| 摘要 |
PURPOSE:To mold a rotational polygonal mirror which is free of distortion due to sink or residual stress at the high accuracies of finished surfaces and of dimensions by injecting molten resin into a polyhedron die, closing the die, forming a metallic film on the surface of the taken-out polyhedron and coating it with a protective film. CONSTITUTION:The molten resin is injected into the polyhedron die previously equipped with gaps so that no molten resin flows out. After a gate is sealed, the gaps are press-bonded to close the die. After a fixed time has passed, the polyhedron is taken out. The metallic film is formed on the surface of the polyhedron, and is coated with the protective film. Namely, the volume of a cavity part 10A is pressurized and reduced to obtain the rotational polygonal mirror 10 with accurate surfaces and accurate dimensions, etc. Pressurizing in the process of reducing and cooling spreads and uniformizes internal stress to reduce the change in the lapse of time due to residual stress. Simultaneously, the sink caused in a thick part is absorbed and prevented to form the rotational polygonal mirror 10 made of resin, which is excellent in durability and finished surfaces. |
