Ceramics and polymers have covalent and ionic bonding, in which the electrons are tightly bound to particular molecules. Dielectric strength is defined as the electrical potential required to break down the insulator per unit thickness. An electrolyte is an ionized solution capable of conducting electric current by movement of the ions. In these cases, which of the following temperatures marks the beginning of melting: a liquidus or b solidus? The high thermal conductivity of copper makes it difficult to weld because the heat flows away from the joint rather than being concentrated to permit melting of the metal.
This is perhaps a tricky question. Choices a and b are included in Eq. Temperature f has a strong influence on the diffusion coefficient. Time g figures into the process because it affects the concentration gradient; as time elapses, the concentration gradient is reduced so that the rate of diffusion is reduced.
This shaft is to be inserted into a hole in an expansion fit assembly operation. To be readily inserted, the shaft must be reduced in diameter by cooling. Refer to Table 4. Revise Eq. Expansion joints are provided to compensate for the change in length in the support girders as the temperature fluctuates.
Each expansion joint can compensate for a maximum of 40 mm of change in length. What is the minimum number of expansion joints required? Therefore, a minimum of 11 joints are needed for coverage of the total length. Solution: Assume a 1 cm3 cube, 1 cm on each side. From Table 4. Conversion: 1. Use Table 4. How does this affect the resistance? Since nickel is a metal, the resistivity would increase, causing the resistance to increase. This, in turn, would cause slightly more heat to be generated. Aluminum wire that was 12 gauge a measure of cross-sectional area was rated at 15 A of current.
If copper wire of the same gauge were used to replace the aluminum wire, what current should the wire be capable of carrying if all factors except resistivity are considered equal? Assume that the resistance of the wire is the primary factor that determines the current it can carry and the cross- sectional area and length are the same for the aluminum and copper wires.
Solution: The area and length are constant between the types of wires. The overall change in resistance is due to the change in resistivity of the materials. A tolerance is defined as the total amount by which a specified dimension is permitted to vary. A bilateral tolerance allows variation in both positive and negative directions from the nominal dimension, whereas a unilateral tolerance allows the variation from the nominal dimension to be either positive or negative, but not both.
Accuracy is the degree to which the measured value agrees with the true value of the quantity of interest. It is a measurement procedure that is absent of systematic errors. Precision in measurement is the degree to which random errors are minimized. A graduated measuring device has markings called graduations on a linear or angular scale to measure an object's feature of interest e. The reasons why surfaces are important include: aesthetics, safety, friction and wear, effect of surface on mechanical and physical properties, mating of components in assembly, and electrical contacts.
The nominal surface is the ideal part surface represented on an engineering drawing. It is assumed perfectly smooth; perfectly flat if referring to a planar surface; perfectly round if referring to a round surface, etc. Surface texture is the random and repetitive deviations from the nominal surface, including roughness, waviness, lay, and flaws.
Surface texture refers only to the surface geometry; surface integrity includes not only surface but the subsurface layer beneath the surface and the changes in it. Roughness consists of the finely-spaced deviations from the nominal surface, while waviness refers to the deviations of larger spacing. Roughness deviations lie within waviness deviations.
Surface roughness is defined as the average value of the vertical deviations from the nominal surface over a specified surface length. Surface roughness provides only a single measure of surface texture. Among its limitations are: 1 it varies depending on direction; 2 it does not indicate lay; 3 its value depends on the roughness width cutoff used to measure the average. The changes and injuries include: cracks, craters, variations in hardness near the surface, metallurgical changes resulting from heat, residual stresses, intergranular attack, etc.
Energy input to the surface resulting from the manufacturing process used to generate the surface. The energy forms can be any of several types, including mechanical, thermal, chemical, and electrical. Common methods for assessing surface roughness are 1 comparison of the specimen surface with standard test blocks having known surface roughness values and 2 stylus-type electronic instruments which measure average roughness.
Processes that produce poor surfaces include sand casting, hot rolling, sawing, and thermal cutting e. Processes that produced very good and excellent surfaces include honing, lapping, polishing, and superfinishing. Answer: The markings are slightly closer. The 50 markings on the vernier plate fit in place of 49 markings on the stationary bar. Answer: The object is inserted between the jaws. The distance between the zero on the stationary bar and the zero on the vernier plate moveable scale is added to the number that corresponds to the line that exactly lines up on the vernier plate.
Only one mark on the veriner plate will line up with a mark on the stationary bar. Answer: The thread pitch determines the linear motion of the micrometer for each rotation of the barrel. A metric micrometer will use a different pitch than an English micrometer. Multiple Choice Quiz There are 19 correct answers in the following multiple choice questions some questions have multiple answers that are correct. Each Also, sawing e will yield a poor finish. Either answer is acceptable.
There is a wear allowance applied only to the GO side of the gage. Solution: a The tolerance band is 0. As the gage wears, the dimension will decrease and allow unacceptable parts, so the wear allowance is added to it. No wear allowance is added because this gage should not fit in the hole and wear away. As the gage wears, the dimension will increase allowing unacceptable parts, so the wear allowance is subtracted from it. The length of the sine bar is 6. The rolls have a diameter of 1.
All inspection is performed on a surface plate. In order for the sine bar to match the angle of the part, the following gage blocks must be stacked: 2. Determine the angle of the part feature. The angle has a dimension of The sine bar rolls have a diameter of A set of gage blocks is available that can form any height from Determine a the height of the gage block stack to inspect the minimum angle, b height of the gage block stack to inspect the maximum angle, and c smallest increment of angle that can be setup at the nominal angle size. Typical metallic properties include: high strength and stiffness, good electrical and thermal conductivity, and higher density than ceramics or polymers.
Define them. Ferrous metals, which are based on iron; and nonferrous, which includes all others. An alloy is a metal comprised of two or more elements, at least one of which is metallic. A solid solution is an alloy in which one of the metallic elements is dissolved in another to form a single phase. A substitutional solid solution is where the atoms of the dissolved element replace atoms of the solution element in the lattice structure of the metal.
An interstitial solid solution is where the dissolved atoms are small and fit into the vacant spaces the interstices in the lattice structure of the solvent metal. An intermediate phase is an alloy formed when the solubility limit of the base metal in the mixture is exceeded and a new phase, such as a metallic compound e.
Why is it so simple? The Cu-Ni alloy system is simple because it is a solid solution alloy throughout its entire composition range. The carbon content ranges from 0. The carbon content ranges from 2. All of the alloying elements other than C strengthen the steel by solid solution alloying. Cr, Mn, Mo, and Ni increase hardenability during heat treatment. Cr and Mo improve hot hardness. Several of the alloying elements Cr, Mo, V form hard carbides with C, which increases wear resistance.
Vanadium inhibits grain growth during heat treatment which improves strength and toughness. It is called austenitic because this alloy exists in its austenitic phase at room temperature. The reason is that nickel has the effect of enlarging the austenitic temperature range to include room temperature. Aluminum is noted for its low density, high electrical and thermal conductivity, formability, good corrosion resistance due to the formation of a tough oxide film on its surface, and ability to be alloyed and strengthened to achieve good strength-to-weight ratios.
Magnesium is noted for its very low density lightest of the structural metals , propensity to oxidize which can cause problems in processing , and low strength; however, it can be alloyed and strengthened by methods similar to those used for aluminum alloys to achieve respectable strength-to-weight ratios. Its high electrical conductivity low resistivity. The elements are a tin and b zinc, respectivley.
The important applications of Ni are 1 as an alloying ingredient in steel, e. Titanium is noted for its high strength-to-weight ratio, corrosion resistance due to the formation of a thin but tough oxide film , and high temperature strength. The important applications of Zn are 1 die castings - zinc is an easy metal to cast; 2 as a coating in galvanized steel; 3 as an alloying element with copper to form brass. Mo and W are the most important.
Name the three groups. The three groups are 1 iron-based alloys, 2 nickel-based alloys, and 3 cobalt-based alloys. What distinguishes them from other alloys? Primary industries cultivate and exploit natural resources, such as agriculture and mining.
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Secondary industries take the outputs of the primary industries and convert them into consumer and capital goods. Manufacturing is the principal activity in this category, but construction and power utilities are also included. Tertiary industries constitute the service sector of the economy. A list of specific industries in these categories is presented in Table 1. This book is concerned with the secondary industries in Table 1. In this book, manufacturing means production of hardware, which ranges from nuts and bolts to digital computers and military weapons.
Plastic and ceramic. Section 1. TABLE 1. Manufactured Products Final products made by the manufacturing industries can be divided into two major classes: consumer goods and capital goods. Consumer goods are products purchased directly by consumers, such as cars, personal computers, TVs, tires, and tennis rackets. Examples of capital goods include aircraft, computers, communication equipment, medical apparatus, trucks and buses, railroad locomotives, machine tools, and construction equipment. Most of these capital goods are purchased by the service industries.
Yet the manufactured capital goods purchased by the service sector are the enablers of that sector. Without the capital goods, the service industries could not function. In addition to final products, other manufactured items include the materials, components, and supplies used by the companies that make the final products. Examples of these items include sheet steel, bar stock, metal stampings, machined parts, plastic moldings and extrusions, cutting tools, dies, molds, and lubricants. Thus, the manufacturing industries consist of a complex infrastructure with various categories and layers of intermediate suppliers with whom the final consumer never deals.
This book is generally concerned with discrete itemsindividual parts and assembled products, rather than items produced by continuous processes. A metal stamping is a discrete item, but the sheet-metal coil from which it is made is continuous almost. Many discrete parts start out as continuous or semicontinuous products, such as extrusions and electrical wire. Long sections made in almost continuous lengths are cut to the desired size.
An oil refinery is a better example of a continuous process. Production Quantity and Product Variety The quantity of products made by a factory has an important influence on the way its people, facilities, and procedures are organized. Annual production quantities can be classified into three ranges: 1 low production, quantities in the range 1 to units per year; 2 medium production, from to 10, units annually; and 3 high production, 10, to millions of units.
The boundaries. Depending on the kinds of products, these boundaries may shift by an order of magnitude or so. Production quantity refers to the number of units produced annually of a particular product type. Some plants produce a variety of different product types, each type being made in low or medium quantities. Other plants specialize in high production of only one product type. It is instructive to identify product variety as a parameter distinct from production quantity. Product variety refers to different product designs or types that are produced in the plant.
Different products have different shapes and sizes; they perform different functions; they are intended for different markets; some have more components than others; and so forth. The number of different product types made each year can be counted. When the number of product types made in the factory is high, this indicates high product variety. There is an inverse correlation between product variety and production quantity in terms of factory operations.
If a factorys product variety is high, then its production quantity is likely to be low; but if production quantity is high, then product variety will be low, as depicted in Figure 1. Manufacturing plants tend to specialize in a combination of production quantity and product variety that lies somewhere inside the diagonal band in Figure 1.
Although product variety has been identified as a quantitative parameter the number of different product types made by the plant or company , this parameter is much less exact than production quantity, because details on how much the designs differ are not captured simply by the number of different designs.
Differences between an automobile and an air conditioner are far greater than between an air conditioner and a heat pump. Within each product type, there are differences among specific models. The extent of the product differences may be small or great, as illustrated in the automotive industry. Each of the U. In different plants, the company builds heavy trucks. The terms soft and hard might be used to describe these differences in product variety.
Soft product variety occurs when there are only small differences among products, such as the differences among car models made on the same production line. In an assembled product, soft variety is characterized by a high proportion of common parts among the models. Hard product variety occurs when the products differ substantially, and there are few common parts, if any. The difference between a car and a truck exemplifies hard variety. These three building blocksmaterials, processes, and systemsconstitute the. There is a strong interdependence among these factors. A company engaged in manufacturing cannot do everything.
It must do only certain things, and it must do those things well. Manufacturing capability refers to the technical and physical limitations of a manufacturing firm and each of its plants. Several dimensions of this capability can be identified: 1 technological processing capability, 2 physical size and weight of product, and 3 production capacity.
Technological Processing Capability The technological processing capability of a plant or company is its available set of manufacturing processes. Certain plants perform machining operations, others roll steel billets into sheet stock, and others build automobiles.
A machine shop cannot roll steel, and a rolling mill cannot build cars. The underlying feature that distinguishes these plants is the processes they can perform. Technological processing capability is closely related to material type. Certain manufacturing processes are suited to certain materials, whereas other processes are suited to other materials.
By specializing in a certain process or group of processes, the plant is simultaneously specializing in certain material types. Technological processing capability includes not only the physical processes, but also the expertise possessed by plant personnel in these processing technologies. Companies must concentrate on the design and manufacture of products that are compatible with their technological processing capability. Physical Product Limitations A second aspect of manufacturing capability is imposed by the physical product.
A plant with a given set of processes is limited in terms of the size and weight of the products that can be accommodated. Large, heavy products are difficult to move. To move these products about, the plant must be equipped with cranes of the required load capacity. Smaller parts and products made in large quantities can be moved by conveyor or other means. The limitation on product size and weight extends to the physical capacity of the manufacturing equipment as well.
Production machines come in different sizes. Larger machines must be used to process larger parts. The production and material handling equipment must be planned for products that lie within a certain size and weight range. Production Capacity A third limitation on a plants manufacturing capability is the production quantity that can be produced in a given time period e. This quantity limitation is commonly called plant capacity, or production capacity, defined as the maximum rate of production that a plant can achieve under assumed operating conditions.
The operating conditions refer to number of shifts per week, hours per shift, direct labor manning levels in the plant, and so on. These factors represent inputs to the manufacturing plant. Given these inputs, how much output can the factory produce? Plant capacity is usually measured in terms of output units, such as annual tons of steel produced by a steel mill, or number of cars produced by a final assembly plant. In these cases, the outputs are homogeneous. In cases in which the output units are not homogeneous, other factors may be more appropriate measures, such as available labor hours of productive capacity in a machine shop that produces a variety of parts.
Materials, processes, and systems are the basic building blocks of manufacturing and the three broad subject areas of this book. This introductory chapter provides an overview of these three subjects before embarking on detailed coverage in the remaining chapters. Their chemistries are different, their mechanical and physical properties are different, and these differences affect the manufacturing processes that can be used to produce products from them. In addition to the three basic categories, there are.
The classification of the four groups is pictured in Figure 1. This section surveys these materials. Chapters 6 through 9 cover the four material types in more detail. Metals and alloys can be divided into two basic groups: 1 ferrous and 2 nonferrous. Ferrous Metals Ferrous metals are based on iron; the group includes steel and cast iron. These metals constitute the most important group commercially, more than three fourths of the metal tonnage throughout the world.
Pure iron has limited commercial use, but when alloyed with carbon, iron has more uses and greater commercial value than any other metal. Alloys of iron and carbon form steel and cast iron. Steel can be defined as an ironcarbon alloy containing 0. It is the most important category within the ferrous metal group. Its composition often includes other alloying elements as well, such as manganese, chromium, nickel,and molybdenum, to enhance the properties of the metal. Applications of steel include construction bridges, I-beams, and.
Silicon is also present in the alloy in amounts from 0. Cast iron is available in several different forms, of which gray cast iron is the most common; its applications include blocks and heads for internal combustion engines. Nonferrous Metals Nonferrous metals include the other metallic elements and their alloys. In almost all cases, the alloys are more important commercially than the pure metals. The nonferrous metals include the pure metals and alloys of aluminum, copper, gold, magnesium, nickel, silver, tin, titanium, zinc, and other metals.
Typical nonmetallic elements are oxygen, nitrogen, and carbon. Ceramics include a variety of traditional and modern materials. Traditional ceramics, some of which have been used for thousands of years, include: clay abundantly available, consisting of fine particles of hydrous aluminum silicates and other minerals used in making brick, tile, and pottery ; silica the basis for nearly all glass products ; and alumina and silicon carbide two abrasive materials used in grinding.
Modern ceramics include some of the preceding materials, such as alumina, whose properties are enhanced in various ways through modern processing methods. Newer ceramics include: carbidesmetal carbides such as tungsten carbide and titanium carbide, which are widely used as cutting tool materials; and nitridesmetal and semimetal nitrides such as titanium nitride and boron nitride, used as cutting tools and grinding abrasives.
For processing purposes, ceramics can be divided into crystalline ceramics and glasses. Different methods of manufacturing are required for the two types. Crystalline ceramics are formed in various ways from powders and then fired heated to a temperature below the melting point to achieve bonding between the powders. The glass ceramics namely, glass can be melted and cast, and then formed in processes such as traditional glass blowing.
Polymers usually consist of carbon plus one or more other elements, such as hydrogen, nitrogen, oxygen, and chlorine. Polymers are divided into three categories: 1 thermoplastic polymers, 2 thermosetting polymers, and 3 elastomers. Thermoplasticpolymers can besubjected tomultipleheatingand coolingcycles without substantially altering the molecular structure of the polymer. Common thermoplastics include polyethylene, polystyrene, polyvinylchloride, and nylon.
Thermosetting polymers chemically transform cure into a rigid structure on cooling from a heated plastic condition; hence the name thermosetting. Members of this type include phenolics, amino resins, and epoxies. Although the name thermosetting is used, some of these polymers cure by mechanisms other than heating. Elastomers are polymers that exhibit significant elastic behavior; hence the name elastomer. They include natural rubber, neoprene, silicone, and polyurethane. A composite is a material consisting of two or more phases that are. The term phase refers to a homogeneous mass of material, such as an aggregation of grains of identical unit cell structure in a solid metal.
The usual structure of a composite consists of particles or fibers of one phase mixed in a second phase, called the matrix. Composites are found in nature e. The synthesized type is of greater interest here, and it includes glass fibers in a polymer matrix, such as fiber-reinforced plastic; polymer fibers of one type in a matrix of a second polymer, such as an epoxy-Kevlar composite; and ceramic in a metal matrix, such as a tungsten carbide in a cobalt binder to form a cemented carbide cutting tool.
Properties of a composite depend on its components, the physical shapes of the components, and the way they are combined to form the final material. Some composites combine high strength with light weight and are suited to applications such as aircraft components, car bodies, boat hulls, tennis rackets, and fishing rods. Other composites are strong, hard, and capable of maintaining these properties at elevated temperatures, for example, cemented carbide cutting tools.
A manufacturing process is usually carried out as a unit operation , which means that it is a single step in the sequence of steps required to transform the starting material into a final product. Manufacturing operations can be divided into two basic types: 1 processing operations and 2 assembly operations.
A processing operation transforms a work material from one state of completion to a more advanced state that is closer to the final desired product. It adds value by changing the geometry, properties, or appearance of the starting material. In general, processing operations are performed on discrete workparts, but certain processing operations are also applicable to assembled items e. An assembly operation joins two or more components to create a new entity, called an assembly, subassembly, or some other term that refers to the joining process e.
A classification of manufacturing processes is presented in Figure 1. Many of the manufacturing processes covered in this text can be viewed on the DVD that comes with this book. Alerts are provided on these video clips throughout the text. Some of the basic processes used in modern manufacturing date from antiquity Historical Note 1. The forms of energy include mechanical, thermal, electrical, and chemical. The energy is applied in a controlled way by means of machinery and tooling.
Human energy may also be required, but the human workers are generally employed to control the machines, oversee the operations, and load and unload parts before and after each cycle of operation. A general model of a processing operation is illustrated in Figure 1. Material is fed into the process, energy is applied by the machinery and tooling to transform the material, and the completed workpart exits the process. Most production operations produce waste or scrap, either as a natural aspect of the process e.
It is an important objective in manufacturing to reduce waste in either of these forms. It was during this period that processes such as the following were developed: carving and other woodworking, hand forming and ring of clay pottery, grinding and polishing of stone, spinning and weaving of textiles, and dyeing of cloth. Metallurgy and metalworking also began during the Neolithic period, in Mesopotamia and other areas around the Mediterranean.
It either spread to, or developed independently in, regions of Europe and Asia. Gold was found by early humans in relatively pure form in nature; it could be hammered into shape. Copper was probably the rst metal to be extracted from ores, thus requiring smelting as a processing technique. Copper could not be hammered readily because it strain hardened; instead, it was shaped by casting Historical. Note Other metals used during this period were silver and tin.
It was discovered that copper alloyed with tin produced a more workable metal than copper alone casting and hammering could both be used. Iron was also rst smelted during the Bronze Age. Meteorites may have been one source of the metal, but iron ore was also mined. Temperatures required to reduce iron ore to metal are signicantly higher than for copper, which made furnace operations more difcult.
Other processing methods were also more difcult for the same reason. Early blacksmiths learned that when certain irons those containing small amounts of carbon were sufciently heated and then quenched, they became very hard. This permitted grinding a very sharp cutting edge on knives and weapons, but it also made the metal brittle. Toughness could be increased by reheating at a lower temperature, a process known as tempering. What we have described is, of course, the heat treatment of steel. The superior properties of steel caused it to succeed bronze in many applications weaponry, agriculture, and mechanical devices.
It was not until much later, well into the nineteenth century, that the demand for steel grew signicantly and more modern steelmaking techniques were developed Historical Note 6. The beginnings of machine tool technology occurred during the Industrial Revolution. During the period , machine tools were developed for most of the conventional material removal processes, such as boring, turning, drilling, milling, shaping, and planing Historical Note Many of the individual processes predate the machine tools by centuries; for example, drilling and sawing of wood date from ancient times, and turning of wood from around the time of Christ.
Assembly methods were used in ancient cultures to make ships, weapons, tools, farm implements, machinery, chariots and carts, furniture, and garments. The earliest processes included binding with twine and rope, riveting and nailing, and soldering. Around years ago, forge welding and adhesive bonding were developed. Widespread use of screws, bolts, and nuts as. It was not until around that fusion welding processes started to be developed as assembly techniques Historical Note Natural rubber was the rst polymer to be used in manufacturing if we overlook wood, which is a polymer composite.
The vulcanization process, discovered by Charles Goodyear in , made rubber a useful engineering material Historical Note 8. Subsequent developments included plastics such as cellulose nitrate in , Bakelite in , polyvinylchloride in , polyethylene in , and nylon in the late s Historical Note 8. Processing requirements for plastics led to the development of injection molding based on die casting, one of the metal casting processes and other polymer-shaping techniques. Electronics products have imposed unusual demands on manufacturing in terms of miniaturization.
The evolution of the technology has been to package more and more devices into smaller and smaller areasin some cases millions of transistors onto a at piece of semiconductor material that is only 12 mm 0. The history of electronics processing and packaging dates from only a few decades Historical Notes More than one processing operation is usually required to transform the starting material into final form.
The operations are performed in the particular sequence required to achieve the geometry and condition defined by the design specification. Three categories of processing operations are distinguished: 1 shaping operations, 2 property-enhancing operations, and 3 surface processing operations.
Shaping operations alter the geometry of the starting work material by various methods. Common shaping processes include casting, forging, and machining. Property-enhancing operations add value to the material by improving its physical properties without changing its shape. Heat treatment is the most common example. Surface processing operations are performed to clean, treat, coat, or deposit material onto the exterior surface of the work.
Common examples of coating are plating and painting. Property-enhancing processes and surface processing operations are covered in Part VII. Shaping Processes Most shape processing operations apply heat, mechanical force, or a combination of these to effect a change in geometry of the work material. There are various ways to classify the shaping processes. The classification used in this book is based on the state of the starting material, by which we have four categories: 1 solidification processes, in which the starting material is a heated liquid or semifluid that cools and solidifies to form the part geometry; 2 particulate processing, in which the starting material is a powder, and the powders are formed and heated into the desired geometry; 3 deformation processes, in which the starting material is a ductile solid commonly metal that is deformed to shape the part; and 4 material removal processes, in which.
The process consists of: 1 pouring the uid into a mold cavity and 2 allowing the uid to solidify, after which the solid part is removed from the mold. In the first category, the starting material is heated sufficiently to transform it into a liquid or highly plastic semifluid state. Nearly all materials can be processed in this way. Metals, ceramic glasses, and plastics can all be heated to sufficiently high temperatures to convert them into liquids.
With the material in a liquid or semifluid form, it can be poured or otherwise forced to flow into a mold cavity and allowed to solidify, thus taking a solid shape that is the same as the cavity. Most processes that operate this way are called casting or molding. Casting is the name used for metals, and molding is the common term used for plastics. This category of shaping process is depicted in Figure 1. In particulate processing, the starting materials are powders of metals or ceramics.
Although these two materials are quite different, the processes to shape them in particulate processing are quite similar. The common technique involves pressing and sintering, illustrated in Figure 1. In deformation processes, the starting workpart is shaped by the application of forces that exceed the yield strength of the material. For the material to be formed in this way, it must be sufficiently ductile to avoid fracture during deformation. To increase ductility and for other reasons , the work material is often heated before forming to a temperature below the melting point.
Deformation processes are associated most closely with metalworking and include operations such as forging and extrusion, shown in Figure 1. Materialremovalprocesses areoperations thatremoveexcessmaterialfromthestarting workpiece so that the resulting shape is the desired geometry. The most important processes in this category are machining operations such as turning, drilling, and milling, shown in Figure 1.
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These cutting operations are most commonly applied to solid metals, performed using cutting tools that are harder and stronger than the work metal. Grinding is another common process in this category. Other material removal processes are known as nontraditional processes because they use lasers, electron beams, chemical erosion, electric discharges,andelectrochemicalenergytoremovematerialratherthancuttingorgrindingtools.
It is desirable to minimize waste and scrap in converting a starting workpart into its subsequent geometry. Certain shaping processes are more efficient than others in terms of material conservation. Material removal processes e. The material removed from the starting shape is waste, at least in terms of the unit operation. Manufacturing processes that transform nearly all of the starting material into product and require no subsequent machining to achieve final part geometry are called net shape processes.
Other processes require minimum machining to produce the final shape and are called near net shape processes. Property-Enhancing Processes The second major type of part processing is performed to improve mechanical or physical properties of the work material. These processes do not alter the shape of the part, except unintentionally in some cases. The most important property-enhancing processes involve heat treatments, which include various annealing Starting diameter Diameter Chip after turning. Sintering of powdered metals and ceramics is also a heat treatment that strengthens a pressed powder metal workpart.
Surface Processing Surface processing operations include 1 cleaning, 2 surface treatments, and 3 coating and thin film deposition processes. Cleaning includes both chemical and mechanical processes to remove dirt, oil, and other contaminants from the surface. Surface treatments include mechanical working such as shot peening and sand blasting, and physical processes such as diffusion and ion implantation. Coating and thin film deposition processes apply a coating of material to the exterior surface of the workpart. Common coating processes include electroplating, anodizing of aluminum, organic coating call it painting , and porcelain enameling.
Thin film deposition processes include physical vapor deposition and chemical vapor deposition to form extremely thin coatings of various substances. Several surface-processing operations have been adapted to fabricate semiconductor materials into integrated circuits for microelectronics.
These processes include chemical vapor deposition, physical vapor deposition, and oxidation. They are applied to very localized areas on the surface of a thin wafer of silicon or other semiconductor material to create the microscopic circuit. Components of the new entity are connected either permanently or semipermanently. Permanent joining processes include welding, brazing, soldering, and adhesive bonding. They form a joint between components that cannot be easily disconnected. Certain mechanical assembly methods are available to fasten two or more parts together in a joint that can be conveniently disassembled.
The use of screws, bolts, and other threaded fasteners are important traditional methods in this category. Other mechanical assembly techniques form a more permanent connection; these include rivets, press fitting, and expansion fits. Special joining and fastening methods are used in the assembly of electronic products. Someofthemethods areidenticaltoorareadaptations oftheprecedingprocesses,for example, soldering. Electronics assembly is concerned primarily with the assembly of components such as integrated circuit packages to printed circuit boards to produce the complex circuits used in so many of todays products.
The extensive use of machinery in manufacturing began with the Industrial Revolution. It was at that time that metal cutting machines started to be developed and widely used. These were called machine toolspower-driven machines used to operate cutting tools previously operated by hand. Modern machine tools are described by the same basic definition, except that the power is electrical rather than water or steam, and the level of precision and automation is much greater today. Machine tools are among the most versatile of all production machines. They are used to make not only parts for consumer products, but also components for other production machines.
Both in a historic and a reproductive sense, the machine tool is the mother of all machinery. Other production machines include presses for stamping operations, forge hammers for forging, rolling mills for rolling sheet metal, welding machines for welding, and insertion machines for inserting electronic components into printed circuit boards. The name of the equipment usually follows from the name of the process.
Mold cavity for molten metal Mold cavity for hot polymer Roll reduce work thickness Die squeeze work to shape Extrusion die reduce cross-section Die shearing, forming sheet metal Cutting tool material removal Fixture hold workpart Jig hold part and guide tool Grinding wheel material removal Electrode fusion of work metal Fixture hold parts during welding. Production equipment can be general purpose or special purpose.
General purpose equipment is more flexible and adaptable to a variety of jobs. It is commercially available for any manufacturing company to invest in. Special purpose equipment is usually designed to produce a specific part or product in very large quantities. The economics of mass production justify large investments in special purpose machinery to achieve high efficiencies and short cycle times.
This is not the only reason for special purpose equipment, but it is the dominant one. Another reason may be because the process is unique and commercial equipment is not available. Some companies with unique processing requirements develop their own special purpose equipment. Production machinery usually requires tooling that customizes the equipment for the particular part or product. In many cases, the tooling must be designed specifically for the part or product configuration.
When used with general purpose equipment, it is designed to be exchanged. For each workpart type, the tooling is fastened to the machine and the production run is made. When the run is completed, the tooling is changed for the next workpart type. When used with special purpose machines, the tooling is often designed as an integral part of the machine. Because the special purposemachine is likely being used for mass production, the tooling may never need changing except for replacement of worn components or for repair of worn surfaces. The type of tooling depends on the type of manufacturing process.
Table 1. Details are provided in the chapters that discuss these processes. Production systems consist of people, equipment, and procedures designed for the combination of materials and processes that constitute a firms manufacturing operations. Production systems can be divided into two categories: 1 production facilities and 2 manufacturing support systems, as shown in Figure 1. Production facilities refer to the physical equipment and the arrangement of equipment in the factory. Manufacturing support systems are the procedures used by the company to manage production and solve the technical and logistics problems encountered in ordering materials, moving work through the factory, and ensuring that products meet quality.
Both categories include people. People make these systems work. In general, direct labor workers are responsible for operating the manufacturing equipment; and professional staff workers are responsible for manufacturing support. The facilities touch the product. Facilities also include the way the equipment is arranged in the factorythe plant layout. The equipment is usually organized into logical groupings; which can be called manufacturing systems, such as an automated production line, or a machine cell consisting of an industrial robot and two machine tools.
A manufacturing company attempts to design its manufacturing systems and organize its factories to serve the particular mission of each plant in the most efficient way. Over the years, certain types of production facilities have come to be recognized as the most appropriate way to organize for a given combination of product variety and production quantity, as discussed in Section 1.
Different types of facilities are required for each of the three ranges of annual production quantities. A job shop makes low quantities of specialized and customized products. The products are typically complex, such as space capsules, prototype aircraft, and special machinery. The equipment in a job shop is general purpose, and the labor force is highly skilled. A job shop must be designed for maximum flexibility to deal with the wide product variations encountered hard product variety. If the product is large and heavy, and therefore difficult to move, it typically remains in a single location during its fabrication or assembly.
Workers and processing equipment are brought to the product, rather than moving the product to the equipment. This type of layout is referred to as a fixed-position layout, shown in Figure 1. In a pure situation, the product remains in a single location during its entire production. Examples of such products include ships, aircraft, locomotives, and heavy machinery. In actual practice, these items are usually built in large modules at single locations, and then the completed modules are brought together for final assembly using large-capacity cranes.
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No notes for slide. Groover fundamentals-modern-manufacturing-4th-solution-manuel 1. Any other reproduction or translation of this work beyond that permitted by Sections or of the United States Copyright Act without the permission of the copyright owner is unlawful. Give an example of each category. A primary industry is one that cultivates and exploits natural resources, such as agriculture or mining.
A secondary industry takes the outputs of primary industries and converts them to consumer and capital goods. Examples of secondary industries are textiles and electronics. A tertiary industry is in the service sector of the economy. Examples of tertiary industries are banking and education. Provide an example. Capital goods are those purchased by companies to produce goods or provide services. Examples of capital goods are aircraft and construction equipment. Generally production quantity is inversely related to product variety.
A factory that produces a large variety of products will produce a smaller quantity of each. A company that produces a single product will produce a large quantity. Manufacturing capability refers to the technical and physical limitations of a manufacturing firm and each of its plants. Three categories of capability mentioned in the text are 1 technological processing capability, 2 physical size and weight, and 3 production capacity.
The three basic categories of engineering materials are 1 metals, 2 ceramics, and 3 polymers. A fourth category, composites, is a non-homogeneous mixture of the other types and therefore is not a basic category. A shaping process changes the geometry of the work material machining or forging. A surface processing operation does not alter the geometry, but instead alters surface of the work painting or plating.
Provide an example process for each subclass. The two subclasses of assembly processes are 1 permanent joining and 2 mechanical fastening. Examples of permanent joining include welding or adhesive bonding. Examples of mechanical fastening include threaded fasteners, such as nuts and bolts, and rivets. Batch production is where groups, lots, or batches or materials or parts are processed together through the manufacturing operations. All units in the batch are processed at a given station before the group proceeds to the next station.
In a medium or low quantity production situation, the same machines are used to produce many types of products. Whenever a machine switches from one product to another, a changeover occurs. The changeover requires the machine setup to be torn down and set up for the new product.
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Batch production allows the changeover time 3. A process layout is one where the machinery in a plant is arranged based on the type of process it performs. To produce a product it must visit the departments in the order of the operations that must be performed. This often includes large travel distances within the plant. A process layout is often used when the product variety is large the operation sequences of products are dissimilar. A product layout is one where the machinery is arranged based on the general flow of the products that will be produced. Travel distance is reduced because products will generally flow to the next machine in the sequence.
A product layout works well when all products tend to follow the same sequence of production. A common organizational structure includes the following three manufacturing support departments: 1 manufacturing engineering, 2 production planning and control, and 3 quality control. Multiple Choice Quiz There are 18 correct answers in the following multiple choice questions some questions have multiple answers that are correct.
To attain a perfect score on the quiz, all correct answers must be given. Each correct answer is worth 1 point. Each omitted answer or wrong answer reduces the score by 1 point, and each additional answer beyond the correct number of answers reduces the score by 1 point. Percentage score on the quiz is based on the total number of correct answers. What are these categories and give an example of each? The three types of elements are metals e. The noble metals are copper, silver, and gold.
Primary bonding is strong bonding between atoms in a material, for example to form a molecule; while secondary bonding is not as strong and is associated with attraction between molecules in the material. In ionic bonding, atoms of one element give up their outer electron s to the atoms of another element to form complete outer shells.
The atoms in a crystalline structure are located at regular and repeating lattice positions in three dimensions; thus, the crystal structure possesses a long-range order which allows a high packing density. The atoms in a noncrystalline structure are randomly positioned in the material, not possessing any repeating, regular pattern. The common point defects are 1 vacancy - a missing atom in the lattice structure; 2 ion-pair vacancy Schottky defect - a missing pair of ions of opposite charge in a compound; 3 interstitialcy - a distortion in the lattice caused by an extra atom present; and 4 Frenkel defect - an ion is removed from a regular position in the lattice and inserted into an interstitial position not normally occupied by such an ion.
Elastic deformation involves a temporary distortion of the lattice structure that is proportional to the applied stress. Plastic deformation involves a stress of sufficient magnitude to cause a permanent shift in the relative positions of adjacent atoms in the lattice. Plastic deformation generally involves the mechanism of slip - relative movement of atoms on opposite sides of a plane in the lattice. Grain boundaries block the continued movement of dislocations in the metal during straining. As more dislocations become blocked, the metal becomes more difficult to deform; in effect it becomes stronger.
Materials typically possessing a crystalline structure are metals and ceramics other than glass. Some plastics have a partially crystalline structure. Materials typically having a noncrystalline structure include glass fused silica , rubber, and certain plastics specifically, thermosetting plastics. Crystalline structures undergo an abrupt volumetric change as they transform from liquid to solid state and vice versa. This is accompanied by an amount of energy called the heat of fusion that must be added to the material during melting or released during solidification.
Noncrystalline materials melt and solidify without the abrupt volumetric change and heat of fusion. Multiple Choice Questions There are 20 correct answers in the following multiple choice questions some questions have multiple answers that are correct. To achieve design function and quality, the material must be strong; for ease of manufacturing, the material should not be strong, in general. Engineering stress divides the load force on the test specimen by the original area; while true stress divides the load by the instantaneous area which decreases as the specimen stretches.
The tensile strength is the maximum load experienced during the tensile test divided by the original area. The yield strength is the stress at which the material begins to plastically deform. It is usually measured as the 0. Because of necking that occurs in the test specimen. Work hardening, also called strain hardening, is the increase in strength that occurs in metals when they are strained. When the material is perfectly plastic and does not strain harden. In a compression test, the specimen cross-sectional area increases as the test progresses; while in a tensile test, the cross-sectional area decreases.
Barreling of the test specimen due to friction at the interfaces with the testing machine platens. What is the test commonly used to determine the strength properties of such materials? A three-point bending test is commonly used to test the strength of brittle materials. The test provides a measure called the transverse rupture strength for these materials. Hardness is defined as the resistance to indentation of a material. It is tested by pressing a hard object sphere, diamond point into the test material and measuring the size depth, area of the indentation.
Different hardness tests and scales are required because different materials possess widely differing hardnesses. A test whose measuring range is suited to very hard materials is not sensitive for testing very soft materials. The recrystallization temperature is the temperature at which a metal recrystallizes forms new grains rather than work hardens when deformed. Viscosity is the resistance to flow of a fluid material; the thicker the fluid, the greater the viscosity. A Newtonian fluid is one for which viscosity is a constant property at a given temperature.
Most liquids water, oils are Newtonian fluids. Viscoelasticity refers to the property most commonly exhibited by polymers that defines the strain of the material as a function of stress and temperature over time. It is a combination of viscosity and elasticity. Multiple Choice Quiz There are 15 correct answers in the following multiple choice questions some questions have multiple answers that are correct.
It is the elastic region that is characterized by a proportional relationship between stress and strain. The plastic region is characterized by a power function - the flow curve. Viscosity is the resistance to flow.
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