The Impact of Product Design and Product Development on the Production System Design

Table of content

ABSTRACT

INDEX OF FIGURES

INDEX OF TABLES

INDEX OF ABBREVIATIONS

1. INTRODUCTION
1.1 BACKGROUND AND MOTIVATION
1.2 THESIS OBJECTIVES
1.3 THESIS OUTLINE

2. THE PRODUCTION AND MANUFACTURING SYSTEM
2.1 AN INTRODUCTION TO SYSTEMS THEORY AND OBJECT-ORIENTATION
2.2 THE PRODUCTION SYSTEM
2.3 THE MANUFACTURING SYSTEM
2.3.1 DEFINITION OF A MANUFACTURING SYSTEM
2.3.2 THE ELEMENTS OF A MANUFACTURING SYSTEM
2.3.3 THE MANUFACTURING PROCESS
2.3.4 THE CHARACTERISTICS OF A MANUFACTURING SYSTEM
2.3.5 TYPES OF MANUFACTURING SYSTEM
2.3.6 THE DESIGN OF A MANUFACTURING SYSTEM
2.3.7 THE CONTROL OF MANUFACTURING SYSTEMS
2.4 LEAN PRODUCTION
2.4.1 THE TRANSITION OF THE MARKET REQUIREMENTS
2.4.2 THE PRINCIPLES OF THE TOYOTA PRODUCTION SYSTEM
2.4.2.1 The Objective
2.4.2.2 The Definition of Value and Waste
2.4.2.3 The Process
2.4.2.4 The Operation
2.4.2.5 The information flow

3. CHARACTERISTICS OF PRODUCT DEVELOPMENT
3.1 THE PRODUCT DEVELOPMENT PROCESS
3.1.1 PRODUCT DEVELOPMENT AS AN INFORMATION PROCESSING ACTIVITY
3.1.2 THE INTEGRATION OF PRODUCT DEVELOPMENT ACTIVITIES
3.1.2.2 Internal integration
3.1.2.3 External integration
3.1.2.4 The impact of integration on product development performance
3.1.3 THE DIFFERENT STEPS WITHIN PRODUCT DEVELOPMENT
3.2 THE DEGREE OF INTERNALIZATION VS. EXTERNALIZATION
3.3 DEFINING A PRODUCT DEVELOPMENT SYSTEM
3.3.1 THE DEFINITION OF A PRODUCT DEVELOPMENT SYSTEM
3.3.2 THE DESIGN OF A PRODUCT DEVELOPMENT SYSTEM
3.3.3 PRODUCT DEVELOPMENT AS A PART OF LEAN PRODUCTION
3.4 PRODUCT ARCHITECTURE AND PLATFORMS
3.4.1 PRODUCT DESIGN
3.4.2 IMPLICATIONS OF THE PRODUCT ARCHITECTURE
3.4.3 PRODUCT PLATFORMS
3.4.4 PART DESIGN
3.5 CONCLUSIONS FOR INTEGRATING PRODUCT DESIGN AND PRODUCT DEVELOPMENT INTO THE DESIGN OF AN MANUFACTRING SYSTEMS

4. AN INTRODUCTION TO AXIOMATIC DESIGN TO DESIGN COMPLEX SYSTEMS
4.1 OBJECTIVE OF AXIOMATIC DESIGN
4.2 INTRODUCTION TO THE PRINCIPLES
4.2.1 THE DESIGN PROCESS AND DESIGN AXIOMS
4.2.1.1 The Independence Axiom
4.2.1.2 The Information Axiom
4.2.2 THE CONCEPTS OF DOMAINS
4.2.3 DECOMPOSITION AND HIERARCHY
4.3 AXIOMATIC DESIGN FOR SYSTEM DESIGN

5. A METHODOLOGY TO INTEGRATE THE STRATEGY
5.1 THE HIERARCHICAL MODEL OF STRATEGY
5.2 THE LINKAGE BETWEEN CORPORATE AND FUNCTIONAL STRATEGY
5.3 MANUFACTURING STRATEGY
5.3.1 DEFINITION
5.3.2 MANUFACTURING CAPABILITIES
5.3.3 MANUFACTURING DECISION AREAS
5.4 PRODUCT DEVELOPMENT STRATEGY
5.4.1 DEFINITION
5.4.2 PRODUCT DEVELOPMENT CAPABILITIES
5.4.3 PRODUCT DEVELOPMENT DECISION AREAS
5.5 STRATEGY INTEGRATION

6. SIMILARITIES AND INTERACTIONS BETWEEN PRODUCT DESIGN, PRODUCT DEVELOPMENT AND MANUFACTURING
6.1 SYSTEM SIMILARITIES BETWEEN MANUFACTURING AND PRODUCT DEVELOPMENT
6.2 LINKAGE BETWEEN PRODUCT DESIGN AND MANUFACTURING SYSTEM
6.2.1 PRODUCT DESIGN AND MANUFACTURING SYSTEM
6.2.2 PRODUCT PORTFOLIO AND MANUFACTURING SYSTEM

7. AXIOMATIC DESIGN FOR INTEGRATING THE DESIGN
7.1 A NEW CORPORATE SYSTEM
7.2 CHARACTERISTICS OF AXIOMATIC DESIGN WITHIN CORPORATE AND ORGANIZATIONAL DESIGN
7.2.1 AXIOMATIC DESIGN AND CORPORATE STRATEGY
7.2.2 AXIOMATIC DESIGN AND THE CONTROL OF SYSTEMS
7.3 ADDITIONAL ASPECT BEYOND AXIOMATIC DESIGN
7.4 THE MAPPING AND THE DECOMPOSITION OF THE MANUFACTURING SYSTEM DESIGN
7.4.1 THE CUSTOMER DOMAIN
7.4.2 THE FUNCTIONAL AND PHYSICAL DOMAIN
7.4.2.1 High level decomposition - level 1 to level 2
7.4.2.2 Mid-level decomposition - level 2 to level 3
7.4.2.3 Low level decomposition - level 3 to level 6 of the quality branch
7.5 THE MAPPING AND THE DECOMPOSITION OF THE PRODUCT DEVELOPMENT SYSTEM
7.5.1 UNDERLYING CAUSALITIES
7.5.2 CUSTOMER DOMAIN
7.5.3 FUNCTIONAL AND PHYSICAL DOMAIN
7.5.3.1 High level decomposition - from level 0 to level 2
7.5.3.2 Mid-level decomposition - from level 2 to level 4
7.5.3.3 Low-level decomposition - from level 4 to level 7

8. SUMMARY

9. ZUSAMMENFASSUNG

10. CONCLUSIONS

11. BIBLIOGRAPHY

Abstract

Thorough long-term success of a company derives out of its capability to adapt to the increasing market and customer requirements. Therefore competitive advantage has to be achieved throughout the entire company. In the past years the capability to gain such an unique advantage by a superior manufacturing strategy, by a superior operational effectiveness and a production system design was neglected due to the assumption that mainly product development and marketing strategies ensured a competitive distinction and advantage [Muffato 1996]. It seemed that greater improvements in manufacturing performance were irrevocably linked with additional investments.

However, the paradigms of Lean Production have macerated the traditional tradeoff between cost and quality. Furthermore, an excellence in manufacturing is seen more and more as a core strategic issue as the time to change to a new product at low cost and high quality can be decreased.

Numerous tasks and structures determine a possible manufacturing excellence. The major issues are to develop and continuously improve the design of the production system, to train the workforce and enhance their working knowledge. In addition, the external links within and without the company have to be established and optimized.

A special role is taken in by the product design as its geometry, structure, material and the derived processing and assembly operations highly determine the production system. In former days, this information was generated in product development¹ and passed sequentially on to process engineering and manufacturing planning. This led to a high degree of readjustment of already defined product properties due to the constraints from the existing manufacturing machinery and facilities [Clark/Fujimoto 1991]. Concurrent engineering integrates these restrictions into the product development with product and process engineer working closely together at the same time.

Although this integration already leads to shorter lead time and increased productivity, it only focuses on the procedural aspect, disregarding the possibility to align the system design of both production and the product development.

At the Production System Design Laboratory of the Massachusetts Institute of Technology, a decomposition framework of the design of a production system has been developed applying Axiomatic Design [Cochran 1998]. Further research has established specific linkages between the product design and the production system, e.g. in the parts complexity [Kim 1999] and in the equipment design [Arinez 1999].

The following diploma thesis describes and analyzes the linkage between the production system and the product development. Hereby the linkage is respected as consistent out of strategic and operational issues. Therefore the focus will be set on the methodology to integrate the manufacturing and product development strategy, its design and its control.

First, the strategic linkage between the objectives of manufacturing and product design has to be defined. This allows in the second to deploy a design of the product development system based on the existing decomposition of the production system design. Furthermore, the control will be integrated by linking the performance measurement system.

Index of figures

FIGURE 1: THE STRUCTURE OF A SYSTEM, ITS SUB-SYSTEMS AND BOUNDARIES

FIGURE 2: THE WIDER SYSTEM OF COMPANIES, THE COMPANY SYSTEM AND ITS SUB- SYSTEM [ADOPTED FROM WU 1994]

FIGURE 3: THE FUNCTIONAL DECOMPOSITION OF A CAR VS. THE OBJECT-ORIENTED VIEW OF A CAR [ADOPTED FROM WU 1994]

FIGURE 4: THE NATURE OF CLASSES AND OBJECTS

FIGURE 5: LINKS AND ASSOCIATIONS OF MACHINES WITH PARTS, AND ASSEMBLERS WITH PARTS

FIGURE 6: THE DIFFERENT VERTICAL LEVELS WITHIN MANUFACTURING SYSTEMS

FIGURE 7: A GENERAL PROCESS MODEL OF THE MANUFACTURING PROCESS [ALTING 1994]

FIGURE 8: MODEL OF MATERIAL PROCESS [ADAPTED FROM ALTING 1994]

FIGURE 9: MANUFACTURING PROCESS AS A IDEF0-MODEL [WU 1994]

FIGURE 10: CONTROL SYSTEM AS A SUB-SYSTEM OF A MANUFACTURING SYSTEM [ADAPTED FROM WU 1992]

FIGURE 11: INFORMATION BASED CONTROL AND CONTROL HIERARCHY [COCHRAN 1994]

FIGURE 12: PRODUCTION TIME OF A LOT AND A SINGLE-PIECE

FIGURE 13: PULL-SYSTEM VS. PUSH-SYSTEM [ADAPTED FROM MONDEN 1993]

FIGURE 14: PRODUCT DEVELOPMENT AS AN INFORMATION PROCESSING ACTITIVITY

FIGURE 15: HORIZONTAL FLOW OF INFORMATION [ADAPTED FROM PAASHUIS 1998]

FIGURE 16: METHODS, AREAS, RESULTS AND PERFORMANCE MEASURES OF INTEGRATION

FIGURE 17: INTEGRATION MECHANISMS BETWEEN DESIGNING A INFORMAL AND

FIGURE 18: DESIGN PARAMETERS OF INTEGRATION REGARDING THE INFORMATION

FIGURE 19: DIFFERENT ARRANGEMENTS OF INFORMATION PROCESSING ACTIVITIES

FIGURE 20: PRODUCT DEVELOPMENT AS A SIMULATION OF CONSUMPTION AND

FIGURE 21: PRODUCT DEVELOPMENT AND A SUB-SYSTEM

FIGURE 22: DIFFERENCES IN LEAD TIME AND ENGINEERING HOURS BY REGION [CLARK ET AL.1992]

FIGURE 23: DIFFERENCE IN AVERAGE PROJECT SCHEDULE PER STAGE [CLARK/FUJIMOTO 1991]

FIGURE 24: HORIZONTAL PLATFORM STRATEGY

FIGURE 25: VERTICAL PLATFORM STRATEGY

FIGURE 26: PLATFORM STRATEGY AND ITS IMPACT ON THE MANUFACTURING CYCLE TIME [ADAPTED FROM THORNTON 1999]

FIGURE 27: THE DESIGN PROCESS OF AXIOMATIC DESIGN

FIGURE 28: CAN AND BOTTLE OPENER

FIGURE 29: THE CLASSIFICATION OF THE MAPPING PROCESS BY EVALUATION OF THE DESIGN MATRIX: UNCOUPLED, DECOUPLED AND COUPLED DESIGN [ADOPTED FROM LINCK 1996]

FIGURE 30: MANUFACTURING SYSTEM WITH TWO SEPARATE SUPPLY LINES

FIGURE 31: MANUFACTURING SYSTEM AN INTEGRATED ASSEMBLY LINE

FIGURE 32: DESIGN RANGE, SYSTEM RANGE AND COMMON RANGE [ADAPTED FROM SUH 1998]

FIGURE 33: THE FOUR DOMAINS OF AXIOMATIC DESIGN [ADAPTED FROM SUH 1990]

FIGURE 34: THE MAPPING PROCESS BETWEEN THE FUNCTIONAL AND PHYSICAL DOMAIN OF AXIOMATIC DESIGN [ADAPTED FROM SUH 1998]

FIGURE 35: DESIGN MATRIX, MODULE AND THE JUNCTION-MODULE STRUCTURE [SUH 1999]

FIGURE 36: COMPONENTS OF THE JUNCTIONS IN THE FLOW DIAGRAM

FIGURE 37: SYSTEM DESIGN FLOW-DIAGRAM [SUH 1999]

FIGURE 38: HIERARCHICAL MODEL OF STRATEGY [ADOPTED FROM HAYES, WHEELWRIGHT 1984]

FIGURE 39: STRATEGIC POSITIONING VS. OPERATIONAL EFFECTIVENESS [ADAPTED FROM PORTER 1996]

FIGURE 40: CONTENT AND LINKAGES WITHIN A CORPORATE HIERARCHICAL STRATEGY

FIGURE 41: DECOMPOSITION OF THE CORPORATE SYSTEM

FIGURE 42: A NEW CORPORATE SYSTEM

FIGURE 43: MATRIX OF LEVEL

FIGURE 44: SEQUENCE OF IMPLEMENTATION OF DPS AND FRS

FIGURE 45: LEVEL 1 DECOMPOSITION

FIGURE 46: MATRIX OF LEVEL

FIGURE 47: LEVEL 11 DECOMPOSITION

FIGURE 48: MEAN AND VARIANCE THROUGHPUT TIME REDUCTION

FIGURE 49: CUSTOMER EXPECTED LEAD TIME AND THE CORRESPONDING INTERNAL TIME PORTIONS

FIGURE 50: MATRIX OF LEVEL

FIGURE 51: LEVEL 12 DECOMPOSITION

FIGURE 52: MATRIX OF LEVEL 12

FIGURE 53: LEVEL 111 DECOMPOSITION

FIGURE 54: MATRIX OF LEVEL

FIGURE 55: DECOMPOSITION OF LEVEL Q

FIGURE 56: MATRIX OF LEVEL Q1

FIGURE 57: DECOMPOSITION OF LEVEL Q12

FIGURE 58: THE MATRIX OF LEVEL Q12

FIGURE 59: DECOMPOSITION OF LEVEL A

FIGURE 60: MATRIX OF LEVEL A

FIGURE 61 DECOMPOSITION OF LEVEL A

FIGURE 62: MATRIX OF LEVEL A3

FIGURE 63: DECOMPOSITION OF LEVEL 11

FIGURE 64: MATRIX OF LEVEL 11

FIGURE 65: DECOMPOSITION OF LEVEL 12

FIGURE 66: MATRIX OF LEVEL 12

FIGURE 67: DECOMPOSITION OF LEVEL 13

FIGURE 68: MATRIX OF LEVEL 13

FIGURE 69: DECOMPOSITION OF LEVEL

FIGURE 70: MATRIX OF LEVEL

FIGURE 71: DECOMPOSITION OF LEVEL

FIGURE 72: MATRIX OF LEVEL

FIGURE 73: DECOMPOSITION OF LEVEL 121

FIGURE 74: MATRIX OF LEVEL

FIGURE 75: DECOMPOSITION OF LEVEL

FIGURE 76: MATRIX OF LEVEL

FIGURE 77: DECOMPOSITION OF LEVEL

FIGURE 78: MATRIX OF LEVEL

FIGURE 79: DECOMPOSITION OF LEVEL E

FIGURE 80: MATRIX OF LEVEL E1

FIGURE 81: DECOMPOSITION OF LEVEL I1

FIGURE 82: MATRIX OF LEVEL I

FIGURE 83: DECOMPOSITION OF LEVEL I

FIGURE 84: MATRIX OF LEVEL I11

FIGURE 85 DECOMPOSITION OF LEVEL I

FIGURE 86: MATRIX OF LEVEL I

FIGURE 87: DECOMPOSITION OF LEVEL I

FIGURE 88 MATRIX OF LEVEL I13

FIGURE 89: DECOMPOSITION OF I

FIGURE 90: MATRIX OF LEVEL I133

FIGURE 91: DECOMPOSITION OF L1

FIGURE 92: MATRIX OF LEVEL L1

FIGURE 93: DECOMPOSITION OF L2

FIGURE 94: MATRIX OF LEVEL L2

FIGURE 95: DECOMPOSITION OF LEVEL D

FIGURE 96: MATRIX OF LEVEL D1

FIGURE 97: DECOMPOSITION OF LEVEL D

FIGURE 98: MATRIX OF LEVEL D2..

Index of tables

TABLE 1: THE ELEMENTS OF A MANUFACTURING SYSTEM AND THEIR INTERACTION

TABLE 2: MARKET REQUIREMENTS, THE DERIVED MANUFACTURING CHARACTERISTICS AND THE DIFFERENT MANUFACTURING TYPES [PARTLY ADAPTED FROM CHRYSSOULOURIS 1994]

TABLE 3: THE BASIC CORRELATION BETWEEN THE ARRANGEMENT OF MANURACTURING ELEMENTS AND TYPE OF MANUFACTURING SYSTEM

TABLE 4: MEASURE OF DIFFERENT TYPES OF MANUFACTURING SYSTEMS [ADAPTED FROM ASKIN/STANDRIDGE 1993 AND COCHRAN 1999]

TABLE 5: RELATIONSHIP BETWEEN PROCESS FLEXIBILITY AND PRODUCT ARCHITECTURE [ULRICH 1995]

TABLE 6: FOUR DOMAINS OF THE DESIGN WORLD FOR VARIOUS DESIGNS [ADAPTED FROM SUH 1998]

TABLE 7: THE DIFFERENTATION OF SYSTEMS DUE TO THE FREQUENCY OF CHANGE AND THE NUMBER AND NATURE OF THE FUNCITONAL REQUIREMENTS

TABLE 8: CORPORATE AND MANUFACTURING CAPABILITIES

TABLE 9: DECISION AREAS OF MANUFACTURING STRATEGY [PARTLY ADOPTED FROM HAYES/WHEELWRIGHT 1984 AND RUDBERG 1999]

TABLE 10: Corporate and Product Development Capabilities

TABLE 11: DECISION AREAS OF PRODUCT DEVELOPMENT STRATEGY

TABLE 12: CORRELATION OF DECISION AREAS OF MANUFACTURING AND PRODUCT DEVELOPMENT

TABLE 13: SIMILARITY OF MANUFACTURING AND PRODUCT DEVELOPMENT

TABLE 14: CORRELATION OF PRODUCT DESIGN AND MANUFACTURING SYSTEM

TABLE 15: CORRELATION OF PRODUCT PORTFOLIO AND MANUFACTURING SYSTEM

Index of abbreviations

Abbildung in dieser Leseprobe nicht enthalten

1. INTRODUCTION

The following thesis elucidates the impact of the product design and the product development process on the design of a manufacturing system. In contrast to integrate constraints and restrictions of the manufacturing system and its processes into the initial design of a product², attributes and characteristics of the product design are analyzed by the way they influence and restrict the design of a manufacturing system. The upcoming hypothesis of this thesis claims latter approach to be the natural and logical one.

A sophisticated design theory known as Axiomatic Design [Suh 1990] is used to embed the design of a manufacturing system into the design of the product and the product development system. The generic derivation of such an integrated design framework will allow a broad application to manufacturing and product development system design.

The following paragraph outlines the background and the issues related to the motivation for this thesis. In the next step, the thesis objectives and hypothesis are stated, marking the scope and content of this academic discussion. Finally, a brief overview is provided about the content and structure of each chapter.

1.1 BACKGROUND AND MOTIVATION

Thorough long-term success of a company derives out of its capability to adopt to increasing market and customer requirements. Market success is determined by the competitive advantage a corporation inhibits throughout its entire corporate activities. However, the leverage to achieve such competitive advantage was primarily seen in attributes related to the appearance of the product in the market, less in the design and operation of internal activities [Clark/Fujimoto 1991]. Marketing and product strategies seemed to ensure market success, neglecting the potential linked with superior operational effectiveness [Muffato 1998]. Yet the success of corporations like Toyota in Japan emphasized the necessity to not only focus on product attributes, but also to stress the management and design of the operational system of a corporation, which strongly contributes to superiority in performance [Cochran 1999, Suh/Cochran/Lima 1998].

Numerous tasks and structures determine a possible manufacturing excellence. The major issues are to develop and continuously improve the design of the production and manufacturing system, to train the workforce and enhance their working knowledge. In addition, the external links within, e.g. to product development, sales, finance and distribution, as well as outside, e.g. suppliers and customers, of the company have to be established and optimized. A special role is taken by the product design as its geometry, structure and material highly determines the production and manufacturing system. In former days, this information was generated in product development³ and sequentially passed on to be implemented into the existing manufacturing system. This led to a high degree of readjustment of already defined product properties due to the existing production system [Clark/Fujimoto 1991]. Concurrent engineering integrates these restrictions into the product development with product and process engineer working closely together at the same time. Although this integration already leads to shorter lead time and increased productivity, it only focuses on the procedural aspect, disregarding the possibility to align the system design of both the manufacturing and the product development.

As the frequency of product introduction due to a more demanding market increased and thus the product life-time shortened, the design task was primarily related to the product, assuming that the manufacturing system design is fairly static. Since the design of a product and the design of a manufacturing system are highly interdependent and the attributes of a product furthermore change rapidly, it was self- evident to derive constraints and restrictions of the manufacturing system and processes to integrate them into the design process of the product. However, this approach neglects the dynamic nature of a manufacturing system and reduces the potential of a corporation to optimize the production and manufacturing activities by adjusting the design and layout of the manufacturing system to the product design. Furthermore, the first step when designing a corporation or system which strives to sell a product is to determine the physical or non-physical attributes of the product before designing the manufacturing system. In addition, the design of a manufacturing system is nearly completely fixed by the attributes of the product, leaving few options when deciding about the variables of the manufacturing system.

Several examples exist which clarify the close relationship between product design and manufacturing system design. The Second Industrial Revolution for instance, which based on the principles of the mass production established by Henry Ford in the 1910´s to 1920´s , was closely linked to the interchangeability of parts [Cochran 1994, Womack/Jones/Ross 1990]. A standardized product design with minimized tolerances made it possible to abolish the manual adjustment of parts and reduce the variations in the assembly time, which is a prerequisite for installing a tact time. An additional characteristic of mass production referred to the reduction of product variety, enabling the dedication of a manufacturing system to only one single product.

A more recent example may be seen in the tendency of increasing the degree of integration of the product architectures [Ulrich 1995, Ulrich/Eppinger 1995]. Former products, which consisted of several hundred small parts, now include only some few parts due to more sophisticated designs and more complex manufacturing processes. This led to a rapid decrease of necessary assembly work per product, however enlarged the investment into the tools and machinery within the processing area. In addition, product variety accelerated as the customer requirements turned increasingly fragmented and individualized [Wheelwright/Clark 1991]. Manufacturing systems had to move from the former single dedication to one or a few products to be able to cope with an entire product family and several product variations. The principles behind a manufacturing cell incorporate the necessity to produce different products or a product family at a standardized assembly time.

The aforementioned examples clarify the statement above regarding the product and its enhanced attribute as the dominant determinant on the design of the manufacturing system. Changes in the objectives of the manufacturing system are therefore closely related to changes in the product attributes.

At the Production System Design Laboratory of the Massachusetts Institute of Technology, a decomposition framework of the design of a manufacturing system design has been developed applying Axiomatic Design [Cochran 1998]. Further research has established specific linkages between the product design and the manufacturing system, e.g. the degree of parts complexity and production costs [Kim 1999] as well as product design and equipment design [Arinez 1999].

The Department of Design in Mechanical Engineering and the Institute for Machine Tools and Industrial Management have founded a special collaborative research project⁴ to optimize assembly automation by developing new methodologies, computer integrated supporting tools for design and by improving the elements of flexible assembly systems [Technical University of Munich 1997]. Embracing several partial projects, the research area for instance analyzed additional product characteristics and the product development process to simplify the design of assembly equipment and system.

1.2 THESIS OBJECTIVES

As stated in the former chapter, the design of a product has highly influenced the design of a manufacturing system. Hereby the design of a product includes issues related to the shape and physical properties, to the process of product development, as well as the product architecture and the degree of product variety a manufacturing system has to deal with.

The objective of this diploma thesis is to describe and analyze the linkage between the design of a product and the design of manufacturing system. This includes the necessity to outline the general activities related to product design, product development, as well as the design of a manufacturing system and its underlying principles. Furthermore, this academic discussion will develop a systematic methodology to integrate the design of both the product design, the product development process and the manufacturing system by using Axiomatic Design [Suh 1990].

The common research concerning the design of manufacturing system and product design respected the interdependence of both activities, however assumed when designing one of the two the other one as rather static [Suh/Lima/Cochran 1999, Eppinger 1995]. When regarding product design, the manufacturing system was assumed as static in structure as the frequency of change of products exceeded that of the manufacturing system by far. The constraints and restrictions of the manufacturing system were integrated into the design process to reduce the development lead time and to minimize the adjustments to the manufacturing system such as additional investment into tools, equipment and machinery. On the other hand, the design of a manufacturing system reduced the scope by considering a certain family or portfolio of products as given without specifying the underlying product attributes. However, the initial design of the manufacturing system is solely dependent on the product, its design and the degree of variety.

The hypothesis of this thesis claims that the design of a manufacturing system is primarily based on the attributes of the product design and should be the second step when designing a corporate system. Throughout the thesis, the hypothesis will be elucidated and tested, whereas the validation is provided in chapter 6. Several aspects are associated with the nature of the linkage between product design and manufacturing system design. Within the scope of this thesis is the design and the control of the system of product development and manufacturing system. The linkage is hereby respected as consistent of strategic and operational issues within the design and control task. One part of the linkage will analyze and classify product characteristics deriving from the product architecture which influence variables within the design of the manufacturing system. The second part will discuss an integrated design of the product development system⁵ and the manufacturing system.

As the product design, the product development system and the manufacturing sytem differ in their underlying structure, the integrated design requires a broad applicable and low formalized design methodology. The design methodology Axiomatic Design [Suh 1990] offers the possibility to derive a consistent design starting from market and customer attributes and ending at the process variables and will serve as a base for the following design. The generic derivation of such an integrated design framework will allow a broad application to manufacturing and product development system design.

1.3 THESIS OUTLINE

To provide a succinct description of the structure and the organization of this thesis, each chapter is briefly summarized. It also outlines the flow of ideas and highlights the context for which each chapter is written.

In chapter 2, the main theories related to the production and manufacturing system are presented. However, before presenting the constituents of such a specific system, a general consistent understanding of systems and their elements has to be provided. Following up, the production and manufacturing system are defined and introduced in more detail. The last part enfolds the principles behind Lean Production and the Toyota Production System, which reflect the current most successful design rules concerning a manufacturing system.

The following chapter 3 illustrates the various constituents behind product development. This embraces introducing the basic information process, the involvement of supplier, and defining a product development system. In addition, the theories underlying the architecture and platform of products are highlighted.

Since the assumptions behind a design methodology impact its design, Axiomatic Design will be presented in chapter 4. Besides the introduction into the objective and the basic principles of Axiomatic Design, the specific assumptions for the design of a complex system are outlined.

In chapter 5, the linkage of product development and manufacturing system is prepared by introducing the nature of strategy and developing major strategic decisions areas within both systems. Finally, both systems will be aligned by their strategic objective.

The analysis of this linkage is continued towards more discrete variables of the product design, the product portfolio and the manufacturing system as highlighted in chapter 6. Chapter 7 will finally incorporate the gathered ideas of chapter 2 to 6 and introduce the design of a new defined corporate system. This definition will allow to integrate the design of the product development and manufacturing system following Axiomatic Design.

In the end, Chapter 8, 9 and 10 will summarize the results of this thesis in English and in German.

2. THE PRODUCTION AND MANUFACTURING SYSTEM

To analyze the linkage between the manufacturing system and product development and to integrate their design, a general understanding of the nature of the production and manufacturing system is developed in the following chapter.

The first paragraph provides an introduction into systems theory and object oriented modeling, whereby the definition of a system, its nature and hierarchy are outlined. In the next step, system theory is then applied to define the production system. As the production system is a wider system covering all activities, which are necessary to produce a product, the manufacturing system is then defined as a sub-system of the production system. Thereafter, the main objects and relationships of the manufacturing are elucidated, allowing to see the first linkage to product design and product development. A short view is then taken on what types of manufacturing system have evolved due to what kind of characteristics. With the scope of the thesis to design a system, the current methodologies to design manufacturing systems are briefly summarized, whereby Axiomatic Design will be presented in chapter 4.

To close the chapter, the Lean Production System is introduced as an experience based arrangement of methods and theories to design a production system.

2.1 AN INTRODUCTION TO SYSTEMS THEORY AND OBJECT-ORIENTATION

System theory follows the objective to simplify the description and analysis of a physical real world object or to define a conceptual entity, for instance a software system. In particular, it overcomes the restriction of the functional approach by considering activities in their entirety. A system can be defined as

“a set of elements embodying specific characteristics. Between the elements are relations representing the functional connections of the elements. The system has a defined boundary to its environment and all elements exist within the boundary.” [Bruns 1988 as quoted in Linck]

A system is an assembly of elements or components. These components represent the structural, the operating and the flow elements that are individually identifiable, for instance people, machines, tools, and parts in a manufacturing system [Wu 1994]. Each element is related direct or indirectly to every other element in the system. An element may possess one or more attributes, whereby the attributes describe any property that characterizes the element, for instance its shape, color, heat or motion. Furthermore, elements can be system inherent entities, where an entity equals a sub- system itself. A collection of elements is enclosed within a system boundary to form a system. A generic system covers a certain type of relation and element and follows a logical objective.

To characterize the objective, the output achieved by certain input as illustrated in figure 1 can be identified.

Abbildung in dieser Leseprobe nicht enthalten

FIGURE 1: THE STRUCTURE OF A SYSTEM, ITS SUB-SYSTEMS AND BOUNDARIES

A manufacturing system may for instance be defined as a

“... a system [...] in which raw materials are processed from one form into another, known as a product, gaining a higher added value in the process” [Parnaby 1979 as quoted in Cochran p.36]

Therefore several possibilities to define a system coexist, whereas a thorough definition covers the constituents of a system, including elements, inputs, and outputs. The elements execute transformations on other elements, whereas the elements can either only be briefly part of the system, for instance if the system is open and parts pass the system boundaries, or remain within the system. This transformation is expressed by the change of the attributes, e.g., when transforming a piece of raw material into a finished product by a machining operation and an assembly operation. The state of a system is thus determined by the totality of these attributes [Wu 1994]. A system normally covers a wide variety of transformations within the systems boundary. In terms of system theory, the term process is regarded as a specific set of changes in the values of the attributes of elements.

Enclosing the same type of elements (e.g. a specific material, information) or attributes (e.g. shape, heat) can draw the boundary of a process. In general a system contains several types of processes, but basically one type of process dominates the system. In the following chapters, product development will be introduced as a system dominated by information processing activities, along with manufacturing systems dominated by material processes.

As an element can equal a system itself, it implies that systems are hierarchical in nature, for the system at one level can either turn to be a sub-system or an element of higher systems. When for instance thinking of a business corporation as a wider system of companies, a car manufacturer is one element in the company system. On the one hand, the manufacturer is a sub-system of the a business system, and on the other hand it is the higher system in relation to the manufacturing or product development system as illustrated in figure 2.

A wider system like a company system can influence its constituent systems by defining operational goals and by measuring and controlling the performance. In chapter 2.3.7, the

Abbildung in dieser Leseprobe nicht enthalten

FIGURE 2: THE WIDER SYSTEM OF COMPANIES, THE COMPANY SYSTEM AND ITS SUB-

SYSTEM [ADOPTED FROM WU 1994]

control of a system will be introduced when designing a control system for an integrated manufacturing and product development system.

In reference to the definition of properties as attributes to characterize a system, certain properties are linked with a certain hierarchy level and may not be exhibited by the lower levels. These so called emergent properties, which state that a system contains additional relationships, behavior patterns and even elements than the sum of its parts respectively, its sub-systems [Wu 1994].

After having introduced the nature and structure of a system, a practicable method is elucidated to define and set-up a system. The easiest way is to commence with classifying the input and output of the system, and with these constituents to define the underlying process or transformation. Finally, the elements, relationships and subsystems if applicable may be analyzed.

The core problem lies within capturing completely the output and input. Hence, grouping the outputs in basic or complementary and the input into resources and supports can endorse this analytic step.

However, system theory is only applicable as far as sub-systems can be formed. Thereafter, a system designer will return to decompose the sub-system by defining processes and functions. Finally, small parts and functions will emerge with a less abstract description, but with the lack of meaningfulness. Additionally, with the market requirements alternating frequently, the system has to be changed in its design, causing increased efforts for maintenance and modeling.

In contrast, the object-oriented methodology refers to the definition of systems and sub- systems as a collection of classes of objects. The underlying construct lies within the object as being a single entity incorporating both the structure and behavior [Rumbaugh et al. 1991]. A core difference between conventional and object-oriented methodologies to decompose systems is that in the former case the focus is set on defining the levels of sub-level, whereas the object-oriented approach models the level of the individual entities within the problem domain, as illustrated in figure 3 [Wu 1994].

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FIGURE 3: THE FUNCTIONAL DECOMPOSITION OF A CAR VS. THE OBJECT-ORIENTED VIEW OF A CAR [ADOPTED FROM WU 1994]

Objects are an abstraction of the real world entities and denote their individuality by their identity. They encapsulate the information about their nature by an arrangement of attributes, attribute value, and operations. Similar to systems theory, attributes are stated as named properties, with the operations being the only possibility to access modifying the attributes and thus characterizing the behavior of the object. To mark the limits in the real world, constraints may be defined which restrict the values an entity can adopt. In Figure 4, two real world entities, a turning and a grinding machine, illustrate the nature of objects and their interaction.

To change therefore a defined object status and behavior, an operation has to be initiated by a message from a requesting object sent to the referred object to invoke the required operation. This individual stimulus from one object to another is referred to as an event. The response of the object depends on the state of the receiving object.

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FIGURE 4: THE NATURE OF CLASSES AND OBJECTS

Obviously, both machines match in several attributes, operations and messages. The object-oriented methodology refers to a group of such similar objects as a class, whereby every object is considered as an instantional part or an instance of the class. The class with the smallest arrangement of common attributes, operations and messages is defined as the super-class. Every class with added information inherits the behavior and data of the super-class and forms a sub-class. The objects of the detailed subclass “grinding machine” for instance inherit the behavior of the super-class “machine”.

Without establishing links and associations, object-orientation would disregard the highly related nature of real world entities. In analogy to objects and classes, a link as the either physical or conceptual connection between connection between object instances represents the instance of an association. Therefore an association incorporates a type of links connecting objects from the same classes. In general, an association is stated as a class and includes attributes, operations and messages. An association could grasp the relationship between parts, machines and operators, as presented in figure 5.

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FIGURE 5: LINKS AND ASSOCIATIONS OF MACHINES WITH PARTS, AND ASSEMBLERS WITH PARTS

To reemphasize, the advantage of object-orientation lies within the flexibility of changing the modeled system. When an object is defined, the encapsulation allows to place the object wherever it is requested. Furthermore, new classes can easily be added by defining a new sub-class and inheriting the properties of the super-class.

In terms of object-orientation, a system may be divided into sub-systems, whereas a sub-system covers a set of classes, associations, operations, events and constraints. However, in contrast to systems theory, the identification of the sub-systems relies not on the input, output and incorporated elements, but on a set of related abstractions or service, which are in general independent of abstractions in other subsystems [Rambaugh 1991]. Although independence of sub-systems can not always be fulfilled, the boundaries of sub-systems should be determined in order to reduce the interactions among other sub-systems. When decomposing further down, a hierarchy of high-level and low-level systems emerges, whereas modules determine the smallest entity within a system. Such a module may highlight one perspective of a situation, and can be defined as a construct to group classes and associations. Hence, modules represent a manageable part of an object model.

Several criteria related to the environment, objects, attributes, the input and output allow classifying systems. As the determining criteria are highly depending on the specific system, they will be presented in the context of the manufacturing system in chapter 2.3 due to their specific application.

The definitions and characteristics above allow to derive both a manufacturing and product development system and to describe their linkages and a possible integrated design. Furthermore

“a system model is constructed to help understand relationships between elements, forms, processes and functions, and to enhance our ability to predict system response to inputs from the environment... this understanding may enable us to control system behavior.” [Rubinstein 1975]

The evident advantage of defining and modeling real world entities into systems, sub- systems and objects is continued in chapter 2.3.7 when referring to system control and measurement.

As the management of such complex system is normally out of the scope of a single individual person, several methodologies associated with systems design management and maintenance have emerged [Sage 1992]. The term systems engineering refers to the

“... the design, production and maintenance of trustworthy systems within cost and time constraints.” [Sage 1992]

Despite, these activities will be accomplished applying Axiomatic Design as elucidated in chapter 4. Additional steps beyond Axiomatic Design will refer to methodologies from System Engineering and introduced when applied to.

Both theories, systems theory and object-oriented modeling, simplify the later design of the manufacturing and the product development system by providing a consistent base for describing real world entities. However, the decomposition will only circumscribe sub-systems with the main interactions with other sub-systems, with seldom going into the detail of enumerating the different attributes in a class of elements. Rather are the links and associations in some cases used to for instance elaborate flexible resource allocation.

2.2 THE PRODUCTION SYSTEM

The production system is the most embracing view of the manufacturing task. Production may be defined as

“a network of processes, operations and information flow. [Shingo 1989]”⁶

However, within academic research it is unclear whether the production system covers all functions and activities [Sesterhenn 1997], or solely incorporates the manufacturing system enlarged by purely manufacturing supporting activities [Cochran 1999]. The second viewpoint resolves in a definition as follows:

“The production system design includes the design of the performance measurement system and supporting elements of the manufacturing system. The production system defines the measurable parameters that the manufacturing system must achieve... Production system design encompasses and includes the manufacturing system design and predicates overall design effectiveness.”[Cochran 1999]

What could be accountable for the above mentioned, more focussed definition of the production system is that the broader definition bounders all corporate function and therefore delivers no extra value for analysis. Although outlined as the design task, it can be clearly derived that the production system incorporates the manufacturing system, the supporting elements and the control activities including the performance measurement system.

In contrast to arrange the elements and relationships into corporate functions, a production system may be seen as a collection of business processes [Hammer/Champy 1993]. Every business process follows a specific logical objective of the system and embraces the related functions. All business processes contribute to particular tasks within the production system. Although various tasks exist, three fundamental managerial tasks can be determined: the task of information management, of physical transformation and of problem solving [Womack/Jones 1996]. This approach overcomes the common approach to optimize production systems at the level of isolated functions and operations [Cochran 1999, Suh/Cochran/Lima 1998] by regarding the primarily task as the overall system design. All processes within the production and the other related parts of a company strive to achieve value. Value is not a common definable attribute, but dependent on the market and customers.

2.3 THE MANUFACTURING SYSTEM

Regardless to the former definition, a manufacturing system is undoubtedly a subsystem to the production system [Suh/Cochran/Lima 1999]. Before actually proposing a definition, the manufacturing system may be classified by attributes of systems theory to ease the subsequent tasks of analysis and integration.

The first criterion refers to the state of the elements by assigning a physical or conceptual existence. Although a manufacturing system consists primarily of real objects such as machinery and equipment, the common analysis of the information and material flow focuses on the conceptual state. When resolving the regarded sub-system level, the physical existence appears dominant, as the information flow turns into its elements such as a heijunka box⁷, kanban cards or the bill-of-materials. Although dualistic in its nature, a manufacturing system is however regarded as conceptual [Wu 1994]. The sum of the physical elements would neglect important properties which emerge when moving to the higher level of system hierarchy⁸.

Following up, the second criterion defines whether the system elements and its relationships change in number and in nature. The structure of a static system remains without alteration, whereas a dynamic system may be defined as

“ a system whose state depends on the input history” [Rubinstein 1975]

A manufacturing system may therefore be either of a static nature if once the design is completed it maintains its structure, or either be of a dynamic nature what for instance corresponds to the philosophy of continuous improvement or to chances caused by a new product platform.

To describe the interaction of a system beyond its boundary, a system may be classified as closed or open. The interaction is defined by the existence of a flow of any kind of elements across the system boundary. Open systems in general show a higher adaptability in order to survive in a competitive business environment. Easy enough, a manufacturing system is regarded as a open system, by solely exchanging raw materials or the produced goods.

2.3.1 DEFINITION OF A MANUFACTURING SYSTEM

To describe a manufacturing system, different approaches stressing different constituents should be made. At first, a manufacturing system may be referred to as a

“[...] system - a subset of the production system - [...] the arrangement and operation of elements (machines, tools, material, people and information) to produce a value- added physical, informational or service product whose success and cost is characterized by the measurable parameters of the system design”. [Cochran/Lima 1998]

Stressing the relationships between the different elements, additional constituents can be elaborated if the manufacturing system is defined

“[...] as a combination of humans, machinery and equipment that are bound by a common material and information flow.”[Chryssolouris 1992]

The value achieved within the manufacturing system can be outlined by stating the manufacturing system as a system

“ [...] in which raw materials are processed from one form into another, known as a product, gaining a higher added value in the process. ” [Parnaby 1979]

Within a manufacturing system, the term process refers to the course in time and space by which material is transformed into a product. The term operation embraces the change in attributes of a material by the interaction of the product with a machine or with a worker. Within the process, four basic elements can be distinguished: processing, inspection, transportation, and delay⁹ [Shingo 1989].

2.3.2 THE ELEMENTS OF A MANUFACTURING SYSTEM

A manufacturing systems consists of various types of elements. Different types of subsystems can be defined, in their nature either physical, conceptual or even both. In Table 1, the elements of a basic manufacturing system are presented. Although some elements may not be highlighted, the enumeration covers the general elements and sub-systems of a manufacturing system. To track the interaction between physical and conceptual sub-systems and elements, the input and output passing the system boundary are elaborated, separated into resources and supports on the inflow side and into basics and supplementary on the outflow side.

In the case of a machine operation, a worker might insert a product into the fixture of the machine and start the operation. During the operation, raw material or semi- finished goods, energy, information concerning the product geometry and lubricants are added. These inputs are passed through the system border of the machine and contributed to the operation. Finally, the output will be embodied in the change of physical attributes of the product. The output of a sub-system can only be per definition of the same type as the input. In a similar case, an assembly activity, the worker will fit two parts together, applying his knowledge about the right alignment and adding his physical movement.

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TABLE 1: THE ELEMENTS OF A MANUFACTURING SYSTEM AND THEIR INTERACTION

In chapter 2.3.3, manufacturing processes will be elucidated by changing the value of the product’s attributes, for instance its shape and hardness.

The segmentation of the manufacturing system into sub-systems reflected a single horizontal view, however additional vertical levels exist. As illustrated in figure 6, four levels can be determined. Starting at the top-level, the term area covers the largest possible entity within a manufacturing system. The boundaries of an area reflect a specific product, process or a conversion flow¹¹. The next smaller entity is the cell, which includes connected stations or operations to produce a part family with a high degree of flexibility. Further down, a station presents a linkage of one or more basic machines, offering several types of processing like turning, drilling or milling. Finally, the smallest entity within a manufacturing system is a machine, which provides a specific processing step [Cochran 1994, Black 1991]. This hierarchy corresponds to the different level of control and will be introduced in the context of manufacturing control in chapter 2.3.7.

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FIGURE 6: THE DIFFERENT VERTICAL LEVELS WITHIN MANUFACTURING SYSTEMS

The following chapter introduces the manufacturing process and addresses the different process types and stages to the changes in product properties.

2.3.3 THE MANUFACTURING PROCESS

As outlined in chapter 2.1, a system generally inhibits several types of processes, whereas one type of process dominates the system. In the case of a manufacturing system, a manufacturing process may be defined as

“a change in the properties of an object including geometry, hardness, state, information content (form data), […] To produce any change in property, three essential agents must be available: (1) material, (2) energy, and (3) information.” [Alting 1994]

For a manufacturing system, the dominant process type is the material process, as illustrated in figure 7.

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FIGURE 7: A GENERAL PROCESS MODEL OF THE MANUFACTURING PROCESS [ALTING 1994]

Furthermore, a refinement may be applied by regarding the change in material. A mass-conserving process (dM=0) maintains the mass of the process object, aiming at changing the shape. In the case of a mass-reducing process (dM<0), a change in shape or state of material is achieved by removal of material. Hence, an assembly or joining process (dM>0) obtains the final geometry by assembling or joining parts or components in a way that the final geometry is approximately equal to the sum of the masses of the components which are manufactured by one or both of the previous methods [Alting 1994].

The second agent, the information flow, consists of the information captured in the shape and property of the product. In a manufacturing process, the property information covers information contents about hardness, stiffness, strength and so on before and after the process. The shape information includes the specific geometry at a certain time during the process.

Energy as the third agent within a manufacturing process occurs as a supply, as a transmission to the work piece and in a removal or loss of energy. In reference to the three flows associated to a manufacturing process, a model as illustrated in Figure 8 incorporates all essential items and will serve as the basis for the later integration of the product design and the product development into the manufacturing system.

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FIGURE 8: MODEL OF MATERIAL PROCESS [ADAPTED FROM ALTING 1994]

Since the information serving the manufacturing process contains mainly assets deriving out of the product design and the product development process, a more detailed analysis is required.

Within a manufacturing system, the information content of a product increases by the extent of geometry-changing processes being applied. Information concerning the shape of a product Is is added by an interaction between a tool¹² with a certain contour content and a pattern of movement for the work material and the tool. Along the several processes, the information content is enlarged and reaches at the final stage the required output level Io, reflected in the final shape and property of the product. The change [Abbildung in dieser Leseprobe nicht enthalten] in information at a process step i adds therefore up out of [Abbildung in dieser Leseprobe nicht enthalten] , the change in property information and [Abbildung in dieser Leseprobe nicht enthalten], the change in shape information.

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For a manufacturing process, all three agents are governed by the control information. Its essential task covers to apply the right interaction between raw material respectively part at the forming medium, including data on the force, power, friction, lubrication and cutting geometry.

The model of manufacturing process above is satisfying when modeling physical transformation, however a more advanced way of modeling the relationships within an entire manufacturing systems has been established by the IDEF-model¹³. The IDEF- model consists of three levels. The first level, the IDEF0, is the static model of the functional relationships within a manufacturing system, composed out of the function block as shown in figure 9. IDEF1 reflects the data items related to the system, whereas IDEF2 simulates the dynamic behavior of the system. In the following paragraph the IDEF0 will be introduced, as it can be used to describe the functional relationships and specify the flow patterns of information and materials within a manufacturing operation [Wu 1992].

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FIGURE 9: MANUFACTURING PROCESS AS A IDEF0-MODEL [WU 1994]

The IDEF0 ‘s elemental unit is the function block. The function as a representation of activities incorporates an input and output, however the block is additionally connected to a control and a mechanism stream. Each of these streams consists of either physical or information objects. Input and output resemble to the process above, as the input is consumed by the function and leaves the function as the output, changing the properties of the function subject. The control flow presents the factors within a system that constrain the function’s performance, e.g., technical limits, schedules or capacity. Mechanisms reflect those sub-systems and entities, which enable the performance of the function, e.g., existing machinery, tools, people and capital. An output stream may serve as input, a control or a mechanism of another function [Wu 1992, Wu 1994].

Unlike a functional flow path, the IDEF0 models the static relationship of function, not the dynamic nature of a sequence of functions. Within an IDEF0 model, every function is displayed only once. The structure follows a top-down hierarchy, a function can therefore be decomposed into several sub-functions and treated as a black box at the high-level of modeling.

2.3.4 THE CHARACTERISTICS OF A MANUFACTURING SYSTEM

As a general definition of a manufacturing system, its elements and process is founded, the next step will be to derive the different types due to the specific characteristics. These characteristics may be classified by the differences in the system environment and the required system outputs. Hence, the characteristics enable to determine the right type of manufacturing system, which will be introduced in chapter 2.3.5. The distinction between the different types relies on the arrangement of the system’s elements and relationships.

In the chapter 5.3, the strategy for manufacturing will be connected to the choice of capabilities and activities [Skinner 1969, Hayes/Wheelwright 1984, Porter 1989]. For a manufacturing system, the choice refers to the capability to be adaptable to changes in production volume, to changes in the product design, the product variety as well as the frequency of new products [Shrensker 1990, Chryssolouris 1994, Askin/Standridge 1993].

As enumerated in table 2, every type of manufacturing system fits to a different degree of the specific market requirements. The specific requirements may be transferred in characteristics for the manufacturing system, which in the degree of their fulfillment differ the basic four types. The elements within a manufacturing system are arranged either following the sequence of processes a product dictates, or forming stations or departments of similar process, or combine the related processes for a product family into a cellular arrangement or finally are transported to a fixed product in the sequence they are required.

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TABLE 2: MARKET REQUIREMENTS, THE DERIVED MANUFACTURING CHARACTERISTICS AND THE DIFFERENT MANUFACTURING TYPES [PARTLY ADAPTED FROM CHRYSSOULOURIS 1994]

At first, a manufacturing system can differ by the capability to encounter the volume of product. With a high volume, the investment and the degree of dedication of the arrangement can be increased. On the long term, a manufacturing system can be differed by its capability to produce at changing volumes and thereby maintain reasonable unit cost.

Second, the different types have to encounter various kinds of products. A manufacturing system may be classified by its capability to produce a high degree of different products at the same time. With regard to a longer time period, the system has also to deal with changes in the market place leading to frequent product introductions and the capability to quickly amortize the necessary investments. In a market of simple, various short life commodity products, the manufacturing system will have to fulfil a different objective than in a specialized, customer-order based environment. A change in the product for instance may be related to a new geometry, to additional parts, to a different material or a new technology.

Finally, the product design affects the right choice of the manufacturing type. The dominant characteristic until now is the physical size, determining especially the necessity for the fixed position of the product in the case of a very large product, e.g., a airplane or a ship.

When closer analyzing the linkage between the product development and the assigned product designs with the manufacturing system, further implications will be found. For the following classification of different types of manufacturing types however, the discussed characteristics cover the relevant issues sufficiently.

2.3.5 TYPES OF MANUFACTURING SYSTEM

During the past, several types of manufacturing system serving various market environments and product designs emerged. The differences of the types are reflected in the arrangement of the system elements and relationships.

As a manufacturing system consists of machinery, people, and work-in-progress, the differences are related to the arrangement of the machinery respectively the machine layout, the human resource and product interaction respectively the degree of automation and the part and machinery relationship respectively the material and conversion flow. Furthermore, the way the information is processed through the system can be observed.

The following table 3 outlines the basic correlation between design concerning the arrangement of elements and the stated basic types of manufacturing systems. In the later chapter 6 elucidating the interactions and dependencies between product design and manufacturing systems, more specific variables are presented.

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TABLE 3: THE BASIC CORRELATION BETWEEN THE ARRANGEMENT OF MANURACTURING ELEMENTS AND TYPE OF MANUFACTURING SYSTEM

A strong relation is now viewable between the market environment, the suitability of the different manufacturing types, and the specific arrangement of the basic elements by combining the results of table 2 and table 3. In addition, performance measures can be assigned to the different manufacturing types, what is presented in table 4. The regarded set of values of measure allows to readjust the selection of the manufacturing type by the market environment with the proposed performance measures.

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TABLE 4: MEASURE OF DIFFERENT TYPES OF MANUFACTURING SYSTEMS [ADAPTED FROM ASKIN/STANDRIDGE 1993 AND COCHRAN 1999]

However, this elaboration might seem to deterministic and simplify the complexity of the design task of a manufacturing system to a too strong extent. In the next chapter, the design is more generally derived and regarded as a highly enduring challenge.

2.3.6 THE DESIGN OF A MANUFACTURING SYSTEM

In the basic meaning of the word, the task of design covers the choice of elements and their arrangement. Before designing a manufacturing system, the objective of the design has to be determined. This objective may be synthesized by the various performance requirements that derive from the chosen market the corporate entity strives to compete in. In chapter 2.3.4, five basic characteristics extracted from the market requirements have been introduced. Furthermore, four basic setups of manufacturing systems, stated as manufacturing types, were associated to different degrees of the characteristics. The differences between the manufacturing types correspond to the value of the decision variables. Therefore, the design can be conceptualized

“as the mapping from performance requirements of a manufacturing system, as expressed by values of certain performance measures, onto suitable values of decision variables, which describe the physical design of the manner of operation of the manufacturing system.” [Chryssolouris 1994]

However, the mass of decision variables within a manufacturing system requires a systematic approach, either by hierarchy or by segmentation. Until now, the design of manufacturing systems lacks of a common accepted methodology, embracing not only the initial design, but the additional methods required to develop and maintain system, e.g., modeling, analysis, evaluation and dynamic aspects. Within the scope of this academic discussion, a design methodology called Axiomatic Design will be introduced to serve as the framework for designing a complex system. Furthermore, a design of a manufacturing system applying Axiomatic Design is elucidated in chapter 7.4. The decomposition of the manufacturing system is not presented as this point, since the Axiomatic Design is a specific approach, however this chapters strives to provide a generic view of manufacturing systems.

Similar to the task of designing a product, the functional requirements and constraints for a manufacturing system change throughout the lifetime of the system [Suh/Cochran/Lima 1998, Chryssolouris 1994]. Hence, the design of a manufacturing system should be seen as an ongoing task, whereas the current design reflects the current stated functional requirements and constraints.

The task of design is based on assumptions concerning installing specific value of decision variables and achieving a desired system output. As a manufacturing system consists of many elements and various relationships between the elements, the behavior requires a feedback loop to the design task. In the following chapter, the methodologies connected to the control of a manufacturing system are introduced, closing the elucidation of the constituents of a manufacturing system.

2.3.7 THE CONTROL OF MANUFACTURING SYSTEMS

The term control in the context of a manufacturing system encompasses the tasks of maintaining and altering a desired state of a system [Wu 1992, Cochran 1994]. As stated in control theory, control can either be designed as an open-loop or a closed-loop model.

In the first case, which is also referred to as feedforward control, the control function refuses to apply information from the controlled operation of the system, but merely adjusts the actuator of a system. However, an open-loop control requires the exact knowledge about the system’s behavior to any internal or external disturbance.

In the second, more common case, control is achieved through a feedback loop by comparing the system output with the desired state of the controlled system operation and using this deviation to assign a change in the system’s actuator. The closed-loop model consists of four basic components as depicted in figure 10. Independent on the regarded system, a monitoring function obtains information about the controlled condition of the system and passes the information through the feedback path to the decision making function. Examples for a monitoring function are a human inspector at a machine, a physical sensor detecting wearout of turning tool or a performance measurement system. In the next step, the decision making function compares the received data on the controlled system operation with a reference level of desired condition and decides on the amount of correction to be sent to the actuator.

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FIGURE 10: CONTROL SYSTEM AS A SUB-SYSTEM OF A MANUFACTURING SYSTEM [ADAPTED FROM WU 1992]

Such a decision making function could be found in a worker manually operating a cutting process, in an intelligent control device of a turning machine or in a management committee. Following up, the actuator receives the determined deviation and acts onto the controlled system process. The action of the actuator enables the control by directing the system output towards the required level of reference.

A feedforward control model states the desired amount of correction for the actuator by measuring the controlled system operation before the actual process. In this case, control in its real sense can only occur when the decision making function is capable of forecasting any disturbances and of predicting the system reaction to the actuator signal.

Furthermore, the control of system may be differentiated by the location of the components of the control function. Intrinsic feedback refers to the integration and the undertaking of feedback and control within the system’s boundary. Extrinsic control in the contrast describes the case when feedback and control are located in a different system. Extrinsic control is very common and the basic model behind the hierarchy of control in complex systems.

In the example depicted in figure 11, a production system is recording a set of performance measures of its manufacturing system and comparing them with world- class benchmarks. Within the management, a set of redesign decisions are discussed and passed towards the manufacturing system engineering, which reflects the actuator role in the basic control model. Although not explicitly shown, the control hierarchy between the production and manufacturing system repeats itself when decomposing the system hierarchies within the manufacturing area, cell, station and machine.

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FIGURE 11: INFORMATION BASED CONTROL AND CONTROL HIERARCHY [COCHRAN 1994]

The basic model in figure 11 reflects additional aspects of a hierarchical control system. Throughout the system, the measuring function will capture different kinds of measures in different formats. At the top level of a manufacturing system, synthesized measures like the average unit cost or the return on investment may be recorded, whereas a operator at a machine will use physical measures like the tolerances of the manufacturing process. Additional, the necessary information has to be provided at the right time to the right place. A delay in time will complicate a appropriate control [Cochran 1994]. Finally, a system can be controlled intrinsic and extrinsic at the same time, what also can be seen in figure 11. In this case, the controlled and measured system operations should not interfere, as no efficient control would be possible. It is rather a question of which measures are controlled by which entity, assigning more high-level aspects to the production system and more system-level aspects to the manufacturing system. The optimal control can take place when the decision making function is assigned to the most knowledgable entity and the actuator refers to the entity which actually can change the system state.

2.4 LEAN PRODUCTION

Until now, the design of a manufacturing system has been highlighted as a purely analytical task, based on well-defined theories and methodologies. However, the decision process in the design of a real world system is submitted to uncertainty. Therefore many design decisions are made on the base of general assumptions about the current best practice. Such a best practice reflects a set of underlying assumptions and design rules due to a specific market environment, existing technologies and general resources.

With the current market paradigms, the methods connected to the system design of the Toyota Production System offers the most sophisticated, experience-based design rules and are therefore presented in the following chapter

2.4.1 THE TRANSITION OF THE MARKET REQUIREMENTS

The principles and the methods of the Toyota Production System are a result of a long- term process of adapting the production and manufacturing system of the Toyota Corporation to the specific market environment [Shingo 1989]. At the stage of the resurrection of the Japan Industry after the Second World War, the market conditions in which Toyota headed to compete were very similar to those of the now outgoing 20th century. As the market was small, the possible sales volume where very low and hard enough, the Japanese customers required various kinds of automobiles due to the different usage, from small transporters to sedans to bigger commercial vehicles. Furthermore, hardly any capital was available for investment. Finally, the quality level was high as American and European car manufacturers were importing their products into Japan [Womack/Jones/Ross 1990]. As the possible sales prices for Japanese products were low, the requirements for designing a production system where not achievable when applying the traditional mass production principles.

2.4.2 THE PRINCIPLES OF THE TOYOTA PRODUCTION SYSTEM

In the following paragraphs the elements of the Toyota Production System are elaborated. Starting with the overall objective, the strategic and market goals are presented. Following the objective, the definition of waste and value enables to assign the main principles and operational efforts behind the Toyota Production System. As no established logical or hierarchical approach exists to present the Toyota Production System, the outlined theories and methods in chapter 2.4.2.1 to 2.4.2.5 are structured in analogy to the constituents of a production and manufacturing system

Often the Toyota Production System is reduced to the manufacturing system although it includes all activities needed to transform a customer requirement into a finished good. The following chapter will only refer to the Toyota Production System as a guideline and framework for a manufacturing system, whereas chapter 3.3.3 enhances the point of view by outlining the Toyota Production System approach to product development.

2.4.2.1 The Objective

The overall objective of the Toyota Production System is to establish a guideline to achieve competitiveness by maximizing profit, improving productivity and reducing the costs of a production system. Although the following equation only encompasses the financial objective of the Toyota Production System, it enables to assign the various goals into a single statement.

Unlike the manufacturers in the American and European market, Toyota introduced the alignment of all corporate activities to the approach of non-cost as it was founded and added target costing in 1959 [Cooper 1997], what incorporates a strategic as well as operational framework due to following equation [Shingo 1989]:

SALES PRICE - COST = PROFIT

At first, it clarifies that the sales price is an exogenous variable determined by the perceived value of the product in the customer’s eyes. Second, the leverage to increase the profit depends solely by the company’s ability to minimize the cost and to maximize the perceived value of the product. Enhancing the term cost by the meaning as a target cost, it states a limit of costs due to the development and production of a marketable performance.

Deriving from this framework, the Toyota Production System strives to continuously reduce the total costs. To design and control its system, it therefore clearly differs between the activities that add or not add value to the product. Later activities are recapitulated into the term waste, or muda [Ohno 1989], and are focussed on as the main lever to improve the production system.

2.4.2.2 The Definition of Value and Waste

The value rendered by any system is solely defined by the customer’s willingness to pay. For a car manufacturer, this can be defined as the value delivered by the transformation of the raw materials to the required finished product and by the individual created emotions linked with the use of a car. Hence, value is reflected as any absolutely necessary process and operation step to achieve.

The antipode is stated as waste, or muda, and incorporates any element of the process, operation or information that is intentionally not paid by the customer.

The nature of waste in a manufacturing system is either related to time, in financial terms capital or labor costs, to defects in functionality respectively material and manufacturing cost until the point of defect, or to oversized capacity respectively investment cost.

Theoretically, only processing adds value to a product, but in terms of Toyota Production System activities like transportation, inspection and storage are referred to as theoretical respectively necessary waste. However, real waste can be eliminated applying current technologies, production assets and resources.

Among all authors describing Toyota Production System, the waste occurring in a production system is caused by one of the following seven forms [Cochran 1994, Monden 1996, Ohno 1989, Shingo 1989]:

I. Waste of overproduction

This waste relates to the fact that a production system can either produce ahead of the actual customer demand, called early overproduction, or produce too many products, called quantitative overproduction [Shingo 1989].

II. Waste of waiting and delay

Waiting time is referred to as the time spent by completed products waiting to be withdrawn by a subsequent process, or by parts-in-process waiting to be assembled or processed [Monden 1996]. Existing worker capacity remains therefore unused and unnecessary inventory enforced.

III. Waste of transportation

As another activity adding waiting time, the way to reduce transportation is to avoid it by improving the design and layout instead of improving the transportation operation itself.

IV. Waste of processing

This form of waste enfolds the improvement of the processing step itself. A processing step for instance is not appreciated by the customer as assumed or the design lacks of simplicity and easiness to produce. Typical methods to apply are value engineering and methods like design-for-assembly [Boothroyd et al.], quality function deployment [Clausing 1988] or concurrent engineering. Thinking in terms of the design of the Production System and the Product Development System, an integration in design and control will decrease this waste.

V. Waste of inventory

Although overlapping with the definition in I. and II. , this waste focuses on inventory driven by semi-finished products waiting due to lot and process delay or work-in- progress.

VI. Waste of motion

As waste III. referred to the non-value added parts transport and movement, this waste clarifies the need to improve the worker utilization by reducing unnecessary steps of movement. Once again, the improvement should avoid the movement by redesigning layout or substitute work by automation, not improve the way of moving. VII. Waste of defects and correction

Again, the aim of the Toyota Production System is to avoid the occurrence of defects or at least to detect it as early as possible, instead of improving the way of correcting the defects. The Toyota Production System heads to 100% inspection, to increase self and successive inspection and to develop mistake-proof operations [Shingo 1989]. VIII. Waste of excessive production resources

Maximizing the machine utilization was one of the major misunderstandings that led to over-engineered existing production facilities and an increase in inventory and order lead-time. All resources, from the work force to the machine and the standard work-in- progress, should be right-sized due to the customer demand. The increased volume and product flexibility enables to optimize the assigned production resources and capacity.

2.4.2.3 The Process

When TPS refers to the term process, the view is set to the flow of material in time and space. In the transformation from raw material to a finished product, the differentiation of process elements into processing, inspection, transportation and delay enables to describe all activities concerned with the flow of material and the product.

At first, the production plan has to be established. TPS introduces therefore the two probably most known approaches, namely ordered-based production and non-stock production, better known as just-in-time.

In contrast to producing a product based on forecast, TPS heads to reflect the actual customer demand by producing at the time it is needed, at the quantity it is needed and at the mix it is needed. Thereby excess inventory and long order lead-time are prevented. To achieve order-based production, the production cycle P has to be reduced to be less or equal to the period between order and delivery D, otherwise a “supermarket” approach has to be adopted [Shingo 1989]. To reduce the production cycle TPS proposes to increase the standardization of work, to equal processing time of the different production stages, to move to one-piece flow and to redesign the layout and linkage of the processes due to reduce transportation and inventory. Since these are solely general statements, the advantage of TPS is to provide a consistent variety of well-experienced methods.

Several ways exist of shortening the production cycle [Shingo 1989], which include reducing process and lot delay, optimizing the layout and the linkage of the manufacturing system and establishing a tact time.

The delay due to a process basically occurs when a part or a lot is waiting to be processed. As long as the processing time at a machine or station is equal, the processes can be synchronized.

In the two scenarios illustrated in figure 12, the difference in the throughput time is obtained by moving from a lot size of 60 to a single piece flow. Neglecting the transportation time between the three stations, the throughput time is reduced from 15 hours to 5 hours 15 min.

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FIGURE 12: PRODUCTION TIME OF A LOT AND A SINGLE-PIECE

In many cases, faster machines have to be slowed down or slower machines increased in their capacity to allow a synchronized process flow.

This requires balancing the work content of the synchronized stations. In the case of an assembly line, the assembly steps operated by the workers have to be assigned at the design stage of the system and equally distributed. Without ensuring that the required time for every workstation to carry out the assigned tasks fits into the tact time, processing delays will occur. The tact time provides a mean to integrate the pace of the customer demand into the individual manufacturing activities of the sub-systems, the manufacturing areas, the cells, stations and machines.

In contrast, delay may be caused by the time a part has to wait due to the arrangement of parts into a lot. As depicted in figure 12, the production cycle varies strongly by the size of the lot. By reducing the lot size to one, the production time can be diminished to the actual processing time and some additional time for transportation. However, single piece flow requires prerequisite action, especially the reduction of the setup time and a plant layout that facilitates the transportation between the processes.

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¹ Product development in its meaning as the organizational system, not as the procedure

² Typical methodologies and techniques include design-for-assembly or design-for-manufacturing theories [Boothroyd 1987, Boothroyd/Dewhurst 1988].

³ Product development in its meaning as the organizational system, not as the procedure

⁴ Sonderforschungsbereich 336

⁵ When referring to an integrated design of two areas within a company the object of analysis should be of the same kind. It is therefore required to define a system of product development, which enlarges the boundary of the term from an configuration of information processing activities to a complex arrangement of elements. The definition will be elaborated in detail in chapter 3.3.1.

⁶ The terms process, operation and information flow will be elaborated in more detail in chapter 2.4.

⁷ The heijunka box is a instrument of the Toyota Production System to visualize the sequence, mix and available production time to meet the customer demand.

⁸ Such additional properties are stated as emergent properties in systems theory.

⁹ In the one of the following chapters, chapter 2.3, the change in attributes of a product during the manufacturing process will be introduced in more details

¹⁰ Although products are of a physical nature, they differ in the attribute to machines or the workforce as they merely pass through the manufacturing system, however are not stationary. The input and output elements therefore are the constituting elements of the sub-system themselves.

¹¹ A conversion flow is the physical order in which a part is processed. Manufacturing cells are often designed to encompass a conversion flow.

¹² The term tool is used in a broader way as it includes all physical instruments that are able to change the shape or property information of a product.

¹³ IDEF stands for Integrated computer-aided manufacturing definition.