Quality Function Deployment

Quality function deployment (QFD) is a method to transform user demands into design quality, to deploy the functions forming quality, and to deploy methods for achieving the design quality into subsystems and component parts, and ultimately to specific elements of the manufacturing process. QFD was developed by Yoji Akao and Shigeru Mizuno in Japan in 1966, by combining their expertise in quality assurance and quality control points with function deployment used in value engineering.

QFD is designed to help planners focus on characteristics of a new or existing product or service from the viewpoints of market segments, company, or technology-development needs. The technique yields charts and matrices.QFD helps transform customer needs (the Voice of the Customer) into engineering characteristics (and appropriate test methods) for a product or service, prioritizing each product or service characteristic while simultaneously setting development targets for product or service.

The QFD framework can be used for translating actual customer statements and needs (“The voice of the customer”) into actions and designs to build and deliver a quality product . Typical tools and techniques used within QFD include:

  • Affinity Diagrams. To surface the “deep structure” of voiced customer requirements.
  • Relations Diagrams. To discover priorities and root causes of process problems and unspoken customer requirements.
  • Hierarchy Trees. To check for missing data and other purposes.
  • Various Matrixes. For documenting relationships, prioritization and responsibility.
  • Process Decision Program Diagrams. To analyze potential failures of new processes and services.
  • Analytic Hierarchy Process. To prioritize a set of requirements, and to select from alternatives to meet those requirements.
  • Blueprinting. To depict and analyze all the processes which are involved in providing a product or service.
  • House of Quality.

The House of Quality

The House of Quality is a popular collection of several deployment hierarchies and tables, including the Demanded Quality Hierarchy, Quality Characteristics Hierarchy, the Relationships Matrix, the Quality Planning Table, and the Design Planning Table. It has the form of a table, that connects dots between the Voice of the Customer and the Voice of the Engineer. The House of Quality is used by multidisciplinary teams to translate a set of customer requirements, using market research and benchmarking data, into an appropriate number of prioritized engineering targets to be met by a new product design.

The House of Quality is a sort of conceptual map, which provides means to the interfunctional planning and coordination of product improvement and product development. In a way this method brings the customer needs in the focus to design or to redesign the product and service. In this method the starting point would be the customer needs which are found from any market research survey about the product in question. Primary, secondary and tertiary customer attributes are found. These form the base of the house. Corresponding engineering characteristics are specified which should be in clear measurable terms. Now the interdependencies are mapped which are in the form of the roof of the house. Accordingly, technical difficulties in achieving the desired changes are calculated. With the help of imputed importance of each characteristic the cost is worked out. Then final targets are set in clear measurable terms. In essence with the help of customer needs, the product is redesigned in clear unequivocal measurable terms.

The House of Quality contains six major components:

  1. Customer requirements (HOW`s). A structured list of requirements derived from customer statements.
  2. Technical requirements (WHAT`s). A structured set of relevant and measurable product characteristics.
  3. Planning matrix. Illustrates customer perceptions observed in market surveys. Includes relative importance of customer requirements, company and competitor performance in meeting these requirements.
  4. Interrelationship matrix. Illustrates the QFD team’s perceptions of interrelationships between technical and customer requirements. An appropriate scale is applied, which is illustrated by using symbols or figures. To fill this portion of the matrix involves discussions and to build consensus within the team, which can be time consuming. Concentrating on key relationships and minimizing the numbers of requirements are useful techniques to reduce the demands on resources.
  5. Technical correlation (Roof) matrix. Used to identify where technical requirements support or impede each other in the product design. Can highlight innovation opportunities.
  6. Technical priorities, benchmarks and targets. Used to record:
    • The priorities assigned to technical requirements by the matrix.
    • Measures of technical performance achieved by competitive products.
    • The degree of difficulty involved in developing each requirement.

    The final output of the matrix is a set of target values for each technical requirement to be met by the new design, which are linked back to the demands of the customer.

Origin of Quality Function Deployment

QFD was first developed in Japan in the late 1960s by Professor Yoji Akao and Professor Shigeru Mizuno as a quality system. QFD was aimed at delivering products and services that efficiently satisfy customers. One should listen to the “voice of the customer” throughout the product or service development process. Mizuno, Akao and other Japanese Quality Management experts developed the tools and techniques for QFD and organized them into a comprehensive system to assure quality and customer satisfaction in new products and services. After World War II, statistical quality control had taken roots in the Japanese manufacturing industry. Quality activities were being integrated with techniques that were emphasizing the importance of making quality control a part of business management. This became eventually known as TQC and TQM. Mizuno and Akao wanted to develop a quality assurance method that would design customer satisfaction into a product before it was manufactured. Prior quality control methods were primarily aimed at fixing a problem during or after manufacturing.

Yoji Ako was the first pioneer to develop QFD from 1965 to 1967 at Matsushita Electric in Japan. In 1966, Kiyotaka Oshiumi of Bridgestone Tires in Japan presented a first large scale application, which used a process assurance items fishbone diagram to identify each customer requirement (effect), and to identify the design substitute quality characteristics and process factors (causes), which are needed to control and measure it. In 1972, with the application of QFD to the design of an oil tanker at the Kobe Shipyards of Mitsubishi Heavy Industry, the fishbone diagrams grew unwieldy. Since the effects shared multiple causes, the fishbones could be changed into a spreadsheet or matrix format. The rows were desired effects of customer satisfaction, and the columns were the controlling and measurable causes. At the same time, Katsuyoshi Ishihara introduced the Value Engineering principles, which are used to describe how a product and its components work. He expanded this to describe business functions necessary to assure quality of the design process itself. Merged with these new ideas, QFD eventually became the comprehensive quality design system for both product and business process. The introduction of QFD to America and Europe began in 1983 when the American Society for Quality Control published Akao’s work in Quality Progress. Following that, Cambridge Research (now the Kaizen Institute) invites Mr. Akao to give a QFD seminar in Chicago.

Usage of the Quality Function Deployment method

  • To prioritize customer demands and customer needs. Spoken and unspoken;
  • Translating these needs into actions and designs such as technical characteristics and specifications; and
  • To build and deliver a quality product or service, by focusing various business functions toward achieving a common goal of customer satisfaction.
  • QFD has been applied in any industry: aerospace, manufacturing, software, communication, IT, chemical and pharmaceutical, transportation, defense, government, R&D, food, and service industry.

Steps in Quality Function Deployment

Typically, a QFD process has the following stages:

  1. Derive top level product requirements or technical characteristics from customer needs, using the Product Planning Matrix.
  2. Develop product concepts to satisfy these requirements.
  3. Evaluate product concepts to select the most optimal concept, using the Concept Selection Matrix.
  4. Partition the system concept or architecture into subsystems or assemblies, and transfer the higher level requirements or technical characteristics to these subsystems or assemblies.
  5. Derive lower-level product requirements (assembly or part characteristics) and specifications from subsystem/assembly requirements (Assembly/Part Deployment Matrix).
  6. For critical assemblies or parts, derive lower-level product requirements (assembly or part characteristics) into the process planning.
  7. Determine manufacturing process steps that correspond to these assembly or part characteristics.
  8. Based on these process steps, determine set-up requirements, process controls and quality controls to assure the achievement of these critical assembly or part characteristics.

Strengths of the Quality Function Deployment model

  • QFD seeks out both “spoken” and “unspoken” customer requirements and maximizes “positive” quality (such as ease of use, fun, luxury) that creates value. Traditional quality systems aim at minimizing negative quality (such as defects, poor service).
  • Instead of conventional design processes that focus more on engineering capabilities and less on customer needs, QFD focuses all product development activities on customer needs.
  • QFD makes invisible requirements and strategic advantages visible. This allows a company to prioritize and deliver on them.
  • Reduced time to market.
  • Reduction in design changes.
  • Decreased design and manufacturing costs.
  • Improved quality.
  • Increased customer satisfaction.
  • The literature describes how Toyota reduced start-up losses by 61%. Mazda reduced last minute design changes by half, etc.

Limitations of Quality Function Deployment

  • As with other Japanese management techniques, some problems can occur when we apply QFD within the western business environment and culture.
  • Customer perceptions are found by market survey. If the survey is performed in a poor way, then the whole analysis may result in doing harm to the firm.
  • The needs and wants of customers can change quickly nowadays. Comprehensive system- and methodical thinking can make adapting to changed market needs more complex.

Assumptions of Quality Function Deployment

  • The market survey results are accurate.
  • Customer needs can be documented and captured and they remain stable during the whole process.

Source: Shigeru Mizuno and Yoji Akao – QFD: The Customer-Driven Approach to Quality Planning and Deployment

Source: Shigeru Mizuno and Yoji Akao – QFD: Integrating Customer Requirements into Product Design

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