Page 186 - Design for Six Sigma a Roadmap for Product Development

Design for Six Sigma Project Algorithm 159

and 5.13. The dependent variables in the transfer functions are opti-
mized by either shifting their means, reducing their variations, or
both. This can be achieved by adjusting their mapped-to-independent
variables means and variance. This optimization propagates to the
customer domain via the other high-level transfer functions in the
design mappings resulting in increased customer satisfaction.
Design scorecard documents record and assess quantitatively the
DFSS project progress, store the learning process, and exhibit all crit-
ical elements and performance of a design (CTSs, FRs, DPs, and PVs).
Scorecards have many benefits, including showing gaps for improve-
ments relative to customer attributes, documenting transfer functions
and design optimization, predicting final results, enabling communi-
cation among all stakeholders in the project, and evaluating how well
the design is supported by manufacturing and production processes at
component and subassembly quality levels. We suggest documenting
the transfer functions belonging to the same design hierarchy in the
mapping in one scorecard, thus avoiding having one for each design
element or requirement in the physical structure.

5.9 Assess Risk Using DFMEA/PFMEA
(DFSS Algorithm Step 8)

An FMEA can be described as a systemized group of activities
intended to

1. Recognize and evaluate the potential failures of a design and its effect.
2. Identify actions which could eliminate or reduce the chance of the
potential failure occurring.
3. Document the process.

It is complementary to the design process to define positively what a
design must do to satisfy the customer.
The failure mode–effect analysis (FMEA) [see AIAG (2001)] helps
the DFSS team improve their project’s product and process by asking
“What can go wrong?” and “Where can variation come from?” Design
and manufacturing or production, assembly, delivery, and other ser-
vice processes are then revised to prevent occurrence of failure modes
and to reduce variation. Specifically, the teams should study and com-
pletely understand physical and process structures as well as the sug-
gested process mapping. This study should include past warranty
experience, design and process functions, customer expectations and
delights, functional requirements, drawings and specifications, and
process steps. For each functional requirement (FR) and manufactur-
ing/assembly process, the team asks “What can go wrong?” Possible