What is QFD?

Quality Function Deployment (QFD) is a design approach in which the cross-organisational functions coherently and systematically maintain in focus what is most important to customers and stakeholders, thereby assuring quality and reducing time. We can apply QFD to any project that, for one, is a development activity and, two, has a definable customer. This includes products, parts, materials, services, events, software and websites.

QFD is not a design and development process (even if the common model is often depicted to resemble one). Its approach is a model for the thinking and the collaboration that goes into identifying, prioritising and resolving design problems. The QFD approach therefore integrates into all different kinds of design and development processes.

 

ISO 16355-1 QFD flow chart

Flow chart for product development, within which the QFD approach is used.
(adapted from ISO 16355-1, Clause 5.2.2)

 

The founders have described QFD as “a way to assure the design quality while the product is still in the design stage” [Akao]. Standard ISO 16355-1:2015 on “General principles and perspectives of Quality Function Deployment” defines it as the “managing of all organizational functions and activities to assure product quality”. The Standard tells that QFD assures satisfaction “by designing in […] the requirements that are most important to the customer or stakeholder”.

ISO 16355 does not provide any ready-made model for implementing QFD. It defines a generic design process flow and describes how the elements of QFD fits within the stages of this generic flow. Annex A to the standard informs of example tools and summarily discusses a few recognised QFD model approaches.

By comparison to other more established design and quality standards, ISO 16355 on QFD can be said to be in its infancy. In a sense, QFD practitioners are still learners. The approach is continually evolving and being tailored for individual circumstances. Judging by an internet image search, the 4-phase model [by Clausing et al] is used in about 95% of all QFD projects today.


Example QFD models and their suggested areas of application, in respect of project complexity (deducted from ISO 16355-1, Annex A). The 4-phase approach covers the majority centre range.

The 4-phase flow diagram shown here should be read as an generalised approach. It is not a strictly delimited, sequential, process. When designing a product feature, we must of course give thought to how a chosen solution can be reliably produced. We will apply Design For Manufacturing (DFM) principles and judge its fit within our existing production systems. By time the product design phase is complete, we will already know how to produce the design. The process design phase is more about defining and refining the details, including any process equipment, while keeping in focus the importance that tracks back to the original Voice of Customer. Both the process design and operations phases may well find design optimisation potential, which will benefit from an adjustment to the initial design specification [thoughts on the QFD model].

Clausing's 4-phase QFD is truncated form of Akao's Comprehensive QFD model

The 4-phase QFD model [from Clausing's] is a truncated variant of the original ‘comprehensive’ approach [Akao].