Die Casting a permanent mold casting process using

Die Casting a permanent mold casting process using pressure other than gravity

Parameters 4 shot pressures 1000 to 100, 000 psi 4 highly mechanized 4 cycle times – up to 18, 000 shots per hour – small components like zipper teeth

Parameters (Cont. ) 4 1/2 the die fastened to stationary platen 4 1/2 the die fastened to movable platen actuated by piston 4 casting pushed out by ejector pins

Two types of machines 4 hot chamber 4 cold chamber

Hot chamber machine 4 chamber is submerged in molten metal 4 forced into cavity by plunger 4 use low melting metals like – lead, tin, zinc 4 metals that don’t attack and erode the metal pot, cylinder, and plunger

Cold chamber machine 4 molten metal ladled into shot chamber (chamber not heated) 4 metals cast – higher melting point – al, magnesium, copper, ferrous metals

Flash 4 metal has flowed between die halves at parting line 4 reduced by adequate pressure clamping both die halves together 4 removed by shearing, blanking, grinding

Machine selection 4 rated according to clamping pressures – 25 to 3000 tons 4 die size 4 piston stroke 4 shot pressure 4 cost

Dies 4 water or oil cooled 4 use of release agents 4 wear increases with temp of molten metal 4 heat checking - surface cracking from repeated heating and cooling is a problem 4 can last up to 500, 000 shots before significant wear occurs

Die Design 4 draft 4 removal of sprues and runners

Types of die cavities 4 single 4 multiple - several identical cavities 4 combination - several different cavities 4 unit - simple small dies that can be combined in two or more units in a master die

Application 4 carburetors 4 small motors 4 business machines and appliance components 4 hand tools 4 toys

Advantages 4 can be automated 4 minimum expenditure of metal 4 thin wall sections (. 020”) 4 components cast internally – pins, shafts, fasteners

Advantages (Cont. ) 4 close tolerances 4 little or no finishing after removal of gate and flash 4 because molten metal chills rapidly, achieve fine grain structure with hard skin and higher strength

Disadvantages 4 equipment costs high