Mba ebooks ! Edhole

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Mba ebooks ! Edhole

  1. 1. EDUCATION HOLE PRESENTS Basic Manufacturing Processes Unit-III
  2. 2. Machining and Welding Operations and their Applications..................................................... 2 Machining........................................................................................................................................2 Basic principles of Lathe-machine ....................................................................................................3 Operations.......................................................................................................................................4 Operations of Shaper-Planer ................................................................................................... 5 Drilling machines .............................................................................................................................5 Milling machines ..................................................................................................................................................5 Welding ...........................................................................................................................................6 1. Gas welding......................................................................................................................................................6 2. Arc welding.......................................................................................................................................................6 3. Resistance welding...........................................................................................................................................6 4. Thermit welding ...............................................................................................................................................7 5. Solid state welding ...........................................................................................................................................7 6. New welding processes....................................................................................................................................7 Electric-Arc welding .........................................................................................................................7 Resistance welding...............................................................................................................................................8 Flames and their applications.................................................................................................. 8 Typical Flame Cutting...........................................................................................................................................8 Cold Machining ....................................................................................................................................................8 Cogmatic Flame Machining Technology ..............................................................................................................9 Soldering ..............................................................................................................................................................9 Applications..........................................................................................................................................................9 Brazing processes .......................................................................................................................... 10 Use of Brazing processes................................................................................................................ 10 Machining and Welding Operations and their Applications Machining Machining is any of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process. The many processes that have this common theme, controlled material removal, are today collectively known as subtractive manufacturing, in distinction from processes of controlled material addition, which are known as
  3. 3. additive manufacturing. Exactly what the "controlled" part of the definition implies can vary, but it almost always implies the use of machine tools (in addition to just power tools and hand tools). The precise meaning of the term machining has evolved over the past one and a half centuries as technology has advanced. In the 18th century, the word machinist simply meant a person who built or repaired machines. This person's work was done mostly by hand, using processes such as the carving of wood and the hand-forging and hand-filing of metal. At the time, millwrights and builders of new kinds of engines (meaning, more or less, machines of any kind), such as James Watt or John Wilkinson, would fit the definition. The noun machine tool and the verb to machine (machined, machining) did not yet exist. Around the middle of the 19th century, the latter words were coined as the concepts that they described evolved into widespread existence. Therefore, during the Machine Age, machining referred to (what we today might call) the "traditional" machining processes, such as turning, boring, drilling, milling, broaching, sawing, shaping, planning, reaming, and tapping.[1] In these "traditional" or "conventional" machining processes, machine tools, such as lathes, milling machines, drill presses, or others, are used with a sharp cutting tool to remove material to achieve a desired geometry. Since the advent of new technologies such as electrical discharge machining, electrochemical machining, electron beam machining, photochemical machining, and ultrasonic machining, the retronym "conventional machining" can be used to differentiate those classic technologies from the newer ones. In current usage, the term "machining" without qualification usually implies the traditional machining processes. Machining is a part of the manufacture of many metal products, but it can also be used on materials such as wood, plastic, ceramic, and composites. A person who specializes in machining is called a machinist. A room, building, or company where machining is done is called a machine shop. Machining can be a business, a hobby, or both.[4] Much of modern day machining is carried out by computer numerical control (CNC), in which computers are used to control the movement and operation of the mills, lathes, and other cutting machines. Basic principles of Lathe-machine 1. Bed: The bed is a heavy, rugged casting in which are mounted the working parts of the lathe. It carries the headstock and tail stock for supporting the workpiece and provides a base for the movement of carriage assembly which carries the tool. 2. Legs: The legs carry the entire load of machine and are firmly secured to floor by foundation bolts. 3. Headstock: The headstock is clamped on the left hand side of the bed and it serves as housing for the driving pulleys, back gears, headstock spindle, live centre and the feed reverse gear. The
  4. 4. headstock spindle is a hollow cylindrical shaft that provides a drive from the motor to work holding devices. 4. Gear Box: The quick-change gear-box is placed below the headstock and contains a number of different sized gears. 5. Carriage: The carriage is located between the headstock and tailstock and serves the purpose of supporting, guiding and feeding the tool against the job during operation. The main parts of carriage are: a). The saddle is an H-shaped casting mounted on the top of lathe ways. It provides support to cross-slide, compound rest and tool post. b).The cross slide is mounted on the top of saddle, and it provides a mounted or automatic cross movement for the cutting tool. c).The compound rest is fitted on the top of cross slide and is used to support the tool post and the cutting tool. d).The tool post is mounted on the compound rest, and it rigidly clamps the cutting tool or tool holder at the proper height relative to the work centre line. e).The apron is fastened to the saddle and it houses the gears, clutches and levers required to move the carriage or cross slide. The engagement of split nut lever and the automatic feed lever at the same time is prevented she carriage along the lathe bed. 6. Tailstock: The tailstock is a movable casting located opposite the headstock on the ways of the bed. The tailstock can slide along the bed to accommodate different lengths of workpiece between the centers. A tailstock clamp is provided to lock the tailstock at any desired position. The tailstock spindle has an internal taper to hold the dead centre and the tapered shank tools such as reamers and drills. Operations 1. Plain Turning and Step Turning 2. Facing 3. Parting 4. Drilling
  5. 5. 5. Reaming 6. Boring 7. Knurling 8. Grooving 9. Threading 10. Forming Operations of Shaper-Planer Shaping and planning operations involve the machining of flat surfaces, grooves, shoulders, T- slots, and angular surfaces with single-point tools. The largest shapers have a 36-inch cutting stroke and can machine parts up to 36 inches long. The cutting tool on the shaper oscillates, cutting on the forward stroke, with the work piece feeding automatically toward the tool during each return stroke. Planning machines perform the same operations as shapers but can machine longer work pieces. Some players can machine parts up to 50 feet long. The work piece is mounted on a reciprocating table that moves the work piece beneath a cutting tool. This tool, which remains stationary during the cutting stroke, automatically feeds into the workpiece after each cutting stroke. Drilling machines Drilling machines, also called drill presses, cut holes in metal with a twist drill. They also use a variety of other cutting tools to perform the following basic hole-machining operations: (1) reaming, (2) boring, (3) counterboring, (4) countersinking, and (5) tapping internal threads with the use of a tapping attachment. Milling machines A milling machine cuts metal as the workpiece is fed against a rotating cutting tool called a milling cutter. Cutters of many shapes and sizes are available for a wide variety of milling operations. Milling machines cut flat surfaces, grooves, shoulders, inclined surfaces, dovetails, and T-slots. Various form-tooth cutters are used for cutting concave forms and convex grooves, for rounding corners, and for cutting gear teeth.
  6. 6. Welding Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the work pieces to form a bond between them, without melting the work pieces. Classification of welding processes Modern methods of welding can be classified, depending on the state of the material during welding (plastic or molten state), as follows: 1. Plastic welding or pressure welding 2. Fusion welding or non pressure welding They can also be classified, depending on the source of heat, as follows: 1. Gas welding • Oxy acetylene or hydrogen welding • Air acetylene welding 2. Arc welding • Carbon arc welding • Metal arc welding • Gas metal arc welding (MIG) • Plasma arc welding • Electro slag welding • Submerged arc welding • Flux cored arc welding • Gas tungsten arc welding (TIG) • Atomic hydrogen arc welding 3. Resistance welding • Butt welding
  7. 7. • Resistance butt welding • Spot welding • Seam welding • Projection welding • Percussion welding 4. Thermit welding 5. Solid state welding • Friction welding • Ultrasonic welding • Diffusion welding • Explosive welding • Cold welding • Forge welding 6. New welding processes • Electron beam welding • Laser beam welding Gas-welding The most common gas welding process is oxyfuel welding, also known as oxyacetylene welding. It is one of the oldest and most versatile welding processes, but in recent years it has become less popular in industrial applications. It is still widely used for welding pipes and tubes, as well as repair work. The equipment is relatively inexpensive and simple, generally employing the combustion of acetylene in oxygen to produce a welding flame temperature of about 3100 °C. The flame, since it is less concentrated than an electric arc, causes slower weld cooling, which can lead to greater residual stresses and weld distortion, though it eases the welding of high alloy steels. A similar process, generally called oxyfuel cutting, is used to cut metals. Electric-Arc welding Arc welding is the most extensively used welding method. Here the source of heat is an electric arc which is produced by the electrode connected to the power supply. It is a fusion welding process.
  8. 8. • Carbon arc welding • Metal arc welding • Gas metal arc welding (MIG) • Plasma arc welding • Electro slag welding • Submerged arc welding • Flux cored arc welding • Gas tungsten arc welding (TIG) • Atomic hydrogen arc welding Resistance welding This is a group of welding processes in which the coalescence of metals is the result of the heat obtained from resistance offered by the work piece to the flow of electrical current. • Butt welding • Resistance butt welding • Spot welding • Seam welding • Projection welding • Percussion welding Flames and their applications Typical Flame Cutting General Application: Commercially available, for off-the-shelf machines • Poor tooth-to-tooth spacing • Surface blemishes, such as gouges, tears, slags and lumps commonly occur • Teeth are not square to the face of the plate Results: The poor quality of typical flame cut components often results in poor chain engagement; noisy operation; excessive wear; and uneven load patterns. Cold Machining General Application: Expensive, large scale equipment
  9. 9. • Excellent quality • Long lead times • High minimum orders • Cost-prohibitive rates • Often unrealistic for many OEMs Results: Great quality, but you’ll pay for it in time and cost (and potential costs due to wait times) Cogmatic Flame Machining Technology General Application: Proprietary machines that create accurate parts • Accurate tooth spacing throughout the sprocket circumference • Controlled cutting speed assures a smooth finish • Precise square tooth profile every time Results: Accurate chain engagement, reduced noise, even wear and proper loading patterns Soldering Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Soldering differs from welding in that soldering does not involve melting the work pieces. In brazing, the filler metal melts at a higher temperature, but the work piece metal does not melt. In the past, nearly all solders contained lead, but environmental concerns have increasingly dictated use of lead-free alloys for electronics and plumbing purposes. Applications Soldering is used in plumbing, electronics, and metalwork from flashing to jewelry. Soldering provides reasonably permanent but reversible connections between copper pipes in plumbing systems as well as joints in sheet metal objects such as food cans, roof flashing, rain gutters and automobile radiators. Jewelry components, machine tools and some refrigeration and plumbing components are often assembled and repaired by the higher temperature silver soldering process. Small mechanical parts are often soldered or brazed as well. Soldering is also used to join lead came and copper foil in stained glass work. It can also be used as a semi-permanent patch for a leak in a container or cooking vessel.
  10. 10. Electronic soldering connects electrical wiring and electronic components to printed circuit boards (PCBs). Brazing processes Brazing is a metal-joining process whereby a filler metal is heated above melting point and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquidus) temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal (known as wetting) and is then cooled to join the work pieces together. It is similar to soldering, except the temperatures used to melt the filler metal are higher for brazing. Use of Brazing processes Brazing has many advantages over other metal-joining techniques, such as welding. Since brazing does not melt the base metal of the joint, it allows much tighter control over tolerances and produces a clean joint without the need for secondary finishing. Additionally, dissimilar metals and non-metals (i.e. metalized ceramics) can be brazed. In general, brazing also produces less thermal distortion than welding due to the uniform heating of a brazed piece. Complex and multi-part assemblies can be brazed cost-effectively. Welded joints must sometimes be ground flush, a costly secondary operation that brazing does not require because it produces a clean joint. Another advantage is that the brazing can be coated or clad for protective purposes. Finally, brazing is easily adapted to mass production and it is easy to automate because the individual process parameters are less sensitive to variation

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