Method of controlling vacuum in vacuum die-casting and vacuum control system for carrying out the same

摘要

A method of controlling vacuum in vacuum die-casting and a vacuum control system for performing the same adjusts the time to open a vacuum valve to start degassing in connection with the position of an injection plunger to control vacuum in a cavity so that gases may not be involved in a molten metal injected into the cavity. The method comprises opening the vacuum valve to start degassing the cavity upon the advancement of the injection plunger to a first position. The vacuum in a vacuum system is measured upon the arrival of the injection plunger at a second position immediately before a final position where the injection plunger completes the injection of the molten metal. A measured vacuum is compared with a predetermined reference vacuum. The first position is shifted by a predetermined distance toward the die when the measured vacuum is higher than the reference vacuum or by a predetermined distance away from the die when the measured vacuum is lower than the reference vacuum to set a corrected first position. The vacuum valve is opened when the injection plunger arrives at the corrected first position in the next injection cycle.