Before any of the engineering design methods, concepts, or practices described in this text- book can be put to productive use, it is necessary to first translate customer needs or de- sires, often vague or subjective, into quantitative, objective engineering specifications.
After clear specifications have been written, the methods presented in this text provide solid guidelines for selecting materials, establishing geometries, and integrating parts and subassemblies into a whole machine configuration that will safely and reliably meet both engineering and marketing goals. The task of translating marketing ideas into well-defined engineering specifications typically involves interaction, communication, and understand- ing among marketing specialists, industrial designers, financial specialists, engineering de- signers, and customers,2cooperatively participating in a cross-functional product design team.3For smaller companies, or smaller projects, the team functionsjust listed may be vested in fewerteam members by assigning multiple-functionresponsibility to one or more participants.
The first steps in translating customer needs or marketplace opportunities into engi- neering design specifications are usually managed by marketing specialists and industrial designers.Marketing specialistson the product design team typically work directly with customers to bring a sharper focus to perceived needs, to establish marketing goals, to sup- ply supportive research and business decision-making data, and to develop customer con- fidence that their needs can be efficiently met on schedule.
Industrial designers on the team are responsible for creating an initial broad-based functional description of a proposed product design, together with the essentials of a visual
2It has become common practice to include customersin product design teams. The argument for doing so is the belief that products should be designed to reflect customers’ desires and tastes, so it is efficient to interac- tively incorporate customer perceptions from the beginning (see ref. 1). On the other hand, an argument has been made that customers do not lead companies to innovation, but rather into refiningexisting products. Since technical innovation often wins the marketplace in today’s business world, companies that concentrate solely on following customer perceptions and desires, rather than leadingcustomers to innovative new ideas, are at risk.
3An interesting side issue related to the formation of a product design team lies in the task of choosing a team leader without generating interpersonal conflicts among the team members. It has been argued that choosing a team leader is the most important decision that management will make when setting up a product design team (see ref. 1, p. 50). Others have observed that good followershipis as important to team success as good leader- ship(see ref. 2). The qualities that typically characterize good leaders are, in great measure, the same qualities found in effective followers: intelligence, initiative, self-control, commitment, talent, honesty, credibility, and courage. Followership is not a person but a role. Recognition that leaders and followers are equally important in the activities of an effective cross-functional product design team avoids many of the counterproductive conflicts that arise in teams of diverse participants.
conceptthat embodies appealing external form, size, shape, color, and texture.4Artistic ren- derings and physical models5are nearly always developed as a part of this process. In de- veloping an initial product design proposal, industrial designers must consider not only broad functional requirements and marketing goals, but also aesthetics, style, ergonomics,6 company image, and corporate identity. The result of this effort is usually termed a product marketing concept.
A good product marketing concept contains all pertinent information about the pro- posed product that is essential to its marketing, but as little information as possible about details of engineering design and manufacturing, so as not to artificially constrain the en- suing engineering decision-making processes. This policy, sometimes called the policy of least commitment, is recommended for application throughout the engineering design and manufacturing stages as well, to allow as much freedom as possible for making down- stream decisions without imposing unnecessary constraints.
Engineering designerson the product design team have the responsibility of identify- ing the engineering characteristics that are directly related to customer perceptions and desires. Describing the potential influences of engineering characteristics on the market- ing goals, and evaluating the product design proposal in measurableterms, is also an en- gineering design function. Ultimately, engineering specifications for designing a practical, manufacturable product that is safe, cost-effective, and reliable are primarily the responsi- bility of the engineering designer on the team.
To implement the work of a cross-functional product design team, it is usually neces- sary to establish a set of planning and communication routines that focus and coordinate skills and experience within the company. These routines are formulated to stimulate design, manufacturing, and marketing departments to propose products that customers want to pur- chase, and will continue to purchase. One matrix-based model for interfunctional planning, communication, and evaluation is called the house of quality.7The principles underlying the house of quality paradigm apply to any effort toward establishing clear relationships be- tween manufacturing functions and customer satisfaction that are not easy to visualize di- rectly. Figure 1.1 illustrates a fraction of one subchart8that embodies many of the house of quality concepts, and provides a sequence of steps for answering the following questions:
1. What do customers want?
2. Are all customer preferences equally important?
3. Will delivering perceived needs yield a competitive advantage?
4. How can the product be effectively changed?
5. How much do engineering proposals influence customer-perceived needs?
6. How does an engineering change affect other characteristics?
Building a house of quality matrix to answer these questions begins with customer perceptions, called customer attributes (CAs).Customer attributes are a collection of cus- tomerphrasesdescribing product characteristics deemed to be important. For the car door example of Figure 1.1, the CAs shown at the left boundary include “easy to close,” “stays
4See ref. 1, p. 8.
5At this conceptual stage, models are usually crude and nonfunctional, although some may have a few moving parts.
6Ergonomicsis the study of how tools and machines can best be fitted to human capabilities and limitations.
The terms human factors engineeringandhuman-machine systemshave also been used in this context.
7See ref. 1. The house of qualityconcepts presented here are extensively paraphrased or quoted from ref. 3.
8Extracted from ref. 3.
The Product Design Team 3
open on a hill,” “doesn’t leak in rain,” and “allows no road noise.” Typical product appli- cations would define 30 to 100 CAs. The relative importanceof each attribute, as evalu- ated by the customer, is also included, as shown in Figure 1.1. The importance-weighting numbers, shown next to each attribute, are usually expressed as percentages, where the complete list of all attributes totals 100 percent.
Customer evaluations of how the proposed product (car door) compares with compet- itive productsare listed at the right side of the matrix. These evaluations, ideally based on scientific surveys of customers, identify opportunities for improvement and ways to gain competitive advantage.
To integrate pertinent engineering characteristics (ECs) into the house of quality, the product design team lists across the top side of the matrix the ECs that are thought likely to affect one or more of the CAs. Engineering characteristics should describe the product in calculable or measurable terms, and should be related directly to one or more customer perceptions.
The cross-functional design team next fills in the bodyof the house (the relationship matrix), reaching a consensus about how much each engineering characteristic affects each of the customer attributes. Semiquantitative symbols or numerical values are inserted into the matrix to establish the strengthsof the relationships. In Figure 1.1 the semiquantitative symbols represent the relationships as “strong positive,” “medium positive,” “medium neg- ative,” or “strong negative.”
Once the product design team has established the relationship strengths linking engineering characteristics to customer attributes, governing variables and objective measures are listed, and target valuesare established. Compromises in target values are
– Energy to close door + Check force on level ground + Check force on 10% slope +Door seal resistance + Road noise reduction
Relative importance ENGINEERING CHARACTERISTICS
OPEN-CLOSE EFFORT
SEALING- INSULATION
...
...
... ... ... ...
...
7 5
3 2
11 9 9.5
12 12 11
6 6 7
3 2 2
9 lb/ft ftlb lb
Measurement units lb db
5 6
EASY TO OPEN & CLOSE DOORISOLA- TIONObjective measures
CUSTOMER ATTRIBUTES
Relationships Strong positive Medium positive Medium negative Strong negative
Our car A's car B's car Customer perceptions
1 2 3 4 5 Easy to close from outside
Stays open on a hill
Our car door A's car door B's car door Doesn't leak in rain No road noise Figure 1.1
Example of a house of qualitymatrix related to the redesign of an auto- motive door. (Reprinted by permission of Harvard Business Review. Exhibit from ref. 3. Copyright © 1998 by the Harvard Business School Publish- ing Corporation; all rights reserved.)
commonplace because alltarget values cannot usually be reached at the same time in any real machine.
Finally, the team consensus on quantitativetarget values is summarized and compiled into initial engineering specifications. As noted throughout this textbook, engineering specifications provide the basis for in-depth engineering design tasks required to produce a practical, manufacturable product that is safe, cost-effective, reliable, and responsive to customer needs and desires.