a permanent mold casting process using pressure other than gravity Die Casting a permanent mold casting process using pressure other than gravity
Parameters shot pressures 1000 to 100,000 psi highly mechanized cycle times up to 18,000 shots per hour small components like zipper teeth
Parameters (Cont.) 1/2 the die fastened to stationary platen 1/2 the die fastened to movable platen actuated by piston casting pushed out by ejector pins
Two types of machines hot chamber cold chamber
Hot chamber machine chamber is submerged in molten metal forced into cavity by plunger use low melting metals like lead, tin, zinc metals that don’t attack and erode the metal pot, cylinder, and plunger
Cold chamber machine molten metal ladled into shot chamber (chamber not heated) metals cast higher melting point al, magnesium, copper, ferrous metals
Flash metal has flowed between die halves at parting line reduced by adequate pressure clamping both die halves together removed by shearing, blanking, grinding
Machine selection rated according to clamping pressures die size 25 to 3000 tons die size piston stroke shot pressure cost
Dies water or oil cooled use of release agents wear increases with temp of molten metal heat checking - surface cracking from repeated heating and cooling is a problem can last up to 500,000 shots before significant wear occurs
Die Design draft removal of sprues and runners
Types of die cavities single multiple - several identical cavities combination - several different cavities unit - simple small dies that can be combined in two or more units in a master die
Application carburetors small motors business machines and appliance components hand tools toys
Advantages can be automated minimum expenditure of metal thin wall sections (.020”) components cast internally pins, shafts, fasteners
Advantages (Cont.) close tolerances little or no finishing after removal of gate and flash because molten metal chills rapidly, achieve fine grain structure with hard skin and higher strength
Disadvantages equipment costs high