Medical Device Design for Six Sigma E-Book

Basem El-Haik

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 811

Veröffentlichungsjahr: 2011

Beschreibung

The first comprehensive guide to the integration of Design for Six Sigma principles in the medical devices development cycle Medical Device Design for Six Sigma: A Road Map for Safety and Effectiveness presents the complete body of knowledge for Design for Six Sigma (DFSS), as outlined by American Society for Quality, and details how to integrate appropriate design methodologies up front in the design process. DFSS helps companies shorten lead times, cut development and manufacturing costs, lower total life-cycle cost, and improve the quality of the medical devices. Comprehensive and complete with real-world examples, this guide: * Integrates concept and design methods such as Pugh Controlled Convergence approach, QFD methodology, parameter optimization techniques like Design of Experiment (DOE), Taguchi Robust Design method, Failure Mode and Effects Analysis (FMEA), Design for X, Multi-Level Hierarchical Design methodology, and Response Surface methodology * Covers contemporary and emerging design methods, including Axiomatic Design Principles, Theory of Inventive Problem Solving (TRIZ), and Tolerance Design * Provides a detailed, step-by-step implementation process for each DFSS tool included * Covers the structural, organizational, and technical deployment of DFSS within the medical device industry * Includes a DFSS case study describing the development of a new device * Presents a global prospective of medical device regulations Providing both a road map and a toolbox, this is a hands-on reference for medical device product development practitioners, product/service development engineers and architects, DFSS and Six Sigma trainees and trainers, middle management, engineering team leaders, quality engineers and quality consultants, and graduate students in biomedical engineering.

Leseprobe

Contents

Foreword

Preface

1 MEDICAL DEVICE DESIGN QUALITY

1.1 INTRODUCTION

1.2 THE ESSENCE OF QUALITY

1.3 QUALITY OPERATING SYSTEM AND THE DEVICE LIFE CYCLE

1.4 EVOLUTION OF QUALITY

1.5 BUSINESS EXCELLENCE: A VALUE PROPOSITION

1.6 SUMMARY

2 DESIGN FOR SIX SIGMA AND MEDICAL DEVICE REGULATION

2.1 INTRODUCTION

2.2 GLOBAL PERSPECTIVE ON MEDICAL DEVICE REGULATIONS

2.3 MEDICAL DEVICE CLASSIFICATION

2.4 MEDICAL DEVICE SAFETY

2.5 MEDICAL DEVICE QUALITY MANAGEMENT SYSTEMS REQUIREMENTS

2.6 MEDICAL DEVICE REGULATION THROUGHOUT THE PRODUCT DEVELOPMENT LIFE CYCLE

2.7 SUMMARY

3 BASIC STATISTICS

3.1 INTRODUCTION

3.2 COMMON PROBABILITY DISTRIBUTIONS

3.3 METHODS OF INPUT AND OUTPUT ANALYSIS

3.4 DESCRIPTIVE STATISTICS

3.5 INFERENTIAL STATISTICS

3.6 NORMAL DISTRIBUTION AND THE NORMALITY ASSUMPTION

3.7 SUMMARY

4 THE SIX SIGMA PROCESS

4.1 INTRODUCTION

4.2 SIX SIGMA FUNDAMENTALS

4.3 PROCESS MODELING

4.4 BUSINESS PROCESS MANAGEMENT

4.5 MEASUREMENT SYSTEMS ANALYSIS

4.6 PROCESS CAPABILITY AND SIX SIGMA PROCESS PERFORMANCE

4.7 OVERVIEW OF SIX SIGMA IMPROVEMENT

4.8 SIX SIGMA GOES UPSTREAM: DESIGN FOR SIX SIGMA

4.9 SUMMARY

Appendix 4A: Cause-and-Effect Tools

5 MEDICAL DEVICE DESIGN FOR SIX SIGMA

5.1 INTRODUCTION

5.2 VALUE OF DESIGNING FOR SIX SIGMA

5.3 MEDICAL DEVICE DFSS FUNDAMENTALS

5.4 THE ICOV PROCESS IN DESIGN

5.5 THE ICOV PROCESS IN PRODUCT DEVELOPMENT

5.6 SUMMARY

6 MEDICAL DEVICE DFSS DEPLOYMENT

6.1 INTRODUCTION

6.2 MEDICAL DEVICE DFSS DEPLOYMENT FUNDAMENTALS

6.3 PREDEPLOYMENT PHASE

6.4 DEPLOYMENT PHASE

6.5 POSTDEPLOYMENT PHASE

6.6 DFSS SUSTAINABILITY FACTORS

6.7 BLACK BELTS AND THE DFSS TEAM: CULTURAL CHANGE

6.8 SUMMARY

7 MEDICAL DEVICE DFSS PROJECT ROAD MAP

7.1 INTRODUCTION

7.2 MEDICAL DEVICE DFSS TEAM

7.3 MEDICAL DEVICE DFSS ROAD MAP

7.4 SOFTWARE DFSS ICOV PROCESS

7.5 SUMMARY

8 QUALITY FUNCTION DEPLOYMENT

8.1 INTRODUCTION

8.2 HISTORY OF QFD

8.3 QFD FUNDAMENTALS

8.4 QFD METHODOLOGY

8.5 HOQ EVALUATION

8.6 HOQ 1: THE CUSTOMER’S HOUSE

8.7 HOQ 2: TRANSLATION HOUSE

8.8 HOQ 3: DESIGN HOUSE

8.9 HOQ 4: PROCESS HOUSE1

8.10 APPLICATION: AUTO 3 D

8.11 SUMMARY

9 DFSS AXIOMATIC DESIGN METHOD

9.1 INTRODUCTION

9.2 AXIOMATIC METHOD FUNDAMENTALS

9.3 INTRODUCTION TO AXIOM 1

9.4 INTRODUCTION TO AXIOM 2

9.5 AXIOMATIC DESIGN THEOREMS AND COROLLARIES

9.6 APPLICATION: MEDICATION MIXING MACHINE

9.7 APPLICATION: AXIOMATIC DESIGN APPLIED TO DESIGN CONTROLS8

9.8 SUMMARY

APPENDIX 9 A: MATRIX REVIEW 9

10 DFSS INNOVATION FOR MEDICAL DEVICES

10.1 INTRODUCTION

10.2 HISTORY OF THE THEORY OF INVENTIVE PROBLEM SOLVING

10.3 TRIZ FUNDAMENTALS

10.4 TRIZ PROBLEM-SOLVING PROCESS

10.5 IDEAL FINAL RESULT

10.6 BUILDING SUFFICIENT FUNCTIONS

10.7 ELIMINATING HARMFUL FUNCTIONS

10.8 INVENTIVE PRINCIPLES

10.9 DETECTION AND MEASUREMENT CONCEPTS

10.10 TRIZ ROOT CAUSE ANALYSIS

10.11 EVOLUTION TRENDS IN TECHNOLOGICAL SYSTEMS

10.12 TRIZ FUNCTIONAL ANALYSIS AND ANALOGY

10.13 APPLICATION: USING TRIADS TO PREDICT AND CONCEIVE NEXT-GENERATION PRODUCTS1

10.14 SUMMARY

APPENDIX 10A: CONTRADICTION MATRIX

11 DFSS RISK MANAGEMENT PROCESS

11.1 INTRODUCTION

11.2 PLANNING FOR RISK MANAGEMENT ACTIVITIES IN DESIGN AND DEVELOPMENT

11.3 RISK ASSESSMENT TECHNIQUES

11.4 RISK EVALUATION

11.5 RISK CONTROL

11.6 POSTPRODUCTION CONTROL

11.7 SUMMARY

APPENDIX 11A ROBUST DESIGN FAILURE MODE AND EFFECTS ANALYSIS

12 MEDICAL DEVICE DESIGN FOR X

12.1 INTRODUCTION

12.2 DESIGN FOR RELIABILITY

12.3 DESIGN FOR PACKAGING (see Nolan, 2006)

12.4 DESIGN FOR MANUFACTURE AND DESIGN FOR ASSEMBLY

12.5 DESIGN FOR MAINTAINABILITY

12.6 DESIGN FOR SERVICEABILITY

12.7 SUMMARY

13 DFSS TRANSFER FUNCTION AND SCORECARDS

13.1 INTRODUCTION

13.2 DESIGN MAPPING

13.3 DESIGN SCORECARDS AND THE TRANSFER FUNCTION

13.4 TRANSFER FUNCTION MATHEMATICS

13.5 TRANSFER FUNCTION AND OPTIMIZATION

13.6 MONTE CARLO SIMULATION

13.7 SUMMARY

14 FUNDAMENTALS OF EXPERIMENTAL DESIGN

14.1 INTRODUCTION

14.2 CLASSICAL DESIGN OF EXPERIMENT

14.3 FACTORIAL EXPERIMENT

14.4 ANALYSIS OF VARIANCE

14.5 2K FULL FACTORIAL DESIGNS

14.6 FRACTIONAL FACTORIAL DESIGNS

14.7 OTHER FACTORIAL DESIGNS

14.8 SUMMARY

APPENDIX 14A

15 ROBUST PARAMETER DESIGN FOR MEDICAL DEVICES

15.1 INTRODUCTION

15.2 ROBUST DESIGN FUNDAMENTALS

15.3 ROBUST DESIGN CONCEPTS

15.4 APPLICATION: DYNAMIC FORMULATION

15.5 SUMMARY

16 MEDICAL DEVICE TOLERANCE DESIGN

16.1 INTRODUCTION

16.2 TOLERANCE DESIGN AND DFSS

16.3 WORST-CASE TOLERANCE

16.4 STATISTICAL TOLERANCES

16.5 TAGUCHI’S LOSS FUNCTION AND SAFETY TOLERANCE DESIGN

16.6 HIGH-VS. LOW-LEVEL REQUIREMENTS’ TOLERANCE RELATIONSHIPS

16.7 TAGUCHI’S TOLERANCE DESIGN EXPERIMENT

16.8 SUMMARY

17 MEDICAL DEVICE DFSS VERIFICATION AND VALIDATION

17.1 INTRODUCTION

17.2 DESIGN VERIFICATION PROCESS

17.3 PRODUCTION PROCESS VALIDATION

17.4 SOFTWARE VALIDATION

17.5 DESIGN VALIDATION

17.6 SUMMARY

18 DFSS DESIGN TRANSFER

18.1 INTRODUCTION

18.2 DESIGN TRANSFER PLANNING

18.3 PROCESS CONTROL PLAN

18.4 STATISTICAL PROCESS CONTROL

18.5 PROCESS CAPABILITY

18.6 ADVANCED PRODUCT QUALITY PLANNING

18.7 DEVICE MASTER RECORD

18.8 SUMMARY

19 DESIGN CHANGE CONTROL, DESIGN REVIEW, AND DESIGN HISTORY FILE

19.1 INTRODUCTION

19.2 DESIGN CHANGE CONTROL PROCESS

19.3 DESIGN REVIEW

19.4 DESIGN HISTORY FILE

19.5 SUMMARY

20 MEDICAL DEVICE DFSS CASE STUDY

20.1 INTRODUCTION

20.2 DFSS IDENTIFY PHASE

20.3 DFSS CHARACTERIZE PHASE

20.4 DFSS OPTIMIZE PHASE

20.5 DFSS VERIFY/VALIDATE PHASE

20.6 SUMMARY

Glossary: DFSS Terminology

Appendix: Statistical Tables

References

Index

Copyright © 2008 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc.

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, [phone], fax [phone], or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, [phone], fax [phone], or online at http://www.wiley.com/go/permission.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at [phone], outside the United States at [phone] or fax [phone].

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com.

Library of Congress Cataloging-in-Publication Data:

El-Haik, Basem.

Medical device design for six sigma: a road map for safety and effectiveness / Basem S. El-Haik, Khalid S. Mekki.

p. ; cm.

“A Wiley-Interscience publication.”

Includes bibliographical references.

ISBN 978-0-470-16861-5

1. Medical instruments and apparatus—Quality control. 2. Medical instruments and apparatus—Safety measures. 3. Six sigma (Quality control standard) I. Mekki, Khalid. II. Title.

[DNLM: 1. Equipment and Supplies—standards. 2. Equipment Design—methods. 3. Equipment Safety—standards. 4. Quality Control. W 26 E375d 2008]

R856.6.E44 2008

610.284—dc22

2007038229

To my parents, wife, and children for their continuous support.

—Basem El-Haik

To those that bring light to my life: my dear parents; my loving wife, Sara; my precious children, Subhi and Talah; my sisters and brothers; and last but not least, Dr. Basem Haik, who has been a great mentor to me.

—Khalid S. Mekki

FOREWORD

The world of complex machine design has evolved steadily for many years. The techniques used to design new products have evolved from the world of one-off designs, with a unique set of characteristics in each new design, to a place today where it is understood that most design efforts are bundled into innovations that are primarily existing or known solutions repackaged for the industry or a specific niche. The theory of inventive problem solving (TRIZ) tells us that 95% of each new design falls into that category.

If this is the case, why do we see the types of quality issues in the medical device industry that we do today? I believe it is because we often confuse the creative process with the robust engineering process. While there are many books that describe the use of specific designs for six sigma (DFSS) tools, there are no texts that help the design professional with the combination of all the DFSS tools necessary to produce a safe, efficacious medical device.

This book by Dr. El-Haik and his team serves as a guide to the design of such devices using the complete tool kit at a designer’ s disposal. It is meant to point out the attributes and applications of a multitude of tools that have long been known to contribute to better, more robust designs in a way that brings all of these tools together in one place. Clearly, this is “the right tool at the right time.”

Imagine a design based on the clarity of customer expectations born from a well-executed house of quality, design concepts conceived using axiomatic design and TRIZ, design outputs optimized using a solidly robust design of experiments, a robust failure modes effects analysis to guide risk management, and a state-of-the-art verification and validation process latched to a mistake proofed design transfer process. These tools, developed in other industries, can now be brought together in one place for the experienced designer to bring to bear for the service of the patient. The objective is to eliminate conceptual and operational design vulnerabilities and to produce an unprecedented device quality level as defined by the customer, by “doing the right things” and “doing things right.”

This book is the first on this subject. This team of authors are not academics; they are design practitioners tasked with the next generation of safe and effective products. There is much for us to learn from them.

Joseph P. Sener

V.P. Corporate Quality Systems and Business Excellence

Baxter International

PREFACE

Attention has begun to shift from the improvement of design quality in downstream development stages to its development in early upstream stages. This shift is motivated by the fact that design decisions made during the early stages of a product development cycle have the largest impact on the total life-cycle cost and quality of a system. It has been claimed that as much as 80% of the total life-cycle cost is determined during the concept development stage (Fredrikson, 1994). Research in the design and manufacturing arenas, including product development, is currently increasingly focused on addressing industry efforts to shorten lead times, cut development and manufacturing costs, lower total life-cycle cost, and improve the quality of end products and systems. It is the authors’ experience that at least 80% of a design’ s quality is also determined in the early design phases.

In general, quality can be defined as the degree to which the design vulnerabilities do not adversely affect product performance. In the context of designfor six sigma (DFSS) methodology, the major design vulnerabilities may be categorized as:

Conceptual vulnerabilities that are established due to the violation of design principles.Operational vulnerabilities that are created as a result of factors beyond the control of the designer, called noise factors. These factors, in general, are responsible for causing a medical device’ s functional characteristic or process to deviate from target values. Controlling noise factors is very costly or difficult, if not impossible. Operational vulnerability is usually addressed by robust design (Taguchi et al., 1989).

Conceptual vulnerabilities will always result in operational vulnerabilities. However, the reverse is not true. That is, it is possible for a healthy concept that is in full conformity with design principles to be operationally vulnerable. Conceptual vulnerabilities are usually overlooked during device development due to a lack of understanding of the principles of design, the absence of a compatible systemic approach to finding ideal solutions, the pressure of deadlines, and budget constraints. These vulnerabilities are usually addressed by traditional quality methods. These methods can be characterized as after-the-fact practices, since they use lagging information relative to developmental activities, such as bench tests and field data. Unfortunately, these practices drive development toward endless design–test –fix–retest cycles, creating what is broadly known in the manufacturing industry as a “firefighting” operational mode. Companies that follow these practices usually suffer from high development costs, longer time to market, lower quality levels, and a marginal competitive edge. In addition, firefighting actions to improve the conceptual vulnerabilities are not only costly but also difficult to implement, as pressure to achieve design milestones builds during the development cycle. Therefore, it should be a goal to implement quality thinking in the conceptual stages of a development cycle. This goal can be achieved when systematic design theories are integrated with quality concepts and methods up front. This book is geared toward developing an integration framework, a process, for quality in design by borrowing from quality engineering (Taguchi, 1986) and the axiomatic design principles of Suh (1990). This is the framework of DFSS. The objective of the DFSS process is to address design vulnerabilities, both conceptual and operational, by providing tools, processes, and formulations for their quantification, then elimination or reduction.

The medical device design solutions of current practices in many companies generally suffer from heightened vulnerability, such as modest quality levels, ignorance of customer wants and desires, complexity, and lack of conformity with a systematic design methodology to address those issues. Such vulnerabilities are common and generate hidden and unnecessary developmental effort in terms of non-value-added elements, and later, operational costs in the hands of the customer. Design vulnerabilities exhibit themselves by the degree of customer dissatisfaction, modest market shares, and rigid organization structure and operations complexity. Complexity in design creates operational bureaucracy that can be attributed to the lack of conformity with sound design processes. This root cause is coupled with several sources of variation in the medical device manufacturing and delivery processes, inducing variability in customer attributes, known as critical-to-satisfaction characteristics.

The success of the six sigma initiative, process, and deployment in many industries has generated enormous interest in the business world. In creating such successes, six sigma combines people power with process power. People power involves organization support and trained teams tackling specific objectives and stretched, yet feasible goals. Process power refers to effective six sigma deployment, risk mitigation, project management, and an array of statistical and system engineering–based methods. Six sigma focuses on the whole quality of a business, including product or medical device quality to external customers, and also the operational quality of all internal processes, such as accounting and billing. A whole quality business with whole quality perspectives will not only provide high-quality products or services, but will also have much lower costs and higher efficiency, because all the business processes are optimized.

Compared with retroactive six sigma, which features the DMAIC (define–measure–analysis–improve–control) process, medical device DFSS (identify–characterize–optimize–verify/validate) is proactive. The six sigma objective is to improve a process without redesigning the current process. The ultimate goal of medical device DFSS is whole quality: Do the right things; and do things right all the time. That is, achieve absolute excellence in design, whether it is a service process facing the customer or an internal business process (including product development) facing the employee. Superior medical device design will deliver superior functions to generate great customer satisfaction. Design for six sigma will generate an optimized device both conceptually and operationally within a process that delivers the medical device in a most efficient, economical, and flexible manner. A superior development process will generate a medical device that exceeds customer needs and wants, and delivers high quality at low cost. Superior business process design will generate the most efficient, effective, and economical business process. This is what we mean by whole quality. That is, not only should we have a superior device, but the design and production processes should always deliver what they are supposed to effectively and efficiently and at six sigma quality levels. It does not do a company good to develop some very superior products but some poor products as well—an inconsistent performance.

Medical device design for six sigma as described in this book proactively produces high consistency and extremely low variation in device performance. The term six sigma indicates low variation: 3.4 defectives per million opportunities (DPMO) or better, as measured by the distance between the specification limits and the mean in standard deviation units. We care about variation because customers “feel” inconsistency and variation; they do not feel averages. Nowadays, high consistency is necessary not only for reputation; it is also a matter of survival. For example, the well-known dispute between Ford Motor Company and Firestone Tires involved only an extremely small fraction of tires, but the negative publicity and litigation placed a giant company like Ford in big trouble.

Compared to six sigma (DMAIC), many new methods are introduced that add to the effectiveness of medical device DFSS. For example, axiomatic design, design for X, the theory of inventive problem solving (TRIZ), and transfer function and scorecards are really powerful methods to create superior device designs: to do the right things within our whole quality perspective.

This book also brings another class of powerful methods, Taguchi methods (robust design), into its tool box. A fundamental objective of the Taguchi methods is to create a superior product that can perform highly consistently despite the noise factors, the many external disturbances and uncertainties that arise: thus doing things right all the time. Because of DFSS tool sophistication, the training of DFSS operatives (black belts, green belts, etc.) is quite involved. However, this increment in investment is rewarded by better results. A main objective of this book is to provide a complete picture of medical device DFSS to readers, with a focus on development.

Objectives

The objectives of this book are:

1. To provide in-depth and clear coverage of philosophical, organizational, and technical aspects of medical device DFSS to readers.

2. To illustrate clearly all the medical device DFSS deployment and execution processes, the DFSS road map.

3. To present the know-how behind all the principal methods used in medical device DFSS, discussing the theory and background of each method clearly. Examples are provided with a detailed step-by-step implementation process for each method.

4. To help develop readers’ practical skills in applying DFSS in medical device environments.

Background Needed

The background required to study this book is some familiarity with simple statistical concepts, such as normal distribution, mean, variance, and simple data analysis techniques.

Summary of the Chapters

In Chapter 1 we introduce medical device design quality, its life cycle, and touch on the effects of regulations on device development. We define device quality as the whole quality, starting from idea generation until use by the customer, with the whole quality concept spanning the two boundary points and all developmental activities in between. A historical scan of quality approaches is provided. We introduce the device life cycle from several perspectives: design controls (regulations); design for six sigma tools, methods, and principles; as well as governing firm qualify system. We propose a highlevel business model for medical device firms based on experience from other industries.

In Chapter 2 we provide a global perspective of medical device regulations and focus on Food and Drug Administration regulations on design controls as they relate to medical device DFSS. This approach is warranted because of the similarities among the varying regulations, which indicate global harmonization.

In Chapter 3 we review some basic statistics that are used throughout the book. Statistical descriptive and inferential statistical techniques were reviewed at the basic level to ground the reader prior to tackling the heavily technical chapters.

In Chapter 4 we explain six sigma and how it has evolved over time. We explain that it is a process-based methodology and introduce the reader to process modeling with a high-level overview of process mapping. The criticality of measurement systems analysis is demystified. The DMAIC methodology and how it incorporates these concepts into a road map method are described, as is the business process management system for a medical device firm.

In Chapter 5 we offer a high-level DFSS process. The DFSS approach, as introduced, helps design teams frame their project with financial, cultural, and strategic implications to the business. In this chapter we form and integrate several strategic and tactical and synergistic methodologies to enhance medical device DFSS capabilities and to deliver a broad set of optimized solutions. We highlight and present the DFSS phases: identify, characterize, optimize, and verify/validate (ICOV).

In Chapter 6 we discuss the deployment of a medical device DFSS initiative, starting from scratch. We present the deployment plan, roles and responsibilities of deployment operatives, project sources, and other aspects of sound deployment strategy in three phases: predeployment, initial deployment, and steady-state deployment. We also discuss certain desirable design team characteristics and offer several perspectives on cultural transformation and initiative sustainability.

In Chapter 7 we present the medical device DFSS project road map. The road map highlights the ICOV phases at a high level over seven life-cycle development stages: idea creation, voice of the customer and business, concept development, preliminary design, design optimization, verification, and launch readiness. The concept of tollgate is introduced and we highlight the most appropriate DFSS tools and methods by DFSS phase, indicating where it is most appropriate to start tool use. Methods are presented in subsequent chapters. Manufacturing processes and software developments are discussed as parts of the medical device DFSS.

In Chapter 8 we present quality function deployment (QFD), used to translate customer needs and wants into focused design actions and paralleling design mappings. QFD is key tool used to prevent problems from occurring once a design has become operational. The link to the DFSS road map allows for rapid design cycle and effective utilization of resources while achieving six sigma levels of performance.

The design activity of design mapping is presented in Chapter 9. The medical device DFSS project road map recognizes two different mappings, functional mapping and process mapping. In this chapter we present functional mapping as a logical model depicting the logical and cause–effect relationships between design elements through techniques such as axiomatic design and value engineering. A process map is a visual aid for picturing work processes which shows how inputs, outputs, and tasks are linked.

The use of creativity and innovation methods such as the theory of problem solving (TIPS or TRIZ) in medical device DFSS is presented in Chapter 10. TRIZ provides design teams with a priceless toolbox for innovation to help see the true design opportunity and provide principles to resolve, improve, and optimize concepts. TRIZ is a useful innovation and problem-solving method that when applied successfully replaces the trial-and-error method in the search for vulnerability-free concepts. TRIZ-based thinking for medical devices helped to identify the technology tools that come into play, such as innovation principles, separation principles for resolving technical contradictions and conflicts, operators for revealing and utilizing system resources, and patterns of evolution of technical systems to support conceptual optimization.

In Chapter 11 we discuss the most significant aspects of building risk management into the flow of the design and medical device DFSS development process. We show how to embed the trade-off concept of risk–benefit analysis as part of the design and development process. DFSS methodology provides traceability where relationships between hazards, requirements, and verification and validation activities are identified and linked. In addition, we show that risk management itself is a process centered on understanding risks and evaluating their acceptability, reducing risks as much as possible, and then evaluating residual risk and overall device safety against the benefits derived. Integrating risk management into the medical device DFSS methodology requires keeping risk issues at the forefront of the entire process, from design planning to verification and validation testing. In this way, risk management becomes part of the product development process, evolves with the design, and provides a framework for decision making. We also discuss failure mode and effect analysis, a very important design review method used to avoid potential failures in design stages.

In Chapter 12 we introduce the concept of design for X (DFX) as it relates to medical device design, building on the work performed for generic product design. In this context we show that DFX for medical devices requires that the device content be evaluated to minimize complexity and maximize commonality. The end result will be a robust design that meets customer’s needs profitably through implementation of methods such as design for serviceability, packaging, assembly and manufacturability, and reliability.

In Chapter 13 we introduce the transfer function and design scorecard tools. The use of such DFSS tools parallels the design mappings introduced in Chapter 9. The transfer function is a mathematical relationship relating a design response to design elements. A design scorecard is used to document the transfer function as well as the optimization calculations.

In Chapter 14 we present the medical device DFSS approach to design of experiments (DOE), a prime optimization tool. DOE is a structured method for determining the transfer function relationship between factors affecting and comprising a device. DOE refers to experimental methods used to quantify indeterminate measurements of factors and interactions between factors statistically through observance of forced changes made methodically as directed by systematic tables called design arrays. The main DOE data analysis tools include analysis of variance, empirical transfer function model building, and main effects and interaction charts. These are presented in Chapter 13.

In Chapter 15 we present the use of robust parameter design methodology in the medical device design environment. Robustness thinking helps the DFSS team to classify design parameters and process variables mapped into the design as controlled or uncontrolled. The objective is to desensitize the design to uncontrolled disturbance factors, also called noise factors, thus producing a consistently performing on-target design with minimal variation.

Chapter 16 deals with the problem of how, and when, to specify tightened tolerances for a medical device so that quality and performance are enhanced. Every device (or its manufacturing processes) has a number—perhaps a large number—of design parameters (or process variables). We explain here how to identify the critical parameters and variables to target when tolerances have to be tightened. The objective is to provide useful techniques allowing further robustness gains on top of parameter design if so desired.

In Chapter 17, the final aspect of DFSS methodology, which differentiates it from the prevalent “launch and learn” method, is design verification, design validation, software validation, and process validation. This chapter covers in detail the verify/validate phase of the DFSS (ICOV) project road map. Design verification, process validation, and design validation help in identifying unintended consequences and effects of the design process, in developing plans and in reducing risk for full-scale commercialization to all stakeholders, including all customer segments. There is a degree of overlap with Chapter 18, and readers are encouraged to read these chapters in sequence.

In Chapter 18 we discuss design transfer as it relates to medical device DFSS. Design transfer simply encompasses clear establishment of a relationship between design engineering and production and service during the product life cycle. In the DFSS process this is an ongoing activity that will gain more momentum as the device design matures in the DFSS process (Chapter 7). Following the FDA regulation and to avoid duplication of effort on the part of the DFSS team, we strongly advocate use of a device master record (DMR) as the documented DFSS knowledge institutionalization. Depending on the project scope, the DFSS part may partially or fully overlap with the DMR. That is, a DMR is sufficient and necessary documentation of any device or subset. In this chapter we utilize advanced product quality planning and the production part approval process.

In Chapter 19 we present design change control, design review, and the design history file for a medical device DFSS project. The change control process manages change to ensure that any changes to a device’ s design, labeling, packaging, device master record, or design inputs prior to or after design transfer must be identified, documented, validated, or where appropriate, verified, reviewed, and approved prior to implementation, and finally, closed and documented in the design history file. Design reviews are a key design control element in quality system regulation 21 CFR 820.30(e). They are intended to assure that the design meets the requirements definition, and they also act as a mechanism for identification of a potential development weaknesses associated with safety, reliability, efficacy, manufacturability, service, implementation, and customer misuse of the device. These reviews are not to be mistaken with the DFSS project tollgate reviews discussed in Chapter 7.

In Chapter 20 we discuss the development of an automatic dissolving and dosing devise (Auto 3D) as a case study of medical device DFSS. In showing how DFSS applies to the development of Auto 3D, we provide a high-level understanding of the project rather than documenting every step and tool application.

What Distinguishes This Book from Others in the Area

This book is the first to address medical device design for six sigma and to present an approach with tool application examples and a medical device DFSS case study. The book’ s main distinguishing feature is its completeness and comprehensiveness, beginning with a high-level overview, deployment aspects, and a medical device design tool box. The most important topics in DFSS are discussed clearly and in depth. The organizational, implementation, theoretical, and practical aspects of the DFSS road map and DFSS toolbox methods are covered carefully and in complete detail. This is the only book that discusses all medical device DFSS perspectives, such as transfer functions, axiomatic design, TRIZ, validation and verification, design transfer, and Taguchi methods in great detail. It can be used as either a complete reference book on DFSS or as comprehensive training material for DFSS teams.

Acknowledgments

In preparing this book we received advice and encouragement from Joseph P. Sener, Vice President, Corporate Quality Systems and Business Excellence, Baxter International and appreciate his continuing support. The authors appreciate the willingness of several people to review this material: Rob Gier, George Dillon, James Plucinski, Brian Schultz, and Sahar Bahrani of Baxter International, Maher Alhaj for the artwork in Chapter 20, and Dr. Abdelqader Zamamiri of Abbott Loboratories. The authors are very thankful for the efforts of George Telecki, Melissa Valentine, and Rachel Witmer of John Wiley & Sons, Inc. We are especially thankful to www.Generator.com for many excellent examples in Chapter 10.

Contacting Dr. Basem El-Haik ([email protected])

Your comments and suggestions on the book will be greatly appreciated and will be given serious consideration for inclusion in a future edition. Six Sigma Professionals, Inc. (www.SixSigmaPI.com) conducts public and in-house six sigma and design for six sigma (DFSS) training and deployment workshops and provides program and project consulting services.

1

MEDICAL DEVICE DESIGN QUALITY

1.1 INTRODUCTION

Throughout the evolution of quality, there has always been a preponderance of focus on the manufacture of parts. In recent years, more applications have focused on design in general; however, the application of a full suite of tools to medical device design is rare and still considered risky or challenging. Some companies in the medical industry that have mature six sigma deployment programs see the application of design for six sigma to product and internal processes as an investment rather than a needless expense.

Attention has begun to shift from improvement of design quality in downstream development stages to early upstream stages. This shift is motivated by the fact that design decisions made during early stages of the product development cycle have the greatest impact on total life-cycle cost and system quality. It has been claimed that as much as 80% of the total life-cycle cost is determined during the concept development stage (Fredrikson, 1994). The deployment of design for six sigma in the device development and manufacturing arenas is currently experiencing an increased focus on addressing industry efforts to shorten lead times, cut development and manufacturing costs, lower total life-cycle cost, and improve device quality. It is the author’s experience that at least 80% of a design’s quality is also determined in the early design phases.

As mentioned in the Preface, design vulnerabilities are the result of poor quality and design engineering practices. In the context of design for six sigma (DFSS), the major design vulnerabilities are categorized as follows:

Conceptual vulnerabilities based on the violation of design principles (for examples of design principles, see Chapters 9 to 12).Operational vulnerabilities created as a result of factors beyond the control of designers, called noise factors. Such factors are, in general, responsible for causing a device’s functional characteristic or process to deviate from target values. Controlling noise factors is very costly or difficult, if not impossible. Operational vulnerability is usually addressed by robust design (see Chapters 15 and 16) (Taguchi et al., 1989).

In medical device design, conceptual vulnerabilities will always result in operational vulnerabilities. However, the reverse is not true. That is, it is possible for a healthy device concept that is in full obedience to design principles to be operationally vulnerable. In this book we are addressing the two categories of design vulnerability.

Profitability is one of the most important factors for any successful business enterprise. High profitability is determined by strong sales and overall low cost in all company operations. Healthy sales are determined strongly by high quality and reasonable price; as a result, improving quality and reducing cost are among the most important tasks for any business enterprise. Six sigma and DFSS are new business excellence initiatives that would effectively reduce cost and improve quality. In medical device design, quality and safety are interlinked. Most errors and inefficiencies in patient care arise from conflicting, incomplete, or suboptimal devices.

The objective of DFSS is to design and redesign medical devices to make them safer and more effective, patient centered, timely, and efficient. How does one achieve quality and safety by quality? What is quality?

1.2 THE ESSENCE OF QUALITY

Quality is a more intriguing concept than it appears to be. The meaning of the term has evolved over time as many concepts were developed to improve product or service quality, including total quality management (TQM), the Malcolm Baldrige National Quality Award, six sigma, quality circles, the theory of constraints quality management systems [ISO 9000 and ISO 13485], axiomatic quality (El-Haik, 2005), and continuous improvement. Following are various interpretations of quality: