Arrange objects so they can go into action without time loss

7.8 Building a Morphology 207 abstraction. We could begin to correct this situation by abstracting the first item, the hydraulic piston. We could cite instead the use of fluid pressure, a more general concept. Then again, air might be better than hydraulic fluid for the purpose, and we would have to consider the other forms of fluid components that might give more usable forces than a piston. We could refine the “impact of another object” by developing how it will provide the impact force and what the object is that is providing the force. Regardless of what is changed, it is important to try to get all concepts to be equally refined. 7.8.3 Step 3: Combine Concepts The result of applying the previous step is a list of concepts generated for each of the functions. Now we need to combine the individual concepts into complete conceptual designs. The method here is to select one concept for each function and combine those selected into a single design. So, for example, we may consider combining one trigger with a ratchet as part of a free-sliding system with a short stroke. This configuration frees the bar so that it can be easily pushed into position against the work and then uses the ratchet to apply force to the work. A second system is similar but uses a jam plate. These are both shown in Fig. 7.22 by lines connecting the concepts. In the actual Irwin morphology, six concepts were generated and drawn on their CAD system for evaluation. There are pitfalls to this method, however. First, if followed literally, this method generates too many ideas. The one-handed clamp morphology, for exam- ple, is small, yet there are 48 possible designs 2 × 4 × 3 × 2. The second problem with this method is that it erroneously assumes that each function of the design is independent and that each concept satisfies only one function. Generally, this is not the case. For example, if a two-speed system is used, it has both a long and a short stroke and may not work with a linkage. Nonetheless, breaking the function down this finely helps with understanding and concept development. Third, the results may not make any sense. Although the method is a technique for generating ideas, it also encourages a coarse ongoing evaluation of the ideas. Still, care must be taken not to eliminate concepts too readily; a good idea could conceivably be prematurely lost in a cursory evaluation. A goal here is to do only a coarse evaluation and generate all the reasonably possible ideas. In Chap. 8, we will evaluate the concepts and decide between them. Even though the concepts developed here may be quite abstract, this is the time for back-of-the-envelope sketches. Prior to this time, most of the design effort has been in terms of text, not graphics. Now the design is developing to the point that rough sketches must be drawn. Sketches of even the most abstract concepts are increasingly useful from this point on because 1 as discussed in Chap. 3, we remember functions by their forms; thus our index to function is form; 2 the only way to design an object with any complexity is to use sketches to extend the short-term memory; and 208 CHAPTER 7 Concept Generation FH FH FH Product: One-handed bar clamp Organization Name: Irwin Tools Morphology Subfunctions Concept 1 Concept 2 Concept 3 Concept 4 One trigger Move bar Amplify force Team Member: Team Member: Team Member: Team Member: Prepared by: Checked by: Approved by: Long stroke 2 speed system 2 speed system Transform grip force and motion to bar Two triggers Ratchet Rack and pinion Linkage Collect grip force and motion from user Copyright 2008, McGraw-Hill Designed by Professor David G. Ullman Form 15.0 The Mechanical Design Process Jam plate Free sliding Short stroke Figure 7.22 Combining concepts in a Morphology. 3 sketches made in the design notebook provide a clear record of the develop- ment of the concept and the product. Keep in mind that the goal is only to develop concepts and that effort must not be wasted worrying about details. Often a single-view sketch is satisfactory; if a three-view drawing is needed, a single isometric view may be sufficient. 7.9 OTHER IMPORTANT CONCERNS DURING CONCEPT GENERATION The techniques outlined in this chapter have focused on generating potential concepts. In performing these techniques, functional decomposition diagrams, literature and patent search results, function-concept mapping, and sketches of overall concepts are all produced. These are all important documents that can support communication to others and archive the design process. 7.11 Sources 209 One of the highest complements that a product designer can receive is “That looks so simple.” It is difficult to find the elegant, simple solutions to complex problems, yet they generally exist. Engineering elegance is the goal of this chapter and thus, keep the following aphorism in mind at all times: Follow the KISS rule: Keep It Simple, Stupid. Additionally, conceptual design is a good time to review the Hannover Prin- ciples introduced in Chap. 1. Questions derived from the Principles that should be asked at this time are 1. Do your concepts enable humanity and nature to coexist in a healthy, sup- portive, diverse, and sustainable condition? 2. Do you understand the effects of your concepts on other systems, even the distant effects? 3. Are concepts safe and of long-term value?. 4. Do your concepts help eliminate the concept of waste throughout their life cycle? 5. Where possible, do they rely on natural energy flows? 7.10 SUMMARY ■ The functional decomposition of existing products is a good method for understanding them. ■ Functional decomposition encourages breaking down the needed function of a device as finely as possible, with as few assumptions about the form as possible. ■ The patent literature is a good source for ideas. ■ Exploring contradictions can lead to ideas. ■ Listing concepts for each function helps generate ideas; this list is often called a morphology. ■ Sources for conceptual ideas come primarily from the designer’s own exper- tise; this expertise can be enhanced through many basic and logical methods. 7.11 SOURCES Sources for patent searches http:www.uspto.govpatftindex.html. The website for the U.S. Patent and Trademark Office. Easy to search but has complete information only on recent patents. http:www.delphion.comhome. IBM originally developed this website. Also, easy to search for recent patents. 210 CHAPTER 7 Concept Generation http:gb.espacenet.com. Source for European and other foreign patents. Supported by the European Patent Organization, EPO. Other non-patent sources Artobolevsky, I. I.: Mechanisms in Modern Engineering Design, MIR Publishers, Moscow, 1975. This five-volume set of books is a good source for literally thousands of different mechanisms, many indexed by function. Chironis, N. P.: Machine Devices and Instrumentation, McGraw-Hill, New York, 1966. Similar to Greenwood’s Product Engineering Design Manual. Chironis, N. P.: Mechanism, Linkages and Mechanical Controls, McGraw-Hill, New York, 1965. Similar to the last entry. Clausing, D., and V. Fey: Effective Innovation: The Development of Winning Technologies, ASME Press 2004. A good overview of recent methods to develop new concepts. Damon,A., H. W. Stoudt, and R.A. McFarland: The Human Body in Equipment Design, Harvard University Press, Cambridge, Mass., 1966. This book has a broad range of anthropometric and biomechanical tables. Design News, Cahners Publishing, Boston. Similar to Machine Design. http:www.designnews. com Edwards, B.: Drawing on the Right Side of the Brain, Tarcher, Los Angeles, 1982. Although not oriented specifically toward mechanical objects, this is the best book available for learning how to sketch. Greenwood, D. C.: Engineering Data for Product Design, McGraw-Hill, New York, 1961. Similar to the above. Greenwood, D. C.: Product Engineering Design Manual, Krieger, Malabar, Fla., 1982. A compendium of concepts for the design of many common items, loosely organized by function. Human Engineering Design Criteria for Military Systems, Equipment, and Facilities, MILSTD 1472, U.S. Government Printing Office, Washington, D.C. This standard contains 400 pages of human factors information. A reduced version with links to other material is at http:hfetag.dtic.milhfs_docs.html Machine Design, Penton Publishing, Cleveland, Ohio. One of the best mechanical design mag- azines published, it contains a mix of conceptual and product ideas along with technical articles. It is published twice a month. www.machinedesign.com. Norman, D.: The Psychology of Everyday Things, Basic Books, New York, 1988. This book is light reading focused on guidance for designing good human interfaces. Plastics Design Forum, Advanstar Communications Inc., Cleveland, Ohio. A monthly maga- zine for designers of plastic products and components. Product Design and Development, Chilton, Radnor, Pa. Another good design trade journal. www.pddnet.com. Thomas Register of American Manufacturers, Thomas Publishing, Detroit, Mich. This 23- volume set is an index of manufacturers and is published annually. Best used on the Web at www.thomasregister.com. TRIZ www.triz-journal.com. The TRIZ Journal is a good source for all things TRIZ. Functional decomposition or reverse engineering case studies for coffeemaker, bicycle, engine, and other products developed by student of Professor Tim Simpson Pennsylvania State University and others: http:gicl.cs.drexel.eduwikiReverse_Engineering_Case_Studies 7.13 On the Web 211 7.12 EXERCISES 7.1 For the original design problem Exercise 4.1, develop a functional model by

a. Stating the overall function.

b. Decomposing the overall function into subfunctions. If assumptions are needed to

refine this below the first level, state the assumptions. Are there alternative decom- positions that should be considered?

c. Identifying all the objects nouns used and defending their inclusion in the functional

model.

7.2 For the redesign problem Exercise 4.2, apply items a–c from Exercise 7.1 and also study

the existing devices to establish answers to these questions. a. Which subfunctions must remain unchanged during redesign? b. Which subfunctions if any must be changed to meet new requirements? c. Which subfunctions may cease to exist?

7.3 For the functional decomposition developed in Exercise 7.1,

a. Develop a morphology as in Fig. 7.21 to aid in generating concepts. b. Combine concepts to develop at least 10 complete conceptual designs. 7.4 For the redesign problem functions that have changed in Exercise 7.2, a. Generate a morphology of new concepts as in Fig. 7.21. b. Combine concepts to develop at least five complete conceptual designs. 7.5 Find at least five patents that are similar to an idea that you have for a. The original design problem begun in Exercise 4.1. b. The redesign problem begun in Exercise 4.2.

c. A perpetual motion machine. In recent times the patent office has refused to consider

such devices. However, the older patent literature has many machines that violate the basic energy conservation laws.

7.6 Use brainstorming to develop at least 25 ideas for

a. A way to fasten together loose sheets of paper.

b. A device to keep water off a mountain-bike rider.

c. A way to convert human energy to power a boat.

d. A method to teach the design process.

7.7 Use brainwriting to develop at least 25 ideas for

a. A device to leap tall buildings in a single bound.

b. A way to fasten a gear to a shaft and transmit 500 watts.

7.8 Finish reverse engineering the one-handed bar clamp in Figure 7.7 7.9 Choose a relatively simple product and functionally decompose it to find the flow of force, energy and information. 7.13 ON THE WEB Templates for the following documents are available on the book’s website: www.mhhe.comUllman4e ■ Reverse Engineering ■ Morphology 8 C H A P T E R Concept Evaluation and Selection KEY QUESTIONS ■ How can rough conceptual ideas be evaluated without refining them? ■ What is technology readiness? ■ What is a Decision Matrix? ■ How can I manage risk? ■ How can I make robust decisions? 8.1 INTRODUCTION In Chap. 7, we developed techniques for generating promising conceptual solu- tions for a design problem. In this chapter, we explore techniques for choosing the best of these concepts for development into products. The goal is to expend the least amount of resources on deciding which concepts have the highest potential for becoming a quality product. The difficulty in concept evaluation and decision making is that we must choose which concepts to spend time developing when we still have very limited knowledge and data on which to base this selection. How can rough conceptual ideas be evaluated? Information about concepts is often incomplete, uncertain, and evolving. Should time be spent refining them, giving them structure, making them measurable so that they can be compared with the engineering targets developed during problem specifications development? Or should the concept that seems like the best one be developed in the hope that it will become a quality product? It is here that we address the question of how soon to narrow down to a single concept. Ideally, enough information about each concept is known at this point to make a choice and put all resources into developing this one concept. However, it is less risky to refine a number of concepts before committing to one of them. This requires resources spread among many concepts and, possibly, inadequate 213 214 CHAPTER 8 Concept Evaluation and Selection development of any one of them. Many companies generate only one concept and then spend time developing it. Others develop many concepts in parallel, eliminating the weaker ones along the way. Designers at Toyota follow what they call a “parallel set narrowing process,” in which they continue parallel develop- ment of a number of concepts. As more is learned, they slowly eliminate those concepts that show the least promise. This has proven very successful, as seen by Toyota’s product quality and growth. Every company has its own culture for product development and there is no one “correct” number of concepts to select. Here we try to balance learning about the concepts with limited resources. In this chapter, techniques will be developed that will help in making a knowledgeable decision with limited information. As shown in Fig. 8.1, after generating concepts, the next step that needs to be accomplished is evaluating them. The term evaluate, as used in this text, implies comparison between alternative concepts relative to the requirements they must Refine concepts Generate concepts Evaluate concepts Make concept decisions Document and communicate Refine plan Approve concepts To product design Refine specifications Cancel project Figure 8.1 The conceptual design phase.

8.2 Concept Evaluation Information

215 If the horse is dead, get off. meet. The results of evaluation give the information necessary to make concept decisions . Be ready during concept evaluation to abandon your favorite idea, if you cannot defend it in a rational way. Also, abandon if necessary “the way things have always been done around here.” Reflect on the above aphorism and, if it applies, use it. Before we get into the details of this chapter, it is worth reflecting on the basic decision-making process introduced in Chap. 4 where we were selecting a project. In Fig. 8.2 a reprint of Fig. 4.19, the issue is “Select a concepts to develop.” We have spent considerable time generating alternatives and criteria. Now we must focus on the remaining steps and decide what to do next. First, we will discuss the types of evaluation information we have available to us, and then we will address different traditional methods for decision making. The criteria importance step 4 will not really surface until Section 8.5. The traditional decision-making methods do not do a good job of helping you manage risk and uncertainty. This will be addressed in Section 8.6, and a robust decision-making method, designed for managing uncertainty will be introduced in Section 8.7. Finally, the documentation and communication needs of conceptual design will be detailed. 8.2 CONCEPT EVALUATION INFORMATION In order to be compared, alternatives and criteria must be in the same language and they must exist at the same level of abstraction. Consider, for example, the spatial requirement that a product fit in a slot 2.000 ±0.005 in. long. An unrefined concept for this product may be described as “short.” It is impossible to compare “2.000 ± 0.005 in.” to “short” because the concepts are in different languages— a number versus a word—and they are at different levels of abstraction—very concrete versus very abstract. It is simply not possible to make a comparison between the “short” concept and the requirement of fitting a 2.000 ± 0.005 in. slot. Either the requirement will have to be abstracted or work must be done on the concept to make “short” less abstract or both. An additional problem in concept evaluation is that abstract concepts are uncertain; as they are refined, their behavior can differ from that initially antic- ipated. The greater the knowledge, the less the uncertainty about a concept and the fewer the surprises as it is refined. However, even in a well-known area, as the concept is refined to the product, unanticipated factors arise. Richard Feynman, the Nobel winning physicist said: “If you thought that science was certain— well that is just an error on your part.” A major factor is to manage the uncertain information on which most decisions are based; there is uncertainty in everything.