JPH10315264A - Method for insert molding by press-fitting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of positional deviation of an insert work or a weld due to injection charging pressure easily generated in the case of insert molding by press-fitting the work in a resin in a cavity in which its casting amount is limited. SOLUTION: An insert work 4 is previously waited at a side face of a cavity 15. Resin 5 of quantity of the degree that a necessary predetermined space for secondarily filling the resin 5 in the cavity 15 is injected. The insert is moved forward in the resin 5 and press-fitted while the resin 5 has fluidity. The resin 5 is densely charged in the entire cavity by its pressure and molded. The insert is press-fitted in the resin at a time point when the injection is stopped or its speed is decelerated. Dwelling is conducted subsequent to the press-fitting of the insert.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

In this type of molding method, an insert work is previously inserted into a cavity of a mold, and the cavity is injected with a resin to embed the insert work in the resin. .

In such insert molding, since the insert work is cantilevered, the gate position is set as close as possible to the work holding portion by the die. However, in the case where the insert work is made of a plate or the like and has a small thickness and is bent by the filling pressure of the resin and the tip may appear on the surface of the molded product, the both ends of the tip are held by pins. I have.

[0004] In the holding by the pins, the pin is retracted into the mold by the filling pressure so that a pin mark does not remain as a hole in the molded product. Since it forms part of the mold surface, it is difficult to completely remove the trace of the tip surface from the surface of the molded product.In addition, when the insert work is long, it is difficult to pull out the above pin, so that A weld line due to the pin may be generated, which may even impair the appearance of the molded product.

[0005] As a means for solving such a problem, it is conceivable that after the resin is injected and filled into the cavity, the insert work is inserted into the resin by press-fitting while the resin maintains a fluid state. However, it is extremely difficult to press-fit surplus insert work into the cavity filled with the resin, and unless the resin corresponding to the volume of the insert portion is pushed out of the cavity, the insert cannot be deeply inserted to a predetermined position.

The present invention was conceived in order to solve the above-mentioned problem in insert molding, and an object of the present invention is to inject and inject a resin into a cavity, and then insert an insert work into the cavity to form a resin. Even if it is press-fitted, a new press-fit insert that does not cause displacement of the insert work, does not cause problems due to internal distortion of the resin due to press-fitting, and can also prevent welds and flow marks. It is to provide a molding method.

[0007]

SUMMARY OF THE INVENTION According to the present invention, an insert work is made to stand by in advance on a side surface of a cavity, and the resin has such a degree that a space required for the resin to be secondarily filled in the cavity is created. The amount is injected, and while the resin has fluidity, the insert portion is moved forward into the resin and press-fitted, and the pressure is used to tightly fill the entire cavity with the resin to perform molding.

Further, the present invention is also such that the press-fitting of the insert portion into the resin is performed when the injection is stopped or the speed is reduced, and the pressure is maintained following the press-fitting of the insert portion.

In such an insert molding method, even if the flow region of the resin narrows due to an increase in the amount of insert work inserted and an increase in the solidified layer with the passage of time, the amount of injected resin is reduced by press-fitting of the insert work. Is limited to the amount that fills the cavity secondarily to complete the molded product, and part of the resin moves relative to the insert work until completion, so the displacement of the insert work due to press-fitting is limited. Of course, internal distortion of the resin, welds, flow marks, and the like hardly occur.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a vertical molding machine capable of carrying out the present invention.
Is an insert device installed on the machine base at the side of the mold clamping device 1, and 3 is an injection device.

The above-mentioned mold clamping device 1 comprises a fixed platen 11 on a machine base,
A mold 13 that opens and closes in the vertical direction is provided between the movable platen 12 and the movable plate 12 above and below the movable platen 12. The insert device 2 is located on a side of the mold 13. The injection device 3 is located on the side of the mold opposite to the insert device 2 with the nozzle 31 facing the gate 14 provided on the parting line.

The above-mentioned insert device 2 is provided with a chuck member 2 at the tip of a piston 22 of a cylinder 21 operated by air or hydraulic pressure.
3, the rear end portion of the insert work 4 is held by the chuck member 23, and the insert work 4 is pressed into the cavity 15 from the parting surface of the mold 13.

In the insert molding by the molding machine, first, the tip of the insert work 4 is set between the molds 13 by the insert device 2 in the mold open state, and the tip is closed by the mold closing so that the cavity 15 faces the gate. Wait to be located at.

Next, after the clamping of the mold 13 is completed, FIG.
As shown in (A), the nozzle 31 is touched, and the molten resin 5 is injected and injected from the gate 14 into the cavity 15. The injection of the resin 5 is not performed until the cavity 15 is completely filled as in the case of ordinary injection molding, but is limited to such an amount that a required space necessary for the resin 5 to secondarily fill the cavity 15 is generated. The reference is the amount obtained by subtracting the volume equivalent of the insert portion 41 from the cavity volume,
Actually, there is a certain difference depending on the volume, volume or resin.

When the injection of the resin into the cavity 15 is completed, the insert work 4 is moved forward in the cavity 15 toward the gate 14 by the extension of the piston 22 and press-fitted. The press-fitting of the insert work 4 is performed by stopping the injection and injection of the resin 5, but may be started at a time when the injection speed is reduced in some cases. The resin 5 injected into the cavity 15 is a cooled mold 1
3, a skin layer is immediately formed on the contact surface with the mold surface, and the skin layer increases in thickness to form the solidified layer 52. However, since the resin is a poor conductor against heat, there is a time until the whole is solidified, and the central portion is in a high temperature state and has fluidity.

Therefore, immediately after the injection is completed, when the insert work 4 is pressed into the cavity 15 toward the gate 14 by the extension of the piston 22, the insert work 4 is moved to the center of the resin 5 as shown in FIG. The resin 5 relatively fills the space of the cavity 5 by that amount. Then, when the press-fitting of the insert work 4 reaches a predetermined position, the pressure is maintained.

It may be difficult to maintain the pressure after the press-fitting of the work smoothly depending on the shape of the molded product and the material resin.
In such a case, as shown in FIG.
If processing is performed so that a occurs, the pressure can be maintained by pushing the resin into the gap 13a. In addition, it can also be used as a control when the resin is excessively injected.

To insert the insert work 4 to a predetermined position, a certain pressing force is required. This is because the flow region in the resin 5 is narrowed due to the increase in the insertion amount and the increase in the solidified layer with the passage of time, so that the press-fitting requires more force than at the start of insertion.

Finally, the insert work 4 finally fills the cavity 5 with the resin 5 and fills the entire cavity tightly as shown in FIG. 2 (C) to complete the molding. Since the pressure on the resin 5 and its reaction force until the completion thereof are reduced by the relative movement between the insert work 4 and the flow portion 51, there is almost no effect of the press-fitting on the resin 5 in the cavity, and In addition to the displacement of the work 4, internal distortion of the resin due to press-fitting hardly occurs, and the occurrence of welds and flow marks, which tend to occur in insert molding, is prevented.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a molding machine capable of performing an insert molding method by press-fitting according to the present invention, in which a mold portion is longitudinally sectioned.

FIG. 2 is an explanatory view showing steps of an insert molding method of the present invention in order.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold clamping device 2 Insert device 3 Injection device 4 Insert work 5 Resin 13 Mold 14 Gate 15 Cavity 31 Nozzle 41 Insert part 51 Flowing part 52 Solidified layer

Claims (2)

[Claims] 1. An insert work is made to stand by in advance on a side surface of a cavity, and a resin amount is injected into the cavity so that a required space necessary for secondary filling of the interior with the resin is injected. A press-fitting insert molding method characterized in that the insert portion is moved forward into the resin and press-fitted, and the resin is densely filled in the entire cavity by the pressure to perform molding. 2. The press-fitting of the insert portion into the resin is as follows.
2. The insert molding method by press-fitting according to claim 1, wherein the press-fitting is performed at the time of stopping the injection or when the speed is reduced, and then holding the pressure following the press-fitting of the insert portion.