Surface Finishing

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Surface Finishing

• Raquel Ayala, Kevin Johnson,
• Rick Russell

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Overview

• Post Surface Finishes
• Design Considerations
• Removing and Reshaping
• Adding and Altering

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Post Machining

• Turning, boring, milling, drilling, sawing,
  broaching, grinding, shaping, planing, and
  reaming.
• Burrs

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Water jet

• Warpage
• Burrs
• Uneven Cutting

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Welding

• Spatter
• Rainbow
• Slag

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Laser and Plasma Cutting

• Burrs
• Oxidation
• Uneven Cutting

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Shearing and Punching

• Pinching

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Casting and Forging

• Parting Lines
• Surface Conditions

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When does design dictate surface finish
required

• Cosmetics
• Sliding - Ex. carbon embedded in Stainless steel
• Sliding Fits and Tolerances

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Tolerances
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Removing and Reshaping

• In Depth Look At
• Buffing
• Blasting
• Machining
• Brief Overview Of
• Flame Polishing
• Shot Peening

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Buffing

• Polishing operation, workpiece is brought into
  contact with revolving cloth wheel
• Abrasive compound is applied to wheel
• Can remover fine scratches and tarnish from the
  surface of work

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Buffing

• Smooth, reflective surface is left behind
• When buffing soft metals, small amounts of metal
  flow may occur, reducing high spots

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Buffing

• Mostly a manual process, high labor rate
• If part had simple geometry, it can be held in a
  fixture and buffed by machines
• Keep in mind that this is mostly for exterior
  surfaces interior surfaces may be hard to reach

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Blast Cleaning

• During metal working processes, there are many
  chances for surface contamination
• Blast cleaning uses an abrasive propelled onto
  the workpiece surface using air or water
• Abrasive particles can be steel grit, metal shot,
  fine glass shot, plastic beads, and even CO2

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Blast Cleaning

• Air pressure of 10-60psi for non-ferrous metals
• Air pressure of 60-100psi for ferrous metals,
  particle speeds can reach 400 mph!
• KE1/2mv2 (400 mi/hr178.8 m/s) (mgrain.03 mg)
• KE1/2(3.0E-8 kg)(178.8 m/s)2
• KE4.8E-4 J 0.00048 J

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Blast Cleaning

• Large scale blasting can be done with a mobile
  air compressor and sand tank
• Small scale blasting
• can be done in an
• enclosed cabinet
• or room

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Blast Cleaning

• From a manufacturing standpoint, can only be done
  in certain instances
• Hard to maintain precision
• Can only be used in line of sight
• Will tend to round and sharp corners

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Machining

• The quality of a machined surface is directly
  related to the technique tooling used as well
  as tolerances held
• Every process leaves an identifiable pattern on
  the machined surface
• Fingerprint

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Machining

• Roughness and Waviness Profiles

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Machining

• Machined surface finish is controlled by many
  factors
• materials properties
• speed, feed, tooling, machine quality
• operator experience, and whether or not the part
  was made on Monday 800am or Friday 400pm

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Brief Overview of

• Flame Polishing Shot Peening

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Adding and altering

• Look At
• Surface Hardening
• Paints Surface Coatings
• Conversion Coatings
• Thin Surface Films

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Surface Hardening

• Surface hardening is the process of hardening the
  surface of a metal, often a low carbon steel, by
  infusing elements into the material's surface,
  forming a thin layer of a harder alloy. Case
  hardening is usually done after the part in
  question has been formed into its final shape.
• Includes
• Case Hardening
• Carburizing
• Nitriding

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Case Hardening / Carburizing

• Case hardened steel is usually formed by
  diffusing carbon, nitrogen, and/or boron into the
  outer layer of the steel at high temperature, and
  then heat treating the surface layer to the
  desired hardness.

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Paints Surface Coatings

• Paint is used to protect, color, or add
  functionality to an object or surface by covering
  it with a pigmented coating. An example of
  protection is to retard corrosion of metal. An
  example of decoration is to add festive trim to a
  room interior. An example of added functionality
  is to modify light reflection or heat radiation
  of a surface. Another example of functionality
  would be the use of color to identify hazards or
  function of equipment and pipelines.
• Includes
• Painting
• Powder coating
• Plasma spraying

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Painting

• Spraying
• Automatic
• Hand
• Dipping
• Hand Brushed

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Conversion Coatings

• Conversion Coatings are coatings for metals where
  the part surface is converted into the coating
  with a chemical or electro-chemical process. They
  are used for corrosion protection, increased
  surface hardness, to add decorative color and as
  paint primers. Conversion coatings may be very
  thin, on the order of 0.00001 and thicker
  coatings can be up to 0.002.
• Includes
• Anodizing
• Bluing
• Parkerizing

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Anodizing

• Carbon steel can not be anodized.
• Aluminum, titanium, magnesium, zinc are
  anodizable.
• A layer of oxidation is placed, dyed and
  thermally set to form a protective seal against
  corrosion and wear.

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Thin Surface Films

• Thin-film deposition is any technique for
  depositing a thin film of material onto a
  substrate or onto previously deposited layers.
  "Thin" is a relative term.
• Includes
• Galvanizing
• Chemical vapor deposition (CVD)
• Electroplating
• Physical vapor deposition (PVD)
• Gilding

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Gilding

• Thin films of gold or other metals are applied to
  a clean smooth surface and adheres and is
  smoothed out removing bubbles.

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Electroplating

• Video

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Conclusion

• Post Surface Finishes
• Design Considerations
• Removing and Reshaping
• Adding and Altering

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References

• http//en.wikipedia.org/wiki/Surface_finishing
• http//www.mfg.mtu.edu/cyberman/quality/sfinish/te
  rminology.html
• Materials and Processes in Manufacturing, E.P.
  DeGarmo, J.T. Black, and R.A. Kohser, Wiley, 10th
  Edition

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Questions