5. other expendable and permanent mold casting

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5. other expendable and permanent mold casting

  1. 1. Different types of sand moulding Green sand mold: most common, evolved from manual to mechanized process; Rough finish poor dim accuracy Dry sand mold: Strengthening of the mold by heating and subsequent baking Although the previous problems can be minimized it is not cost effective Skin-dry sand mold • An compromise between the two, drying the mold adjacent to the mold • refractoriness is increased by silica wash, zircon sand and also by using additional binders
  2. 2. NO-BAKE, AIR SET, CHEMICALLY BONDED SANDS Sodium silicate-CO2 moulding Na2SiO3 (water glass) added to sand acts as a binder when exposed to CO2 Strong hardening of the entire mold leads to • poor collapsibility • poor shake out • poor core removal Solution: • skin-treatment approach • alternative binders like room temp-cured resins.
  3. 3. OTHER EXPENDABLE-MOLD CASTING PROCESSES
  4. 4. • Expensive metallic pattern, hence suitable for large batch production
  5. 5. Full mold casting
  6. 6. Lost foam process (similar to lost-wax technique)

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