casting

casting

1. solidification in mold of metal or inyected into a die having a cavity on the shape of the desire part quickest way to shape a metal into a part, isotproic or uniform granes structure and properties

   • chossing prosses depends on
     • part size
     • part configuration
     • part quantity
     • required tolerances
     • metal specified

2. used

   • in every industry since all metals can be cast
     • prototiping
     • large quantity parts

3. elimination or reducing porpsity

   • siling, for surface porosity
   • isoestatic processing, for internal porosity

4. reusable patterns

   • wood
   • plastic
   • metal

5. expendable patterns

   • wax
   • pastic
   • polystyrene foam

6. patterns include

   • allowances for finish machinig
   • location of the parting line
   • details for alignment of mold halves
   • details for metal transfer through the mold

7. classifications

   • expendable mold/reusable pattern
     • multiple partes requires multiple molds
     • types
       • sand-mold casting
         • variations
           • green-sand molds
             • flexible mixture of sand, clay and water
           • no-bake molds
             • mixture of sand resin
           • shell molds
             • resin covered by sand by rotation
         • pros and cons
           • not very precise
           • low cost production
           • sand can be reused
         • parts
           • cope:upper mold
           • drag:lower mold
           • pouring
           • spru
           • runner system
           • gates
       • plaster-mold casting
         • for non-ferrous materials
           • low thermal conductivity
         • made of
           • gypsum
           • strengthening compounds
           • water
       • ceramic-mold casting
         • for ferrous and non-ferrous metals
         • types
           • shaw process
           • unicast process
   • expendable mold/expensable pattern
     • types
       • investment casting
         • lost-wax casting
         • made by: inyection molding
           • called a three
         • assemble wax patterns
           • dipping a pattern cluster into a slurry
             • place in a furnace or autoclave to melt out and/or vaporize the wax
               • mold burnout to remove moisture
         • pros
           • complex shapes can be reached
           • closed tolerances
       • evaporative-foam casting
         • use of polyestyrene foam
         • covered with silicon
         • surrounded by sand
         • pros
           • single flask replaces cope and drag
           • cores are not required
           • foam patterns are light in weight
           • no parting line
           • smoother as-cast finish
   • permanent mold/no pattern
     • permanent-mold casting
       • pros
         • uniform shapes
         • close tolerances
         • cmooth finishes
       • made of
         • gray iron
         • carbon steel
         • hot- work tool steels
         • graphite
       • non-ferrous metals
     • die casting
       • rapid high production
       • hot-chamber machine
         • for low melting temperature metals like zinc
       • cold-chamber machine
         • die cast higher temperature
           • alluminum
           • magnesium
           • copper
     • centrifugal casting
       • types
         • true
           • metal is purrued into a mold rotating in a horizontal or vertical plane about its central axis
         • semi
           • molds surrounds the casting and controls the shape