Design for Six Sigma I

This course covers the design of specific solutions that achieve 6-sigma process capability. Designing such process capability into a solution requires an additional set of rigor and control beyond that accomplished on most improvement projects. DFSS covers an integrated deployment of business requirements, functional specifications, system design, and operational implementation that allows critical design variables to be prioritized and optimized across each layer. One view of DFSS is that it applies DMAIC improvement to each level of the DFSS design, optimizing the cross-level integration and interaction. Another view is that DFSS builds in self-correcting mechanisms by emphasizing the gap between 3-sigma control limits and 6-sigma specification limits. (4 days, $20,000, Required prerequisite: Six Sigma Improvement II, Recommended prerequisite: Introduction to Requirements Engineering or Introduction to Quality Engineering)

Process Coverage

Design for Six Sigma is not independent of the Six Sigma Improvement model. Opportunities for new systems, or components of systems, arise out of the DMAIC analysis process. Implementing a system using DFSS always takes place in the context of the DMAIC-driven improvement and always results in an implementation that is sustained by DMAIC-derived controls, even if the DMAIC efforts are not explicitly associated with the DFSS effort.

Lifecycle Coverage (DFSS)

Design for Six Sigma is based on an Identify-Define-Develop-Optimize-Verify (IDDOV) lifecycle that emphasizes identifying and designing innovative solutions against opportunities defined during traditional DMAIC initiatives. The DMAIC lifecycle is viewed as the driver of scope and direction.

This course covers the entire IDDOV lifecycle, but emphasizes activities toward the front end. Tool coverage is complete enough to build a comprehensive and integrated design, but optimization and tuning of that design is deferred until the Design for Six Sigma II course.

  1. Identify the Opportunity - Driven by the measurement and analysis phases of DMAIC, identification activities clarify particular product or service opportunities that can be implemented to help solve the problems being addressed by the DMAIC activity. Whether the need is for a comprehensive systems solution, or a collection of independent components that collectively will solve the problem, their identification initiates the DFSS process.

  2. Define the Requirements - Comprehensive requirements engineering is a central theme of DFSS, with integrated models developed for Customer Needs, Business Processes, Functional Systems, Systems Designs, and Operational Support. Emphasis is placed on defining exhaustive requirements with a high level of control and quantification. Customer needs define requirements priorities, leading to a requirements management model that might implement as a single solution, or a series of releases planned over time.

  3. Develop the Concept - As requirements progress toward implementation details, various conceptual solutions are continuously being identified and evaluated as stronger and stronger alternatives emerge and drive subsequent engineering activities. Evaluation might include various forms of experimentation, simulation, or prototyping to better understand design parameters and performance relationships.

  4. Optimize the Design - Once a best conceptual solution has solidified in response to the prioritized and allocated requirements, the design parameters and performance relationships are driven toward optimal values using further experimentation and analysis. Critical design variables and functional dimensions are designed toward maximizing satisfaction and performance.

  5. Verify Conformance - Once a systematic and rigorous design has been optimized, it must be verified and validated against the original requirements, as well as the critical-to-quality control values that have been established at each level of the overall design. The quantification of requirements must be assured, followed by the review and approval of stakeholders to be impacted by the design.

Other common DFSS lifecycle models are also discussed, including Define-Measure-Analyze-Design-Verify (DMADV) and Define-Model-Optimize-Verify-Control (DMOVC). These lifecycles aim to accomplish goals similar to those of the IDDOV lifecycle. They are typically seen in environments trying to implement DFSS on a standalone basis, independent of DMAIC. We believe that DFSS works best if it attempts to integrate the findings and tools of DMAIC into a comprehensive design. DMAIC measurement and analysis activities always lay the groundwork for effective design, and so we integrate them to illustrate and maximize that effect.

Tool Coverage

  1. Voice of the Customer (VoC) - While Voice of the Customer was introduced in DMAIC as a general process for gathering and validating requirements, when integrated into DFSS it is tailored to the various layers that constitute a whole system design. Overall customer needs become differentiated from their preferences for functional capability or design performance targets.

  2. House of Quality (HoQ) - The set of matrices that constitute the House of Quality allow for the definition, analysis, prioritization, and quantification of intersecting requirements. The rows define what's needed, and the columns define how the need will be met. The context in which the HoQ is built (e.g. analysis, design, operations) determines the types and depth of entries along these two dimensions.

  3. Quality Function Deployment (QFD) - QFD is the primary integration tool of DFSS because it forms the backbone that ties all other Six Sigma tool results together. The QFD is built as a series of related HoQ matrices, where the columns of one matrix become the rows of the next. Beyond integration of the multiple levels of design detail, the QFD provides for prioritization and quantification of requirements and design parameters at all levels of the design model, and assures traceability from implementation back to the original voice of the customer.

  4. Pugh Concept Selection - Each time a design team transitions from one level of the QFD to the next, the columns of the previous level become the rows of the next. Where does the subsequent set of columns come from? Pugh supports the identification of multiple alternatives and supports the negotiation of a best hybrid alternative. The chosen alternative is considered least vulnerable to disruption, and becomes the columns of the next layer of QFD.

  5. Design Failure Mode and Effect Analysis (DFMEA) - Just as the Process FMEA improved the design and specification of processes in DMAIC, the Design FMEA is used to continuously improve the quality of the design that is emerging through the QFD.

  6. Design for "X" - Any number of factors might be relevant to the definition of quality during a systems initiative. DFSS involves being able to incorporate a variety of factors "X" into a design, working toward a solution set that optimizes their interaction against customer needs and requirements. Common "X" factors in this course include Testability, Reliability, Maintainability. Other "X" factors are covered in Design for Six Sigma II course.


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