Shell           Moulding
                           Shell moulding is a process well suited to  rapid,         automated, repetitive and high-volume production. The most  common method         for producing shell moulds is to use a dump box as shown in the  diagram.         The dump box is rotated through 360 degrees, so that the sand  contacts         the heated surface. An organic thermosetting resin, such as  phenol         formaldehyde or furane is typically used (2.5-4.5% of sand  volume) in         conjunction with a catalyst (11- 14% of resin volume). Catalysts  include         weak aqueous acids such as ammonium chloride or hexamine, a  white         powder.
         
        
	
	
	
		
		
		
			
		
		
	
	
		
	 
	
	
	
		
		
		
		
	
	
		
	 
	
	
	
		
		
		
		
	
	
		
	 
         
         
		  		   		 
The thickness of shell moulding, typically around 10 mm, is  determined by         the contact time between the sand and pattern. The shell  moulding is heated again         to cure the sand, causing it to harden. shell moulding is  released from the         pattern using ejector pins. The entire cycle can be completed in  a         matter seconds, making it suitable for rapid production. Cores  are added         to the shell mould and the two halves of the mould are glued and  clamped         together before the metal is poured. 
Shell Moulds are  relatively robust and         can therefore be stored for reasonably long periods of time.  Depending         on the cores used, spent sand can be reclaimed successfully  using         thermal reclamation.