Medical Device Design for Six Sigma
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"The book is well-written and the authors use well versed descriptions, easy to read figures and tables, and industry-related examples and case studies to explain what can be very complex concepts and processes. This book would be a valuable resource for anyone in the field of medical device design." (Doody's Book Reviews, October 2008)More details
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Content
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 Classifi cation.
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 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 Gose 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 HQQ Evaluation.
8.6 HQQ 1: The Customer's House.
8.7 HQQ 2: Translation House.
8.8 HQQ 3: Design House.
8.9 HQQ 4: Process House.
8.10 Application: Auto 3D.
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 Controls.
9.8 Summary.
Appendix 9A: Matrix Review.
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 Suffi cient 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 Products.
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.
11A.1 Parameter Diagram.
11A.2 Robust Design FMEA Elements.
12 Medical Device Design for X.
12.1 Introduction.
12.2 Design for Reliability.
12.3 Design for Packaging.
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 Experiments.
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.
14A.1 Diagnostic Plots of Residuals.
14A.2 Pareto Chart of Effects.
14A.3 Square and Cube Plots.
14A.4 Interaction Plots.
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 Verifi cation and Validation.
17.1 Introduction.
17.2 Design Verifi cation 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.
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 quality 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:
- "Quality means the totality of features and characteristics that bear on the ability of a device to satisfy fitness-for-use, including safety and performance" [21 CFR 820.3(s)].
- "Quality: an inherent or distinguishing characteristic, a degree or grade of excellence" (American Heritage Dictionary, 1996).
- "Quality and the required style of management" (W. Edwards Deming).
- "Conformance to requirements" (Philip B. Crosby in the 1980s).
- "Fitness for use" (Joseph M. Juran).
- "Degree to which a set of inherent characteristic fulfills requirements" (ISO 9000).
- "Value to some person" (Gerald M. Weinberg).
- "The loss a product imposes on society after it is shipped" (Genichi Taguchi).
- "The degree to which the design vulnerabilities do not adversely affect product performance" (Basem El-Haik).
Quality is a characteristic that a product or service must have. It refers to the perception of the degree to which a product or service meets a customer's expectations. Quality has no specific meaning unless it is related to a specific function or measurable characteristic. The dimensions of quality refer to the measurable characteristics that quality achieves. For example, in the design and development of a medical device:
- Quality supports safety and performance.
- Safety and performance support durability.
- Durability supports flexibility.
- Flexibility supports speed.
- Speed supports cost.
You can easily build the interrelationship between quality and all aspects of product characteristics, as these characteristics act as the qualities of the product. However, not all qualities are equal. Some are more important than others. The most important qualities are the ones that customers want most. These are the qualities that products and services must have. So providing quality products and services is all about meeting customer requirements. It's all about meeting the needs and expectations of customers.
When the word quality is used, we usually think in terms of an excellent design or service that fulfils or exceeds our expectations. When a product design surpasses our expectations, we consider that its quality is good. Thus, quality is related to perception. Conceptually, quality can be quantified as follows (Yang and El-Haik, 2003):
(1.1)
where Q is quality, P is performance, and E is an expectation.
In a traditional manufacturing environment, conformance to specifications and delivery are the common quality items that are measured and tracked. Often, lots are rejected because they don't have the correct documentation supporting them. Quality in manufacturing, then, is conforming product, delivered on time, and having all the supporting documentation. In design, quality is measured as consistent conformance to customer expectations.
The expected performance is actually "what this design can do for me" in the eyes of customers. The American Society for Quality (ASQ) defines quality as a subjective term for which each person has his or her own definition. In technical use, quality can have two meanings: (1) it represents the characteristics of a product or service that bear on its ability to satisfy stated or implied needs; or (2) it describes a product or service free of deficiencies. By examining ASQ's definition, we see that "on its ability to satisfy stated or implied needs" means that a product or service should be able to deliver potential customer needs; we call it "doing the right things." And "free of deficiencies" means that the product or service can deliver customer needs consistently. We can call this "doing things right all the time." Several concepts that are associated with quality are defined below (see http://www.praxiom.org/iso-definitions.htm).
- Quality system: the organizational structure, responsibilities, procedures, processes, and resources for implementing quality management.
- Quality policy: the overall intentions and direction of an organization with respect to quality as established by management with executive responsibility.
- Quality management: includes all the activities that managers carry out in an effort to implement their quality policy. These activities include quality planning, quality control, quality assurance, and quality improvement.
- Quality audits: a systematic independent examination of a manufacturer's quality system that is performed at defined intervals and at sufficient frequency to determine whether both quality system activities and the results of such activities comply with quality system procedures, that these procedures are implemented effectively, and that these procedures are suitable to achieve quality system objectives.
- Quality control: a set of activities or techniques whose purpose is to ensure that all quality requirements are being met. To achieve this purpose, processes are monitored and performance problems are solved.
- Quality improvement: anything that enhances an organization's ability to meet quality requirements.
- Quality assurance: a set of activities whose purpose is to demonstrate that an entity meets all quality requirements. Quality assurance activities are carried out to inspire the confidence of both customers and managers, confidence that all quality requirements are being met.
- Quality planning: a set of activities...
