Problem-Solving Methodology of Engineering Design

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Problem-Solving Methodology of Engineering Design

Post by subham »

Designing can be approached as a problem to be solved. A problem-solving methodology that is useful in design consists of the following steps.

● Definition of the problem
● Gathering of information
● Generation of alternative solutions
● Evaluation of alternatives and decision making
● Communication of the results

This problem-solving method can be used at any point in the design process, whether at the conception of a product or the design of a component.

Definition of the problem

The most critical step in the solution of a problem is the problem definition or formulation. The true problem is not always what it seems at first glance. Because this step seemingly requires such a small part of the total time to reach a solution, its importance is often overlooked. Figure 1 illustrates how the final design can differ greatly depending upon how the problem is defined.

Problem definition often is called needs analysis. While it is important to identify the needs clearly at the beginning of a design process, it should be understood that this is difficult to do for all but the most routine design. It is the nature of the design process that new needs are established as the design process proceeds because new problems arise as the design evolves. At this point, the analogy of design as problem solving is less fitting. Design is problem solving only when all needs and potential issues with alternatives are known. Of course, if these additional needs require reworking those parts of the design that have been completed, then penalties are incurred in terms of cost and project schedule. Experience is one of the best remedies for this aspect of designing, but modern computer-based designs tools help ameliorate the effects of inexperience.

Gathering Information

Perhaps the greatest frustration you will encounter when you embark on your first design project will be either the dearth or the plethora of information. No longer will your responsibility stop with the knowledge contained in a few chapters of a text. Your assigned problem may be in a technical area in which you have no previous background, and you may not have even a single basic reference on the subject. At the other extreme you may be presented with a mountain of reports of previous work, and your task will be to keep from drowning in paper. Whatever the situation, the immediate task is to identify the needed pieces of information and find or develop that information.
An important point to realize is that the information needed in design is different from that usually associated with an academic course. Textbooks and articles published in the scholarly technical journals usually are of lesser importance. The need often is for more specific and current information than is provided by those sources. Technical reports published as a result of government-sponsored R&D, company reports, trade journals, patents, catalogs, and handbooks and literature published by vendors and suppliers of material and equipment are important sources of information. The Internet is becoming a very useful resource. Often the missing piece of information can be supplied by an Internet search, or by a telephone call or an e-mail to a key supplier. Discussions with in-house experts (often in the corporate R&D center) and outside consultants may prove helpful.
The following are some of the questions concerned with obtaining information:

What do I need to find out?
Where can I find it and how can I get it?
How credible and accurate is the information?
How should the information be interpreted for my specific need?
When do I have enough information?
What decisions result from the information?

Generation of Alternative Solutions
Generating alternative solutions or design concepts involves the use of creativity stimulation methods, the application of physical principles and qualitative reasoning, and the ability to find and use information. Of course, experience helps greatly in this task. The ability to generate high-quality alternative solutions is vital to a successful design.

Evaluation of Alternatives and Decision Making
The evaluation of alternatives involves systematic methods for selecting the best among several concepts, often in the face of incomplete information. Engineering analysis procedures provide the basis for making decisions about service performance. Design for manufacturing analyses and cost estimation provide other important information. Various other types of engineering analysis also provide information. Simulation of performance with computer models is finding wide usage. Simulated service testing of an experimental model and testing of full sized prototypes often provide critical data. Without this quantitative information it is not possible to make valid evaluations.
An important activity at every step in the design process, but especially as the design nears completion, is checking. In general, there are two types of checks that can be made: mathematical checks and engineering-sense checks. Mathematical checks are concerned with checking the arithmetic and the equations for errors in the conversion of units used in the analytical model. Incidentally, the frequency of careless math errors is a good reason why you should adopt the practice of making all your design calculations in a bound notebook. In that way you won’t be missing a vital calculation when you are forced by an error to go back and check things out. Just draw a line through the section in error and continue. It is of special importance to ensure that every equation is dimensionally consistent.
Engineering-sense checks have to do with whether the answers “seem right.” Even though the reliability of your intuition increases with experience, you can now develop the habit of staring at your answer for a full minute, rather than rushing on to do the next calculation. If the calculated stress is 106 psi, you know something went wrong! Limit checks are a good form of engineering-sense check. Let a critical parameter in your design approach some limit (zero, infinity, etc.), and observe whether the equation behaves properly.
We have stressed the iterative nature of design. An optimization technique aimed at producing a robust design that is resistant to environmental influences (water vapor, temperature, vibration, etc.) most likely will be employed to select the best values of key design parameters.

Communication of the Results
It must always be kept in mind that the purpose of the design is to satisfy the needs of a customer or client. Therefore, the finalized design must be properly communicated, or it may lose much of its impact or significance. The communication is usually by oral presentation to the sponsor as well as by a written design report. Surveys typically show that design engineers spend 60 percent of their time in discussing designs and preparing written documentation of designs, while only 40 percent of the time is spent in analyzing and testing designs and doing the designing. Detailed engineering drawings, computer programs, 3-D computer models, and working models are frequently among the “ deliverable” to the customer.
It hardly needs to be emphasized that communication is not a one-time occurrence to be carried out at the end of the project. In a well-run design project there is continual oral and written dialog between the project manager and the customer.
Note that the problem-solving methodology does not necessarily proceed in the order just listed. While it is important to define the problem early on, the understanding of the problem improves as the team moves into solution generation and evaluation. In fact, design is characterized by its iterative nature, moving back and forth between partial solutions and problem definition. This is in marked contrast with engineering analysis, which usually moves in a steady progression from problem setup to solution.

Problem-Solving Methodology of Engineering Design



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