MANUFACTURING

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MANUFACTURING
(Lecture 2)
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Manufacturing Processes

• Processes add value to materials
• A process involves a number of steps or
  operations
• Four basic processes applied on production
  materials are forming, material removal, assembly
  (or joining) and conditioning
• Forming operations change the geometry of the
  starting material without cutting it
• Material removal or separating processes remove a
  part of the starting material using a tool to get
  the desired geometry
• Combining processes join two materials or deposit
  material onto the exterior surface of the
  starting material
• Conditioning processes add value to the starting
  material by improving its internal and physical
  properties

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Forming Processes

• Casting
• A material in a liquid or semisolid form is
  poured or forced to flow into a mold cavity and
  allowed to solidify, thus taking the solid shape
  of the cavity
• The process can be applied on metals, ceramics
  and plastics
• The term casting is commonly used for metals
• The term molding is used for plastics
• Examples of molds cake-pan, an ice-cube-tray or
  the footprints on a beach
• Types of castings sand casting and die casting
• Sand casting pouring molten metal into a sand
  mold, breaking up the mold to remove the casting
• Sand casting requires a pattern a full sized
  model of the part
• Die casting is a permanent-mold-casting molten
  metal is injected into the mold cavity under high
  pressure
• Molds for die casting are named as dies

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Forming Processes
Casting with a two-piece mold

• Pressing
• Pressing is commonly used for majority of sheet
  metal parts of an automobile
• A measured amount of material is poured into a
  mold. A plunger with its own shape is lowered to
  force the material to spread out and fill the
  mold
• The material is forced into the shape of the mold
  at the bottom and the shape of the plunger at the
  top
• Mechanical or hydraulic presses are used
• The plunger and the base of a forming die
  transform the sheet metal into the required shape
  drawing fuel tank of a motorbike

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Forming Processes

• Pressing
• Rolling is a type of pressing thickness of the
  starting material is reduced by compressive
  forces exerted by two opposing rolls
• Great pressure can make the powdered metal into a
  solid. The material is then heated to make the
  object hard sintering

Rolling of a slab
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Forming Processes

• Forging
• The oldest metal forming operation
• Work part is heated and compressed using either
  impact or gradual pressure part
• Forging machine applying an impact load forging
  hammer
• Forging machine applying gradual pressure
  forging press
• Examples high-strength components for
  automotive and aircrafts like engine crank shafts
  and connecting rods, gears, aircraft structural
  components, and jet engine turbine parts

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Forming Processes

• Extrusion
• A compression process in which the work metal is
  forced to flow through a die opening, thereby
  taking the shape of the opening as its own
  cross-section
• Toothpaste is a very good example of the process
• Different shapes are possible especially with hot
  extrusion
• The end product does not require much more
  shaping and machining

Extruding a red hot metal
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Forming Processes

• Blow Molding
• Air pressure is used to inflate soft plastic into
  a mold cavity
• One-piece hollow plastic parts with thin walls
  are possible, such as bottles and similar
  containers
• The technology is borrowed from the glass
  industry with which plastics compete in the
  disposable or recyclable bottle market

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Material Removal Processes

• Operations that remove excess material from the
  starting workpiece to get the desired geometry
• Use of knives and scissors is a common example
• Important processes shearing, sawing and
  machining operations such as turning, drilling
  and milling, shaping and planing and grinding
• Nontraditional processes lasers, filters,
  magnets and electrochemical energy
• Sawing
• A narrow slit is cut into the workpiece by a tool
  consisting of a series of narrowly spaced teeth
• Most sawing operations work is held stationary
  and saw blade is moved relative to it
• Types hacksawing and bandsawing
• Hacksaw blade thin straight tool with cutting
  teeth on one edge
• Bandsaw blade endless flexible loop with teeth
  on one edge pulley-like drive mechanism

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Material Removal Processes

• Sawing

A power hacksaw
A vertical bandsaw
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Material Removal Processes

• Shearing
• Metal cutting operation along a straight line
  between two cutting edges similar to using a
  pair of scissors
• Typically used to cut large sheets into smaller
  sections for subsequent pressworking operations
• Other similar processes are blanking and punching

Shearing
Blanking and punching
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Material Removal Processes

• Turning
• Cutting tool with a single cutting edge
  rotating workpiece to generate a cylindrical
  shape
• Turning is commonly performed using a lathe
• Drilling
• Used to create a round hole
• A rotating tool that has two cutting edges
• The holes can be made from 1/10,000 of an inch to
  3½ inches
• Milling
• Rotating tool with multiple cutting edges plane
  or straight surface
• Types vertical milling and horizontal or face
  milling

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Material Removal Processes

• Shaping and Planing
• Single-point cutting tool moved linearly relative
  to the workpiece
• Creating a straight, flat surface
• Shaping tool provides the speed motion and the
  workpiece remains static
• Planing workpiece provides the speed motion
  while the tool remains motionless.
• Grinding
• Used to provide surface finish and the uniform
  thickness of the workpiece
• Abrasive particles are used sand paper or
  grinding wheel
• Abrasives very small crushed particles of hard
  materials like aluminum oxide and silicon carbide
• Grinding wheel usually disk-shaped, precisely
  balanced for high rotational speeds
• Common forms of grinding polishing, buffing and
  the use of toothpaste

Grinding tools
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Assembly Processes

• Two or more separate parts are joined to form a
  new entity
• Components are connected permanently or semi
  permanently
• Types mechanical methods, thermal methods and
  adhesive bonding
• Mechanical Assembly
• Various fastening methods use of hardware
  components, called fasteners
• Products using mechanical assembly automobiles,
  large and small appliances, telephones,
  furniture, utensils and wearing apparels
• Categories nails, threaded fasteners and rivets
  
• Mechanical assembly is often preferred for its
  ease of assembly and disassembly
• Nails are commonly used for wood finishing
  nails, box nails and common nails