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Quality function Deployment . 設計方法 朝陽科技大學工業設計系 林登立助理教授. product opportunity. A product opportunity is a mis-match between the needs of customers and the offerings of competing products.

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Quality function Deployment

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Quality function Deployment




product opportunity

  • A product opportunity is a mis-match between the needs of customers and the offerings of competing products.

  • The description of that product opportunity is, and always should be, phrased in terms that customers would understand and that they themselves might use.

  • The new product should be cheaper, have more features, look more attractive or do things that no other product currently does.


  • 以這種方式描述產品機會有許多優點。

  • 第一是它可以使產品機會簡單易懂,而且具有強烈的市場導向。

  • 其次是它確立了產品開發的目標,但卻不限制其達成手段。


  • 但是,在某些時間點,需要使用技術性的方式說明產品機會。

  • 設計程序的最終結果是產品製造規格書,它所使用的語句基本上和消費者常用的語彙有所不同。

  • 對於一般消費者而言,產品所必須使用的材料名稱可能汲有任何意義。他們可能從沒聽過生產製造程序或工程公差。

  • 重要的問題是要能適當的區別何時要用消費者導向的語句,何時要用技術性專業術語去描述產品機會。

direction for further development

  • It is a fundamental principle of effective product development that this translation form customer needs into technical objectives should happen before the start of the design process.

  • Developing a technical design specification from the opportunity specification is a pre-requisite for quality controlling the design and development process.

  • It is only by referring to the design specification that emerging new product can be judged to be progressing satisfactorily, and given direction for its further development.

  • Alternatively, the product is judged to be unsatisfactory and killed off, before further resources are wasted on its development.

two functions of quality control

  • A quality ‘guidance’ function which targets the development process progressively more closely to the achievement of customer satisfaction.

  • A quality ‘gating’ function which reviews the progress of the new product against targets and only allows through the products meeting the necessary targets.

Guiding and gating

utility, accuracy and fidelity

  • In preparing a design specification, achieving utility means making the specification useful for the purposes of quality controlling product development.

  • The design specification must, therefore, be described with sufficient precision to allow technical decisions to be made.

  • These precise descriptions in the design specification must be an accurate reflection of the customer’s needs and wishes.

  • The design specification must have fidelity to customer needs.

difficult & important

  • The preparation of this design specification is as difficult as it is important.

  • Get it wrong and you may end up with a product that has been perfectly quality controlled in entirely the wrong direction.

human brain is particularly poor

  • Getting this design specification to translate customer requirements accurately and with utility and fidelity is a fundamentally difficult task.

  • In the language of problem solving, this is a complex (problem solving involves several stages), fuzzy (the problem boundaries are ill-defined), multi­factorial (there are many different variables to consider) problem requiring simultaneous ( as opposed to sequential) resolution.

  • It is an unfortunate fact of life that the human brain is particularly poor at this sort of problem solving.

the need for humility in the design profession

  • the development of a design specification is a task for which you need help.

  • The difficulty people have with complex information processing must be acknowledged and assistance sought for a design task, for which we have been less than perfectly designed ourselves.

  • Designers need help to effectively translate customer needs into a design specification.

  • That help comes in the form of quality function deployment.

four main stages to quality function deployment

  • a matrix is developed to explore the technical attributes of a product which contribute to customer needs.

  • competing product analysis ranks the performance of existing products in terms of both customer satisfaction and technical performance.

  • quantitative targets are set for each of the technical attributes of the product and

  • these targets are prioritised.

Stage 1: The heart of quality function deployment

  • At the heart of both the procedure for quality function deployment and the house of quality diagram is the translation matrix or relationship matrix.

  • This matrix translates individual customer needs into specific technical design requirements by a systematic step-by step process.

  • The process starts by listing all the identified customer needs and arranging them in rows down one side of the matrix.

  • Then design requirements for satisfying these customer needs are arranged in columns along the top of the relationship matrix.

  • The extent to which each of these technical parameters relates to each customer need is identified in the matrix.

strength of the relationship

  • The coding system for the matrix is arbitrary but it should indicate the strength of the relationship and

  • whether it is positive (i.e. makes a positive contribution towards sat­isfying customer needs) or negative (i.e. detracts from the satisfaction of customer needs)

Stage 2: Competing product analysis

  • Competitor analysis takes two forms in quality function deployment.

  • Firstly, customers give a rating of competing products on each of their stated customer requirements.

  • Secondly, the design team examines each competing product on each of their design requirements.

  • Two competing thumb tacks were analysed, as well as the company's own existing product (Figure 8.6).

  • The ratings for both customer and design analysis were made on a 1 (worst) to 5 (best) scale.

Stage 3: Setting quantitative targets

  • Having seen how competing products compare both technically and in the eyes of customers, we are now in a position to set design targets for the proposed new product.

  • The table (Figure 8.7) shows how the three current products compare on the four design features.

target design values

Stage 4: Prioritising the design targets

  • Once the design targets are identified, it is important to know which are the most important so that maximum effort is invested in meeting, or exceeding, the most important ones.

  • It is also possible that certain design targets will have to be compromised in order to resolve conflict between them (e.g. conflict between improved features and reduced cost).

  • In order to do so systematically, each design target is given an importance rating.

  • This rating must be a reflection of their importance for achieving customer satisfaction.

  • Consequently, they are based on the customers' ratings of the importance of the different customer requirements.



importance rating

  • During the research into customer ratings of competing products, customers would have been asked to give a score from 1 to 10, indicating the importance of each customer requirement.

  • This is entered into the house of quality diagram alongside each of the customer requirements.

  • Then, using a scoring system for each type of relationship within the relationship matrix, an importance rating for each design requirement is calculated

importance ratings is arbitrary

  • The scoring system used to calculate importance ratings is arbitrary.

  • Scales of either 1 to 5 or 1 to 10 are most common, since this allows a significant differentiation between important and unimportant factors (Figure 8.10).

  • What is important about the scoring system is that it gives importance ratings which intuitively feel right.

  • If they do not feel right, adjust the' numbers slightly on the relationship scores to see if a more intuitively reasonable importance rating is produced.

  • The customer ratings should not be adjusted so arbitrarily since they are derived from market research.

  • If, for any reason they do not 'feel' right, the market research should be repeated.

beyond product planning

  • Quality function deployment can be used throughout the design process, not just in the product planning stages.

  • The house of quality is turned into a street of quality in which the outputs from one quality function deployment exercise become the input into the next quality function deployment analysis.

  • In this way, quality can be systematically and rigorously steered from product planning to manufacturing and assembly.

outputs can be taken as inputs

  • The quality function deployment procedure we have just been through takes customer requirements as inputs and translates them into design specifications as outputs.

  • These outputs can be taken as inputs into the second house of quality and turned, just as systematically into product specification outputs.

  • So, we concluded in the analysis of the thumb tack that the design specification should include diameter of head, diameter of pin, strength of join and sharpness of pin.

  • Imagine taking these requirements and placing them in the house of quality where we previously put customer requirements.

  • This would give us a relationship matrix from design specification to product specification: how do we engineer the product to meet these design specifications.

The End

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