JPH1170539A - Insert molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the adverse effect by a weld by the rotation of an insert work itself by stirring the resin in a cavity by rotating the insert work at the time of injection filling with the resin and stopping the insert work before the resin is solidified to insert the same into the resin at a predetermined position. SOLUTION: An electromotor 17 is operated during a period when the interior of a resin 19 has flowability and the rotatory power thereof is transmitted to a rotary pin 10 through a spline 12 and the insert work 7a fitted to the leading end thereof is rotated together with the rotary pin 10. This rotation is performed after the resin 19 is injected but may be started from a point of time immediately before the injection of the resin 19 according to circumstances and the resin at the part coming into contact with the insert work 7a is pulled by the side surface of the work by the rotation to be stirred. This stirring region is expanded by the increase in viscosity accompanied by the cooling of the resin 19 and the boundary of the resin by confluence is disturbed and a weld is erased. The rotation of the insert work 7a is stopped before the internal resin is solidified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insert molding method for integrally molding an insert work such as a metal product and a resin in a mold.

[0002]

In the usual insert molding, an insert work is inserted in a cavity of a mold in advance, a resin is injected and filled into the cavity, and a part of the insert work is embedded in the resin. I am trying. If the insert work allows the resin to penetrate through the gear or wheel shaft, hold both ends of the insert work on the opposing mold surface and insert the insert work so that it is positioned across the cavity. I have.

In such conventional insert molding, since the insert work is positioned laterally with respect to the flow direction of the resin in the cavity, the flow of the resin is divided by the insert work and then merged. Welding not only impairs the appearance of molded products,
There is also a problem in impact strength.

The present invention has been conceived in view of the above circumstances, and has as its object to suppress the adverse effects of welds caused by rotation of the insert work itself even in insert molding in which an insert work is previously inserted into a cavity. It is an object of the present invention to provide a new insert molding method.

[0005]

SUMMARY OF THE INVENTION According to the present invention, an insert work is rotatably set in a cavity formed by closing a fixed mold and a movable mold. After rotating and agitating the resin in the cavity, the resin is stopped before the resin is solidified, and is inserted into a predetermined position in the resin.

In this new insert molding method, even if the flow of the resin in the cavity is divided by the insert work and merged, the weld generated by the merge is wiped out by the stirring of the resin by the rotation of the insert work itself. Thus, the problem of the impact strength due to the weld of the insert molded product or the problem of the appearance can be easily solved, and the quality can be improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, a half part of a mold capable of simultaneously injecting a molten resin into a pair of cavities via a runner is omitted, wherein 1 is a fixed type and 2 is a movable type. A cavity 3 such as a wheel is recessed on the surface.

A sprue 4 connected to a runner on a parting surface is formed in the fixed mold 1, and a nozzle 5 a of an injection device 5 is in contact with the sprue 4 through a fixed platen 6. A receiving hole 8 having an inner diameter slightly larger than the outer diameter of the insert work 7 is formed in the center of the parting surface facing the cavity 3.

Inside the movable die 2, a work setting hole 9 of the insert work 7 is formed in the center of the cavity 3 so as to face the receiving hole 8, and a rotating pin 10 is inserted into the work setting hole 9. It is inserted into the mold surface from the rear hollow portion 11 so as to be able to advance and retract. The center of the front end of the rotating pin 10 is a ridge 1
0a, and a spline 12 is provided on the front peripheral side surface. Further, a protruding plate 15 which moves forward and backward by a protruding rod 14 provided in the movable platen 13 is in contact with the rear end.

The spline 12 of the rotating pin 10 has
A transmission gear 16 rotatably supported in the movable mold meshes with a drive gear 18 of an electric motor 17 mounted on a side surface of the movable platen 2.
Can be rotated in any direction by the electric motor 17. In the illustrated example, the electric motor 17 is attached to the side surface of the movable mold 2. However, the electric motor 17 may be installed on the movable platen 13. In this case, the electric motor value 17 is set for each mold. Installation work can be saved.

In the insert molding using the mold, first, in the mold open state, the rotary pin 10 is retracted, and the insert work 7 is inserted into the work set hole 9 at the front part thereof.
The insert work 7 includes a shaft portion having both ends protruding outward from the cavity 3 and a retaining flange 7a integrally formed at the center of the shaft, and a lateral groove is formed at the shaft end.

The insertion is performed until the lateral groove is fitted with the ridge 10a of the rotating pin 10, and the fitting is set so that the insert work 7 rotates together with the rotating pin 10. After the completion of this setting, the movable mold 2 is moved toward the fixed mold 1 to close the mold. When the mold is closed, the insert work 7 projecting from the cavity 3 is accommodated in the receiving hole 8 of the fixed mold 1, and the insert work 7 stands by while being rotatably supported by both mold surfaces of the cavity 3.

Next, after the mold is clamped, the molten resin 19 is injected into the cavity 3 through the sprue 4 and the runner from the nozzle 5a of the injection device 5 in contact with the sprue 4 of the fixed die 1. Since the insert work 7 is positioned laterally with respect to the flow direction, the flow of the resin 19 is divided by the insert work 7 and then merges, and a weld is generated as it is.

Therefore, while the resin 19 has fluidity, the electric motor 17 is operated to transmit the rotational force to the rotary pin 10 via the drive gear 18, the transmission gear 16 and the spline 12. The insert work 7 fitted to the tip is rotated together with the rotating pin 10. This rotation is performed after the resin 19 is injected. In some cases, the rotation may be started immediately before the resin 19 is injected. The resin in the part in contact with the insert work 7 is pulled and stirred by the work side surface.

The agitation area is enlarged by the increase in viscosity accompanying cooling of the resin 19, and the boundary of the resin due to the merge is disturbed, so that the weld is erased. Particularly, as shown in the drawing, when a flange portion 7a for retaining is provided at the center of the insert work 7, stirring is efficiently performed over a wide range due to an increase in the contact area in the resin, and the elimination of weld is further improved. It will be noticeable.

The rotation of the insert work 7 stops before the internal resin solidifies. This is because when the solidification starts, not only the resistance increases, but also the resin is heated by frictional heat, and the resin around the work is deteriorated, so that an insert defect is likely to occur. Therefore, the rotation of the transmission motor 17 is stopped before solidification, the insert work 7 is stopped at the set position, and the state is maintained until the resin is completely cooled and solidified.

After the cooling is completed, the movable mold 2 is moved backward to open the mold. Thereafter, the projecting plate 15 is pressed and moved by the projecting rod 14, and the rotary pin 10 is protruded toward the cavity to release the insert molded product. Do. Therefore, the rotating pin 10 also serves as a protruding pin.

Therefore, even if the flow of the resin in the cavity is divided by the insert work and merged, the weld which is assumed to be generated at the merged portion is wiped out by the stirring of the resin by the rotation of the insert work 7. And the quality of the insert molded product is improved.

[Brief description of the drawings]

FIG. 1 is a view in which a half of a mold used for performing a pressure holding method in insert molding according to the present invention is omitted, and is an explanatory view in a mold open state.

FIG. 2 is an explanatory view at the time of injection filling.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed type 2 Movable type 3 Cavity 5 Injection device 5a Nozzle 7 Insert work 8 Receiving hole 9 Work set hole 10 Rotating pin 12 Spline 16 Transmission gear 17 Electric motor 18 Drive gear 19 Resin

Claims (1)

[Claims] An insert work is rotatably set in a cavity formed by closing a fixed mold and a movable mold, and the insert work is rotated during injection filling of the resin to stir the resin in the cavity. An insert molding method characterized in that the resin is stationary and inserted into a predetermined position in the resin before the resin is solidified.