An engineering process that creates a design for an artefact, defined by Taylor (1959) as engineering design, is the process of applying various techniques and scientific principles to the purpose of defining a device, a process, or a system in sufficient detail to permit its physical realization. The pioneering work of Hubka & Eder (1982, 1988) on the theory of engineering design and technical systems has structured the way designers today create products.
Design processes at the early stages of industrialization initiated from a need or a problem and resulted in artefacts that were strictly made as “task to be done” type of solutions.
Today, examining the products designed decades ago, it is obvious that during the design process, little attention was placed on anything other than a product’s functional requirements. Later, more systematic design processes were required as the design tasks
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became more demanding in their complexity and more designers were involved within the same design task. The development of systematic design processes was a natural continuation, as were the development of manufacturing systems.
The engineering processes originate from the need to develop a new solution. As technology development has brought its impacts to engineering, the business environment has also changed the scope of engineering management. Nobelius (2004) has presented a review of R&D management generations, starting from the 1950s with (i) technology push, which turned to (ii) market pull in the 1960s, and expanded to (iii) portfolio management in the 1970s. Rapid technology development in the 1980s created a need for (iv) cross- functional teams and disciplinary integration. Globalization and subcontracting created the need for (v) networking in the mid-1990s, which continued with (vi) open innovation environments in the middle of this decade.
The type of product development project obviously impacts on what kind of design process best suits a purpose. Thus, the study identifies different product development projects and classifies them according to their results. Ullrich & Eppinger (2003) introduced eight initiation modes of product development variants and three different processes which are presented below [Table 4.1].
Table 4.1 Variants of the generic product development process, their applicability and distinct features during execution. Adopted from Ulrich & Eppinger (2003).
Based on these variants, three different development process descriptions have been presented [Figure 4.1], where the main differences between the detail design, testing and refinement phases are acknowledged (Ulrich & Eppinger 2003).
33 Figure 4.1 Three flow charts for product development processes: A) Generic, B) Spiral, C) Complex Systems. Main differentiation during the detail design and testing phases. Adopted from Ulrich & Eppinger (2003).
The development task involves a wider approach and the development process for new product development has been studied by various authors. In addition, generic product development models provide alternative approaches to different product environments.
In the early 1960’s Nadler (1963) presented his approach on work design. He defined work design as Systematic investigation of contemplated and present work systems to formulate, through an ideal system concept the easiest and most effective systems and methods for achieving necessary functions. Even though he mentioned in the preface, that the book is experimental, the philosophy establishes the objectives for work design and clarifies the areas in which the objectives are applicable and determines how objectives are to be reached. The work design is a procedure for designing an answer to any type of situation and consists of ten steps, namely:
• Function determination.
• Ideal system development.
• Information gathering.
• Alternative system suggestions.
• Selection of the feasible solution.
• Formulate the work system.
• Review the work system design.
• Install the work systems and methods.
• Performance criteria established.
The presented steps are familiar to later design processes presented by some groups or individual experts. The initial development of Design Science started in Prague 1967 at a series of international conferences, in particular at the first International Conference on Engineering Design held in Rome 1981.
Systematic design processes divide design tasks into phases with defined inputs and outputs. One of the best known design process descriptions, greatly associated with the research of Pahl & Beitz (1996) is VDI 2221 (1993), which divides the product design process into seven stages resulting in specification, function structures, principle solutions,
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module structures, preliminary layouts, definitive layouts and product documents [Figure 4.2].
Figure 4.2 Product development process, stages and main results. Adopted from VDI 2221 (1993).
The VDI-process has a structured task separation and flows from abstract to concrete, thus enabling iterations between previous and latter stages that are typical of product development when uncertainties or constraints prevent linear progress. In this process, concept development is based on changing and varying the functional structure to enable the exploration of different solutions.
The definition of design as mapping between what to achieve and how to do it has led Suh (2001) to separate the engineering environment into four domains; customer, functional, physical and process. Mapping between these domains during design reveals function to be the definitive driver. Within multi-functional systems, as industrial products tend to be, the design process progresses towards breaking down the system into functions, in which finally design parameters with constraints can satisfy the functional requirements [Figure 4.3].
Figure 4.3 Multi-functional requirement design process steps to reach robust design by decomposition to fulfil independence axiom of one functional requirement.
Adopted from Suh (2001).
35 The principle of robust design here leads to a reductive process, in which the function is decomposed to the simplest level, and where the different requirements can be separated and shown to be independent of each other.
The nature of a design situation between the two extremes of an existing practice and an unknown design during the conceptual stage was acknowledged by Pugh (1996) resulting in the definitions of dynamic and static designs. The dynamic refers to the application of a new product development, in which concept development follows the specification, as opposed to static development where the conceptual decision is already taken [Figure 4.4].
Figure 4.4 Design activity model examples for dynamic (ship design) and static (car design) concepts. Adopted from Pugh (1991).
With the total design product model, with reference to ship and car design, Pugh (1996) also showed that a product consists of different technologies and systems which cannot be developed separately. In his model, the stages where different systems are defined and a synthesis and decisions made vary depending on the type of concept. However, this will be further discussed while studying the core problem of this thesis in more detail with mechatronic products and incremental development.