The work described in the thesis was informed by grounded theory as a research method for developing theory that is “grounded in data” systematically gathered and analysed (Urquhart et
al. 2010) with the use of spiral model as an overarching framework for the study.
The following section gives an overview of the research shown in Figure 3-3 and describes the phases of the study.
After an exploratory research stage leading to the clarification of the research motivation and objectives, the author spent over ten weeks at Renault Lyon in France (a company acquired by Volvo Group) to learn about the organisation and to understand the existing practices at Volvo Group. This first phase of the study helped addressing the first research question (RQ1). Then a second phase was initiated to capture how engineers and designers deal with margins during complex development projects. This was performed by empirical collection of data from different sources in the company and by conducting a first set of interviews (3.3.1 for more details). At the end of this phase, research question 2 (RQ2) was answered. Later, in phase 3, a case study was conducted to identify how margins can be modelled (RQ3).
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Figure 3-3 Overview of the research
3.3.1 Interviews
Twenty semi-structured interviews from between 45 minutes and two hours were carried out with employees from Volvo GTT which has been designing and building trucks for nearly 100 years. The interviews were conducted in Gothenburg site by the author and the supervision team; Professor Claudia Eckert and Professor Chris Earl between October 2013 and December 2014. Three or four interviews were held on a single day every two to three months. Each session was recorded on audio tapes and selected conversations were later transcribed for analysis. The interviews were carried out in English and were semi-structured in that there was a list of topics that the interviewers wished to cover, but the interviewees were allowed to move the discussion onto related issues if they felt that it was necessary.
The first series of interviews took place in October 2013, which focussed on chassis engineering across the product life cycle. The second set of interviews was conducted while carrying out the case study of this research and took place in December 2014. The interviewees were designers,
engineers and managers who work in different departments, with at least five years of experience within the company and industry.
At the beginning of each interview a brief introduction was made to give an overview on the project status and introduce the objectives of the session. The questioning was relatively general with each person initially asked to describe their role. As the interview progressed the questioning focused more on design process and in particular on design margins, and whether they have room for maneuver to take up new requirements. An example of the questions asked can be found in Appendix A. Practically, the questions can be grouped as follows:
– Questions on the role of the interviewee. – Questions on the main constraints
– Questions on the company structure and the structure of their products – Questions on the new product design process
– Questions on the design change
– Questions on the design of the cooling system.
– Questions on the key parameters of the cooling system.
During the discussion of design changes, the interviewees were asked if they are aware of the design margins they may have on specific parameters and if so how they deal with them. In this research two main series of interviews were carried out. The first set of interviews was conducted to figure out some of the vocabulary used around margins with the aim of getting a definition for margins which is compatible with the language used in the company. For this, ten interviews were conducted with ten employees from the Chassis department. The interviewees were selected to cover different phases of the design process and different level of detail. These interviews helped to establish an understanding of the current practice in the company.
At this stage of the study, specific research problems started to emerge. Combined with a literature review about the concepts related to design margins and the previous empirical
60 research at Volvo GTT, this led to investigation of a new method aiming to support designers and engineers, understanding, managing and communicating design margins across the product development process. This method and its potential application was investigated through a case study. A second set of interviews was planned for this purpose.
A set of follow-up interviews focused on understanding how design changes affected the margins on components during the design process. It was decided to focus on one system to get a better understanding of the concept. The cooling system team was interviewed as many of the margin issues around the cooling combine geometrical issues which are fairly intuitive with thermodynamics and fluid flow issues which are more technically complex. This study gave an understanding about the core parameters for the cooling system that the designers and engineers need to consider in the first place. It enabled an examination of how margins on key parameters are handled and helped establish how margins play a role in carrying out changes. This allowed patterns in the mapping between changes and margins to be identified.
Fourteen engineers and designers from the cooling system team were interviewed for 60 / 90 minutes. The interviewees have different positions and functions within the cooling team. At a high level, the interviewees could be split into two categories: engineers (14 interviews) and managers (6 interviews). This is illustrated in Table 3-1 by a reference code: “Eng” for engineer and “Mng” for manager. It should be noted that the managers all had extensive engineering experience either with Volvo or with other companies. Each session was recorded and the conversations were transcribed for analysis. At the beginning of each interview a brief introduction was made to give an overview on the project status and introduce the objectives of the session.
Interview Role Classification
1 Specialist in Geometry, high level view of computer tool in the