Plan On the Web
3. Understand
the problem by developing requirements and uncovering existing solutions for similar problems.4. Generate
alternative solutions.5. Evaluate
the alternatives by comparing them to the design requirements and to each other.6. Decide
on acceptable solutions. This model fits design whether we are looking at the entire product see the product life-cycle diagram, Fig. 1.7 or the smallest detail of it. These actions are not necessarily taken in 1-2-3 order. In fact they are often in- termingled with solution generation and evaluation improving the understanding of the problem, enabling new, improved solutions to be generated. This iterative nature of design is another feature that separates it from analysis. The list of actions is not complete. If we want anyone else on the design team to make use of our results, a seventh action is also needed: 7. Communicate the results. The need that initiates the process may be very clearly defined or ill-defined. Consider the problem statements for the design of the simple lap joint of two pieces of metal given earlier Fig. 1.9. The need was given by the problem statement in both cases. In the first statement, understanding is the knowledge of what parameters are needed to characterize a problem of this type and the equations that relate the parameters to each other a model of the joint. There is no need to generate potential solutions, evaluate them, or make any decision, because this is an analysis problem. The second problem statement needs work to understand. The requirements for an acceptable solution must be developed, and then alternative solutions can be generated and evaluated. Some of the evaluation may be the same as the analysis problem, if one of the concepts is a bolt. Some important observations: ■ New needs are established throughout the design effort because new design problems arise as the product evolves. Details not addressed early in the process must be dealt with as they arise; thus, the design of these details poses new subproblems. ■ Planning occurs mainly at the beginning of a project. Plans are always updated because understanding is improved as the process progresses. ■ Formal efforts to understand new design problems continue throughout the process. Each new subproblem requires new understanding. ■ There are two distinct modes of generation: concept generation and product generation. The techniques used in these two actions differ. ■ Evaluation techniques also depend on the design phase; there are differ- ences between the evaluation techniques used for concepts and those used for products. ■ It is difficult to make decisions, as each decision requires a commitment based on incomplete evaluation. Additionally, since most design problems1.7 Knowledge and Learning During Design
19 are solved by teams, a decision requires consensus, which is often difficult to obtain. ■ Communication of the information developed to others on the design team and to management is an essential part of concurrent engineering. We will return to these observations as the design process is developed through this text. 1.7 KNOWLEDGE AND LEARNING DURING DESIGN When a new design problem is begun, very little may be known about the solution, especially if the problem is a new one for the designer. As work on the project progresses, the designer’s knowledge about the technologies involved and the alternative solutions increases, as shown in Fig. 1.11. Therefore, after completing a project, most designers want a chance to start all over in order to do the project properly now that they fully understand it. Unfortunately, few designers get the opportunity to redo their projects. Throughout the solution process knowledge about the problem and its po- tential solutions is gained and, conversely, design freedom is lost. This can also be seen in Fig. 1.11, where the time into the design process is equivalent to ex- posure to the problem. The curve representing knowledge about the problem is a learning curve; the steeper the slope, the more knowledge is gained per unit time. Throughout most of the design process the learning rate is high. The second curve in Fig. 1.11 illustrates the degree of design freedom. As design decisions are made, the ability to change the product becomes increasingly limited. At the beginning the designer has great freedom because few decisions have been made and little capital has been committed. But by the time the product is in production, Time into design process Percentage 20 40 60 80 100 Design freedom Knowledge about the design problem Figure 1.11 The design process paradox.Parts
» Mechanical engineering design process
» Introduction Measuring the Design Process with Product
» The History of the Design Process The Life of a Product
» The Many Solutions for Design The Basic Actions of Problem Solving
» Summary Mechanical Design Languages
» Different Types of Mechanical Constraints, Goals, and
» Product Decomposition Summary Introduction
» The Individual Designer: A Model of Human Mental Processes That Occur
» Characteristics of Creators The Structure of Design Teams
» Building Design Team Performance Overview of the Design Process
» Designing Quality into Products Product Discovery
» Choosing a Project Summary Sources Exercises On the Web
» Product, Project, and Decision Risk
» In engineering design, the designer uses three types of knowledge: knowl-
» A design process that results in a quality product can be learned, provided
» Improved material on project planning.
» Insist on rights of humanity and nature to coexist
» Recognize interdependence. On the Web
» Accept responsibility for the consequences of design
» Create safe objects of long-term value.
» Eliminate the concept of waste.
» Rely on natural energy flows.
» Understand the limitations of design.
» Seek constant improvement by the sharing of knowledge.
» Respect relationships between spirit and matter.
» Engineering Changes Patent Applications Design for End of Life Sources Placing a piece in a puzzle
» Decompose a simple system such as a home appliance, bicycle, or toy into its assemblies,
» For the device decomposed, list all the important features of one component.
» Select a fastener from a catalog that meets these requirements:
» Sketch at least five ways to configure two passengers in a new four-wheeled commuter
» You are a designer of diving boards. A simple model of your product is a cantilever beam.
» Find five examples of mature designs. Also, find one mature design that has been recently
» Teams develop decisions by consensus rather than by authority. This leads to
» Beneficial team behaviors. Well-defined decision process.
» Use of sound generationevaluation approach.
» Standardizes, organizes, and controls operations.
» Provides for consistent dissemination of information.
» Encourages improvement. Team nam
» Generate alternatives Team nam
» Identify criteria importance Team nam
» Based on the evaluation results, decide what to do next. This decision will
» “What I want for myself out of this.” Refine criteria.
» Refine evaluation—work to gain consensus and reduce uncertainty.
» Choose an alternative—you’ve made a decision, document it and address
» Develop a list of original design problems that you would like to do at least 3. Choose
» Make a list of features you don’t like about products you use. One way to develop this
» Executive summary: Team Members:
» Gantt chart: All diagrams, figures, and tables should be accurately and clearly labeled
» References: Appendices: All diagrams, figures, and tables should be accurately and clearly labeled
» For the features of the redesign problem Exercise 4.2 develop a plan as in Exercise 5.1.
» Develop a plan for making a breakfast consisting of toast, coffee, a fried egg, and juice. Be
» Developing the specifications or goals for the product
» Finding out how the specifications measure the customers’ desires
» Determining how well the competition meets the goals
» Developing numerical targets to work toward
» The QFD method can be applied to the entire problem and any subprob-
» Both competitors have good lifting position when transferring the passenger
» Both products have poor stability. Clearly, this is a market opportunity.
» The Colub is easy to move and Delton is not, need to determine why and do
» For most of adjustment requirements, neither of the competitors score above 3,
» Each specification should measure at least one customers’ requirement at
» Each specification should be measurable. Every specification should be writ-
» The first specification “seat width relative to frame width” is not clear. What
» Two points about specifications that are in terms of “number of steps”:
» For a design problem Exercise 4.1, develop a house of quality and supporting informa-
» The interface to the jam plate. Energy flows between the trigger and the jam
» Articulate the conflicting positions or functions. Identify the needs forcing the two positions.
» Articulate the conflicting positions
» Identify the issue, the objective of the needs
» Articulate injections that can relieve the conflict while meeting the objective.
» Many of the problems that engineers face contain elements that have already
» There are predictable patterns of technological change that can be applied to
» Increase degree of an object’s segmentation
» Arrange objects so they can go into action without time loss
» Stating the overall function.
» Decomposing the overall function into subfunctions. If assumptions are needed to
» Identifying all the objects nouns used and defending their inclusion in the functional
» For the redesign problem Exercise 4.2, apply items a–c from Exercise 7.1 and also study
» Which subfunctions must remain unchanged during redesign?
» Which subfunctions if any must be changed to meet new requirements?
» Which subfunctions may cease to exist?
» For the functional decomposition developed in Exercise 7.1,
» A perpetual motion machine. In recent times the patent office has refused to consider
» Use brainstorming to develop at least 25 ideas for
» A way to fasten together loose sheets of paper.
» A device to keep water off a mountain-bike rider.
» A way to convert human energy to power a boat.
» A method to teach the design process.
» Use brainwriting to develop at least 25 ideas for
» A device to leap tall buildings in a single bound.
» Are the critical parameters identified?
» Are the safe operating latitude and sensitivity of the parameters known?
» Have the failure modes been identified?
» Does hardware exist that demonstrates positive answers to the preceding four
» Is the technology controllable throughout the product’s life cycle?
» The source of the component.
» Wheel and chain must clear frame for all deflections. Wheel should move straight up and down.
» Your body while holding a 5-kg weight straight out in front of you with your
» Maximum acceleration on a standard street
» Maximum acceleration on a 5-cm standard pothole
» Identify the critical parameters and interfaces for evaluation.
» Develop a P-diagram for each.
» Choose whether to build physical models for testing or run an analytical experiment
» Perform the experiments or analysis and develop the most robust product.
» For the redesign problem Exercise 4.2, repeat the steps in Exercise 10.1.
» You have just designed a tennis-ball serving machine. You take it out to the court, turn it
» Does your machine have an accuracy or a variation problem?
» Itemize some of the potential causes of each type of error. Consider the types of
» A new, spring-powered can opener
» A diving board for your new swimming pool
» An art nouveau shelf bracket
» From what material is the component to be machined?
» The overall dimensions are 9.46 cm 3.72 in. by 4.52 cm 77 in. in the
» The wall thickness is 3.2 mm 0.125 in..
» The number of components to be manufactured is 1 million.
» The labor hourly rate is 35.
» Find the Theoretical Minimum Number of Components. Examine each
» hr R Mechanical engineering design process
» For the product developed in response to the design problem begun in Exercise 4.1,
» For the redesign problem begun in Exercise 4.2, estimate the changes in selling price
» Estimate the manufacturing cost for a plastic injection-molded component:
» Compare the costs for manufacturing volumes of 100, 1000, 10,000, and 100,000.
» Compare the cost for a change in tolerance.
» Why does changing the material have virtually no effect on cost at low plastic
» Perform a design-for-assembly evaluation for one of these devices. Based on the results
» A simple toy fewer than 10 parts
» Read as many similar instruction manuals as you can. Many companies post
» Organize instructions into sections to make it easy to find answers. Do not
» Recruit members of the user community not familiar with the product to test
» Know your goals and your vendor’s goals. Building a strong vendor relation-
» Involve vendors early. When dealing with vendors, you cannot afford delays
» Establish relationships. It is important to have vendor partners who under-
» Communicate. Put everything in writing—responsibilities, expected sales
» Stay professional. Things go wrong in life. When they go wrong in a relation-
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