JPH0462120A - Method and apparatus for injection molding - Google Patents

Abstract

PURPOSE:To obtain a large injection flow rate by a low injection pressure and to prepare a molded item with precise shape and dimension by injecting a molten resin in a cavity through a number of fine holes of a multihole member forming a part of a wall dividing the cavity. CONSTITUTION:A molten resin kept at a specified temp. passes through a path 10b from a nozzle hole 18a of an injection apparatus 18 and flows into fine holes of a multihole member 12 through a manihold chamber 10a and flows in a cavity A. The molten resin is filled in the cavity A and a molded item P is molded. A movable mold 8 moves a little to the left to form a gap B between the movable mold 8 and a fixed mold 4. By this movement, the molten resin in the fine holes of the multihole member 12 are drawn into a fibrous shape and a number of these resin fibers are stretched over between the molded item P and the fine holes. Air at a low temp. is fed in a blast nozzle 20a from a cooling air feeding apparatus 20 and the air cools and solidifies a number of resin fibers and is then evacuated out of the molds 4 and 8. Mold opening is performed and the molded item with a number of fibrous resin are separated and the molded item is taken out.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to an injection molding method and apparatus.

(B) Conventional technology When manufacturing resin molded products with precise shapes and dimensions by injection molding, it is desirable to inject at as low an injection pressure as possible in order to suppress the generation of distortion. A low pressure injection method is used for this purpose. The molten resin injected from the injection device passes through a portion of the sprue within the mold, further passes through the runner section and the gate section, and is injected into the cavity at low pressure. This makes it possible to manufacture molded products with precise shapes and dimensions.

(c) Problems to be Solved by the Invention However, in the conventional low-pressure injection method as described above, the molten resin passes through the runner section and the gate section, which have a small cross-sectional area of the flow path, so the injection flow rate is reduced due to flow resistance. This meant that it was necessary to inject and fill the mold with molten resin over a long period of time. In addition, when manufacturing resin molded products with precise shapes and dimensions using normal injection molding methods without using low-pressure injection methods, the time required to inject and fill the mold is short, but the distortion of the molded products In order to remove this, the long cooling cycle in the mold is long, making it difficult to increase production efficiency. The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention is characterized in that the molten resin is injected into the cavity through a porous member having a large number of pores, without passing through the runner section and gate section, which have a small cross-sectional area of the flow path. , solve the above problems. That is, in the injection molding method of the present invention, a part of the wall that partitions the cavity (A) of the mold (4, 8) is formed by a porous member (12) having a large number of pores,
Through this, the molten resin is injected into the cavity (A), and by slightly opening the molds (4 and 8) after injection a, the gap (B) between the molded product and the porous member (12) is created.
After forming a large number of filamentous resin in the mold (4), blowing gas into the gap (B) and cooling and solidifying the filamentous resin.
・8) is opened to take out the molded product.

Furthermore, the injection molding apparatus of the present invention for carrying out the above method includes a mold (4, 8) and an injection device (18) capable of injecting molten resin into the cavity (A) formed thereby. ), and a space (4a) that communicates with the cavity (A) is formed in the stationary mold (4), and a cavity (4a) is formed in this mold.
A) is provided with a porous member (12) that forms part of a wall that partitions the molten resin passageway (4a or 10).
a, 10b) and the cavity (A) are formed, and the cooling gas supply device (20
) are provided in the mold (4, 8), and the injection nozzle (2
The tip of 0a) is connected to the fixed side mold (4) and the movable side mold (4).
8) is open toward the mating surface.

A stepped cylindrical manifold member (10) is provided in the space (4a) so that the porous member (12) is supported by the manifold member (10), and a heater member ( 14) may be provided. Note that the symbols in parentheses may be omitted. Note that the symbols in parentheses indicate corresponding members in the embodiment.

(E) Function The molten resin is injected into the cavity of the mold through the pores of the porous member through the resin passage to form a molded product. The porous member is provided with a large number of pores serving as resin passages corresponding to gates that communicate the resin passage with the cavity, and the molten resin is injected into the cavity through these many pores. A large flow rate of molten resin can be injected even under conditions of low pressure resistance. After injection, the mold is opened slightly and a large number of thread-like resin is formed in the minute gaps between the porous member and the molded product, and gas is blown into this to form the resin in the part corresponding to the gate. It is cooled and solidified. By opening the mold, an operation equivalent to gate cutting is performed and the molded product can be taken out.

(f) Examples Section 1 shows examples of the present invention. A cylindrical fixed side mold 4 is fixed to a fixed mold mounting plate 2. Fixed foot mold mounting plate 2
is fixed to a fixed platen (not shown). A movable mold mounting plate 6 is arranged on the left side in the figure, facing the fixed mold mounting plate 2, and a movable mold 8 having a "convex" cross section is fixed to this. The movable mold mounting plate 6 is attached to a movable platen (not shown), and thereby moves the movable mold 8 between the illustrated mold closing position where it contacts the fixed mold 4 and away from the fixed mold 4. It is possible to move it between the mold opening position on the left in the figure. A space 4a is formed within the stationary mold 4, and a stepped cylindrical manifold member 10 is disposed within the space 4a. The manifold member 10 is a fixed mold mounting plate 2
is fixed. The manifold member 10 is formed with a stepped cylindrical manifold chamber 10a at the left end thereof, and a resin passage 10b communicating with the manifold chamber 10a and communicating with the nozzle hole 18a of the injection device 18. A porous member 12 is fitted and supported in the larger diameter cylindrical portion of the manifold chamber 10a, and most of the left end side of the porous member 12 in the figure forms a wall portion that partitions the cavity A. That is, the wall surface that partitions the cavity A is the fixed side mold 4. It is formed by a movable mold 8 and a porous member 12. The porous member 12 is provided with a large number of pores that communicate between the cavity A and the manifold chamber 10a, and these pores form resin passages corresponding to gates. Porous member 12 is easily replaceable. A heater 14 is fixed to the outer periphery of the manifold member 1o, and a ring-shaped spacer 16 made of a heat insulating material is arranged between the manifold member 10 and the fixed mold mounting plate 2. On the outer periphery of the mating surfaces of the stationary mold 4 and the movable mold 8, an injection nozzle 20a is arranged with one end opening toward the mating surface, and the other end of the injection nozzle 20a is connected to a cooling air supply device. 20.

Next, the operation of this embodiment will be explained using FIGS. 2 to 6. In the mold-closed state shown in FIG. 2, a mold-closing force is acting on the movable mold mounting plate 6. Further, the heater 14 is energized to heat the manifold 10, and the molten resin maintained at a predetermined temperature passes through the resin passage 10b from the nozzle port 18a of the injection device 18, passes through the manifold chamber 10a, and enters the porous member 12. flowing into the pores. In the third section, the molten resin begins to flow into the cavity A. As shown in Figure 4, the molten resin fills the cavity A, and the molded product P
is formed. Next, the movable mold 8 moves slightly to the left in the figure from the position shown in FIG. 4, and the movable mold 8 and the fixed mold 4
A gap B is formed between them as shown in FIG. Due to this movement, the molten resin in the pores of the porous member 12 is stretched into threads, and many threads of this resin are stretched between the molded product P and the pores. In this state, low temperature air is supplied from the cooling air supply device 20 to the injection nozzle 20a. The air is discharged from the molds 4 and 8 after cooling and solidifying the numerous resin threads. Next, as shown in FIG. 6, the mold is opened, and the molded product is separated from the molded product along with many filamentous resins, and the molded product is taken out. Next, the movable mold 8
will return to the mold-closed position shown in FIG. 1 and repeat the same cycle.

In the above description, the porous member 12 is shown as being plate-shaped, but it may be shaped in accordance with the shape of the molded product, for example, in the shape of a bowl.

In addition, the nationally designated side mold 4 is a split type, and the porous member 1
2 can also be made easier to attach and remove.

In addition, in the above description, the manifold member 10 is provided in the space 4a in the movable mold 4, but the porous member 12 is fixed to the movable mold 4 without providing this. The heater 14 may be provided in the movable mold 4.

Further, in the above description, the cooling air supply device 20 uses air, but nitrogen gas or the like may also be used.

(G) As described in detail, according to the present invention, the molten resin is injected into the cavity through the many pores of the porous member that forms part of the wall that partitions the cavity. A large injection flow rate can be obtained with low injection pressure, and molded products with precise shapes and dimensions can be manufactured in a short time. Since the porous member is easily replaceable, even if the color of the resin used is changed, the molding operation can be restarted within a short time by replacing the porous member. Also,
Ultra-low pressure molding becomes possible, and a highly rigid injection molding machine is not required to manufacture precision molded products, so the injection molding machine can be made smaller.

[Brief explanation of drawings]

Fig. 1 is a partially cross-sectional view of an injection molding apparatus according to an embodiment of the present invention, Figs. 2 to 4 are partially cross-sectional views showing how the molten resin is injected, and Fig. 5 is a partially cross-sectional view of the injection molding apparatus according to an embodiment of the present invention. FIG. 6 is an enlarged sectional view showing a situation in which the mold is slightly moved in the mold opening direction and cooling air is blown into the mold, and FIG. 6 is a diagram illustrating the state in which the molded product is taken out. 2...Fixed mold mounting plate, 4...Fixed side mold, 6...
- Movable mold mounting plate, 8... Movable side mold, 10... i manifold member, 12... Porous member, 14... Heater, 18... Injection device, 20... Cooling gas supply Device,
A...Cavity, B...Gap. Diagram

Claims (1)

[Claims] 1. A part of the wall that partitions the cavity (A) of the mold (4, 8) is formed by a porous member (12) having a large number of pores, through which the inside of the cavity (A) is formed. The gap (B) between the molded product and the porous member (12) is filled by injecting the molten resin into the mold and opening the molds (4 and 8) slightly after the injection is completed.
) to form a large number of filamentous resin, blow gas into the gap (B), cool and solidify the filamentous resin, and then mold (
4.8) An injection molding method characterized by opening and taking out the molded product. 2. In an injection molding device that includes molds (4 and 8) and an injection device (18) capable of injecting molten resin into the cavity (A) formed by these, the fixed side A space (4a) communicating with the cavity (A) is formed in the mold (4), and the cavity (A)
A porous member (12) forming a part of a wall that partitions the molten resin passageway (4a or 10) is provided in the porous member (12).
a, 10b) and the cavity (A) are formed, and the cooling gas supply device (20
) are provided in the mold (4, 8), and the injection nozzle (2
The tip of 0a) is connected to the fixed side mold (4) and the movable side mold (4).
8) An injection molding device characterized by being open toward the mating surface of item 8). 3. A stepped cylindrical manifold member (10) is provided in the space (4a), the porous member (12) is supported by the manifold member (10), and a heater is installed on the outer circumference of the tube of the manifold member (10). 3. Injection molding device according to claim 2, further comprising a member (14).