The Sand Casting Process The most commonly used Casting Process, in the entire Casting Industry. Concept: The top and the bottom of the mold form the flask. "holds the whole thing together." The cope and the drag. An impression device, in the middle of the flask assembly, called the pattern. The sand around the pattern is called the, holding medium. These are the basic, universal casting components, which can be applied to all Casting and Molding Processes. The mold maker uses the pattern to make the impression in the holding medium, the sand, then sets the pattern aside, closes the cope and drag, to complete the flask, and forms the mold, fills that void with a molten material; which could be almost anything. NITC

Casting a component NITC

CARBON-DI OXIDE PROCESS (SILICATE BONDED SAND PROCESS) FIRST IN 1950s MIXTURE OF SAND AND 1.5% TO 6 % SODIUM SILICATE (AS BINDER) MIXTURE PACKED AROUND THE PATTERN, HARDENED BY BLOWING CO 2 DEVELOPED FURTHER BY ADDDING OTHER CHEMICALS AS BINDERS MAINLY TO MAKE CORES- AS USE IS IN ELEVATED TEMPERATURE APPLICATION

Na 2 O SiO 2 + H 2 O +CO 2 Na 2 CO 3 + (SiO 2 +H 2 O) (Silica Gel) Formation of Silica Gel gives strength to the moulds + Points: Drying not necessary Immediately ready for pouring Very high strength achieved Dimensional accuracy very good -Points -Collapsibility poor, can be improved by additives -Na 2 O SiO 2 attacks and spoils wooden pattern

CO 2 Funnel CO 2 Moulding Mould

DIE CASTING GRAVITY SEMI PERMANENT MOULD OR PERMANENT MOULD COLD CHAMBER HOT CHAMBER (HEATING CHAMBER) OUTSIDE THE MACHINE INTEGRAL WITH THE MACHINE

PERMANENT MOULD OR GRAVITY DIE CASTING * METALLIC MOULDS USED *TWO HALVES OF DIES- ONE FIXED, ONE MOVABLE VERY CLOSE TOLERANCE CASTINGS, MORE STRENGTH, LESS POROUS -BETTER SURFACE FINISH COMPARED TO SAND CASTING -SURFACE FREE FROM SAND & DENSITY HEAVY ONLY FOR SMALL AND MEDIUM SIZE CASTINGS FOR NON FERROUS, MAINLY LARGE QUANTITY, BUT IDENTICAL PIECES ONLY

PERMANENT MOULD OR GRAVITY DIE CASTING * METALLIC MOULDS USED - MOULD TO WITHSTAND TEMPERATURE *NO EXTERNAL PRESSURE APPLIED, *HYDROSTATIC PRESSURE BY RISERING *LAMP BLACK/CORE OIL APPLIED TO DIE SURFACES FOR EASY REMOVAL *FAST CONDUCTION, RAPID COOLING *TWO HALVES OF DIES- ONE FIXED, ONE MOVABLE NITC

+POINTS - VERY CLOSE TOLERANCE CASTINGS, MORE STRENGTH, LESS POROUS - BETTER SURFACE FINISH COMPARED TO SAND CASTING - SURFACE FREE FROM SAND - DENSITY HEAVY - MORE DIMENSIONAL ACCURACY TO 0.3 MM - DIES LESS COSTLY THAN PRESSURE DIE CASTING DIES - GOOD FOR PRESSURE TIGHT VESSELS - LESS COOLING CRACKS - LESS SKILL - GOOD FOR LARGE QUANTITIES NITC

- POINTS  ONLY FOR SMALL AND MEDIUM SIZE CASTINGS  FOR NON FERROUS, MAINLY  LARGE QUANTITY, BUT IDENTICAL PIECES ONLY  POOR ELONGATION  STRESS AND SURFACE HARDNESS DEFECTS OBSERVED  CASTING TO BE WITHDRAWN CAREFULLY FROM DIES NITC

A TYPICAL DIE ECCENTRIC CLAMPING MOULD / DIE HALF VENT HOLE POURING BASIN MOULD CAVITY

SEMIPERMANENT DIECASTING DIE PRESSURE AT 20 TO 20,000 ATM PRESSURE FILL SOLIDIFICATION FOR NONFERROUS METALS FOR INTRICATE SHAPES CLOSE TOLERANCES POSSIBLE FOR MASS PRODUCTION, >10,000 NITC

A MUST FOR SEMI AND PRESSURE DIE CASTING SET UPS, THE FOLLOWING FACTORS A MUST 1. A GOOD DIE SET MECHANISM 2. MEANS FOR FORCING METAL 3. DEVICE TO KEEP DIE HALFS PRESSED 4. ARRANGEMENT FOR AUTOMATIC REMOVAL OF CORES- IF ANY 5. EJECTOR PINS NITC

TWO TYPES OF PRESSURE DIE CASTING COLD CHAMBER - HEATING CHAMBER OUTSIDE THE MACHINE - FOR Al, Mg, Cu, AND HIGH MELTING ALLOYS HOT CHAMBER - HEATING INTEGRAL WITH THE HANDLING GOOSE NECK MECHANISMS WIDELY USED FOR LOW MELTING ALLOYS- Zn, Pb, Etc. ALSO VACUUM DIE CASTING MACHINES- SPACE BETWEEN THE DIES AND PASSAGE VACUUMISED BEFOR POURING- SUBMERGED PLUNGE TYPE, DIRECT AIR DIE CASTING MACHINES

D.A.D.C. MACHINE – showing two positions of pot

ANOTHER TYPE OF D.A.D.C. MACHINE