Engineering Change Management (ECM) has been studied by many academic researchers and industrial practitioners in the past decades. Researchers and practitioners investigated various engineering companies and projects in manufacturing industry (Stanev et al., 2008; Tseng et al., 2008a; Huang and Mak, 1999; Huang et al., 2003; Nichols, 1990; Gerwin, 1982; Pikosz and Malmqvist, 1998), construction industry (Chang et al., 2010; Zou and Lee, 2008; Xue et al., 2008; Kraft and Nagl, 2007; Xue et al., 2006), and software industry (Williams and Carver, 2010; Mohan et al., 2008; Park and Bae, 2011; Lam, 1998). Some characteristics of engineering change have been learnt from these investigations and critical issues within engineering change management have also been identified. Therefore, management processes/frameworks, methodologies, technical methods and tools for engineering change management have been proposed in the attempt to address these issues and tackle them with solutions from different perspectives.
2.1.1 Definitions of Engineering Change
What is engineering change exactly? In many cases, engineering change is also referred to with related terms such as engineering change request (ECR) (Helms, 2002), engineering change order (ECO) (Loch and Terwiesch, 1999; Pikosz and Malmqvist, 1998), engineering change notice (ECN) (Buckley, 1996; Ullman, 2010), request for change (RFC) (Keller, 2005) and Change Request (CR) (Lam, 1998; Crnkovic et al., 2003; Kajko-Mattsson, 1999). Although the exact meanings behind these terms may be seen slightly different in terms of the stages of the engineering change process, they represent the same essence of work in companies, and in many times people use them interchangeably. This actually reflects the fact that even if engineering change management has been researched and practiced for many years, the definition of engineering change has not had general consent. Therefore, to consolidate the background of the research topic, it is worthy of having a review of
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views and definitions of engineering change before rushing into review of methods and techniques proposed in this area.
Wright (1997) defined engineering change as modification to a component of a product before it goes into production. The definition is focused on changes on physical components of products at any stages before production which is mainly in the product design phase in the general product development process (Ulrich and Eppinger, 2004; Pahl et al., 1996).
However, some researchers have defined engineering change as modification to dimensions, fits, forms, functions, materials and so on, to product or components after the product design is released (Huang et al., 2003; Kocar and Akgunduz, 2010). In their view, engineering change has a broader scope where modifications are applied, which includes modifications not just to components but also to the whole product. At the product level, change to function is an important constitute which is one of the significant differences from Wright’s definition. Besides, they argued that engineering change occurred after the design of product was released, which included the production phase and all other phases afterwards. Obviously, Wright’s definition of engineering change focuses more on the design stage while Huang and Kocar’s definition is more about change in the manufacturing phase, which is the essential difference.
In another paper, Tseng, Kao and Huang (2008a) viewed engineering change as modifications to a component or a portion of a product for certain improvement purposes, such as adding more functions, strengthening quality, enhancing aesthetic or operational features, or improving manufacturability. Compared to the previous two definitions, their definition of engineering change is at a higher level and extends the scope that engineering change covers. They also advocated Huang and Kocar’s definitions that engineering change should happen after the product design stage or even in the production stage. A notable point made by them was that they thought engineering change was about improvement based on the current design, which included either for adding some values or for reducing costs.
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While some other researchers viewed engineering changes as changes occurring in a wider range from customer requirements to product use (Pikosz and Malmqvist, 1998; Eckert et al., 2004). In a joint proposal for Object Management Group (OMG) which is a influential international computer industry consortium, engineering change was defined as ‘a task by which companies request, implement and affect changes to products, documents, components, manufactured or purchased parts, processes, or even supplies’ (Dec et al., 1998). This definition considers engineering change not only within products but also in processes and in the supply chain.
2.1.2 Different Views on Engineering Change
A lot of research carried out in the manufacturing industry reported that engineering change has caused serious problems (Huang and Mak, 1999; Maull et al., 1992; Boznak and Decker, 1993; Kidd and Thompson, 2000). Most of the researchers found that the engineering change process was very time consuming and costly. In Huang and Mak’s survey of 100 manufacturing companies in the UK, they found that there were about 65 active engineering changes on average in each company (Huang and Mak, 1999). In another study, it was shown that companies had 220 change requests per month on average nowadays, 22% of which were manufacturing related changes (Stanev et al., 2008).
The reported figures above are echoed by evidences from other researchers. Boznak and Decker (1993) reported the annual administrative processing cost for engineering change in companies, which they investigated, ranged from US$ 3.4 million to US$ 7.7 million. Maull et al. (1992) found that engineering changes might cost companies about 10% of their annual turnover. Apart from concerns of cost for engineering change, it was also discovered that it might require an average of 40 days to discover an engineering change, 40 days to process and approve an engineering change, and 40 days to implement it (Watts, 1984).
Köhler (2008) cited some German reports about how engineering change negatively affected industry. It showed that engineering change management consumed 30 to 50 %, sometimes even up to 70 % of the capacity in product development. This was
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supported by Ehrlenspiel (2007) who found that processing changes often absorbed from 20% to over 50% of the product development capacity in the manufacturing industry.
Despite the negative effects of engineering change on product development, some research also showed that engineering change facilitated companies’ innovation and creativity. A study by the Aberdeen Group showed that the majority of changes were necessary for innovation (Brown, 2006). There are 82% of interviewed companies stating that although they were mostly concerned about increasing product revenue, engineering changes could also lead to innovation to their existing products. Conrad et al. (2007) also found that one of the reasons for engineering change was the improvement, enhancement or adaptation of a product. It was also supported by Balogun (2003) who saw engineering change as a means to facilitate knowledge generation in industry.
2.1.3 Causes of Engineering Change
By reviewing literature in engineering change management, it is noticed that people’s understanding of causes of engineering change have advanced. Research in earlier time was focused on engineering changes emerging from physical components/parts, which included changes of dimensions, materials and forms. Typically, the draft standard ISO11442-6 (1996) gave some examples of engineering change, which included change to a part because of alterations of function or production requirements, change to the application of a part, adding new parts, replacing or removing existing parts, correcting errors in a document or updating a document.
However, Pikosz and Malmqvist saw causes of engineering changes in the view of product development (Pikosz and Malmqvist, 1998), which included changes in customer specifications, faults in the interpretation of customer demands into technical requirements, difficulties in parts fabrication or assembly, weaknesses in the product identified during prototype testing, quality problems with some subsystem or component, and development for future product revisions. Obviously, their view of the causes of engineering change is from a high level of the product development
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process. Engineering changes are not just seen as modifications to physical parts but to possible changes in any stages of the product development process.
Dennis et al. (2002) viewed engineering change from a system engineering perspective. They identified that engineering change might be caused by (i) problem reports that identify bugs that must be fixed, which forms the most common source; (ii) system enhancement requests from users; (iii) events in the development of other systems; (iv) changes in underlying structure and or standards (e.g., in software development, this could be a new operating system), and (v) demands from senior management.
Eckert et al. (2004) saw engineering change in two main categories: initiated changes and emergent changes. Initiated changes are those intended by a stakeholder, while emergent change is unintended and occurs when some aspect of the system design requires changing because of errors or undesirable emerging system properties, often due to an earlier initiated change.
Conrad et al. (2007) saw the causes to engineering change at a higher level. They stated that engineering change could be triggered by (i) a change of one or more characteristics, e.g., a modification of the diameter of a shaft; (ii) a change of one or more required properties, e.g., the change of customer desires; (iii) a change of external conditions, e.g., new standards; (iv) a change of internal dependencies, e.g., the realisation of a different solution; (v) a change of relations between characteristics and properties, e.g., the use of a different formula, tool or practical experiences from the field.
While people’s views of causes of engineering change have been changing over time, the focus and the scope of research on engineering change has been widened. The initial motivation of studying ECM was to avoid engineering changes during the manufacturing process due to the adverse effects they caused. The adverse effects caused in terms of delivery time, developing cost and product quality are noticeable, but very difficult to estimate (Huang et al., 2003). Later on, people realised that engineering changes were actually inevitable. Therefore, researchers have turned to
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finding out how engineering changes went on and what kind of impacts they might cause (Clarkson et al., 2004; Kocar and Akgunduz, 2010; Ouertani, 2008). Recently, some researchers argued the benefit of engineering changes to innovation and creativity, which could enhance the competitiveness of companies. Thus some researchers have started to study engineering changes from perspectives of knowledge management and knowledge reuse (Balogun and Jenkins, 2003; Palani Rajan et al., 2005; Lee et al., 2006; Keese et al., 2009).