CHAPTER 2 Engineering GeometryINTRODUCTION
Technical graphics is an integral part of the engineering design process through which engineers and drafters/designers generate new ideas and solve problems. Traditionally, engineering design consisted of closely related steps documented as paper graphics and text which flowed in a linear/sequential manner through an organization. In the face of increased global competition, many industries in the United States have a adopted a team-oriented concurrent approach using 3-D CAD model information as a primary means for communication. This chapter describes a modern approach to the engineering design process, so that you will have a better understanding of and appreciation for the role of engineering graphics in the design process.
DESIGNDesign is the process of conceiving or inventing ideas mentally and communicating these ideas to others in a form that is easily understood. Most often the communications tool is graphics. |
2.1Design is used for two primary purposes: personal expression, and product or process development.
Design for personal expression, usually associated with art, is divided into concrete (realistic) and abstract design and is often a source of beauty and interest.
When a design serves some useful purpose, such as the shape of a new automobile wheel, it is classified as a design for product or process development. Aesthetic design is concerned with the look and feel of a product. Functional design is concerned with the function of a product or process. Function means that a product possesses a form related directly to the purpose of that product. |
2.2Engineering design is a problem-solving process that uses knowledge, resources, and existing products to create new goods and processes. Engineering design has both aesthetic and functional elements and can be broken into two broad categories: product design and system design. Product Design is the process used to create new products, such as a new automobile model, a new appliance, and a new type of wheelchair. Product design is a complex activity that includes market, production, sales, service, function, and profit analyses used to produce a product that meets the wants and needs of the consumer, is economically produced, is safe for the consumer and the environment, and is profitable to the company. System design is the process used to create a new system or process. A system is an orderly arrangement of parts that are combined to serve one general function. Examples of the system designs are: the arrangement of the assembly process in a factory; the heating, ventilation, and air-conditioning (HVAC) system in a structure; and the electrical system in the automobile. |
2.2.1Engineering design is one of the processes normally associated with the entire business or enterprise, from receipt of the order or product idea, to maintenance of the product, and all stages in between. An engineering design involves both a process and a product. A process is a series of continuous actions ending in a particular result. A product is anything produced as a result of some process. Graphics is an extremely important part of the engineering design process, which uses graphics as a tool to visualize possible solutions and to document the design for communications purposes.
Traditional engineering design is a linear approach divided into a number of steps. For example, a six-step process might be divided into: problem identification, preliminary ideas, refinement, analysis, documentation, and implementation. The design process moves through each step in a sequential manner; however, if problems are encountered, the process may return to a previous step. This repetitive action is called iteration or looping. |
2.2.2Concurrent engineering is a nonlinear team approach to design that brings together the input, processes, and output elements necessary to produce a product.
The concurrent engineering model shows how every area in an enterprise is related, and the CAD database is the common thread of information between each area.
The engineering design process consists of three overlapping areas: ideation, refinement, and implementation which all share the same CAD database. |
2.2.3Collaborative engineering has evolved from concurrent engineering into a true enterprise-wide integrated product development process. It creates an organizational environment where teams can effectively collaborate with shared product information databases. Collaborative engineering is based on empowered, cross-functional teams and low-level decision-making. |
2.2.4Collaborative engineering is highly dependent on computer-based tools, including those that support virtual product representation. Tools in this category include shaded CAD models, large assembly visualizations, and dynamic simulations for design and manufacturing. |
2.2.5Prototyping encompasses the creation of physical representations of the proposed design using traditional machining or rapid prototyping technology. |
2.2.6Productivity tools support the engineering design process. They include e-mail, word processing, and spreadsheet software. |
2.2.7Product Data Management (PDM) is the name given to specific computer-based tools and processes used to manage engineering and technical data associated with the product development process. Enterprise Data Management (EDM) describes similar systems used to manage information at the enterprise level. |
2.2.8-10Modern data networks are used to both manage the product development process within a company (using Intranets) and support sales and support of the product in the field (using
Extranets). The use of Internet for conducting business is often called e-Business. |
2.2.11The actual members of a design team will vary according to the complexity and type of product being designed and the stage of the design process. The size of the design team may vary from one, to three, to many dozen. Coordination of the design team is critical to the success of the design and meeting deadlines. As mentioned earlier, design teams are an integral part of concurrent engineering. |
2.2.12Members of the design team include: - product design engineer - product manager - mechanical engineer - electrical engineer - manufacturing engineer - software engineer - detailer/drafter - materials engineer - quality control engineer - industrial designer - vendor representatives |
2.3Ideation is a structured approach to thinking for the purpose of solving a problem. The ideation process consists of three important steps: problem identification, preliminary ideas, and preliminary design. |
2.3.1Problem identification is an ideation process in which the parameters of the design project are set before an attempt is made to find a solution to the design. Problem identification includes the following elements: Problem statement summarizes the problem to be solved. Research gathers relevant information useful to the design team. Data gathering, sometimes called feasibility study determines: market needs, benchmarking with the competition, and rough physical measurements, such as weight and size. Objectives list the things to be accomplished by the team. Limitations list the factors in the design specifications. Scheduling organizes activities into a sequence. Engineering design problems must be clearly defined before the design process can begin. The problem definition requires input from customers, marketing, management, and engineering. Data to determine consumer needs is gathered through surveys, such as personal or telephone interviews, mail questionnaires, and focus groups. After all the data is gathered, the information is shared with the team before preliminary ideas are developed. Presentation graphics are a tool used to display the data in the form of charts and graphs, and are thus an important element in the information-sharing process. Scheduling of the design activities is one of the last stages in problem identification. Objectives specifically state what is to be accomplished during the design process. |
PRELIMINARY IDEAS STATEMENT |
2.3.2After the problem identification is complete, the design team begins to develop preliminary ideas for solving the problem. Brainstorming is the process of identifying as many solutions to a problem as possible. |
2.3.3In the ideation phase, rough sketches and conceptual computer models, called ideation drawings or models are produced. Ideation drawings communicate new ideas through the use of rough sketches and computer models. |
2.3.4Inventive or creative ideas can come from a number of sources. Both personal sources and outside sources — such as surveys, competition reviews, library reference material, and vendor catalogues — can be used for inspiration. |
2.3.5A design notebook should be used to record all ideas, no matter how insignificant they seem at the time. A well-documented notebook is critical for recording ideas for later synthesis and to provide legal groundwork for patents and other proof of intellectual ownership. |
2.4Refinement is a repetitive (iterative or cyclical) process used to test the preliminary design, make changes if necessary, and determine if the design meets the goals of the project. The refinement stage normally begins with technicians using the rough sketches and computer models to create dimensionally accurate drawings and models. The refinement stage is heavily dependent on graphics to document, visualize, analyze, and communicate the design idea. Refinement drawings are technical drawings and models used to analyze preliminary design ideas. |
2.4.1Modeling is the process of representing abstract ideas, words, and forms, through the orderly use of simplified text and images. A descriptive model presents abstract ideas, products, or processes in a recognizable form. A predictive model is one that can be used to understand and predict the behavior/performance of ideas, products or processes. A mathematical model uses mathematical equations to represent system components. A scale model is a physical model created to represent system components. Rapid prototyping is a broad term used to describe several related processes that create real models directly from a 3-D CAD database. Virtual reality (VR) systems offer a way to visualize a model more realistically than on a traditional computer display. By using the principals of human perception, a completely immersive environment in which the user experiences the model. |
COMPUTER SIMULATION AND ANIMATION |
2.4.2Computer simulation is the precise modeling of complex situations that involve a time element. Computer animation is the imprecise modeling of complex situations that involve a time element. The major difference between simulation and animation is the degree of precision. An animation only approximately replicates a real situation; a simulation accurately replicates a real situation. |
2.4.3Design analysis is the evaluation of a proposed design, based on the criteria established in the ideation phase. It is the second major area within the refinement process, and the whole design team is involved. Typical analyses performed on designs include: Property analysis, which evaluates a design based on its physical properties. Functional analysis, which determines if the design does what it is intended to do. Human factors analysis, which evaluates a design to determine if the product serves the physical, emotional, quality, mental, and safety needs of the consumer. Aesthetic analysis, which evaluates a design based on its aesthetic qualities. Market analysis, which determines if the design meets the needs of the consumer, based on the results of surveys or focus groups. Financial analysis, which determines if the price of the proposed design will be in the projected price range set during the ideation phase. Finite element modeling (FEM) is an analytical tool used in solid mechanics to determine the static and dynamic responses of components under various conditions, such as different temperatures. Discretization is the process that divides a solid model into smaller, discrete parts such as triangles and rectangles. Each corner of these elements is called a node. After the finite element is created, the boundary conditions, such as temperature or load, are defined. The model is then analyzed by a computer. Mechanism analysis is concerned with the calculation of motions and loads in mechanical systems comprised of rigid bodies connected by joints. Assembly analysis is used to define the individual rigid bodies of the mechanism and to assemble them correctly, considering both geometry and velocities. Kinematic analysis determines the motion of assemblies without regard to the loads. Dynamic analysis determines the loads that drive or create the motion of a mechanism. Functional analysis is a judgment process in which factors, such as cost, appearance, profitability, marketability, safety, and others, are used to determine the worth of a design. Human factors analysis determines how a design interacts with the dimensions, range of motion, senses, and mental capabilities of the population that will use the product. Aesthetic analysis is a process that evaluates a design based on aesthetic qualities. The look and feel of the product are analyzed by industrial designers, marketing personnel, environmental and human factors engineers, and the customer. Market analysis determines the needs and wants of the customer so that the product produced is the product wanted by the consumer. Financial analysis determines the capital available for a project, the projected expenses to design, manufacture, assemble, market, and service a product. Graphical analysis is a process used in engineering analysis to display empirical data in the form of graphics. |
2.5A design review is a formal meeting where the design team presents and defends their progress towards a solution to management. Graphic communication plays a key role in presenting the designs to meeting participants and providing a basis for discussion. |
2.6Implementation is the third and final phase in concurrent engineering design and is the process used to change the final design from an idea into a product, process, or structure. |
2.6.1The planning process determines the most effective method of moving a product through the production cycle. Modern planning techniques include: computer-aided process planning (CAPP), material requirement planning (MRP), and just-in-time (JIT) scheduling. CAPP uses the computer model of the design to determine which machines and processes should be used. MRP calculates the raw materials needed to produce the product, and uses solid models to assist in these calculations. Just-in-time (JIT) is an operational philosophy that tries to reduce cycle time while eliminating waste. A JIT system prevents waste by taking deliveries on orders only as they are needed. |
2.6.2Production is the process used to transform raw materials into finished products and structures, using labor, equipment, capital, and facilities. |
2.6.3The marketing process anticipates customer needs and directs the flow of goods from the producer to the consumer. Computer models and technical drawings can be used as the basis to create the illustrations needed. Motorola marketing example. |
2.6.4The finance process analyzes the feasibility of producing a product, relative to capital requirements and return on investment (ROI). |
2.6.5Management is the logical organization of people, materials, energy, equipment, and procedures into work activities designed to produce a specified end result, such as a product. Total quality management (TQM) is the process of managing the organization as a whole, such that it excels in all areas of production and service that are important to the customer. The key concepts are: (1) quality is applicable throughout the organization in everything it does; and (2) quality is defined by the customer. Design qualitythe inherent value of the product in the marketplace. |
2.6.6Service is an activity which supports the installation, training, maintenance, and repair of a product or structure for the consumer. Service uses technical illustrations and reports to support its activities. Technical illustrations are typically assembly drawings which show how multiple parts fit together, pictorial drawings, rendered illustrations, and graphics showing the order of assembly, as well as the functionality, of the components of the product. |
2.6.7Documentation is a process used to formally record and communicate the final design solution. Concurrent documentation is a process that creates documents at the same time that t he product design is being developed. Design drawings and models are all the sketches, rough design layout drawings, and initial 3-D computer models created during the ideation and refinement phases. Multiview dimensioned drawings and assembly drawings with a parts list are for production purposes. These multiview drawings are called production drawings because they are used as the communications medium between design and production or manufacturing. If the design is modeled in 3-D by CAD, then multiview drawings can automatically be extracted from the model. Another purpose for engineering drawings is archiving, which is a process used to create a permanent graphics record of the design in the form of drawings saved on vellum, microfiche, computer tape, or some other medium. It is possible to create a product without the use of paper drawings by linking the entire business to computers. Technical illustrations are developed and used throughout the concurrent engineering and documentation cycle, starting with the design database. Animations are used in the documentation phase to support the marketing, training, production, and service activities. Technical reports are in-depth accounts that chronicle the design process. Presentation graphics are text, illustrations, and other visual aids used when making an oral report to a group. A patent is the “right to exclude others from making, using, or selling .” The patenting process was developed to encourage the prompt disclosure of technical advances by granting a limited period of protection for the exclusive use of that advance. A patent is granted for a period of 17 years. |
2.7.1Product data control involves managing all information associated with a product. PDM/EDM systems are central to this process. Enterprise Document (or Data) Management (EDM) is a software system used to track all data generated by an enterprise, whether it is directly related to the design process or not. These databases are often linked to other database systems, including PDM systems. Product Data Management (PDM) is the name given to specific computer-based tools and processes used to manage engineering and technical data associated with the product development process. Networked computer systems are used to manage and distribute the PDM database information. Individuals working at CAD workstations (the clients) can access the database located on a central server through the network. The client software allows the user to search for documents by database fields such as the part name, file name, who created the data, or the last date revised. The software usually provides a viewer for previewing the selected document. The PDM system provides tools to update, manage, and secure engineering data. In addition, the system typically provides some means of managing the workflow of design information. Wide area network tools on the Internet such as the World Wide Web are being used to distribute and manage engineering data among remote locations of global companies. |
2.7.2Even small organizations should have file management protocols in place. These include file naming conventions, saving, and backup procedures. |
2.7.3ISO 9000 is a set of quality standards that promote and facilitate international commerce. An important part of these standards is the documentation of all processes that affect the quality of service in your organization. |
OTHER ENGINEERING DESIGN METHODS |
2.12Design for manufacturability (DFM) is a design technique in which the design is developed by a team, and the focus is on simplicity and functionality. Knowledge-based engineering (KBE) systems complement CAD by adding the engineering knowledge necessary for a product’s design. Reverse engineering is a method of taking an existing product, accurately evaluating it, and putting the information into a CAD database. |
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2002 McGraw-Hill Higher Education