4-phase QFD model (part 2 of 3)

Evolved 4-phase QFD model

In my last post I identified that QFD has often been mistaken as the process of building a House of Quality (HoQ). We do not develop the product toward a HoQ, but instead the HoQ establishes the plan for the development work to follow. We in fact spend a proportionally very small amount of time in the HoQ.

The Evolved 4-phase model now depicts how the HoQ planning step proceeds the design and development step, in each of the 4 phases. As mentioned in my earlier post, the step-by-step depiction does not infer a ‘process over-the-wall’ approach. Therefore, note the 2 dotted arrows between product design, process design and production planning, which are used to indicate an information transfer between what tends to be concurrent design activities – as opposed to represent sequential process flow steps.

Planning step

The HoQ explained in my earlier post sets out a plan, which matches the ambition for the development project.

The QFD approach may emphasise development work by different functional groups at different stages, but it is planned under the same umbrella project where everyone in the project team have oversight of and contributes to the end-to-end master plan. This contrasts a traditional over-the-wall planning approach, where designers interpret and develop the product in isolation of other organisational functions.

The QFD planning activity is about the collective team accepting the output from a previous phase and then deploying it into fresh specification objectives, for the following phase activity that is currently about to commence. The plan addresses:

    1. What source requirements are we to address?
    2. How should we go about addressing them?

Normally, for very simple design problems, we can perform this deployment in a mental exercise. However, as the complexity of unknowns and contradicting multiplicity sets in, we will need a system for ensuring that we best predict the causal argument for our actions. Individual gut feel is important, but it is better to produce a robustly evidenced plan for the more complex phases in a development project. Selecting an appropriate depth of planning relies on our understanding of risk-based thinking.

The ‘plan’ step is where the QFD matrix tool adds strength. The deployment matrix, which in some form is called the ‘House of Quality’, is partly constructed from what we obtained as the outputs in the previous phase. This assures the 4 phases are interlinking. The fresh set of characteristics that are being worked on within any one phase will inherently link back to the very original set of customer input requirements. It is worth reminding that the HoQ is not necessarily the only planning tool that can be used at this point. Once we deeper understand the house workings then we may find different ways to perform or approximate the same function.

Development step

The development activity is where the value-added is created – as opposed to previously, where it was being planned. It is here the project team spends most of its time and resources. The QFD team will periodically refer back to the HoQ for evaluation and visualisation of progress against the ‘development importance’. The output from the development activity is evaluated against and must match the ‘Technical importance’, which were transferred from and represents the customer input requirements.

Products and the approach to developing them will of course vary. QFD does not define any specific tools or techniques for the activity. The following lists some suggestive development tools, which are often seen associated with the development processes. However, their selection is not obligatory. Other tools could in fact be equally or better suitable:

    • Picture board.
    • Translation table.
    • Sketching.
    • Design re-use.
    • CAD modelling/simulation.
    • Cost Function Analysis.
    • TRIZ.
    • Design for Manufacturing.
    • Engineering optimisation.
    • Rapid Prototyping, build and test cycles.
    • Robust Engineering Design (RED).
    • Failure Mode and Effects Analysis (FMEA).
    • … and many more

Project span

We don’t necessarily use all 4 phases in the QFD model and the project start and end points may be varied.

For example, if the development is concerned with a software product, for which the production and distribution process is already well-developed. It then suffice to use QFD approach phase 1 and 2 only.  In another example, the QFD project may omit phase 4 and instead hand the process specification to the production team under a program of Kaizen, for the team self to evolve the production planning phase. Also, the project organisation may already have well-developed market insight and platform solutions, which would enable it short-cutting the initial VOC phase. In such case, the VOC phase could simply be a matter of clarifying the existing data for the project and ensuring its visibility to the developers.

In the next post, we will look at the 4-phase model’s possible future.

You can download the Evolved 4-phase model and QFD resources here.

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