Abstract: A method of plastically forming splines on a shaft-like workpiece is provided. The volume of part of the shaft-like workpiece on which the splines are plastically formed is generally the same as the volume of plastically processed portion following processing. In addition, the part on which the splines are formed first is made with a maximum diameter. The shaft-like workpiece extends from the first formed part toward the part that is not plastically processed in a conical shape.

Abstract: In a vacuum casting method, a molding cavity is reduced in pressure to a vacuum, and when a gate is opened, a molten metal which has been raised to a molten metal retaining dome is charged into the molding cavity at a high speed. When a portion of a molten metal held in a molten metal holding furnace is raised to the molten metal retaining dome via a stalk, (1) the rising speed of a portion of the molten metal is set at 5-10 cm/sec, or (2) the rising speed is varied between an early stage of the rising motion and a later stage of the rising motion. In the latter method, the rising speed at the early stage of the rising motion is set at a speed higher than 10 cm/sec, while the rising speed at the later stage of the rising motion is set at 5-10 cm/sec. Due to the rising speed control, air involvement by the rising molten metal is effectively prevented.

Abstract: A vacuum casting apparatus in which a molding cavity is reduced in pressure substantially to a vacuum, and upon opening a gate, a molten metal which has been raised to a molten metal retaining dome is charged into the molding cavity via a runner at a high speed. The runner has a first portion making a pool of molten metal, a second portion connecting the molten metal retaining dome to the first portion, and a third portion connecting the first portion to the molding cavity. A pin is slidably provided in the first portion of the runner. An opening of the second portion of the runner to the first portion is located nearer to the pin than an opening of the third portion of the runner to the first portion. When the pin is moved into the first portion of the runner, the pin first closes the opening of the second portion and then begins to apply pressure the molten metal in the molding cavity.

Abstract: In a method of vacuum casting wherein when the molten metal previously introduced into a molten metal reservoir is fed into a cavity, the lowest head of the molten metal in the molten metal reservoir is held to be higher than the level of a sprue, so that the cycle time of casting may be shortened and the quality of cast products may be improved. To this end, the interior of the molten metal reservoir is held gas tight while the sprue is opened by a gate member of straight tubular shape.

Abstract: A vacuum casting apparatus includes a plurality of pressure pins arranged in a molding cavity, and at least one pressure pin is located in a portion of the molding cavity farthest from a gate. The pressure pins are operated to pressurize the molding cavity in an order from the pressure pin located farthest from the gate to a pressure pin located nearest to the gate. A cross-sectional area reduced portion can also be formed in a portion of a runner connecting the molding cavity and the molten metal retaining dome. A molten metal in the molding cavity is thereby suppressed from flowing backward into the molten metal retaining dome when being pressurized by the pressure pins, so that the quality of the cast products is improved.

Abstract: In a method of vacuum casting molten metal sucked from a molten metal reservoir into a cavity held under a reduced pressure by opening a gate having been blocking the communication between the molten metal reservoir and the cavity, the trapping of gas and foreign matter in the cavity is effectively prevented. To this end, an accommodation space for accommodating gas and foreign matter is provided in the molten metal reservoir. The accommodation space is provided at a position from which the accommodated matter is not sucked into the cavity.

Abstract: In a vacuum casting method, a mold cavity is reduced in pressure to a vacuum, and when a gate is opened, a molten metal which has been raised to a molten metal retaining dome is charged into the cavity at a high speed. When a portion of a molten metal held in a molten metal holding furnace is raised to the molten metal retaining dome, an upper surface of the molten metal is moved downwardly and upwardly through at least one cycle in the molten metal retaining dome, or a swirl flow is generated in the molten metal in a stalk. Such a unique motion as the downward and upward motion or the swirl flow effectively operates to detach solid metal pieces from an inside surface of the molten metal retaining dome or the stalk to push them to an upper portion of the molten metal. As a result, the detached metal pieces are prevented from being charged into the mold cavity to thereby cause defects in a cast product.