A FEW WORDS ABOUT

QFD





QFD is a step-by-step technique for ensuring that the 'Voice of the Customer' is heard throughout the product development process so that the final product fully meets customer requirements. The first step of QFD is to identify and capture customer requirements, wishes, expectations and demands. In the following steps, these are translated by multi-functional product teams into the corresponding technical specifications. QFD uses a series of related matrices and tables as the tool for translating the voice of the customer first to design specifications, then to more detailed part characteristics, then to show the necessary process and technology characteristics, and finally to show the specific operational conditions for the production phase. The result is that, before the design phase is complete, the complete product development and production process has been defined and agreed, and the voice of the customer can be followed through the different steps. In doing this, the team members develop a shared and documented view of the key information describing the product and the overall process.

The most widely used QFD model for product development is that developed by the American Supplier Institute. It involves four linked matrices used for product specification, component specification, manufacturing process capability specification, and production rules specification. Each new matrix takes information from the preceding matrix as its starting point.

The matrices can be traversed forwards and backwards. For example, by backing up the matrices from a production rule, the customer requirement which gave rise to the rule can be traced. The linked matrices are a deployment mechanism through which several business functions contribute to turning a customer requirement into a well defined and reproducible product. QFD is a very useful support tool to help multi-functional teams manage the large quantities of information necessary to make quality decisions.

In the first step, a matrix is built showing the relationships between customer requirements (generally expressed in non-technical language) and the corresponding product characteristics expressed in measurable, technical terms. The intensity of the relationship at each intersection of the matrix is then defined, bringing to light relative priorities and potential conflicts. Additional tables are added to show the target numbers for each of the measurable characteristics, and the corresponding numbers for competitive products. Further matrices link requirements to product functionality, and show how the overall product will be built up from parts and subsystems. Then, additional matrices are developed for the detailing of each part, the process and technology characteristics, and the operating procedures and conditions for the production phase. The interrelated tables and matrices develop to form what is often called a 'Quality House' (due to the roof-like shape of some of the tables). The ten areas from which the House is built are :

To ensure that the final matrices and tables are not too large and numerous, a certain amount of focusing on the most important requirements is carried out at each step.

QFD is not a rigid methodology. It is a decision support tool, and as such is most useful when people throughout the company contribute to the definition of the information content of the matrices. The matrices selected to solve a particular problem which is important to the company will depend on the particular problem. In some cases, a single matrix may suffice, but usually the resolution of a complex problem requires looking at it from different angles : cost, reliability, technology, tooling requirements, manufacturing process rules, etc., which are in most cases related, and spawn new matrices and tables. A key concept of QFD is that of ranking the importance of the information elements and working on those which are the most important, or difficult, or new. In this way problems are reduced to a manageable size.

Even so, a typical House of Quality of 20 rows x 20 columns can contain over 1320 distinct pieces of information.

When conducting a QFD study much time can be saved by having efficient access to the information required to construct the matrices and tables e.g. market research results, functional analysis, competitive analysis, test results, benchmarking, fmeca, design libraries, design rule data bases, field reliability, regulatory data base, specifications libraries, etc. This information may reside in disparate systems and the benefits of bringing the information sources under the control of an EDM/PDM system are great.

Among the main benefits resulting from the use of QFD are:

Capturing the 'Voice of the Customer'
QFD captures the Voice of the Customer, isolating it from reinterpretation. QFD brings understanding of the competition, it leads to products and services which give total customer satisfaction, and it builds the knowledge base of the company.

Teamwork
QFD enforces teamwork, establishes common objectives and facilitates consensus. Cultural barriers are reduced and the team members learn from each other.

Improved planning
The project plan is more in phase with customer requirements, priorities are established correctly and resources better employed. Planning problems due to rework are greatly reduced. Deployment.

The 'Voice of the Customer' becomes the reference within the company by which the activities and players in the development process are welded together.

The exact process of implementation of QFD will depend on the objectives of each particular company. However a typical process would be :
QFD ensures that the voice of the customer is heard throughout the steps of the product development process, and is heard in language appropriate to each step. It maintains coherence and consistency between the various stages of the product development process, and among the people involved. It makes sure the overall design is correct and documented at the beginning of the development process (rather than correcting and documenting it in production). QFD was first used by Mitsubishi's Kobe Shipyards in the late 1960s. QFD users claim it has helped them reduce design cycle time by one third or one half, reduce the number of engineering changes by half, and greatly increase the new product introduction rate.

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Copyright 1998 by John Stark