What is Engineering Design Process ( Mechanical Design Engineer ) ?

The engineering design process can be used to achieve several different outcomes. One is the design of products, whether they be consumer goods such as refrigerators, power tools, or DVD players, or highly complex products such as a missile system or a jet transport plane. Another is a complex engineered system such as an electrical power generating station or a petrochemical plant, while yet another is the design of a building or a bridge. However, the emphasis in this text is on product design because it is an area in which many engineers will apply their design skills. Moreover, examples taken from this area of design are easier to grasp without extensive specialized knowledge. This chapter presents the engineering design process from three perspectives. Inthe design method is contrasted with the scientific method, and design is presented as a five-step problem-solving methodology. the role of design beyond that of meeting technical performance requirements and introduces the idea that design must meet the needs of society at large. lays out a cradle-to-the-grave road map of the design process, showing that the responsibility of the engineering designer extends from the creation of a design until its embodiment is disposed of in an environmentally safe way. Chapter 2 extends the engineering design process to the broader issue of product development by introducing more business oriented issues such as product positioning and marketing.

1. Importance of the Engineering Design Process

In the 1980's when companies in the United States first began to seriously feel the impact of quality products from overseas, it was natural for them to place an empha- sis on reducing their manufacturing costs through automation and moving plants to lower-labor-cost regions. However, it was not until the publication of a major study of the National Research Council (NRC)3 that companies came to realize that the real key to world-competitive products lies in high-quality product design. This has stimu- lated a rash of experimentation and sharing of results about better ways to do product design. What was once a fairly cut-and-dried engineering process has become one of the cutting edges of engineering progress. This text aims at providing you with insight into the current best practices for doing engineering design. The importance of design is nicely summed up in Fig. This shows that only a small fraction of the cost to produce a product ( 5 percent) is involved with the design process, while the other 95 percent of cost is consumed by the materials, capital, and labor to manufacture the product. However, the design process consists of the accumulation of many decisions that result in design commitments that affect about 70 to 80 percent of the manufactured cost of the product. In other words, the decisions made beyond the design phase can influence only about 25 percent of the total cost. If the design proves to be faulty just before the product goes to market, it will cost a great deal of money to correct the problem. To summarize: Decisions made in the design process cost very little in terms of the overall product cost but have a major effect on the cost of the product. The second major impact of design is on product quality. The old concept of prod- uct quality was that it was achieved by inspecting the product as it came off the production line. Today we realize that true quality is designed into the product. Achieving quality through product design will be a theme that pervades this book. For now we point out that one aspect of quality is to incorporate within the product the performance and features that are truly desired by the customer who purchases the product. In addition, the design must be carried out so that the product can be made without defect at a competitive cost. To summarize: You cannot compensate in manufacturing for defects introduced in the design phase. The third area where engineering design determines product competitiveness is product cycle time. Cycle time refers to the development time required to bring a new product to market. In many consumer areas the product with the latest “bells and whistles” captures the customers’ fancy. The use of new organizational methods, the widespread use of computer-aided engineering, and rapid prototyping methods are contributing to reducing product cycle time. Not only does reduced cycle time increase the marketability of a product, but it reduces the cost of product development. Furthermore, the longer a product is available for sale the more sales and profits there will be. To summarize: The design process should be conducted so as to develop quality, cost-competitive products in the shortest time possible.

crease the marketability of a product, but it reduces the cost of product development. Furthermore, the longer a product is available for sale the more sales and profits there will be. To summarize: The design process should be conducted so as to develop quality, cost-competitive products in the shortest time possible.

2. Types of Designs 

Engineering design can be undertaken for many different reasons, and it may take different forms. 

● Original design, also called innovative design . This form of design is at the top of the hierarchy. It employs an original, innovative concept to achieve a need. Some- times, but rarely, the need itself may be original. A truly original design involves invention. Successful original designs occur rarely, but when they do occur they usually disrupt existing markets because they have in them the seeds of new technology of far-reaching consequences. The design of the microprocessor was one such original design. 

● Adaptive design . This form of design occurs when the design team adapts a known solution to satisfy a different need to produce a novel application. For example, adapting the ink-jet printing concept to spray binder to hold particles in place in a rapid prototyping machine. Adaptive designs involve synthesis and are relatively common in design. 

● Redesign . Much more frequently, engineering design is employed to improve an existing design. The task may be to redesign a component in a product that is fail- ing in service, or to redesign a component so as to reduce its cost of manufacture. Often redesign is accomplished without any change in the working principle or concept of the original design. For example, the shape may be changed to reduce a 1 1 6 engineering design stress concentration, or a new material substituted to reduce weight or cost. When redesign is achieved by changing some of the design parameters, it is often called variant design. 

● Selection design. Most designs employ standard components such as bearings, small motors, or pumps that are supplied by vendors specializing in their manufacture and sale. Therefore, in this case the design task consists of selecting the components with the needed performance, quality, and cost from the catalogs of potential vendors.

● Industrial design. This form of design deals with improving the appeal of a product to the human senses, especially its visual appeal. While this type of design is more artistic than engineering, it is a vital aspect of many kinds of design. Also encompassed by industrial design is a consideration of how the human user can best inter- face with the product.

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