Page 55 - Design for Six Sigma a Roadmap for Product Development

Six Sigma and Lean Fundamentals 33

Six Sigma and process capability. The concept of process capability
indicates that in order to achieve high process capability, the following
two tasks must be accomplished:
1. The actual process mean performance should be as close to ideal
performance level, or target value, as possible.
2. Process performance spread should be small relative to functional
limits.

Therefore, it is again a “Do the right thing, and do things right all the
time” rule. Accomplishing Six Sigma process capability is a very diffi-
cult but necessary task. If a process can produce good performance “on
average,” for example, a company can make a good profit some years
but could lose a lot in other years, then this inconsistency will severely
damage the image and morale of the company.
Six Sigma is a strategy that applies to all the quality methods and
process management available to a full process life-cycle implementa-
tion. The goal for any Six Sigma project is to make the process able to
accomplish all key requirements with a high degree of consistency.
There are two ways to do this: Six Sigma process improvement and
design for Six Sigma (DFSS).

Six Sigma process improvement. Six Sigma process improvement is
actually the Six Sigma method that most people refer to. This strategy
does not involve any changing or redesigning of the fundamental
structure of the underlying process. It involves finding solutions to
eliminate the root causes of performance problems in the process and
of performance variation, while leaving the basic process intact. If we
refer to the process life cycle illustrated by Fig. 2.7, Six Sigma process
improvement applies only to stage 4 and after.

Design for Six Sigma (DFSS). Design for Six Sigma is a Six Sigma
approach which will involve changing or redesigning of the fundamen-
tal structure of the underline process. If we refer to the process life
cycle illustrated by Fig. 2.7, DFSS applies to stages 1 through 3.
Therefore, it is an upstream activity. The goal of DFSS is to design or
restructure the process in order for the process to intrinsically achieve
maximum customer satisfaction and consistently deliver its functions.
Design for Six Sigma is needed when

■ A business chooses to replace, rather than repair, one or more core
processes
■ A leadership or Six Sigma team discovers that simply improving an
existing process will never deliver the level of quality customers are
demanding