Written by Muqi Wulan
Reading through the materials for L1 and L2, you will have the basic knowledge on QFD and its House of Quality (HoQ). QFD is a graphical method of bridging the voice of the customer and technical features through the structural HoQ. In a sequential way, customer requirements are translated into engineering characteristics which are assigned target values to be achieved. The most comprehensive HoQ is configured with 8 featured “rooms” or sections as shown in Figure 1.
Figure 1 – The HoQ converts customer requirements into engineering characteristics
(Dieter and Schmidt 2009: 101)
Not all design projects will call for the construction of a HoQ in its full configuration (Rooms 1 to 8) as in the above figure. The basic translation of customer requirements (CRs) into engineering characteristics (ECs) can be accomplished with a HoQ only including Room 1, 2, 4 and 5 in Figure 2. An example of the HoQ with minimum configuration constructed for the CD case is illustrated in Figure 3.
Figure 2 – Simplified version of a HoQ (Dieter and Schmidt 2009: 103)
Figure 3 – Simplified HoQ as applied to CD case (Dieter and Schmidt 2009: 105)
As described in the materials at L1 and L2, QFD aims to provide developers with a systematic method for “deploying” the voice of the customer into product design. It is the original intent of QFD to assist in the design of products (Cohen 1995: 21). The methodology is of great value in bridging the communication gap between the customer and the personnel who is responsible of designing and engineering the product to be manufactured, distributed and maintained in the field. Actually the House of Quality in QFD can help the users organising, controlling and carrying out more of the design process (ReVelle, Moran, and Cox 1998: 55). The American Supplier Institute’s Four Phase approach and the GOAL/QPC Matrix of Matrices approach employ multiple HoQs to support more complex product development process. Therefore QFD is a linked, sequential and transformational process. The first set of inputs strongly influences all downstream transformations. The QFD process enables infusing the voice of the customer into every aspect in the product design and development process.
Figure 4 – Four phases of QFD (ReVelle, Moran, and Cox 1998: 56)
The next example is still of chocolate chip cookies (QFD Online 2011). Three HoQs are used to describe a process more extensive than the one at L1 and L2. The process is divided into three phases: product planning, production planning, and parts deployment. All the three phases are sequentially connected, as shown in Figure 3.5. Each individual phase is depicted by one single HoQ.
Figure 5 – Three phases of QFD for chocolate chip cookies
1. Product planning: mapping customer needs to functional requirements (Figure 3.6).
2. Production planning: mapping functional requirements to production attributes (Figure 3.7);
3. Parts deployment: mapping production attributes to part/material deploying (Figure 3.8).
Figure 6 The first HoQ – product planning for chocolate chip cookies (QFD Online 2011)
Figure 7 – The second HoQ – production planning for chocolate chip cookies (QFD Online 2011)
Figure 8 – The third HoQ – parts deployment for chocolate chip cookies (QFD Online 2011)
Summary
QFD is a method for structured product planning and development that enables a development team to specify customer needs, and systematically evaluate each engineering capability of the proposed product or service in terms of its impact on meeting those needs (Cohen 1995: 11).
As the core structure of QFD, the House of Quality (HoQ) needs to be constructed in a step-by-step process in accordance to the fully configured “rooms” of the HoQ. Depending on application circumstances and project requirements, the configuration of the HoQ allows to be simplified and only includes main featured “rooms”.
QFD extends to use multiple HoQs and support cross-functional teams to get involved in the all phases of product design and development.
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Selected References
Cohen, L. (1995) Quality Function Deployment; How to make QFD work for you. Reading: Addison-Wesley
QFD Online (2011) House of Quality (QFD) example [online] available from <http://www.qfdonline.com/qfd-tutorials/house-of-quality-qfd-example/> [26 July 2011]
ReVelle, J., Moran, J., and Cox, C. (1998) ‘QFD and product design’. in The QFD handbook. ed. by ReVelle, J., Moran, J., and Cox, C. New York: John Wiley & Sons, 55-67