Method and Implementation
In this chapter, a research design process is presented where the reader will get an overview of the work that has been done in order to collect information and be able to answer the research questions. The methods and data collection techniques that have been used are further explained. A description of the data analysis, the validity and reliability of the research is as well presented.
Research Study Process
The thesis work started first in the middle of July 2015 with a pre-study of documents review that was offered from the case company to get a wider overview about their problems with the output variation. Then a combination between the pre-study and a literature review were made to formulate two research questions that aims to finding solutions for minimizing output variations within this research field.
Those formulated research questions were: RQ1: What problems can be identified that affect the process output variability when dealing with mass customized production? and RQ2: how can those problems be reduced to stabilise the process output?
In order to answer these research questions a literature study was carried out in parallel with a multiple case study. The aim of this study was to investigate how to minimize output variations in mass customized production within assembly lines.
There were different data collection techniques that were used when collected data in the case company, such as observations, document study and interviews. According to Williamson (2002) it is appropriate to use several data sources in a case study. The use of those data collection techniques was as well essential for the research because of the chosen research design. This enabled the data triangulation in the research which strengthens the validity of the findings (Williamson, 2002; Yin, 2014). Figure 4 below shows the entire process of this study.
After conducting the literature review and the case study, the data collected from these two methods were analysed.
The main research methods used in this study are presented here.
The researchers had chosen literature review as the first method to use when starting the research process. The focus was on finding relevant books and scientific articles that have been peer-reviewed to build an understanding background of the existing theories in the thesis area. This method was very important because it provided the knowledge of the area and supported the researchers to formulate the research questions.
Before starting the search, a list of keywords and search terms below was created to find relevant contents to the research.
Mass customization challenges, customized production, high variety in production, production variability, customization challenges.
Process output variation, output variability, Mura, Mura in production, output variability within customized production.
The sources of the literature review were mainly conducted through using the database Primo, Scopus and Google Scholar. When the search was conducted, the focus was on accessing only scientific articles between 2000 and 2016. To not exclude articles published before 200o that might contain useful information, the researchers did as well a search for articles that were published from 1980 to 2016.
When the search was conducted, the keywords were used in the advanced search as titles, keywords and in abstracts. Beside that the snowballing technique was used, which means through the bibliography of the article other relevant articles were found. This helped both in creating a fundamental base of the theoretical background and contributed to more keyword. The following new keywords and terms that were used in the search are from the key article and the other relevant articles.
Balancing challenges, material supply challenges, mass customization balancing problems, balancing and material supply problems.
Logistic constrains in customized production, material supply challenges, internal logistic, standardise work, lean manufacturing.
After conducting the last search with the keywords above the researchers had the theories needed to create the theoretical background for the research.
A case study is about studying a real-life phenomenon in its natural setting and it can be carried out in form of a depth study of different activities for collecting reliable and valid findings. A case study can be performed as a single or multiple cases (Williamson, 2002; Yin, 2014). In this research, the authors had chosen to work with a multiple case study in a white-goods company during a period of three months (January to March 2016). There were two reasons behind this choice. The first one was because the case company is a white goods company and the researchers wanted to extend the research to other industries then the automotive industry. The second reason was that both researcher had had done an internship of three months (July to September 2015) in two different assembly lines in the case company. Therefore, the multiple case study was performed in those two production lines because of the insight that the researchers gained during the internship. Those two production lines are called in this research as line A and line B.
The aim of using this multiple case study was that the findings from the cases will provide a wider knowledge for the researchers to understand what problems affect the output variation and which applicable solutions could be used to minimize those output variations. This helps in both answering RQ1&2. This as well provided the possibility of comparing between the findings from both lines.
The data collection techniques are presented here explaining the procedure used and the preparation done in order to collect accurate data for the study.
Several participating observations have been conducted during a period of four months. The participating observations aimed to give an understanding of the nature settings of both production lines, the assembly processes, and the material handling and delivering to the lines (Williamson, 2002).
The first observation was about study the performed assembly in two production lines; line A and line B. The second observation was focused on the integrated effects of internal logistics to the production.
In the first participating observations, the researchers studied the assembly steps, visualization in the working stations, product quality and the production output for three months on both production lines. The collected data were compiled in a table and concerned the number of operators, the planned production, products variants and NRFT. This table were updated each day with the information above in order to see the deviations between on day and another. During this time, the researchers got opportunities to see what problems usually occurred in the line and based on that, a frequency list of problems was clarified which supported researchers to answered RQ1. When making observation in the working stations, the researchers even recorded videos when operators were performing their job in each working station. By studying those videos, the researchers could identify non- value adding- and value adding activities of operators. Different wastes and root causes that affect productivity were identified. Based on those time study measurements, the researchers could answer RQ1.
The second participating observation was to study the internal milk-run of deliver raw material from warehouse to assembly stations for one month. This observation was focusing to identify the frequency of internal material supplying and pick-up between warehouse and the case assembly lines. The researchers followed and observed two warehouse operators who had responsible for delivering components from the warehouse to the production line day by day for one month.
The collected data were the time that needed for the warehouse operators to pick up material from warehouse and the train delivery routes when delivering components to the production line. The different stop-points for the train were recorded and as well the time for each train delivery. This observation was important because by studying the delivery routes and the delivery time, the researcher could find a related problem between internal material delivery and several stops in production line. This observation helped to answer RQ1 and supported to find new solutions for RQ2.
Conversation During Participating Observations
The conversations and meeting were carried out with the process engineers, the line supervisor, and the line operators. The conversations treated current problems in the lines or some thoughts and ideas of making new improvements. Because of that reason, no list of questions was created. The aim of those conversations was to increase the authors’ knowledge about the assembled products in both lines and currents problems that both line was facing. Besides that, it is important to understand more about the existing line balancing and the material delivery to the lines. Those conversations were as well used towards understanding for example why did the lines stop, what was the problem and when and where did it occur.
The concerned people who had been involved in those conversations were process engineer supervisor, process engineers, line leader and operators from both case assembly lines. An outline of the conversation area is presented in table 2.
Three different documents in the case company’s database between period of 2015 and in the beginning of 2016 had been reviewed to get a deeper knowledge about the research scope, the output variation in the production lines and to compare with the data from the participating observations in order to later compile the data and present the final findings for RQ1&2, see table 3.
The first documents were NRFT (Not Right First Time) and present problems with the products quality that had occurred in the production lines. This data was important to be able to categorize the problems that have occurred in the production line. It helps as well in defining the frequency of similar problems in the production lines.
The second document review was the efficiency documents for both Line A and Line B. Those documents contained information that helps in obtaining the efficiency of the production lines. The information was the actual output for each day, the planed output, the number of operator that were present in the line and the total work hours for each day. This was relevant for the study because it gave an understanding of the variation that exists in the line from day to day.
The third conducted document review was the existing balancing of both production lines. This was important to review because when the researcher conducted the observation many different variants were produced in the same day without changing the balancing, even if the preformed work and assembly time differed in some stations. Therefore, it was essential to understand the line balancing that exist in each line to see if the balancing had an impact on the process output variability that are visible in both lines.
There are different types of interviews such as structured, semi-structured and unstructured interviews. In this study only one type had been used when collecting the qualitative data in the case study. It is called semi-structured interviews and are the most commonly used data collection technique in case studies (Williamson, 2002). The semi-structured interview was chosen to make sure that the collected data is useful and not excluding any important information. Therefore, the interview was more open and several follow-up questions were asked depending on the answers the researchers received.
One semi-structured interview was conducted with the supply chain manager from the case company on 14th of July 2016 via Skype in one hour.
An interview guide was used (appendix 1) included questions that were related to problems of material delivery to the production and different solutions for the current internal milk run system. The supply chain manager answered the questions based on his own knowledge, experiences and personal perspectives. Therefore, depended on the answers the authors carried out a deeper and further discussion about the topic with the interviewee. The interview contributed to relevant data when it came to logistics problems and possible solutions. This supported the researchers to answer RQ1 & 2.
Time and Motion Study
During the participating observations in both case assembly lines, the authors had collected assembly process time and movements of the operator in each working station. A time study collection sheet (appendix 2) had been created and used to support the study. The researchers used this sheet to capture every task and working element in each working station and recorded the measured time for the operators to perform his/her tasks.
The aim of doing time and motion study was to create a base information list of different value adding and non-value adding activities that happened in the production line and from that finding solution for e.g. eliminate different wastes, improve the line productivity, increase efficiency and effectiveness and lower production cost and lead time (Ortiz, 2006).
The time and motion study was helpful because the collected information was used for identifying different wastes, understanding the differentiation of standard work between operators both when it comes to standard time and the standard procedures of the assembly activities. This supported the researchers as well in the re-balancing of the lines and helped in answering RQ1 &2.
The collected data were analysed and summarized. Firstly, the data from the literature review were analysed to build the theoretical background. These data were divided in two categories as mentioned in the background. The first category was the existing problems in mass customized production. The second category is the existing solutions for minimizing the output variation through solving the joint balancing and material supply problems. Both categories from literature review were later triangulated with the data from the two studies conducted on both lines.
The first study was about observing and analysing the flow in the assembly lines, the assembly processes and the lines’ output variation. The second study was about the identification of the frequency of internal material supplying and pick-up between warehouse and the production lines. The analysis of collected data were from all observations, conversations, Semi-structured interview and document reviews. The data from observations conducted on the production lines and the internal material supplying for the lines contained data from some conversations during the participating observations. This was important because there was a need of understanding what was happening in the lines during the conducted observations to prevent losses of data because of the language barrier that the researcher faced.
The collected data from the observations was analysed and summarized in different problem areas. The summarization showed which problem areas had mostly occurred in both lines. This data was compared later with the summarisation of the document review analysis that showed similar problems as the one encountered during the observations. Out from this the problems that were most frequent on both line was defined and only by gaining a deeper understanding of the problem root causes the researcher would be able to analyse the applicability of different solutions. Therefore, the data from several conversations and the semi-structured interview were essential to fill in the gaps and get the entire picture of the problems. The notes from the conversations were already structured and categorized directly during the observations which simplified the summarization of the data. Later, the data from all the conversations, the observations, the document review, the semi-structure interview and the literature review were triangulated to understand which are the most frequent problems and the root causes of the problems.
The second study was about analysing the applicability of solutions that can stabilize the process output variation. For that the collected data from several conversations and the semi-structured interview were analysed and categorized in balancing solutions and material supply solution that the case company finds applicable in their case. The data from the literature search and the interview were triangulated to see if there were any connection between the theoretical solutions and the real-world solution suggestions that were given by the case company.
1.2 PROBLEM DESCRIPTION
1.3 PURPOSE AND RESEARCH QUESTIONS
2 Theoretical Background
2.1 LEAN MANUFACTURING
2.2 LEAN IN MASS CUSTOMIZED PRODUCTION
2.3 THE JOINT BALANCING AND MATERIAL SUPPLY PROBLEM
2.4 INTERNAL LOGISTIC
3 Method and Implementation
3.1 RESEARCH STUDY PROCESS
3.2 RESEARCH METHODS
3.3 DATA COLLECTION
3.4 RELIABILITY AND VALIDITY OF THE STUDY
4 Empirical Findings & Analysis
4.1 CASE COMPANY DESCRIPTION
4.2 PROCESS OUTPUT VARIATION PROBLEMS
4.3 SOLUTION APPLICABILITY
5 Discussion and Conclusions
5.1 DISCUSSION OF METHOD
5.2 DISCUSSION OF FINDINGS
5.3 CONCLUSIONS AND FURTHER STUDY
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