JPH06262652A - Injection molding method and injection mold - Google Patents

Abstract

PURPOSE:To certainly vent the gas causing the molding inferiority so as not to generate flash. CONSTITUTION:In initial and medium stages filling the cavity 5 formed by a fixed mold 1 and a movable mold 10 with a molten resin, the cavity 5 is filled with the molten resin in such a state that the gas vent hole 15 communicating with the final filling part of the cavity 5 is opened and, in a final stage completing the filling with the molten resin, the gas vent hole 15 is closed by the ejector pin 21 of a product ejecting mechanism 20 to perform filling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a product ejecting mechanism by injecting a molten resin into a cavity formed over a fixed mold and a movable mold, opening the movable mold with respect to the fixed mold. The present invention relates to an injection molding method and an injection molding die for taking out a molded product.

[0002]

2. Description of the Related Art An injection molding method for injecting a molten resin from an injection device into a cavity in a mold to obtain a product having a desired shape is well known in the art without mentioning a literature name. Both the injection device used for implementing this method and the injection mold are well known. The injection mold is generally a fixed mold, a movable mold driven in the mold clamping direction or mold closing direction with respect to the fixed mold, and a product molded in the mold clamped. It is composed of a product ejecting mechanism, that is, an ejector device and the like. A sprue is formed in the fixed mold, and a runner and a gate are formed along the parting lie of the movable mold and the fixed mold. Then, a cavity for forming a product is formed across both molds. Therefore, when the cavity in the mold is filled with the molten resin from the injection device, a product having a desired shape is molded. When the mold is opened by the mold clamping device after waiting for cooling and solidification, the molded product is taken out by the ejector device. When a molded product is obtained as described above, the cavity before being filled with the molten resin is filled with air, but this air is generally excluded from the mating surfaces of the mold parts by the piston action of the filling resin. R. In this way, the air in the cavities, that is, the gas, is released for the time being, but if the removal of the gas is not sufficient, it may cause defects in the molded product. A small gap may be provided on the ring surface.

[0003]

When a gap is provided on the parting surface of the movable mold and the fixed mold, as compared with the case where the gas in the cavity is discharged from the mating surface of each part of the mold,
The advantage of being able to reliably pull out is recognized. However, there is a problem that it is difficult to adjust the gap. For example, if you make the gap relatively wide, it is convenient for removing gas,
Depending on the type of resin to be injected, when the cavity is filled with the molten resin, the molten resin may enter a wide gap and cause burrs. On the other hand, if the gap is narrowed in order to prevent the resin from entering, the result will be the same as in the conventional case where the gas is released from the mating surface of each part of the mold, and the gas release will be worse. If the gas does not escape sufficiently, it may cause defective molding such as burning, short shot, and poor appearance.
Therefore, it is an object of the present invention to provide an injection molding method and an injection molding die in which a gas that causes defective molding can be reliably discharged, but burrs and the like do not occur.

[0004]

In order to achieve the above-mentioned object, the present invention injects a molten resin into a cavity formed between a fixed mold and a movable mold to transform the movable mold into a fixed mold. On the other hand, in the injection molding method in which the mold is opened and the molded product is ejected by the product ejection mechanism, at the initial and middle stages of filling the molten resin, the gas vent hole communicating with the final filling part of the cavity is filled with the resin. In the final stage of completion of filling, the gas vent hole is closed by a product ejection mechanism to fill the gas. The invention according to claim 2 comprises a fixed mold, a movable mold, and a product ejecting mechanism, and a gas vent hole is formed in the final filling portion of the cavity formed in the fixed mold and the movable mold. The gas vent holes are communicated with each other and are opened and closed by the product ejection mechanism.

[0005]

The invention according to claim 2 operates as follows. That is, for example, an injection machine is used to inject the molten resin into the cavity formed over the fixed mold and the movable mold. At this time, in the initial and middle stages of filling the molten resin, the filling is performed with the gas vent hole opened. When the filling progresses and the completion is approaching, the gas vent hole is closed by the product ejecting mechanism to fill. The movable mold is opened with respect to the fixed mold, and the molded product is taken out by the product ejecting mechanism.

[0006]

EXAMPLES Examples of the present invention will be described below. 1A is an overall view showing a part of the first embodiment in a cross section, FIG. 1B is an enlarged cross-sectional view of a main part, and FIG. 1C is an enlarged cross-sectional view of a main part showing another embodiment. It is a figure. As is well known in the art, the mold is composed of a fixed mold 1 mounted on a fixed side mounting plate 34 and a movable mold 10 mounted on a movable side mounting plate 35. A sprue bush 3 is fitted to the fixed mold 1 by a locate ring 2. The sprue bush 3 has a tapered cross-section that increases toward the movable mold 10, and communicates with the first cavity 4 via a gate (not shown). A runner 4 is formed across the fixed mold 1 and the movable mold 10, and the runner key 4 is connected to the cavity 5.
The cavity 5 is located far from the sprue bush 3. Therefore, when filling the molten resin,
The runner 4 will be filled first, and then the cavity 5 will be filled.

The movable mold 10 forming a pair with the fixed mold 1 includes
A plurality of guide holes 11, 12, 13, 14 are bored in the axial direction. And these guide holes 11, 12, 1
The ejector pins 21, 22 of the ejector device 20, which will be described later, the return pin 23, the sprue lock pin 24, and the like are inserted into and guided by 3 and 14, respectively. Cavity 5
In the figure, the lower left end is the filling end portion 5 ', and the guide hole 11 communicates with the filling end portion 5'of the cavity 5. The movable die 10 is provided with a gas vent hole 15. The gas vent hole 15 communicates with the outside and the filling end portion 5 ′ of the second cavity 5. Reference numeral 31 in FIG. 1 indicates a guide bush.
The guide pin 32 is inserted into the movable mold 10 and is guided to the fixed mold 1. Reference numeral 33 indicates a spacer block.

The ejector device 20 includes a protruding plate 25. The ejector pins 21, 22, the return pin 23 and the sprue lock pin 24 are provided on the projecting plate 25. These ejector pins 2
1, 22, the return pin 23 and the sprue lock pin 24 are inserted into the guide holes 11, 12, 13, 14 of the movable mold 10 through the holes formed in the receiving plate 30. A spring 26 is provided between the lower surface of the receiving plate 30 and the upper surface of the projecting plate 25, and the projecting plate 25 is biased downward in the drawing. Therefore, as shown in FIG. 1A, when the movable die 10 is clamped to the fixed die 1, the ejector pins 21, 22, the return pin 24, and the sprue lock pin 23 have upper ends. , Mold lines 1 and 10 parting line P or cavity 5
A gap δ is formed with the lower surface of the.

According to this embodiment, there is a gap δ between the upper end of the ejector pin 21 and the like and the parting line P of the molds 1 and 10 in the mold clamped state. A device for filling the gap δ, for example, an ejector device or a hydraulic piston cylinder unit provided in the injection device is provided. However, the hydraulic piston cylinder unit is not shown in the figure. The ejector device and hydraulic piston cylinder provided in the injection device are
Synchronized with the injection cycle, pressure oil is supplied to the cylinder to push the protruding plate 25 near the completion of filling. When the protruding plate 25 is pushed, the ejector pin 2
The upper ends of 1, 22, the return pin 24, and the sprue lock pin 23 rise to the parting line P, and the ejector pin 21 closes the gas vent hole 15. The injection-molded product can be taken out by further driving the projecting plate 25 by an ejector device or a hydraulic piston cylinder unit provided in the above-mentioned injection device. It can also be carried out as conventionally known. That is, when injection, filling and cooling are over and the mold is opened, the movable mold 10 retracts, and when the mold is near the retract limit,
It is also possible to prevent the receiving plate 30 from retreating by the protruding lot, so that the ejector pins 21 and 22 are relatively advanced and the molded product is ejected from the molds 1 and 10.

Next, an example of formation using the above apparatus will be described. As shown in FIG. 1A, the movable mold 10 is clamped to the fixed mold 1. Then, since the protruding plate 25 is biased downward in the drawing by the spring 25, a gap δ is formed between the upper end portion of the ejector pin 21 and the lower surface of the cavity 5 which is the final filling portion 5 ′. Of course, a gap δ also exists between the upper ends of the other ejector pins 22, the return pins 24 and the sprue lock pins 23 and the parting line P of the molds 1 and 10.
You can Molten resin is injected by a conventionally known injection device including an injection cylinder, a screw that is rotationally driven in the cylinder, and the like. The resin is filled in the runner 4 and then in the cavity 5. Figure 2 (a)
As shown in, when the cavity 5 is filled,
That is, when the filling is almost completed, the ejector device and the hydraulic piston cylinder unit provided in the injection device drive the projecting plate 25 upward in the drawing. Then, the ejector pins 21 and 22, the return pin 24, and the sprue lock pin 23 also rise, and their upper ends reach the parting line P. And ejector pin 21
Seals the gas vent hole 15. The closed state is shown in FIG. Further injection and filling is completed.
After cooling and solidification, the movable mold 10 is opened. The ejector device or the hydraulic piston cylinder unit provided in the injection device drives the projecting plate 25 to take out the product. Alternatively, it is taken out by a conventionally known method as described above.

As described above, according to this embodiment, the gas vent hole 1 is specially provided for degassing during filling.
Since 5 is opened, the gas harmful to molding can be almost completely removed. Then, when the filling is completed, the resin is blocked, so that the molten resin does not leak into the gas vent hole 15 and burrs are not generated.

Although the gas vent hole 15 is provided as a through hole in the movable mold 10 in the above embodiment, it may be formed along the parting line P. For example, as shown in FIG. 1C, a groove 15 ′ with an upward opening is formed on the parting surface of the movable mold 10.
5'can be communicated with the guide hole 11 and the second cavity 5 to form a gas vent hole. Also in this embodiment, when the ejector pin 21 'is lowered, that is, when the resin filling is not completed, the groove 15' is formed in the guide hole 11 and the final filling portion 5'of the second cavity 5 as shown in the figure. Since it is communicated with and, it is possible to fill while degassing as described above. At the final stage of filling, the ejector pin 21 'is driven to close the gas vent hole 15 for filling. According to this embodiment, since the gas vent hole 15 is formed as the groove 15 'whose upper side is open, the effect that the processing is easy and the maintenance is easy can be obtained.

A second embodiment of the invention is shown in FIG. According to this embodiment, in addition to the projecting plate 25, the second projecting plate 25 'is provided so as to be vertically stacked. The elements similar to those of the above-described embodiment are designated by the same reference numerals and will not be described redundantly, but the ejector pin 21 for opening and closing the gas vent hole 15 is attached to the projecting plate 25. The ejector pin 21 penetrates the second projecting plate 25 'loosely and has no direct relationship with the second projecting plate 25'. Therefore, when the tip of the return pin of the ejector pin 22 ′ provided on the second projecting plate 25 ′ comes into contact with the member on the fixed side slightly before the mold is closed, the tip of the ejector pin 22 ′ of the second cavity 5 is formed. Same as the bottom surface. However, since the springs 26, 26 are provided between the protruding plate 25 and the second protruding plate 25 ′,
The protruding plate 25 is pushed down, and the upper end portion of the ejector pin 21 provided on the protruding plate 25 and the parting line P
A gap δ can be formed between and.

In this embodiment, it is obvious that the molding can be carried out in the same manner as the above-mentioned embodiment. According to this embodiment, the ejector pin 2 located at the filling end 5 '
Only 1 is driven to open and close in the vertical direction, and the second projecting plate 25 '
Since the tip end portion of the ejector pin 22 ′ provided in the same is the same as the lower surface of the second cavity 5, the molten resin is filled with the guide hole 1 of the ejector pin 22 ′ when filling.
There is no such thing as a 4 '. In addition, the gas vent hole 15
It is clear that, as in the previous embodiment, can be formed as a groove 15 'along the parting line P.

[0015]

As described in detail above, according to the present invention, at the initial and middle stages of filling the molten resin, the gas vent hole communicating with the final filling portion of the cavity is filled and the filling is completed. When approaching, the gas vent hole is closed and filled by the product ejecting mechanism, so that the gas vent hole can be enlarged and the gas causing defective molding can be surely vented. Even if the gas vent hole is large, the gas vent hole is closed by the product ejecting mechanism to fill the gas when the completion of filling is approaching, so that the molten resin does not enter the gas vent hole and burrs are not generated. Furthermore, since the gas vent hole communicates with the final filling portion of the cavity, it can be vented without causing a gas reservoir, as compared with the conventional gap provided in a simple parting line.

[Brief description of drawings]

FIG. 1 is a view showing a first embodiment of the present invention, (a) is a front view showing a part of the cross section, (b) is an enlarged cross-sectional view of a main part, and (c) is another embodiment. FIG. 3 is an enlarged cross-sectional view of a main part showing.

FIG. 2 is an enlarged cross-sectional view of a main part showing the operation of the present embodiment, in which (a) is a view near the end of filling and (b) is a cross-sectional view schematically showing the final stage.

FIG. 3 is a front view showing a second embodiment of the present invention with a partial cross section.

[Explanation of symbols]

1 Fixed mold 5
Cavity 5'Final filling section 10
Movable mold 15, 15 'Gas vent hole 20 Ejector device (Product ejection device) 21 Ejector pin

Claims (2)

[Claims] 1. A molten resin is injected into cavities 4 and 5 formed over a fixed mold 1 and a movable mold 10,
In the injection molding method in which the movable mold 10 is opened with respect to the fixed mold 1 and the molded product is taken out by the product ejecting mechanism 20, in the initial and middle stages of filling the molten resin, the final filling portion 5'of the cavity 5 is formed. Vent hole 15 communicating with
5 ′ is filled in an open state, and at the final stage of completion of filling, the gas vent holes 15 and 15 ′ are connected to the product ejection mechanism 2
An injection molding method, which comprises closing at 0 and 21 and filling. 2. A final filling section 5'of a cavity 5 formed of a fixed mold 1, a movable mold 10 and a product ejecting mechanism 20 and formed across the fixed mold 1 and the movable mold 10. Gas vent hole 1
5, 5'communicates, and the gas vent holes 15, 15 'are opened and closed by the product ejection mechanism 20.