- Email: [email protected]
Design for Assembly (DFA) Using Resources of Virtual Reality
Copyright © IFAC Intelligent Manufacturing Systems, Gramado - RS, Brazil, 1998
Design For Assembly (DFA) using resources of Virtual Reality Creusa Sayuri Tahara [email protected]
Eduardo Vila Gon~alves Filho [email protected]
Arthur Jose Vieira Porto [email protected] University of Sao Paulo - USP - Engineering School of Sao Carlos - Department of Mechanical Engineering Av. Dr.Carlos Botelho, 1465 ZIP CODE 13560-250 - Sao Carlos -SP - Brazil Abstract The design for assembly (DFA) supplies information about the efficiency of product design in agreement with the assembly characteristics. We can classify it as an optimisation technique that intends to improve the product design without loss of the quality. In this work, we suggested a study proposal that links the resources of the virtual reality with technique of design for assembly. Copyright © 1998 1FAC
1. Introduction The world market required that the companies restructured their business strategies, and they incorporated that new model into the reality of the company. The factory of the future should think of guaranteeing its business in the internal and external market. All the sections of the company should work in an integrated way, that is to say, from the product design to the production planning, with its private interfaces with the external set. In this environment, the companies should have flexibility in the production form and speed in the liberation of requests, together with the reduction of times of processing for the \vhole company. The information system increasingly the comp'41Y' s integration. Thus, the simultaneous engmeenng will have a mechanism for its effective implementation and the processes can happen in parallel with the product design and the production planning or the manufacturing facilities. The product design, joins a several information, on the layout of its components and it structures geometric since those characteristics will influence the process of assembly of the product directly. Inside of the
structure of the product design, we have tools to compose the component layout and tools for optimisation of the structure of the product and geometry of the components for assembly. So far the moment, little tools computational optimisation (systems CAD) for the assembly process is available, and they already allow the verification of the viability of the assembly and checking of possible collisions. Already for the conventional methods, the tools embrace two categories: evaluation and correction. The evaluation methods include FMEA (Failure Mode and Effects Analysis) and DFA (Design For Assembly), DFM (Design For Manufacturing), among others methods. The method FMEA worries about identifying sources of possible flaws in the product design and correcting them, providing larger reliability to the product. DF A provides a method for a detailed evaluation of the assembly process. Bootbroyd and Dewhurst developed the method DF A with the main purpose of minimising the manipulation cost and junction of the components. The reduction of costs is obtaining with the reduction of the number of components and the warranty that the assembly is possible.
299
The available tools until the moment do not allow an evaluation based on information from CAD to contribute with DF A, but we can already think of tools of virtual reality that to supply information on the assembly of the product. Softwares as W orldToolKit and WorldUp (Sense8i&' Corporation) can be used to develop the of the alteration project, resultant suggestions. ANGSTER (1996) development VEDAM (Virtual a system called Environments for Design And Manufacturing) that has been designed and partially implementated to support virtual design, virtual manufacturing and virtual assembly. VEDAM is aimed at extending the capabilities of existing parametric C.AD/CAM systems. Advantages in the use of the methodology of DF A come from the fact of being a simple, fast method and easily, but as disadvantage does not consider the cost of the piece or the cost of the assembly. The best assembly cannot be the smaller nwnber of pieces. However, associated as other (Design For techniques like , DFM Manufacturing), FMEA, QFD, can obtain a system integrated for the product development that guarantees for whole its phases the best acting in quality terms and cost. In this work, we looked for the contributions of "irtual reality in the process of design for assembly of the product as a tool optimisation. In the section 2, we present the basic concepts and the foundations of the application of the virtual reality to improve the design for assembly. In the section 3, we present a brief conclusion or considerations on the work.
after to reduce the costs. Consequently, assembly design involves decisions that have interactive with the process decisions, generating an appropriate combination to accommodate the advantages and disadvantages of the process. The product development process relates a series of departments for the elaboration of the product. From the phase of the conception until to production, a lot of information is compiled to product conclusion as to defme of the fmal tests and the production line. The co-ordination of this process would run of way to allow the largest possible interaction among the departments. The problems are solved with the smallest time possible, or cost minimising through decrease of number of mistakes in the product design. A serious problem can take to a substantial delay in the product development is the defInition of parts that later become the process of assembly very onerous. For these reasons, considerations on the assembly and on the manufacturability of the product initials of the cycle of product development should be analysed, since 70% of the cost of the fmal product is certain in the project phase. Two basic classes of assembly process are available: executed manually and that executed by mechanism (automated). Both classes divide in subclasses, in agreement with the specifIcations of the method. It is common in the methods of projects for assembly the suggestion of the reduction of the number of components in the product. However, it is no most appropriate strategy, since the times of assembly and the cost are associated to the number of necessary operations for the assembly. The design for manufacturability of a product has as main objective the integration of the activities of the product design with the process planning. The method DFM allows that they are establishes communication entails among all the elements of the production system, facilitating flexibility in to adopt and to modify the design during each apprenticeship of product development. The design for assembly (DFA) is an important element in the defInition of the design for
2. Basic concepts 2. 1 DFA As all good design methodology, in the assembly is important to decide which factors are important for the project analysis establishing priorities and action rules. We can think that whole production design has as main objective to reach the functionality (reliability, quality, innovation, etc.) and soon
300
manufacture, because it simplifies the structure of the product. The method DF A is use to analyse the design, to identify difficulties and to esteem assembly costs. The design characteristics are examines in a systematic way and the efficiency of the design is calculates, allowing a comparison among two projects. The design for assembly acts as a tool that provides a larger involvement between the manufacture area and design engineering and it still provides the documentation of the design process, allowing that can be used in future works.
envelop a person in an interactive computergenerated or computer-mediated virtual environment (WEXELBLAT, 1993). The virtual reality provides a way of the participant to interactive with a simulate environment 3D. The available tools for the development of virtual environments provide the advantage of the incorporation of the user's intuitive knowledge regarding the physical world to manipulate the virtual world. The user enters in the virtual space of the application and he visualises, manipulates and explores the data of the application in real time, using his senses. This application line refers the immersive virtual reality. To support that interaction type, the user uses devices as visualisation helmet and control and gloves. These devices supply to the user the impression of the three-dimensional environment, making possible the exploration and the manipulation of the objects developed in the environment. An important area of the automation of projects that uses resources of virtual reality is the virtual prototyping. Many works have been discussing on the perspectives of the virtual prototipa9ao in the market as well as other forms of application of the virtual reality, as:
2.1 .1 Methodologies for design for assembly The methodologies of DFA can be classified in four basic types, (RED FORD & CHAL, 1994): 1. Based on beginnings and design rules; 2. Based on quantitative evaluation procedures; 3. Based on the approach of knowledge base 4. Based on tools guided for the computer. Those methods look for information on the assembly in two categories: put quantitative and qualitative. Once the method has been defme, the model to evaluate the assembly supplies the following information: • Location and orientation of the components; • Assembly Directions; • Tolerancing • Collision-free assembly! disassembly processes; • Neighbourhoods; • Degree of freedom of connections; • Stability.
• •
•
• 2.2 Virtual reality • We detine virtual reality from much focus, but it may be describe as an interactive interface that allows the use of senses to control and manipulate objects in the artificial world. VR creates artiticial worlds of sensory experience, a simulation of real world that
to design machines with appraised and tested structural properties; to develop a functional and reliable ergonomics, without having to build a model in real scale; to product design that possess design in agreement with the customer's preference, with the possibility of you preview testing; to facilitate remote operations and control of equipment To educate employees in techniques production assaults, mainly with emphasis in guaranteeing the safety in the work.
2.3 Optimisation the design for assembly with resources of virtual reality
301
2. Decrease of Costs: the virtual prototype can reduce the need to do a great number of physical prototypes, this permit a decrease in the time of development and of the work human employee in the project. There are also decrease of the amount of tools and materials used for the making of the physical prototype. The results of the virtual prototype are obtaining more quickly and for this reason, they facilitate the collection of information about the project, before that the costs of the production be fastening. 3. Improvement of the Quality: the verification of different alternatives for a design can be accomplished more quickly and allowing an improvement of the validation of the appropriate solutions that satisfies the parameters specified by the customer, with a smaller cost. The construction of the virtual prototypes facilitates the anticipation of decisions, joining larger quality to the product for the largest refmement of the design. In a general way, the readiness of a larger number of prototypes, ends for supplying a larger involvement of the design team, joining knowledge on the product and facilitating financial decisions, of planning or techniques on the product. In the specific case of the assembly, the prototype will allow the analysis of viability of the design, that is to say, to verify the product can be set up and in that conditions that happens. The techniques of virtual reality would be using in the product virtual prototype construction phase. The virtual model generated that will aid the planner to analyse some assembly characteristics in relation to qualitative and quantitative measures. The model would be using with the aid of gloves, helmets and glasses for control and visualisation. The environment initially could work just with analyses of manual assemblies and later with automated assemblies, since we can also model virtual machines. This design is part of a recent research line in the Engineering School of Sao Carlos, USP, Department of Mechanical Engineering, Laboratory of Simulation, where a virtual lathe was already developed to test an interlocking model (VALERIO NETTO, 1998).
The illustration 1 exhibition the inclusion of the virtual reality to aid the design for assembly. A lot of information are necessary to use this tool since is necessary to transfer all the information of the new design from softwares as CAD, or to use the resources of the own virtual environment. In this environment, they will acquire special characteristics.
Development of the concept for the improved project
Design for Assembly (DF A)
Concept improved of product
Figure 1: Optimisation of the analysis DFA with virtual reality This process requests investment in equipment and specialists for the project development, that mean costs, but many benefits can be resulted: 1. Reduction of Time: the parameter time is an important factors for the industry. The virtual prototype facilitate the execution of more tests and analyses with the product;
302
WEXELBLAT, A., Virtual reality. Application and explorations. Academic Press, Boston, 1993. VALERIO NEITO, A. Proposta de prototipaC;ao do intertravamento de urn tomo CNC usando modelagem em realidade virtual. Dissertation, EESe, USP. Sao Carlos, Brazil. 1998.
The use virtual reality together with the design for assembly can develop ' for construction a system integrated with every company, since this is the tendency of the organisations of the future. 3. Conclusion The use of the methodology of DFA already guarantees a considerable improvement for the cost and design for assembly of a product. When we used it 'together with the resources of virtual reality, we can activate the process of tests of the new design and to verify the new alterations corresponds to the practical expectations. However, this application is still restrict to design for manual assembly and low complexity. The construction of objects in the virtual environment, with all property of real object is not totally trivial and the difficulty increases the measure that we defined more properties or functions for the object. Current of that fact, besides the planner's team, the team for the virtual design should also be qualified and well trained, since the necessary knowledge to work with the models of virtual reality demands experience. The use of the virtual reality, can be to revolutionise the area of product development, today still limited by the resources and the own difficulty of diffusion of those new technologies in the ambient organisational. In this work, we intended to develop a model to incorporate the potentialities of that new tool in the design for the assembly.
4. Bibliographical references ANGSTER, S.R., VENDAM: Virtual environment for Design and Manufacturing, Ph.D. Dissertation, Washington State University, December 1996. KALAWSKY, R.S. The science of virtual reality and \;rtual environments. AddisonWesley, New York, 1993 . REDFORD, A., CHAL, J. Design goes assembly. Principles and practice. McGrawHill, London, 1994.
303
Design For Assembly (DFA) using resources of Virtual Reality Creusa Sayuri Tahara [email protected]
Eduardo Vila Gon~alves Filho [email protected]
Arthur Jose Vieira Porto [email protected] University of Sao Paulo - USP - Engineering School of Sao Carlos - Department of Mechanical Engineering Av. Dr.Carlos Botelho, 1465 ZIP CODE 13560-250 - Sao Carlos -SP - Brazil Abstract The design for assembly (DFA) supplies information about the efficiency of product design in agreement with the assembly characteristics. We can classify it as an optimisation technique that intends to improve the product design without loss of the quality. In this work, we suggested a study proposal that links the resources of the virtual reality with technique of design for assembly. Copyright © 1998 1FAC
1. Introduction The world market required that the companies restructured their business strategies, and they incorporated that new model into the reality of the company. The factory of the future should think of guaranteeing its business in the internal and external market. All the sections of the company should work in an integrated way, that is to say, from the product design to the production planning, with its private interfaces with the external set. In this environment, the companies should have flexibility in the production form and speed in the liberation of requests, together with the reduction of times of processing for the \vhole company. The information system increasingly the comp'41Y' s integration. Thus, the simultaneous engmeenng will have a mechanism for its effective implementation and the processes can happen in parallel with the product design and the production planning or the manufacturing facilities. The product design, joins a several information, on the layout of its components and it structures geometric since those characteristics will influence the process of assembly of the product directly. Inside of the
structure of the product design, we have tools to compose the component layout and tools for optimisation of the structure of the product and geometry of the components for assembly. So far the moment, little tools computational optimisation (systems CAD) for the assembly process is available, and they already allow the verification of the viability of the assembly and checking of possible collisions. Already for the conventional methods, the tools embrace two categories: evaluation and correction. The evaluation methods include FMEA (Failure Mode and Effects Analysis) and DFA (Design For Assembly), DFM (Design For Manufacturing), among others methods. The method FMEA worries about identifying sources of possible flaws in the product design and correcting them, providing larger reliability to the product. DF A provides a method for a detailed evaluation of the assembly process. Bootbroyd and Dewhurst developed the method DF A with the main purpose of minimising the manipulation cost and junction of the components. The reduction of costs is obtaining with the reduction of the number of components and the warranty that the assembly is possible.
299
The available tools until the moment do not allow an evaluation based on information from CAD to contribute with DF A, but we can already think of tools of virtual reality that to supply information on the assembly of the product. Softwares as W orldToolKit and WorldUp (Sense8i&' Corporation) can be used to develop the of the alteration project, resultant suggestions. ANGSTER (1996) development VEDAM (Virtual a system called Environments for Design And Manufacturing) that has been designed and partially implementated to support virtual design, virtual manufacturing and virtual assembly. VEDAM is aimed at extending the capabilities of existing parametric C.AD/CAM systems. Advantages in the use of the methodology of DF A come from the fact of being a simple, fast method and easily, but as disadvantage does not consider the cost of the piece or the cost of the assembly. The best assembly cannot be the smaller nwnber of pieces. However, associated as other (Design For techniques like , DFM Manufacturing), FMEA, QFD, can obtain a system integrated for the product development that guarantees for whole its phases the best acting in quality terms and cost. In this work, we looked for the contributions of "irtual reality in the process of design for assembly of the product as a tool optimisation. In the section 2, we present the basic concepts and the foundations of the application of the virtual reality to improve the design for assembly. In the section 3, we present a brief conclusion or considerations on the work.
after to reduce the costs. Consequently, assembly design involves decisions that have interactive with the process decisions, generating an appropriate combination to accommodate the advantages and disadvantages of the process. The product development process relates a series of departments for the elaboration of the product. From the phase of the conception until to production, a lot of information is compiled to product conclusion as to defme of the fmal tests and the production line. The co-ordination of this process would run of way to allow the largest possible interaction among the departments. The problems are solved with the smallest time possible, or cost minimising through decrease of number of mistakes in the product design. A serious problem can take to a substantial delay in the product development is the defInition of parts that later become the process of assembly very onerous. For these reasons, considerations on the assembly and on the manufacturability of the product initials of the cycle of product development should be analysed, since 70% of the cost of the fmal product is certain in the project phase. Two basic classes of assembly process are available: executed manually and that executed by mechanism (automated). Both classes divide in subclasses, in agreement with the specifIcations of the method. It is common in the methods of projects for assembly the suggestion of the reduction of the number of components in the product. However, it is no most appropriate strategy, since the times of assembly and the cost are associated to the number of necessary operations for the assembly. The design for manufacturability of a product has as main objective the integration of the activities of the product design with the process planning. The method DFM allows that they are establishes communication entails among all the elements of the production system, facilitating flexibility in to adopt and to modify the design during each apprenticeship of product development. The design for assembly (DFA) is an important element in the defInition of the design for
2. Basic concepts 2. 1 DFA As all good design methodology, in the assembly is important to decide which factors are important for the project analysis establishing priorities and action rules. We can think that whole production design has as main objective to reach the functionality (reliability, quality, innovation, etc.) and soon
300
manufacture, because it simplifies the structure of the product. The method DF A is use to analyse the design, to identify difficulties and to esteem assembly costs. The design characteristics are examines in a systematic way and the efficiency of the design is calculates, allowing a comparison among two projects. The design for assembly acts as a tool that provides a larger involvement between the manufacture area and design engineering and it still provides the documentation of the design process, allowing that can be used in future works.
envelop a person in an interactive computergenerated or computer-mediated virtual environment (WEXELBLAT, 1993). The virtual reality provides a way of the participant to interactive with a simulate environment 3D. The available tools for the development of virtual environments provide the advantage of the incorporation of the user's intuitive knowledge regarding the physical world to manipulate the virtual world. The user enters in the virtual space of the application and he visualises, manipulates and explores the data of the application in real time, using his senses. This application line refers the immersive virtual reality. To support that interaction type, the user uses devices as visualisation helmet and control and gloves. These devices supply to the user the impression of the three-dimensional environment, making possible the exploration and the manipulation of the objects developed in the environment. An important area of the automation of projects that uses resources of virtual reality is the virtual prototyping. Many works have been discussing on the perspectives of the virtual prototipa9ao in the market as well as other forms of application of the virtual reality, as:
2.1 .1 Methodologies for design for assembly The methodologies of DFA can be classified in four basic types, (RED FORD & CHAL, 1994): 1. Based on beginnings and design rules; 2. Based on quantitative evaluation procedures; 3. Based on the approach of knowledge base 4. Based on tools guided for the computer. Those methods look for information on the assembly in two categories: put quantitative and qualitative. Once the method has been defme, the model to evaluate the assembly supplies the following information: • Location and orientation of the components; • Assembly Directions; • Tolerancing • Collision-free assembly! disassembly processes; • Neighbourhoods; • Degree of freedom of connections; • Stability.
• •
•
• 2.2 Virtual reality • We detine virtual reality from much focus, but it may be describe as an interactive interface that allows the use of senses to control and manipulate objects in the artificial world. VR creates artiticial worlds of sensory experience, a simulation of real world that
to design machines with appraised and tested structural properties; to develop a functional and reliable ergonomics, without having to build a model in real scale; to product design that possess design in agreement with the customer's preference, with the possibility of you preview testing; to facilitate remote operations and control of equipment To educate employees in techniques production assaults, mainly with emphasis in guaranteeing the safety in the work.
2.3 Optimisation the design for assembly with resources of virtual reality
301
2. Decrease of Costs: the virtual prototype can reduce the need to do a great number of physical prototypes, this permit a decrease in the time of development and of the work human employee in the project. There are also decrease of the amount of tools and materials used for the making of the physical prototype. The results of the virtual prototype are obtaining more quickly and for this reason, they facilitate the collection of information about the project, before that the costs of the production be fastening. 3. Improvement of the Quality: the verification of different alternatives for a design can be accomplished more quickly and allowing an improvement of the validation of the appropriate solutions that satisfies the parameters specified by the customer, with a smaller cost. The construction of the virtual prototypes facilitates the anticipation of decisions, joining larger quality to the product for the largest refmement of the design. In a general way, the readiness of a larger number of prototypes, ends for supplying a larger involvement of the design team, joining knowledge on the product and facilitating financial decisions, of planning or techniques on the product. In the specific case of the assembly, the prototype will allow the analysis of viability of the design, that is to say, to verify the product can be set up and in that conditions that happens. The techniques of virtual reality would be using in the product virtual prototype construction phase. The virtual model generated that will aid the planner to analyse some assembly characteristics in relation to qualitative and quantitative measures. The model would be using with the aid of gloves, helmets and glasses for control and visualisation. The environment initially could work just with analyses of manual assemblies and later with automated assemblies, since we can also model virtual machines. This design is part of a recent research line in the Engineering School of Sao Carlos, USP, Department of Mechanical Engineering, Laboratory of Simulation, where a virtual lathe was already developed to test an interlocking model (VALERIO NETTO, 1998).
The illustration 1 exhibition the inclusion of the virtual reality to aid the design for assembly. A lot of information are necessary to use this tool since is necessary to transfer all the information of the new design from softwares as CAD, or to use the resources of the own virtual environment. In this environment, they will acquire special characteristics.
Development of the concept for the improved project
Design for Assembly (DF A)
Concept improved of product
Figure 1: Optimisation of the analysis DFA with virtual reality This process requests investment in equipment and specialists for the project development, that mean costs, but many benefits can be resulted: 1. Reduction of Time: the parameter time is an important factors for the industry. The virtual prototype facilitate the execution of more tests and analyses with the product;
302
WEXELBLAT, A., Virtual reality. Application and explorations. Academic Press, Boston, 1993. VALERIO NEITO, A. Proposta de prototipaC;ao do intertravamento de urn tomo CNC usando modelagem em realidade virtual. Dissertation, EESe, USP. Sao Carlos, Brazil. 1998.
The use virtual reality together with the design for assembly can develop ' for construction a system integrated with every company, since this is the tendency of the organisations of the future. 3. Conclusion The use of the methodology of DFA already guarantees a considerable improvement for the cost and design for assembly of a product. When we used it 'together with the resources of virtual reality, we can activate the process of tests of the new design and to verify the new alterations corresponds to the practical expectations. However, this application is still restrict to design for manual assembly and low complexity. The construction of objects in the virtual environment, with all property of real object is not totally trivial and the difficulty increases the measure that we defined more properties or functions for the object. Current of that fact, besides the planner's team, the team for the virtual design should also be qualified and well trained, since the necessary knowledge to work with the models of virtual reality demands experience. The use of the virtual reality, can be to revolutionise the area of product development, today still limited by the resources and the own difficulty of diffusion of those new technologies in the ambient organisational. In this work, we intended to develop a model to incorporate the potentialities of that new tool in the design for the assembly.
4. Bibliographical references ANGSTER, S.R., VENDAM: Virtual environment for Design and Manufacturing, Ph.D. Dissertation, Washington State University, December 1996. KALAWSKY, R.S. The science of virtual reality and \;rtual environments. AddisonWesley, New York, 1993 . REDFORD, A., CHAL, J. Design goes assembly. Principles and practice. McGrawHill, London, 1994.
303