Page 29 - Design for Six Sigma a Roadmap for Product Development

Quality Concepts 7

order to deliver the product’s intended functions. By using axiomatic
design terminology, product design is a mapping from function space to
design parameter space. Therefore, the key task for quality in design is
to ensure that the designed product is able to deliver the desired prod-
uct functions over its useful life. The quality methods used in this stage
include robust design (Taguchi method) (Taguchi 1986), design of
experiment (DOE), response surface methods (RSMs), Design for X,
axiomatic design, TRIZ, and some aspects of reliability engineering.

1.2.5 Stage 4: Manufacturing process
preparation/product launch
The fourth stage is manufacturing process preparation/product
launch. During this stage, the manufacturing process design will be
finalized. The process will undergo testing and adjustment, so there is
another set of build-test-fix cycles for the manufacturing process. After
iterations of cycles, the manufacturing process will be validated and
accepted and installed for production. Using axiomatic design termi-
nology, this stage is a mapping between product design parameters to
process variables.
For quality assurance, clearly the key task for this stage is to ensure
that the manufactured product should be consistent with product
design; that is, the product design on paper or computer can be real-
ized in the manufacturing process. The process is able to produce the
real product consistently, economically, and free of defects. The quality
methods used in this stage include robust design, DOE, manufactur-
ing troubleshooting and diagnosis, and the Shainin method.

1.2.6 Stage 5: Production
The fifth stage is the full-scale production. In this stage, the product
will be produced and shipped to the market. Some parts or subassem-
blies might be produced by suppliers. During production, it is very
important that the manufacturing process be able to function consis-
tently and free of defect, and all parts and subassemblies supplied by
suppliers should be consistent with quality requirements.
For quality assurance at this stage, the key task is to ensure that
the final product is in conformance with product requirements; that is,
all products, their parts, subassemblies should be conformant with
their designed requirement; they should be interchangeable and con-
sistent. The quality methods used in this stage include statistical
process control (SPC), quality standard and acceptance inspection for
suppliers, and production troubleshooting and diagnosis methods.
The combined activities from stage 1 through stage 5 is also called
the product development cycle.