JPH02121817A - Cast molding method for rotor - Google Patents

Abstract

PURPOSE:To reduce the number of post-machining steps by covering the upper face of an insert passed through a centering shaft and positioned in a mold with a cover having a diameter equal to or smaller than the outer diameter of the insert, closing molds, injecting resin, and removing, after molding, the cover together with unnecessary resin. CONSTITUTION:A metal insert 3 is passed through the centering shaft 2 of a mold 1. The end of the shaft 2 is formed in a small diameter, a steel plate cover 8 (having a diameter equal to or smaller than the outer diameter of the insert 3) is passed through the small-diameter part 7 to be fixed to cover a gap between the shaft 2 and the insert 3. The molds 1, 1' are closed, filler- containing phenol resin is injected and molded. The cover 8 is easily removed by disconnecting resin at the time of machining for removing a gate 5 from a molded form, the resin is not impregnated to the center of the insert, and not necessarily removed. Accordingly, the step of removing burr after molding is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the production of synthetic resin rotating bodies such as gears and pulleys. The present invention relates to an insert casting method for molding a rotating body by injecting.

BACKGROUND OF THE INVENTION When synthetic resin rotating bodies such as gears and pulleys are manufactured by injection molding, a central disgate is used to ensure roundness of the rotating body. In the case of a specification in which a metal insert is cast into the boss portion of the rotating body, the metal insert 3 is mounted and positioned on the centering shaft 2 installed in the mold 1 as shown in Fig. 4, and then the mold 1. 1' is closed and resin 4 is injected. However, since the gate 5 is located directly above the metal insert 3, the injected resin 4
and the metal insert 3 attached thereto (as shown in FIG. 5 as an enlarged view of section A in FIG. 4).

In the case of resins that undergo a melt-hardening reaction in the mold, such as phenolic resins, the injection pressure of 500 to 9/- or more is applied, so the resin can enter even a gap of 0.01 m and cause paris. become. Additionally, if there is a keyway or spline on the inner wall of the hole of the metal insert, it is difficult to reliably fill the space created between them when it is attached to the centering shaft, and resin should not fill in these gaps. Since intrusion is unavoidable, a large number of man-hours are required to remove the paris after molding.

Problems to be Solved by the Invention As mentioned above, when molding is performed by injecting resin from directly above the metal insert (constituting the center of the rotating body) placed in the mold, the core with the metal insert attached It was difficult to prevent resin from entering the gap between the output shaft and the metal insert. The purpose of the present invention is to prevent this resin from entering and facilitate post-processing to remove pars.

Means for Solving the Problems The present invention is an insert casting method in which the above metal insert is passed through a centering shaft and positioned in a mold, and resin is injected from directly above the metal insert to mold a rotating body. In molding, (a) the step of covering the top surface of the metal insert positioned in the mold through the centering shaft with a cover that has a diameter equal to or smaller than the outside diameter of the metal insert (b) the mold is then closed and the resin The process of injecting (c) is characterized by the step of removing the cover together with unnecessary resin after molding.

Function As described above, in the present invention, when resin is injected, the gap between the metal insert and the centering shaft to which it is attached is covered with a cover, which prevents the resin from entering this gap. be able to. After molding, the cover can be easily removed when removing unnecessary resin such as the gate portion from the molded product.

Example Examples of the present invention will be described in detail below.

As shown in FIG. 1, a metal insert 3 (made of 845C carbon steel) is passed through a centering shaft 2 provided in a mold 1. The tip of the centering shaft 2 is formed with a small diameter, and the small diameter part 7 has a diameter of 1.6 mm.
It is fixed through a steel plate cover 8 (same diameter as the outer diameter of the metal insert 3) having a thickness of mm to cover the gap created between the centering shaft 2 and the metal insert 3. Thereafter, the molds 1 and 1' were closed and the filled phenol resin was injected to form a toothed pulley.

The cover was easily removed by cutting off the resin during processing to remove the gate from the molded product, and no resin entered the keyway on the inner wall of the hole in the center of the metal insert, so there was no need to remove it.

Embodiment 2 FIG. 2 shows a case where the metal insert 3 incorporates a ball bearing. The gap between the metal insert 3 and the centering shaft 2 and the gap between the inner and outer rings of the ball bearing were covered with a cover 8 and injection molded as in Example 1. The cover 8 was a 3 m thick steel plate with an outer diameter 2 mm smaller than the metal insert 3.

Although it is absolutely unacceptable for resin to enter the ball part of the bearing, the cover was pressed against the metal insert with great force due to the pressure during injection molding, so no resin entered.

Embodiment 3 As shown in FIG. 3, this is an example in which a magnet 9 is embedded in the upper end surface of the centering shaft 3 as means for fixing the cover 8 covering the gap. The cover 8 is attracted and fixed by the magnet 9. If the suction fixation is reliable, the small diameter portion 7 is not necessarily necessary.

Effects of the Invention As mentioned above, the present invention can prevent resin from entering the gap between the metal insert and the centering shaft in insert casting molding through a simple process, and can reduce the number of post-processing steps. It is. Additionally, if the metal insert is made of a material with low hardness such as aluminum or galvanized, it may be deformed or the plating may peel off due to the pressure or flow of the injected resin. The existence of this solves this problem.

[Brief explanation of the drawing]

1 to 3 are sectional views of essential parts showing an embodiment of the present invention, FIG. 4 is a sectional view of essential parts showing a conventional method, and FIG. 5 is an enlarged view of section A in FIG. 4. 1.1' is the mold, 2 is the centering shaft, 3 is the metal insert, 5 is the gate, 7 is the small diameter part, 8 is the cover 9 is the magnet

Claims (1)

[Claims] 1. Metal insert (constituting the central part of the rotating body)
In insert casting molding, in which the metal insert is attached to the centering shaft and positioned in the mold, and resin is injected from directly above the metal insert to form a rotating body, (a) the metal insert is passed through the centering shaft and placed in the mold. A process of covering the top surface of the positioned metal insert with a cover having an outer diameter equal to or smaller than the outer diameter of the metal insert, (b) A process of subsequently closing the mold and injecting resin, (c)
A casting method for rotary bodies, which is characterized by a step of removing the cover along with unnecessary resin after molding. 2. The casting method for a rotary body according to claim 1, wherein the tip of the centering shaft has a smaller diameter than the mounting portion of the metal insert, and a cover is passed through the small diameter portion and fixed. 3. The casting method for a rotating body according to claim 1 or 2, wherein a magnet is embedded in the upper end surface of the centering shaft, and the magnetic cover is attracted and fixed to the magnet.