study unit manufacturing processes, part 3f01. 4 manufacturing processes, part 3 types of processes
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Manufacturing Processes, Part 3 By
In this unit we’ll focus on the actual manufacturing tech- niques and processes used to make parts and assemblies from raw materials to finished products. The choice of materials, the processes used, the performance goals, and the aesthetic goals all are significant factors in the product design process, which starts with the development of a performance specification, or “spec.” The spec can be firm, complete with dimensions, weights, performance limits, and costs; or it can be a simple goal of providing a product to meet a need identified by marketing surveys, with minimum performance goals and some desirable features. The product design process is a continuous analysis. It consists of evalu- ating possible combinations of material selection, process selection, design for processing, part count analysis, design for ease of assembly, assembly costs, and part costs. The goal is to produce the product efficiently for the highest pos- sible value at the lowest possible cost. Very often, advances in materials will make changes in processes and assembly methods desirable, to lower the finished product’s cost or raise its performance level.
When you complete this study unit, you’ll be able to
• Identify and describe the general classifications of manufacturing systems that provide us with product
• Identify important processes used to manufacture parts from different materials, and select appropriate techniques to produce finished parts
• Understand and describe the fundamental cutting and forming processes used to make products or parts
• Understand and describe the basic technical aspects of new manufacturing processes for high-tech applications
• List the advantages and disadvantages of manufacturing methods used to process various materials and understand why each of these processes may be used in different applications
• Identify and describe the most important methods of joining components or subassemblies to make completed parts
• Understand and select appropriate finishing methods for manufactured parts
• Understand and describe the basic manufacturing systems used to assemble parts into finished products
DEFINITIONS AND CLASSIFICATIONS 1
Primary and Secondary Processes 1 Discrete and Continuous Processes 2 Types of Processes 4
MANUFACTURING PROCESSES 8
Casting and Molding 10 Plastic Processes 21
FORMING PROCESSES 29
Forging 31 Rolling 35 Spinning 38 Extrusion 39 Drawing 41 Powder Metallurgy Processes 41
MATERIAL REMOVAL PROCESSES 45
Introduction to Cutting Processes 46 Conventional Machining Processes 54 Unconventional Machining Processes 67 Process Comparisons 75
JOINING PROCESSES 78
Welding 79 Brazing and Soldering 88 Adhesive Bonding 92 Mechanical Fastening 93 Additional Processes 96 Assembly Processes 102
SELF-CHECK ANSWERS 111
DEFINITIONS AND CLASSIFICATIONS
Primary and Secondary Processes
Primary manufacturing processes are those that produce materials used to make other parts or products. For example, a steel mill is a place where the raw materials of iron ore, coke, limestone, and alloying ingredients are gathered and put through a primary process that results in steel ingots. These in turn are reheated and processed into shapes such as billets, rods, bars, tubing, and plate. These manufactured products serve as the raw material for other manufacturing processes that turn them into auto parts, golf clubs, or machine tools. Primary manufacturing industries generally use naturally occurring raw materials as input to their processes, and include such diverse industries as farming, mining, and wood processing.
Another example of primary manufacturing is the production of plastics from petroleum. These materials contain organic (carbon-based) molecules that are polymerized to form long chains of monomers linked together. As you know, thermo- plastic materials can be melted and molded into various shapes. The raw material for these processes often is shipped from the primary manufacturer in the form of containers of small plastic pellets.
Manufacturing Processes, Part 3
Manufacturing Processes, Part 32
An important primary manufacturing business is the produc- tion and fabrication of building materials such as framing lumber and sheathing materials including oriented-strand board and plywood. Producing these wood products involves harvesting suitable trees, debarking and sawing them into shapes, drying the boards in ovens until they have a specific moisture content, and sawing and planing them into the finished shape, such as the common 2 � 4. These in turn are used in other manufacturing processes such as the construction of houses, garages, and items such as tables or furniture.
Secondary manufacturing processes are those that take the output of a primary process and make it into finished parts or products. Common examples of secondary manufac- turers would be modular home manufacturers (who build residential houses), appliance manufacturers (stoves and dishwashers), toy manufacturers (children’s plastic figurines), or auto manufacturers (cars and trucks). All these industries use raw materials that were prepared for their use by a primary manufacturer, which processed naturally occurring raw materials into usable forms.
Discrete and Continuous Processes
Manufacturing processes can be further classified as discrete or continuous. Discrete manufacturing processes are those that make individual parts or assemblies. They may be pro- duced by the thousands every hour, 24 hours a day, but the method always produces individual parts. Continuous manufacturing, on the other hand, produces a continuous flow of product. Common examples include manufacturing wire or cable, and chemical processes such as petroleum refining.
Aluminum wire for electrical installations is produced in a continuous process that starts with large individual billets of aluminum. These billets are heated and rolled into increasingly smaller shapes until they can be drawn through dies and made into wire. The wire in turn is drawn through a series of dies until the desired diameter is achieved. When the material available from one billet has been completely processed,
Manufacturing Processes, Part 3 3
another section of wire is welded onto the end of the preceding one, making a continuous length of wire as long as desired. The wire “flows” through the factory as a never-ending piece. As it moves through the transport machines, it’s heat-treated and processed into its final form. Many applications call for metal cable, which is produced from smaller strands of wire that are twisted together in winding machines. Often plastic insulation material is applied before the cable is wound onto a large reel and prepared for shipment.
Wire rope is made in a similar fashion from many strands of smaller steel wires that are twisted together into larger cables; these larger cables are twisted together to make even larger ones. Wire rope is a key feature of suspension bridges and elevators.
Many types of chemical manufacturing are also continuous processes. For example, crude oil is refined into gasoline and other products in a process called fractional distillation. As the crude is heated, various components, called fractions, vaporize at successively higher temperatures based on their molecular weight. Gasoline has a low molecular weight, so it vaporizes at a temperature just below the boiling point of water, while the other components are still liquid. Further increases in temperature allow the distillation and recovery of other products such as diesel fuel and kerosene, waxes, lubricants, greases, and even asphalt.
Modern refining processes produce about 21 gallons of gaso- line from every barrel of oil (42 gallons), while also producing about 3 gallons of jet fuel, 9 gallons of oil and distillates, a little less than 4 gallons of lubricants, and about 3 gallons of heavier residues (Figure 1). Catalytic processes allow the pro- duction of other types of chemicals, generally classified as petrochemicals, from which we derive primary materials such as alcohols, detergents, synthetic rubber, glycerin, fertilizers, solvents, and the raw materials for the manufacture of drugs, plastics and polymers, paints, polyesters, explosives, dyes, and insulating materials. The petrochemical industry con- sumes about 5 percent of the total supply of oil and gas in the United States.
Manufacturing Processes, Part 34
Types of Processes
Manufacturing businesses supply almost all the durable and nondurable goods we use every day. Durable goods like appliances, automobiles, and airplanes are meant to last a long time. Nondurable goods are those consumed quickly, such as paper, food, clothing, and calculators. Subsets of these very broad classifications of manufactured products include several major industries that have large impacts on our economy. Changes in the conditions, resources, methods, or markets in these industries will have major effects on our lives and jobs. These are
• Iron and steel manufacturing—the production of steel material such as rod, plate, billets, bar, and beams used in many other manufacturing industries. Iron an