 Finally , the Acurad system employed a patented double shot piston design . The idea was to use a second piston ( located within the primary piston ) to apply pressure after the shot had partially solidified around the perimeter of the casting cavity and shot sleeve . While the system was not very effective , it did lead the manufacturer of the Acurad machines , Ube Industries , to discover that it was just as effective to apply sufficient pressure at the right time later in the cycle with the primary piston ; this is indirect squeeze casting . 
