WHAT IS MANUFACTURING? Manufacturing is the process of converting raw materials into products. It encompasses the design and manufacturing of goods using various production methods and techniques. The word manufacturing is derived from the Latin manu factus, meaning made by hand. Modern manufacturing involves making products from raw materials by various processes, machinery, and operations, following a well-organized plan for each step.
Type of Course • Manufacturing is an integration course • It integrates your knowledge of: • Materials • Nature of materials • Mechanical properties • Flow properties • Stress strain behavior • Statics • Forces, torque's, pressures, vectors • Resolution of forces/vectors • Phase changes/crystal growth • Thermodynamics • Specific heat • Latent heat • Heat transfer • Fluid flow, statistics, control, etc
Examples of Knowledge Integration • Casting • Fluid flow • Heat Transfer • Phase changes • Crystal growth in pure metals and alloys • Rolling • Vector forces • Relationships among force, power and energy • Effect of deformation on crystal structure • Effect of temperature on microstructure (heat treating) • Machine dynamics
Why is traditional engineering so expensive? The typical cost for each change made during the development of a major product When changes are made Cost During Design $1,000 During Design Testing $10,000 During Process Planning $100,000 During Test Production $1,000,000 During Final Production $10,000,000
The basic goals of CE are: • to minimize product design and engineering changes. • to minimize time and cost involved in taking product from design concept to production and introduction of the product into the marketplace. Direct Engineering: • utilizes a database representing the engineering logic used in the design of each part of a product. If a design modification is made on a part, DE will determine the manufacturing consequences of that change. In order to implement CE it should be provided: • the full support of upper management • a multifunctional and interactive work team • utilization of all available technologies
Product design involves preparing analytical and physical models of the product as an aid to analyze factors such as: • forces • stresses • deflections • optimal part shape Computer-aided design, engineering, and manufacturing simplifies construction and analyses of analytical models. On the basis of these models, the product designer selects and specifies the final shape and dimensions of the product, its dimensional accuracy and surface finish, and the materials to be used.
A powerful and effective tool is COMPUTER SIMULATION in evaluating the performance of the product and planning the manufacturing system to produce it. Computer simulation helps in: • early detection of design flaws • identifying possible problems in a particular production system • optimizing manufacturing lines for minimum product cost Computer simulation predicting tool performance
Overview of the Manufacturing Processes The final shape of the manufactured component can be achieved by: • Changing the shape of the raw stock without adding material to it or taking material away from it. • Metal forming processes: Rolling, extrusion, forging, drawing, sheet metal forming • Obtaining the required shape by adding metal or joining two metallic parts together • Welding, brazing, metal deposition • Molding molten or particulate metal into a cavity that has the same shape as the final product • Casting, powder deposition • Removing portions from the stock material to obtain the final shape • turning, milling, drilling, etc.
Factors involved in the processes • Material Removal • Shear stress strain behavior • Vector forces • Relationships among force, power and energy and shearing energy • Machine dynamics • Thermodynamics and material expansion • Powder Processing for metals, ceramics and plastics • Surface science • Thermodynamics • Effect of heat on microstructure • Sintering • Flow and rheology of powders
Fundamentals of Manufacturing Concepts • The ability to create shapes, components and assembled products relies on several physical phenomena: • The liquid to solid phase transformation • Create the required shape in the liquid form then solidify • The ability of certain materials to flow under stresses greater than some limit • soften the material by heating it, then shape it • The ability of powders to flow like liquid and for powders to "sinter" and densify under heat and/or pressure • Useful for brittle materials • Additive methods • The method chosen depends on the material and the required properties.
Liquid to solid phase transformation • Create a negative mold of the same shape • Pour the liquid material in the mold • Solidify by • extracting heat or liquid (e.g. water) • reactions: heat induced, photon induced, or by reagents • Remove the solid part from the mold • Casting conditions determine the properties
Material Flow • Most metals and many plastics flow when stress exceeds the yield stress • The stress-strain curve has three regions: elastic, yield stress, and flow regime. • Flow regime - mechanical energy transformed into deformation and heat • Stress/strain conditions • Pure Compressive • die forging • Pure Tensile • drawing • Pure Shear • cutting, machining, turning
Combined Stress States • Rolling • Mostly compressive with some shear • Forging • Extremely complex stress states • Extrusion • Combination of high compressive and shear stresses • Bending • Mostly shear with tensile and compressive components • Stretching with bending • Mostly shear with only tensile components • Machining • Highly complex stress combination with high levels of shear causing fracture in a controlled manner
Powder Processing • Takes advantage of the ability of powders to flow like a liquid and fill complex shapes • can be dry or slurry • can be compacted by pressure or extraction of liquid from the slurry • this process forms a green body which is pliable and weak • heating to high temperatures causes the powder particles to sinter together for a strong, nearly 100% dense, product
Tolerances • impossible to obtain the desired nominal dimension when processing a workpiece • caused by • inaccuracies inherent in the machine tool • elastic deformation of the workpiece and/or fixture • temperature effects during processing • skill of the operator • establish a permissible degree of inaccuracy with respect to the nominal dimension that will not affect the proper functioning of the manufactured part • the nominal dimension is referred to as the the basic size of the part
the deviations from the basic size to each side determine the high and low limits • the difference between these two limits of size is called the tolerance • The International Standardization Organization (ISO) • the magnitude of the tolerance is dependent upon the basic size and is designated by an alphanumeric symbol called the grade • there are 18 standard grades of tolerance in the ISO system
Fits • the relationship between the dimensions of the mating surfaces must be specified • this determines the degree of tightness or freedom for relative motion between the mating surfaces • clearance fit: the upper limit of the shaft is always smaller than the lower limit of the mating hole • interference fit: the lower limit of the shaft is always larger than the upper limit of the hole • transition fit: is an intermediate fit
Interchangeability • means that identical parts must be able to replace each other without the need for any fitting operation • it is achieved by establishing a permissible tolerance, beyond which any further deviation from the nominal dimension of the part is not allowed • standardization limits the diversity and total number of varieties to a definite range of standard dimensions • e.g. For wires and sheets, the sheet thickness is limited to only 45 (in US standards)
The Production Turn • The main goal of a manufacturing project is to make a profit
Technology Development Cycle • A new technology emerges as a result of active R&D and is then employed in the design and manufacturing of several different products. • Technology is concerned with the industrial and everyday applications of the results of the theoretical and experimental studies that are referred to as engineering
Rapid Prototyping • Rapid prototyping relies on CAD/CAM and various manufacturing techniques to produce prototypes in the form of a solid physical model of a part rapidly and at low cost. • These techniques can be used for low-volume economical production of parts. • Tests on prototypes must be designed to simulate, as closely as possible, the conditions under which the product is to be used.
Computer-aided engineering techniques are now capable of comprehensively and rapidly performing such simulations. • After this phase has been completed, appropriate process plans, manufacturing methods, equipment, and tooling are selected with the cooperation of manufacturing engineers, process planner, and all others involved in production.
Design for Manufacturing, Assembly, Disassembly, and Service • Design for manufacturing (DFM) is a comprehensive approach to production of goods and integrates the design process with materials, manufacturing methods, process planning, assembly, testing, and quality assurance. • Designers should acquire a fundamental understanding of the characteristics, capabilities, and limitations of materials, manufacturing processes, and related operations, machinery, and equipment. • Expert system expedites the traditional iterative process in design optimization.
Properties of Materials • Mechanical Properties • strength • toughness • ductility • hardness • elasticity • fatigue • creep • Physical Properties • density • specific heat • conductivity • melting point • electric and magnetic properties
Chemical Properties: • oxidation • corrosion • general degredation • toxicity • flammability • Manufacturing properties of materials determine whether they can be cast, formed, shaped, machined, welded, or heat-treated with relative ease. • Another important consideration is that the methods used to process materials to the desired shapes ma adversely affect the product’s final properties, service life, and cost.
Cost and Availability: • The economic aspects of material selection are as important as the technological considerations of properties and characteristics of materials. • Appearance, Service Life, and Recycling: • color • feel • surface texture • time and service dependent phenomena such as wear, fatigue, creep, and dimensional stability are also important. • Compatibility of materials
Selecting Manufacturing Processes There is usually more than one method of manufacturing a part from a given material. • Casting: expandable mold and permanent mold • Forming and Shaping: rolling, extrusion, drawing, sheet forming, powder metallurgy, and molding. • Machining: turning, drilling, milling, planning, shaping, broaching, grinding, ultrasonic machining; chemical, electrical, and electrochemical machining; and high-energy beam machining. • Joining: welding, brazing, soldering, diffusion bonding, adhesive bonding, and mechanical joining. • Finishing Operations: honing, lapping, polishing, burnishing, deburring, surface treating, coating, and plating.
Dimensional and Surface Finish Consideration • Size, thickness, and shape complexity of the part have a major bearing on the process selected to produce it. • Flat parts with thin cross-sections cannot be cast properly. Complex parts cannot be formed easily and economically. • Tolerances and surface finish obtained in hot-working operations cannot be as fine as those obtained in cold-working operations. Dimensional changes, warpage, and surface oxidation occur during processing at elevated temperatures.
The size and shape of manufactured parts cary widely. • Nanotechnology and nanofabrication • Ultraprecision manufacturing techniques and machinery is coming into more common use. Highly sophisticated techniques such as molecular-beam epitaxy and scanning-tunneling engineering will be implemented to obtain accuracies on the order of the atomic lattice
Operational and Manufacturing Cost Considerations • the design and cost of tooling, the lead time required to begins production, and the effect of workpiece materials on tool and die life • availability of machines and equipment and operating experience • environmental and safety implications • the safe use of machinery
Net-shape Manufacturing The parts are made as close to the final desired dimensions, tolerances, and specifications as possible. Typical examples are: near-net shape forging and casting of parts, stamped sheet-metal parts, components made by powder metallurgy techniques, and injection molding of plastics.
Computer Integrated Manufacturing • The major goals of automation in manufacturing facilities are: • to integrate carious operations • to improve productivity • increase product quality and uniformity • minimize cycle times • reduce labor costs • Computers are used for: • optimization of manufacturing processes • material handling • assembly • automated inspection and testing of products.
Machine Control Systems • Numerical Control (NC) of machines is a method of controlling the movements of machine components by direct insertion of coded instructions in the form of numerical data. • In adaptive control (AC), process parameters are adjusted automatically to optimize production rate and product quality and minimize cost. Parameters such as forces, temperatures, surface finish, and dimensions of the part are monitored constantly.
Computer Technology • Computers allow us to integrate virtually all phases of manufacturing operations, which consist of various technical, as well as managerial, activities. • Computer-integrated Manufacturing (CIM) is characterized with: • responsiveness to rapid changes in market demand, product modification, and shorter product cycles • high quality products at low cost • better use of materials, machinery, and personnel, and reduced inventory • better control of production and management of the total manufacturing operation
Computer-aided Design (CAD) allows the designer to conceptualize objects more easily without having to make costly illustrations, models, or prototypes. • Computer-aided Engineering provides: • simulation, analyses, and testing of the performance of structures subjected to static or fluctuating loads and temperatures. • Computer-aided Manufacturing (CAM) involves all phases of manufacturing by utilizing and processing further the large amount of information on materials and processes collected and stored in the organization’s database. • Some of the tasks are: programming numerical control of machines; programming robots for material handling; designing tools, dies, and fixtures; and maintaining quality control.
Computer-aided Process Planning (CAPP) is capable of improving productivity in a plant by optimizing process plans, reducing planning costs, and improving the consistence of product quality and reliability. Functions such as cost estimating and time required to perform a certain operation can also be incorporated into the system. • Group Technology and Cellular Manufacturing (CM) • The concept of group manufacturing is that parts can be grouped and produced by classifying them according to similarities in design and manufacturing processes. In this way, part design and process plans can be standardized, and families of parts can be produced efficiently and economically.
Quality Assurance and Total Quality Management • Traditionally, quality assurance has been obtained by inspecting parts after they have been manufactured. • Quality must be built into a product from the design stage through all subsequent stages of manufacture and assembly. • We control processes, not products. • Product integrity is a term that can be used to define the degree to which a product • is suitable for its intended purpose • fills a real market need • functions reliably during it’s life expectancy • can be maintained with relative ease.
Total quality management (TQM) • becomes the responsibility of everyone involved in designing and manufacturing a product • prevents defects from occurring rather than detecting defective products • Important developments in quality assurance include the implementation of design of experiment, a technique in which the factors involved in a manufacturing process and their interactions are studied simultaneously. • ISO 9000 series on quality management and quality assurance standards • this is a quality process certification, not a product certification • It is becoming the world standard for quality
Global Competitiveness and Manufacturing Costs • Typically, manufacturing costs represent about 40% of a product’s selling price • design principles for economic production are: • the design should be as simple as possible to manufacture, assemble, disassemble, and recycle • materials should be chosen for their appropriate manufacturing characteristics • dimensional accuracy and surface finish specified should be as broad as permissible • because they can add significantly to cost, secondary and finishing processes should be avoided or minimized • The total cost of manufacturing a product consists of: • materials • tooling • labor • fixed and capital costs
Environmental Concerns • Discarded per year in the US: • 9 million passenger cars • 285 million tires • more than 5 billion kilograms of plastic products • metalworking fluids (lubricants, coolants, solvents, etc.) • by-products: sand with additives for casting; water, oild, and other fluids from heat-treating facilities and plating operations; slag from foundries and welding operations; scrap of all kinds • 800,000 metric tons of old TV sets, radios, and computer equipment are discarded in Germany each year.
Certain guidelines can be followed: • reducing waste of materials at their source by refinements in product design and reducing the amount of materials used • conducting research and development of manufacturing technologies • reducing the use of hazardous materials in products and processes • ensuring proper handling and disposal of all waste • making improvements in recycling, waste treatment, and reuse of materials • Design for the environment • Design for recycling