JPH05177326A - Method for injection-molding product provided hollow part - Google Patents

Abstract

PURPOSE:To improve the production efficiency to prevent entrainment of the air at the time of injecting molten metal by an extremely simple action easily mechanized. CONSTITUTION:The injection of the molten metal (a) into a cavity 3 is started in the condition of taking off a core 4, and at the time of injecting a prescribed quantity of the molten metal (a) from a sprue gate 7 to the front part from the core setting position, the core 4 is set in the cavity 3 so as not to develop eddy at the back side part of the core 4 even if the molten metal (a) is flowed so as to round the core 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of injection molding a product having a hollow portion such as a through hole or a recess.

[0002]

2. Description of the Related Art Generally, when manufacturing a product having such a hollow portion, as shown in FIGS. 5 and 6, a cavity 3 is provided on the facing surface of a fixed mold 1 and a movable mold 2, and a movable mold 2 is provided. An injection molding apparatus having a core 4 fixedly installed on the side is used, and the molten metal a is injected into the cavity 3 through the sleeve 5, the gate runner 6, and the gate 7 with the fixed mold 1 and the movable mold 2 closed. The child 4 is used to form through holes, recesses, and the like. In FIGS. 5 and 6, reference numeral 8 indicates the cavity 3
Is an air vent provided in the upper part of the product, and 9 is a product take-out mechanism.

However, in the case of this injection molding method, the molten metal a injected from the sprue gate 7 collides with the core 4 at a high speed and flows in the cavity 3 so as to wrap around the core 4, so that the back side of the core 4 is closed. 6 causes a swirl flow as shown by arrows A and A'in FIG. 6, and there is a problem that the molten metal a easily entrains air inside. For this reason, conventionally, as a technique for coping with this, a technique as disclosed in Japanese Patent Laid-Open No. 62-118944 has been proposed.

In this technique, a heat-resistant polymer organic material is applied to the confluent portion (for example, the back side of a core) of the melt in the cavity where a swirl is likely to occur, and the heat-resistant polymer organic material is heated by the heat of the melt injected into the cavity. Is evaporated, and the ascending air current generated at that time causes the air in the confluence of the molten metal to be smoothly discharged to the outside.

[0005]

However, in the case of the above-mentioned conventional injection molding method, the work of applying the heat-resistant polymer organic material has to be carried out every time the injection molding is carried out.
There is a problem that the preparation work for molding takes time and the production efficiency is poor.

Therefore, the present invention is intended to provide an injection molding method of a product having a hollow portion with high production efficiency by preventing entrapment of air at the time of injecting molten metal by an extremely simple operation which is easy to mechanize. Is.

[0007]

Means for Solving the Problems As a means for solving the above-mentioned problems, the present invention starts injection of molten metal into a cavity with a core removed, so that the molten metal is injected from a spout gate to a position higher than that of the core. The core was installed in the cavity when a predetermined amount of molten metal was injected forward.

[0008]

[Operation] When the injection of the molten metal into the cavity is started with the core removed, the molten metal does not collide with the core.
A predetermined amount is filled in front of the gate without generating swirl. If the core is placed in the cavity after this, the molten metal flows in the cavity so as to wrap around the core, but at this time the molten metal has already been filled in a predetermined amount from the sprue gate in front of the core installation position. Also, the molten metal is filled in every corner of the cavity without generating a vortex on the back side of the core.

[0009]

Embodiments of the present invention will be described below with reference to FIGS. The same parts as those shown in FIGS. 5 and 6 are designated by the same reference numerals.

1 to 4 show an example of an injection molding apparatus using the injection molding method of the present invention, FIGS. 1 and 2 show the first half stage of injection of the molten metal a, and FIGS. Shows the latter half of the injection.

First, the structure of this injection molding apparatus will be described.

Reference numeral 1 is a fixed die fixedly installed on a base member (not shown), and 2 is a movable die which is opened and closed with respect to the fixed die 1 by the power of an actuator (not shown).
Is a substantially disc-shaped cavity provided on the opposing surfaces of the fixed die 1 and the movable die 2, 5 is a pouring sleeve, 6 is a sprue runner, and 7 is a sprue gate. The movable die 2 includes a plurality of push-out pins 10, a push-out plate 11 that supports the push-out pins 10, and an actuator (not shown) that moves the push-out plates 11 back and forth.
In addition, a core 4 for forming a hollow portion such as a through hole or a recess in the center of the product, and an actuator 12 such as a hydraulic cylinder for moving the core 4 forward and backward are provided.

The core 4 is a support hole 1 formed in the movable mold 2.
3 is slidably fitted to the center of the cavity 3 and is moved forward (projected) or retracted by the power of the actuator 12. Further, the actuator 12 is electrically connected to a limit switch provided on a plunger (not shown) for pushing out the molten metal a poured into the sleeve 5, and the plunger is set to a set position (only about half of the total injection amount into the cavity 3). Position where molten metal is injected)
When moving forward, the core 4 is moved forward. In the figure, 14 is an overflow provided in a concave shape in the upper part of the cavity 3 of the facing surfaces of the fixed mold 1 and the movable mold 2, and 8 is an air vent provided continuously to this overflow 14.

Next, the operation of this injection molding apparatus and the injection molding method according to the present invention will be described.

First, the movable mold 2 is advanced by an actuator (not shown) to close the fixed mold 1 and the movable mold 2, and the actuator 12 retracts the core 4 as shown in FIGS. 1 and 2 (removed from the cavity 3). State).

From this state, the molten metal a is poured into the sleeve 5, and a plunger (not shown) is operated to inject the molten metal a into the cavity 3 through the gate gate runner 6 and the gate gate 7. At this time, since the core 4 is retracted (removed) from the inside of the cavity 3, the molten metal a injected from the sprue gate 7 does not generate a vortex and the inside of the cavity 3 is indicated by an arrow F in FIG. So that it flows almost straight.

In this way, the injection of the molten metal a continues, and the plunger in the sleeve 5 advances to the set position,
When a predetermined amount of molten metal a is injected from the gate 7 to the front of the core installation position, the limit switch provided on the plunger operates, and the actuator 12 moves the core 4 forward as shown in FIGS. The core 4 is installed in the center of the cavity 3. Then, the molten metal a ejected from the gate 7 is split into two as shown by an arrow G in FIG.
However, since the back side of the core 4 is already filled with the molten metal a as described above, no swirl occurs in this portion and no air is entrained. When the injection is continued in this way, the molten metal a gradually becomes the cavity 3
The air in the cavity 3 is smoothly discharged to the outside through the overflow 14 and the air vent 8.

When the filling of the molten metal a into the cavity 3 is completed, the movable mold 2 is opened after the molten metal a is solidified, and the product is taken out of the cavity 3 by the take-out mechanism 9.

[0019]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, when the molten metal is injected into the cavity with the core removed, a predetermined amount of the molten metal is injected from the spout gate forward of the core installation position. Since the core is installed in the cavity, even if the molten metal flows around the core when the core is installed, no vortex is generated in the back side of the core.
It becomes possible to prevent the entrapment of air during the injection of the molten metal without requiring complicated forming preparation work. Further, since the entrapment of air can be prevented by an extremely simple mechanical operation, it is possible to improve the production efficiency by mechanization.

[Brief description of drawings]

FIG. 1 is a sectional view taken along line BB of FIG. 2 showing an embodiment of the present invention.

FIG. 2 is a sectional view showing the same embodiment.

FIG. 3 is a sectional view taken along the line CC of FIG. 4 showing the same embodiment.

FIG. 4 is a sectional view showing the same embodiment.

FIG. 5 is a cross-sectional view showing a conventional general technique.

6 is a cross-sectional view taken along the line DD of FIG.

[Explanation of symbols]

3 ... cavity, 4 ... core, 7 ... gate gate, a ... molten metal.

Claims (1)

[Claims] 1. The injection of the molten metal into the cavity is started with the core removed, and the core is set in the cavity when a predetermined amount of the molten metal is injected from the spout gate to the front of the core installation position. An injection molding method for a product having a hollow portion, characterized in that