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MANUFACTURING PROCESS - INVESTMENT CASTING PROCESS


INVESTMENT CASTING PROCESS

THE ROOT OF THE INVESTMENT CASTING PROCESS, THE CIRE PERDUE OR “LOST WAX” METHOD DATES BACK TO AT LEAST THE FOURTH MILLENNIUM B.C. THE ARTISTS AND SCULPTORS OF ANCIENT EGYPT AND MESOPOTAMIA USED THE RUDIMENTS OF THE INVESTMENT CASTING PROCESS TO CREATE INTRICATELY DETAILED JEWELRY, PECTORALS AND IDOLS. THE INVESTMENT CASTING PROCESS ALOS CALLED LOST WAX PROCESS BEGINS WITH THE PRODUCTION OF WAX REPLICAS OR PATTERNS OF THE DESIRED SHAPE OF THE CASTINGS. A PATTERN IS NEEDED FOR EVERY CASTING TO BE PRODUCED. THE PATTERNS ARE PREPARED BY INJECTING WAX OR POLYSTYRENE IN A METAL DIES. A NUMBER OF PATTERNS ARE ATTACHED TO A CENTRAL WAX SPRUE TO FORM A ASSEMBLY. THE MOLD IS PREPARED BY SURROUNDING THE PATTERN WITH REFRACTORY SLURRY THAT CAN SET AT ROOM TEMPERATURE. THE MOLD IS THEN HEATED SO THAT PATTERN MELTS AND FLOWS OUT, LEAVING A CLEAN CAVITY BEHIND. THE MOULD IS FURTHER HARDENED BY HEATING AND THE MOLTEN METAL IS POURED WHILE IT IS STILL HOT. WHEN THE CASTING IS SOLIDIFIED, THE MOLD IS BROKEN AND THE CASTING TAKEN OUT.
THE BASIC STEPS OF THE INVESTMENT CASTING PROCESS ARE 
  1. PRODUCTION OF HEAT-DISPOSABLE WAX, PLASTIC, OR POLYSTYRENE PATTERNS
  2. ASSEMBLY OF THESE PATTERNS ONTO A GATING SYSTEM
  3. “INVESTING,” OR COVERING THE PATTERN ASSEMBLY WITH REFRACTORY SLURRY
  4. MELTING THE PATTERN ASSEMBLY TO REMOVE THE PATTERN MATERIAL
  5. FIRING THE MOLD TO REMOVE THE LAST TRACES OF THE PATTERN MATERIAL
  6. POURING
  7. KNOCKOUT, CUTOFF AND FINISHING. 



References :- www.nptel.iitm.ac.in
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