Design for Six Sigma

Contributing Author: Greg Swartz

Design for Six Sigma (DFSS) is the application of Six Sigma principles to the design of products and their manufacturing and support processes. Often the acronym DMADV (define, measure, analyze, design and verify) is used synonymously with Design for Six Sigma. While DFSS can apply to the design or a product, manufacturing process, business process or service, our focus in the paper is the development of new products.

HIGHLIGHTS OF DFSS INCLUDE
1. Determining Critical to Quality (CTQ) attributes most important to the customer
2. Enhanced Process Capability: What your process can deliver
3. Reduce Variation to a Minimum in final product output
4. Stable Operations: Ensuring consistent, predictable processes and improve what the customer sees and feels
5. Designing performance excellence to meet customer needs and process capability

SITUATION

In this dynamically changing world, product cycles are being reduced drastically. Just a few years ago, it was not uncommon to have 18-24 month product cycles, whereas today, we are seeing 3-6 month product life cycles. To meet these demanding requirements product developers have to develop products in the shortest amount of time that are safe, reliable, and competitive.

VALUE TO YOUR ORGANIZATION

Using the methods of DfSS, we can assure the design of a product with the highest quality and reliability in the shortest amount of time.

RELIABILITY INTEGRATION

An example of Reliability Integration during Software Reliability is as follows:

Design for Six Sigma is a methodology that calls upon many of the fundamental design tools such as Design of Experiments (DoE), Failure Modes and Effects Analysis (FMEA), Design for Reliability (DfR), and Design for Testability (DfT). Using DfSS in conjunction with our Reliability Plan, we will know when to use which tool and how to integrate each together to produce a reliable product in the shortest amount of time.

BACKGROUND

Six Sigma initiatives have achieved recent popularity because of their bottom line focus versus previous TQM initiatives which often tended to be unfocused.

In one respect, DFSS is the repackaging of many quality tools and techniques appropriate for product development into a framework. This framework contains many of the same elements as the Advanced Product Quality Planning (APQP) process used in the automotive industry.

American Society of Quality's Body of Knowledge on Design for Six Sigma (DFSS) includes the following:
1. Quality Function Deployment (QFD)
2. Robust design and processes (includes functional requirements)
3. Failure Mode and Effects Analysis
4. Design for X (DFX)
5. Special design tools

General Electric originally defined the principles of DFSS as the following:
1. Disciplined CTQ flowdown
2. Controlled design parameters
3. Product performance modeled and simulated
4. Designed for robust performance and producibility
5. Functionally integrated product development
6. Quality "designed in"

METHODOLOGY

The following represents our more specific list of elements of the DFSS framework:
1. Understand real customer needs through voice of the customer (VOC) analysis.
2. Use Quality Function Deployment (QFD) to translate customer needs into critical technical characteristics of the product and into critical to quality (CTQ) characteristics of the product and process.
3. Focus on designing for the lifecycle to minimize lifecycle costs, value analysis and target costing and to enhance reliability with Design for Reliability (DfR) and Design for Testability (DfT).
4. Mistake-proof the product and process.
5. Perform Failures Modes and Effects Analysis (FMEA) or Anticipatory Failure Determination (AFD) to identify potential failures and take corrective action to mitigate or prevent those failures. FMEA and AFD apply to both the design of the product and the design of the process.
6. Develop capable manufacturing processes and select processes that are capable of meeting the design requirements, especially with CTQ parameters.
7. Use Design of Experiments (DoE) or Taguchi Methods to optimize parameter values and reduce variation, in other words, develop a robust design.
8. Verify and validate that the product design will meet customer needs with peer reviews, checklists, design reviews, simulation and analysis, qualification testing, production validation testing, focus groups and market testing.
9. Measure results with DFSS scorecard; estimate sigma - do results meet quality target?

CASE STUDIES

The following case studies and options provide example approaches. We will tailor our approach to meet your specific situation.

Using DfSS with a Medical Company making an Infusion Pump

A Medical company was re-designing a product and needed to get the product out in the shortest amount of time, but their reputation was on the line because customers were expecting a much higher level of reliability than the previous generation. We turned to the methodology of DfSS and linked it in with the Reliability Plan to know which DfSS tools to use and how to integrate each of the tools together to maximize the reliability payback while shortening the development time as much as possible. We ended up deploying FMEA across the entire product, Design of Experiments early on for the new tolerance-critical assemblies, and Accelerated Life Testing on the new mechanical components of the product. The results were that we developed the product in half the time of the original and the initial product defect rate was 1/4 of the rate from the previous generation product.

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1) Apollo Root Cause Methodology
2) Fishbone
3) 5 Why's
4) CNX diagrams - Control, Noise, X=No Control
5) Cause and Effect Diagrams
6) DMAIC - Define, Measure, Analyze, Improve, Control Methodology
7) Design of Experiments - DOE
8) Control Charting
9) Pareto Charting
10) TOPS 8D Methodology

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DfR Solutions has world-renowned expertise in applying the science of Reliability Physics to electrical and electronics technologies, and is a leading provider of quality, reliability, and durability (QRD) research and consulting for the electronics industry. The company's integrated use of Physics of Failure (PoF) and Best Practices provides crucial insights and solutions early in product design and development and throughout the product life cycle. DfR Solutions specializes in providing knowledge- and science-based solutions to maximize and accelerate the product integrity assurance activities of their clients in every marketplace for electronic technologies (consumer, industrial, automotive, medical, military, telecom, oil drilling, and throughout the electronic component and material supply chain). For more information visit www.dfrsolutions.com.

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Senior Reliability Consultant

Ops A La Carte's newsletter goes out to over 15,000 subscribers. If you would like to put a job opening in next quarter's "Reliability News", email us via our Job Openings Contact Form or call at (408) 654-0499.