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You have successfully signed out and will be required to sign back in should you need to download more resources. Description For courses in manufacturing processes at two- or four-year schools An up-to-date text that provides a solid background in manufacturing processes Manufacturing Engineering and Technology, 7e , presents a mostly qualitative description of the science, technology, and practice of manufacturing.
Engage Students: Examples and industrially relevant case studies demonstrate the importance of the subject, offer a real-world perspective, and keep students interested.
Support Instructors and Students: A Companion Website includes step-by-step Video Solutions, the Pearson eText, and color versions of all figure and tables in the book.
Coverage of the latest technological advances, like rapid prototyping , the most dramatic change in manufacturing in recent years. Also includes coverage of nanofabrication, rapid tooling, and semisolid metalworking Chapter 20 making this one of the most up-to-date texts available.
Lists and process comparisons give students a through look at manufacturing processes and operations. Thechapters on specific groups of manufacturing processes and operations feature lists of typical parts produced by the processes described in the chapter, as well as a list of competing and alternative processes to produce the same types of parts.
Four kinds of end-of-chapter problems help reinforce concepts in each chapter: Review Questions; Qualitative Problems; Quantitative Problems; and Synthesis, Design, and Projects.
Comprehensive bibliographies are far more complete than any other manufacturing textbooks. For example, see the case studies on the manufacture of golf clubs Chapter 24 , artificial hip stems Chapter 11 , and monosteel piston Chapter June Duggal Free Download June Charles H. Roth, Larry April April 6. Popular Files. Grewal Book Free Download April Bansal Book Free October Verma Book Free Download February Dutta Free Downlaod August 5.
Trending on EasyEngineering. Peck, Walter E. Polymers have gone from being cheap substitutes for natural products to providing high-quality options for a wide variety of applications. Further advances and breakthroughs supporting the economy can be expected in the coming years. Polymers are derived from petroleum, and their low cost has its roots in the abundance of the feedstock, in the ingenuity of the chemical engineers who devised the processes of manufacture, and in the economies of scale that have come with increased usage.
Less than 5 percent of the petroleum barrel is used for polymers, and thus petroleum is likely to remain as the principal raw material for the indefinite future. Polymers constitute a high-value-added part of the petroleum customer base and have led to increasing international competition in the manufacture of commodity materials as well as engineering thermoplastics and specialty polymers.
Polymers are now produced in great quantity and variety. Polymers are used as film packaging, solid molded forms for automobile body parts and TV cabinets, composites for golf clubs and aircraft parts airframe as well as interior , foams for coffee cups and refrigerator insulation, fibers for clothing and carpets, adhesives for attaching anything to anything, rubber for tires and tubing, paints and other coatings to beautify and prolong the life of other materials, and a myriad of other uses.
It would be impossible to conceive of our modern world without the ubiquitous presence of polymeric materials. Polymers have become. The unique and valuable properties of polymers have their origins in the molecular composition of their long chains and in the processing that is performed in producing products. Both composition including chemical makeup, molecular size, branching and cross-linking and processing affected by flow and orientation are critical to the estimated properties of the final product.
This chapter considers the various classes of polymeric materials and the technical factors that contribute to their usefulness. In spite of the impressive advances that have been made in recent years, there are still opportunities for further progress, and failure to participate in this development will consign the United States to second-class status as a nation.
The familiar categories of materials called plastics, fibers, rubbers, and adhesives consist of a diverse array of synthetic and natural polymers. It is useful to consider these types of materials together under the general rubric of structural polymers because macroscopic mechanical behavior is at least a part of their function. Compared with classical structural materials like metals, the present usage represents a considerable broadening of the term.
As shown in Table 3. Because these materials go through several manufacturing steps before reaching the final consumer, the ultimate impact on the national economy is measured in the hundreds of billions of dollars each year. These materials have many different chemical and physical forms, such as cross-linked versus non-cross-linked, crystalline versus amorphous, and rubbery versus glassy.
More recently, structural polymers having liquid crystalline order have become important. Structural polymers are rarely used in the pure form but often contain additives in small quantities, such as antioxidants, stabilizers, lubricants, processing aids, nucleating agents, colorants, and antistatic agents or, in larger quantities, plasticizers or fillers. There is rapid growth in the areas of blends and composites. In composites, a material of fixed shape, such as particles filler or fibers, is dispersed in a polymer matrix.
The filler or fiber may be an inorganic material or another organic polymer. Blends or alloys on the other hand consist of two or more polymers mixed together and differ from composites in that the geometry of the phases is not predetermined prior to processing.
Some polymers are used for many different purposes. A good example is poly ethylene terephthalate , or PET, which was originally developed as a textile fiber.
It is now used in film and tape virtually all magnetic recording tape is based on PET , as a molding material, and as the matrix for glass-filled composites. One of its largest uses is for making bottles, especially for soft drinks. PET is also used in blends with other polymers, such as polycarbonate. The word "plastic" is frequently used loosely as a synonym for "polymer," but the meaning of "polymer'' is based on molecular size while "plastic" is defined in terms of deformability.
Plastics are polymeric materials that are formed into a variety of three-dimensional shapes, often by molding or melt extrusion processes. They retain their shape when the deforming forces are removed, unlike some other polymers such as the elastomers, which return to their original shape.
Plastics are usually categorized as thermoplastics or thermosets, depending on their thermal processing behavior. Thermoplastics are polymers that soften and flow upon heating and become hard again when cooled.
This cycle can be repeated many times, which makes reprocessing during manufacturing or recycling after consumer use possible using heat fabrication techniques such as extrusion or molding. The polymer chains in thermoplastics are linear or branched and do not become cross-linked as in the case of thermosets. While there are many different chemical types of thermoplastics, those made from only four monomers ethylene, propylene, styrene, and vinyl chloride account for about 90 percent of all thermoplastics produced in the United States Figure 3.
Of these four types, polypropylene has grown most rapidly in recent years—production has increased eightfold over the past two decades. Thermoplastic polyesters, primarily PET, are growing even more rapidly at the present time driven mainly by.
Future activities will focus strongly on recycling. In the case of PET, recycling can be accomplished by chemical depolymerization to monomers or oligomers followed by repolymerization to PET or other products. Such processes are currently in use for products that come into contact with food, while simple reprocessing is used for less critical products. The so-called engineering thermoplastics, which include the higher-performance, more expensive polymers such as the polyacetals, polycarbonates, nylons, polyesters, polysulfones, polyetherimides, some acrylonitrile butadiene styrene ABS materials, and so on, have generally exhibited stronger growth than the commodity plastics see Table 3.
These materials generally have greater heat resistance and better mechanical properties than the less expensive commodity thermoplastics and, therefore, are used in more demanding applications, such as aircraft, automobiles, and appliances.
A major area of development is. TABLE 3. The area of blends and alloys is reviewed separately below. New products and advances in processes have resulted from the ring-opening polymerization of cyclic oligomers; for example, new developments in polycarbonates are particularly noteworthy. Other new products can be expected based on copolymers, and entirely new polymers are under development. A further category sometimes referred to as high-performance engineering thermoplastics commands even higher prices for yet higher levels of performance.
These include highly aromatic polymers such as poly phenylene sulfide , several new polyamides, polysulfones, and polyetherketones. Development of new molecular structures has dominated this sector.
Polymer chains with quite rigid backbones have liquid crystalline order, which offers unique structural properties as described below. Figure 3. Approximately one-third are used in packaging, primarily containers and film. The data in Figure 3. To understand the diversity of products and opportunities that is possible, it is useful to review developments that have occurred in thermoplastics based on ethylene, one of the simplest monomers possible.
Commercial production of polyethylene commenced in England during the early s using a free radical process operating at very high pressures 30, to 50, psi. The structure proved to be far more complex than the simple textbook repeat unit, —CH 2 CH 2 —, would suggest Figure 3.
The backbone has short-and long-chain branches. The short-chain branches, typically four carbons long, interfere with the ability. Because the short-chain branches reduce crystallinity and, thus, density, this material is called low-density polyethylene LDPE.
In the late s, a linear or unbranched form of polyethylene was developed as a result of advances in coordination polymerization catalysis.
An accidental finding by K. Ziegler in the early s at the Max Planck Institute of Mulheim, Germany, resulted in a fundamentally new approach to polyolefins. It was found that transition metal complexes could catalyze the polymerization of ethylene under mild conditions to produce linear chains with more controlled structures. As a result, this polymer was more crystalline with higher density, and it became known as high-density polyethylene HDPE.
Similar catalytic procedures were used by G. Natta to produce crystalline polypropylene. The properties of this polymer are a result of unprecedented control of the stereochemistry of polymerization. The newer material did not replace the older one; it was used for different purposes.
The cost factor plus innovations in. It is a copolymer of ethylene and an alpha-olefin like butene-1, hexene Thus, short-chain branches of controlled length and number are introduced into the chain without any long-chain branches, and the material is called linear low-density polyethylene LLDPE; see Figure 3. As a result, the production of LDPE initially declined, but its production has been growing again since Construction of new high-pressure production facilities may be required in the next decade to meet demands.
Currently this is the only process by which copolymers can be made with polar monomers such as vinyl acetate or acrylic acid. HDPE is fabricated primarily by molding. Blow-molded food bottles and auto gasoline tanks constitute major markets. Very large containers made by rotational molding represent a specialized growth area.
A process known as "gel spinning" has been commercialized, which produces fibers of ultrahigh-molecular-weight polyethylene. New technology based on single-site metallocenes holds promise for the production of a new range of products.
This brief review of the history and future prospects for olefin polymers illustrates the need for research of all types e. These materials are complex in terms of molecular structure, and so there are many ways to tailor their behavior provided the basic knowledge and tools for structural determination are available and are integrated with innovative process technology.
Much of the present research is directed toward the design of catalysts that yield materials that are easier to process. Rapid progress has resulted from an integration of catalyst synthesis and reactor and process design. As a recent example, a new polyolefin alloy product has been developed by exposing a designed catalyst to a series of different olefin monomer feeds to produce a polymer particle that is composed of polymers with different properties.
Extrusion of those particles results directly in a polymer alloy. Structural thermoplastics are a vital part of the national economy, and considerable opportunity remains for economic growth and scientific inquiry. New specialized materials will continue to offer rewards in the marketplace.
At the high-performance end, several entirely new polymer structures are likely to emerge over the next decade. A major part of the growth in "new" materials will be in the area of blends or alloys. The vitality of thermoplastics cannot be judged only on the basis of the introduction of what might be called "new materials.
This trend is expected to continue but will require greater sophistication in terms of process technology, characterization, and structure-property relationships especially modeling than has been required in the past. Thermoset materials are broadly defined as three-dimensional, chemically resistant networks, which in various technologies are referred to as gels, vulcanizates, or "cured" materials. Applications as diverse as coatings, contact lenses, and epoxy adhesives can be cited. Thermosets are defined here as rigid network materials, that is, as materials below their glass transition temperature.
Thermosets are formed when polyfunctional reactants generate three-dimensional network structures via the progression of linear growth, branching, gelation, and postgelation reactions.
The starting monomers must include at least some reactive functionality greater than two, which will ensure that as the reaction proceeds, the number of chain ends will increase. They will eventually interconnect to produce a gelled network material. This process may be followed by observing the viscosity increase as a function of time or from the percent reaction completed. In many cases, this can be predicted mathematically.
As the gel begins to form, the soluble fraction decreases and eventually is eliminated altogether. An important consideration with respect to rigid thermosetting networks is the extensively studied interrelationship between reactivity, gelation, and vitrification. As the reaction proceeds, the glass transition temperature rises to meet the reaction temperature, and the system vitrifies; that is, the motion of the main chain stops.
At this point, the reaction essentially stops for all practical purposes. This has been conveniently described in terms of a time-temperature-transformation cure diagram. Thermosetting systems can be formed either by chain or step polymerization reactions.
The chemistry of thermoset materials is even now only partially understood, because they become difficult to characterize once they reach the three-dimensional insoluble network stage. Thermal and dynamic mechanical methods have been widely used to characterize these materials, and solid-state nuclear magnetic resonance NMR has begun to have some impact on this problem.
Thermoset materials make up approximately 15 percent of the plastics produced in the United States. Phenolics make up the largest class of thermoset materials. Some polyurethanes are classified as thermosets, although many urethane and urea materials can be produced in linear thermoplastic or soluble forms, such as the well-known elastomeric spandex fibers.
Urea-formaldehyde-based materials continue to be significant and, in fact, were the systems used in the first "carbonless" paper. Unsaturated polyesters are derived from maleic anhydride and propylene glycol, which are then dissolved in styrene and cross-linked into a network. They have gained significant importance in. The resulting glass-reinforced composites are frequently called sheet molding compounds SMC. Thermoset materials, although smaller in total volume than the thermoplastics, are used in a number of very high performance applications, such as matrix resins or structural adhesives in composite systems such as those used for aerospace applications.
These composites are normally reinforced with glass, aramid, or carbon fibers. Important examples of such matrix materials include the epoxies, bismaleimides, cyanates, acetylenes, and more recently, benzocyclobutene systems.
The existing database for matrix resins and structural adhesives is much more established for thermosets than it is for high-performance thermoplastics such as the poly arylene ether ketones , certain polyaryl imides, and poly phenylene sulfide.
Major research needs in the area of polymer-based composites include better ways to improve the toughness of thermosetting systems and better techniques for processing those formed from high-performance thermoplastics.
Advances in processing and toughening thermosets are occurring on several fronts. Methods for generating the network have been investigated by many organizations. The most conventional methods involve use of a thermal-convection-oven-type curing, often in autoclaves. However, recently there has been considerable effort in electromagnetic or microwave processing of high-performance polymeric matrix resins, particularly for structural adhesives and composite structures.
An approach for "toughening" that has been investigated over the last 10 years involves the incorporation of either rubbers or reactive engineering thermoplastics into networks, such as epoxies, to develop a complex morphology. Here the added material is dispersed as isolated domains or forms co-continuous morphologies. Most of the original studies focus on rubber toughening, and an extensive body of literature deals with utilization of carboxyl functional nitrile rubbers to toughen epoxy adhesives.
More recently, advantages associated with the utilization of engineering thermoplastics have been realized. These include, for example, the ability to retain stiffness and thermo-oxidative stability, as well as in some cases, chemical resistance. These properties are often severely diminished with rubber-toughened thermosetting systems.
Fracture toughness can be significantly improved. This is significant in terms of improving the durability of advanced organic materials utilized in structural adhesives and composites. The interfacial adhesion between the separate polymer phases, as well as their proportions, morphology, and molecular characteristics, is of prime significance in improving fracture toughness. Other forefront areas include the development of new chemistries and, in particular, better characterization of leading candidate materials.
The bismaleimides are considered to be somewhat more thermally stable than the epoxy materials and are being seriously considered for various applications, such as the high-speed civil transport airplane, which is planned for commercialization in the next 10 years. Aspects of the flammability of these materials are also crucial. Aryl-phosphine-oxide-containing materials show considerable promise for producing advanced organic materials with significantly improved flammability resistance.
A new development is the possibility of bridging organic and inorganic materials to produce organic-inorganic composite networks. Elastomers, or rubbers, are soft and compliant polymers that are able to experience large, reversible deformations. Only long-chain polymers are capable of this type of elasticity.
Elastomers are typically amorphous, network polymers with lower cross-link density than thermoset plastics. Most thermosets can be made to function as elastomers above their glass transition temperatures.
Historically, elastomers have played an important role in the industrialization, prosperity, and security of the United States. According to the functions, pads are made from either hardenable tool steel or soft low-carbon steel. At the mating section of the die, it must be closely fit with contoured pads. In stamping dies, there are different types of pads. They are as follows:. At the cutting punches, a stripper pad is used to strip or pull the metals.
Stripper pads are usually spring-loaded and flat. When it cut, the metal used to collapse on the shank or body. The stripper pads used to mount the die shoes, mainly the upper shoe. Before the contact of forming punch with the metal, in the lower section of die, metal has to be taken down.
It is done at the time of the wipe bending process. The amount of bending force and the force pressure pad should be equivalent. On the sheets of metals, the amount of downward force and pressure is exerted. This determines that how much flow in the metal can be agreed and the die cavity by drawing can enter. According to that, flow in metals can be controlled by the draw pads. The shoes die used to move from up to down. The Spools, Keepers and Shoulder Bolts are used as the fasteners of this movement.
By screw or dowels, Spools, Keepers and Shoulder Bolts are secured with lower and upper die shoes. The retainer can be used to secure the components with lower and upper die shoes at the time of forming and cutting process. The popular retainer among all is a ball-lock retainer.
It is a high-precision retainer. It is used to align and secure the forming and cutting punches accurately. It uses a spring-loaded ball-bearing. In the teardrop shape, the spring-loaded ball-bearings are locked not to come out the punches. This ball-lock retainer gives advantages to the technicians to reinstall the punches by removing it quickly.
Spring is a component that can be used to supply force to the strip, form metal and hold it. Different springs can be used here. Most popular springs are gas spring, coil and urethane springs.
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