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 bakingAlthough 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

Sodium silicate-CO2 mouldingNa2SiO3 (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.

NO-BAKE, AIR SET, CHEMICALLY BONDED SANDS

OTHER EXPENDABLE-MOLD CASTING PROCESSES

• Expensive metallic pattern, hence suitable for large batch production

Full mold casting

Lost foam process (similar to lost-wax technique)