QFD | Quality Function Deployment | Quality-One

How to Implement Quality Function Deployment (QFD)

The Quality Function Deployment methodology is a 4-phase process that encompasses activities throughout the product development cycle.  A series of matrices are utilized at each phase to translate the Voice of the Customer to design requirements for each system, sub-system and component. The four phases of QFD are:

1. Product Definition: The Product Definition Phase begins with collection of VOC and translating the customer wants and needs into product specifications. It may also involve a competitive analysis to evaluate how effectively the competitor’s product fulfills the customer wants and needs. The initial design concept is based on the particular product performance requirements and specifications.
2. Product Development: During the Product Development Phase, the critical parts and assemblies are identified. The critical product characteristics are cascaded down and translated to critical or key part and assembly characteristics or specifications. The functional requirements or specifications are then defined for each functional level.
3. Process Development: During the Process Development Phase, the manufacturing and assembly processes are designed based on product and component specifications. The process flow is developed and the critical process characteristics are identified.
4. Process Quality Control: Prior to production launch, the QFD process identifies critical part and process characteristics. Process parameters are determined and appropriate process controls are developed and implemented. In addition, any inspection and test specifications are developed. Full production begins upon completion of process capability studies during the pilot build.

Effective use of QFD requires team participation and discipline inherent in the practice of QFD, which has proven to be an excellent team-building experience.

Level 1 QFD

The House of Quality is an effective tool used to translate the customer wants and needs into product or service design characteristics utilizing a relationship matrix. It is usually the first matrix used in the QFD process. The House of Quality demonstrates the relationship between the customer wants or “Whats” and the design parameters or “Hows”. The matrix is data intensive and allows the team to capture a large amount of information in one place. The matrix earned the name “House of Quality” due to its structure resembling that of a house. A cross-functional team possessing thorough knowledge of the product, the Voice of the Customer and the company’s capabilities, should complete the matrix. The different sections of the matrix and a brief description of each are listed below:

• “Whats”: This is usually the first section to be completed. This column is where the VOC, or the wants and needs, of the customer are listed.
• Importance Factor: The team should rate each of the functions based on their level of importance to the customer. In many cases, a scale of 1 to 5 is used with 5 representing the highest level of importance.
• “Hows” or Ceiling: Contains the design features and technical requirements the product will need to align with the VOC.
• Body or Main Room: Within the main body or room of the house of quality the “Hows” are ranked according to their correlation or effectiveness of fulfilling each of the “Whats”. The ranking system used is a set of symbols indicating either a strong, moderate or a weak correlation. A blank box would represent no correlation or influence on meeting the “What”, or customer requirement. Each of the symbols represents a numerical value of 0, 1, 3 or 9.
• Roof: This matrix is used to indicate how the design requirements interact with each other. The interrelationships are ratings that range from a strong positive interaction (++) to a strong negative interaction (–) with a blank box indicating no interrelationship.
• Competitor Comparison: This section visualizes a comparison of the competitor’s product in regards to fulfilling the “Whats”. In many cases, a scale of 1 to 5 is used for the ranking, with 5 representing the highest level of customer satisfaction. This section should be completed using direct feedback from customer surveys or other means of data collection.
• Relative Importance: This section contains the results of calculating the total of the sums of each column when multiplied by the importance factor. The numerical values are represented as discrete numbers or percentages of the total. The data is useful for ranking each of the “Hows” and determining where to allocate the most resources.
• Lower Level / Foundation: This section lists more specific target values for technical specifications relating to the “Hows” used to satisfy VOC.

Upon completion of the House of Quality, the technical requirements derived from the VOC can then be deployed to the appropriate teams within the organization and populated into the Level 2 QFDs for more detailed analysis. This is the first step in driving the VOC throughout the product or process design process.

Level 2 QFD

The Level 2 QFD matrix is a used during the Design Development Phase. Using the Level 2 QFD, the team can discover which of the assemblies, systems, sub-systems and components have the most impact on meeting the product design requirements and identify key design characteristics. The information produced from performing a Level 2 QFD is often used as a direct input to the Design Failure Mode and Effects Analysis (DFMEA) process. Level 2 QFDs may be developed at the following levels:

• System Level: The technical specifications and functional requirements or “Hows” identified and prioritized within The House of Quality become the “Whats” for the system level QFD. They are then evaluated according to which of the systems or assemblies they impact. Any systems deemed critical would then progress to a sub-system QFD.
• Sub-system Level: The requirements cascaded down from the system level are re-defined to align with how the sub-system contributes to the system meeting its functional requirements. This information then becomes the “Whats” for the QFD and the components and other possible “Hows” are listed and ranked to determine the critical components. The components deemed critical would then require progression to a component level QFD.
• Component Level: The component level QFD is extremely helpful in identifying the key and critical characteristics or features that can be detailed on the drawings. The key or critical characteristics then flow down into the Level 3 QFD activities for use in designing the process. For purchased components, this information is valuable for communicating key and critical characteristics to suppliers during sourcing negotiations and as an input to the Production Part Approval Process (PPAP) submission.

Level 3 QFD

The Level 3 QFD is used during the Process Development Phase where we examine which of the processes or process steps have any correlation to meeting the component or part specifications. In the Level 3 QFD matrix, the “Whats” are the component part technical specifications and the “Hows” are the manufacturing processes or process steps involved in producing the part. The matrix highlights which of the processes or process steps have the most impact on meeting the part specifications. This information allows the production and quality teams to focus on the Critical to Quality (CTQ) processes, which flow down into the Level 4 QFD for further examination.

Level 4 QFD

The Level 4 QFD is not utilized as often as the previous three. Within the Level 4 QFD matrix, the team should list all the critical processes or process characteristics in the “Whats” column on the left and then determine the “Hows” for assuring quality parts are produced and list them across the top of the matrix. Through ranking of the interactions of the “Whats” and the “Hows”, the team can determine which controls could be most useful and develop quality targets for each. This information may also be used for creating Work Instructions, Inspection Sheets or as an input to Control Plans.

The purpose of Quality Function Deployment is not to replace an organization’s existing design process but rather support and improve an organization’s design process. QFD methodology is a systemic, proven means of embedding the Voice of the Customer into both the design and production process. QFD is a method of ensuring customer requirements are accurately translated into relevant technical specifications from product definition to product design, process development and implementation. The fact is that every business, organization and industry has customers. Meeting the customer’s needs is critical to success.  Implementing QFD methodology can enable you to drive the voice of your customers throughout your processes to increase your ability to satisfy or even excite your customers.