PURPOSE: To enable to injection-mold a molded part with the predetermined accuracy in shape by a method wherein polycarbonate resin containing glass flakes is molten and injected with an injection molding machine in a molding die by changing stepwise injection speed and injection pressure at various locations and stages during injection molding in the ranges of specified injection speeds and injection pressures.

CONSTITUTION: Injection molding is performed by means of synthetic resin material containing glass flakes under the condition that the injection speed and injection pressure are respectively stepwise changed within the range of 90W6mm/ sec for speed and of 2,100W1,500kg/cm2 for pressure. Concretely, polycarbonate containing 30% of glass flakes, each of which has mean thickness of 3μm and the magnitude of a side of 50W500μm, is empolyed as synthetic resin material. The injection speeds of molten resin in passing through a sprue 4 and a gate 3 are respectively set in the orders of 87mm/sec and 60mm/sec. In addition, the injection speed at the time point just before the cavity becomes full of the material is set in the order of 36mm/sec. The injection pressure are successively set at about 1,600kg/cm2 as primary pressure, 1,866kg/cm2 as secondary pressure and 2,100kg/cm2 as tertiary pressure.