A method for filling a mold with a compressible liquid material is disclosed. The mold is connected to a manifold via a plurality of runners, with at least one valve disposed in at least one of the plurality of runners. A controller is configured to pressurize the manifold with the liquid material, and modulate the at least one valve to perform a plurality of pulse cycles during one filling cycle of the mold. A pulse cycle includes adjusting an aperture of the valve from a first position to a second position, and adjusting the aperture of the valve from the second position to a third position, where the aperture corresponding to the second position is larger than the aperture corresponding to the first position, and the aperture corresponding to the third position is smaller than the aperture corresponding to the second position.