Exam 3 FINAL Micro

CHAPTER 1: MATERIAL AND PROCESSES IN MANUFACTURING

Difference of System & Process: process implies a sequence of steps, processes, or operations for production of goods and services. A system is a collection of many processes, including workers, machines, and information.
Difference of Manufacturing system and manufacturing process: Manufacturing system is a group of machine put in a certain layout to produce a product. Manufacturing process is what you do on a machine. For example : drilling, milling, grinding are manufacturing processes.
The production system includes the manufacturing system plus all the other functional areas of the plant for information, design, analysis, and control.These subsystems are connected by various means to each other to produce either goods or services or both.
Production systems include : People, Money, Equipment, Materials, Supplies, Markets, Management, Manufacturing System, All aspects of commerce
Input and of a manufacturing system: Raw
Materials, Component Supplies, Subassemblies information
Output of a manufacturing system: Components, Goods, Products, Parts, Subassemblies
Design engineer responsibilities; What the design is to accomplish, Assumptions that can be made, Service environments the product must withstand, Final appearance of the product, Product designed with the knowledge that certain manufacturing processes will be used
Manufacturing engineer responsibilities: Select and coordinate specific processes and equipment, Supervise and manage their use,
Industrial (Manufacturing) engineer responsibilities: Manufacturing systems layout
Materials engineers responsibilities: Specify ideal materials, Develop new and better materials
Five manufacturing system designs
The Job Shop: includes large varieties of components, general-purpose machines, and a functional layout. machines are collected by function (all lathes together, all broaches together, all milling machines together) and the parts are routed around the shop in small lots to the various machines. For example a job shop includes Lathe, Drilling and grinding machine.
The Flow Shop: larger volumes of the same part or assembly, special-purpose machines and equipment, less variety, and more mechanization. Flow shop layouts are typically either continuous or interrupted and can be for manufacturing or assembly. If continuous, a production line is built that basically runs one large-volume complex item in great quantity and nothing else. The common light bulb is made this way. A transfer line producing an engine block is another typical example. If interrupted, the line manufactures large lots but is periodically “changed over” to run a similar but different component. For example : making car production line.
The linked-cell manufacturing system (L-CMS) is composed of manufacturing and subassembly cells (Figure 1-9) connected to final assembly (linked) using a unique form of inventory and information control called kanban. The L-CMS is used in lean production systems where manufacturing processes and subassemblies are restructured into U-shaped cells so they can operate on a one-piece-flow basis, like final assembly.
The project shop is characterized by the immobility of the item being manufactured. In the construction industry, bridges and roads are good examples. In the manufacture of goods, large airplanes, ships, large machine tools, and locomotives are manufactured in project shops. It is necessary that the workers, machines, and materials come to the site. The number of end items is not very large, and therefore the lot sizes of the components going into the end item are not large.Thus the job shop usually supplies parts and subassemblies to the project shop in small lots.
Continuous processes are used to manufacture liquids, oils, gases, and powders. These manufacturing systems are usually large plants producing goods for other producers or mass-producing canned or bottled goods for consumers. The manufacturing engineer in these factories is often a chemical engineer. For example, in producing chemical, oil, soft drink,…
Examples of basis manufacturing processes:
Casting, foundry, or molding process: produce parts that often require other follow-on processes. Casting uses molten metal to fil a cavity. The metal retains the desired shape of the mold cavity after solidification.
Forming or metalworking process: utilize materials that has been cast or molded. The materials pass through a series of forming operations, so the form of the material for a specific operation may be the result of all the prior operations.
Machining (material removal) process: refer to the removal of certain selected areas from a part in order to obtain a desired shape of finish. For example: drilling, milling.
Joining and assembly: joining parts to each other, for example: welding, fastening.
Surface treatments (finishing): cleaning, removing burrs left by machining, or providing protective and/or decorative surfaces on workpieces. For example: painting, galvanizing.
Rapid prototyping: produce components directly from the software using specialized machines driven by computer-aided design package.
Heat treating: heating or cooling of a metal for the specific purpose of altering its metallurgical and mechanical properties.
Common aspect of manufacturing:
A job is a group of related operations generally performed at one station, and a station is a position or location in a machine (or process) where specific operations are performed
An operation is a distinct action performed to produce a desired result or effect. Categories of operations includes Materials handling and transport, Processing, Packaging, Inspecting and testing, Storing
Treatments operate continuously on a workpiece. Example: Heat treating, curing, galvanizing, plating, finishing, chemical cleaning, painting
Tools, tooling and workholders : Lowest mechanism in the production is a tool. Used to hold, shape or form the unfinished product
Tooling for measurement and inspection: Rulers, calipers, micrometers, and gages. Precision devices are laser optics or vision systems that utilize electronics to interpret results
Joining process: Mechanical fastening, Soldering and brazing, Welding, Press, shrink, or snap fittings, Adhesive bonding, Assembly processes
CHAPTER 2: MANUFACTURING SYSTEM DESIGN. the major functional elements or departmental areas of the production system: A production system includes all aspects of the business, including design engineering, manufacturing engineering, sales, advertising, production and inventory control (scheduling and distribution), and most important, the manufacturing system
Marketing and sales department. Finance and accounting (not shown). Manufacturing system (where goods are produced). Manufacturing engineering (designs processes and systems to make goods). Personnel or human resources (HR).

Research and development (not shown). Design engineering (designs the product). Purchasing and procurement. Production planning and control (scheduling the manufacturing system).
Information technology. Inventory control. Quality control, testing, and inspection. Plant engineering or maintenance
Inputs to the manufacturing system include material information, and energy. The system is a complex set of elements that includes machines, people, material-handling equipment, and tooling . Workers are the internal customers.
Modeling and analysis of manufacturing system are difficult because:
In the absence of a system design, the manufacturing system can be very complex , difficult to be define, and have conflict goal.
The data or information may be difficult to secure, inaccurate, conflicting, missing, or even too abundant to digest and analyze.
Relationships maybe awkward to express in analytical terms, and interactions may be nonlinear; thus many analytical tools cannot be applied with accuracy. System size may be inhibit analysis.
System are always dynamic and change during analysis. The environment can change the system and vice versa.
All systems analyses are subject to errors of omission (missing information) and commission (extra information). Some of these are related to breakdowns or delay in feedback elements.
Manufacturing System:
Job Shop: distinguish feature is its functional design. In the job shop a variety of products are manufactured, which results in small manufacturing lot sizes often one of a kind. Example: Auto repair, hospital, restaurant, university, machine shop, metal fabrication. Advantage: Its ability to make a wide variety of products.
Route Sheet: are used as the production control device to define the path of the material through the manufacturing system. The route sheet lists manufacturing operations and associated machine tools for each workpiece. The route sheets travel with the parts, which move in batches between the process. operation sheet describes what machining or assembly operations are done to the parts at particular machines.
A process flowchart is a chart of the separate steps of a process in sequential order. throughout the process flow chart, the production team will suggest material and their amount needed during the process to create the product. It shows the various level of the product, subassemblies, and components.
Process planning for the Job shop:
Size and shape of the geometric components of the workpiece.
Tolerances, as applied by the designer
Material from which the part is to be made
Properties of material being machined
Number of pieces to be produced
Machine tools available for this workpiece.
Flow shop:has a product-oriented layout composed mainly of flow lines. When the volume gets very large especially in an assembly line, it is called mass production. Advantage: can have a very high production rates.
PLC (programmable logic controller): a computer used to control machines in automation manufacturing.
Flexible manufacturing systems use CNC machines for processing and AGVs, robots, or conveyors to transport parts”: The CNC Machines for processing give the system greater flexibility. A Flexible manufacturing system need both automation and flexibility. Therefor AGV (automated guided vehicle) , CNC machines, robots and conveyors are added to support the manufacturing.
The design of the product influence the design of the manufacturing system: Manufacturing system is a sequence of processes and people that actually produce the desired product. The manufacturing system includes complex sets of elements that includes machines, people, materials-handling equipment, and tooling. The manufacturing system vary by the products they make o assemble. In the absence of a system design, the manufacturing system can be very complex, be difficult to define, and have conflicting goal
Project shop: A product must remain in a fixed position, or location during manufacturing because of its size an weight. The project shop involves large stationary assemblies (projects), where components are usually fabricated elsewhere and transported to the site. The project shop often produces one-of-a-kind products with very low production rates. The work is schedule using project management technique like CPM (critical path method), or PERT (program evaluation and review techniques)
Continuous process: the project physically flows. Example oil refineries, chemical processing plants, and food processing; Continuous processes are the most efficient but least flexible. They usually have leanest, simplest production system because easiest to control, having the least work-in-process . But usually involve complex chemical reaction and thus special kind of manufacturing engineer.
Lean manufacturing systems: employs U-shaped cells or parallel rows to manufacture components. The final assembly lines are convert to mixed model, final assembly so that the demands for subassemblies and components is leveled, making the demand for components the same every day. Subassembly line are also reconfigured into volume flexible, single piece flow cells.
In linked-cell-system, the key propriety aspects are the U-shaped manufacturing and assembly cells.
CHAPTER 44 THE ENTERPRISE
Marketing: The chief activities of marketing are forecasting sales, advertising, and stimating future demand for existing products. Selling the product is the primary interest of marketing. Including: Sales forecast of future demand for existing products. 2. Sales order data. 3. Customer quality requirements. 4. Customer reliability requirements. 5. New products or modifications for existing products. 6. Customer feedback on products. 7. Customer service (repair or replacement of defective products). Sales order information is central to production planning and control. Products are either made to stock (finished-goods inventory) or made to fill customer orders. Marketing develops information on new products or new uses for old products. This information usually goes to research and development or to product design engineers. Marketing also gathers customer feedback on existing products. The marketing department, which is in direct customer contact, gathers complaints about product performance and communicates them to design and/or manufacturing
Finance functions involve management of the company’s assets. For the production system, finance provides information and services concerning the following elements: 1. Internal capital financing. 2. Budgeting. 3. Investment analysis. Periodically, the manufacturing manager, as well as other managers, must submit budgets of expected financial requirements and expenditures to the finance department. The decisions made during budget preparation and the discussions of budget adjustments have a significant impact on the manufacturing system’s operation.
Accounting: The accounting department maintains the company’s financial records. Money is used to keep score, so to speak. Accounting also provides the data needed for decision making. For the production system, accounting provides information and services on the following: 1. Cost accounting. 2. Special reports. 3. Data processing. human resources (HR) department: typically represents workers, one of the key physical elements of the manufacturing system, and provides information and services concerning the following: 1. Recruitment. 2. Training. 3. Labor relations. 4. Safety.
Research and development (R&D) involves invention or discovery and innovation and their development in terms of achievable ends, such as new materials, products, processes, tools, and techniques
Engineering providing information and services on the following: 1. Product design engineering or design. 2. Manufacturing engineering. 3. Industrial engineering. 4. Plant engineering. 5. Quality engineering.
Product Design Engineering: a design will often develop in three phases. the conceptual or idea phase, the designer conceives of an idea for a device that will accomplish some function. This stage establishes the functional requirements that must be met by the device. functional-design stage, the product is designed so that it will achieve the functional requirements established in the conceptual stage. Often, more than one prototype will be made, suggesting alternative ways in which the functions can be met. At this stage, the designer is usually more concerned with materials than with processes and may ignore the fact that the designed configuration cannot be produced economically utilizing the material being considered production design: attention should also be given to the appearance of the product. The design engineer must, of course, know that certain manufacturing processes and operations exist that can manufacture the desired product. The designer must also know their limitations, relative costs, and process capabilities (accuracy, tolerance requirements, etc.) to design for manufacture (DFM)
Manufacturing engineers (MFEs)1 address the design, planning, and management of all manufacturing processes and systems. Using the specifications, the process of manufacturing engineering plans the manufacture of the product, determining which machine tools, operations, workers, cutting tools, workholding devices, and other manufacturing system components should be used to meet quality, cost, delivery, and functional requirements. Manufacturing engineers work with the product designers on production producibility [design for manufacturing and assembly (DFMA)]. Once manufacturing has begun, changes to the product design can be expensive. These changes are usually called ECOs—engineering change orders. Manufacturing engineering may also design individual processes, design or modify machine tools, design tooling and specifications (workholding devices and cutting tools and dies), specify the sequence of production processes and operations (process planning), and solve processing problems on the plant floor.
Industrial Engineering: responsible for determining the number of workers, machines, and materials needed on the plant floor to turn the ideas developed in R&D, marketing, and procurement into real products. Industrial engineers look for the ‘‘better way’’ to produce products and services under uncertain conditions and constraints, such as the nature of the plant, materials, machines on hand, personnel, and available capital. The industrial engineering department is responsible for many elements of the manufacturing system and the production system, including some that overlap with those of the manufacturing engineer. These include the following: 1. Production methods analysis. 2. Work measurement (time study, motion study, and time standards). 3. Setup reduction (SMED). 4. Safety and ergonomics. 5. Manufacturing system design (factory design), including material handling. 6. Quality engineering (which may be a separate functional group) and Six Sigma. 7. Plant maintenance information.
The lean engineer is an IE who knows lean manufacturing, has Six Sigma capabilities with a green (zero waste) mentality.
Plant engineering: responsible for in-plant construction and maintenance, meaning machine tool and equipment repair; heating and air-conditioning system maintenance; and repair of any other mechanical, hydraulic, or electrical problems not necessarily related to the manufacturing system
Quality engineering is responsible for ensuring that the quality of the product and its components meets the standards specified by the designer before, during, and after manufacturing
Procurement and purchasing functions in a company involve primarily the acquisition of specified materials, equipment, services, and supplies of the proper quality, in the correct quantities, at the best prices, and at the correct time
Production planning translates sales into forecasts by part number. The authority to manufacture the product is translated into a master production schedule (MPS), a key planning document specifying the products to be manufactured, the quantity to be produced, and the delivery date to the customer
Manufacturing Resource Planning (MRP) is a computerized system to control inventory within the mass system.
Given a schedule showing the expected demand of independent demand items (a master production schedule) and given the relationship between independent and dependent demand items (bills of materials), MRP will calculate the quantities of dependent demand items needed and when they will be needed.
Reason to have inventory control: 1. Fluctuation in demand and/or supply. 2. Protection against process breakdowns or stopping production due to a shortage. 3. Replacement parts for lost batches or defective lots. 4. Overproduction in anticipation of future demand. 5. Protection from defective parts. 6. Goods in transport. 7. Just in case they are needed. 8. Quantity purchasing.
Inventory control governs finished goods, raw materials, purchased components, and work-in-process within the factory.
Functions of a total inventory control system 1. Analyze and plan inventory requirements. 2. Purchase raw materials and component parts in the amounts needed according to scheduled usage. 3. Receive and record the receipt of purchased materials. 4. Provide adequate facilities to store raw material, work-in-process, and finishedgoods inventory. 5. Maintain accurate records of inventories on hand and on order. 6. Install realistic controls for materials in stores and for the assuance of materials, parts, and supplies when needed. the difference between production control and inventory control: Production control: to control where the parts need to go, when they need to go, and how many need to go (lot size), so they develop the schedule to ensure that delivery of the final product meets the customer demand; Inventory control: governs finished goods, raw materials, purchased components, and work-in-process within the factory. The idea is to achieve a balance between too little inventory (with possible stockouts of raw materials) and too much inventory (with investments and storage space tied up). material requirements planning (mrp): To control inventory within the mass system, a computerized system called. To support the job shop-flow shop systems. Material requirements planning has become manufacturing resource planning (MRP) enterprise resource planning (ERP) software: responsible for final scheduling of production, dispatching, and releasing purchase orders
Subsequent sophistication of MRP by adding feedback of actual results has led to closed-loop manufacturing resource planning (MRP II).
CHAPTER 15 FUNDAMENTALS OF METAL FORMING
Plasticity is the ability of a material to flow as a solid without deterioration of properties
The main independent variables in metal forming processes (those aspects of the process for which control is direct and immediate)
Starting material: When specifying the starting material, we may define not only the chemistry of that material but also its condition. In so doing, we define the initial properties and characteristics. These may be chosen entirely for ease of fabrication, or they may be restricted by the desire to achieve the required final properties upon completion of the deformation process.
Starting geometry of the workpiece: The starting geometry may be dictated by previous processing, or it may be selected from a variety of available shapes. Economic considerations often influence this decision.
Tool or die geometry: This is an area of major significance and has many aspects, such as the diameter and profile of a rolling mill roll, the bend radius in a sheet-forming operation, the die angle in wire drawing or extrusion, and the cavity details when forging. Since the tooling will induce and control the metal flow as the material goes from starting shape to finished product, success or failure of a process often depends on tool geometry.
Lubrication: It is not uncommon for friction between the tool and the workpiece to account for more than 50% of the power supplied to a deformation process. Lubricants can also act as coolants, thermal barriers, corrosion inhibitors, and parting compounds. Hence, their selection is an important aspect in the success of a forming operation. Specification includes type of lubricant, amount to be applied, and method of application.
Starting temperature: Since material properties can vary greatly with temperature, temperature selection and control are often key to the success or failure of a metal forming operation. Specification of starting temperatures may include the temperatures of both the workpiece and the tooling.
Speed of operation. Most deformation processing equipment can be operated over a range of speeds. Since speed can directly influence the forces required for deformation, the lubricant effectiveness, and the time available for heat transfer, its selection affects far more than the production rate.
Amount of deformation: While some processes control this variable through the design of tooling, others, such as rolling, may permit its adjustment at the discretion of the operator. the main dependent variables in metal forming processes (those aspects for which control is entirely indirect)
Force or power requirements: A certain amount of force or power is required to convert a selected material from a starting shape to a final shape, with a specified lubricant, tooling geometry, speed, and starting temperature. A change in any of the independent variables will result in a change in the force or power required, but the effect is indirect. We cannot directly specify the force or power; we can only specify the independent variables and then experience the consequences of that selection.
Material properties of the product: While we can easily specify the properties of the starting material, the combined effects of deformation and the temperatures experienced during forming will certainly change them. The starting properties of the material may be of interest to the manufacturer, but the customer is far more concerned with receiving the desired final shape with the desired final properties. It is important to know, therefore, how the initial properties will be altered by the shape-producing process.
Exit (or final) temperature: Deformation generates heat within the material. Hot workpieces cool when in contact with colder tooling. Lubricants can break down or decompose when overheated or may react with the workpiece. The properties of an engineering material can be altered by both the mechanical and thermal aspects of a deformation process. Therefore, if we are to control a process and produce quality products, it is important to know and control the temperature of the material throughout the deformation. (Note: The fact that temperature may vary from location to location within the product further adds to the complexity of this variable.)
Surface finish and precision: The surface finish and dimensional precision of the resultant product depend on the specific details of the forming process.
Nature of the material flow: In deformation processes, dies and tooling generally exert forces or pressures and control the movement of the external surfaces of the workpiece. While the objective of an operation is the production of a desired shape, the internal flow of material may actually be of equal importance. As will be shown later in this chapter, product properties can be significantly affected by the details of material flow, and that flow depends on all the details of a process. Customer satisfaction requires not only the production of a desired geometric shape but also that the shape possess the right set of companion properties, without any surface or internal defects.
Three distinct ways To gain information on the interdependencies of independent and dependent variables:
Experience. generally requires long-time exposure to a process and is often limited to the specific materials, equipment, and products encountered during past contact. Younger employees may not have the experience necessary to solve production problems. Moreover, a single change in an area such as material, temperature, speed, or lubricant may make the bulk of past experience irrelevant.
Experiment. While possibly the least likely to be in error, direct experiment can be both time consuming and costly. Size and speed of deformation are often reduced when conducting laboratory studies. Unfortunately, lubricant performance and heat transfer behave differently at different speeds and sizes, and their effects are generally altered.The most valid experiment, therefore, is one conducted under full-size and full-speed production conditions—generally too costly to consider to any great degree. While laboratory experiments can provide valuable insight, caution should be exercised when extrapolating lab-scale results to more realistic production conditions.
Process modeling. Here, the process is approached through high-speed computing and one or more mathematical models. Numerical values are selected for the various independent variables, and the models are used to compute predictions for the dependent outcomes. Most techniques rely on the applied theory of plasticity with various simplifying assumptions. Alternatives vary from crude, first-order approximations to sophisticated, computer-based methods, such as finite element analysis. Various models may incorporate strain hardening, thermal softening, heat transfer, and other phenomena. Solutions may be algebraic relations that describe the process and reveal trends and relations between the variables or simply numerical values based on the specific input features.
Temperature Concerns:
Hot working is defined as the plastic deformation of metals at a temperature above the recrystallization temperature. At the temperatures of hot working, recrystallization eliminates the effects of strain hardening, so there is no significant increase in yield strength or hardness, or corresponding decrease in ductility. cold working : The plastic deformation of metals below the recrystallization temperature
When compared to hot working, the advantages of cold working include the following
1. No heating is required.
2. Better surface finish is obtained.
3. Superior dimensional control is achieved since the tooling sets dimensions at room temperature. As a result, little, if any, secondary machining is required.
4. Products possess better reproducibility and interchangeability.
5. Strength, fatigue, and wear properties are all improved through strain hardening.
6. Directional properties can be imparted.
7. Contamination problems are minimized.

Some disadvantages associated with cold-working processes include the following:
1. Higher forces are required to initiate and complete the deformation.
2. Heavier and more powerful equipment and stronger tooling are required.
3. Less ductility is available.
4. Metal surfaces must be clean and scale-free.
5. Intermediate anneals may be required to compensate for the loss of ductility that accompanies strain hardening.
6. The imparted directional properties may be detrimental.
7. Undesirable residual stresses may be produced.

CHAPTER 16 BULK FORMING PROCESS
Classification of Bulk deforming processes
Primary processes reduce a cast material into slabs, plates, and billets
Secondary processes reduce shapes into finished or semifinished products
Bulk Deforming Process:
Rolling: reduce the thickness or change the cross section of a material through compressive forces exerted by rolls. rolling is often the first process that is used to convert material into a finished wrought product. Thick starting stock can be rolled into blooms, billets, or slabs, or these shapes can be obtained directly from continuous casting. Blooms have a square or rectangular cross section Billets are usually smaller than a bloom and can have a square or circular cross section Can be further rolled into structural shapes. Slabs are a rectangular solid with a width greater than twice the thickness Can be used to produce plates, sheets, or strips
In Basis rolling process: Metal is passed between two rolls that rotate in opposite directions Friction acts to propel the material forward Metal is squeezed and elongates to compensate for the decrease in cross-sectional area
In hot rolling, temperature control is required for successful forming Temperature of the material should be uniform. Rolling is terminated when the temperature falls to about 50 to 100 degrees above the recrystallization temperature Ensures the production of a uniform grain size
In Cold rolling products sheet, strip, bar and rod products with smooth surfaces and accurate dimensions
Rolling mill configurations: Smaller diameter rolls produce less length of contact for a given reduction and require less force to produce a given change in shape Smaller cross section provides a reduced stiffness. Rolls may be prone to flex elastically because they are only supported on the ends.
Continuous rolling mill: Billets, blooms, and slabs are heated and fed through an integrated series of nonreversing rolling mills. Synchronization of rollers may pose issues
Ring rolling: One roll is placed through the hole of a thick-walled ring and a second roll presses on the outside Produces seamless rings; Circumferential grain orientation and is used in rockets, turbines, airplanes, pressure vessels, and pipelines
Characteristics, Quality, and Precision of Rolled Products: Hot-rolled products have little directionality in their properties; Hot-rolled products are therefore uniform and have dependable quality; Surfaces may be rough or may have a surface oxide known as mill scale; Dimensional tolerances vary with the kind of metal and the size of the product; Cold-rolled products exhibit superior surface finish and dimensional precision
Forging -Forging is a term applied to a family of processes that induce plastic deformation through localized compressive forces applied through dies. most forging is done with workpieces above the recrystallization temperature. The metal may be (1) drawn out to increase its length and decrease its cross section, (2) upset to decrease the length and increase the cross section, or (3) squeezed in closed impression dies to produce multidirectional flow. Common forging processes include: 1. Open-die drop-hammer forging; 2. Impression-die drop-hammer forging; 3. Press forging; 4. Upset forging; 5. Automatic hot forging; 6. Roll forging; 7. Swaging; 8. Net-shape and near-net-shape forging
Open-die Hammer Forging: Same type of forging done by a blacksmith but mechanical equipment performs the operation; An impact is delivered by some type of mechanical hammer; Simplest industrial hammer is a gravity drop machine; Computer controlled-hammers can provide varying blows.
Impression-Die Hammer Forging: The dies are shaped to control the flow of metal; Upper piece attaches to the hammer and the lower piece to the anvil; Metal flows and completely fills the die; Excess metal may squeeze out of the die (This metal is called flash); Flashless forging can be performed if the metal is deformed in a cavity that provides total confinement; Many forged products are produced with a series of cavities (First impression is called edging, fullering, or bending; Intermediate impressions are for blocking the metal to approximately its final shape; Final shape is given in its final forging operation)
Extrusion: metal is compressed and forced to flow through a suitably shaped die to form a product with reduced but constant cross section. may be performed either hot or cold. hot extrusion is commonly employed for many metals to reduce the forces required, eliminate cold-working effects, and reduce directional properties. A ram advances from one end, causing the billet to first upset and conform to the confining chamber. As the ram continues to advance, the pressure builds until the material flows plastically through the die and extrudes. Aluminum, magnesium, copper, lead, and alloys of these metals are commonly extruded, taking advantage of the relatively low yield strengths and low hot-working temperatures. Steels, stainless steels, nickel-based alloys, and titanium are far more difficult to extrude.
Advantages of Extrusion: Many shapes can be produced that are not possible with rolling; No draft is required; Amount of reduction in a single step is only limited by the equipment, not the material or the design; Dies are relatively inexpensive; Small quantities of a desired shape can be produced economically
Extrusion Methods: With either process, the speeds of hot extrusion are usually rather fast. Extruded products can emerge at rates up to 300 m/min (1000 ft/min)
Direct extrusion: Solid ram drives the entire billet to and through a stationary die; Must provide power to overcome friction
Indirect extrusion: A hollow ram pushes the die back through a stationary, confined billet
Lubrication is important to reduce friction and act as a heat barrier
Metal flow in extrusion: Flow can be complex; Surface cracks, interior cracks and flow-related cracks need to be monitored; Process control is important
Extrusion of Hollow Shapes : Two methods of extruding hollow shapes using internal mandrels (a) the mandrel and ram have independent motions; in part (b) they move as a single unit.
Wire-, rod-, and tube-drawing: operations reduce the cross section of a material by pulling it through a die. In many ways, the processes are similar to extrusion, but the applied stresses are now tensile, pulling on the product rather than pushing on the workpiece. The reduction in area is usually restricted to between 20 and 50%, since higher values require higher pulling forces that may exceed the tensile strength of the reduced product.To produce a desired size or shape, multiple draws may be required through a series of progressively smaller dies.
Tube drawing can be used to produce high-quality tubing where the product requires the smooth surfaces, thin walls, accurate dimensions, and added strength (from the strain hardening) that are characteristic of cold forming. Internal mandrels are often used to control the inside diameter of tubes, which range from about 12 to 250 mm (0.5 to 10 in.) in diameter. Thick-walled tubes and those less than 12 mm (0.5 in.) in diameter are often drawn without a mandrel in a process known as tube sinking.
Wire drawing is essentially the same process as bar drawing except that it involves smaller-diameter material. Because the material can now be coiled, the process can be conducted in a somewhat continuous manner on rotating draw blocks,
Cold Forming, Cold Forging, and Impact Extrusion: cold forming: slugs of material are squeezed into or extruded from shaped die cavities to produce finished parts of precise shape and size.Workpiece temperature varies from room temperature to several hundred degrees Fahrenheit.
Cold heading is a form of upset forging, used to make the enlarged sections on the ends of rod or wire (i.e. heads of nails, bolts, etc.) impact extrusion, can also be incorporated into cold forming. A metal slug of predetermined size is positioned in a die cavity, where it is struck a single blow by a rapidly moving punch. The metal may flow forward through the die, backward around the punch, or in a combination mode. In forward extrusion, the diameter is decreased while the length increases. Backward extrusion shapes hollow parts with a solid bottom. The punch controls the inside shape, while the die shapes the exterior. The wall thickness is determined by the clearance between the punch and die, and the bottom thickness is set by the stop position of the punch. The impact extrusion processes were first used to shape low-strength metals such as lead, tin, zinc, and aluminum into products method of manufacturing of thick-walled seamless pipes using hot piercing of solid steel rod: Thick-walled seamless tubing can be made by rotary piercing. A heated billet is fed longitudinally into the gap between two large, convex tapered rolls. These rolls are rotated in the same direction, but the axes of the rolls are offset from the axis of the billet by about 6 degrees, one to the right and the other to the left. The clearance between the rolls is preset at a value less than the diameter of the incoming billet. As the billet is caught by the rolls, it’s simultaneously rotated and driven forward. The reduced clearance between the rolls forces the billet to deform into a rotating ellipse
CHAPTER 17 SHEET-FORMING PROCESSES differences of sheet metal forming as compared to bulk forming (1) Bulk forming uses heavy machinery to apply 3D stresses; (2) Sheet metal processes, on the other hand, generally involve place stress loadings and lower forces than bulk forming; (3) Almost all sheet metal forming is considered to be secondary processing
The main categories of sheet metal forming: Shearing; Bending; Drawing
Shearing: is the mechanical cutting of materials without the formation of chips or the use of burning or melting. Sheared or blanked edges generally is not smooth because it uses in a single operation, it require secondary finishing to smooth out burrs along the edges.
Simple shearing: When sheets of metal are to be sheared along a straight line, squaring shears are frequently used
Slitting : is the lengthwise shearing process used to cut coils of sheet metal into several rolls of narrower width. the differences between piercing and blanking: Piercing and blanking are shearing operations where a part is removed from sheet material by forcing a shaped punch through the sheet and into a shaped die. Blanking- the piece being punched out becomes the workpiece; Piercing- the punchout is the scrap and the remaining strip is the workpiece
Types of Piercing and Blanking
Lancing – is a piercing operation that forms either a line cut (slit) or hole, like those shown in the left-hand portion. Lancing can combined with bending to form tabs or opening like those found in vents or louvers. Lancing is also used to permit the adjacent metal to flow more readily in subsequent forming operations.
Nibbling - a contour is progressively cut by producing a series of overlapping slits or notches.
Shaving – is a finishing operation in which a small amount of metal is sheared away from the edge of an already blanked part.
Cutoff – an operation with a punch and die are used to separate a stamping or other product from a strip of stock.
Rules for Design for piercing and blanking
Diameters of pierced holes should not be less than the thickness of the metal, with a minimum of 0.3 mm (0.025 in.). Smaller holes can be made, but with difficulty.
The minimum distance between holes, or between a hole and the edge of the stock, should be at least equal to the metal thickness.
The width of any projection or slot should be at least 1 times the metal thickness and never less than 2.5 mm ( in.).
Keep tolerances as large as possible. Tolerances below about 0.075 mm (0.003 in.) will require shaving.
Arrange the pattern of parts on the strip to minimize scrap.
Bending: is the plastic deformation of metals about a linear axis with little or no change in the surface area. Multiple bends can be made simultaneously, but to be classified as true bending, and treatable by simple bending theory, each axis must be linear and independent of the others. If multiple bends are made with a single die, the process is often called forming. When the axes of deformation are not linear or are not independent, the processes are known as drawing and/or stretching. The location that is neither stretched nor compressed is known as the neutral axis of the bend
To prevent flattening or wrinkling when bending a tube: We specialize in Mandrel bending, or more precisely called Rotary Draw bending. This process uses an internal mandrel to support the tube/pipe while bending in order to prevent flattening and wrinkling. This is especially necessary for bending thin wall materials on a tight bend radius
Angle Bending (Bar Folder and Press Brake): Bar folders make angle bends up to 150 degrees in sheet metal; Press brakes make bends in heavier sheets or more complex bends in thin material
Design Considerations for bending: determining the smallest bend radius that can be formed without metal cracking. Three factors that determine the minimum bend radius for a material: (1) Formed without metal cracking; (2); Ductility of the metal; (3) The thickness of the material being bent determining the dimensions of a flat blank that will produce a bent part of the desired precision.
Air-Bend, Bottoming, and Coining Dies
Bottoming dies contact and compress the full area within the tooling (Angle of the bend is set by the geometry of the tooling)
Air bend dies produce the desired geometry by simple three-point bending
If bottoming dies go beyond the full-contact position, the operation is similar to coining
Roll bending: is a continuous form of three-point bending where plates, sheets, beams, pipe, and even rolled shapes and extrusions are bent to a desired curvature using forming rolls
Draw bending, compression bending, and press bending: The flexibility of each process is somewhat limited because a certain length of the product must be used for clamping.
Draw bending, the workpiece is clamped against a bending form and the entire assembly is rotated to draw the workpiece along a stationary pressure tool.
Compression bending, the bending form remains stationary and the pressure tool moves along the surface of the workpiece.
Press bending, utilizes a downward-descending bend die, which pushes into the center of material that is supported on either side by wing dies.
Tube bending: Key parameters: outer diameter of the tube, wall thickness, and radius of the bend
Roll Forming: is a process by which a metal strip is progressively bent as it passes through a series of forming rolls; Only bending takes place during this process, and all bends are parallel to one another; A wide variety of shapes can be produced, but changeover, setup, and adjustment may take several hours
Seaming is a bending operation that can be used to join the ends of sheet metal in some form of mechanical interlock. Seaming machines range from small hand-operated types to large automatic units capable of producing hundreds of seams per minute. Common products include cans, pails, drums, and other similar containers.
Flanges can be rolled on sheet metal in essentially the same manner as seams
The objective of straightening or flattening is the opposite of bending, and these operations are often performed before subsequent forming to ensure the use of flat or straight material that is reasonably free of residual stresses. Done before subsequent forming to ensure the use of flat or straight material. Various methods to straighten material: Roll straightening (Roller levering); Stretcher leveling- material is mechanically gripped and stretch until it reaches the desired flatness
Butt-welded pipe: steel skelp is heated to a specified hot-working temperature by passing it through a tunnel-type furnace; The skelp rolls back on each other through rollers and produces a welded seam
The lap-welding process for making pipe: the skelp now has beveled edges and the rolls form the weld by forcing the lapped edges down against a supporting mandrel.This process is used primarily for larger sizes of pipe, with diameters from about 50 mm (2 in.) to 400 mm (14 in.).
CHAPTER 30 FUNDAMENTAL OF JOINING:
Consolidation Processes consist of: Welding; Brazing; Soldering; Fasteners; Adhesives; Shrink Fits; Slots and Tabs
Welding is the consolidation of two materials by means of temperature and/or pressure to cause the materials to melt or diffuse at the joint. Welding can be done in a wide variety of conditions and methods and is therefore on of the most common consolidation processes.
There are two forms of welding: Both process can cause changes in the structure of the material, and must be considered when selecting a process
Solid State welding where pressure and heat are used to cause the diffusion at the joint, causing the parts to fuse together
Fusion welding where heat is applied to create molten material at the joint, which fuses the parts upon solidification
Four basic types of fusion welds:
Bead welds: are made directly onto a flat surface and therefore require no edge preparation, used primarily for joining thin sheets of metal, building up surfaces, and depositing hard-facing (wear-resistant) materials
Groove welds are used when full-thickness strength is desired on thicker material.
Fillet welds are used for tee, lap, and corner joints and require no special edge preparation
Plug welds attach one part on top of another and are often used to replace rivets or bolts.A hole is made in the top plate and welding is started at the bottom of this hole.
The possible problems associated with the high temperatures that are commonly used in welding: the structure of the metal may be significantly altered
Even when no melting occurs, the heating and cooling of the welding process can affect the metallurgical structure and quality of both the weld and the adjacent material.
Classification of common welding processes along with their AWS (American Welding Society) designations.
Oxyfuel gas welding (OFW): Oxyacetylene welding (OAW), Pressure gas welding (PGW)
Solid state welding (SSW): Forge welding (FOW), Cold welding (CW), Friction welding (FRW), Ultrasonic welding (USW), Explosion welding (EXW), Roll welding (ROW)
Arc welding (AW): Shielded metal arc welding (SMAW), Gas metal arc welding (GMAW), Gas tungsten arc welding (GTAW), Flux cored arc welding (FCAW), Submerged arc welding (SAW), Submerged arc welding (SAW), Plasma arc welding (PAW), Stud welding (SW)
Resistance welding (RW): Resistance spot welding (RSW), Resistance seam welding (RSW), Projection welding (RPW)
Unique processes: Thermit welding (TW), Laser-beam welding (LBW), Electroslag welding (ESW), Flash welding (FW), Induction welding (IW), Electron-beam welding (EBW
Some of the common types of weld defects:,
Incomplete fusion between the weld and base metals.
Incomplete penetration (insufficient weld depth),
Unacceptable weld shape or contour
Arc strikes, spatter, undesirable metallurgical changes (aging, grain growth, or transformations), and excessive distortion fusion zone can have a chemistry that is different from the filler metal: Fusion zone, is actually a mixture of parent metal and electrode or filler metal, with the ratio depending upon the particular process, the type of joint, and the edge preparation. The metal in the fusion zone is cast material with a microstructure reflecting the cooling rate of the weld. This region cannot be expected to have the same properties and characteristics as the wrought material being welded, since their processing histories and resulting structures are usually different. Adequate mechanical properties, therefore, can only be achieved by selecting filler rods or electrodes, which have properties in their as-deposited conditionthat equal or exceed those of the wrought parent metal.
Design Consideration for welding: Welding produces monolithic structures; Welded joints do not stop crack propagation, cracks propagation typically does not travel through a bolted joint ; Vibration stresses are transferred through a weld joint, bolted joints adsorb some of the vibration; Welded structure are more rigid than bolted assemblies
Heat Effect: In fusion welding, the heat melts some of the base material, which is then rapidly cooled, creating changes in the granular structure; The pool of metal bonding the base material is a blend of each material, and forms a cast structure in the joint zone; Surrounding the pool of metal is the heat affected zone, where metallurgical properties have been changed.
Classification of Common Welding Processes by Rate of Heat Input
Low Rate of Heat Input: Oxyfuel welding (OFW), Electroslag welding (ESW), Flash welding (FW)
Moderate Rate of Heat Input: Shielded metal arc welding (SMAW), Flux cored arc welding (FCAW), Gas metal arc welding (GMAW), Submerged arc welding (SAW), Gas tungsten arc welding (GTAW)
High Rate of Heat Input: Plasma arc welding (PAW), Electron-beam welding (EBW), Laser welding (LBW), Spot and seam resistance welding (RW), Percussion welding heat-affected zone (HAZ): Adjacent to the fusion zone, and wholly within the base material. In this region, the parent metal has not melted but has been subjected to elevated temperatures for a brief period of time. Heat affected zone is subjected to enough heat to cause metallurgical changes, leading to phase transformations, embrittlement, precipitation, or cracking
Post weld heat treatment can be used to reduce the impact of the heat affected zone. Welding techniques can be used to reduce the heat distortion in welds; Preheating the base metal also reduces weld distortion; Distortion is the result of thermally induced stresses

Chapter 31: Gas Flame and Arc Processes Sections
Oxyfuel-gas welding (OFW) refers to a group of welding processes that use the flame produced by the combustion of a fuel gas and oxygen as the source of heat. It was the development of a practical torch to burn acetylene and oxygen,
Three different types of flames can be obtained by varying the oxygen-toacetylene (or oxygen-to-fuel gas) ratio.
Natural flame: If the ratio is between 1:1 and 1.15:1, all reactions are carried to completion and a neutral flame is produced.
Oxidizing Flame: A higher ratio, such as 1.5:1, produces an oxidizing flame, which is hotter than the neutral flame (about 3600C, or 6000 F) but similar in appearance.
Carburizing Flame: created by excess fuel.
Acetylene is the hottest and most versatile of the fuel gases.
Alternative fuels include propane, propylene, and stabilized methyl-acetylene-propadiene, best known by the trade name of MAPP gas.
MAPP gas MAPP is the second-hottest gas, with a flame temperature between 2875 and 3000C
Propylene is actually a generic name for a variety of mixed gases, often consisting of propane and ethylene or other hotter-burning chemicals.
Propane has a flame temperature between 2480 and 2540 C (4500 and 4600 F). While flame temperature is slightly lower, these gases can be safely stored in ordinary pressure tanks.
Butane, natural gas, and hydrogen have also been used in combination with air or oxygen for brazing and to weld the low-melting-temperature, nonferrous metals.
Fusion Welding: Almost all oxyfuel-gas welding is fusion welding. The metals to be joined are simply melted where a weld is desired and no pressure is required. Because a slight gap often exists between the pieces being joined,filler metal can be added in the form of a solid metal wire or rod.
Fluxes: To promote the formation of a better bond,fluxes may be used to clean the surfaces and remove contaminating oxide.
Arc: arc between two electrodes was a concentrated heat source that could produce temperatures approaching 4000 C. As early as 1881, various attempts were made to use an arc as the heat source for fusion welding. A carbon rod was selected as one electrode and the metal workpiece became the other.
Straight polarity ((SPDC) or DCEN): If direct current is used and the electrode is made negative, for direct-current electrode-negative.
Reverse polarity: the condition when the work is made negative and the electrode positive
Variable Polarity: power supplies also alternate between DCEP and DCEN conditions, using rectangular waveforms to vary the fraction of time in each mode, as well as the frequency of switching.
Consumable-electrode processes: In one group of arc-welding processes, the electrode is consumed and thus supplies the metal needed to fill the joint.
Non consumable-electrode processes, The second group of arc-welding processes employs a tungsten (or carbon) electrode, which is not consumed by the arc, except by relatively slow vaporization. A separate metal wire is required to supply the filler metal.
Four processes make up the bulk of consumable-electrode arc welding: Shielded metal arc welding (SMAW). Flux-cored arc welding (FCAW). Gas metal arc welding (GMAW). Submerged arc welding (SAW).
Submerged arc welding (SAW) No shielding gas is used in this process, it is most suitable for making flat-butt or fillet welds in low carbon steels
Shielded metal arc welding (SMAW), also called stick welding or covered-electrode welding, is among the most widely used welding processes because of its versatility and because it requires only low-cost equipment.
Flux-cored arc welding (FCAW) overcomes some of the limitations of the shielded metal arc process by moving the powdered flux to the interior of a continuous tubular electrode
Gas metal arc welding (GMAW): If the supplemental shielding gas flowing through the torch becomes the primary protection for the arc and molten metal, there is no longer a need for the volatilizing flux. The consumable electrode can now become a continuous, solid, uncoated metal wire or a continuous hollow tube with powdered alloy additions in the center, known as a metal-cored electrode. Because shielding is provided by the flow of gas, and fluxing and slag-forming agents are no longer required, the gas metal arc process can be applied to all metals.
Arc penetration is the depth of melting in the work piece
The coated electrodes are classified by the tensile strength of the deposited weld metal, the welding position in which they may be used, the preferred type of current and polarity (if direct current), and the type of coating.
A variety of electrode coatings have been developed and can be classified as cellulosic, rutile (titanium oxide), and basic. The cellulosic and rutile coatings contain variable amounts of SiO2, TiO2, FeO, MgO, Na2O, and volatile matter. Upon decomposition, the volatile matter may release hydrogen, which can dissolve in the weld metal and lead to embrittlement or cracking in the joint.
Metal powder (usually iron) can be added to the electrode coating to significantly increase the amount of weld metal that can be deposited with a given size electrode wire and current—but with a noticeable decrease in penetration depth.
Globular transfer: If the voltage and amperage are increased, the mode becomes one of globular transfer. The electrode melts from the heat of the arc, and metal drops form with a diameter equal to or greater than the diameter of the electrode wire. This is the least desirable mode of transfer because the arc is loud and erratic, with lots of splashing or spatter.
Spray transfer (GMAW-ST) occurs with even higher currents and voltages (25 to 32 V and about 200 A), argon gas shielding, and DCEP conditions. Small droplets emerge from a pointed electrode at a rate of hundreds per second. Because of their small size and the greater electromagnetic effects, the droplets are easily propelled across the arc in any direction, irrespective of the effects of gravity. Spray transfer is accompanied by deep penetration and low spatter.
Pulsed spray transfer (GMAW-P) was developed to overcome some of the limitations of conventional spray transfer. In this mode, a low welding current is first used to create a molten globule on the end of the filler wire. A burst of high current then ‘‘explodes’’the globule and transfers the metal across the arc in the form of a spray.
Bulk welding: happen in a modification of the submerged arc, iron powder is first deposited into the joint (ahead of the flux) as a means of increasing deposition rate. A single weld pass can then produce enough filler metal to be equivalent to seven or eight conventional submerged arc passes.
Stud welding (SW) is an arc-welding process used to attach studs, screws, pins, or other fasteners to a metal surface. Stud welding requires almost no skill on the part of the operator. Once the stud and ferrule are placed in the gun and the gun positioned on the work, all the operator has to do is pull the trigger
Chapter 32: Resistance and Solid-State Welding Processes
There are a number of welding and cutting processes that utilize heat sources other than oxyfuel flames and electric arcs, solid-state welding, resistance welding, Resistance spot welding (RSW), Resistance seam welding (RSEW), resistance butt welding, Edition, Projection welding (RPW), Projection welding (RPW), deformation resistance welding
Solid-state welding processes, create joints without any melting of the workpiece or filler material.
Resistance welding, heat and pressure are combined to induce coalescence. Electrodes are placed in contact with the material, and electrical resistance heating is used to raise the temperature of the workpieces and the interface between them. The required temperature can often be attained, and coalescence can be achieved, in a few seconds or less. Resistance welding, therefore, is a very rapid and economical process, extremely well suited to automated manufacturing.
Resistance spot welding (RSW) is the simplest and most widely used form of resistance welding, providing a fast, economical means of joining overlapped materials that will not require subsequent disassembly.
HEAT: heat for resistance welding is obtained by passing a large electrical current through the work pieces for a short period of time. The amount of heat input can be determined by the basic relationship: H = I^2 x R x t
H = total heat input in joules. I = current in amperes. R = electrical resistance of the circuit in ohms. t = length of time during which current is flowing in seconds
Faying surfaces: The resistance between the surfaces to be joined
Pressure: Because the applied pressure promotes a forging action, resistance welds can be produced at lower temperatures than welds made by other processes. If too little pressure is used, the contact resistance will be high and surface burning or pitting of the electrodes may result. If excessive pressure is applied, molten or softened metal may be expelled from between the faying surfaces, or the electrodes may indent the softened workpiece.
Current: the temperature achieved during resistance welding is primarily determined by the magnitude and duration of the welding current
Bulk resistances of metal increase as temperature rises
Contact resistances decrease as the metal softens and pressure improves the contact.
Spot-Welding Equipment: A variety of spot-welding equipment is available to meet the needs of production operations. For light-production work where complex current pressure cycles are not required, a simple rocker-arm machine is often used.
Spot-welding Guns have been instrumental in extending the process to such applications. The guns are connected to a stationary power supply and control unit by flexible air hoses, electrical cables, and water-cooling lines. They can be used in a manual fashion or installed on industrial robots where programmed positioning enables quality spot welds to be produced in a highly automated fashion.
Transguns: offer reduced power losses and enhanced process efficiency. However, if accurate positioning is required in an articulated system like an industrial robot, the added weight of the integral transformer may become a disadvantage.
Electrodes. Resistance spot-welding electrodes must conduct the welding current to the work, set the current density at the weld location, apply force, and help dissipate heat during the noncurrent portions of the welding cycle.
Resistance seam welding (RSEW) requires two distinctly different processes. In the first process, sheet metal segments are joined to produce gas- or liquid-tight vessels, such as gas tanks, mufflers, and simple heat exchangers. The weld is made between overlapping sheets of metal, and the seam is simply a series of overlapping spot welds,
The second type of resistance seam welding, known as resistance Butt welding, is used to produce butt welds between thicker metal plates. The electrical resistance of a butting metal is still used to generate heat, but high-frequency current (up to 450 kHz) is now employed.
PROJECTION WELDING In a mass-production operation, conventional spot welding is plagued by two significant limitations. Because the small electrodes provide both the high currents and the required pressure, the electrodes generally require frequent attention to maintain their geometry. In addition, the process is designed to produce only one spot weld at a time. When increased strength is required, multiple welds are often needed, and this means multiple operations. Projection welding (RPW) provides a means of overcoming these limitations.
Capacitor-discharge stud welding: is a variation of projection welding; a burst of current from an electrostatic storage system melts the projection and the pieces are pushed together, all within a time of 6 to 10 ms.
ADVANTAGES OF RESISTANCE WELDING
1. They are very rapid.
2. The equipment can often be fully automated.
3. They conserve material, because no filler metal, shielding gases, or flux is required.
4. There is minimal distortion of the parts being joined.
5. Skilled operators are not required.
6. Dissimilar metals can be easily joined.
7. A high degree of reliability and reproducibility can be achieved.
The limitations of resistance welding include:
1. The equipment has a high initial cost.
2. There are limitations to the thickness of material that can be joined (generally less than 6 mm, or14 in.), and the type of joints that can be made (mostly lap joints). Lap joints tend to add weight and material.
3. Access to both sides of the joint is usually required to apply the proper electrode force or pressure.
4. Skilled maintenance personnel are required to service the control equipment.
5. For some materials, the surfaces must receive special preparation prior to welding.

Chapter 34: Adhesive Bonding, Mechanical Fastening, and Joining of Nonmetals
ADHESIVE BONDING The ideal adhesive bonds to any material, needs no surface preparation, cures rapidly, and maintains a high bond strength under all operating conditions. It also does not exist. In adhesive bonding, a nonmetallic material is used to fill the gap and create a joint between two surfaces. The actual adhesives span a wide range of material types and forms, including thermoplastic resins, thermosetting resins, artificial elastomers, and even some ceramics.
Curing can be induced by the use of heat, radiation or light (photoinitiation), moisture, activators, catalysts, multiple-component reactions, or combinations thereof.
Structural adhesives are selected for their ability to effectively transmit load across the joint, and include epoxies, cyanoacrylates, anaerobics, acrylics, urethanes, silicones, high-temperature adhesives, and hot melts.
Epoxies. The thermosetting epoxies are the oldest, most common, and most diverse of the adhesive systems, and can be used to join most engineering materials, including metal, glass, and ceramic. They are strong, versatile adhesives that can be designed to offer high adhesion, good tensile and shear strength, toughness, high rigidity, creep resistance, easy curing with little shrinkage, good chemical resistance, and tolerance to elevated temperatures.
Cyanoacrylates. These are liquid monomers that polymerize when spread into a thin film between two surfaces. Trace amounts of moisture on the surfaces promote curing at amazing speeds, often in as little as 2 s. Thus, the cyanoacrylates offer a one-component adhesive system that cures at room temperature with no external impetus. Commonly known as superglues,
Anaerobics. These one-component, thermosetting, polyester acrylics remain liquid when exposed to air. When confined to small spaces and shut off from oxygen, as in a joint to be bonded or along the threads of an inserted fastener, the polymer becomes unstable. In the presence of iron or copper, it polymerizes into a bonding-type resin, without the need for elevated temperature.
Acrylics. The acrylic-based adhesives offer good strength, toughness, and versatility, and they are able to bond a variety of materials, including plastics, metals, ceramics, and composites and even oily or dirty surfaces. Most involve application systems where a catalyst primer (curing agent)
Urethanes. Urethane adhesives are a large and diverse family of polymers that are generally targeted for applications that involve temperatures below 65C (150F) and components that require great flexibility.
Silicones. The silicone thermosets cure from the moisture in the air or adsorbed moisture from the surfaces being joined. They form low-strength structural joints and are usually selected when considerable amounts of expansion and contraction are expected in the joint; flexibility is required (as in sheet metal parts); or good gasket, gap-filling, or sealing properties are necessary.
High-temperature adhesives. When strength must be retained at temperatures in excess of 300C (500F), high-temperature structural adhesives should be specified. These include epoxy phenolics, modified silicones or phenolics, polyamides, and some ceramics. High cost and long cure times are the major limitations for these adhesives, which see primary application in the aerospace industry.
Hot melt adhesives. can be used to bond dissimilar substrates, such as plastics, rubber, metals, ceramics, glass, wood, and fibrous materials like paper, fabric, and leather. They can produce permanent or temporary bonds, seal gaps, and plug holes. While generally not considered to be true structural adhesives, the hot melts are being used increasingly to transmit loads, especially in composite material assemblies. The joints can withstand exposure to vibration, shock, humidity, and numerous chemicals and offer the added features of sound deadening and vibration damping.
Hot melt disadvantage: The traditional hot melts do not cross-link or form three-dimensional network structures, but retain their linear thermoplastic structure throughout their history. As a result, they are characterized by poor strength, poor heat resistance, and the tendency to creep under load.
Reactive hot melts, overcomes many of these limitations, positioning the hot melts as true structural adhesives. These materials are applied as liquids at elevated temperature, cool to solids at room temperature, but then react (often with moisture) to form a cross-linked or three-dimensional network thermoset polymer with enhanced performance properties. They melt at lower temperatures than the conventional hot melts and can bond to many different surfaces.
Additives also play a large part in the success of industrial adhesives. They can impart or enhance properties like toughness, joint durability, moisture resistance, adhesion, and flame retardance.
Evaporative adhesives use an organic solvent or water base, coupled with vinyls, acrylics, phenolics, polyurethanes, or various types of rubbers. Some common evaporative adhesives are rubber cements and floor waxes.
Pressure-sensitive adhesives are usually based on various rubbers, compounded with additives to bond at room temperature with a brief application of pressure.
Delayed-tack adhesives are similar to the pressure sensitive systems but are nontacky until activated by exposure to heat. Once heated, they remain tacky for several minutes to a few days to permit use or assembly.
Conductive adhesives :While most adhesives are electrical and thermal insulators, conductive adhesives can be produced by incorporating selected fillers, such as silver, copper, aluminum, nickel, and gold in the form of flakes or powder.
Radiation-curing adhesives Still another group of commercial adhesives are those designed to cure by exposure to radiation, such as visible, infrared, or ultraviolet light; microwaves; or electron beams. These radiation-curing adhesives offer rapid conversion from liquid to solid at room temperature and a curing mechanism that occurs throughout, rather than progressing from exposed surfaces
Design considerations: 1. What materials are being joined? What are their surface finishes, hardnesses, and porosities? Will the thermal expansions or contractions be different? 2. How will the joined assembly be used? What type of joint is proposed, what will be the bond area, and what will be the applied stresses? How much strength is required? Will there be mechanical vibration, acoustical vibration, or impacts? 3. What temperatures might be required to affect the cure, and what temperatures might be encountered during service? Consideration should be given to the highest temperature, lowest temperature, rates of temperature change, frequency of change, duration of exposure to extremes, the properties required at the various conditions, and differential expansions or contractions. 4. Will there be subsequent exposure to solvents, water or humidity, fuels or oils, light, ultraviolet radiation, acid solutions, or general weathering? 5. What is the desired level of flexibility or stiffness? How much toughness is required? 6. Over what length of time is stability desired? What portion of this time will be under load? 7. Is appearance important? 8. How will the adhesive be applied? What equipment, labor, and skill are required? 9. Are their restrictions relating to storage or shelf life? Cure time? Disposal? Recyclability?
10. What will it cost?
Continuous-surface bonds, both of the adhering surfaces are relatively large and are of the same size and shape.
Core-to-face bonds have one adherend area that is very small compared to the other, like when the edges of lightweight honeycomb core structures are bonded to the face sheets
Advantage of Adhesive bonding Almost any material or combination of materials can be joined in a wide variety of sizes, shapes, and thicknesses. Heat-sensitive materials can be joined without damage, A substantial number cure at room temperature or slightly above and can provide adequate strength for many applications. Good load distribution and fatigue resistance are obtained, and stress concentrations are avoided. Are generally inexpensive and frequently weigh less than the fasteners. Surface preparation may be reduced; Tolerances are less critical
Disadvantage of Adhesive bonding: Adhesive bonding, Most industrial adhesives are not stable above 180 C degree, Some adhesives shrink significantly during curing. High-strength adhesives are often brittle. Surface preparation and cleanliness, adhesive preparation, and curing can be critical if good and consistent results are to be obtained. Assembly times may be greater than for alternative methods depending on the curing mechanism. It is difficult to determine the quality of an adhesive-bonded joint by traditional nondestructive techniques, Some adhesives contain objectionable chemicals or solvents or produce them upon curing. Many structural adhesives deteriorate under certain operating conditions. Adhesively bonded joints cannot be readily disassembled.
Weld bonding is for combining welding and adhesive bonding, they often combine in a way that compliments one another and cancels each other’s negative features.
Mechanical fastening includes a wide variety of techniques and fasteners designed to suit the individual requirements of a multitude of joints and assemblies.
Integral fasteners are formed areas of a component that interfere or interlock with other components of the assembly and are most commonly found in sheet metal products.
Discrete fasteners are separate pieces whose function is to join the primary components. These include bolts and nuts, screws, nails, rivets, quick-release fasteners, staples, and wire stitches.
Shrink and expansion fits form another major class of mechanical joining. Here, a dimensional change is introduced to one or both of the components by heating or cooling
Reason for Selection: They are easy to disassemble and reassemble. It can be used to join similar or different materials in a wide variety of sizes, shapes, and joint designs, Manufacturing cost is low. Installation does not adversely affect the base materials. Little or no surface preparation or cleaning is required.
MANUFACTURING CONCERN: Many mechanical fasteners require that the components contain aligned holes. Some fasteners, such as bolts coupled with nuts, require access to both sides of an assembly during joining. Stapling is a fast way of joining thin materials and does not require prior to hole making.
DESIGN AND SELECTION: Mechanical joints generally fail because of oversight or lack of control in one of four areas: (1) the design of the fastener itself and the manufacturing techniques used to make it, (2) the material from which the fastener is made, (3) joint design, or (4) the means and details of installation. Fasteners may have insufficient strength or corrosion resistance or may be subject to stress corrosion cracking or hydrogen embrittlement.
Many failures are the result of poor joint preparation or improper fastener installation. Nearly all fastener failures can be avoided by proper design and fastener selection.
Chapter 39: Manufacturing Automation
Automation: it was first used in the early 1950s to mean automatic handling of materials, particularly equipment used to unload and load stamping equipment. It has now become a general term referring to services performed, products manufactured and inspected, information handling, materials handling, and assembly—all done automatically. Automation as we know it today begins with the A(3) level. In recent years, this level has taken on two forms: hard automation and soft automation
A(1) LEVEL IS POWERED MACHINES If the first industrial revolution is tied to the machines that made cotton, the first factory revolution can be tied to the development of powered machine tools, dating from 1775, when the energetic,‘‘iron-mad’’John Wilkinson constructed a horizontal boring machine in England for machining internal cylindrical surfaces, such as piston-type pumps.
Another early machine tool was developed in 1794 by Henry Maudsley. It was anengine lathe with a practical slide tool rest.
A(2) LEVEL IS SINGLE-CYCLE AUTOMATICS The A(2) level of automation was clearly delineated when machine tools became singlecycle, self-feeding machines displaying dexterity. The A(2) level of machine can be loaded with a part and the cycle initiated by the worker. The machine completes the processing cycle and stops automatically.
Mechanization refers to the first and second orders of automaticity, which includes semiautomatic machines.
A(3) LEVEL IS REPEAT-CYCLE AUTOMATICS The A(3) level of automation requires that the machine be diligent; in other words, they should be repeat-cycle automatics. These machines have open-loop control, meaning that they do not have feedback and are controlled by eaither an internal fixed program, such as a cam, or are externally programmed with a tape, programmable logic controller (PLC), or computer.The A(3) level also includes robots, numerical control (NC) machines that have no feedback, and many special-purpose machine tools.
Transfer line, which is really an automated flow line. Workpieces are automatically transferred from station to station, from one machine to another. Operations are performed sequentially. In large transfer lines, to prevent entire machines from being shut down when one or two stations become inoperative, the individual machines are grouped in sections with 10 to 12 stations per section. Transfer machines are usually A(3)-level machines but can be A(4)- or even A(5)
Line balancing means that the processing time at each station must be the same, with the total nonproductive time for all other stations minimized.
A(4) LEVEL HAS FEEDBACK The A(4) level of automation required that human judgment be replaced by a capability in the machine to measure and compare results with desired position or size and adjustments to minimize errors. This is feedback, or closed-loop, control.
Computer numerical control (CNC)/ Numerical control (NC)/ machine control unit (MCU),
APT (automatically programmed tools), was introduced by MIT in 1959, Flexible manufacturing systems (FMSs)
The difference between an open-loop A(3) machine and a closed-loop A(4) machine, with feedback provided on the location of the table with respect to the axis of the spindle of the cutting tool. Three position control methods are commonly used: Transducer on table itself. Transducer (encoder) on the motor. Transducer (encoder) on the drive motor.
In CNC turning machines, Equation: Number of rough passes= (stock diameter –Minimum diameter+ Finish) / (Dept of cut x2)
Automatic tool changers, which require that the tools be precisely set to a given length prior to installation in the machines, permitted the merging of many machines into one machine.
The use of computer coding and classification systems, a group technology technique, to identify the initial family of parts around which the FMS is designed greatly improves the FMS design.
Expert systems try to infuse the software with the deductive decision-making capability of the human brain by having the system get smarter through experience. The software is designed to emulate human learning by configuring neural networks, where the computer relates inputs to outputs. Artificial intelligence (AI) carries this step higher by infecting the control software with programs that exhibit the ability to reason inductively.
Fuzzy logic control. The behavior of the process is described with linguistic terms. Fuzzy logic control statements replace closed-form mathematical models. The decision analysis element depends on a set of if–then statements rather than specific equations.
Robots, or steel-collared workers, are typically A(3)-, A(4)-, or A(5)-level machines. robot is a reprogrammable, multifunctional manipulator designed to handle material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.
Asimov’s three laws of robotics are the following:1. A robot may not injure a human being or, through inaction, allow a human being to be harmed. (Safety first.)2. A robot must obey orders given by human beings except when that conflicts with the First Law. (A robot must be programmable.3. A robot must protect its own existence unless that conflicts with the First or Second Law. (Reliability.)
Basic components of robot: Manipulators: the mechanical unit, often called the arm, that does the actual work of the robot. End effector: the hand or gripper portion of the robot, which attaches the end of the arm and performs the operations of the robot. Controller: the brains of the system that direct the movements of the manipulator. Teach pendants are often used to‘‘program’’the robot. The operator manipulates the arm and gripper and the robot remembers the taught path. Feedback devices: transducers that sense the positions of various linkages and joints and transmit this information to the controllers in either digital or analog form. Power supply electric, pneumatic, and hydraulic power supplies used to provide and regulate the energy needed for their manipulator’s actuators.
The A(3)-level robot, usually called a pick-and-place machine, is capable of performing only the simplest repeat-cycle movements, on a point-to-point basis,
Robot applications: Die cast, Press transfer, Material handling, Investment Casing, Material processing, Welding and cutting, Assembly, Painting.
ROBOT SELECTION Economic analysis: Can this robotic application be cost-justified?, Process capability: Can this robot do the job—is it accurate and precise enough?,Changing product designs: Can this robot handle new product designs?, Changing existing machine. Doing simple, hazardous, harmful, or fatiguing jobs first: Is this a good application for a robot?. Does the supplier have a training program? Will the supplier help during initial installation?
Computer-integrated manufacturing (CIM). an integrated system that encompasses all the activities in the production system, from the planning and design of a product through the manufacturing system, including control.
Computer-aided design (CAD) and computer-aided manufacturing (CAM). CAM is a computer-aided process planning (CAPP) module, which acts as the interface between CAD and CAM.
Capacity planning is concerned with determining what labor and equipment capacity is required to meet the current master production schedule as well as the longterm future production needs of the firm. Capacity planning is typically performed in terms of labor- and/or machine-hours available.
Chapter 40: Numerical Control (NC) and the A(4) Level of Automation
The first numerically controlled (NC) machine tool was developed in 1952 at the Massachusetts Institute of Technology (MIT).
NC uses a processing language to control the movement of the cutting tool or workpiece or both. The programs contain information about the machine tool and cutting-tool geometry, the part dimensions (from rough to finish size), and the machining parameters (speeds and feeds and depth of cut). A side result of NC is the decrease in the non-chip-producing time of machine tools.
HOW CNC MACHINES WORK: NC and CNC machines can be subdivided into two types,
In point-to-point machines, the tool path is not controlled but tools can be moved in straight lines or parallel traverses at desired table feed rates, but only one axis drive is operated at a time.
Contouring or contouring path permits two or three axes to be controlled simultaneously, permitting two- or three-dimensional geometries to be generated.
Traditionally, NC machine tool has a machine control unit (MCU). The MCU is further divided into two elements: the data-processing unit (DPU) and the controlloops unit (CLU).
The DPU processes the coded data that are read from the tape or some other input medium that it gives to the CPU, specifically the position of each axis, its direction of motion feed, and its auxiliary-function control signals.
The CLU operates the drive mechanisms of the machine.
For most NC controls, the feedback signals are supplied by transducers actuated either by the feed screw or by the actual movement of the component.
Two basic types of digital transducers: One supplies incremental information and tells how much motion of the input shaft or table has occurred since the last time. The second type of digital information is absolute in character, with each pulse corresponding to a specific location of the machine components.

Some of the functions in programmable machines require feed forward or preset loops. The machine must know in advance the rough dimensions of a casting or a forging so that it can determine how many roughing cuts are needed prior to the finishing cut. Common machining routines such as pocket milling or peck drilling have been programmed into many CNC machines. These are called canned cycles. To ensure accurate machining of a workpiece on a CNC machine, the control system has to know certain dimensions of the tools. These tool dimensions are referenced to a fixed setting point on the tool holder.
Part Programing: The zero reference point is the lower left-hand corner of the part.
Part program. The program (1) defines the sequence of operations required to fabricate the part; (2) gives the x, y, and z coordinate positions of the operations; (3) specifies the spindle traverse that determines the depth of the cut, the spindle speed, and the feed rate; and (4) determines whether the same tool can continue the next operation or whether a tool change is required.
The verification step can use the computer monitor, which simulates the part being made by tracing all the tool work paths as they would occur on the machine tool.
Four basic types of tape format have been used for NC input to communicate dimensional and no dimensional information: fixed-sequential format, block-address format, tab-sequential format, and word-address format.
Interpolation and cutter offset in numerical control :In milling machines, the centerline of the cutter is offset from the desired surface by the radius of the cutter. The path that the cutter needs to take to generate the desired geometry is not simply the perimeter or profile of the part.
Basic Interpolation: For numerically controlled machine tools, the program to control the relative tool/work motions is expressed by a sequence of numbers. In addition, the numerical program also contains other commands to control spindle speeds, tool changes, coolant cycles, and other tasks.
ADAPTIVE CONTROL: A(5) LEVEL Adaptive control (A/C, can deal with the problems caused by variations in the size of the uncut work piece, which may be a casting or a forging.
Thermal error, caused by the thermal expansion of machine elements, is not uniform and is normally the greatest source of machine error. Methods used to remove heat from a machine include cutting fluids, locating drive motors away from the center of a machine, reducing friction from the ways and bearings, and spray cooling control element of the machine.
The modern lathe is called a turning center and has CNC control and tools mounted in turrets on slanted beds. The tailstock has been replaced by a live, powered spindle and chuck.
Other NC machine: NC turret punches with X-Y control on the table, CNC wire EDM machines, laser and water-jet abrasive machining, flame cutters, and many other machines are readily available.
Probes on CNC machines can greatly improve the process capability of the machine tool. There is a big difference between the claimed program resolution for an NC machine and the accuracy and precision of the actual parts.