6.1 Introduction

In the context of Design for Six Sigma (DFSS), quality function deployment (QFD) is best viewed as a planning tool that relates a list of delights, wants, and needs of customers to design technical functional requirements. With the application of QFD, possible relationships are explored between quality characteristics expressed by customers and substitute quality requirements expressed in engineering terms (Cohen 1988, 1995; Clausing 1994). In the context of DFSS, we will call these requirements critical-to characteristics, which include subsets like critical-to-quality, and critical-to-delivery characteristics. In the QFD methodology customers define the product using their own expressions which usually do not carry any significant technical terminology. The voice of the customer (VOC) can be discounted into a list of needs used later as input to a relationship diagram, which is called QFD's house of quality.

Knowledge of customer needs is a must requirement in order for a company to maintain and increase its position in the market. Correct market predictions are of little value if the requirements cannot be incorporated into the design at the right time. Critical-to-innovation and critical-to-market characteristics are critical because companies that are first to introduce new concepts at six-sigma (6 ?) levels usually capture the largest share of the market. Wrestling market share away from a viable competitor is more difficult than wrestling market share away from a first producer into a market. One major advantage of a QFD is attainment of the shortest development cycle, which...