CHAPTER 11 The Engineering Design Process
INTRODUCTION
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 that flowed in a linear/sequential manner through an organization. In the face of increased global competition, many industries in the United States have 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 you will have a better understanding of and appreciation for the role of engineering graphics in the design process.
11.1 design
Design 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.
Design 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.
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 systems engineer or industrial engineer is an engineer who specializes in designing systems. A system is an orderly arrangement of parts that are combined to serve one general function.
11.2 ENGINEERING DESIGN
Engineering 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.
Engineering 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.
Concurrent 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.
Collaborative 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.
Collaborative 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.
Prototyping encompasses the creation of physical representations of the proposed design using traditional machining or rapid prototyping technology.
Productivity tools support the engineering design process. They include e-mail, word processing, and spreadsheet software.
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. Enterprise Data Management (EDM) describes similar systems used to manage information at the enterprise level.
Modern 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.
The manufacture of a new product now calls for the involvement of all the company’s departments: engineering, strategy, marketing and sales, planning and production, procurement, finance, and human resources. Product Lifecycle Management (PLM) is a model that facilitates the simultaneous working of all these departments. It makes it possible to create, manage, simulate, share, and communicate digitally all the information related to the company’s products, processes, and resources, optimizing its overall performance.
PLM is a strategic business approach for the effective management and use of corporate intellectual capital. Corporate intellectual capital (CIC) is the sum of retained knowledge that an organization accumulates in the course of delivering its products.
The 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.
Members of the design team include:
Not all designs are totally new designs of products. In fact, most designs have at least some common features with a previous design. Design projects are grouped as:
11.3 ideation
Ideation 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.
Problem 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 tools 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.
After 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.
In 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.
Inventive 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.
A 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.
11.4 REFINEMENT
Refinement 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.
Modeling 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 is created.
Computer 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.
Design 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, and 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.
11.5 design review meetings
A 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.
11.6 IMPLEMENTATION
Implementation 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.
The 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.
Production is the process used to transform raw materials into finished products and structures, using labor, equipment, capital, and facilities.
The 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.
The finance process analyzes the feasibility of producing a product, relative to capital requirements and return on investment (ROI).
Management 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 quality is the inherent value of the product in the marketplace.
Service is an activity that 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 that 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.
Documentation 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 the 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.
11.7 drawing control
Product 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.
Even small organizations should have file management protocols in place. These include file-naming conventions, saving, and backup procedures.
ISO 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.
11.8 Other Engineering design Methods
Design 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.
Virtual reality (VR) is an emerging technology that is beginning to be more commonly used in engineering design and manufacturing. Since this technology is still relatively new, often the terms are used incorrectly or misunderstood. There are four closely interrelated terminologies:
In general, virtual reality is a three-dimensional (3-D) (in most cases, but not always), computer-generated, simulated environment, rendered in real time with interactive user control of the environment.
Humans are accustomed to seeing three dimensions. This is often referred to as stereopsis or stereoscopic vision. For simulated images, this is done in several ways. These include
The head-mounted display (HMD) was the first device that provided its wearer with an immersive experience.
The term fishtank VR refers to a system in which a stereo image of a 3-D scene is viewed on a monitor in perspective coupled with the head position and orientation of the user.
Larger display systems have been developed to display stereo images through the use of computer projection devices. Large screen areas are possible through the use of multiple projectors that can be edge-blended to create a seamless single large image. A CAVE consists of multiple screens and projectors configured into walls, floor, and ceiling to create a room.
In VR, real-time tracking is necessary to monitor the position and orientation of a user’s head and hands. Tracking systems are mechanical, optical, ultrasonic, magnetic, or inertial.
SUMMARY
This chapter introduces you to modern design practices. Graphics have been and will continue to be an important part of engineering design. Graphics, in all forms, are the communications medium of choice in the design process. The use of computers to create 3-D models is a critical part of the modern design process. These models are used to generate a database of information that can be shared with all of the members of the design team and used to develop and analyze the product. As has always been true, the engineer and technologist must know how to use all types of graphics and integrate them into the design process effectively to be successful in industry.
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