Metering method of metal material in injection molding

A metering method of a metal material in injection molding employing a single heating cylinder having a tip, a front chamber, and a rear portion, a nozzle disposed at the tip and a supply port of a granular metal material disposed at the rear portion, a screw disposed inside the heating cylinder, the screw operative to rotate and move along an axial direction, for melting the metal material in said heating cylinder to be transferred to and metered in said front chamber of said heating cylinder in a liquid phase state, and then injecting the metal material from said front chamber through said nozzle by moving said screw forward, said method comprising the steps of:

• placing said single heating cylinder in an inclined position with a head thereof pointing downward, and operating said single heating cylinder so that the metal material turns from a granular material to the liquid phase state and, in the liquid phase state, flows down into said front chamber due to self-weight;
• forcing said screw, at a forward position after injection, to retract to a set position without rotation while maintaining an inclination, thereby accumulating a predetermined quantity of a liquid phase material in said front chamber of said heating cylinder, the accumulation due to suction from a negative pressure in said front chamber acting on the liquid phase material stored primarily on a periphery of a head portion of said screw;
• and
• stopping the retraction of said screw, then rotating said screw at a retracted position, thereby metering a constant quantity of the liquid phase material in said front chamber, whereby the constant quantity can be repetitively metered during subsequent metering operations.