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The Digital Factory between vision and reality
Computers in Industry 56 (2005) 325–333 www.elsevier.com/locate/compind
The Digital Factory between vision and reality U. Bracht *, T. Masurat Institut fu¨r Maschinelle Anlagentechnik und Betriebsfestigkeit (IMAB), at the Technical University of Clausthal, Bereich, Anlagenprojektierung und Materialflusslogistik, Leibnizstraße 32, D-38678 Clausthal-Zellerfeld, Germany Received 1 February 2004; received in revised form 18 November 2004; accepted 31 January 2005 Available online 9 April 2005
Abstract The comprehensive approach to the digital factory has become a subject of paramount importance to all major automotive companies, and the chances offered by it are numerous. However, extensive preliminary work is still necessary and thus requires a tremendous effort, especially for small and medium-sized enterprises (SME) which must be integrated as suppliers of components. The purposes of the present article are to describe, in a general way, how the vision of the digital factory can be implemented in reality and to outline the problems, which must still be expected in the further course of the endeavour. In addition, the status of research relating to the digital factory at IMAB, Anlagenprojektierung und Materialflusslogistik at the Technical University of Clausthal, and the fields of future developmental activity are illustrated through the use of an example. # 2005 Elsevier B.V. All rights reserved. Keywords: Digital factory; Simulation; Factory planning
1. Introduction An old proverb, to err is human, provides the best explanation for the endeavour to develop a digital factory. The entire life cycle of products and production plants requires planning efforts from the very beginning, and this planning work must be performed by humans. In conclusion, this implies that planning is always subject to error and that the failure to recognise the errors in due time results in * Corresponding author. Tel.: +49 5323 72 2201; fax: +49 5323 72 3516. E-mail address: [email protected] (U. Bracht). URL: http://www.imab.tu-clausthal.de
considerable problems during the respective implementation phase. The objective of the digital factory is derived from this simple fact. The object is to secure products and processes during an early phase of development and also to accompany the evolution of products and production with the use of digital models. Besides that, the extension of the Digital Factory towards internal and external logistics and business processes should enhance the networking and the overall view of the cooperating enterprises. For SME’s it is especially important in the long term to integrate the fundamental idea of the digital factory into the supply chain to gain competitive advantages. Through simulation of various scenarios it should be possible for these
0166-3615/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.compind.2005.01.008
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enterprises to dimension storage and distribution concepts and to derive new organizational structures. This visionary approach towards the digital factory could be described as a ‘digital enterprise’. Even if a common understanding prevails in and among the companies in setting objectives for the digital factory, the definitions of the concept and the emphasis in the course of developmental activities will still differ. The fact is that the implementation of the digital factory will result in enormous savings in time and costs. However, the efforts necessary for implementation have in part been underestimated and are still underestimated. Only a few decades ago, computers were first introduced into industrial production. More and more partial aspects of planning and development work were supported by software tools specifically designed for particular applications. The first savings in time and costs were achieved, and simulation techniques began to prove their worth as a useful instrument for solving complex, dynamic problems. Rapid, continuing progress in technology and the associated increase in the efficiency of computer systems stimulated the idea of combining and concentrating software solutions, with their predominantly insular character, to form large networks and of creating a continuous chain, all the way from planning to production. The objectives of this concept, designated as ‘computer-integrated manufacturing’ (CIM), were to maintain a continuous flow of information and to interconnect all associated factory departments by means of an interdepartmental information system for electronic data processing [4]. The intention was to achieve the highest possible level of integration for individual computer-aided subsystems in the factory organization. Thus, an all-encompassing solution was envisaged, from the computer-aided functions of designing (CAD), over operations planning (CAP), manufacturing (CAM), and quality assurance (CAQ), all the way to automated production. Nowadays, this vision is regarded as a near-failure since the interface problems between the various software tools and the different programming languages for system control have proved to be an insurmountable barrier. Nevertheless, the basic conclusions derived from CIM development have resulted in substantial progress, especially in the fields of production planning and control. Hence, the real approach to the CIM concept can be viewed as a major success, and the CIM pioneers
can also be regarded as having paved the way for the digital factory. Some of the problems posed by the digital factory are similar to those presented by the CIM concept. For this reason, a few questions are important for the further development of the digital factory. What is the current developmental status of the digital factory? Which targets have been set? What does the digital factory mean to small and medium-sized enterprises? How much digital factory is actually required by various companies? The answers to these questions are decisive for the success or failure of the digital factory and are by no means trivial. The object of the present publication is to explain a few aspects of these questions, to stimulate discussions for obtaining a better understanding of the problems posed by the digital factory, and thus to derive new approaches to a realistic implementation.
2. The vision of the digital factory The vision of the digital factory could be as follows: All computer-aided tools necessary for the planning of new products and production plants as well as for the operation of the factories are networked through a central database. New structures in the product development and manufacturing processes ensure that the requirement for simultaneous engineering is satisfied. Thus, the entire factory is simulated on the computer as a continuous and consistent virtual-reality model (VR model), which can then be applied, without interruption, all the way from the product idea to the final dismantling of the production plants and buildings. An automatic data management system ensures that changes result in the updating of the data in all company departments concerned after their release. Access to all necessary information is possible on a permanent basis. The data can be exchanged between systems without any conversion whatsoever, since the open structure of the software tools allows the docking of new companyspecific modules and new tools. Efficient VR systems permit high-end visualization of all situations at any time; hence, interdisciplinary cooperation among various experts is possible all the way from the product design to the inspection of the new or modified factory.
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The simulation techniques have been continuously improved. As a result, the phases of physical product testing can also be minimized; consequently, the number of product prototypes also decreases considerably. For production plants, the try-out is performed entirely with the aid of VR-supported simulations; hence, there is no need to construct physical pilot plants. The construction of new production plants can be permanently monitored by means of laser scanning. The VR models generated from the scans of the halls and plants can be compared with the planning models; errors in implementation can thus be detected immediately. Remedial measures or planning adaptations can therefore be implemented directly. Pilot production is no longer necessary, since a virtual confidence test is also performed here. Consequently, the start-up curves for production are also very steep, since only a few errors still occur in the systems or their logistic interconnections. During the production phase, material-flow simulators monitor and control the factory operation and provide support for job scheduling. If major malfunctions occur, emergency scenarios are quickly generated and simulated; thus, clear-cut procedural instructions can be provided for an efficient reaction. Conversion and optimizing processes can likewise be simulated
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with the computer model; hence, optimal conditions can also be created for reorganization, conversion phases, and start of operation. Changes in the layouts result in an automatic adaptation of the associated material-flow models and can be immediately compared with simulation results and appraised correspondingly. With an extension of the simulation functions, permanent cost monitoring is possible. In this context, the digital factory also functions as a tool for controlling and for more extensive economic considerations. During the developmental phases, the digital factory thus operates virtually in the same way as the real factory should function after implementation. Furthermore, it is permanently coupled with the actual production process after the realization of the plans and can thus be employed for monitoring, controlling, and constantly improving this process. In Fig. 1, the vision of the digital factory is represented graphically.
3. Problems along the way to the digital factory An example from the history of industrial development during the past decades very clearly illustrates the far-reaching consequences, which can result from
Fig. 1. The vision of the digital factory.
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the increased application of computer-aided tools. The introduction of ‘computer-aided design’ (CAD) tools can be viewed as a kind of miniature revolution. Because of general scepticism and inadequate user orientation of some CAD programs, the complete implementation of such tools in industry as a whole required decades. Initially, it was simply not possible to substitute such tools for the knowledge and skill of engineering draughtsmen. A well-versed draughtsman was capable of achieving a usable result on his drawing board considerably faster than was possible with the use of a computer. Furthermore, the efficiency of computers and plotters was, in many cases, still not sufficient for attaining the required quality. Nevertheless, the advantages resulting from the considerable simplifications in the management of change and from the performance of time-consuming routine activities finally paved the way for widespread acceptance of the tools. To a steadily increasing extent, the preparation of detailed drawings and plans was assumed by the designers themselves; this development resulted in decisive structural changes in some functional departments in the companies, as well as in changes
in the methods of design and construction. The distribution of work over various stages of planning development thus became possible, too. However, disadvantages also resulted from the introduction of CAD tools. Over the years, many engineering draughtsmen had accumulated highly specialized know-how in the course of their activities. Practicable detail solutions were often the work of draughtsmen, and the avoidance of certain errors was rendered possible by their work. As the drafting departments were phased out, the loss of valuable know-how was thus accepted as an inevitable consequence. From this example, it is evident that the introduction of a new system decisively affects structures and procedures. In this context, the implementation of the digital factory can be expected to cause considerable changes in previous production processes. Computeraided monitoring and control of the factory operation will also be affected. Essentially, four major problem fields result from the implementation of the digital factory. These problem fields are considered in more detail in the following and are illustrated in Fig. 2.
Fig. 2. Problem fields associated with the digital factory.
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3.1. Networking The fundamental requirement of comprehensive networking among all software tools involved in the production processes and in factory operation is hindered by their predominantly proprietary design. As is the case of the CIM concept, native formats give rise to a multiplicity of interfaces, which render cooperation among the various tools difficult or even impossible. The expenditure for the conversion of the required data is still considered to be too high at present and is therefore often regarded as unacceptable. 3.2. Version, knowledge, and data management As the efficiency of the software and hardware increases, the working habits of the user also change. Especially the increase in memory capacity results in immense volumes of stored data. Hence, the memory requirement has increased dramatically during recent years, and a veritable flood of data must therefore be managed. This demand is in part due to the steadily increasing use of new tools in product development, factory planning, and factory operation. On the other hand, however, the modern user is intensively concerned with data back-up. Consequently, a large number of data-record versions are stored in the course of a project, in order to ensure the continued availability of the data in the event that they are needed again. Furthermore, identical data are often stored redundantly on various servers and systems. A further challenge results from the necessity of managing and securing a company’s specific knowhow in a manner appropriate for preventing loss. Workflows and experience must be recorded in such a way that they are available and useful to all employees. Obsolete data-record versions and insufficient information flows constitute sources of error which should not be underestimated. Since the development and planning process is characterized by a multiplicity of iteration loops, adaptations are absolutely necessary in all departments of the company and in all phases of project execution. Particularly in the digital factory, special demands are imposed on the maintenance of data and the management of versions in this respect. It must be ensured that up-to-date, subject-specific,
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relevant data are continuously and immediately available to all those concerned, especially in the event of changes. The large quantities of data and the equally large number of different data formats constitute one of the main problems associated with the digital factory. 3.3. Processes and structures It is assumed that the existing structural organization of company departments will change as the digital factory becomes more widespread. Fewer physical prototypes will be required, and various specialized departments will be combined to an increasing extent. A redistribution of functions and responsibilities will be necessary for creating integrated and efficient design processes. Moreover, the concerned personnel will be confronted with new planning procedures. The conventional phase models of project work must likewise be eliminated, since a clear-cut delimitation of individual steps no longer makes sense if the potential of the digital factory is to be fully utilized. In this context, simultaneous engineering will become a necessity, and its possibilities will be utilized to the limits. At present, only speculation is possible in connection with the actual structures of the hierarchical and sequential organizations within companies in the future. In any event, it is certain that decisive changes will occur. As already pointed out in a publication [3], the essential supporting pillars for the digital factory may already be standing by 2005. However, the conversion process itself will require much more time, more than was required for the introduction of CAD systems. Furthermore, considerable research and innovative solutions will be necessary. 3.4. Commitment At present, the digital factory is still a project for large-scale enterprises, especially for OEM’s in the automotive industry. Large amounts of capital are being made available for making the vision come true. However, questions concerning the necessary level of implementation are also receiving increased attention. Conversion of the incurred costs to yield a financial return flow is not yet possible. Of course, many of the software tools necessary for processing individual
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partial aspects of product and production development are already available and have also been tried and proved in applications. However, the available resources are not yet sufficient to allow for a rapid and useful application of these tools, especially in small and medium-sized enterprises. Consequently, not only internal structures are subject to change; in particular, cooperation among companies must also be adapted accordingly. This matter is currently being considered, too, and the objective is to achieve continuity at least up to the 2nd tier suppliers. In the course of these deliberations, however, one question is seldom considered: are the SME, who are very likely to be among the 1st or 2nd tier suppliers, really capable of adequately implementing the digital factory? These smaller companies usually do not have large planning departments of their own for dealing with production requirements, and they usually cannot afford the corresponding software tools. Consequently, it will be difficult for them to utilize the potential offered by the digital factory [1]. For many small companies, investments of this kind are hardly feasible, since they are not economically justifiable as long as the price of the necessary software remains so high, and current expenses can hardly be borne by small companies. Initial approaches toward possible solutions have already been attempted [5], but have not yet found widespread acceptance. Major reasons for this reluctance certainly include the lack of information and the absence of appropriate structures on the part of the KMU. Nevertheless, the digital factory approach is not merely an inevitable necessity; it also offers a chance for some medium-sized suppliers. In this case, too, considerable potential savings could be achieved by implementing the appropriate structural measures and with support from external service companies.
4. The reality of the digital factory The vision and the associated problems have been described. However, what is the current developmental status of the digital factory? In this context, it should first be mentioned that the level of implementation already achieved by some companies cannot be determined exactly. Hence, the following discussion should be regarded as a summary of the
authors’ experience and an analysis of the published information. At least one thing is certain, however, large investments in the digital factory have already been realized, especially in the automotive industry and by many 1st tier suppliers. Furthermore, it cannot be denied that companies have already achieved success in certain partial fields and in pilot projects. An example is the nearly uninterrupted application of various planning tools by automobile manufacturers in vehicle body construction. Product data integration, robot simulation, and the associated off-line programming have already become established there. Two large software suppliers currently constitute the supporting columns of the digital factory. As indicated by current knowledge, however, it is not necessarily probable that a software platform can cover all facets of the digital factory. Previous cooperation among the suppliers of tools, which may be applicable within the scope of the digital factory is by no means adequate, and the demands imposed on a central, standardized data management system can hardly be satisfied at present. For small and medium-sized enterprises, many of the tools are still much too expensive, or cost recovery from applications is not possible. Nonetheless, some of these companies are already requesting delivery of certain proofs or data in digital form to match their customers’ respective digital factory. An increasing number of system suppliers also offer services in conjunction with the digital factory. Since the various computer-aided tools in the developmental, design, and planning stages are so numerous, however, these suppliers must also come to grips with a multiplicity of interfaces. Furthermore, they are forced to keep almost all software tools available, in order to be able to satisfy the needs of as many customers as possible. This requirement also poses the question of economy and will further aggravate competition. Hence, it must be concluded that inherently necessary, standardized networking of the tools is hardly feasible, since the structures of many tools do not allow for docking with other modules or applications, or at least render an adaptation difficult. Furthermore, the problems of version and data management have not yet been solved. These factors could further increase the multiplicity of insular
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software solutions in the various company departments. Regardless of which decision is reached in favour of a particular general supplier of software for the digital factory, certain advantages as well as disadvantages will always result from the choice. For instance, it cannot always be assumed that all problems associated with the interfaces between supplier-specific software tools have been solved. Since the existing company structures tend to reflect conventional patterns of thought and work, and since the new process and method orientation is not yet practiced in a comprehensive manner, only a limited portion of the potential savings can be achieved with the insular IT solutions. The real possibilities offered by the digital factory are accessible only through an appropriate networking of all tools in combination with a restructuring of the processes and hierarchical organization of the companies. Reconsideration and redistribution of competencies and responsibilities will also be necessary. Furthermore, a considerable untapped potential is still available from the computer tools themselves. The user interfaces of the tools and the user guidance must become considerably more intuitive. After all, the user’s creativity should not be subordinated to the formalities of the tools; in particular, ideas must be implemented and tested quickly and simply with the use of the computer.
5. Small steps toward success—an example of research at IMAB The following project description should provide insight into the fundamental research in progress at IMAB on the subject of the digital factory. In order to allow for interdisciplinary discussions among the project participants from different fields of specialization, the concept of the virtual communication platform is frequently employed in conjunction with the digital factory. Above all, this term designates a virtual-reality-oriented tool, which is employed to allow for a more effective visualization of various planning results. For instance, the results of the design process can thus be considered together with the factory planners’ data and the logistician’s concepts. Joint planning meetings before and during VR projection thus allow for more efficient mutual
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agreement on the work and support the continuing development activities on the basis of results which are already available. An example is the so-called digital mock-up, which permits the virtual assembly of individual components and subassemblies. A further field of research is the networking of results from material-flow simulation and layout planning. In this context, the functions of a material-flow simulator have been integrated into a VR model developed at IMAB [2]. 5.1. Objectives For the new manufacturing technology based on high-frequency welding in the sheet-metal industry, a general survey already indicates the possible range of series applications in future production, even at a very early stage of development. The short process time for the welding of sheet-metal profile components by this method had suggested the possibility of applying this technique to the manufacture of modular-design components. The associated requirements on the structure of a production plant should be investigated, especially from a logistics point of view at this early stage of process development. 5.2. Procedure In order to find a realistic approach to the problems posed by the new manufacturing process, a fictitious subassembly was designed; this subassembly consisted of three individual components and could be produced in 10 different versions by high-frequency welding. From the structure of the subassembly, the necessary manufacturing facilities were then derived and combined to form a production cell in a preliminary draught. For this purpose, two of the three components had to be manufactured directly in the production cell. For one of these two components, five versions of different shape and material were envisaged. Since a metal-shaping press was to be used for its manufacture, a component buffer had to be included in the system to ensure continuity of supply for production. In Fig. 3, the virtual prototype for the process is illustrated for high-frequency welding. On the basis of the preliminary layout draught for the production cell, the construction of a model for material-flow simulation was attempted, in order to
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Fig. 3. Illustration of the virtual prototype for a process involving high-frequency welding.
test the functioning and efficiency of the system. Upon parameterization of the simulation model, however, an exact determination of the times – almost by memory – proved to be impossible for most of the manipulation and clamping operations as well as for the entire process sequence in the high-frequency welding facility. For this reason, and also in view of the technical possibilities offered by the VR laboratory at IMAB, it was decided to construct a VR model. The purpose of this model was to visualize the kinematics of the welding facility as well as all operations, in order to allow conclusions to be reached regarding the actual process and operation times. From the basic design and conception of the welding facility, an animated VR model of the production cell was constructed within a period of 5 months. For this purpose, the system layout was structured and further developed by an interdisciplinary project team during several work sessions in the VR laboratory. The discussions among the specialists were supported in a decisive way by the three-dimensional models and the stereoscopic, large-screen projection; as a result, the virtual reality assumed the function of a communica-
tion platform. After completion of all work for the modelling of the 3D layout, the idea of integrating the functionalities necessary for the material-flow simulation into the VR model was considered. The model was adapted correspondingly during the following 4 months. For instance, all machines were provided with programs, which allowed a parameterization of perturbation functions and the associated distributions by means of input masks, as is the case with commercially available material-flow simulators. Moreover, an additional function, which allows for intervention in the distribution of the versions to be produced was included; by means of this function, the behaviour of the system under modified boundary conditions can be analyzed. Provision was also made for free parameterization of the buffer inventory. As soon as the buffer inventory falls below a specified minimum, the manufacturing process is initiated for the corresponding version of component 3. The VR model thus constructed is designated as a virtual prototype for a process and combines the functions of a simulator with the possibilities of 3D visualization.
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5.3. Conclusions resulting from the research project on the digital factory On the basis of the approach described here, and with the virtual prototype for the process as a model example, important conclusions have been reached for the implementation of preliminary production plants with new manufacturing technologies. In this manner, a possible structure for future production by high-frequency welding has been validated as a basic concept. The results of this and similar approaches suggest that considerable progress has already been achieved on the way toward the digital factory. However, the question of the cost-to-benefit ratio is still open.
6. Conclusions It can be concluded that the vision and progressing realization of the digital factory include the essential formulation and potential solution of almost all problems posed by future planning methods and production. Whoever wants to face the brutal global competition must decrease the time required for the realization of products as well as production by orders of magnitude and simultaneously improve the quality. For this purpose, the digital factory is an absolute prerequisite. However, many considerations on the subject of the digital factory suggest that no single company alone will be capable of totally meeting this challenge. For this purpose, extensive cooperation among numerous companies and institutions will be necessary. The objective of acquiring and maintaining competitive advantages single-handedly entails the risk of becoming totally isolated, since too many company-specific software solutions must be developed. The care of such software must also be specific. In the long term, the use of company-specific software will decisively aggravate the difficulties in coupling with development partners, suppliers, and service companies. As a result, only partial success can be expected with such an approach.
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In order to avoid failure with the vision of the digital factory in the short term, an unambiguous orientation of the results is necessary. Obvious projects and objectives must be approached directly and successfully executed in a step-by-step manner. In all of these endeavours, attention must be focused on the prime requirement of maintaining and ensuring the viability of the company in the future.
References [1] U. Bracht, T. Masurat, The forgotten factories, wt-online 4 (2002) 154–158. [2] U. Bracht, T. Masurat, Integration of virtual reality and material flow simulation for digital process specimen – mind games in logistic and production for the digital factory, wt-online 4 (2003) 249–253. [3] E. Schiller, W.P. Seuffert, Bis 2005 realisiert, Automobil-Produktion. (2002) 20–30. [4] Spur G. Fabrikbetrieb. Mu¨ nchen: Hanser; 1994. [5] E. Westka¨ mper, S. Bierschenk, T. Kuhlmann, Digital manufacturing – only for large scale enterprises? wt-online 1/2 (2003) 22–26. Professor Uwe Bracht, born in 1949, studied mechanical engineering at Hannover University. He is director of the Institute for Plant Engineering and Fatigue Analysis (Clausthal Technical University) and founding member of the VDA research group ‘‘Computer-Aided Factory Planning’’. Since 2002 he is heading the VDI expert committee ‘‘Digital Factory’’. His publication list contains more than 50 papers dealing with the improvement of factory planning and organization processes. Thomas Masurat, born in 1967, studied mechanical engineering at Clausthal Technical University, focussing on production technologies. Since 2000 he is scientific assistant at the Institute for Plant Engineering and Fatigue Analysis; mainly dealing with facility planning and logistics tasks.
The Digital Factory between vision and reality U. Bracht *, T. Masurat Institut fu¨r Maschinelle Anlagentechnik und Betriebsfestigkeit (IMAB), at the Technical University of Clausthal, Bereich, Anlagenprojektierung und Materialflusslogistik, Leibnizstraße 32, D-38678 Clausthal-Zellerfeld, Germany Received 1 February 2004; received in revised form 18 November 2004; accepted 31 January 2005 Available online 9 April 2005
Abstract The comprehensive approach to the digital factory has become a subject of paramount importance to all major automotive companies, and the chances offered by it are numerous. However, extensive preliminary work is still necessary and thus requires a tremendous effort, especially for small and medium-sized enterprises (SME) which must be integrated as suppliers of components. The purposes of the present article are to describe, in a general way, how the vision of the digital factory can be implemented in reality and to outline the problems, which must still be expected in the further course of the endeavour. In addition, the status of research relating to the digital factory at IMAB, Anlagenprojektierung und Materialflusslogistik at the Technical University of Clausthal, and the fields of future developmental activity are illustrated through the use of an example. # 2005 Elsevier B.V. All rights reserved. Keywords: Digital factory; Simulation; Factory planning
1. Introduction An old proverb, to err is human, provides the best explanation for the endeavour to develop a digital factory. The entire life cycle of products and production plants requires planning efforts from the very beginning, and this planning work must be performed by humans. In conclusion, this implies that planning is always subject to error and that the failure to recognise the errors in due time results in * Corresponding author. Tel.: +49 5323 72 2201; fax: +49 5323 72 3516. E-mail address: [email protected] (U. Bracht). URL: http://www.imab.tu-clausthal.de
considerable problems during the respective implementation phase. The objective of the digital factory is derived from this simple fact. The object is to secure products and processes during an early phase of development and also to accompany the evolution of products and production with the use of digital models. Besides that, the extension of the Digital Factory towards internal and external logistics and business processes should enhance the networking and the overall view of the cooperating enterprises. For SME’s it is especially important in the long term to integrate the fundamental idea of the digital factory into the supply chain to gain competitive advantages. Through simulation of various scenarios it should be possible for these
0166-3615/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.compind.2005.01.008
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enterprises to dimension storage and distribution concepts and to derive new organizational structures. This visionary approach towards the digital factory could be described as a ‘digital enterprise’. Even if a common understanding prevails in and among the companies in setting objectives for the digital factory, the definitions of the concept and the emphasis in the course of developmental activities will still differ. The fact is that the implementation of the digital factory will result in enormous savings in time and costs. However, the efforts necessary for implementation have in part been underestimated and are still underestimated. Only a few decades ago, computers were first introduced into industrial production. More and more partial aspects of planning and development work were supported by software tools specifically designed for particular applications. The first savings in time and costs were achieved, and simulation techniques began to prove their worth as a useful instrument for solving complex, dynamic problems. Rapid, continuing progress in technology and the associated increase in the efficiency of computer systems stimulated the idea of combining and concentrating software solutions, with their predominantly insular character, to form large networks and of creating a continuous chain, all the way from planning to production. The objectives of this concept, designated as ‘computer-integrated manufacturing’ (CIM), were to maintain a continuous flow of information and to interconnect all associated factory departments by means of an interdepartmental information system for electronic data processing [4]. The intention was to achieve the highest possible level of integration for individual computer-aided subsystems in the factory organization. Thus, an all-encompassing solution was envisaged, from the computer-aided functions of designing (CAD), over operations planning (CAP), manufacturing (CAM), and quality assurance (CAQ), all the way to automated production. Nowadays, this vision is regarded as a near-failure since the interface problems between the various software tools and the different programming languages for system control have proved to be an insurmountable barrier. Nevertheless, the basic conclusions derived from CIM development have resulted in substantial progress, especially in the fields of production planning and control. Hence, the real approach to the CIM concept can be viewed as a major success, and the CIM pioneers
can also be regarded as having paved the way for the digital factory. Some of the problems posed by the digital factory are similar to those presented by the CIM concept. For this reason, a few questions are important for the further development of the digital factory. What is the current developmental status of the digital factory? Which targets have been set? What does the digital factory mean to small and medium-sized enterprises? How much digital factory is actually required by various companies? The answers to these questions are decisive for the success or failure of the digital factory and are by no means trivial. The object of the present publication is to explain a few aspects of these questions, to stimulate discussions for obtaining a better understanding of the problems posed by the digital factory, and thus to derive new approaches to a realistic implementation.
2. The vision of the digital factory The vision of the digital factory could be as follows: All computer-aided tools necessary for the planning of new products and production plants as well as for the operation of the factories are networked through a central database. New structures in the product development and manufacturing processes ensure that the requirement for simultaneous engineering is satisfied. Thus, the entire factory is simulated on the computer as a continuous and consistent virtual-reality model (VR model), which can then be applied, without interruption, all the way from the product idea to the final dismantling of the production plants and buildings. An automatic data management system ensures that changes result in the updating of the data in all company departments concerned after their release. Access to all necessary information is possible on a permanent basis. The data can be exchanged between systems without any conversion whatsoever, since the open structure of the software tools allows the docking of new companyspecific modules and new tools. Efficient VR systems permit high-end visualization of all situations at any time; hence, interdisciplinary cooperation among various experts is possible all the way from the product design to the inspection of the new or modified factory.
U. Bracht, T. Masurat / Computers in Industry 56 (2005) 325–333
The simulation techniques have been continuously improved. As a result, the phases of physical product testing can also be minimized; consequently, the number of product prototypes also decreases considerably. For production plants, the try-out is performed entirely with the aid of VR-supported simulations; hence, there is no need to construct physical pilot plants. The construction of new production plants can be permanently monitored by means of laser scanning. The VR models generated from the scans of the halls and plants can be compared with the planning models; errors in implementation can thus be detected immediately. Remedial measures or planning adaptations can therefore be implemented directly. Pilot production is no longer necessary, since a virtual confidence test is also performed here. Consequently, the start-up curves for production are also very steep, since only a few errors still occur in the systems or their logistic interconnections. During the production phase, material-flow simulators monitor and control the factory operation and provide support for job scheduling. If major malfunctions occur, emergency scenarios are quickly generated and simulated; thus, clear-cut procedural instructions can be provided for an efficient reaction. Conversion and optimizing processes can likewise be simulated
327
with the computer model; hence, optimal conditions can also be created for reorganization, conversion phases, and start of operation. Changes in the layouts result in an automatic adaptation of the associated material-flow models and can be immediately compared with simulation results and appraised correspondingly. With an extension of the simulation functions, permanent cost monitoring is possible. In this context, the digital factory also functions as a tool for controlling and for more extensive economic considerations. During the developmental phases, the digital factory thus operates virtually in the same way as the real factory should function after implementation. Furthermore, it is permanently coupled with the actual production process after the realization of the plans and can thus be employed for monitoring, controlling, and constantly improving this process. In Fig. 1, the vision of the digital factory is represented graphically.
3. Problems along the way to the digital factory An example from the history of industrial development during the past decades very clearly illustrates the far-reaching consequences, which can result from
Fig. 1. The vision of the digital factory.
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the increased application of computer-aided tools. The introduction of ‘computer-aided design’ (CAD) tools can be viewed as a kind of miniature revolution. Because of general scepticism and inadequate user orientation of some CAD programs, the complete implementation of such tools in industry as a whole required decades. Initially, it was simply not possible to substitute such tools for the knowledge and skill of engineering draughtsmen. A well-versed draughtsman was capable of achieving a usable result on his drawing board considerably faster than was possible with the use of a computer. Furthermore, the efficiency of computers and plotters was, in many cases, still not sufficient for attaining the required quality. Nevertheless, the advantages resulting from the considerable simplifications in the management of change and from the performance of time-consuming routine activities finally paved the way for widespread acceptance of the tools. To a steadily increasing extent, the preparation of detailed drawings and plans was assumed by the designers themselves; this development resulted in decisive structural changes in some functional departments in the companies, as well as in changes
in the methods of design and construction. The distribution of work over various stages of planning development thus became possible, too. However, disadvantages also resulted from the introduction of CAD tools. Over the years, many engineering draughtsmen had accumulated highly specialized know-how in the course of their activities. Practicable detail solutions were often the work of draughtsmen, and the avoidance of certain errors was rendered possible by their work. As the drafting departments were phased out, the loss of valuable know-how was thus accepted as an inevitable consequence. From this example, it is evident that the introduction of a new system decisively affects structures and procedures. In this context, the implementation of the digital factory can be expected to cause considerable changes in previous production processes. Computeraided monitoring and control of the factory operation will also be affected. Essentially, four major problem fields result from the implementation of the digital factory. These problem fields are considered in more detail in the following and are illustrated in Fig. 2.
Fig. 2. Problem fields associated with the digital factory.
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3.1. Networking The fundamental requirement of comprehensive networking among all software tools involved in the production processes and in factory operation is hindered by their predominantly proprietary design. As is the case of the CIM concept, native formats give rise to a multiplicity of interfaces, which render cooperation among the various tools difficult or even impossible. The expenditure for the conversion of the required data is still considered to be too high at present and is therefore often regarded as unacceptable. 3.2. Version, knowledge, and data management As the efficiency of the software and hardware increases, the working habits of the user also change. Especially the increase in memory capacity results in immense volumes of stored data. Hence, the memory requirement has increased dramatically during recent years, and a veritable flood of data must therefore be managed. This demand is in part due to the steadily increasing use of new tools in product development, factory planning, and factory operation. On the other hand, however, the modern user is intensively concerned with data back-up. Consequently, a large number of data-record versions are stored in the course of a project, in order to ensure the continued availability of the data in the event that they are needed again. Furthermore, identical data are often stored redundantly on various servers and systems. A further challenge results from the necessity of managing and securing a company’s specific knowhow in a manner appropriate for preventing loss. Workflows and experience must be recorded in such a way that they are available and useful to all employees. Obsolete data-record versions and insufficient information flows constitute sources of error which should not be underestimated. Since the development and planning process is characterized by a multiplicity of iteration loops, adaptations are absolutely necessary in all departments of the company and in all phases of project execution. Particularly in the digital factory, special demands are imposed on the maintenance of data and the management of versions in this respect. It must be ensured that up-to-date, subject-specific,
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relevant data are continuously and immediately available to all those concerned, especially in the event of changes. The large quantities of data and the equally large number of different data formats constitute one of the main problems associated with the digital factory. 3.3. Processes and structures It is assumed that the existing structural organization of company departments will change as the digital factory becomes more widespread. Fewer physical prototypes will be required, and various specialized departments will be combined to an increasing extent. A redistribution of functions and responsibilities will be necessary for creating integrated and efficient design processes. Moreover, the concerned personnel will be confronted with new planning procedures. The conventional phase models of project work must likewise be eliminated, since a clear-cut delimitation of individual steps no longer makes sense if the potential of the digital factory is to be fully utilized. In this context, simultaneous engineering will become a necessity, and its possibilities will be utilized to the limits. At present, only speculation is possible in connection with the actual structures of the hierarchical and sequential organizations within companies in the future. In any event, it is certain that decisive changes will occur. As already pointed out in a publication [3], the essential supporting pillars for the digital factory may already be standing by 2005. However, the conversion process itself will require much more time, more than was required for the introduction of CAD systems. Furthermore, considerable research and innovative solutions will be necessary. 3.4. Commitment At present, the digital factory is still a project for large-scale enterprises, especially for OEM’s in the automotive industry. Large amounts of capital are being made available for making the vision come true. However, questions concerning the necessary level of implementation are also receiving increased attention. Conversion of the incurred costs to yield a financial return flow is not yet possible. Of course, many of the software tools necessary for processing individual
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partial aspects of product and production development are already available and have also been tried and proved in applications. However, the available resources are not yet sufficient to allow for a rapid and useful application of these tools, especially in small and medium-sized enterprises. Consequently, not only internal structures are subject to change; in particular, cooperation among companies must also be adapted accordingly. This matter is currently being considered, too, and the objective is to achieve continuity at least up to the 2nd tier suppliers. In the course of these deliberations, however, one question is seldom considered: are the SME, who are very likely to be among the 1st or 2nd tier suppliers, really capable of adequately implementing the digital factory? These smaller companies usually do not have large planning departments of their own for dealing with production requirements, and they usually cannot afford the corresponding software tools. Consequently, it will be difficult for them to utilize the potential offered by the digital factory [1]. For many small companies, investments of this kind are hardly feasible, since they are not economically justifiable as long as the price of the necessary software remains so high, and current expenses can hardly be borne by small companies. Initial approaches toward possible solutions have already been attempted [5], but have not yet found widespread acceptance. Major reasons for this reluctance certainly include the lack of information and the absence of appropriate structures on the part of the KMU. Nevertheless, the digital factory approach is not merely an inevitable necessity; it also offers a chance for some medium-sized suppliers. In this case, too, considerable potential savings could be achieved by implementing the appropriate structural measures and with support from external service companies.
4. The reality of the digital factory The vision and the associated problems have been described. However, what is the current developmental status of the digital factory? In this context, it should first be mentioned that the level of implementation already achieved by some companies cannot be determined exactly. Hence, the following discussion should be regarded as a summary of the
authors’ experience and an analysis of the published information. At least one thing is certain, however, large investments in the digital factory have already been realized, especially in the automotive industry and by many 1st tier suppliers. Furthermore, it cannot be denied that companies have already achieved success in certain partial fields and in pilot projects. An example is the nearly uninterrupted application of various planning tools by automobile manufacturers in vehicle body construction. Product data integration, robot simulation, and the associated off-line programming have already become established there. Two large software suppliers currently constitute the supporting columns of the digital factory. As indicated by current knowledge, however, it is not necessarily probable that a software platform can cover all facets of the digital factory. Previous cooperation among the suppliers of tools, which may be applicable within the scope of the digital factory is by no means adequate, and the demands imposed on a central, standardized data management system can hardly be satisfied at present. For small and medium-sized enterprises, many of the tools are still much too expensive, or cost recovery from applications is not possible. Nonetheless, some of these companies are already requesting delivery of certain proofs or data in digital form to match their customers’ respective digital factory. An increasing number of system suppliers also offer services in conjunction with the digital factory. Since the various computer-aided tools in the developmental, design, and planning stages are so numerous, however, these suppliers must also come to grips with a multiplicity of interfaces. Furthermore, they are forced to keep almost all software tools available, in order to be able to satisfy the needs of as many customers as possible. This requirement also poses the question of economy and will further aggravate competition. Hence, it must be concluded that inherently necessary, standardized networking of the tools is hardly feasible, since the structures of many tools do not allow for docking with other modules or applications, or at least render an adaptation difficult. Furthermore, the problems of version and data management have not yet been solved. These factors could further increase the multiplicity of insular
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software solutions in the various company departments. Regardless of which decision is reached in favour of a particular general supplier of software for the digital factory, certain advantages as well as disadvantages will always result from the choice. For instance, it cannot always be assumed that all problems associated with the interfaces between supplier-specific software tools have been solved. Since the existing company structures tend to reflect conventional patterns of thought and work, and since the new process and method orientation is not yet practiced in a comprehensive manner, only a limited portion of the potential savings can be achieved with the insular IT solutions. The real possibilities offered by the digital factory are accessible only through an appropriate networking of all tools in combination with a restructuring of the processes and hierarchical organization of the companies. Reconsideration and redistribution of competencies and responsibilities will also be necessary. Furthermore, a considerable untapped potential is still available from the computer tools themselves. The user interfaces of the tools and the user guidance must become considerably more intuitive. After all, the user’s creativity should not be subordinated to the formalities of the tools; in particular, ideas must be implemented and tested quickly and simply with the use of the computer.
5. Small steps toward success—an example of research at IMAB The following project description should provide insight into the fundamental research in progress at IMAB on the subject of the digital factory. In order to allow for interdisciplinary discussions among the project participants from different fields of specialization, the concept of the virtual communication platform is frequently employed in conjunction with the digital factory. Above all, this term designates a virtual-reality-oriented tool, which is employed to allow for a more effective visualization of various planning results. For instance, the results of the design process can thus be considered together with the factory planners’ data and the logistician’s concepts. Joint planning meetings before and during VR projection thus allow for more efficient mutual
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agreement on the work and support the continuing development activities on the basis of results which are already available. An example is the so-called digital mock-up, which permits the virtual assembly of individual components and subassemblies. A further field of research is the networking of results from material-flow simulation and layout planning. In this context, the functions of a material-flow simulator have been integrated into a VR model developed at IMAB [2]. 5.1. Objectives For the new manufacturing technology based on high-frequency welding in the sheet-metal industry, a general survey already indicates the possible range of series applications in future production, even at a very early stage of development. The short process time for the welding of sheet-metal profile components by this method had suggested the possibility of applying this technique to the manufacture of modular-design components. The associated requirements on the structure of a production plant should be investigated, especially from a logistics point of view at this early stage of process development. 5.2. Procedure In order to find a realistic approach to the problems posed by the new manufacturing process, a fictitious subassembly was designed; this subassembly consisted of three individual components and could be produced in 10 different versions by high-frequency welding. From the structure of the subassembly, the necessary manufacturing facilities were then derived and combined to form a production cell in a preliminary draught. For this purpose, two of the three components had to be manufactured directly in the production cell. For one of these two components, five versions of different shape and material were envisaged. Since a metal-shaping press was to be used for its manufacture, a component buffer had to be included in the system to ensure continuity of supply for production. In Fig. 3, the virtual prototype for the process is illustrated for high-frequency welding. On the basis of the preliminary layout draught for the production cell, the construction of a model for material-flow simulation was attempted, in order to
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Fig. 3. Illustration of the virtual prototype for a process involving high-frequency welding.
test the functioning and efficiency of the system. Upon parameterization of the simulation model, however, an exact determination of the times – almost by memory – proved to be impossible for most of the manipulation and clamping operations as well as for the entire process sequence in the high-frequency welding facility. For this reason, and also in view of the technical possibilities offered by the VR laboratory at IMAB, it was decided to construct a VR model. The purpose of this model was to visualize the kinematics of the welding facility as well as all operations, in order to allow conclusions to be reached regarding the actual process and operation times. From the basic design and conception of the welding facility, an animated VR model of the production cell was constructed within a period of 5 months. For this purpose, the system layout was structured and further developed by an interdisciplinary project team during several work sessions in the VR laboratory. The discussions among the specialists were supported in a decisive way by the three-dimensional models and the stereoscopic, large-screen projection; as a result, the virtual reality assumed the function of a communica-
tion platform. After completion of all work for the modelling of the 3D layout, the idea of integrating the functionalities necessary for the material-flow simulation into the VR model was considered. The model was adapted correspondingly during the following 4 months. For instance, all machines were provided with programs, which allowed a parameterization of perturbation functions and the associated distributions by means of input masks, as is the case with commercially available material-flow simulators. Moreover, an additional function, which allows for intervention in the distribution of the versions to be produced was included; by means of this function, the behaviour of the system under modified boundary conditions can be analyzed. Provision was also made for free parameterization of the buffer inventory. As soon as the buffer inventory falls below a specified minimum, the manufacturing process is initiated for the corresponding version of component 3. The VR model thus constructed is designated as a virtual prototype for a process and combines the functions of a simulator with the possibilities of 3D visualization.
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5.3. Conclusions resulting from the research project on the digital factory On the basis of the approach described here, and with the virtual prototype for the process as a model example, important conclusions have been reached for the implementation of preliminary production plants with new manufacturing technologies. In this manner, a possible structure for future production by high-frequency welding has been validated as a basic concept. The results of this and similar approaches suggest that considerable progress has already been achieved on the way toward the digital factory. However, the question of the cost-to-benefit ratio is still open.
6. Conclusions It can be concluded that the vision and progressing realization of the digital factory include the essential formulation and potential solution of almost all problems posed by future planning methods and production. Whoever wants to face the brutal global competition must decrease the time required for the realization of products as well as production by orders of magnitude and simultaneously improve the quality. For this purpose, the digital factory is an absolute prerequisite. However, many considerations on the subject of the digital factory suggest that no single company alone will be capable of totally meeting this challenge. For this purpose, extensive cooperation among numerous companies and institutions will be necessary. The objective of acquiring and maintaining competitive advantages single-handedly entails the risk of becoming totally isolated, since too many company-specific software solutions must be developed. The care of such software must also be specific. In the long term, the use of company-specific software will decisively aggravate the difficulties in coupling with development partners, suppliers, and service companies. As a result, only partial success can be expected with such an approach.
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In order to avoid failure with the vision of the digital factory in the short term, an unambiguous orientation of the results is necessary. Obvious projects and objectives must be approached directly and successfully executed in a step-by-step manner. In all of these endeavours, attention must be focused on the prime requirement of maintaining and ensuring the viability of the company in the future.
References [1] U. Bracht, T. Masurat, The forgotten factories, wt-online 4 (2002) 154–158. [2] U. Bracht, T. Masurat, Integration of virtual reality and material flow simulation for digital process specimen – mind games in logistic and production for the digital factory, wt-online 4 (2003) 249–253. [3] E. Schiller, W.P. Seuffert, Bis 2005 realisiert, Automobil-Produktion. (2002) 20–30. [4] Spur G. Fabrikbetrieb. Mu¨ nchen: Hanser; 1994. [5] E. Westka¨ mper, S. Bierschenk, T. Kuhlmann, Digital manufacturing – only for large scale enterprises? wt-online 1/2 (2003) 22–26. Professor Uwe Bracht, born in 1949, studied mechanical engineering at Hannover University. He is director of the Institute for Plant Engineering and Fatigue Analysis (Clausthal Technical University) and founding member of the VDA research group ‘‘Computer-Aided Factory Planning’’. Since 2002 he is heading the VDI expert committee ‘‘Digital Factory’’. His publication list contains more than 50 papers dealing with the improvement of factory planning and organization processes. Thomas Masurat, born in 1967, studied mechanical engineering at Clausthal Technical University, focussing on production technologies. Since 2000 he is scientific assistant at the Institute for Plant Engineering and Fatigue Analysis; mainly dealing with facility planning and logistics tasks.