The mechanical vacuum shut-off valve is the most effective way of obtaining a good vacuum in the cavity. The valve closes when the advancing liquid metal front contacts a triggering piston and is diverted. Since the recommended speeds of the injection piston in the shot sleeve during the second phase of injection range from 2.5 to 5.5 m/s, the speed of the metal in the valve can exceed 500 m/s. When this metal stream hits the trigger piston it is diverted, and it is the force induced on the piston by this change in momentum that causes the valve to close so rapidly during the very last milliseconds of the shot. This maintains the vacuum until the last possible moment, which is important because air from leaks, residual water vapour and the gaseous products of the combustion of the die lubricant continue to be generated right up to the moment when the die is completely filled; if they were not removed, they would cause porosity in the parts of the component corresponding to the regions of the cavity that are filled last. The VDS valve “Standard Plus” delivers this required performance, with high reliability in service and low maintenance costs.