Ion implantation: the ions are accelerated in a vacuum to such an extent that they penetrate the sub

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• Ion implantation the ions are accelerated in a
  vacuum to such an extent that they penetrate the
  substrate to a depth of a few mm.
• Diffusion coating a process in which an
  alloying element is diffused into the surface of
  the substrate, thus altering its properties.
  (carburizing, nitriding, boronizing)
• Electroplating
• The workpiece (cathode) is plated with a
  different metal (anode) while both are suspended
  in a bath containing a water-base electrolyte
  solution.
• Electroforming is a variation of electroplating.
  Metal is elctrodeposited on a mandrel, which is
  then removed.

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• Anodizing
• the workpiece is the anode in an electrolytic
  cell immersed in an acid bath, resulting in
  chemical adsorption of oxygen from the bath. The
  workpiece surface is covered with a hard and
  porous oxide layer.
• Applications aluminum furniture and utensils,
  architectural shapes, automobile trim, picture
  frames, keys, sporting goods
• Diamond coating of metals, glass, ceramics, and
  plastics, uses chemical and plasma-assisted vapor
  deposition process and ion beam enhanced
  deposition techniques.
• Production of free-standing diamond films on the
  order of 1 mm thick and up to 5 in diameter
• properties of diamond hardness, wear
  resistance, high thermal conductivity, and
  transparency to ultraviolet light and microwave
  frequencies
• Used for scratchproof windows, sunglasses,
  cutting tools, calipers, surgical knives, razors,
  electronic and infrared heat sinkers and sensors,
  light emitting diodes, turbine blades, and fuel
  injection nozzles.

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• Cleaning surfaces
• Cleaning involves removal of solid, semisolid, or
  liquid contaminants from a surface.
• Two types of cleaning methods
• Mechanical - physically disturbing the
  contaminants, as with wire or fiber brushing, dry
  or wet abrasive blasting, tumbling, and stream
  jet.
• Chemical - usually involves the removal of oil
  and grease from surfaces. It consists of one or
  more of the following processes
• solution - the soil dissolves in the cleaning
  solution
• saponification - a chemical reaction that
  converts animal or vegetable oils into a soap
  that is soluble in water
• emulsification - the cleaning solution reacts
  with the soil or lubricant deposits and forms an
  emulsion. The soil and the emulsifier then
  become suspended in the emulsion

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• dispersion - the concentration of soil on the
  surface is decreased by surface-active materials
  in the cleaning solution
• aggregation - lubricants are removed from the
  surface by various agents in the cleaner and
  collect as large dirt particles.
• Some common cleaning fluids are used in
  conjunction with electrochemical processes for
  more effective cleaning. These fluids include
  alkaline solutions, emulsions, solvents, hot
  vapors, acids, salts, and organic compound
  mixtures.
• Cleaning discrete parts having complex shapes can
  be difficult. Design engineers should be aware
  of this difficulty and provide alternative
  designs, such as avoiding deep blind holes or
  making several smaller components instead of one
  large component that may be difficult to clean,
  and provide appropriate drain holes in the part
  to be cleaned.

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Engineered Metrology and Instrumentation

• Engineering metrology is defined as the
  measurement of dimensions
• postprocess inspection
• in-process, online, real-time inspection
• Dimensional tolerances - the permissible
  variation in the dimensions of a part

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• Instruments
• Line-graduated (marked)
• steel rule, bar, or tape (1 mm or 1/64 in.)
• vernier caliper or caliper gage (25 mm or 0.001
  in.)
• micrometer (2.5 mm or 0.0001) used for measuring
  the thickness, and inside or outside diameters
• diffraction grating
• telescoping gage for indirect measurement of
  holes or cavities
• bevel protractor to measure angles
• Comparative length-measuring instruments
• Amplifies and measures variations or deviations
  in distance between two or more surfaces
• dial indicators (1 mm or 40 min)
• electronic gages sense the movement of the
  contacting pointer through changes in the
  electrical resistance of a strain gage or through
  inductance or capacitance (linear variable
  differential transformer - LVDT)

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• Measuring straightness, flatness, roundness, and
  profile
• straightness can be checked with straight edges
  or with dial indicators
• flatness can be measured by using a surface plate
  and a dial indicator
• or by interferometry using an optical flat
• roundness
• the round part is placed on a V-block or between
  centers and is rotated, with the point of a dial
  indicator in contact with the surface
• circular tracing, the part is placed on a
  platform, and its roundness is measured by
  rotating the platform
• profile
• a surface is compared with a template or profile
  gage to check shape conformity
• profile-tracing instruments

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• Threads and gear teeth
• thread gages that compare the thread produced
  against a standard thread
• optical projectors, called optical comparators
• Coordinate measuring and layout machines
• accuracy up to 0.25 mm or 10 min
• layout machines are used to measure parts with
  large dimensions (/- 0.04 mm or 0.0016 in)

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• General characteristics of measuring instruments
• The characteristics and quality of measuring
  instruments are generally described by certain
  specific terms. These terms, in alphabetical
  order, are defined as follows
• Accuracy - the degree of agreement of the
  measured dimension with its true magnitude
• Amplification - see magnification
• Calibration - adjusting or setting an instrument
  to give readings that are accurate within a
  reference standard
• Drift - see stability
• Linearity - the accuracy of the readings of an
  instrument over is full working range
• Magnification - the ratio of instrument output to
  the input dimension
• precision - degree to which an instrument gives
  repeated measurement of the same standard
• repeat accuracy - same as accuracy, but repeated
  many times

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• Resolution - smallest dimension that can be read
  on an instrument
• Rule of 10 - an instrument or gage should be 10
  times more accurate than the dimensional
  tolerances of the part being measured.
  Similarly, a factor of 4 is known as the Mil
  Standard rule
• Sensitivity - smallest difference in dimension
  that an instrument can distinguish or detect
• Speed of Response - how rapidly an instrument
  indicates the measurement, particularly when a
  number of parts are measured in rapid succession
• Stability - an instruments capability to
  maintain its calibration over a period of time
  (drift)

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• Automated measurement
• flexible manufacturing systems and manufacturing
  cells have led to the adoption of advanced
  measurement techniques and systems.
• Automated inspection is based on various on-line
  sensor systems.
• What factors contribute to subsequent deviation
  in the dimension of the same part produced by the
  same machine?
• Static and dynamic deflections of the machine
  because of vibrations and fluctuating forces,
  cause by variations such as in the properties and
  dimensions of the incoming material.
• Deformation of machine because of thermal
  effects.
• Wear of tolls and dies.

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• Dimensional tolerances
• is defined as the permissible or acceptable
  variation in the dimensions of a part.
• Tolerances become important only when a part is
  to be assembled or mated with another part.

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• Several terms are used to describe features of
  dimensional relationships between mating parts.
  These terms, in alphabetical order, are defined
  as follows
• Allowance - the specified difference in
  dimensions between mating parts also called
  functional dimension or sum dimension.
• Basic size - Dimension from which limits of size
  are derived, using tolerances and allowances.
• Bilateral tolerance - deviation (/-) from the
  basic size
• Clearance - the space between mating parts.
• Datum - a theoretically exact axis, point, line,
  or plane.
• Feature - physically identifiable portion of a
  part, such as hole, slot, pin, or chamfer.
• Geometric tolerancing - tolerances that involve
  shape features of the part.
• Hole-basis system - tolerances based on a zero
  line on the hole also called standard hole
  practice, or basic hole system.
• Interference - negative clearance.

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• Interference fit - a fit having limits of size so
  prescribed that an interference always results
  when mating parts are assembled.
• International tolerance grade (IT) - a group of
  tolerances that vary depending on the basic size,
  but provide that same relative level of accuracy
  within a grade.
• Limit dimensions - the maximum and minimum
  dimensions of a part also called limits.
• Maximum material condition (MMC) - the condition
  where a feature of size contains the maximum
  amount of material within the stated limits of
  size.
• Nominal size - dimension that is used for the p
  urpose of general identification.

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• Positional tolerancing - a system of specifying
  the true position, size, and form of the features
  of a part, including allowable variations.
• Shaft-basis system - tolerances based on a zero
  line on the shaft also called standard shaft
  practice, or basic shaft system.
• Standard size - nominal size in integers and
  common subdivisions of length.
• Transition fit - fit with small clearance or
  interference that allows for accurate location of
  mating parts.
• Unilateral tolerancing - deviation in one
  direction only from the nominal dimension.
• Zero line - reference line along the basic size
  from which a range of tolerances and deviations
  are specified.

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Testing and Inspection

• Nondestructive testing (NDT)
• is carried out in such a way that product
  integrity and surface texture remain unchanged
• requires skill
• examples
• liquid penetrant- fluids are applied to the
  surfaces of the part and allowed to penetrate
  into the surface openings, including cracks,
  seams, and porosity (width of 0.1 mm or 4 min)
• visible penetrants
• fluorescent penetrants
• magnetic particle - fine ferromagnetic particles
  are placed on the surface. When the part is
  magnetized, a discontinuity on the surface causes
  the particles to gather visibly around it.

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• Liquid Penetrant Inspection
• Principle A liquid penetrant is drawn into
  surface flaws by capillary action and
  subsequently revealed by developer material in
  conjunction with visual inspection.
• Advantages Simple, inexpensive, versatile,
  portable, easily interpreted, and applicable to
  complex shapes.
• Limitations Can only detect flaws that are open
  to the surface surfaces must be cleaned before
  and after inspection deformed surfaces and
  surface coatings may prevent detection and the
  penetrant may be wiped or washed out of large
  defects.
• Material limitations Must have nonporous
  surface.
• Geometrical limitations Any size or shape
  permitting accessibility of surfaces to be
  inspected.
• Permanent record Photographs, videotapes, and
  inspectors reports provide the most common
  records.

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• Ultrasonic inspection - an ultrasonic beam
  travels through the part. An internal defect,
  such as a crack, interrupts the beam and reflects
  back a portion of the ultrasonic energy. The
  amplitude of the energy reflected and the time
  required for return indicates the presence and
  location of any flaws in the workpiece.
• Acoustic emission - detects signals (high
  frequency stress waves) generated by the
  workpiece during plastic deformation, crack
  initiation and propogation, and sudden
  reorientation of grain boundaries, friction and
  wear sliding interfaces.
• Acoustic impact - tapping the surface of an
  object and listening to and analyzing the signals
  to detect discontinuities and flaws.
• Radiography - radiation (x-rays, etc.) is passed
  through the sample and absorbed depending on
  thickness, material, and flaws

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• Eddy current testing - and electrically
  conductive workpiece is brought bear an AC coil
  that produces a magnetic field, therefore
  producing eddy currents in the workpiece, which
  in turn produces a magnetic field interacting
  with the original. This modifies the impedance
  of the coil. Defects in the workpiece can affect
  the magnitude and direction of the induced eddy
  currents.

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• Radiography - involves x-ray inspection to detect
  internal flaws or density and thickness
  variations in the part.
• Eddy current inspection - based on the principle
  of electromagnetic induction.
• alternating current (60Hz to 6 MHz) flows through
  an electric coil
• the current causes eddy current to flow in the
  part
• defects in the part impede and change the
  direction of the current, causing changes in the
  magnetic field
• these changes affect the exciting coil, whose
  voltage is monitored to determine the presence of
  flaws
• Thermal inspection - involves observing
  temperature changes by contact or non-contact
  heat sensing devices (heat sensitive paints and
  papers, liquid crystals, and other coatings).

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• Automated inspection
• postprocess inspection - lacks flexibility,
  requires maintenance and inventory, results in
  some defective parts going through the system
• automated inspection - uses a variety of sensor
  systems that monitor the relevant parameters
  during the manufacturing process (on-line
  inspection)
• using these measurements, the process
  automatically corrects itself to produce
  acceptable parts
• it is flexible and responsive to product design
  change, less operator skill is required,
  productivity is increased, parts have higher
  quality, reliability, and dimensional accuracy
• Sensors for automated inspection
• sensors operate on the principle of strain gages,
  inductance, capacitance, ultrasonics, acoustics,
  pneumatics, infrared radiation, optics, lasers,
  and various electronic gages.

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• Quality assurance
• It is the total effort by a manufacturer to
  ensure that its products conform to a detailed
  set of specifications and standards (dimensions,
  surface finish, tolerances, composition, color,
  and mechanical, physical, and chemical
  properties).
• quality can not be inspected into a finished
  product
• 100 inspection is too costly
• several methods of inspecting smaller,
  statistically relevant sample lots have been
  devised
• Inspection
• incoming materials
• individual components
• assembled product
• testing the product

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• Statistical methods of quality control
• Sample size The number of parts to be inspected
  in a sample, whose properties are studies to gain
  information about the whole population.
• Random sampling Taking a sample from a
  population or lot in which each item has an equal
  chance of being included in the sample. Thus,
  when taking samples from a large bin, the
  inspector does not take only those that happen to
  be within reach.
• Population The totality of individual parts of
  the same design from which samples are taken.
• Lot size A subset of population. A lot or
  several lots can be considered subsets of the
  population and may be treated as representatives
  of the population.
• Sample is inspected for certain characteristics
  such as tolerances, finish, and defects. These
  characteristics come in two types
• quantitative (can be measured)
• qualitative (attributes)

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• Statistical Process Control (SPC)
• developed in the early 1950s
• it advises the operator to take certain measures
  and when to take them in order to avoid producing
  further defective parts
• SPC consists of several elements
• control charts and setting control limits
• capabilities of the particular process
• characteristics of the machinery involved

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Surface Treatments, Coatings, and Cleaning

• Reasons for surface treatments
• Improve resistance to wear, erosion, and
  indentation
• Control friction
• Reduce adhesion
• Improve lubrication
• Improve corrosion and oxidation resistance
• Improve stiffness and fatigue resistance
• Rebuild surfaces on worn components
• Improve surface roughness
• Impart decorative features, color, or special
  texture

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• Processes
• Shot peening the workpiece surface is hit
  repeatedly with a large number of cast steel,
  glass, or ceramic shot (small balls), making
  overlapping indentations on the surface. Because
  plastic deformation is not uniform throughout a
  parts thickness, shot peening imparts
  compressive residual stresses on the surface,
  thus inproving the fatigue life of the component.
• Roller burnishing (surface rolling) the surface
  of the component is cold worked by a hard and
  highly polished roller or series of rollers. It
  is used to improve mechanical properties of
  surfaces, as well as the shape and surface finish
  of components.

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• Explosive hardening large increase in surface
  hardness, very little change (less than 5) in
  the shape of the component.
• Cladding metals are bonded with a thin layer of
  corrosion-resistant metal by applying pressure
  with rolls or other means.
• Mechanical plating fine metal particles are
  compacted over the workpiece surfaces by
  impacting them with spherical glass, ceramic, or
  porcelain beads.
• Case hardening used to alter the surface
  properties of a part (carburizing,
  carbonitriding, cyaniding, nitriding, flame
  hardening, and induction hardening). Laser beams
  are used as a heat source in surface-treatment.
• Hard facing a relatively thick layer, edge, or
  point of wear-resistant hard metal is deposited
  on the surface by one of the welding techniques.

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• Thermal spraying metal in the form of a rod,
  wire, or powder is melted in a stream of
  oxyacetylene flame, electric arc, or plasma arc,
  and the droplets are sprayed on the preheated
  surface, at speeds up to 100 m/s with compresses
  air spray gun. (cold spray - 2 km/s)
• Thermal spray processes
• plasma (8300 ºC)
• detonation gun
• high velocity oxyfuel (HVOF) gas spraying
• wire arc
• flame wire
• Surface texturing etching using chemicals or
  sputtering, electric arcs, or atomic oxygen which
  reacts with surfaces and produces fine, conelike
  surface textures.
• Ceramic Coatings for high temperature and
  electrical resistance applications.

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• Vapor deposition
• The substrate is subjected to chemical reactions
  by gases that contain chemical compounds of the
  materials to be deposited.
• The deposited materials could be metals, alloys,
  carbides, nitrides, borides, ceramics, or various
  oxides.
• The substrate may be metal, plastic, glass, or
  paper.
• Typical applications are coating tools, drills,
  reamers, milling cutters, punches, dies, and wear
  surfaces.
• Two major deposition processes
• physical vapor deposition
• chemical vapor deposition
• thermochemical