Method and implementation
The method and implementation chapter presents our research design, including a description of the case study, the used techniques for data collection, how the data has been analyzed, as well as the quality of our research.
The work started officially in January 2016 with a pre-study including a literature review to provide a deeper knowledge in the research area of assembly simulation. Based on the pre-study, three research questions were created and formed.
To answer the first and second research questions, What are the limitations of using assembly simulation tools? and When can additive manufacturing be a complement to assembly simulation?, a literature review and a case study were performed. This was done in order to understand the limitations with assembly simulations and the possibilities with AM as a complement. In parallel with the literature review the case study was carried out to gather empirical data regarding the use of simulations and the problems related to this in a real scenario. The reason for choosing this approach was to gather and compare both theoretical data and empirical data from two different perspectives (Williamson, 2002).
The case study included semi structured interviews, observations, and a document study. The data collection techniques covered areas regarding experiences with assembly simulations and other techniques to assess assembly feasibility. The output and results from the first and second research questions formed a basis for the third research question, How can the decisions be supported by an AM applicability framework?
The findings from the literature review and the case study were combined and analyzed and provided the base for the results and conclusions. Figure 8 outlines the included segments during the whole study.
This section will describe how the research was designed, which methods were used and why they were chosen. In principle, two methods are utilized; a case study complemented with a literature review.
A case study is to investigate a contemporary phenomenon in its natural setting by using multiple sources as data collection (Williamson, 2002). Yin (2014) argues that the more the research question tries to explain a current situation, the more relevant a case study is. In our case, it is essential to explain how well the assembly simulation tools work and if additive manufacturing techniques can be utilized. Also, this method is useful when the research questions demand an in-depth investigation, e.g. understanding of a complex manufacturing system.
A prerequisite for a case study is that the researcher has access to a significant amount of data (Yin, 2014). This data usually resides in the three different categories of sources, i.e. interviews, documents and records, and field observations. The case company made relevant employees available for interviews, both employees working with simulation and manufacturing in general, as well as managers at the manufacturing department. Observations were performed in the actual production environment with the intention to identify problem areas in the assembly of the product. The researchers were also given access to relevant share point data regarding product design and CAD drawings.
In our research, a single case study was performed at one automotive company based on the contextual environment and the units of analysis. The choice of case company was based on the use of virtual tools in assembly system design and manufacturing. Volvo Cars was therefore selected, due to the exclusive use of virtual tools in assembly system design. The case, product development projects on the SPA-platform, is an embedded one with two units of analysis. The first unit is the limitations of assembly simulations and the second one the possibilities of using additive manufacturing (Yin, 2014). Case boundaries for this study are chosen so as to be more representative of the new Scalable Product Architecture (SPA) platform for Volvo vehicles, which all new Volvo models are based on. No specific project was selected, due to the similarities the SPA based vehicles have. SPA vehicles are today built in the Torslanda plant and this is also where the cased study is performed.
The case study first aims at answering the question if simulations of the manufacturing assembly system exhibit any limitations. If not, simulations can be assumed to be reliable enough to ensure a flawless assembly. On the other hand, if deviations between simulations and the actual assembly are detected, it should be investigated if AM could work as a complement to simulation. In order to investigate if AM is a suitable solution a number of criteria for decision support should be identified.
Literature reviews play an important role in research; it provides the researcher with a context and a background, which is crucial for the understanding and the result (Williamson, 2002). As a first step, in the early phases of this study, a literature review was conducted to understand the background and the current use of AM in the industry, which was important to obtain a deeper understanding and context of AM. The review was also needed to be able to formulate the research questions and the aim of the thesis. Assembly simulations in engineering have also been investigated in the current literature to understand and get a picture of the research in the area, as well as a deeper knowledge of the assembly simulation tools and their limitations.
An extended literature review was performed in the area of AM and assembly simulation. The sources for the literature review were mainly academic journal articles, which are the most useful type of source in a literature review (Lewis et al., 2012). Still, some conference proceedings and books have been investigated during the review. Textbooks have only been used to get a background and knowledge about the experts in the area (Lewis et al., 2012). The databases Scopus, Google Scholar and Primo (Jönköping University Library) were used to find journal papers and conference articles. The document types in the search have been limited to journal articles in the area of engineering; e.g. biochemistry has been excluded even though some research around 3D-printing of biological parts have been made but is not deemed relevant for our purposes.
During the literature review, different search terms and keywords were used in order to find relevant content. Since researchers use various terms for the same technology and tools, the combination of the search terms and key words had to be arranged structurally. For example, AM has been developed a lot since the first journal published an article in the area, and nowadays the term 3D-printing is commonly used to describe the same technology.
To find relevant articles to answer the research questions, the following terms were used:
Simulation AND verification AND additive manufacturing OR 3D-printing OR rapid prototyping.
Additive manufacturing OR 3D-Printing OR rapid prototyping
Path Planning AND Simulation
The search was aimed at ‘keywords’, ‘titles’, and ‘abstracts’ to obtain an overview of the areas.
Because of the chosen research design, several methodology instruments were used. These instruments additionally contributed to triangulating the data and strengthening the validity of results (Yin, 2013). Williamson (2002) argues that different data sources are appropriate for case studies. Therefore, interviews, observations, and document studies have been chosen for this thesis.
Interviews are one of the most commonly used data collection methods in case studies and typically collects qualitative data. The advantage of interviews is for example a high response rate compared to other methods (Williamson, 2002). The participants for the interviews were selected to enable reaching our aim and get our research questions answered. The respondents included simulation engineers, project managers and production system developers. The aim of the interviews was twofold. First to gain knowledge of areas where they experienced that the simulation was not enough and incomplete. Second, what possible usage of additive manufacturing could be found. In addition, some general information about their project processes was also included in the interviews. To get exhaustive and complete answers, semi structured interviews were conducted in this study. The semi structured interviews allowed the researchers to ask follow-up questions as a complement to the pre-determined list of questions. In this way, the possibilities to come up with more relevant questions during the interview would be beneficial for the study (Williamson, 2002).
The outline of the conducted interviews is presented in table 3. All interview questions are shown in appendix 1.
Observations have been used in this study to give the researchers a better picture of the complexity of assembling a car, and the problems associated with this. The observations were also used to get a picture and an understanding of the production system design at the case company in its natural setting (Williamson, 2002). The first observation was a guided tour at the assembly line of the new SPA-platform and the researchers had the possibility to ask questions to both the assembly workers as well as the tour guide. During the observation, the researchers identified various problems related to research question one. Parts and sub -systems details included in the car were also identified during the observations, to see these parts being assembled in real, and not only in a CAD environment, which is possible through observations (Williamson, 2002).
The second observation was carried out in the prototype workshop with 3D-printers and the manufacture of parts. Also the after-treatment of these parts was observed to understand how the finishing touch was executed. These observations provided a better context to be able to answer research question two. The observations made it possible to analyze and understand a certain problem in its natural setting (Williamson, 2002).
By studying the CAD files of the SPA-platform, the researchers gained understanding of the specific setting or policies that were needed for our study. The documents provided very useful information about the platform and the ingoing components and gave insights in the organization (Williamson, 2002). Advantages with document studies are that the researchers get a broad coverage, an extended time span, stable environment with the possibilities to repetitions, and in an unobtrusive nature, which means it required no involved participants from the company (Tellis, 1997).
The documents were gathered from the main visualization PLM software named Teamcenter. This program consists of all the information about the various car models, including detailed CAD drawings of every part that assemble the car. The CAD files and the visualization of the cars brought us information about which parts of the car are prone to cause problems in the assembly by for instance being positioned in a complex setting. In addition, the areas containing numerous cables and wires are important, as these constitute a major production challenge.
Furthermore, the study of the assembly simulation software provided information of situations where simulation was not enough and support was needed.
The data analysis for this research was mainly divided into four steps. First, the data from the observations of the assembly lines and the prototype workshop was analyzed and summarized. The data from the observations was divided into different problem areas and was later used as a support for the document study where parts and sub-part were analyzed in the visualization software. The data from the observations and document study were then combined to find patterns regarding complex assembly operations and was then connected to the reality from the observations. This was then used as a support during the interviews.
The second step was the analysis of the data from the interviews. Here, the researchers transcribed the data from the taped interviews and complementing it with the notes that were taken. This made it easier to summarize and analyze. After this, familiarization with the data was necessary in order to be able to make different categorizations. There were two main categories of data, namely simulation within product development as well as simulation within production development, the latter one related to the thesis units of analysis. For each of these two categories, two groups of respondents, simulation engineers and project managers, were included. Once the data was structured and accessible to analyze, relationships between the answers were identified and categorized into two problem areas; compatibility and ergonomics.
The third step was the literature review and followed the same process as the other data collection techniques, the first steps being familiarization and categorization of the gathered data. The aim of the literature review was to get a good foundation of knowledge within the subjects of assembly simulation and additive manufacturing to build the theoretical background as outlined in chapter two as well as the connection with the empirical data in the decisions support matrix. This required an extended review with focus on only gathering useful data and trying to categorize it in such a way it would be easier to complement the case study and reaching the goal of the study.
The last step in the data analysis were the combination of the data from the literature study and the interviews which created the foundation for the decision support matrix presented in chapter 4, where the empirical data from the interviews are combined and summarized with the findings from the literature review.
The value of a research study is to a large extent relying on the quality of the data and that no biases are contaminating the sources. In principle, the research and the quality of the project and its findings are judged on two criteria: validity and reliability (Williamson, 2002). The former is about measuring accuracy and what the study sets out to measure. The latter, reliability, is whether the same results and findings are obtained in repetitive research under the same circumstances.
Validity and reliability
For this study multiple data collection techniques have been used to reach as high validity as possible. The description of the methods used in this study, described earlier in chapter 3, makes it possible for other researchers to repeat the study again under the same circumstances. The description of how the interviews, observations and literature review was performed in this study will ensure the reliability, since it allows others to repeat the study with the same results (Williamson, 2002). The use of more than two data collection techniques in the case study made it possible to reach triangulation. The advantage of triangulation is that the gathered data are more likely to be reliable if it’s gathered by more than one method (Williamson, 2002). Furthermore, the comparison of the empirical data and the literature review will ensure the internal validity of the study, which is presented in chapter 4.
1.2 PROBLEM DESCRIPTION
1.3 PURPOSE AND RESEARCH QUESTIONS
2 Theoretical background
2.1 DESIGN FOR MANUFACTURING AND ASSEMBLY
2.2 DESIGN FOR ADDITIVE MANUFACTURING
2.3 ASSEMBLY SIMULATION SOFTWARE TOOLS
2.4 ADDITIVE MANUFACTURING
2.5 THEORETICAL FRAMEWORK
3 Method and implementation
3.1 RESEARCH PROCESS
3.2 RESEARCH METHODS
3.3 DATA COLLECTION
3.4 DATA ANALYSIS
3.5 RESEARCH QUALITY
4 Findings and analysis
4.1 CASE COMPANY DESCRIPTION
4.2 LIMITATIONS WITH ASSEMBLY SIMULATION
4.3 ADDITIVE MANUFACTURING POSSIBILITIES FOR ASSEMBLY ASSESSMENT
4.4 AM TECHNOLOGY LIMITATIONS
4.5 FRAMEWORK FOR WHEN UTILIZING AM
5.1 DISCUSSION OF METHODS
5.2 DISCUSSION OF FINDINGS
5.3 LIMITATIONS OF THE RESEARCH
5.4 IMPLICATIONS OF THE RESEARCH
6 Conclusion and future research
6.2 FUTURE RESEARCH
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