Fundamentals of Manufacturing Processes IT 208

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Fundamentals of Manufacturing Processes IT 208

• Lecture notes were obtained from
• http//www.engr.siu.edu/it/IT20208/
• for IT 208

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Fundamentals of Manufacturing Processes IT 208
Chris Healy, P.E.
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• The Definition of Manufacturing.
• Identify production tasks by the type of product

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Classification of Production Tasks

• Material removal any process by which a part or
  piece of a material is severed or separated from
  another section of the same material.
• Material addition by which a piece of stock can
  be increased in volume or weight
• Change of form methods by which the shape of a
  piece of material is altered.
• Change of condition when the internal structure
  of metal and other parts can be altered to
  provide the qualities required in the final
  product.
• Material joining method by which two or more
  parts are held together
• Finishing when a finish is applied that makes a
  product suitable for use for its intended purpose

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Determining The Proper Tool

• What are the physical properties of the material
  being cut, formed, or shaped, and what are the
  properties of the tools being used?
• Does the tool or process produce an object or
  part that meets all of the design specifications
  given in the plans?
• Does the tool or process selected have the
  precision required for the product?
• Does the tool or process selected meet the
  required production rate of the job?

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Determining The Proper Tool

• Is the tool or process economical? In other
  words, is the per-unit cost of the process low
  enough to do the job profitably?
• Does the selected tool or process meet the social
  or environmental requirements, and are the
  resulting environmental costs small enough to
  justify using the process?
• Will the tool or process be available when it is
  needed?
• Is a trained operator required for the process?
  If so, will one be available when needed?

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Properties of Materials

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• Competencies
• Define Stress, Strain, True Stress and
  Engineering Stress, Yield Strength, and
  Compression
• Calculate Stress, Strain, True Stress and
  Engineering Stress, Yield Strength, Safety Factor
  and Compression
• List and describe the 4 categories of chemical
  bonds.
• Define material fatigue and creep
• List materials used to produce iron leading to
  steel.

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STRUCTURE OF MATTER

• All properties of materials are a function of
  their structure. If the atomic structure,
  bonding structure, crystal structure, and the
  imperfections in the material are known, the
  properties of the material can be determined.
• Matter is composed of atoms, which are composed
  of proton, neutrons, and electrons.
• Atoms combine to form molecules, which are the
  smallest units of chemical compounds.
• The atoms are held together by chemical bonds.

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Categories of chemical bonds

• In chemical bonds, atoms can either transfer or
  share their valence electrons
• ionic In the extreme case where one or more
  atoms lose electrons and other atoms gain them in
  order to produce a noble gas electron
  configuration, the bond is called an ionic bond.
• covalent - Covalent chemical bonds involve the
  sharing of a pair of valence electrons by two
  atoms, in contrast to the transfer of electrons
  in ionic bonds. Such bonds lead to stable
  molecules if they share electrons in such a way
  as to create a noble gas configuration for each
  atom.
• metallic -
• van der waal -

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STATES OF MATTER

• Gaseous State individual atoms or molecules
  have little or not attraction to each other.
  They are in constant motion and are continuously
  bouncing off one other.
• Boiling Point The temperature at which gaseous
  particles begin to bond to each other. To
  continue into the liquid state the heat of
  vaporization must be removed or to move from
  liquid to gas the heat must be added.
• Liquid State having bonds of varying lengths
  relating to the viscosity of a material
• Solid State has a definite structure
• Melting point the temperature at which enough
  energy to break one bond of a crystal. All true
  solids have a definite melting point.

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NUCLEATION OF GRAINS

• The phenomenon when the temperature of molten
  material is lowered to the melting point, little
  crystals or nuclei are formed at many points in
  the liquid.
• After the grains have been nucleated and grown
  together to form a solid, the process of grain
  growth occurs. Slow cooling to room temperature
  allows for larger grains to form, while rapid
  cooling only allows for small grains to form.

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NUCLEATION OF GRAINS

• Atoms or particles align themselves into planes
  within each crystal, there is a uniform distance
  between particles. These plains can slide over
  each other, the more ductile the material
  becomes, the more ways slip can occur.
• A materials density, ductility, and malleability
  are a factor or crystalline structure resulting
  in planes for slip to occur.

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STRENGTH PROPERTIES

• Stress - defined as the load per unit cross
  section of area.
• Compression
• Torsional
• Tension forces pulling an object in opposite
  directions. If the load or force pulling on the
  material is divided by the cross-sectional area
  of the bar, the result is the tensile stress
  applied to the sample
• AREA
• Width x Height
• Pi r2
• Stress generally given in psi (english) or
  Pascal (metric)

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Problems

• If a tensile force of 500 lb is placed on a
  0.75-in. diameter bar, what is the stress on the
  bar?

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Problems

• If a tensile force of 500 lb is placed on a
  0.75-in. diameter bar, what is the stress on the
  bar?

1130 lb/in2
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Problems

• What is the tensile strength of a metal if a
  0.505 in.-diameter bar withstands a load of
  15,000 lb before breaking?

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Problems

• What is the tensile strength of a metal if a
  0.505 in.-diameter bar withstands a load of
  15,000 lb before breaking?

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Problems

• A cable in a motor hoist must lift a 700-lb
  engine. The steel cable is 0.375 in. in diameter.
  What is the stress in the cable?

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Problems

• A cable in a motor hoist must lift a 700-lb
  engine. The steel cable is 0.375 in. in diameter.
  What is the stress in the cable?

6338 lb/in2
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STRENGTH PROPERTIES
Strain - the elongation of a specimen per unit of
original length
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STRENGTH PROPERTIES

• Elastic limit - The maximum applied stress that
  metals and other materials can be stretched and
  still rebound in much the same manner as a rubber
  band - also called proportional limit.
• The rest of the stress-strain curve, to the right
  of the elastic limit, is the plastic region.
  (Figure 2.16 in text, pg 21.)

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STRENGTH PROPERTIES

• Tensile strength or ultimate strength is the
  maximum stress that a bar will withstand before
  failing and is shown as point T on the curve.
  (See Figure 2.16, pg 21)
• Rupture strength - or breaking strength is the
  stress at which at a bar breaks, point R on
  Figure 2-16.
• Yield strength - the engineering design strength
  of the material
• The point intersection determined by measuring a
  distance of 0.002 inch/inch on the strain axis,
  then drawing a straight line parallel to the
  straight-line portion of the curve. (Figure
  2-17).

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Problem
4. If a steel cable is rated to take 800 lb and
the steel has a yield strength of 90,000 psi,
what is the diameter of the cable? (Ignore safety
factor, which is defined on pg24.)
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Problem
4. If a steel cable is rated to take 800 lb and
the steel has a yield strength of 90,000 psi,
what is the diameter of the cable? (Ignore safety
factor, which is defined on pg24.)
D 0.11 in.
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Problem
5. If a tensile part in a machine is designed to
hold 25,000 lb and the part is made from a
material having yield strength of 75,000 psi,
what diameter must the part have?


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Problem
5. If a tensile part in a machine is designed to
hold 25,000 lb and the part is made from a
material having yield strength of 75,000 psi,
what diameter must the part have?


D.65
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STRENGTH PROPERTIES
Modulus of Elasticity (Youngs modulus) is the
change in stress divided by the change in strain
while the material is in the elastic region.
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STRENGTH PROPERTIES
Compression is loading a specimen by squeezing
the material. If a compressive force of 2200 lb
is applied to a concrete column having a diameter
of 6 in., what is the stress on the column?
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STRENGTH PROPERTIES
Compression is loading a specimen by squeezing
the material. If a compressive force of 2200 lb
is applied to a concrete column having a diameter
of 6 in., what is the stress on the column?
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STRENGTH PROPERTIES
Shear is defined as the application of opposing
forces, slightly offset to each other (Figure
2-21). Torsion is the twisting of an object
(Figure 2-23). Torque Length x Force Usually
expressed in Ft. lbs
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Problem
What force must be applied to the end of a 14-in.
pipe wrench if a torque of 75 ft-lb is needed?
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Problem

• What force must be applied to the end of a 14-in.
  pipe wrench if a torque of 75 ft-lb is needed?

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Problem
A shear force of 1800 lb is required to cut a bar
having a diameter of 0.400 in. What is the shear
strength of the material being cut?
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Problem
A shear force of 1800 lb is required to cut a bar
having a diameter of 0.400 in. What is the shear
strength of the material being cut?
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SURFACE PROPERTIES

• Hardness is a measure of a materials resistance
  to surface deformation.
• One of the most common is the Rockwell test.
• The Rockwell test makes use of three different
  indenters or points (Figure 2-28)
• 1/16-inch steel ball
• 1/8-inch ball, and
• black diamond conical or brale point.
• In reporting a Rockwell harness number, the scale
  must be stated along with the hardness value

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SURFACE PROPERTIES

• The B-scale is used for softer materials (such as
  aluminum, brass, and softer steels). It employs a
  hardened steel ball as the indenter and a 100kg
  weight to obtain a value expressed as "HRB".
• The C-scale, for harder materials, uses a diamond
  cone, known as a Brale indenter and a 150kg
  weight to obtain a value expressed as "HRC".

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SURFACE PROPERTIES

• Brinell Hardness (BHN). A second common hardness
  test used to test metals is the Brinell hardness
  test (Figure 2-30).
• In the Brinell test, a 10-millimetre
  case-hardened steel ball is driven into the
  surface of the metal by one of three standard
  loads 500, 1500, or 3000 kilograms. Once the
  ball is pushed into the material by the specified
  load, the diameter of the indentation left in the
  metal (Figure 2-31) measured in millimeters

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SURFACE PROPERTIES

• Impact
• As opposed to steady-state test (tensile
  strength, compressive strength, shear strength,
  and torsion strength) Impact strength is
  determined by a sudden blow to the material.
• The speed at which the load is applied is known
  as the strain rate and is measured in inches per
  minute, meters per minute, millimeters per second
  or similar units.
• The impact strength of a metal can be determined
  by using one of three methods Izod, Charpy,
  Tensile impact.
• Impact testing is discussed on pgs 34 through 37.

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SURFACE PROPERTIES

• Creep
• The elongation caused by the steady and
  continuous application of a load over a long
  period of time. The load is applied continuously
  for many months to many years. The amount of
  creep depends on the elasticity of the material,
  its yield strength, the stress applied, and
  temperature.
• Fatigue
• The failure of a material due to cyclic or
  repeated stresses.

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Properties of Material (Iron and Steel)

• Ferrous (Contains Iron) Non-Ferrous (No Iron)
• Raw materials used to produce iron
• Iron ore - mined in various forms (65 pure iron)
  
• Limestone - acts as a flux to help remove
  impurities
• Coke - specialized coal (burns hotter than coal)

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Properties of Material

• Blast Furnace
• Materials brought to top of furnace
• Heated air at 1100 oF is blown into furnace
• Pig iron drained is off into carts
• Slag is tapped off of the other side

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TYPES OF STEEL MAKING FURNACES

• Used to burn the carbon out of the steel
• Open Hearth Hot air blown over the top of the
  steel (ceased in the 1940s)
• Bessemer hot air blown from the bottom of the
  crucible (used between 1890-1950)
• Electric requires a tremendous amount of power
• Continuous arc between electrode and metal
• Electrodes made of carbon
• Produce 60 to 90 ton of very clean steel/day
• Basic Oxygen Furnace (BOF)
• Uses pure O2 at 180 psi
• Refine 250 tons/hour

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Properties of Material
Alloying element - 10 XX - Carbon Content by
weight (points of carbon) Low Carbon Steel -
lt 0.25 carbon Medium Carbon Steel -
0.25 to 0.55 C High Carbon Steel - gt 0.55
carbon
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Properties of Material

• Stainless Steels
• Characterized by corrosion resistance, high
  strength, ductility, and high chromium content
• Tool and Die Steels
• High strength, impact toughness, and wear
  resistance at room and elevated temperatures
• Non-ferrous metals (no iron as base metal)
• Corrosion resistance, high thermal and electrical
  conductivity, low density ease of fabrication

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Properties of Material

• Aluminum and aluminum alloys (most abundant
  metallic element)
• High strength to weight ratio, resistance to
  corrosion, electrical/thermal conductivity, ease
  of formability
• Uses containers (cans), transportation
  (aerospace aircraft, busses, and marine crafts),
  electrical applications (economical and
  nonmagnetic conductor)
• About 79 percent of Boeing 757 consists of
  aluminum
• Can be heat treated for different properties

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Properties of Material

• Magnesium and magnesium alloys (third most
  abundant metallic element)
• lightest engineering metal
• has good vibration damping character
• not sufficiently strong in its pure form so must
  be alloyed
• Copper and Copper alloys
• Among best conductors of elect/heat
• Usually used where electrical and corrosion
  resistant properties are needed

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Properties of Material

• Brass - (Copper and Zinc) one of the earliest
  developed alloys
• Bronze - (Copper and tin)
• For electrical conductors refined to 99.95
  percent purity
• Nickel and Nickel alloys
• Major alloying element (strength, toughness,
  corrosion resistance)
• Food handling equipment
• Chemical processing equipment
• It is magnetic (used in solenoids for this
  reason, also electromagnetic)

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Measurements in Manufacturing
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Measurements in Manufacturing

• Frequently mistakes are made using incorrect
  methods, faulty judgments, incorrect
  calculations, lack of attention to details,
  carelessness, etc.
• Limitations of measuring instruments may also
  induce errors.

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Measurements in Manufacturing

• Length (inch, feet, yard, mile, or millimeter,
  centimeter, meter, kilometer)
• 1 inch 25.4 centimeters
• Volume (pint, quart, gallon or liter,)
• 1 Liter 1000 cm3 1 Quart 0.946 L
• Force (pound lb or Newton N)
• Pounds per square inch (psi)
• Newton per square millimeter
• Converting force (F) units to mass (M)
• F ma where m mass (Lb or Kg) and a
  acceleration (ft/s2 or m/s2)
• 1 Kg mass 2.20446 Lbs or 1 Lb 0.4536 Kg

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Measurements in Manufacturing

• Products are tested as they leave assembly line
• The process of testing product as they leave
  assembly line is called quality control
• Inspecting and testing product is called quality
  assurance

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Mechanical Methods of Material Removal

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• Competencies
• Identify the unique characteristics associated
  with powered mechanical methods of material
  removal
• Calculate the optimum feeds and speeds for
  milling, drilling and turning
• List and define the two types of milling machine
  configurations
• List the 3 major functions of cutting

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POWERED MECHANICAL METHOD OF MATERIAL REMOVAL

• Two most versatile
• Lathe to make cylindrical, conical, spherical,
  treaded shapes
• Vertical mill prismatic parts with contours
  with various shapes
• Lathe Components
• Bed- supports all other major components
• Carriage- slides along the ways and consists of
  an assembly cross-slide, tool post, and apron.
• Headstock- fixed to the bed and has motors,
  pulleys, and v-belts that supply power to the
  spindle (hollow) (work holding device attached to
  the spindle)
• Tailstock- can slide along the ways and can be
  clamped down. Supports the part on the rear end
  with Live or Dead center6.
• Feed rod and lead screw- used to provide power to
  the carriage to feed it along or across the work
  piece.

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MATERIAL REMOVAL

• 4 Considerations that determine how fast to run a
  lathe
• Workpiece material
• Tool diameter
• Diameter of the work piece
• Depth of cut

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MATERIAL REMOVAL

• Cutting fluids- provide 3 major functions
• Lubrication
• Cooling
• Chip removal

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MATERIAL REMOVAL

• Milling- A process that is capable of producing
  a variety of configurations using a multitooth
  tool, turns the tool and holds the workpiece to
  provide the cutting action
• Types of Milling Machines
• Horizontal- the spindle is placed horizontal
  (used for heavier cutting)
• Vertical- the spindle is placed vertical (the
  most common type of milling machine)

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MATERIAL REMOVAL

• Shaping and Planning - Cutting blades rotate
  while the material is passed through them.
• Routing - Uses specially shaped cutting tool to
  remove material in a defined geometry.
• Broaching - Specific file geometry is used to
  duplicate the profile of the broach inside a
  hole.
• Drilling and Boring
• Drilling - Stock is held stationary and the drill
  is rotated
• Boring - Cutting tool is stationary and the
  material rotated

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MATERIAL REMOVAL

• Reaming and Honing
• Reamer- Similar to a drill, but has straight
  cutting edges and is used for finishing a hole to
  very close tolerances.
• Hones - Small grindstone used to move material
  and smooth out the final surface.

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MATERIAL REMOVAL

• Sawing
• Advantages Quick and cheap method of material
  removal
• Disadvantages Leaves rough surface on both
  sides of the cut.
• Saw Set Making the kerf wider than the blade
  backing so that the blade will not bind in the
  kerf.
• Blade selection Harder the material, the finer
  and closer the teeth. Steel 14-30 t.p.i.,
  Aluminum 8-12 t.p.i.
• Circular Saws, Jig Saws, Hack Saws, Band, Saws,
  Chain Saws.
• Abrasive Saws- used to cut (grind) extremely hard
  materials cannot be used to cut soft materials
  because it will load the blade.

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MATERIAL REMOVAL

• Shearing and Punching
• Shearing- Process of slitting flat stock up to
  ½ in thickness
• Punching- Shearing any shaped hole in flat stock.
  
• Grinding Removal of material by abrasion.
• Dressing a wheel is a process of using a
  diamond to remove the outer layer of a wheel, so
  that it becomes round (true) and the ends square.
  
• Grit Size refers to the size of grit that will
  pass through the number of openings per linear
  inch in a sieve. (i.e. 100 grit sand paper)

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MATERIAL REMOVAL

• Cutting Tool Shapes (see fig. 4-50)
• Side, back, and end rake angles are determined by
  the materials being cut and the type of cut being
  made. Hard materials require very little side or
  back rake angle.
• High Speed Steel (HSS) best choice for roughing
  purposes. They are inexpensive, can be easily
  resharpened, and are not extremely brittle. The
  HSS tools will take considerable shock. Their
  drawback is that they dull faster, especially in
  the cutting of harder metals.

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MATERIAL REMOVAL

• Carbide Carbide tips will cut harder steels,
  but they are brittle and should not be used for
  roughing purposes. Carbide-tipped tools can
  produce closer tolerances and better finishes
  than the HSS tools.
• Ceramic tools - are not affected by heat, and can
  be operated at extremely high revolutions per
  minute. However, these tools are similar to
  glass in brittleness. Ceramic tools are
  generally used only for the final, very light cut
  on very hard steels.

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MATERIAL REMOVAL

• Feeds Speeds
• Cutting Speed is the velocity of the surface of
  a workpiece as it passes the cutting tool.
• Speed (SFPM) given in surface feet per minute
  (SFPM).
• Spindle Speed is the rotational speed in
  revolutions per minute at which the lathe,
  milling machine, saw, grinder, or drill press is
  running.
• Feed - the rate of advance of the cutting tool
  per revolution.
• Depth of Cut is the distance to which the
  cutting tool enters the workpiece.

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MATERIAL REMOVAL

• Determining Optimum production
• where N spindle speed (rpm), CS recommended
  SFPM, and D diameter (ft)
• Using recommended Cutting Speeds and Feeds Table
  4.2 p.105

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Problem
A 4-in.-diameter piece of mild, low-carbon steel
is to be turned on a lathe using a carbide
cutting tool. What is the optimum speed of the
lathe? (From table 4.2 on pg. 105, Cs 550
SFPM)
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Problem
A 4-in.-diameter piece of mild, low-carbon steel
is to be turned on a lathe using a carbide
cutting tool. What is the optimum speed of the
lathe? From table 4.2, Cs 550 sfpm
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Problem
A 0.5-in.-diameter hole is to be drilled in a
piece of 316 stainless steel with a HSS drill. At
what rpm should the drill press be set? From
table 4.2, Cs 100 SFPM
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Problem
A 0.5-in.-diameter hole is to be drilled in a
piece of 316 stainless steel with a HSS drill. At
what rpm should the drill press be set? From
table 4.2 on pg. 105, Cs 100 SFPM
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Problem
A lathe has a maximum speed of 1500 rpm. Could it
be run at this maximum rpm using a carbide-tipped
tool to cut a 2-in.-diameter piece of aluminum?

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Problem
A lathe has a maximum speed of 1500 rpm. Could it
be run at this maximum rpm using a carbide-tipped
tool to cut a 2-in.-diameter piece of aluminum?

Yes, Cs 1200 sfpm, Maximum recommended speed is
2292 RPM
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Electrical Methods of Material Removal

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• Competencies
• Identify the general operating principles of EDM

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Electrical Methods of Material Removal

• Electrical Discharge Machining (EDM) - The
  process of removing metal with an electric arc.
• The workpiece and cathode (shape of tool/
  impression) are submerged in a dielectric fluid
• Voltage is applied (DC 300V)
• Material is arced away and flushed out by the
  dielectric fluid
• Electrodes are usually made of graphite
• The material removal rate is influenced by the
  melting temperature of the workpiece material and
  is faster for materials of lower melting
  temperature.

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Electrical Methods of Material Removal

• EDM is best suited for materials whose parts are
  
• Made of very hard (conducting) materials and
• To have a high precision (or low surface
  roughness)
• At a low production rate
• To have some strange shapes which would be
  difficult to machine by conventional techniques

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Electrical Methods of Material Removal

• RAM EDM Plunge EDM Die Sinking EDM - complex
  cavities are formed by penetration of shaped
  electrode into the part.
• Used to make dies for forging or punching
  operations.
• Wire EDM- Uses a wire to erode the sides of the
  hole to form two external surfaces, which can
  have an elaborate shape.
• wire electrode is of brass, copper, tungsten or
  molybdenum

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Chemical Methods of Material Removal
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Chemical Methods of Material Removal

• Acids dissolve metal
• Alcohols and Acetates dissolve certain plastics
• Water dissolves sugar and table salts

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Chemical Methods of Material Removal

• Chemical and electrochemical machining allow
  parts to be removed that may be difficult by
  other processes
• Chemical machining can reach areas not accessible
• Electrochemical are faster than chemical
  machining
• Both chemical and electrochemical pose
  environmental problems
• Disposal process is expensive
• Serious environmental risks/expenses associated
  with handling

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