure have an obvious impact on the design efficiency and the quality of the result. Furthermore, the interactive mode also makes the reasoning procedure very boring.In comparison, Case based reasoning (CBR) does not require so much complicated domain knowledge system as the expert system. It is mainly concerned on how to create a new solution by imitating past cases, based on the assumption that similar workpiece will have a similar fixture design solution. So first, it focuses on structuralizing fixture design cases and to emphasize some crucial data which will be the focus in measuring similarities. Then, the final solution will be generated by modifying the best similar design case according to case comparison. The CBR technique gives the possibility to avoid time-consuming and expensive experiments and is able to propose a good starting point for the detailed design (physical form) without many complicated calculations. Table 2 gives a comparison among some CBR methods in the past decade. Table 1Current CAFD literatureTwo techniques remain necessary and crucial in CBR. One is for an efficient method to refine, model and utilize fixture design domain knowledge (fixture design cases), and the other is for an effective technical system which can assist the fixture designer not only by simplifying the design process, but also by generating design ideas.The prevailing methods on case modeling are based on an attribute set. For example, Chen 51 used a case template to structuralize all fixture design cases, and Fan divided fixture design data into three attribute groups, part representation, setup representation and fixture representation. However, there are few guidelines on defining and choosing appropriate attributes. So this mostly relies on the designers experience: The designer selects some important attributes which he thinks are important to the current design case and use these attributes as a vector to compute and match stored cases. Thus, it results in a demand for systemizing fixture design domain knowledge to clarify the design requirement in CAFD. Therefore, Boyle 48,49 developed a methodology to classify fixture design information into two libraries: conceptual design information and fixture unit information. Furthermore, Hui re-organized fixture design information into three tiers: workpiece (design requirements), fixturing plan (fixture configuration) and fixture units.The fixture design domain knowledge representation has a crucial impact on the CBR procedure. Actually, a single CBR system using attribute similarity often has not a good performance on accurate results. Sometimes, the attributes which the designer determined this time do not fit the next time for case indexing, or a high similarity between cases does not necessarily result in a case that can be easily adaptedTable 2 Some CBR methods in CAFD The CBR procedure in most of those articles is similar, a cycle such as Aamodts classic model . But as a typical experienced based design process, after one cycle of CBR (without a designers interaction), current fixture design does not have a good performance on obtaining a good solution. That is why we proposed interactive multi-tier CBRs for a fixture design system 50. Multilevel CBRs, from rough indexing, solution configuration to physical form determination, each cycle the result can get a chance to update and become more close to the ideal result. Each time, after one CBR process completes case indexing and retrieval, the system will present the designer with a selection of cases for a detailed decision, rather than just one that is preferred more than any other. And the designer is required to select the preferred case(s) and determine what changes need to be made to solve the new case and how this change can be achieved. Hence, this is an interactive design process, that requires multiple rounds of CBR reasoning and human intervention before approximating the final solution.3.2. Generating optimal fixture configuration layoutsThe research of generating optimal fixture configuration layouts has received much attention in the CAFD community 5861, 1015. These layouts specify the optimumpositions where the fixture should contact the workpiece being machined. The main ideas are similar in these typical fixture layout optimization research articles (as Fig. 12). The first step is the application of the machining process analysis method to predict the machining forces exerted on the workpiece. This analysis is typically carried out for a large sample of cutting tool positions and orientations throughout the machining cycle. The second step is the deformation analysis of the fixture-workpiece system, utilizing the pre-determined load cases. Typically deformation analysis is based on the finite element method (FEM). The loads and the shape of the machined surface are calculated, and hence, the deformation of workpiece, under a given locating and clamping scheme, will be analyzed a to whether or not it is in an acceptable region. In general, if considering the clamping and machining forces over the entire machining process, by simulating the dynamic machining process, the analysis on workpiece deformation will be more accurate 54,55, with a cost of time-consuming computation. Finally, it will employ an optimization process (GA is mostly used) to search for a potential solution space and determine the locations of the fixtures within acceptable candidate regions with a minimized workpiece deformation56,57.Most of relevant works assumed some conditions: treat fixtureworkpiece contact as point contact 5457, the workpiece is deformable while the tools and fixtures are rigid. So one limitation of these methods is that they usually give a list of coordinates specifying where the fixture should be located, without providing the actual physical form of the fixture unit. Even though by considering more relevant factors, e.g., using the workpiece and process information, some performance criteria (ease of loading unloading, cost and rate of production), in the design process 44,45, fixture unit information also is a high level concept that only specifies its basic type and the nature of its components. Currently, the design of a physical form of fixture is geometric based and there is a long way to go before systemizing the research on automatic or intelligent fixture physical design.One interesting method is using the required height as the critical dimension for fixture unit generation, then to complete the detailed fixture shape. Particularly, this method is useful for modular fixture unit design where a fixture unit is usually assembled with several existing modular fixture components. So the fixture height can play a crucial role on searching potential elements to assemble. Fig. 12. Typical FEM based fixture design solution analysis framework 73.3.3. Fixture design verificationFixture design verification is the technique to verify existing fixture design by analyzing its geometric constraining ability, achieved tolerance, the deformation and stability of fixtureworkpiece system, and fixturing accessibility, etc., and to provide related improvement suggestions on the design 6265. Fixture verification is an integrated part of the design process and must allow for the detection of any interference that may occur during the fixtures construction. Verification of a fixture design solution is necessary for the following reasons: (1) there are too many factors involved in the design process; it is very difficult to establish accurate analysis models in the process. (2) Design constraints are considered individually; some contradicting constraints may be produced when they are considered together. (3) Fixture design has a close relationship with other activities (such as Computer- Aided Process Planning, and Computer-Aided Manufacturing) in a manufacturing system; the design solution needs to be verified as practicable for the whole manufacturing system. Fig. 13. Overview of fixture verification system 6265. Verification or monitoring is also needed in the use of a fixture system to justify whether the system is in a good condition. As the Fig. 13, Kang and Rong have developed a methodology concept of computer aided fixture design verification to unify various verification aspects into a framework.In this field, the stability of the workpiece-fixture system, particularly, the deformation and accuracy of the system, always attracts most of the attention. Research on the stability of the fixture-workpiece system, can provide a mechanism for the deformation and error chain in the workpiece-fixture system which will guide the user to choose perfect fixtures, adjust suitable fixturing forces and fixture positions to generate adequate contact forces to keep the workpiece in an accurate position during machining. By contrast, due to the fact that most research focuses on machining fixtures where there is only one workpiece, seldom does research put attention on the degree of freedom and geometric constraints of whole system, even though this problem also is important in assembly related fixturing situations. Typical research on the stability of a workpiece-fixture system needs to model workpiece boundary conditions and applied loads during a machining process, before the analysis on the deformation of a workpiece, as the work by Amaral et al. 66. However, they only considered the positions of locators and clamps, and did not consider the deformation of fixtures in this process. The tolerances are defined based on surface sample points, and the workpiece-fixture system is assumed to be rigid. This kind of workpiece-fixture system for fixtures of rigid bodies and of point contacts without friction has been well described and studied in the literature. However, in machining, particularly, in precision and ultraprecision manufacturing, the understanding of the sensitivity characteristics of workpiece-fixture system could be of particular benefit to the manufacture of intricate and/or precise parts of complex shapes. So in the analysis and numerical simulation process, the stiffness of fixtures should be considered, and the contact model of the workpiece-fixture system also needs to be more accurate.Some significant efforts have been done in the modeling of workpiece-fixture contact. Ratchev et al. 73 used spring elements to represent the point contact between the fixture and workpiece. And Asante 74 presented a surfacesurface contact model of the workpiece-fixture, and also considered the friction between these surfaces, with the assumption that the contact interface between the workpiece and locator/clamp obeys the laws of linear elasticity and so elastic deformation is the linear summation of the influence of all forces in the normal and tangential direction acting on the contact interface. Assuming a case of only single workpiece-fixture contact, Satyanarayana 71 have presented a comparative analysis of the different boundary conditions contact elements (nodal and surface-to-surface), nodal boundary conditions (nodal displacement constraint and nodal force) available for sphericalplanar and planarplanar contact models.However, they also regarded the fixture as a rigid body. Understanding the stiffness model of the fixture unit is very useful6769, particularly when predicting the contact load and pressure distribution at the contact region in a workpiece-fixture system. Thus, this can help the designer very much in the detailed design of a fixture (including its shape, material, etc.), even though currently, the physical form of the design of the fixture usually depends on the geometric analysis from the designers experience3.4. Deformation and error analysis of workpiece-fixture systemFixture positioning error has a direct impact on the machining errors of a workpiece. In this field, two problems have usually been discussed: one is the forward problem that involves predicting the tolerance deviation resulting at a feature from a known set of errors on the locators and another is its inverse problem that involves establishing bounds on the errors of the locators to ensure that the limits specified by geometric tolerances at a feature are not violated. So the essential problem is how to represent the relationship between the machining error, fixturing error and the deformation of the workpiece-fixture system. Locator positional errors, locator surface geometric errors, and the workpiece datum geometric errors can result in a localization error of the workpiece, which in turn yields a relational form error in a machined feature. Fixture positioning error (or fixel error, by M.Y. Wang) comes mainly from three sources. (1) A variation in the position of a locator is a direct contribution to the fixel error of the locator (Asada and By, 1985; Wang, 2000). The variation is usually specified in the locators position tolerance defined during the fixture design. (2) Another source of fixel error is the variation in the geometric shape of the locator, such as profile tolerance specified for a spherical locator. During operation, mechanical wear and tear of the locator will also contribute to the fixel error. (3) The third source is related to geometric variations that may exist in the physical datum features of the workpiece. The datum geometric variations will have an equivalent result of fixel errors in the reference frame embedded in the workpiece body. The primary objective of a fixturing scheme is to reduce the manufacturing error as related to the three types of fixel errors that are essentially caused by the positional and geometric variability of the locators and the geometric variability of the workpiece itself.Inaccuracies in a fixtures location scheme result in a deviation of the workpiece from its nominal specified geometry (position and orientation of datum references). For a workpiece, this deviation must be within the limits allowed by the geometric tolerances specified. Various methods on controlling the manufacturing errors have been suggested, for instance, (1) using stiffness optimized machining fixtures (and configuration layout) to ensure the tolerance limit specified for the machined part surface 70; (2) during the manufacturing process, clamping forces of active fixtures can be adjusted according to the FEA analysis result to compensate for machining errors 73, or (3) adjust suitable clamp forces to generate adequate contact forces and pressure distribution at the contact region to keep the workpiece in position during machining 74. However, modeling of a workpiece-fixture and the manufacturing process using sophisticated FEM is usually affected by several basic sources of error which can lead to improper results:(1) poor input data due to the lack of information about the process,(2) unreasonable simplifications, idealization and assumptions of the manufacturing process, (3) improper modeling of the boundary conditions, (4) numerical round-off (in solving the simultaneous equations), (5) discretization error and (6) errors associated with re-mapping. Besides those sources, in the research of the relationship between machining error and fixture positioning error, some assumptions on modeling the workpiece-fixture system also can affect the validity of the results. For instance, assuming hatt the workpiece-fixture system is a rigid body 76,70, and the workpiece-fixture contact as a theoretical non-friction point contact 76.4. Conclusions and future researchRecent achievements in the development of computer aided fixture design methodologies, systems and applications have been examined in this paper. Various novel papers in the computer aided fixture design field have been published in recent years, up to 2010. However, current design and automation theories and technologies are still not mature. Most current commercialized fixture design tools in manufacturing are traditional geometricbased, for instance, the tooling and fixture design functions in some CAD systems, e.g., Unigraphics and Pro/Engineer, the software by some fixture components manufacturers, e.g., Bluco Corp., Jergens Inc. They only provide engineers with a fixture component library or simple modules to do fixture design manually based on some extended functions of commercial CAD software. Fixture design still continues to be a major bottleneck in the promotion of current manufacturing, though numerous innovative CAFD techniques have been proposed. Those techniques also need time to be tested and evaluated in real manufacturing environments and integrated with other product and process design activities. Therefore, several research aspects are promising and challenging.4.1. To develop intelligent techniques for computer aided fixture designIt is already recognized that developing a computerized fixture design can result in high efficiency, stable accuracy, short set-up time, and low cost. But the real performance of a computerized fixture design system is rooted in a powerful ability of the system to replace or exceed that which is done manually by a fixture designer. For instance, an increasing research interest is using various meta-heuristic methods to obtain optimal fixture layout solutions 5861, which often requires much precise calculations in geometry and mechanics. Actually, computer supported intelligent algorithms can have a better performance on this kind of work. Meanwhile, deploying a multi-sensor network into a workpiece-fixture system and using online intelligent control techniques can adjust fixturing contacts and forces adaptively in a machining process to keep an optimal fixture-workpiece situation 8486. That is an important reason for the rapid progress of intelligent techniques on fixture design applications over the past years. Furthermore, recent achievements on some new knowledgerelated techniques, such as knowledge modeling, data mining, machine learning, and so on, indicate a more promising and fruitful future for the development of advanced computer aided fixture design. In many manufacturing companies, the technical knowledge of experienced fixture designers, a huge amount of technical files and many good design cases are a very valuable resource for fixture design. Using new technologies in the knowledge engineering field to refine, model and utilize fixture design domain knowledge as an information base for intelligent and automatic systems can assist a fixture designer not only by simplifying the design process, but also by generating design ideas. For example, some interesting progress on using XML technology as a fixture knowledge representation tool to support case-based reasoning in the fixture design process is attractive, despite the reality that it need more effort on the systemization 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 manufacturing, and it should obey to the total objective of workpiece manufacturing requirements which often are related with production resources, equipment, cost and machining processes, etc. Therefore, it is necessary to put the fixture design task into an overall manufacturing process to obtain best fixture design solution.Many researchers have accepted the viewpoint of integration of CAFD systems with other manufacturing related technologies, even though many early researches are very limited in obtaining the manufacturing requirements from and send the result of fixture design to other systems, e.g. PDM or PLM systems. Future research should emphasize the importance of more efficient integration of fixture systems with other manufacturing systems. Particularly, view the fixture design as one node in a whole chain of manufacturing process. So we have to consider the impact of fixture design result on the cutting center and machining toolpath, and meanwhile, we also may find a necessary redesign of the fixture solution due to various conditions of cutting tools, production amount and cost, etc. Another important research is on the integration of various techniques directly used in computer aided fixture design. As we know, an optimal fixture solution is a hybrid result of many different considerations, such as tolerance configuration, stiffness configuration, machining process, etc. Thus more attention should also be paid on the establishment of a systematic way of integrating various techniques, such as FEM methods for workpiece-fixture system stiffness analysis, advanced mathematical analysis on tolerance design, 3D path planning and collision detection analysis on the cutting toolpath.4.3. Applications in more wide manufacturing fieldsIt is apparent that almost all the literature is focused on machining fixtures field beside a few on welding fixture research. This puts a question of the theoretical value of fixture research in other industrial fields and a more rigid comparative study of fixture design among those fields and the traditional machining field. In fact, besides the traditional machining field, there is a wide usage of fixtures in other industrial fields, e.g., welding, assembly. And as we have motioned in Section 2.1, there exist obvious different requirements. There is a clear demand for more research in computerized fixture design in such fields. Another attractive field is fixture design in Micro and Nanomachining. Because nanometric machining has a very different physics from conventional machining 87, e.g. in the manufacturing process, material and physical phenomena, existing fixture design methodologies cannot handle the meso-scale fixturing problem. With respect to this, micro and nano scale fixturing technology appears promising. Additionally, trends in manufacturing flexibility and customized small production also suggest more deep comparisons, analysis and research on the applications of computerized modular fixtures and dedicated fixtures.AcknowledgementsThe author would like to thank the anonymous referees who made valuable comments that considerably improved the final paper. We also gratefully acknowledge the support from Shanghai Key Lab of Mechanical Automation & Robot, Shanghai University. This research is supported in part by National Natural Science Foundation of China (Grant U0834002), the Fundamental Research Funds for the Central Universities in South China University of Technology (Grant 2009ZM0172 and 2009ZM0121), and Government Research Program of Guangdong Province, China (Grant 2008B010400005).References1 Bi ZM, Zhang WJ. Flexible fixture design and automation: review, issues and future direction. 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London:Springer-Verlag; 2008.Computer-Aided Design 2010（12）,42（12）;10851094.计算机辅助夹具设计：近期研究和发展趋势王慧, 荣一鸣, 李华,布莱斯.肖恩1、精密仪器与机械，清华大学，北京，100084，中国一系2、计算机辅助制造实验室，伍斯特理工学院，MA，01609，USA文章资讯文章历史：收到日期：2009年4月7日；接收日期：2010年7月15日。关键词：计算机辅助夹具设计文献调查趋势。摘要 夹具广泛应用于制造业，对产品的质量，生产效率和成本有直接的影响，受到了广泛的关注，投入了大量资金用于计算机辅助夹具的研究，并且取得了显著的成果。在本文中，是对“计算机辅助夹具的设计”过去十年的文献调查和一些建议。首先，将介绍工业夹具设计的应用程序。然后，在夹具CAD领域所做的显著贡献，并对他们的设计方法、要求和工作原理进行了讨论。最后，对一些前瞻性的研究进行了讨论1、简介夹具是制造过程中用于固定工件并在加工过程中支撑它的机构，对产品的质量、生产效率和成本有很大的影响，在制造中被广泛使用。一般来说，与夹具设计和制造相关的成本占总制造成本的10%-20%。大约40%的不合格产品是由于劣质的夹具造成的。夹具设计工作是繁琐及费时的。它很大程度上需要依赖夹具设计工程师的经验和知识，一般来说设计合格的夹具需要10年以上的生产实践。传统上，人们利用夹具设计的经验完成一个夹具的设计制造需要花费好几天甚至更多的时间。而且通常一个好的夹具设计需要设计者的经验，对产品的理解和一个不断尝试失败的过程。因而，随着日益激烈的市场竞争，工业制造商们尽力提高产品的质量，缩短生产周期，降低制造成本来保证产品的竞争力，并将新产品投入市场。人们对利用较低成本进行更有效率的夹具设计有着强烈的愿望。过去十年计算机辅助设计技术的发展使这一目标有了实现的可能。作为制造中的重要领域，夹具设计的研究和应用在过去十年中得到了更多的关注。人们在这一领域中发表了许多学术和应用文献。该文中，我们将集中于调查过去十年中的计算机辅助夹具设计的研究。下面的版块中，我们会给出关于这些研究技术的调查，并描述了一些研究方向的结论。2.夹具制造夹具是设计用来定位和固定一个或多个工件的，它有很多的规格。它被广泛应用于制造过程中，如：加工（包括车削、铣削、磨削、钻孔等）、焊接、装配、检测和试验。下面图1-9是一些真实的夹具设计案例。夹具可以通过不同的原理来分类。然而，与机床夹具领域发表的有关计算机辅助夹具设计的研究相比，只有小部分（6-16）集中在其他重要的制造领域，例如，装配夹具和焊接夹具。2.1焊接夹具焊接对制造业中包括国防工业等占很大比重的行业具有重要意义。根据美国焊接协会和爱迪生焊接协会2001年6月发布的“焊接重工业的生产和经济影响”的报告，1999年焊接通过这些行业对美国经济的贡献超过了78.5亿美元。这个数字代表着这些企业1999年总支出的7%。因而焊接夹具设计系统的开发和部署有着重大的技术和商业优势。图1. 机加工夹具图2. 飞机端盖轴承的机加工夹具图3.涡轮叶片的磨夹具图4. 组装夹具用于定位橱柜装配中的架子图5. 凹耳框架上的汽车焊接夹具螺机加工夹具设计和焊接夹具的设计有很大的不同，如下所列：1、焊接过程的工件通常是由几个部件装配而成的，而机加工过程中的工件通常只有一个部件2、通常焊接过程的精度要求要比机加工低3、焊接过程一般来说夹紧力和加工力要比机加工的小4、焊接过程需要充分考虑热反应再者，焊接夹具设计案例中还要考虑下面的问题：1、导电性对焊接稳定性是十分重要的2、除了导热性之外，夹具材料的选择还要考虑热膨胀性。3、精确的焊接波形要求具有优化的焊接电路可以保持短电弧的长度同时减少喷涂、硬物、电弧光斑和电弧中断，使运行速度最大4、更复杂的应用需要一个专用夹具。专用夹具的设计和安装包括安装路由线路和气动或液压线在过去的十年中，在焊接领域只报道了有限的计算机辅助夹具设计的研究和应用。在该领域，根据焊接钣金装配在汽车、航天等行业的重要性，钣金的焊接和装配将得到一些特殊的关注。焊接夹具通常开发用来减少每个工件由于加热和焊接中的残余应力所产生的变形，以此来减少装配的尺寸变化。因而，一些离线或在线的变形分析方法被开发出来加强夹具对变形控制的能力。在钣金激光焊接夹具的装配红，也要保证一个配合的表面，以保证正常的激光焊接操作和激光焊接质量。结果，一个传统的“3-2-1”定位方案扩展到混合定位方案“焊接的总定位和直接定位”。总定位用来定位整个装配，而直接定位用来定位焊接点和焊接配合面的要求。2.2 模块夹具和专用夹具的应用根据夹具的柔性，夹具也可分为专用夹具和通用夹具。重组和整合夹具可以适用于不同形状和尺寸的零件。特别的，整合pin阵列夹具技术被广泛用于各种夹具设计中，因为组件包含的内部变量可以随着工件的不同特点而掉正。而且与材料相关的变向夹具可以使用同样的精度。例如，在航空工业中，低熔点的金属被用来包裹涡轮叶片并产生磨削过程中零件位置和装夹的明确表面。最重要且使用最广泛的夹具是模块夹具。随着柔性制造系统越来越多被那些通过缩短生产周期和降低生产成本来试图在这个快速变化的市场中保持竞争力的生产商所适应，模块夹具因其所有的使用方便、通用性能强、对产品变化适应性强的特点，越来越受欢迎。图6. 机器人焊接夹具图7. Pin矩阵夹具应用图8.工程机械零件的模块夹具图9.工程机械零件的专用夹具图10.一个专用的弯管夹具通过使用标准工件夹紧装置和部件，模块夹具具有更大的灵活性。它的灵活性是从不同夹具元件的组合产生大量可能的夹具配置推导出的。模块夹具的应用对缩短生产周期和降低通用产品的小体积产品的成本贡献很大。然而，它也存在局限性：从这些组件中只能得到有限的组合，意味着对某些复杂不规则的工件来说无法得到合适的组合。模块夹具的结构特性有事难以维持。模块夹具的结构特性包括定位精度、刚度、稳定性、装卸、运转速度等等。使用模块夹具很可能无法获得最优的质量。不适合大批量生产，如汽车生产及其组件制造。为了进行比较，图8显示了一个模块夹具用于工程机械的零件，而同一个零件在图9中使用的是专用夹具。专用夹具在制造中同样很重要，由其在先进、成熟和精密零件或质量的生产中。因为专用夹具是为某一特定产品设计的，设计者不仅可以使夹具满足基本的定位精度、刚度、稳定性夹具要求，还可以优化促进装卸方便、效率、芯片的有效处理等等运行要求。图11.夹具设计过程的基本元素与模块夹具相比，专用夹具需要根据工件的设计和制造要求仔细的设计。因而在专用夹具的设计任务中有更多的不确定性。在模块设计中，有一个有着预设计的定尺寸的标准夹具元件的组件库。因此，模块夹具的结构设计其实是将夹具元件装配起来。由于目前它广泛应用于生产制造和标准产品中，在很多发表的计算机辅助夹具设计研究和应用中，采用模块夹具原理来进行夹具设计。早期在模块设计中计算机辅助夹具设计仅仅使用的是CAD系统装配图的绘制能力。模块夹具元素如底板、定位、支撑和爪被储存在数据库中。基于夹具理念，首先，设计师指定主要定位表面及其定位器的位置，合适的装夹表面及位置，接着在要求的位置上选择放置合适的夹具组件。虽然在产生夹具配置的总时间上得以减少，但最后的设计很大程度上依赖于设计师德经验。因而他们只给设计工程师提供很简单的工具，而设计师们基于一些商业CAD软件扩展功能的基础上进行手动夹具设计。结果，即使有着许多的研究成果，但目前计算机辅助夹具设计在工业上的应用仍旧十分局限。在过去的十年中，为了寻求将更多的设计知识转化为半自动或自动计算机辅助夹具设计系统的技术突破，人们将更多的注意力集中到计算机辅助夹具设计的智能方法上。在下面的版块中会做具体的描述。（表1）3.现有技术水平3.1 智能和自动夹具设计方法典型的，夹具设计包括了爪、定位器、支撑点的确认和有着对应功能的相应夹具元件的选择。夹具的设计过程主要由四个阶段机构设计（D1），夹具设计（D2），夹具装置设计（D3）和检验（D4），如图11所示。机构设计过程决定了完成整个制造过程需要的机构数目以及每个机构的任务，如工件和正在进行的生产工艺，每个机构中工件的位置和方向。一个机构代表着不需要手动进行工件的位置和方向的调整就可以通过一个小的机械工具节能型工件上工艺的结合。在夹具设计过程中，需要确定定位和夹紧操作的表面以及工件上准确的定位位置和夹紧点。在制造过程中定位点的位置和数量必须保证工件的完全约束。在第三个夹具设计阶段，生成了合适的装置。在检验阶段，要保证工件的所有制造要求都能满足。设计也必须核实以保证它能满足其他设计的要求包括夹具成本、夹具重量、装配时间和工件与夹具装置的装卸时间。目前，尽管已经提出了许多的夹具设计的技术并缺的了一些成就，成熟的与商业的计算机辅助夹具设计应用仍然很有局限性。现有生产制造的推广中，夹具设计仍旧是一个主要的瓶颈。目前这项工作仍旧是传统的设计者集中模式，所有的夹具设计的相关工作很大程度上依赖于设计者的经验和知识。这种情况制约了生产率的提高，培养一个夹具设计者需要很长的实践使夹具设计工作成为一个主要的瓶颈。因而，综合传动几何设计工具、设计知识和过去设计案例额的新型智能和自动化技术在学术和工业上都获得了过多的关注。该领域中过去十年的成果以使用不同智能方法的多样的计算机辅助夹具设计应用表现，如专家系统、基于计算机扶着软件工程的推理以及遗传算法等。在本质上说，开发夹具设计方法需要解决2个主要的问题：如何在计算机中体现家具设计知识以及如何实行问题的解决程序。20年前在计算机辅助夹具设计的初始期，专家系统常被当做启发工具使用，可以引导夹具设计者获得完全的夹具设计的解决方案，尤其是在一个交互环境中的夹具结构设计。在大多数的这些方法中，设计知识是根据一套假设规则模仿的。因而，在交互夹具设计阶段，设计解决方法会通过一系列基于这些规则的问答板块得出。然而，建立一个对设计效率和结果质量有明显影响的推论程式的足够完全的规则集和逻辑树是很难的。此外，交互模块同样使推论程式显得很无聊。表1. 目前的计算机辅助夹具设计文献与专家系统相比，CBR不需要如此多复杂的领域知识系统。它主要集中于通过模仿过去的案例，基于假定有一个相似夹具设计结局方法的相似工件来创建一个新的结局方法。因此，首先，他侧重于构造夹具设计案例并强调集中于测量相似性的一些重要数据。接着，将会通过比较案例并修改最佳的方案来生成最终的结局方案。CBR技术可以避免耗时及昂贵的实验，并且不需要太多的复杂结论就可以为具体的设计提供一个好的起点。表2给出了过去十年中一些CBR方法的比较。在CBR中2个技术仍旧是重要及必须的。一个是一种有效提炼、建模和利用夹具设计知识的方法，另一种是一个有效的技术系统可以帮助夹具设计者简化设计过程并生成设计方案。现在流行的案例建模方法是基于属性集得。Chen使用了一个案例模板来综合所有的夹具设计案例，Fan将夹具设计分成3个属性组，零件描述、设置描述及夹具描述。然而，很少有定义和选择合适的属性的指导方法。所以这很大程度上依赖于设计者的经验：设计者选择一些他认为对目前的设计案例很重要的属性并将它作为一个计算和搭配储存案例的矢量。因而，它以系统化夹具设计领域相关知识的要求表现来定义计算机辅助设计的设计要求。因此，Boyle开发了一个方法来定义夹具设计信息在2个信息库中：概念设计信息以及夹具单元信息。此外，会将夹具设计信息重组成三个块：工件、夹具计划和夹具单元。表2.一些计算机辅助夹具设计中的CBR方法过程信息，一些性能指标。在设计过程中，夹具单元信息同样是可以明确其基夹具设计领域知识体现对CBR程序有个很重要的影响。事实上，一个单独使用形似属性的CBR系统通常无法获得精确的结果。有时，这次设计者设置的属性不能满足下个案例索引，或者案例间高度的相似性不一定能简单的适应一个案例。大多数文章中的CBR程序是相似的，如Aamodt的经典模型的一个周期。但作为一个传动的基于经验的设计过程，在CBR的一个周期后，现在的夹具设计并不能获得一个好的解决方案。这就是我们为什么提出一个交互多层CBR夹具设计系统。多层次CBR通过粗索引、解决方法配置来确定物理形式，每个周期的结束可以获得一个更新的机会并接近结果。每一次，在一个CBR程序完成案例索引和检索后，系统将会提供给设计者一个具体结果的案例选择，而不是仅仅提供最优的。接着设计者要选择较好的案例并提出哪些地方需要改进并如何改进来解决新案例。因此，这是一个可选择的设计过程，需要多轮的CBR检索和人为操作来获得最终的解决方案。3.2 最优夹具配置布局的生成在CAFD区域中最优夹具配置布局生成的研究获得了很大的关注。这些布局指定了夹具接触加工中零件的最佳位置。主要内容与这些传动夹具配置布局文章相似（如图12所示）。第一步是通过加工过程分析方法的应用来求出工件上的加工受力。该分析通常是进行大量加工周期中刀具位置和方向的试验。第二步是利用预先确定的工况来进行夹具工件的变形分析。传统的变形分析是基于有限元法的。算出负载和加工表面的形状，接着在给定的固定和装夹方案下，就可分析出工件变形是否在允许的范围内。一般来说，如果考虑整个加工过程中的夹紧力和加工力，对动态加工过程进行数字模拟，长时间计算后工件变形的分析会更为精确。最后，它使用一种最优化方法来寻找一种潜在解空间，并确定允许范围内具有最小变形的工件位置。大多数相关的工作都需要一些假设条件：将夹具工件的接触看成点接触。工件是可变性的而刀具和夹具是刚性的。因此这些方法的一个局限性在于它们通常给出一个夹具定位的指定坐标的列表而没有提供实际性质的夹具单元。即使考虑更多的相关因素，如：使用工件和本类型和组件性质的重要概念。目前，夹具物理形态的设计是以几何为基础的，夹具物理设计的自动化及智能化的系统研究仍有很长的路要走。一种有趣的方法是使用需要的高度作为夹具单元系列的标准尺寸，然后完成具体的夹具形状。特别的，这种方法常用于夹具单元与几个存在的模块夹具元件相配合的模块夹具单元设计。因此夹具的高度在寻找潜在装配元素的时候起到了重要的作用。图12.传统的基于FEM的夹具设计方案分析框架3.3 夹具设计验证夹具设计验证是一项通过分析它的几何驱动能力、完成公差、变形、夹具工件系统的稳定性以及装夹目标完成性等来验证完成的夹具的设计的技术，同时它提供了设计相关的改进意见。夹具验证是夹具设计过程的一个整合部分，需要能检测出夹具建造过程中发生的任何冲突。出于以下几点，夹具设计的方案需要经过验证：（1）设计过程中有太多的因素；在过程中很难建立确切的分析模块。（2）设计的约束条件需要单独考虑；当一起考虑时可能产生一些矛盾的约束条件。（3）在一个制造系统中夹具设计与其它过程有密切的联系（如计算机辅助过程设计和计算机辅助制造）；设计方案需要验证能用于整个制造系统。在夹具系统的使用中为了判断系统是否处于良好状态，同样需要进行验证或监视。如图13所示，Kang和Rong开发了一个计算机辅助夹具设计验证的方法论将各种各样的验证方面统一在一个方框中。图13.夹具验证系统的图框在该领域中，工件夹具系统的稳定性尤其是系统的变形和精度需要更多的关注。夹具工件系统稳定性的研究可以给工件夹具系统的变形和错误链提供一个机构，而工件夹具系统将会引导使用者选择完美的夹具，调整为合适的夹紧力和装夹位置来使加工中的工件保持一般合适的接触力并处于正确的位置上。通过比较，根据大多数研究集中在只有一个工件且很少关注整个系统的自由度和约束条件的机械夹具，即使在装配相关夹具时该问题也很重要。根据Amaral等人的工作，在工件变形分析之前，传动的工件夹具系统的稳定性研究需要模块化工件边界条件并提供加工过程中的负载。然而，他们只考虑了定位和爪的位置，并没有考虑到这个过程中夹具的变形。公差是基于表面样本点定义的，而该工件夹具系统是刚性的。这种刚性夹具和无摩擦接触点的工件夹具系统在文献中被大量描述和研究。然而，在加工制造尤其是精密和超精密加工制造中，工件夹具系统的灵敏性的理解将很有利于加工复杂的零件或形状复杂的精密零件。所以在分析和数值仿真过程中，需要考虑装置的刚度，且工件夹具系统的接触模型同样需要更为精确。在工件夹具的建模上人们花费了很大的努力。Ratchev等人使用弹簧座代表夹具和工件之间的点接触。Asante提出了一种面与面接触的工件夹具模型，并考虑了这些面之间的摩擦。假设工件和定位板/爪之间的接触接口满足弹簧线性特征，所以弹性变形是作用于接触界面正向和切向的所有力的线性影响。假设一个单一情况的工件夹具接触，Satyanarayana提出了一个不同边界条件的比较分析接触单元、节点边界条件可用于球面-平面和平面-平面的接触模型。然而，他们仍然认为夹具是刚性体。理解夹具单元的刚度模型，尤其当预测工件夹具系统中接触须臾的接触负载和压力分部时是很有用的。因而，在夹具的具体设计时这可以帮到设计者很多，尽管目前来说，夹具设计的物理模型通常依靠设计者经验的几何分析。3.4 工件夹具系统的变形和错误分析夹具的位置错误对工件的加工错误有直接影响。在该领域，2个问题常被拿来讨论：一个是从一个已知定位误差来预测误差产生的误差特性，另一个相反则是通过建立定位误差界限来保证利用几何公差的限度标准在一个不能违反的特征内。所以实质问题是如何表现加工误差，装夹误差和工件夹具系统的变形之间的关系。定位器位置误差，定位器表面几何误差和工件的基准几何误差可以通过工件的定位误差来体现，从而转化成一个机加工特性中的产量形状误差。夹具定位误差主要从3个方面获得。（1）定位器的位置变化是定位器装夹误差的直接原因。在夹具设计时，该变化通常被指定在一定的位置公差内。（2）另一个原因是定位器几何形状的变化，如一个指定球形定位器的轮廓公差。在加工过程中，定位器的机械磨损同样会引起装夹误差。（3）第三个原因是工件物理数据特性中可能存在的几何变化。基准几何变化和装夹误差对工件本体的参考框架嵌入式有同样的影响。装夹方案的主要目标是降低制造误差包括本质上由定位器的位置和几何变化以及工件本身的几何变化所引起的三种装夹误差。夹具定位方案的不精确会引起工件的几何偏差。对一个工件来说，这个偏差必须在规定的几何公差所允许的范围内。许多控制制造误差的方法已经被提出了，例如，（1）使用刚度优化加工夹具来保证加工零件表面规定的公差界限；（2）在制造过程中，现有夹具的夹紧力可以通过FEA分析来调整继而补偿加工误差，或者（3）调整合适的夹紧力来产生一般的接触力和接触区域的压力分布来保持加工过程中的工件位置。然而，使用复杂FEM的工件夹具模型和制造过程通常会被基本的误差来源所影响，引起不良结果：（1）由于过程信息的缺失引起的数据输入错误，（2）制造过程不合理的简化、理想化和假设，（3）边界条件的不当建模，（4）数值四舍五入，（5）离散化误差，（6）重组误差。除了这些原因外，在加工误差和夹具位置误差之间关系的研究中，一些工件夹具系统模型的假设同样可以引起结果的变化。例如，假设工件夹具系统是刚性的物体，并且工件夹具接触是一个理想的无摩擦点接触。4、结论与未来研究计算机辅助夹具设计方法、系统和应用的发展的近期成果在该文中已做了介绍。至2010年为止，最近几年，人们发表了各种计算机辅助夹具设计的文献。然而，目前的设计和自动化理论与技术仍不成熟。目前大多数制造过程中的商业化的夹具设计工具是传统的基于几何学的，例如，一些CAD系统中的模具和工装的设计功能等，UG和PRO/E，一些夹具制造商的软件等，Bluco 公司、Jergens公司。他们只给工程师提供了一个夹具组件库或者简单的模型来进行基于一些商业CAD软件的扩展功能手动的夹具设计。在现代制造的发展中夹具设计仍然是一个主要的瓶颈，尽管许多先进的CAFD技术已经被提出。那些技术同样需要时间的检验和实际制造环境中的评估并需要与其它产品和工艺设计活动相结合。因而，这几个研究方面是有前途且富有挑战性的。4.1 开发智能计算机辅助夹具设计技术人们已经意识到计算机夹具设计的开发可以获得高效率，稳定精度，短生产时间以及低成本。但真正的计算机夹具设计系统的性能是基于强力的系统能否“替换”或超过一个设计师收工完成的。例如，人们热衷于研究使用不同的变化启发的方法来获得优化夹具布局方案，通常需要几何和力学计算的足够多的精度。事实上，计算机支持的智能算法在这项工作上有更好的表现。与此同时，在工件夹具系统中分布多传感网络并使用网上智能控制技术可以适当的调整加工过程中的装夹接触和力来保持一个优化的夹具工件情况。那是过去几年中夹具设计应用的智能技术快速发展的重要原因。此外，近期在一些新知识相关的技术中的成就中，如知识模型化，数据挖掘技术，机器学习等等显示了先进计算机辅助夹具设计的一个更加光明和成功的未来发展。在许多制造公司中，有经验的夹具设计师的技术知识，大量的技术文件
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