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Quality function deployment (QFD) is a method developed in Japan beginning in 1966 to help transform the voice of the customer [VOC] into engineering characteristics for a product. Yoji Akao, the original developer, described QFD as a "method to transform qualitative user demands into quantitative parameters, to deploy the functions forming quality, and to deploy methods for achieving the design quality into subsystems and component parts, and ultimately to specific elements of the manufacturing process." The author combined his work in quality assurance and quality control points with function deployment used in value engineering.
Contents
Process
The QFD method identifies and classifies customer desires, identifies the importance of those desires, identifies engineering characteristics which may be relevant to those desires, correlates the two, allows for verification of those correlations, and then assigns objectives and priorities for the system requirements. This process can be applied at any system composition level (e.g. system, subsystem, or component) in the design of a product, and can allow for assessment of differently level abstraction systems based on the output of QFDs matrices assessed for those system levels. The output of the method is generally a matrix with customer desires on one dimension and correlated nonfunctional requirements on the other dimension. The cells of matrix table are filled with the weights assigned to the stakeholder characteristics where those characteristics are affected by the system parameters across the top of the matrix. At the bottom of the matrix, the column is summed, which allows for the system characteristics to be weighted according to the stakeholder characteristics.
System parameters not correlated to stakeholder characteristics, may be unnecessary to the system design and are identified by empty matrix columns, while stakeholder characteristics (identified by empty rows) not correlated to system parameters indicate "characteristics not address by the design parameters". System parameters and stakeholder characteristics with weak correlations potentially indicate missing information, while matrices with "too many correlations" indicate that the stakeholder needs may need to be refined.
Areas of application
QFD is applied in a wide variety of services, consumer products, and military needs.
Fuzziness
The concepts of fuzzy logic have been applied to QFD ("Fuzzy QFD" or "FQFD"). A review of 70 papers in 2013 by Abdolshah and Moradi found a number of conclusions: most FQFD "studies were focused on quantitative methods" to construct a QFD matrix based on customer requirements, where the most-employed techniques were based on multiple-criteria decision analysis methods. They noted that there are factors other than QFD relevant to product development, and called metaheuristic methods "a promising approach for solving complicated problems of FQFD."