CHAPTER 2 MECHANICAL DESIGN

CHAPTER 2MECHANICAL DESIGN

Outline the major steps involved in a mechanical design process.Recognize the importance of mechanical design for solving the technical, global, and environmental challenges that society faces.Recognize the importance of innovation in designing effective engineered products, systems, and processes.Recognize the importance of multidisciplinary teams, collaboration, and technical communication in engineering.Be familiar with some of the processes and machine tools used in manufacturing.Understand how patents are used to protect a newly developed technology in the business side of engineering.Describe the role played by computer-aided engineering tools in linking mechanical design, analysis, and manufacturing.

GADGET PRODUCT DEVELOPMENT

RENEWABLE ENERGY PRODUCT DEVELOPMENT

Make solar energy economical Provide energy from fusion Develop carbon sequestration methods Manage the nitrogen cycle Provide access to clean water Restore and improve urban infrastructure Advance health informatics Engineer better medicines Reverse-engineer the brain Prevent nuclear terror Secure cyberspace Enhance virtual reality Advance personalized learning Engineer the tools of scientific discoveryThe National Academy of Engineering (NAE) has identified 14 Grand Challenges facing the global engineering community and profession in the twenty-first century.

Requirements DevelopmentEngineering design begins when a basic need has been identified. This could be a technical need from a certain market or a basic human need like clean water, renewable energy, or protection from natural disasters. Initially, a design engineer develops a comprehensive set of system requirements considering the following issues:

Functional performance: What the product must accomplishEnvironmental impact: During production, use, and retirementManufacturing: Resource and material limitationsEconomic issues: Budget, cost, price, profitErgonomic concerns: Human factors, aesthetics, ease of useGlobal issues: International markets, needs, and opportunitiesLife cycle issues: Use, maintenance, planned obsolescenceSocial factors: Civic, urban, cultural issues

Requirements DevelopmentThe design team develops the following set of system requirements. These requirements state what the system must do, not how. Determining how starts in the conceptual design stage.Affordable ReliableEfficientAesthetically attractive/unobtrusiveMinimize noise levelsSimple to installAdaptableEasy to maintainSafe to useEasy to manufacture

In this stage, design engineers collaboratively and creatively generate a wide range of potential solutions to the problem at hand and then select the most promising one(s) to develop.

Conceptual Design

At this point in the design process, the team has defined, innovated, analyzed, and converged its way to the best concept. However, many design and manufacturing details remain open, and each must be resolved before the product hardware can be produced. In the detailed design of the product, a number of issues must be determined:Detailed DesignDeveloping product layout and configurationSelecting materials for each componentAddressing design-for-X issues (e.g., design for reliability, manufacturing, assembly, variation, costing, recycling)Optimizing the final geometry, including appropriate tolerancesDeveloping completed digital models of all components and assembliesSimulating the system using digital and mathematical modelsPrototyping and testing critical components and modulesDeveloping the production plans

SimplicityIterationUsabilityDocumentationPatentsDesign patentUtility patent

Detailed Design

Rapid Prototyping

MANUFACTURING PROCESSESThe main classes of manufacturing processes are as follows:Casting is the process whereby liquid metal, such as gray iron, aluminum, or bronze, is poured into a mold, cooled, and solidified.Forming encompasses a family of techniques whereby a raw material is shaped by stretching, bending, or compression. Large forces are applied to plastically deform a material into its new permanent shape.Machining refers to processes where a sharp metal tool removes material by cutting it. The most common machining methods are drilling, sawing, milling, and turning. Joining operations are used to assemble subcomponents into a final product by welding, soldering, riveting, bolting, or adhesively bonding them. Many bicycle frames, for instance, are welded together from individual pieces of metal tubing.Finishing steps are taken to treat a components surface to make it harder, improve its appearance, or protect it from the environment. Some processes include polishing, electroplating, anodizing, and painting.

Examples of hardware produced by casting:a disk-brake rotor, automotive-oil pump, piston, bearing mount, V-belt sheave, model-airplane engine block, and a two-stroke engine cylinder

Examples of hardware produced by forging

Examples of aluminum extrusions

This body for a hydraulic valve assembly was first cast from aluminum (left) and then machined in order to produce holes, flatten surfaces, and cut threads (right)

(a) Major components of a drill press

(b) Different types of holes that can be produced

Mini wind turbines placed on roofs of buildingsSidewalks that produce energy when walked onMini turbines in toilets that generate energy when flushedBatteries using new high-kappa materialsHybrid cars that charge the grid when not in useA large array of roof-mounted solar panels across the cityWind turbines located near a cityA power plant using a Rankine cycle with rocket-derived combustionA plasma-arc gasification plant to burn garbage to produce powerIncreasing the number and efficiency of traditional steam power plantsDeveloping a series of hydroelectric damsGeothermal plants that exploit in-ground temperature differencesGenerating power from humans using a Matrix style farmDeveloping a fusion reactorOrganic Rankine cycle to recover heat from lower-temperature sourcesUsing algae as a biofuelDeveloping a revolving door generator for use in large commercial buildingsPhotovoltaic steel to generate energyPhotovoltaic paint to generate power on all buildingsGenerating power in gyms (treadmills, bicycles, elliptical machines)Using running animals to generate powerFood recycle science system to capture methanePower Infrastructure Alleviation Concepts