Design for Six Sigma—The DMADV Roadmap contrasted with the DMAIC Process


Six Sigma is a process for improvement of manufacturing or business processes. It shows how to improve processes that create an already existing product or service. But what if you want to create a new existing product or service? How can Six Sigma help on the design, rather than on the manufacturing side of things?

1. DMAIC Process

First, let’s review the Six Sigma process for manufacturing, which goes in the following steps: Define, Measure, Analyze, Improve, and Control or DMAIC.

With the principle of kaizen or continuous improvement in mind, these steps form a continuous cycle as shown below.

Here are the DMAIC steps defined for the manufacturing process.

Six Sigma Step

Definition

1. Define Define customer and organizational requirements. Select the “Y” responses to be improved.
2. Measure Measure what is critical to quality, map the process, establish measurement system and determine what is “out of specification” or unacceptable. Measure the “Y” response variable.
3. Analyze Now develop a baseline (the process capability), set objectives, identify the “X” independent variables that are the root causes of defects or “out of specification” measurements of the “Y” response variables.
4. Improve Improve the process by reducing variability in the process or eliminating the cause of the defects or out of spec measurements.
5. Control Establish a system to monitor and control the process to sustain the improvements in the long term.

2. DMADV Roadmap

In DMADV, there are actually six steps rather than five in the following formulation that has “Optimize” as step 5 out of 6 (so I guess it could be referred to DMADOV).

The DMADV roadmap steps are defined as follows, with examples of what is in each step.

Roadmap Step

Definition

1. Define Evaluate and prioritize design objectives.  Define your design project goals by doing an analysis of customer needs and general risk assessment; create design team.
2. Measure Do technical and competitive product analysis (including regulatory-based requirements.  Capture Voice of Customer (use QFD or other methodology). Refine general risk assessment, and create design project schedule.
3. Analyze Identify design priorities.  Develop Critical to Quality features or CTQs. Finalize risk assessment.
4. Design Finalize design including CTQs.  Develop prototypes, and review design in light of CTQs.
5. Optimize Review CTQs, test design tolerances, and optimize design.
6. Verify Compare product to initial design objectives, complete development documentation, send design to operations.

I mentioned QFD because it was the subject of a previous post, and the House of Quality tool shows visually the method of first developing a list of customer requirements, and then weighting the design features based on how well they fulfill these customer requirements. The top-ranking design features would therefore be considered Critical to Quality features or CTQs. The QFD approach also includes the target specifications as well (in the “basement” or “foundation” of the House of Quality).

The risk assessment mentioned in several steps above can be done with the Failure Mode and Effects Analysis, which is the subject of another previous post.

3. Conclusion

In this way there is a Six Sigma “roadmap” that can be utilized in the design phase of a product or service. I hesitate to call it a Six Sigma design “process”, because in reality a Six Sigma process on the manufacturing side of things can only be done when a process is already in control or stable. That incidentally, is the reason why some consultants I have talked to consider the use of Six Sigma in the healthcare field to be perhaps a little premature because many processes are not yet well controlled.

On the other hand, doing the DMADV (actually DMADOV, if you include “optimize” as the 5th step out of 6) roadmap will make the subsequent Six Sigma process on the manufacturing side easier, because you have already done an extensive study of the various technical requirements or design features which should make any cause-and-effect analysis of potential defects a lot easier to do.

This concludes the final portion of the Design for Six Sigma or DFSS that is part of the Six Sigma Green Belt Body of Knowledge. The next posts in this series will start covering the D or Define of DMAIC.

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