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Methodology
This chapter is highlighting the methodology that was used for this thesis. This chapter includes the strategy the problem has been approached with, and the way the problems have been dealt with.
Framework for system development
When developing a manufacturing system, a structured methodology and a plan is a key factor for achieving a satisfying result (Bellgran & Säfsten, 2008). A framework for development of manufacturing systems is presented in Bellgran and Säfsten (2008). The framework is emphasizing the need for a structured approach to the development project, since the development of manufacturing systems are quite complex. The framework is based on both empirical, as well as theoretical investigations.
The planning part of this framework is considering the pre-decisions and the organizational aspects of the development work. The task is to plan for the development project and by so make sure quality and control of the project. The design and evaluation part is including the development of the process layout of the manufacturing system. Before that, choices regarding processes and technology are done and implemented into conceptual layouts.
These are then being evaluated based on specific criteria’s of concern. Later on is the solution implemented in the reality and the production gets ramped-up (Bellgran & Säfsten, 2008).
The methodology from this framework was used at the early start of the thesis project. The structured way of working and planning level in figure 3-1 above were guiding for the entire project, and kept the project in line with the set targets. Since a structured way of working was requested, a plan for the development project was created and is presented in the next section.
Influences from the Design and Evaluate level in figure 3-1 were absorbed. This was guiding when the method of separating the conceptual and the detailed design in this project was formed. The implementation level in figure 3-1 was not considered due to the fact that the thesis project was delimited to only developing a system, not realizing it.
Scientific approach
A Master thesis is to a certain degree a research project and may include both doing academic research and applying already known science in what is referred to as applied research (Saunders & Lewis & Thornhill, 2000). Further on, the result of any research project benefits from a well arranged project plan. This plan should include the goal of the project, which is the factor that the plan should be designed according to fulfilling it. The plan should also include the methodology that is supposed to lead the project to the goal (Saunders & Lewis & Thornhill, 2000).
Since the goal of this thesis is to develop an entirely new assembly system, the project plan must be designed in order to facilitate this situation. Due to the complexity of the subject, it was required to break down the problem into smaller entities, which was done in a project plan shown below.
The plan starts with a literature review, which was supposed to guide the design process and give the necessary academic basis. The next step was to analyze how the design process was affected by its surrounding environment.
From Muther (1973) and Slack & Lewis & Johnston (2004) some implicating factors was identified as limiting factors to the design process. Therefore it was found relevant to investigate how they affect the design process.
The assembly system design was broken down into 2 smaller design processes: assembly line and logistic system design, as can be seen in figure 3-2 above. When the concepts of these 2 were developed they were combined and an assembly system design was generated. The assembly system design was a compromise between the two combined concepts in order to find the best solution possible.
The last step was to evaluate the assembly system design and reflect upon its weaknesses and strengths.
Literature review
A literature review is essential when carrying out a thesis work. It is supposed to be a framework that guides the student with her thesis work and enables her to work in a systematic and academic way. A literature review was done at an early stage of the project.
The study provided some necessary inputs to the later assembly system development. The focus of this study was set on finding practical guidelines, therefore is the previous chapter, the theoretical background, mainly presenting those literature findings that provided most practical use, rather than for an academic purpose.
This thesis is in the field of Production Systems, which in the literature is similar to the more frequently used Production and Operations Management. The literature that is included in the theoretical background chapter is thus based on that research area, together with logistics and production development. The literature used was mainly books, but also some articles were found relevant and therefore used. The literature review was essential for the outcome of the thesis and provided the necessary inputs for the assembly system design process.
Interviews and empirical observations
In order to find design inputs and the delimiting factors of the design process, it was necessary to seek the information were it was located. The following 2 paragraphs describe the way the information was gathered.
Meetings and cooperation with Aercrete Industries
Much of the information needed for the development of the assembly system was empirical, and was to be found from the employees working at Aercrete Industries. During the project, there were some briefings and discussions, which provided the necessary data that was requested.
The management at Aercrete Industries provided comments about the project and together with the supervisor at Jönköping School of Engineering, tried to steer the project towards a successful end. Since the project was faced with the fact that hardly any documentation or data was to be found stored, a close collaboration with the company was soon realized to be crucial for the outcome of the project.
Data collection
As described in the previous section, much of the data collected was empirical. Since the product was entirely new and there was no existing assembly system, the empirical data was mainly based on experience and qualified guesses by the management at Aercrete Industries. One type of data gathered was time estimations for the assembly of the product.
This data was mainly based on estimations and previous assembly of demo products. Another data collected was assembly information, which is crucial for determining the assembly order. This data is based on experience and logical thinking of assembly efficiency. Data regarding the facility was both measured and gathered through interviews. Much of this data are requests from the management at Aercrete Industries, and thus limiting the scope of design possibilities. Most of the data gathered is presented in attachments 2-5 and in chapter 4 as preconditions.
Design process
As previous described, the design process was broken down into smaller entities in order to simplify the task. The design process was split up into an initial preconditions analysis and how those preconditions affect the design process. Then the conceptual designs of the assembly line and logistic system were developed. Later on the detailed design of the assembly system was created by combining the conceptual design together. The combining task was complicated by the fact that some factors forced rework and rethinking regarding the finalization of the system design. The methodology used for the combining task was a discussion between the authors and the management at Aercrete Industires.
Assembly technology
The factors that affect the assembly process itself were investigated in order to gain an understanding of what data was needed and what design steps to use it for. The assembly technology was especially relevant for the detailed design of the assembly system, when the assembly work was supposed to be distributed out in the system.
Systematic Layout Planning
The systematic Layout Planning framework was used as a methodology to understand how to design the physical layout of a manufacturing system. It was also useful for gaining insight in what aspects to consider when making the layout. Besides, the method displayed the necessary inputs that are required to gain knowledge about in an assembly line development project. The framework was not followed as strict as it is recommended and that is due to the fact that some factors were unknown as well as the applicability was considered limited on this specific situation.
Lean production approach
Lean Production is a philosophy that should be guiding the design process. Its strong focus on liming the waste in every detail was constantly at mind during the design process and affected the decisions made during the thesis project. Similar to the Systematic Layout Planning framework was the Lean Production approach not followed strict since it is often taught as an improvement tool instead of an development tool. However, as described previous, the Lean philosophy was followed in the way the design process and surrounding factors enabled it.
Technology aids
In order to increase the visibility and help designing the assembly system, some technical aids where used during the thesis. Besides the standard office package, this following software’s where used:
AutoCAD
At an initial stage of the thesis work, the AutoCAD software was used to illustrate the facility’s dimensions and constraints. Printings from this program were also used for the block design of the assembly system.
Solidworks
Further on in the thesis work, when the detail of design increased, Solidworks was used to make a graphical representation of the results of the design. It was also used for making some of the attachment in this report. The Cad documents were also part of the presentation of the results to the project givers.
Validity & Reliability
When carrying out research, it is important to reflect upon it and question it, in order to increase the quality of the result (Williamson, 2002). In research the term validity is used to investigate whether the scientific work is valid. Golafshani (2003) states that high validity brings truth to the scientific work, and gives strength to the given conclusions and recommendations.
It exist 2 types of validity: internal and external. The internal validity is used to determine whether the research process carried out is about the intended context. The external validity is used to determine if the research results are possible to apply in other situations, or in other words is general for any situation given (Jacobsen, 2002).
If the internal validity is low, the results might be infeasible due to the fact that they are based on an incorrect basis. Another term for judging the quality of scientific work is reliability. Reliability is used to determine if the results are of good quality or if there are any factors affecting the results negative (Williamsson, 2002). The trustworthy of the results are strongly depending on the reliability of the results. Golafshani (2003) states that it is important to plan for validity and reliability at an early stage in a scientific project. Besides, value and criticize the outcome of the own scientific work is necessary for a serious researcher.
The factors in this project that that were identified as possible sources of error affecting the reliability are:
Low accuracy of the time measurements, making time estimations necessary.
Little knowledge of the assembly process of the machine, making practical experience of others important.
Little documentation regarding the machine, making estimations necessary.
The internal validity of this project was considered to be relatively high since the subject is rather focused. Since the subject is rather focused, the external validity will be low due to the fact that the result will be strongly situation adapted, or in other words fairly dedicated to the specific parameters affecting in this situation.
Table of Contents
1 Introduction
1.1 COMPANY BACKGROUND
1.2 PURPOSE AND AIMS
1.3 DELIMITS
1.4 OUTLINE
1.5 CLARIFICATION AND READING INSTRUCTIONS
2 Theoretical background
2.1 MANUFACTURING STRATEGY
2.2 PRODUCTIVITY AND PERFORMANCE
2.3 LEAN PRODUCTION
2.4 SYSTEMATIC LAYOUT PLANNING
2.5 FACILITY LAYOUT AND FLOW
2.6 PRODUCT STRUCTURE AND ARCHITECTURE
2.7 ASSEMBLY TECHNOLOGY
2.8 LOGISTIC ASPECTS OF MANUFACTURING SYSTEMS
2.9 HUMAN FACTORS AND ERGONOMICS IN MANUFACTURING SYSTEMS
2.10 QUALITY IN MANUFACTURING SYSTEMS
3 Methodology
3.1 FRAMEWORK FOR SYSTEM DEVELOPMENT
3.2 SCIENTIFIC APPROACH
3.3 LITERATURE REVIEW
3.4 INTERVIEWS AND EMPIRICAL OBSERVATIONS
3.5 DESIGN PROCESS
3.6 VALIDITY & RELIABILITY
4 Analysis of the preconditions
4.1 STRATEGIC IMPLICATIONS ON THE ASSEMBLY SYSTEM
4.2 FACILITY CONSTRAINTS AFFECTING THE MANUFACTURING SYSTEM
4.3 THE PRODUCT’S EFFECTS ON THE ASSEMBLY SYSTEM
5 Conceptual design of the assembly line
5.1 THE STARTING POSITION
5.2 THE ASSEMBLY LINE
5.3 LAYOUT PROPOSAL NUMBER 1
5.4 CONCEPTUAL LINE LAYOUT PROPOSAL NUMBER 2: THE FINAL ASSEMBLY LINE
5.5 LINE LAYOUT PROPOSAL NUMBER 3: THE SUB-ASSEMBLY SYSTEM
6 Conceptual design of the logistic system
6.1 LOADING/UNLOADING
6.2 THE OVERHEAD CRANE
6.3 INVENTORY STORAGE
6.4 MATERIAL FLOW
6.5 FEEDING THE ASSEMBLY LINE
6.6 ERGONOMIC FACTORS
7 Detailed design of the assembly system
7.1 THE PHYSICAL SHAPE AND POSITION OF THE ASSEMBLY LINE
7.2 THE PHYSICAL POSITION OF THE SUB-ASSEMBLY STATIONS
7.3 DETAILED LAYOUT OF THE LOGISTICS SYSTEM
7.4 SUMMARY OF THE FINAL ASSEMBLY SYSTEM DESIGN
8 Conclusions and discussion
8.1 RECOMMENDATIONS
8.2 REFLECTIONS AND CRITICISM OF THE THESIS
8.3 VISIONS AND CONCERNS FOR THE FUTURE
8.4 FUTURE RESEARCH OPPORTUNITIES
9 Glossary
10 References
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Design of an Assembly System at AERCRETE INDUSTRIES
