Although the founding of QFD is based on evaluation matrices, as containers for the planning activities, the concept of QFD can in fact be implemented without using any single matrix at all. The spirit of QFD lays in a team-based process for maintaining visibility and integrity in the VOC, when translating the characteristics in one domain into characteristics in another domain. In some cases, we could justifiably translate and transfer the requirements in a team discussion session, off paper. We should do so in the understanding to the QFD project team that they are about to lose the opportunity of the House of Quality bringing out new learning – about the development focus and priorities.
The above one-sheet QFD chart, also containing a project management overview and design documents index, was developed to help shortcut the 4-phase planning tool for a particular organisational context. The product developer had prior practices of conventional QFD and years of VOC experience from supplying 2 related products into the market.
Nasal prongs with soft cushion seals
The one-sheet deployment tables provide an at-a-glance total planning overview on a single sheet of A3 paper. This proves easy for visualising a direct link between the original customer input requirements flowing in on the left-hand side and a production implementation plan flowing out on the right. The area below the 4 tables indicates the existence of project related documents and records of applied tools – such as FMEA, for example. The references are arranged on an approximate time line, which indicates the stage at which the documents are produced.
In this chosen QFD approach, customer requirements are in the first instance weighted for their “Competitive opportunity”, where L = Low, M = Medium, H = High. We are using a relatively modest addition here. This is to avoid excessively distorting customer requirements. The “Resulting importance”, to take forward, is produced by adding 0 to the customer “Input importance” for a low (L) score, 2 for a medium (M) score and 3 for a high (H) score.
The transfer of importance values between the stages is performed by a simple line drawing, representing ‘strong’ or ‘weak’ relationships. The input importance into the design requirements are arrived at in a consensus-based team discussion, considering the various strong and weak relationships to customer requirements. The team then judges a representative input importance score from the links. The multiple lines can look a little busy; but the scoring is actually quick and easy when performed just after the lines are drawn, while their rationale remains fresh in the team memory.
In the design requirements stage we weigh the input importance by “Difficulty” and “Company strategy”. Again, we use the scores L, M or H. The resulting importance, this time, is derived by multiplying the input importance by both the difficulty and the strategy weights, where L = 1, M = 2 and H = 3. For example, the resulting score for the requirement that our design can perform as both “Generator and prong variants” becomes 8 x 3 x 3 =72. The resulting importance facilitates planning – i.e. resource and time allocation – for the product design development, which now takes place in between the second and third table (see project timeline above the chart). The designers will refer back to the original customer input importance when selecting their technical solutions.
Once we have completed our product design work, the product parts and their target values are entered into the third table. Again, we drawn lines to indicate relationships and transfer the importance values. Individual parts may have multiple target parameters. We try best possible to judge how much of the part input importance value relates to each the individual targets. For example, “Prong cushion” has an importance value of 150. The “Ball shape” parameter relates to about 120 of the 150. The “Viscoelastic resilient” relates to about 90 of the 150. The resulting importance facilitates planning – i.e. resource and time allocation – for the process design, which now takes place in between the third and fourth table. One particularity in this project is that the prong cushion foam moulding process is outsources to a specialist sub-manufacturer. Although we do now not produce this part internally, its quality characteristics and importance values form basis for the negotiations, specification and process validation that we put in place with the contractor.
This one-sheet QFD case study is described in more details in my book ‘Quality Innovation: A QFD approach’. A full preview can be read online at lulu.com (click here, requires FlashPlayer, go to pages 206 to 222).