Chapter 2 Literature Review
2.4 Quality Function Deployment
2.4.3 The QFD Method
The QFD method consists of the construction of one or more matrices. QFD employs several matrices to clearly establish relationships between company functions and customer satisfaction. Among these interrelated phases (as shown in Figure 2-10), the HOQ is the most commonly used table and its aim is to reflect customer wants. Its concept and mechanism is to translate Customer Requirements directly into a product’s technical characteristics through the various stages of product planning, engineering, and manufacturing.
Because quality table has a “roof” on the top, it is called a “quality house” which is also known as “the House of Quality” (see Figure 2-9). HOQ is the primary tool of QFD which calculates the weights and relationships automatically and could easily and rapidly reflect the priorities among the customers and design requirements (Akao, 1990). One form of QFD is a four-phase model, which includes the house of quality (HOQ), parts deployment, process planning and production planning (Hauser and Clausing, 1988). These four linked house implicitly convey the voice of customer through manufacturing. It uses a matrix to present what the customers’ requires against how those requirements would be met.
Correlation Matrix
Technical Requirement (How)
Relationship Matrix
Target Values Technical Assessment
Weight
Customer Assessment Importance
Customer attributes (What)
Figure 2-9: House of Quality Source: Griffin and Hauser, (1992) The columns of HOQ are set referring to following usage:
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Step 1: Customer Requirements - "Voice of the Customer"The first step in a QFD project is to determine what market segments will be
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analyzed during the process and to identify who the customers are. The team then gathers information from customers on the requirements they have for the product or service. In order to organize and evaluate this data, the team uses simple quality tools like Affinity Diagrams or Tree Diagrams.
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Step 2: Regulatory RequirementsNot all product or service requirements are known to the customer, so the team must document requirements that are dictated by management or regulatory standards that the product must adhere to.
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Step 3: Customer Importance RatingsOn a scale from 1 - 5, customers then rate the importance of each requirement. This number will be used later in the relationship matrix.
Relationship matrix collects all relationships among design and customers’
requirements.
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Step 4: Customer Rating of the CompetitionUnderstanding how customers rate the competition can be a tremendous competitive advantage. In this step of the QFD process, it is also a good idea to ask customers how your product or service rates in relation to the competition. There is remodeling that can take place in this part of the House of Quality. Additional rooms that identify sales opportunities, goals for continuous improvement, customer complaints, etc., can be added.
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Step 5: Technical Descriptors - "Voice of the Engineer"The technical descriptors are attributes about the product or service that can be measured and benchmarked against the competition. Technical descriptors may exist that your organization is already using to determine product specification, however new measurements can be created to ensure that your product is meeting customer needs.
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Step 6: Direction of ImprovementAs the team defines the technical descriptors, a determination must be made as to the direction of movement for each descriptor.
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Step 7: Relationship MatrixThe relationship matrix is where the team determines the relationship between customer needs and the company's ability to meet those needs. The team asks the question, "What is the strength of the relationship between the technical descriptors and the customers’ needs?" Relationships can either be weak, moderate, or strong or carry a numeric value of 1, 3 or 9.
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Step 8: Organizational DifficultyRate the design attributes in terms of organizational difficulty. It is very possible that some attributes are in direct conflict. Increasing the number of sizes may be in conflict with the company’s stock holding policies, for example.
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Step 9: Technical Analysis of Competitor ProductsTo better understand the competition, engineering then conducts a comparison of competitor technical descriptors. This process involves reverse engineering competitor products to determine specific values for competitor technical descriptors.
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Step 10: Target Values for Technical DescriptorsAt this stage in the process, the QFD team begins to establish target values for each technical descriptor. Target values represent "how much" for the technical descriptors, and can then act as a base-line to compare against.
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Step 11: Correlation MatrixThis room in the matrix is where the term House of Quality comes from because it makes the matrix look like a house with a roof. The correlation matrix is probably the least used room in the House of Quality; however, this room is a big help to the
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design engineers in the next phase of a comprehensive QFD project. Team members must examine how each of the technical descriptors impacts each other. The team should document strong negative relationships between technical descriptors and work to eliminate physical contradictions.
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Step 12: Absolute ImportanceFinally, the team calculates the absolute importance for each technical descriptor.
This numerical calculation is the product of the cell value and the customer importance rating. Numbers are then added up in their respective columns to determine the importance for each technical descriptor.
A house of quality (HOQ) involves the collection and analysis of the “voice of the customer” which includes the customer needs for a product, customers’ perceptions on the relative importance of these needs and the relative performance of the producing company and its main competitors on the needs. With such a large amount of information to be collected and processed, building an HOQ may be too complex to be complete and comparable. Thus systematization of the HOQ process is a necessity.