Design Methods in the Aerospace Industry: Looking for Evidence of Set-Based Practices by Joshua I. Bernstein Master of Engineering Aeronautics and Astronautics Massachusetts Institute of Technology, 1997 Bachelor of Science Mechanical Engineering The Johns Hopkins University, 1996 Submitted to the Technology and Policy Program in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY May, 1998 © Massachusetts Institute of Technology, 1998 All Rights Reserved Author ________________________________________________________________________ Technology and Policy Program May 8, 1998 Certified by ____________________________________________________________________ John Deyst Professor, Departments of Aeronautics and Astronautics Accepted by ___________________________________________________________________ Richard de Neufville Chairman, Technology and Policy Program 2 Design Methods in the Aerospace Industry: Looking for Evidence of Set-Based Practices by Joshua I. Bernstein Submitted to the Technology and Policy Program on May 18, 1998 in partial fulfillment of the requirements for the degree of Master of Science in Technology and Policy. Abstract A new paradigm in engineering design, known as set-based concurrent engineering (SBCE), has been proposed which seems to offer advantages over more traditional techniques. This research, therefore, had three goals: 1) to develop a clear understanding of the definition of SBCE and to contrast that definition with other theories, 2) to assess the “set-basedness” of the aerospace industry, and 3) based on the assessment, to propose a model for implementing SBCE within an aerospace development project. While set-based concurrent engineering consists of a wide variety of design techniques, the basic notions can be stated in two principles: 1) engineers should consider a large number of design alternatives, i.e., sets of designs, which are gradually narrowed to a final design, and 2) in a multidisciplinary environment, engineering specialists should independently review a design from their own perspectives, generate sets of possible solutions, and then look for regions of overlap between those sets to develop an integrated final solution. This research found that while no company’s design process completely fulfilled both of these criteria, many set-based techniques are used within the aerospace industry. Building on some of the observed industry practices, a design process model is proposed which combines concepts from lean manufacturing, such as “flow” and “pull,” to implement set-based concurrent engineering. Thesis Supervisor: John Deyst Title: Professor of Aeronautics and Astronautics, MIT 3 4 Acknowledgements Many people have assisted me in the endeavor now represented by this thesis. Without their time, effort, advice, and support I could never have completed this work. I first owe my gratitude to the Lean Aerospace Initiative, which funded this research. LAI represents a unique opportunity for a graduate student to work directly with members of the aerospace industry, and I consider myself very fortunate to have been able to make a contribution to this effort. LAI is not simply an abstract organization, however. I owe a great debt to the many people who are LAI. First, I must thank my site visit coordinators and escorts at the companies which I visited. They were willing to take one, two, or even three days off from their busy work schedules to show a wide-eyed graduate student how aerospace systems really are designed and developed. In addition, I thank the many engineers and managers who were willing to spend an hour or two sharing the details of their work. Though these people must remain nameless in this document, I thank them all. I also must thank my advisors. First, Professor John Deyst. John has advised me now for two years, over the course of two Masters degrees and two theses. I have valued his time and assistance and his genuine concern for my academic experience. During this work I have also been fortunate to be able to call upon an array of additional advisors. Within LAI, I thank Professor Earll Murman, Professor Stan Weiss, and especially Dr. Joyce Warmkessel and Dr. Eric Rebentisch for their time and advice. I was fortunate enough to meet Dr. Bill Finch, a “kindred spirit” here at MIT in the realm of set-based concurrent engineering. Without his willingness to listen to my ramblings on several late nights, I would not have been able to pull this work together. I must also thank my “advisors at large,” Professor Al Ward, at the University of Michigan, and Professor Durward Sobek, at the University of Montana. Al and Durward are some 5 of the original developers of the theory of set-based concurrent engineering, and their advice and input were essential to my work. Finally, I must thank my family: Mom, Pop, Jesse, and especially my wife, Ritu. Without their support, none of this would have been possible. 6 Table of Contents ABSTRACT....................................................................................................3 ACKNOWLEDGEMENTS....................................................................................5 TABLE OF CONTENTS .....................................................................................7 LIST OF FIGURES.........................................................................................15 LIST OF TABLES ..........................................................................................19 1. INTRODUCTION......................................................................................21 1.1 MOTIVATION AND OBJECTIVES OF THIS RESEARCH....................................................................21 1.2 THESIS OVERVIEW AND OUTLINE...........................................................................................22 2. POINT-BASED APPROACHES AND CONCURRENT ENGINEERING.....................23 2.1 CHAPTER INTRODUCTION......................................................................................................23 2.2 POINT-BASED STRATEGIES....................................................................................................23 2.3 POINT-BASED STRATEGIES AND CONCURRENT ENGINEERING......................................................24 2.3.1 Traditional Approaches to Product Development: Over the Wall..........................................24 2.3.2 The Separation and Integration of Knowledge....................................................................25 2.3.3 Transitioning to Concurrent Engineering.........................................................................31 2.3.4 Interteam Communication: An Integration Problem..........................................................34 2.3.5 Task Sequencing.........................................................................................................35 2.3.6 Establishing Requirements in the Point-Based Approach and Doing It Right the First Time......36 2.4 THE RISKS AND LIMITATIONS OF THE CE SOLUTION..................................................................37 7 2.5 SUMMARIZING THE CE SOLUTION.........................................................................................39 3. DEFINING SET-BASED CONCURRENT ENGINEERING ....................................41 3.1 CHAPTER INTRODUCTION......................................................................................................41 3.2 THE TRIPLE PROBLEM: FACTORS MOTIVATING THE NEED TO DELAY DECISION-MAKING................41 3.3 THE NEED FOR A PARADIGM SHIFT.........................................................................................47 3.4 SET-BASED CONCURRENT ENGINEERING DEFINED.....................................................................47 3.4.1 An Introductory Summary.............................................................................................47 3.4.2 Developing Sets of Alternatives.....................................................................................49 3.4.3 Using Sets to Communicate and Guide Development.........................................................50 3.4.4 Using Sets to Integrate and Optimize a Design..................................................................54 3.4.5 Requirements in the Set-Based Context............................................................................55 3.4.6 Managing Set-Based Concurrent Engineering....................................................................56 3.5 OTHER METHODS WHICH RECOMMEND CARRYING OPTIONS.......................................................57 3.5.1 Two Examples............................................................................................................57 3.5.2 Contrasting These Methods with SBCE: Different but Highly Complimentary......................60 3.6 SBCE VERSUS PLATFORM DESIGN..........................................................................................61 3.7 SUMMARIZING SET-BASED CONCURRENT ENGINEERING.............................................................62 4. EXAMPLE OF SBCE FROM TOYOTA AND ITS SUPPLIERS..............................67 4.1 INTRODUCTION: “THE SECOND TOYOTA PARADOX”..................................................................67 4.2 SET-BASED PRACTICES WITHIN TOYOTA..................................................................................68 4.2.1 Design Organization....................................................................................................68 4.2.2 A Quick Overview of the Process Highlighting the Use of Sets...........................................69 4.2.3 Discussion of the Process: The Relationship between Upstream and Downstream Groups and the Use of Standardized Processes............................................................................................................72 4.3 SET-BASED PRACTICES BETWEEN TOYOTA AND ITS SUPPLIERS.....................................................74 8 5. ASSESSING THE “SET-BASEDNESS” OF THE AEROSPACE INDUSTRY: SETTING THE STAGE .................................................................................................77 5.1 CHAPTER INTRODUCTION......................................................................................................77 5.2 RESEARCH DESIGN..............................................................................................................77 5.3 OVERVIEW OF RESULTS........................................................................................................81 5.4 COMMON THEMES: AN EXAMPLE..........................................................................................82 5.5 DISCUSSION........................................................................................................................85 5.5.1 Conceptual Design Processes.........................................................................................85 5.5.2 The Departure of the Conceptual Designers......................................................................87 5.5.3 Relationships between Engineers....................................................................................88 5.5.4 The Impact of the Contracting Environment.....................................................................89 5.5.5 The Analysis Cycle as a Driver of the Design Process........................................................90 5.5.6 Long Lead Items as Drivers of the Design Process.............................................................91 5.6 COMMON THEMES: IN CLOSING….........................................................................................91 6. EXAMPLES OF DESIGN STRATEGIES.........................................................93 6.1 CHAPTER INTRODUCTION......................................................................................................93 6.2 EXAMPLE 1: CAPITALIZING ON THE POINT DESIGN...................................................................93 6.2.1 Introduction and the Underlying Theme: Speed.................................................................93 6.2.2 Approach to Requirements and the Limitation of the Method...............................................94 6.2.3 “Just Do It” Design: The 80/20 Rule, Select an Option Quickly, and Plan for Success............96 6.2.4 Making the Method Work: Robustness, People, and Small Teams......................................100 6.3 DISCUSSION OF EXAMPLE 1...................................................................................................101 6.4 EXAMPLE 2: DESIGN BY CONSTRAINT...................................................................................103 6.4.1 Introduction...............................................................................................................103 6.4.2 A Multi-Tiered Approach.............................................................................................103 6.4.3 An Example..............................................................................................................105 9 6.4.4 Additional Issues........................................................................................................109 6.5 DISCUSSION OF EXAMPLE 2...................................................................................................111 6.6 EXAMPLE 3: COMBINING PARALLEL CONCEPT DEVELOPMENT WITH CONCEPTUAL ROBUSTNESS......113 6.6.1 Development of Parallel Design Concepts to Explore the Design Space................................113 6.6.2 Conceptual Robustness...............................................................................................114 6.7 DISCUSSION OF EXAMPLE 3...................................................................................................115 6.8 EXAMPLE 4: SUBSYSTEM INSTALLATION................................................................................116 6.8.1 Overview of the Design Dilemma..................................................................................116 6.8.2 New Developments.....................................................................................................117 6.9 DISCUSSION OF EXAMPLE 4...................................................................................................118 6.10 DESIGN STRATEGIES: POINT-BASED, WITH HINTS OF SETS........................................................119 7. VIRTUAL PRODUCT DEVELOPMENT TOOLS...............................................121 7.1 CHAPTER INTRODUCTION.....................................................................................................121 7.2 EXAMPLE 5: AN INTEGRATED DESIGN AND ANALYSIS PACKAGE................................................121 7.3 DISCUSSION OF EXAMPLE 6...................................................................................................124 7.4 EXAMPLE 6: USING COMPUTER TOOLS TO INSTITUTE A PROCESS-BASED DESIGN METHOD..............125 7.4.1 Introduction and Overview............................................................................................125 7.4.2 The Ideal Design Environment......................................................................................126 7.4.3 Involving Downstream Activities..................................................................................128 7.4.4 Convergence Range and Decision Gates..........................................................................128 7.4.5 Database Management.................................................................................................130 7.4.6 Pending Issues...........................................................................................................130 7.5 DISCUSSION OF EXAMPLE 6...................................................................................................131 7.6 CONCLUSIONS: THE CHALLENGES IN IMPLEMENTING VIRTUAL PRODUCT DEVELOPMENT TOOLS.....132 8. STANDARD PRODUCTS AND PRACTICES ..................................................135 8.1 CHAPTER INTRODUCTION.....................................................................................................135 10