Sequential, Design Centered, Concurrent and Dynamic

Journal of Engineering Design, Vol 10, No. 1, 1999

Four Models of Design De® nition: Sequential, Design Centered, Concurrent and Dynamic

BABACK YAZDANI & CHRISTOPHER HOLMES

SUMMARY Most organisations adhere to one form of product de® nition as the core of their product development process. The dominant design methodology employed is the foundation upon which the process has to be de® ned. This paper identi® es four very diþ erent models for design de® nition: sequential, design centered, concurrent and dynamic. Using case studies from the automotive and aerospace industrial sectors, this paper illustrates the models identi® ed, which appear to be based on the dominant and prevailing drivers of new product introduction for a given company. The sequential model shows the traditional functionally based organisation and explores how the design is developed through the various functions. The design centered model demonstrates the front end ® xing of the design through the use of Design for Lifecycle tools and techniques. The concurrent de® nition model introduces the concept of concurrent engineering and stage gate systems, with the design de® nition being ® xed at various gates in the process. Finally, the dynamic model demonstrates the interaction of the various functional skill groups and shows a radical departure in the way the design information is transferred in complex organisations.

1. Introduction The pressure to adopt new methods to improve product introduction has recently been intensi® ed, and many companies are implementing a variety of methods, tools and techniques, organisational designs, etc. in response to quality, cost, and time pressures. The main strands of improving new product introduction (NPI) in companies have been centered around the adoption of formal stage gate processes [1] and concurrent engineering (CE) practices [2, 3]. The formal stage gate system process seeks to provide a formalised process for the development of new products [4]. While the process is controlled by a number of formal reviews [5], the pressure on lead time reduction is critical [4], hence the need to employ CE techniques. CE itself has been the subject of development in terms of philosophy, tools and techniques, and information technology (IT) applications. However, the purpose of CE is to reduce this lead time by overlapping activities as well as reducing the length of time in each activity. In CE, the activities of design and development of products and their processes have to overlap. Figure 1 demonstrates the diþ erence between sequential and CE, and the main reason why companies wish to implement CE, i.e. compressing the lead times of product development. Although in any given product grouping, such as car or aircraft development, the sequence and B. Yazdani & C. Holmes, Department of Engineering, University of Warwick, Coventry CV4 7AL, UK. 0954-4828/99/010025-13 $7.00

€ 1999 Taylor & Francis Ltd

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FIG. 1. Concurrent and sequential engineering. phases of design and development remain essentially the same, the detail of practice and forms of CE application tend to be widely diþ erent according to the dominant design philosophy of a company. This itself is generally embedded in the culture and educational paradigm of countries and regions [6, 7]. Diþ erent design methodologies are the foundations upon which a company’ s NPI process is based. In order to examine the underlying principles of how companies improve their NPI, a number of diþ erent companies with varying design backgrounds, from the two sectors of automotive and aerospace, were studied. The areas under observation, in this research, were organisation, management, process orientation, types and levels of teaming, tools and technologies employed, levels of integration across the process, dominant measures of performance, information ¯ ows and the prevailing design methodology. The explanation of the models is split into a number of key areas. The ® rst of these explores the concurrency of the model. This is explored in more detail through an examination of the information exchange between the varying functions. The enabling methods and technologies are then reviewed, followed by a review of the change process, and its control. Organisational aspects are then discussed including the style of management. Finally, the dominant driving forces and measures of performance (MOPS) are discussed. Examples are provided to illustrate instances of the models.

2. Methodology Two major industrial sectors, aerospace and automotive, were investigated in order to establish the main types of design de® nition practiced in industry. The companies under observation came from a number of diþ erent countries across Europe, Japan and the US in these two sectorsÐ exhibiting very diþ erent approaches to NPI. Over a period of 3 years, six automotive and two aerospace companies were

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investigated using structured interviews. In some cases, the depth of research was strengthened by collaborative action research projects (including the Time Compression Programme, sponsored by Industry and DTI, the Engineering Doctorate Programme, sponsored by EPSRC, and industrially based Doctoral Research Programmes), giving the authors a greater insight to the workings of NPI in the mentioned industries. The main parameters considered for this paper were (i) NPI driving forces and MOPS; (ii) risk; (iii) time; (iv) cost; and (v) quality: ·

·

· · ·

Driving forces and MOPs were determined by directly asking the company senior management and NPI managers to identify and rank the factors and criteria employed in each ® rm. This was supplemented by the general prevailing conditions of the given industry determined from publicly available literature. Risk was measured in terms of technical and commercial risks for both incremental and breakthrough products. The broad classi® cations used to categorise risk were based on a number of new technologies for product and process required (technical risk) and the size of committed expenditure as a percentage of company turnover. This was then broadly classi® ed as high /medium/low. The measurement of time corresponds to lead time (critical path) from project launch (concept approval) to volume production. Cost was measured in terms of project costs throughout the process. Quality of design was measured in terms of cost of engineering changes and also the stage at which change was necessitated.

The generic results are described. 3. The Sequential Model The sequential model for design de® nition is that the product is designed and then all the functions add their input to the design in a sequence of activities, with the process being repeated until a satisfactory result is output from the last function. This traditional model of development has proved not to be satisfactory for today’s industrial pressures where cost, quality and time parameters are far more demanding than ever before [8]. Time, in particular, has now been recognised as the determining performance parameter [4, 8± 10]. This has brought on a whole host of models for developing new products including stage gate systems [4], product development funnel [11], CE [2, 3], etc. Information here is batched at each stage and passed on to the subsequent activity, such as from design to build, and so on, until production is ready (Fig. 2). The enabling technology and methods used for sequential engineering are based on the individual functional requirements with very little integration. Hence, the tools used are functionally orientated rather than process orientated. Often, there is no protocol for the transfer of information between the diþ erent tools employed. The prototyping process, under the sequential design, takes place after the detail design is completed, and productionisation normally waits until the results of the tests are satisfactory. Many product design changes are initiated at this stage. The change process and its control are normally characterized by the `over the wall’ scenario. Most of the manufacturing changes are normally initiated in the manufacturing process and taken back to the detail design stage. Depending on the nature of the change required, parts of or the whole process may be repeated. This has a signi® cant eþ ect on the lead time of the development system. The dominant organisational constructs for this model are functional silos [12] with functional management acting as the liaison point. The leadership of each function is

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FIG. 2. Sequential engineering. responsible for the control and eý ciency of its own domain, with measures of performance relating to the function rather than the process. Normally, many layers of management are prevalent in this type of organisation, as necessitated by the information ¯ ow structure. Hence, the de® nition of the product in its detail is carried out in a sequential manner. The driving forces within companies that employed the sequential model were determined to be predominantly based on cost and quality in the automotive sector, and technology in one aerospace ® rm. 4. Design Centered Model Many companies have realised that the cost of change at each sequential stage proved to be very expensive, and it became increasingly apparent that more life-cycle consideration was required at the crucial design stage. Hence, a whole set of tools were developed in order to facilitate this [13]. These tools were intended primarily for the design function to take account of downstream activities when developing the product. In design centered product de® nition, the design methodology dictates that there is a higher level of design analysis required at the front end of the process (Fig. 3). This does not necessarily involve the participation of members of other departments, but consideration of their requirements is embedded in the activities within detail design. Hence, downstream design changes are minimized. The prototyping process here still takes place after the detail design has been completed and, overall, the process is still predominantly sequential; but there is a higher level of con® dence in the design information, which is still batched and passed to the next stage of the process. The central piece of information is the original detailed design which may be in the form of 2D/3D computer-aided design (CAD) models and remains so throughout the development cycle, acting as the master to which all processes have to comply. The required tools and technologies here are centered around analysis tools (computational and analytical) such as ® nite element analysis (FEA), design for manufacture

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FIG. 3. The design centered model.

(DFM), design for assembly (DFA), design for environment (DFE), life-cycle costing (LCC), etc. [13]. The centrally controlled product data is an ideal form of controlling design release issues which is easily facilitated by state of the art CAD/computer-aided manufacturing. The change control process is the same as the sequential model, in that the master model requires modi® cation to enable engineering change to occur. The premise of design centered product de® nition is that at each stage, risk is minimised before release. The organisational construct still does not require departmental integration, but a greater understanding of downstream processes is necessary in the design stage. This information is normally captured in the above-mentioned analysis tools. Often, this is combined by a `lightweight’ project coordinator [12] who acts as a liaison between the functional departments. The design centered approach can be observed in most Western-style engineering companies, particularly aerospace, where life-cycle analysis has traditionally been a requirement by the original contractor. The Western culture and education systems tend to support and be geared towards the sequential and design centered models of product de® nition. The driving forces within companies that employed the design centered model were predominantly based on quality and cost of development. In the automotive industry, General Motors applied the design centered model to radically improve its product introduction process. This initially started with just the application of DFM concepts and broadened out to include tools such as design for sheet metal, product and process failure mode analysis, dimensional variance analysis, benchmarking, Taguchi, design of experiments (DOE) methodology, design for injection moulding, etc. [14]. This is shown in Fig. 4. A similar approach is pursued by a number of other European automotive manufacturers.

5. Concurrent De® nition The design centered product de® nition has brought about many improvements in cost reduction through the development cycle by introducing more robust designs. However, the continuing drive to reduce development lead times and the need for more complex

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FIG. 4. Integrating DFM into the vehicle development process [14]. products made the task of accurate modeling of all the downstream considerations increasingly more diý cult with the currently available technologies. Product and process complexity have tended to increase over the period since the Second World War. This is combined with the demand for shorter development lead times, as is demonstrated in Fig. 5 for the electrical industry and in Fig. 6 for the automotive industry. Hence, a greater involvement of downstream activities was necessary to bring in all speci® c expertise to the design stage. This initiated the development of concurrent product de® nition. The process required for concurrent de® nition is characterized by the overlapping of design and the planning of the process development as shown in Fig. 7. Here, each phase (stage) of development has a gate attached, which has all the

FIG. 5. Product development time versus product lifetime in the electrical industry [15].

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FIG. 6. The relationship between the increase of product complexity and the reduction in time to market in the auto industry based on WMG research.

FIG. 7. The concurrent de® nition model. downstream activities represented in order to allow the continuation of the master design. Because of the greater involvement of downstream activities, sub-units of data can be released to facilitate greater concurrency and, hence, earlier start of prototype testing and production preparation. Information exchange within concurrent de® nition is facilitated through multi-functional teams, where the information exchange is more informal and exhibits greater intensity at the overlapping stages, as illustrated in Fig. 7. The main driving forces within companies that employ the concurrent de® nition model are predominantly engineering quality and lead-time based, with time to market as one of the top measures of performance cited by company executives and NPI staþ . Although DFX tools can be used in this approach, they are not essential as the expertise of the downstream activities is present in the multi-functional team responsible for allowing the project to proceed at the gate reviews. The product de® nition is, therefore, more concurrent in this approach than in the previous models. The premise of this model is not purely on design analysis but relies on the expertise contained within the project team. However, the use of integration tools such as STEP [16]

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FIG. 8. Design change within a stage gate system. enable greater concurrency, not only within the organisation, but also with the supply chain. The start of prototyping activity within the concurrent de® nition model occurs much earlier and overlaps with productionisation (manufacturing of production tools), initiating changes not only in product design but also in manufacturing process design. The nature of the change process becomes more ambiguous within concurrent de® nition, with higher levels of partial information exchange between functional activities. The de® nition of the stage gate phases allows for many iterations and design changes to take place within each phase. In fact, it also requires a greater number of them in the up-front activities. Changes that require cross-stage modi® cations require a greater degree of control and clearance authority, thereby bringing more discipline within the whole process. This is shown in Fig. 8 [17]. At the end of each phase, the master model is revised and used as the basis for further steps within the process. A combination of integration tools and CAD acts as the central database, containing the master, which is released following every phase review. However, within the phase, the information has a dynamic nature and is matured before every review and subsequent release [18]. The necessity for cross-functional teams requires a matrix style of organisation. Cross-functional team members require project management skills and process knowledge as well as their functional expertise. More technical decisions need to be made within the team and, hence, the functional managers are less involved in the day-today problem solving. The leadership of these teams is normally characterized by `heavyweight’ project management [12], where the project manager controls the crossfunctional resources involved with the project. Overall organisational structures have also got to be focused towards the team approach with fewer layers of management and the decision-making responsibility shifted to the project team. An example of this can be seen in the introduction of stage gates within automotive body development such as the work carried out at Rover Body and Pressings [6, 19, 20]. Here, after the tool design was completed, the information was ® xed and deemed unchangeable until subsequent manufacturing processes had been taken through their maturation stages. This manifested itself in the process documentation identi® ed by three engineering stages denoted by E1, E2 and E3, followed by the tool manufacturing processes denoted by M1, M2 and M3, and ® nally tool testing denoted by T1, T2 and T3 [21] (Fig. 9).

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FIG. 9. Rover body and pressings concurrent de® nition system.

A similar approach was developed to support the reduction of lead times within an aerospace system supplier. This involved the development of a staged data release mechanism within a higher level stage gate system. This was coupled by a change in the organisation to introduce dedicated multi-functional teams with decision-making power [22].

6. The Dynamic Model The introduction of a stage gate system allows the functions to have in¯ uence upon the gates and, essentially, the downstream processes, exerting a veto power upon the phase review. Although this has proved productive to improve lead time and the quality of the design that passes through the decision gates, many changes were initiated at the gates rather than earlier. This necessitated many iterations within the preceding stages. The pro® le of ability to in¯ uence the engineering decisions, however, diminishes over time within each stage. Hence, a further development of the concurrent de® nition system was to introduce a much more intensive level of communication present from the start of every product development project. This allowed a greater and a more timely in¯ uence of the design activities. The process therefore becomes much more concurrent as all activities start at the same time. This is demonstrated in Fig. 10. Information exchange is far more intensive and informal in its nature under the dynamic product de® nition model. The activity of prototyping may be prolonged in the dynamic de® nition model and, in fact, in one organisation showed an increase in the number of prototypes. But, in the overall scheme of NPI, a reduction in lead-time and costs is achieved. The main driving forces within companies that employ the dynamic de® nition model are time based, and the MOPs employed within these organisations are more holistic and also include the pro® le of engineering changes. In order to enable the intensive exchange of information, a greater degree of integration is required, where all the functional tools and techniques need the ability to seamlessly exchange engineering data. The data is ® nalised at the review point. This becomes the master model for the next phase of the development cycle. The form which the information may take is dependent on the phase and the easiest methods which can access and process it, as illustrated in Fig. 11.

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FIG. 10. The dynamic model of design de® nition.

FIG. 11. Example of Japanese automotive dynamic design de® nition. Although the currently available IT enablers, such as electronic product de® nition, product data management, etc. prove very useful for the storage and transfer of information, they are not a pre-requisite for the dynamic de® nition model. The Japanese automotive makers use a very simple system to control the storage and release of information. As long as the information is accessible to the next phase of the product design process, this will satisfy the dynamic product de® nition model. The radically diþ erent dynamic de® nition model requires a very simple change process, which is controlled by the project team both at the product and process de® nition levels. Hence, the project team requires not only the technical skills, but also business and project management skills to enable them to make the required decisions based on a consensus balance of time, quality and cost parameters. If the decisions are not taken at the working level, the technical risks will outweigh the bene® ts gained from this dynamic de® nition model [23]. In order to be able to operate such a system, a fully dedicated multi-functional project team with high levels of technical and business expertise is required to be empowered at the working level. This can only be possible in a very ¯ at organisation model. For example, Nissan is said to operate four levels of management worldwide, where plant managers will only be promoted to their position after having gone through

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FIG. 12. The PDCA cycle. at least one product development programme. Often the Japanese automotive makers tend to exhibit a very simple process model based on Demming’ s PDCA cycle [24] as shown in Fig. 12. 7. Results The four identi® ed models of design de® nition were categorised against the main parameters as de® ned in Section 2. The type of product introduction process adopted by a company is dependent upon the levels of risk involved, which is determined by the product strategy of a given company. Breakthrough projects are seen to exhibit greater levels of technical risk than incremental innovation projects. The level of risk (both technical and commercial) is therefore categorised according to incremental or breakthrough projects. A summary of the main elements of each model is presented in Table I. TABLE I. Comparison of the identi® ed models

Project risk level: incremental Project risk level: breakthrough Top NPI driver Time Cost Design quality

Sequential model

Design centered model

Concurrent de® nition model

Dynamic de® nition model

Low Low Cost/quality Slow High Low

Low Medium Cost/quality Medium Medium High

Low High Quality/time Medium Medium/low Medium

Low High Time Fast Low High

Time, critical path from project launch to volume production; cost, measured in terms of project costs throughout the process; quality of design, measured in terms of cost of engineering changes and also the stage at which change was necessitated.

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Sequential product de® nition exhibits low levels of risk in both incremental and breakthrough products, as each stage is completed before hand-over to the next. However, time, cost and design quality are adversely aþ ected in this model. The design centered product de® nition model addresses the design quality issue by up-front analysis in order to reduce the downstream cost and time. However, the breakthrough products may still exhibit higher levels of risk in comparison with the sequential model when on-line new product and process technologies need to be matured. In concurrent models of product de® nition, where stages overlap, costs are minimised by team analysis of technical risk. This model, however, may not be suitable for breakthrough products as the level of company knowledge may be low. Hence, the risks are high for breakthrough products. But in incremental innovation, the speed of NPI is increased. The design quality measures are observed to be of medium level as the project team task is to manage the speedy introduction of the product. In incremental innovation products, the quality of the product may be assured through high levels of company knowledge. The dynamic model also exhibits high levels of risk in breakthrough innovation. But the design quality increases as the team is fully committed and works concurrently. Hence, the three major external measures of performance of time, cost and quality are concurrently improved by local exchange of technical information where design freeze occurs very much closer to product launch, and is matured with respect to customer requirements rather than the original design. 8. Conclusions Four distinct models of product design de® nition are identi® ed and compared in terms of NPI drivers, MOPs, risk, time, cost and quality; namely sequential, design centered, concurrent de® nition and dynamic de® nition: Both the concurrent de® nition and dynamic product de® nition models are observed to exhibit CE processes. Sequential and design centered product de® nition models are observed to be prevalent in sequential processes. The dynamic de® nition model exhibits a radically diþ erent model from the other three, where the design de® nition changes and matures during the process. However, this is only observed in Japanese companies. REFERENCES [1] COOPER, R.G. (1995) Developing new products on time, in time, Research and Technology Management Journal, 38, pp. 49± 57. [2] WILDING, R.D. & YAZDANI, B. (1997) Concurrent engineering in the supply chain, Logistics focusÐ The Journal of the Institute of Logistics, 5, pp. 16± 22. [3] YAZDANI, B. (1996) Demysti® cation of concurrent engineering, Proceedings of the Twelfth International Conference on CAD/CAM Robotics and Factories of the Future, London, August, pp. 981± 987. [4] COOPER, R.G. (1993) Winning at New Products. Accelerating the process from idea to launch (Wokingham, Addison Wesley). [5] COOPER, R.G. & K LEINSCHMIDT, E.J. (1996) Winning businesses in product development: the critical success factors, Research and Technology Management Journal, 39, pp. 18± 38.

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