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 –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

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

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

Separating Processes  Drilling –Pointed tool --- twisted drill –Hand drill or an electric drill –1/10, / 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

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

Combining Materials CoatingCoating Composite MaterialsComposite 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 2/3 rd 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

Combining Materials  Mechanical Means –Screws  More holding power and they can be removed easily  Wood --- the thread starts at the point and goes 2/3 rd 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

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

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 F  Gas Welding --- torch burns a mixture of air and gas  Arc Welding --- a machine used high electrical current

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