MANUFACTURE OF SYNTHETIC RESIN ROTATING FUNCTION PART

PURPOSE:To improve the accuracy of a tooth forming section by injecting molten resin into a forming chamber of rotation function part shape with a ring thick wall section in a manner of causing to flow from thick wall sections into a thin wall section, solidifying the thin wall section, injecting high pressure gas into the unsolidified thick wall section, carrying out the molding in a cavity section and filling resin in the thick wall section. CONSTITUTION:The shape of a molding tool (cavity) 3 formed by mold clamping a fixed mold 1 and a movable mold 2 is of the gear shape as a rotating function part. Molten resin is injected into ring thick wall sections 5 and 7 of the molding tool 3 by a spool 13 and flowed therefrom into a thin wall section 8. The thin wall section 8 is solidified, and when the ring thick wall sections 5 and 7 are in the unsolidified state, high pressure gas is introduced from the spool 13, and cavities are formed in the thick wall sections 5 and 7 to fill the resin completely in the thick wall sections 5 and 7. The accuracy of the tick wall section 7 and the tooth forming section 5 forming a boss section of rotation center is improved to make the rotating performance superior.