taken in institutions and production companies. ... all of these activities within a manufacturing enterprise. It is also ... between these various software packages.
Int J Adv ManufTechnol (1992) 7:101-108 9 1992 Springer-Verlag LondonLimited
The klternatiornd Journal of
Rdvanced manufacturini Technologu
An Exploration of Simultaneous Engineering for Manufacturing Enterprises H.-C. Zhang* and L.
Alting*
*Department of Industrial Engineering,Texas Tech University, Lubbock,Texas, USA; and 'institute of ManufacturingEngineering, Technical Universityof Denmark, Lyngby,Denmark
With the increasing application of high technology in manufacturing enterprises, the traditional serial or sequential production approach has begun to be replaced by a parallel or simultaneous production approach. The functional balance of organisations of current manufacturing enterprises is decline. The organisation within manufacturing enterprises needs to be restructured and the functions need to be adjusted. Many production functions within an enterprise can be integrated by foUowing the production information. This is the premise of this exploration of simultaneous engineering in manufacturing enterprises. A functional model of an enterprise is described in this paper. Some possibilities of functional integration within an enterprise are discussed. Finally, some related research activities are outlined to stimulate an open discussion on the point of view.
Keywords: CIM; Engineering management system (EMS); Factory of the future; Model of manufacturing enterprise; Simultaneous/concurrent engineering
1.
Introduction
In looking at the impact of high technology on manufacturing enterprises during the 1980s, a number of remarkable premises are involved. Among these high technologies can be mentioned electronics and computer technologies, new machine tools, robots, CVD, PVD, etc. Of these, the computer has had the major impact, especially because it influences all the functions in a company. Computer-integrated manufacturing (CIM) has been proposed as a new
Accepted for publication: 12 January 1991 Correspondence and offprint requests to: Hong-Chao Zhang, PbD, Assistant Professor, Department of Industrial Engineering, Texas Tech University, Lubbock,Texas 79409-3061, USA.
manufacturing philosophy and has been addressed with great efforts in the last two decades [1-5]. Computer-integrated manufacturing has been discussed as the vision of the factory of the future for a long time. Integrated manufacturing systems are supposed to make up a major part of the factories of the 1990s. Now, when we are already into the beginning of the 1990s, many of the proposed potential benefits from integrated manufacturing are still to be seen. Naturally, some questions have to be asked: Why is the present situation not very satisfactory? Have we already found the correct way to realise the final integrated manufacturing? If the answers to these questions are not satisfactory, we might further ask: What are the problems for current manufacturing? What should we do in this coming decade? Some of these questions will be addressed in this paper and some answers will be put forward. It is important that when high technology (for instance computer technology) is applied in an enterprise, it occasions not only an adjustment of equipment, an adjustment of the requirement for skilled workers and an adjustment of production tasks, but also an adjustment of the enterprise's organisation. This latter adjustment is a vital factor in achieving the expected potential benefits from the application of the technology. This situation has attracted some attention and some research activities have already been undertaken in institutions and production companies. Simultaneous engineering is one of these advanced research activities. In the last couple of years, simultaneous engineering has been much discussed in the literature [6-10]. However, if we study all these previous research activities, we might find that very few of them focus on the production functions, activities and practices which might influence the adjustment of the structure of an enterprise. From the viewpoint of rea[ising simultaneous engineering, analysis of production functions, activities and practices is very important. Generally, it is impossible to realise the concept of simultaneous engineering in the factories
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of the future unless we can understand the production functions and structures of manufacturing enterprises very well. This paper is focused on the analysis of current production functions, activities and practices, This discussion will provide some fundamental theories and requirements for applying simultaneous engineering in current production enterprises.
2.
Simultaneous Engineering
Simultaneous engineering (SE) has been called by many different names, including concurrent engineering, lifecycle engineering, concurrent product and process design, design for production, design for manufacturing, design for assembly, integrated and cooperative design, design fusion, producibility engineering and system engineering. Whatever it is called, the meaning of simultaneous engineering is a merging of the efforts of product designers and manufacturing engineers to improve manufacturing processes and products. Simultaneous engineering has been defined in many different ways. McKnight and Jackson defined it as follows [6]: Simultaneous engineering is the concurrent development of project design functions, with open and interactive communication existing among all team members for the purpose of reducing lead time from concept to production launch. It has also been defined in another way, that is [11]: Concurrent engineering is a systematic approach to the integrated, concurrent design of products and their related processes, including manufacture of support. This approach is intended to cause the developers, from the outset, to consider all elements of the product life cycle from concept through disposal, including quality, cost, schedule, and user requirements The above two definitions may indicate that the lead time should be significantly reduced as a result of simultaneous engineering, because the design is not passed from group to group. All disciplines required are members of the same team, reporting to the same management. That means that to realise simultaneous engineering in production, the current structure of a manufacturing enterprise has to be reorganised. The boundaries between each group have to be broken. The new cross-functional teams have to be established in the manufacturing enterprise. In addition, SE is characterised by a focus on the customer's requirements and priorities, a conviction that quality is the result of improving a process, and a philosophy that improvement of the processes of design, production and support are never-ending responsibilities of the entire enterprise. In general, simultaneous engineering may involve four '~C" aspects, as follows [12]:
Concurrence: product and process design run in parallel and occur in the same time-frame. Constraints: process constraints are considered as part of the product design. This helps to ensure parts that are easy to fabricate, handle and assemble and to facilitate the use of simple, cost-effective process, tooling and material-handling solutions. Coordination: product and process are closely coordinated to achieve optimal matching of needs and requirements for effective cost, quality and delivery. Consensus: high-impact product and process decisionmaking involve full team participation and consensus. In recent research activities, simultaneous engineering is discussed within two spectrums, namely from the macrocosmic viewpoint and the microcosmic viewpoint. In other words, simultaneous engineering can take place at two levels of implication - the external environment level and the internal environment level. The external environment is the macrocosmic oriented one. At this level, the four "C" aspects mentioned above have to occur between a manufacturing enterprise and its associated business partners, such as the suppliers and customers of a manufacturing enterprise. Fig. 1 illustrates the external environment level. The internal enviromnent is the microcosmic oriented one. At this level, the four "C" aspects occur between different departments of a manufacturing enterprise, such as the design department, the manufacturing department, and so forth. Fig. 2 illustrates the internal environment level, To realise either tile external- or the internal-level implications here, a dynamic common database system, in some cases also referred to as an engineering management system (EMS), plays a key role in linking all of these activities within a manufacturing enterprise. It is also a critical factor for communicating between the two levels. The dynamic common database will provide the enterprise with a single view of engineering, manufacturing and management information through-
Fig. 1. The external environment level of simultaneousengineering.
An Exploration of Sirnuhaneous Engineering
~YNAM~ Fig. 2. The internal environment level of simultaneous engineering.
out the product life cycle. Dynamic information about the enterprise's suppliers and customers can also be provided by such a dynamic common database system. The detailed discussion of such a database is beyond the scope of this paper, but may be found elsewhere [13,14].
3.
Current Situation and Problems
One of the ultimate challenges in engineering is the goal of developing useful, reliable and economic products. In order to reach an advanced level of these strategies, many efforts have been made by manufacturing enterprises. An important example is the impact of modern computer technology on engineering design and manufacturing to reduce production cost, lead time and inventory, and to increase productivity, quality, equipment utilisation, etc. Based upon this technology, many tools have been developed by various industries, vendors and research institutions in order to support the design and manufacturing functions. These computer-supported developments are now being offered to industry and represent such developments as: CNC/DNC - computer numerical control/direct numerical control CAD/CAM - computer-aided design/computer-aided manufacturing FMS flexible manufacturing systems CIM computer-integrated manufacturing CAE - computer-aided engineering CAPP - computer-aided process planning Automated NC programming Specially developed software package to support different functions -
-
However, these developments are not coordinated, and they contain a great deal of overlap in terms of their intended functions. For example, CAD/CAM systems have their strength in geometrical modelling, i.e. the CAD part; the CAM part is usually limited to NC/CNC programming (a CL-file which must be postprocessed), but nesting, process planning, etc. are included in some systems. Developments are taking
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place that will bring more CAM activities into CAD/ CAM systems in the future. These developments are not coordinated with other systems and will thus lead to various overlaps. A second example is the CIM (computer-integrated manufacturing) concept. It is ill defined and may contain elements of such technologies as GT (group technology), MRP I (material-requirements planning), MRP II (manufacturing-resource planning), CAPP (computer-automated process planning), and so forth. It may also contain elements of product design, production planning, production control and control of production equipment and processes. It is important to note that the above technologies represent the development of a tremendous number of specialised software packages by different vendors, suppliers and developers. Unfortunately, they also reflect different points of view concerning the different functions of a manufacturing enterprise and the interrelationships between these various software packages. Integration of these elements has been attempted in some cases, but in most instances as an afterthought. These independent automated systems can not share data and functions with each other. They are only "isolated automation islands", yet it is very easy to call them "'integrated systems". The primary objective of such software should be an ability to share various functions in an enterprise and to operate as a system in order to transmit and process vast amounts of data. The effective use of computers and communication equipment, as well as their integration into a single system, which includes humans, is crucial in realising this. "Linking" or integration of the activities in an enterprise through a dynamic common database allows the management of data flow while directing material and conversion activities. It should give the ability to organise, control and direct the huge amount of information required to produce even the smallest item. Companies must be viewed as a whole, instead of as a conglomeration of parts. In order to work towards the above goal, one must first have a well-defined concept of all the functions and activities of an enterprise in terms of the inputs and outputs that are generated by each function and activity, before attempting to solve this "linking" or integration problem. Generally, these functions and activities are ill defined, and therefore it becomes very difficult to obtain a clear idea of what is included in the term "linking" or integration. In order to gain a clearer understanding, it is necessary to attempt to establish a general and generic model of a company by analysing its main functions, decomposing these main fucntions into specific functions and associated activities, and defining the necessary information flow (in terms of inputs and outputs for each function) in order to carry out these activities within a company. It is our belief that a generic model can provide an appropriate basis for the definition of
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integration. More importantly, it serves as a base for ascertaining which computer-supported tools are available and which must be either tailored or even developed to enhance the integration process. In the following section a general generic model of a company is structured. The described model, which is based on that described by Alting and Olling [15], is to be considered as a concept and not as a final model.
4. A Model of a Manufacturing Enterprise The success of an integrated manufacture system rests on the accuracy and completeness of design performance, management information and fabricating output data. More and better information must be transferred across the interface between management and engineering and fabrication. Industry needs an integrated systems approach converging its main functions, specific functions and activities. Such a systems approach would provide a top-down information-flow architecture, enabling a bottom-up implementation. The aim has been to develop a model of a company and to identify its structure in terms of:
Engineering (defines, formulates and evaluates) Fabrication (organises, executes and distributes) For clarity, the following terms are defined: "Manufacturing" is used as the overall term to describe all the activities within an enterprise, i.e. according to the original definition of the word. "Management" includes the general industrial engineering activity, i.e. the activities related to scheduling. "Engineering" covers both design and manufacturing engineering to describe their closeness or integration. "'Fabrication" describes the actual physical production. As indicated in Fig. 3, the general main functions are integrated by an informational "highway structure". Each main function can be decomposed into specific functions (see Fig. 4).
Management. Under management, the following specific functions have been identified: 1. 2. 3. 4, 5.
Sales and marketing Finance/accounting Production planning and control Policy-making and strategic planning Personnel
Main functions Specific functions Activities within the functions Information flow (input-output) necessary to carry out the activities
As indicated above, these functions together represent the total main management function. However, it has been realised that, depending on specific company structures, variations in the decomposition may exist.
This general model would enable the development of a coherent functional and informational network which could serve as the necessary background for the development and implementation of the computersupported tools. This structure and network can be considered as a tubing system, in which actual data can be guided to the right activities, thus enabling the activity to be carried out. It is a misinterpretation to assume that data obtained from various sources can substitute for company data. The company data represents the tradition, know-how and business infrastructure which must be captured. Thus, a generic architecture with a well-defined network of functional and activity relations, i.e. an information flow network, is necessary. The following sections present a generic picture of a company, its main functions, specific functions, activities and associated information input and output, as well as their interrelationships.
Engineering. The main engineering function includes the following specific functions and is divided into two equally important branches - design and manufacturing. Design has the following functions:
4.1 General Main Functions in an Industrial Enterprise
It must be noted that integration between design and manufacturing is considered vital. This can be seen from the fact that the first and last functions are common and that parallelism between the other functions is established. The parallelism is also intended to reflect vertical and horizontal integration. This capability should immesurably improve the accuracy
The general main functions in a production company are (see Fig. 3): Management (plans, analyses and controls)
6. 7. 8. 9. 10.
Need verification Product-principle design Preliminary product design Design maturation Product/manufacturing verification
Manufacturing has the following functions: 6. 11. 12. 13. 10.
Need verification Manufacturing-principle design Preliminary manufacturing study Manufacturing preparation Product/manufacturing verification
An Exploration of Simuhaneous Engineering i
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of communication throughout the entire manufacturing environment. Fabrication. Under fabrication, the following specific functions have been identified:
14. I/O lager (incoming and outgoing materials and products, including handling, preparing, storing and retrieving) 15. Equipment and set-up 16. Quality control and testing 17. Plant operation Fabrication is here defined as an organising, executing and distributing function based on documentation from management and engineering, physical facilities and personnel. Fig. 5 shows how production equipment
can be organised in different ways in order to achieve maxinmm productivity. If the elements listed in Fig. 5 are integrated into the information flow (Fig. 3), the CIM philosophy is approached. 4.2 Activities Within the Functional Structure
In order to define the general information flow between the functions, each specific function has been further decomposed into activities reflecting the tasks of the function. For each activity (task), the necessary information inputs and the produced outputs must be defined. Different techniques can be applied for modelling the information flow [15], but it is outside the scope of this paper to go into detail here.
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Production planning and control activities, leading to the production master schedule, which contains answers to when, where and how much.
MACHINE TOOLS 9 cutting 9 forming 9 finishing Depending on production requirements, these elements may be organised as:
CONTROL 9 NC, CNC, DNC 9 AC 9 PC
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Fig. 5. Organisationof fabricationequipment. If we look at the transformation of input to output for the activities within each function, appropriate tools must be used. These tools can be divided into methodological tools and general tools. The methodological tools support the involved functions, i.e. theories, methods and procedures characteristic to the professional work. The general or specific tools support the application of the methodological tools, i.e. FEM analysis, simulation, geometric modelling, decision and classification tools, knowledge engineering. To carry out the actual transformations, datahandling tools must be used for information storage and retrieval, extraction, reformation, dynamic updating, etc. A careful analysis of the activities and the related input and output of information flow can lead to a logical grouping of these activities. Furthermore, these groups can represent reasonably well-defined areas requiring similar methodologies. As an example, the following areas are presented: Manufacturing engineering activities (integrated with design activities), leading to a manufacturing master plan which contains full documentation for the product and how it is to be produced. Design engineering activities (integrated with the manufacturing engineering activities), leading to the final specifications of the product, including the bill of materials.
For each of these areas, the necessary methodological tools must be defined (theories, methods, procedures, etc.) and any weak points strengthened.
5. Trends of the Development The results from recent researches have indicated that our previous vision of the factory of the future, in which the human being will be replaced by intelligent robots - the unmanned factory - is indefinite. On the contrary, the revised perspective of the situation is clearly that the human being has an important role in the factories of the future. All the tasks of global and process supervision, schedule changing, correcting errors, and implementation of knowledge and experience have to be done by human beings. These trends confirm that the CIM philosophy is still valid, but the emphasis is now more on the "I" - integration, including functional integration, necessary changes in the company's organisation, the role of the human being, etc. As a matter of fact, the concept of simultaneous engineering is exactly centred on the ' T ' of CIM. It not only emphasises the integration within a manufacturing enterprise, but also the macrocosmicviewpoint integration. That means that the integration will also occur between several manufacturing enterprises, such as in a business-partners group. Some related research projects, for instance design for manufacturing, design for productivity, design for assembly and development of engineering management systems (EMS) all follow this strategy. This clearly indicates the need for a functional level. The area of computer-aided process planning produces many systems for operations planning but not for process selection in integration with design. These few lines serve only to indicate that in order to enhance the development we shall have to work towards functional integration and not only towards information-flow integration based on the "old" organisational structure in the company. The traditional serial or sequential approach (see Fig. 6) will have to be replaced by a parallel, simultaneous or cross-functional team approach. To move in that direction we must change our organisational structures, since they at present tend to preserve the inherent power structure. On the more detailed level we shall have to study the allocation of tasks between the computer controller and the human supervisor and, more important, how communication between the computer and the human can be enhanced [16]. These few remarks do not pretend to be exhaustive but only to illustrate a trend. Another area attracting interest today is how information technology is changing business opportunities
An Exploration of Simuhaneous Engineering
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integration. This research should be tightly linked with industrial companies.
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[17]. In most manufacturing enterprises we have witnessed investment in new equipment (hardware and software) only as an automation of existing functions and activities in the company: a mentioned above, functional integration, change of organisation and so on were not discussed prior to the investments. Beyond that, the companies have not realised the changed customer expectations concerning quality, services and so forth, and the fact that information technology creates new business possibilities. A company can establish a close collaboration with suppliers and customers based on direct electronic links tying the suppliers and customers closer to the company. This "integration", which can bring new and better products, is not caused by the information technology but made possible by it [17]. Therefore when companies invest in information technology they will have to look carefully at which desired business opportunities will now be possible, Increasing attention is therefore being paid to a number of basic research areas, which must be pursued if companies are to be brought into the next century. Among these are:
A functional model of a manufacturing enterprise. Here it is necessary to develop a model describing the functions and activities, with the functions and so forth seen from an integrational point of view (see Section 4). An important part of the development of the model will be the study of functional relationships and
A study of the mental processes associated with the various functions. If we think about the integration of design and manufacturing, we need to study the mental design process and the associated manufacturing functions to be able to develop the coupling or integration between these. A mental model of the functional integration between design and manufacturing will lead to a specification of the tools necessary to support this. This in turn may influence the development of new computer-based tools so that they are based on functional requirements and not on what computer or software companies think that they can sell. The human being in manufacturing. The roles of human beings in manufacturing will have to be studied from different points of view and at different levels, for example expectations/work satisfaction, supervising, monitoring, decision-making, etc. Which computerbased tools, for example artificial-intelligence techniques (knowledge engineering), can enhance the human's skills? A very important aspect here is the interface between the human and the computer. Most computer-based systems today are not a result of a thorough study of how the human can interact with computer-based systems in an optimal way. We shall have to learn how to design the interfaces based on the integrated roles of humans and the communication roles between computer and humans.
Computer-based tools to support the integration of functions. The development of CAD, CAM, CAPP, CAE, etc. which are more or less based on artificial intelligence/knowledge of engineering, expert systems and so forth, must be based on the functionalintegration viewpoint leading to some modification of the existing systems. The information-flow computer integration is made easier and easier through better and better communication standards. Today we see many useful developments within planning, scheduling, shop-floor control tools and so forth which to some extent have taken notice of the above trends. But this has to be reinforced, and more weight should be given to the point that these systems are to be seen as an enhancement of human skills and not as automated decision-making systems.
How to organise functions within a company to support the integrated factory of the future. The present organisation will have to change in the future (it is already changing in many places) to support the integration, i.e. the cross-functional working method. This is a team approach, where each team has responsibility for a product throughout its life history. It is necessary to develop new organisation structures in conjunction with the study of functional integration and the roles of human beings in manufacturing.
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Customer-required high-quality products, global competition and computer-supported integration in products and production systems all depend on better and better scientific knowledge in manufacturing. It is necessary to develop A new science of manufacturing.
or to introduce science broadly in engineering design and manufacturing. A science of manufacturing will include theories, methods and knowledge on different levels of abstraction. It is necessary to stimulate the development of knowledge (theories, methods and experience) about manufacturing processes, manufacturing systems, planning, scheduling, contracts and so forth. This may provide a structure for the important data capture. In the future we should discuss what we should include in a science of manufacturing and start to introduce the concepts in education and research.
6.
Conclusion
The Delphi forecast has predicted that the technology which will make the greatest future contribution to a shortening of a product's development time will be simultaneous engineering. It also indicated that the technology in which manufacturing engineering will be most extensively involved throughout the industry by the year 2000 is computer-integrated manufacturing [3]. However, the research activities for simultaneous engineering are now just on the increase. We are still in the beginning stage of application of the concept of simultaneous engineering in the production environment. Full capability for simultaneous engineering is still a long way from being accomplished, owing to technological hurdles which must still be surmounted. In this paper an exploration of simultaneous engineering in manufacturing enterprises has been discussed. This discussion may provide some fundamental theories for application of the concept of simultaneous engineering in production companies. With the rapid development of high technologies, the traditional serial or sequential production functions have been changed to the simultaneous or parallel production functions, so that the structure and organisation of the manufacturing enterprises have to be adjusted to keep the organisation in balance. Sections 3 and 4 have indicated this adjustment. Some related research areas have been
mentioned in this paper. However, the discussion of these research activities is far away from sufficiency. A paper introducing the "state of the art" in simultaneous engineering will follow to compensate for this shortage.
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