Omega Guide 3

QFD – Quality Function Deployment … a brief guide

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Issue 1.0
July 2012

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QFD – Quality Function Deployment … a brief guide

Overview

  • Quality Function Deployment is a particularly useful methodology to use whenever attempting to determine and analyse a set of requirements, especially to check for any missing parts, and to integrate analysis of requirements and functionality
  • QFD enables retention of customer focus, integrating the “Voice of the Customer(s)” (mostly the WHATs ) into what the system is to do (the HOWs) in a structured and traceable way
  • It is used to validate requirements – checking that the proposed means of meeting requirements is complete
  • It is a visual technique that shows the full traceability of every aspect of solution back to stakeholder needs
  • Used to support the development of requirements documentation and flow down
  • It can be used to prioritise aspects of the solution – and so generate Critical to Quality (CTQ) definitions

Tips / Dangers / Source

  • Do not overcomplicate it – too many rows and columns make it hard to do
  • Keep notes on rationale given for correlation or relationship – otherwise you will struggle to update
  • Expect a considerable number of blank cells
  • Don’t confuse correlations between HOWs with relationship between WHAT and HOW
  • Don’t over-analyse / debate each relationship
  • Be clear where received requirements go – customers may give functions / technical requirements as well as customer needs

QFD is sometimes know as the “House of Quality”. This is due to the resemblance (especially of the ‘How’ correlations, to a roof) of the diagram to a house.

The ‘House of Quality’ is the central construct of QFD and the elements included should be tailored to your organisation.

QFD was conceived in Japan in the late 1960’s in response to challenges in the manufacturing industry.


The House(s) of Quality

The Basic House of Quality

Matrix comparison of WHATs (customer needs) and HOWs (technical design requirement, or function).

There is no `fixed` symbology but a standard should be chosen.

Use clear symbols in your QFD`s. An example of symbols is below:


Flow from Customer Need to Production Requirements


  • QFD 2 relates the functionality to the physical elements of the solution
  • QFD 3 translates physical elements to the manufacturing requirements (helping to set out key tolerances making solution robust to variation)
  • QFD 4 defines the control measures required in production to ensure customer quality (the WHATs are in QFD1)


Decomposition Between System Levels


The Process for doing a QFD1

QFD 1 relates to the required properties of system of interest to the required functionality.

The steps to build a‘House of Quality’


Step 1 – Identify customer / stakeholder “WHATs” and record any specified targets

Step 2 – Translate customer / stakeholder wants into measurable technical requirements (the “HOWs” (translating for action)

Step 3 – Determine relationships between customer and technical requirements

Step 4 – Determine targets for the technical requirements (traceable to customers needs)

Step 5 – Identify requirements correlations / trade-offs

Step 6 – Assess importance and competitive assessments

This summary is based on material prepared by Richard Beasley of Rolls-Royce plc for INCOSE UK one day event “Simple Systems Techniques That Work”, which in turn was based and derived from the training provided by Stuart Burge of Burge Hughes Walsh.


This leaflet is intended as a working guide to Quality Function Deployment

This series of working guides is produced by members of the UK Chapter of INCOSE. For further information, advice and links to helpful websites go to: www.incoseonline.org.uk

Members can download copies of this leaflet and other Systems Engineering resources online at: www.incoseonline.org.uk

For more information about the worldwide Systems Engineering professional community, go to: www.incose.org

Series editor: Hazel Woodcock
Lead author: Richard Beasley (Rolls-Royce plc)
© 2012 INCOSE UK Ltd