Injection molding method of metal material

An injection molding method of a metal material adapted to employ an injection apparatus comprising a heating cylinder provided with a nozzle at a tip thereof and a supply port at a rear portion thereof and having inside a screw, which is allowed to rotate and move along an axial direction, for injecting the metered metal material in a liquid phase state through said nozzle by moving said screw forward, said method comprising the steps of:

• after injection, rotating said screw at a forward position a set number of times, removing metal material accumulated in a clearance between said heating cylinder and the screw flights wherein a retraction resistance is removed;
• accumulating the metal material in the liquid phase state in a front chamber by forcing said screw to retract for a set distance with rotation of said screw stopped or at a slower rotation rate than a rotation rate in the forward position, and applying a back pressure to said screw rotating at a retraction position, thereby starting transfer of liquefied metal material;
• completing accumulation by stopping rotation of said screw;
• pressing the liquefied metal material accumulated by moving said screw forward;
• and
• effecting injection of the liquid phase metal material only when a material pressure reaches a set pressure within a preset forward distance of said screw, whereupon metering is assumed to have been completed.