Abstract: Using a mold equipped with a rib-forming member capable of moving forward and backward relative to the mold cavity, produced is a lightweight, hollow resin molding having a reinforcing rib structure in the hollow area, from a fiber-containing thermoplastic resin having a fiber content of from 10 to 70% by weight. To produce the molding, a melt of a fiber-containing thermoplastic resin is injected into the mold cavity or is injected thereinto under compression, then the movable mold member is moved backward in the direction in which the mold cavity is expandable, and after the start of the mold member moving, a gas is introduced into the resin melt. Even though the molding has a hollow structure and has a large surface area, it has good stiffness and high strength, and has good appearances. The weight of the molding can be well controlled and reduced to any desired degree. The molding has many applications in various fields.

Abstract: A method for injection-molding a plastics propeller fan by using a fixed-side mold section and movable-side mold section, comprises the steps of providing a movable core at an area corresponding to a thicker portion of a blade section of the propeller fan; after a predetermined amount of plastics material has been injected into a blade space of a mold cavity defined by the fixed-side mold section, movable-side metal section and movable core and conforming to the propeller fan, pushing out the movable core into the mold cavity and, after this step, bringing the movable core back to a normal position conforming to a mold shape defining the blade space and forming a proper fan.

Abstract: A method for injection-molding a plastics propeller fan by using a fixed-side mold section and movable-side mold section, comprises the steps of providing a movable core at an area corresponding to a thicker portion of a blade section of the propeller fan; after a predetermined amount of plastics material has been injected into a blade space of a mold cavity defined by the fixed-side mold section, movable-side metal section and movable core and conforming to the propeller fan, pushing out the movable core into the mold cavity and, after this step, bringing the movable core back to a normal position conforming to a mold shape defining the blade space and forming a proper fan.

Abstract: A gas-introduced injection molding is disclosed, which is obtained by charging molten resin into a die and introducing gas into the charged molten resin. The molding thus obtained has a sufficient thickness portion extending linearly as a framework and a sheet-like small thickness portion integral with the sufficient thickness portion and having a uniform thickness, a space being formed inside the sufficient thickness portion. Thus, even by reducing the overall thickness of the molding it is possible to ensure sufficient rigidity with the hollow portion, and the molding is thus best suited as a sheet-like product requiring a predetermined rigidity, such as an automobile bumper, a household electric product casing, etc.