Quality by Design

Quality by Design (QbD) is a simple concept. It posits that quality cannot be inspected
into products, but rather is created by processes. Witness the near-constant
retooling and reinvention of manufacturing processes in the automotive,
semiconductor manufacturing and electronics industries who started with Six
Sigma now extending to and fully embraced QbD. The evolution to QbD is a
logical next step since QbD is built on top of Six Sigma and extends into the
design space.

Continual improvement drives Quality

The attitude towards defects should be one of avoidance, prevention and resolution. The aim should be to do things right the first time anyplace, anywhere and
anytime in the product quality lifecycle implementation. When this is applied
throughout the process, the defects will be reduced dramatically and improve the
output of any process. The cost to resolve errors is referred to as the ‘Cost
of Quality’, the further downstream defects or design errors are detected the
more costly they will become to solve. In all cases, defects should be
corrected during design or manufacturing, they should never reach the customer
with the risk of product recalls or damage/harm to the customer. Cost to
correct errors grows exponentially when they are detected later in the process;
it clearly puts the focus on the design. With this in mind, well planned products
with Quality involvement in design as well as in production, will cost less to
manufacture and to maintain. In addition, it will also cost the customer less to own or buy them and will improve satisfaction for the product or service.

Six Sigma principles and the tools are drivers to define and quantify quality
enhancements. The goal is to drive down defects, enhance customer satisfaction
and contribute to the financial results. Key to Six Sigma is a quantitative approach to support the results of the achievements; a variety of statistical tools are used. This process is completely data driven. Computerized systems supporting the storage and analysis of the measurements are critical, both for speed and compliance. A production facility running at a Six Sigma level is close to perfection, meaning that only 3.4 defects per million opportunities or units will be recorded.

Many processes may not reach this level of variation despite the efforts; three or
four level sigma may be the best that can be reached. When you hit this sigma
wall, no process improvements can be further made and the law of diminishing
returns takes over. In these cases there could be a fundamental problem in the
design of the product or service preventing further improvements. Redesign of
the product may be the only possibility to improve the quality level further.

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