PROCESSING MATERIALS

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PROCESSING MATERIALS
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Forming Processes

• Casting
• Castings are made from molds --- ice cubes, walk
  on a beach, cake pan
• One-piece and two-piece molds
• Slip is the liquid clay poured into a two-piece
  mold
• Pressing
• Pressing is like casting with a plunger
• Meat can be pressed into shape with hands
• Powdered metal pressed and heated --- sintering
• Forging
• Heating a metal and hammering into a shape ---
  blacksmith, coins
• Hydraulic and mechanical presses use powerful
  rams --- thousand tons of force

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Forming Processes

• Extruding
• Soft metal pressed/squeezed through an opening,
  e.g toothpaste
• End products do not require much more shaping and
  machining
• Blow Molding
• Air blows the plastic into a mold, e.g plastic
  bottles
• Vacuum Forming
• A vacuum pulls the warm, soft plastic down
• The plastic clings to whatever it is drawn
  against, e.g. blister packaging

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Separating Processes

• Shearing
• Using knife-like blade for separating
• When the force gets high enough, the material
  breaks along the line of the cut
• Sawing
• Separating with a blade that has teeth
• Cutting wood along the direction of the grain ---
  Ripping
• Cutting wood across the direction of the grain
  --- Crosscutting
• Handsaws used for wood have 6-10 tpi
• Metal is cut by hand using a hacksaw --- usually
  18 tpi
• Machine saws and table saws

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Separating Processes

• Drilling
• Pointed tool --- twisted drill
• Hand drill or an electric drill
• 1/10,000 - 31/2 inches drill
• Grinding
• Done by tools like grinders or sanding machines
• Abrasives --- crushed hard particles --- emery
  cloth or sand paper
• Removing tiny bit of material --- toothpaste,
  polish
• Sharpening knives, scissors --- safety glasses
• Shaping
• Pointed tool moves in to-and-fro motion
• Job piece moves in planing
• Chisels and planes are hand tools for the same
  purpose

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Separating Processes

• Milling
• Milling cutters
• Turning
• Different from shaping tools in that the tool
  doesnt move itself
• A lathe spins the work/job piece
• Feed and depth of cut
• Hard steel --- Diamond tools
• Other Separating Processes
• Chemical Separation --- Electrolysis, Water into
  H and O
• Filtering --- separating solids from liquids,
  e.g. stainer
• Magnets --- magnetic materials from nonmagnetic
  ones
• Distillation --- Crude oil patrol, diesel,
  JP4, JP10

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Combining Materials

• Coating
• Composite Materials
• Mechanical Means
• Nails
• Nails were once made one at a time --- ends
  heated red-hot. Automatic machines now make them
  by the thousands
• Nails should be at right angle to the grain ---
  best holding power. It should also go 2/3rd of
  the bottom piece
• Splitting of wood --- pilot hole
• Types of nails brad, finishing, casing, common
  and box (BCCFCB)
• Pennyweight --- cost of one hundred nails. Now it
  refers to the length of the nails, e.g. 8d is 2.5
  inches and 6d is 2 inches

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Combining Materials

• Mechanical Means
• Screws
• More holding power and they can be removed easily
• Wood --- the thread starts at the point and goes
  2/3rd the way to the head
• Sheet metal --- threaded all the way to the head
• Pilot hole is of the size of the body of the
  screw without threads --- root diameter
• Machine screws and bolts do not have pointed
  ends. They are held in place by a nut or a
  threaded hole
• Washers
• Used between the nut and the material being
  fastened
• Flat --- protects against damage by nut
• Lock --- keeps nut from loosening under vibration

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Combining Materials

• Mechanical Means
• Screwdriver
• A wide blade slip out of the screw
• A narrow blade will damage the screw slot
• It may slip --- never put your hand in line
• Rivets
• Two pieces of metal to be fastened
• Used in aircraft building
• One end of a rivet is already formed

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Combining Materials

• Thermal Means
• Soft Soldering
• Joining metals with heat and soft solder (lead
  and tin) using soldering irons or guns
• Soft solder melts at 450 F
• Most common way to attach wires in electronic
  circuits
• Hard Soldering
• Uses an alloy of brass or silver with acetylene
  torch. Also called brazing or silver soldering
• Hard solder melts at 1400 F
• Welding
• Metals are heated high enough to fuse together
• It requires temperatures of 6000-7000 F
• Gas Welding --- torch burns a mixture of air and
  gas
• Arc Welding --- a machine used high electrical
  current

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Combining Materials

• Gluing
• Glue forms a chemical bond b/w itself and the
  materials being glued
• Wood --- white/yellow glue
• Plastic, metal and ceramics --- epoxy
• Hot glues are applied with glue guns --- set
  rapidly
• Coating
• Ceramic dishes are coated with glass-like glazes
• Electroplating --- gold plating, silver plating
• Anodizing --- a thin oxide coating is formed on
  the surface of Aluminum
• Galvanizing --- coating steel with Zinc --- keeps
  steel from rusting
• Composite Materials
• Egyptians added straw to the clay they used to
  make bricks
• Combining several materials, e.g. plywood ---
  layers of wood
• Fiberglass is composite of glass and an epoxy
  resin --- much stronger and lighter than steel