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PROCESSING MATERIALS

PROCESSING MATERIALS. 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

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PROCESSING MATERIALS

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  1. PROCESSING MATERIALS

  2. 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

  3. 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

  4. 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

  5. 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

  6. Separating Processes • Milling • Milling cutters • Turning • Different from shaping tools in that the tool doesn’t 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

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