Step-by-step guide to performing quality function deployment (QFD)

PERFORMING QFD STEP BY STEP

Kenneth Crow
DRM Associates

© 2002 DRM Associates  All rights reserved. May be used with attribution. Other use prohibited.

Product Development Forum
NPD Body of Knowledge
Quality Function Deployment (QFD) Paper
QFD: What, Why and How
QFD Case Study
QFD Software and Examples
Product Definition
QFD Experience
Quality Function Deployment (QFD) Workshop
Voice of the Customer (VOC) Workshop
QFD Consulting
QFD Software (PD Toolkit)
DRM Associates

QFD uses a series of matrices to document information collected and developed and represent the team's plan for a product. The QFD methodology is based on a systems engineering approach consisting of the following general steps:

  1. Derive top-level product requirements or technical characteristics from customer needs (Product Planning Matrix).
  2. Develop product concepts to satisfy these requirements.
  3. Evaluate product concepts to select most optimum (Concept Selection Matrix).
  4. Partition system concept or architecture into subsystems or assemblies and flow-down 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, flow-down lower-level product requirements (assembly or part characteristics) to process planning.
  7. Determine manufacturing process steps to meet these assembly or part characteristics.
  8. Based in these process steps, determine set-up requirements, process controls and quality controls to assure achievement of these critical assembly or part characteristics.

The QFD process described below is supported by our Product Development Toolkit, which includes QFD software. The matrices and the specific steps in the QFD process are as follows.

Gather Customer Needs
  1. Plan collection of customer needs. What sources of information will be used? Consider customer requirement documents, requests for proposals, requests for quotations, contracts, customer specification documents, customer meetings/interviews, focus groups/clinics, user groups, surveys, observation, suggestions, and feedback from the field. Consider both current customers as well as potential customers. Pay particular attention to lead customers as they are a better indicator of future needs. Plan who will perform the data collection activities and when these activities can take place. Schedule activities such as meetings, focus groups, surveys, etc.
  2. Prepare for collection of customer needs. Identify required information. Prepare agendas, list of questions, survey forms, focus group/user meeting presentations.
  3. Determine customer needs or requirements using the mechanisms described in step 1. Document these needs. Consider recording any meetings. During customer meetings or focus groups, ask "why" to understand needs and determine root needs. Consider spoken needs and unspoken needs. Extract statements of needs from documents. Summarize surveys and other data. Use techniques such as ranking, rating, paired comparisons, or conjoint analysis to determine importance of customer needs. Gather customer needs from other sources such as customer requirement documents, requests for proposals, requests for quotations, contracts, customer specification documents, customer meetings/interviews, focus groups, product clinics, surveys, observation, suggestions, and feedback from the field.
  4. Use affinity diagrams to organize customer needs. Consolidate similar needs and restate. Organize needs into categories. Breakdown general customer needs into more specific needs by probing what is needed. Maintain dictionary of original meanings to avoid misinterpretation. Use function analysis to identify key unspoken, but expected needs.
  5. Once needs are summarized, consider whether to get further customer feedback on priorities. Undertake meetings, surveys, focus groups, etc. to get customer priorities. State customer priorities using a 1 to 5 rating. Use ranking techniques and paired comparisons to develop priorities.
Product Planning
  1. Organize customer needs in the Product Planning Matrix. Group under logical categories as determined with affinity diagramming.
  2. Establish critical internal customer needs or management control requirements; industry, national or international standards; and regulatory requirements. If standards or regulatory requirements are commonly understood, they should not be included in order to minimize the information that needs to be addressed.
  3. State customer priorities. Use a 1 to 5 rating. Critical internal customer needs or management control requirements; industry, national or international standards; and regulatory requirements, if important enough to include, are normally given a rating of "3".
  4. Develop competitive evaluation of current company products and competitive products. Use surveys, customer meetings or focus groups/clinics to obtain feedback. Rate the company's and the competitor's products on a 1 to 5 scale with "5" indicating that the product fully satisfies the customer's needs. Include competitor's customer input to get a balanced perspective.
  5. Review the competitive evaluation strengths and weaknesses relative to the customer priorities. Determine the improvement goals and the general strategy for responding to each customer need. The Improvement Factor is "1" if there are no planned improvements to the competitive evaluation level. Add a factor of .1 for every planned step of improvement in the competitive rating, (e.g., a planned improvement of goiung from a rating of "2" to "4" would result in an improvement factor of "1.2". Identify warranty, service, or reliability problems & customer complaints to help identify areas of improvement.
  6. Identify the sales points that Marketing will emphasize in its message about the product. There should be no more than three major or primary sales points or two major sales points and two minor or secondary sales points in order to keep the Marketing message focused. Major sales points are assigned a weighting factor of 1.3 and minor sales points are assigned a weighting factor of 1.1.
  7. The process of setting improvement goals and sales points implicitly develops a product strategy. Formally describe that strategy in a narrative form. What is to be emphasized with the new product? What are its competitive strengths? What will distinguish it in the marketplace? How will it be positioned relative to other products? In other words, describe the value proposition behind this product. The key is to focus development resources on those areas that will provide the greatest value to the customer. This strategy brief is typically one page and is used to gain initial focus within the team as well as communicate and gain concurrence from management.
  8. Establish product requirements or technical characteristics to respond to customer needs and organize into logical categories. Categories may be related to functional aspects of the products or may be grouped by the likely subsystems to primarily address that characteristic. Characteristics should be meaningful (actionable by Engineering), measurable, practical (can be determined without extensive data collection or testing)and global. By being global, characteristics should be stated in a way to avoid implying a particular technical solution so as not to constrain designers. This will allow a wide range of alternatives to be considered in an effort to better meet customer needs. Identify the direction of the objective for each characteristic (target value or range, maximize or minimize).
  9. Develop relationships between customer needs and product requirements or technical characteristics. These relationships define the degree to which as product requirement or technical characteristic satisfies the customer need. It does NOT show a potential negative impact on meeting a customer need - this will be addressed later in the interaction matrix. Consider the goal associated with the characteristic in determining whether the characteristic satisfies the customer need. Use weights (we recommend using 5-3-1 weighting factors) to indicate the strength of the relationship - strong, medium and weak. Be sparing with the strong relationships to discriminate the really strong relationships.
  10. Perform a technical evaluation of current products and competitive products. Sources of information include: competitor websites, industry publications, customer interviews, published specifications, catalogs and brochures, trade shows, purchasing and benchmarking competitorís products, patent information, articles and technical papers, published benchmarks, third-party service & support organizations, and former employees. Perform this evaluation based on the defined product requirements or technical characteristics. Obtain other relevant data such as warranty or service repair occurrences and costs.
  11. Develop preliminary target values for product requirements or technical characteristics. Consider data gathered during the technical evaluation in setting target values. Do not get too aggressive with target values in areas that are not determined to be the primary area of focus with this development effort.
  12. Determine potential positive and negative interactions between product requirements or technical characteristics using symbols for strong or medium, positive or negative relationships. Too many positive interactions suggest potential redundancy in product requirements or technical characteristics. Focus on negative interactions - consider product concepts or technology to overcome these potential trade-offs or consider the trade-off's in establishing target values.
  13. Calculate importance ratings. Multiply the customer priority rating by the improvement factor, the sales point factor and the weighting factor associated with the relationship in each box of the matrix and add the resulting products in each column.
  14. Identify a difficulty rating (1 to 5 point scale, five being very difficult and risky) for each product requirement or technical characteristic. Consider technology maturity, personnel technical qualifications, resource availability, technical risk, manufacturing capability, supply chain capability, and schedule. Develop a composite rating or breakdown into individual assessments by category.
  15. Analyze the matrix and finalize the product plan. Determine required actions and areas of focus.
  16. Finalize target values. Consider the product strategy objectives, importance of the various technical characteristics, the trade-offs that need to be made based on the interaction matrix, the technical difficulty ratings, and technology solutions and maturity.
  17. Maintain the matrix as customer needs or conditions change.
Concept Development
  1. Develop concept alternatives for the product. Consider not only the current approach and technology, but other alternative concept approaches and technology. Use brainstorming. Conduct literature, technology, and patent searches. Use product benchmarking to identify different product concepts. Develop derivative ideas. Perform sufficient definition and development of each concept to evalaute against the decision criteria determined in the next step.
  2. Evaluate the concept alternatives using the Concept Selection Matrix. List product requirements or technical characteristics from the Product Planning Matrix down the left side of the Concept Selection Matrix. Also add other requirements or decision criteria such as key unstated but expected customer needs or requirements, manufacturability requirements, environmental requirements, standards and regulatory requirements, maintainability / serviceability requirements, support requirements, testability requirements, test schedule and resources, technical risk, business risk, supply chain capability, development resources, development budget, and development schedule.
  3. Carry forward the target values for the product requirements or technical characteristics from the Product Planning Matrix. Add target values as appropriate for the other evaluation criteria added in the previous step. Also bring forward the importance ratings and difficulty ratings associated with each product requirement or technical characteristic from the Product Planning Matrix. Normalize the importance rating by dividing the largest value by a factor that will yield "5" and post this value to the "Priority" column. Review these priorities and consider any changes appropriate since these are the weighting factors for the decision criteria. Determine the priorities for the additional evaluation criteria added in the prior step. List concepts across the top of the matrix.
  4. Perform engineering analysis and trade studies. Rate each concept alternative against the criteria using a "1" to "5" scale with "5" being the highest rating for satisfying the criteria.
  5. For each rating, multiply the rating by the "Priority" value in that row. Summarize these values in each column in the bottom row. The preferred concept alternative(s) will be the one(s) with the highest total.
  6. For the preferred concept alternative(s), work to improve the concept by synthesizing a new concept that overcomes its weaknesses. Focus attention on the criteria with the lowest ratings for that concept ("1's" and "2's"). What changes can be made to the design or formulation of the preferred concept(s) to improve these low ratings with the product concept? Compare the preferred concept(s) to the other concepts that have higher ratings for that particular requirement. Are there ways to modify the preferred concept to incorporate the advantage of another concept?
Subsystem/Subassembly/Part Deployment Matrix
  1. Using the selected concept as a basis, develop a design layout, block diagram and/or a preliminary parts list. Determine critical subsystems, subassemblies or parts. Consider impact of subsystems, subassemblies or parts on product performance or with respect to development goals. What parts, assemblies or subsystems present major challenges or are critical to the success and operation of the product? What critical characteristics have a major effect on performance? Consider performing failure mode and effects analysis (FMEA); failure mode, effects and criticality analysis (FMECA); or fault tree analysis (FTA) to help pinpoint critical items and their critical characteristics from a reliability/quality perspective.
  2. If there will be multiple Subsystem/Subassembly/Part Deployment Matrices prepared, deploy the technical characteristics and their target values to the appropriate matrices. Carry forward the important or critical product requirements or technical characteristics from Product Planning Matrix (based on importance ratings and team decision) to the Subsystem/Subassembly/Part Deployment Matrix. These "product needs" become the "what's" for this next level matrix. Where appropriate, allocate target values (e.g., target manufacturing cost, mean-time between failures, etc.) to the Subsystem / Subassembly / Part Deployment Matrices. Organize these product requirements or technical characteristics by assembly(ies) or part(s) to be addressed on a particular deployment matrix. Include any additional customer needs or requirements to address more detailed customer needs or general requirements. Normalize the Importance Ratings from the Product Planning Matrix and bring them forward as the Priority ratings. Review these priority ratings and make appropriate changes for the subsystems, subassemblies or parts being addressed. Determine the the Priority for any needs that were added.
  3. Considering product requirements or technical characteristics, identify the critical part, subassembly or subsystem characteristics. State the characteristics in a measurable way. For higher-level subsystems or subassembles, state the characteristics in a global manner to avoid constraining concept selection at this next level.
  4. Develop relationships between product needs (product-level technical characteristics) and the subsystem / subassembly / part technical characteristics. Use 5-3-1 relationship weights for strong, medium and weak relationships. Be sparing with the strong relationships.
  5. Develop preliminary target values for subsystem / subassembly / part characteristics.
  6. Determine potential positive and negative interactions between the technical part characteristics using symbols for strong or medium, positive or negative relationships. Too many positive interactions suggest potential redundancy in critical part characteristics. Focus on negative interactions - consider different subsystem / subassembly / part concepts, different technologies, tooling concepts, material technology, and process technology to overcome the potential trade-off or consider the trade-off in establishing target values.
  7. Calculate importance ratings. Assign a weighting factor to the relationships (5-3-1). Multiply the customer importance rating by the improvement factor (if any), the sales point factor (if any) and the relationship factor in each cell of the relationship matrix and add the resulting products in each column.
  8. Identify a difficulty rating (1 to 5 point scale, five being very difficult and risky) for each subsystem / subassembly / part requirement or technical characteristic. Consider technology maturity, personnel technical qualifications, business risk, manufacturing capability, supplier capability, and schedule. Develop a composite rating or breakdown into individual assessments by category. Determine if overall risk is acceptable and if individual risks based on target or specification values are acceptable. Adjust target or specification values accordingly.
  9. Analyze the matrix and finalize the subsystem/subassembly/part deployment matrix. Determine required actions and areas of focus.
  10. Finalize target values. Consider interactions, importance ratings and difficulty ratings.