JPH10156883A - Manufacture of sandwich molding and mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sandwich molding of a densely filled core layer by closing a mold in such a manner that the cavity part of the mold is diminished when the flow front of the core layer reaches near the flow front of a skin layer, with the help of a mold member making up a freely stretchable cavity part. SOLUTION: This mold for manufacturing a sandwich molding consists of three stacked layers such as a top force 50 and a bottom force 54 of a flat plate shape and an intermediate molding part 52 interposed between the former two. The intermediate molding part 52 is encircled with a first split part 52a, a second split part 52b and a side wall member which freely come into contact with and separate from both forces 50, 54 in the injection direction, and has a freely expandable cavity part. Part of an outer core material which forms a skin layer is injected into a cavity 37 and then, a core material is successively injected into the skin layer. Further, when the flow front of the core layer reaches near the flow front of the skin layer injected ahead of the former, a skin material is successively injected and the mold is clamped upto a specified position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sandwich molded article for highly filling a core layer in sandwich molding using an injection molding machine, and a mold therefor.

[0002]

2. Description of the Related Art Conventionally, as shown in Japanese Patent Application Laid-Open No. 4-126212, in conventional sandwich molding, low-temperature cooling water is caused to flow through cooling passages 106 of split dies 101 and 102, and a cooling passage 107 of split Then, when high-temperature cooling water is allowed to flow and the skin layer material 200 is injected from the gate 108 into the main body forming portion 110, the skin layer material 200 is solidified to form a skin layer.

At this time, the lower piece forming portion 11 having a low flow resistance is used.
A large amount flows into the two sides, and a small amount of the skin layer material is contained in the mounting part forming part 113 side. Next, the core layer material 300 is placed in the skin layer material 200 of the main body forming portion 110 by the gate 108.
Is injected, the main body forming portion 110 and the mounting portion forming portion 113
The skin layer material 200 entered therein is divided into split molds 101 and 102.
Since the mold surface temperature of the mold surface is low, it cools and solidifies quickly, and its thickness increases. On the other hand, the mold surface of the split mold 113 is gradually cooled and solidified because the mold surface temperature is high, so that the thickness is reduced (FIGS. 16 and 17).

[0004]

However, at the time of sandwich molding, the temperature of the mold surface at the portion where the skin layer is to be made thicker is lower than that at the portion where the skin layer is to be made thinner, and the softened skin layer material is injected into the mold. Then, by injecting the core layer material in a softened state into the skin layer material, since the skin layer has a different thickness at an arbitrary portion, the split molds are kept at different temperatures, There was a problem that the distortion of the formed molded article was large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a flow front of a core layer near a flow front of a skin layer using a mold member constituting a scalable cavity portion. It is an object of the present invention to obtain a sandwich molded product having a highly filled core layer by closing the mold so as to reduce the cavity portion of the mold when it reaches, and to obtain a molded product with less distortion.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a mold is previously opened to form a cavity portion, and then a skin layer having a smooth surface is formed. The core material is first injected only partially into the cavity, and then the core material forming the core layer is injected into the outer core material, and the flow front of the core layer causes the flow of the skin layer injected first. After reaching the vicinity of the front, the skin material is continuously injected, and then the mold is tightened to a predetermined position. In the second invention, the outer core material for forming the skin layer is first partially filled in the cavity. After injecting, the core material forming the core layer is injected into the skin layer, and at the same time, the mold is opened to expand the cavity, and after the inner core material, the outer core material is injected again.
The mold was clamped to a predetermined position. According to a third aspect of the present invention, there is provided a sandwich molding mold formed by superimposing three layers by an upper mold having a flat plate shape and an intermediate mold interposed between the lower molds, wherein the intermediate mold is A first mold and a second mold that are freely movable in and out of the injection direction, and the first and second molds;
In the fourth aspect of the present invention, an upper mold and a lower mold having a flat plate shape are formed by being surrounded and bent by a side wall member opposed to a step forming position of the mold so as to be expandable and contractable. What is claimed is: 1. A sandwich molding die formed by superimposing three layers with an intermediate die interposed therebetween, wherein said intermediate die comprises a pair of movable dies which can freely come and go in a direction intersecting the injection direction, and a fixed platen. And the side wall members respectively mounted on the movable plate and the movable plate to form an expandable and contractable cavity portion.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a method of manufacturing a sandwich molded product according to the present invention.

FIG. 1 is a sectional view of a mold showing an injection state according to the present invention, FIG. 2 is a front view showing a part of an injection molding machine cut away, and FIGS. 3 to 5 show cases where a mixing nozzle is used. FIG. 6 to FIG. 9 are explanatory views of the injection operation using a mold capable of expanding and contracting a cavity in the injection direction, and FIG. 10 to FIG. 15 are directions intersecting the injection direction. FIG. 7 is an explanatory view of an injection operation using a mold capable of expanding and contracting a cavity.

First, the mold used in this embodiment is shown in FIG.
9 as well as types as shown in FIGS. 10 to 15. First, the A-type mold will be described with reference to FIG. 6. The upper mold 50 and the lower mold 54 each having a flat square or rectangular shape, and the upper and lower molds 5.
The molds 50, 52, and 54 are formed so as to overlap three layers. Further, the intermediate mold 52 is provided with a fixed mold 7.
, A second mold 52b mounted on the movable platen 8 to form the movable mold 9, and a pair of side wall members 56a, 56b. The movable platen 8 having the second mold 52b can be moved back and forth in the injection direction with respect to the fixed platen 5 having the first mold 52a.

The fixed mold 7 includes an upper mold 50 and a lower mold 5.
4 and a first mold 52a, all of which are mounted on the fixed platen 5. The first mold 52a is provided with a hot runner 27, and the injection unit 2 (2A, 2A,
B).

Both end surfaces of the first mold 52a and the second mold 52b are stepped, and a pair of side wall members 56 (56a, 56b) are elongatedly engaged with the step forming position in the injection direction. They are arranged facing each other. The side wall member 56 (56
a, 56b) are fixed to the step forming position of the first mold 52a, and the second mold 52b is fixed to the inner surface 58 of the side wall member 56.
It moves back and forth along the (cavity 37 side) in the injection direction, and is configured to be able to expand and contract the cavity 37 surrounded and bent between the first mold 52a, the second mold 52b, and the side wall member 56. In order to control the cavity 37 to have an appropriate volume, a position sensor (not shown) for controlling the front-rear position of the movable plate 8 having the movable mold 9 is provided.

Next, a B-type mold will be described with reference to FIG. Upper mold 5 having a flat square or rectangular shape
0 and a lower mold 54, and an intermediate mold 52 interposed between the upper and lower molds 50 and 54. The molds 50, 52, 54 are formed in three layers.

Further, the intermediate mold 52 interposed between the upper and lower molds 50 and 54 is divided into a side wall member 60a mounted on the fixed platen 5 and an inner side surface 62 of a side wall member 60b mounted on the movable platen 8. And a pair of movable molds 9a and 9b arranged so as to be able to freely contact and separate in a direction intersecting with the injection direction along.

On the other hand, the fixed mold 7 includes an upper mold 50 and a lower mold 5.
4 and a side wall member 60a, all of which are mounted on the fixed platen 5. The hot runner 27 is provided on the side wall member 60a, and the injection unit 2 (2A, 2A,
B).

Both end surfaces of the movable molds 9a and 9b are formed with steps, and a pair of side wall members 60 (6
0a, 60b) are engaged with each other and are opposed to each other in the injection direction. The cavity 37 is surrounded and bent by the pair of side wall members 60a and 60b and the pair of movable molds 9a and 9b, and the cavity 37 can be expanded and contracted by the left and right movement of the movable molds 9a and 9b. In order to control the cavity portion 37 to have an appropriate volume, cylinders having piston rods (not shown) are provided on both outer sides of the movable molds 9a and 9b. 37
Is to be scaled.

Next, the injection molding machine 1 will be described. Code 5
Reference numeral denotes a fixing plate of a mold clamping device (not shown) provided on the left side (front side) of the head 3 of the injection molding machine 1 in the figure. The fixed platen 5 has an opening 6 of a predetermined size. In this opening 6, a sandwich forming block 10 interposed between a fixed mold 7 and the injection unit 2 can move back and forth on a support base 8. It is arranged in.

The injection unit 2 is composed of two injection units 2A and 2B. The injection units 2A and 2B are installed so as to form an eight-letter shape as shown in FIG.
The injection units 2A and 2B are mounted on a movable table 11 (11A, 11A).
B) Hydraulic cylinders 4A, 4A
The injection nozzles 12A and 12B are provided so as to be slidable back and forth between a position where the injection nozzles 12A and 12B are in contact with the contact portion 13 of the sandwich molding block 10 and a position where the injection nozzles are separated by appropriate means such as B. The moving table 11 (11A, 11B) and the sandwich molding block 10 are arranged on the common moving table 11, and the front end contact portion of the mixing nozzle 35 is fixed to the fixed die 7.
In order to be able to abut against the spool 14, a dedicated hydraulic cylinder 4 (4A, 4B) can slide back and forth.

Here, the sandwich molding block 10
The one having the structure of the mixing nozzle 35 therein will be described with reference to FIG. The multi-material molding block 10 includes:
A block nozzle 15 that contacts the spool 14 of the fixed mold 7, a tip block 16 that screw-holds the block nozzle 15, a first block 17, a second block 18, a needle valve 19, and a needle valve driving cylinder 20. It is configured.

As described above, at the tip of the multi-material molding block 10, that is, at the portion of the block nozzle 15 and the tip block 16, a cylindrical piece 21 is interposed at the tip of the first block 17, and concentric inner and outer rings are provided. A first injection unit 2A and a second injection unit 2B are formed to form a resin passage.
The molten resin respectively injected from the
7 is injection-filled in a predetermined amount, and a molded article having inner and outer layers is sandwich-molded.

Reference numeral 22 denotes an inside passage, and 23 denotes an outside passage. Inside passage 22 and outside passage 23
Is communicated from the second injection unit 2B to the block nozzle 15 having concentric inner and outer annular resin passages via the second block 18, the first block 17, and the end block 16.

The inner and outer annular resin passages provided in the block nozzle 15 communicate with the outer passage 23 and are located outwardly in communication with the outer annular passage 25 and the inner passage 22 and are located inwardly. The inner annular passages 24 join together at a distal end port 26 of the blocking nozzle 15 and are connected to a hot runner 27.

A needle valve 19 connected to a needle valve driving cylinder 20 provided at the rear end of the sandwich forming block 10 and moving back and forth to open or close the inner annular passage 24 is provided with a needle valve 19 of the sandwich forming block 10. It is arranged on the axis.

Reference numeral 28 denotes a shut-off valve 28, which is rotatably disposed on the injection nozzle 12A of the first injection unit 2A and opens and closes a resin passage hole 29 provided in the injection nozzle 12A. Has become.

Although not shown in this embodiment, only the periphery of the resin passage formed in the fixed mold 7 is locally heated while maintaining the two molds 7 and 9 at the solidification temperature of the resin. Although the embodiments have been described as the so-called hot runners 27, 34A, and 34B, the invention is not limited to this, and a cold runner (the periphery of the resin passage is not locally heated) may be used by using the sandwich molding block 10 of the present embodiment. . A sheath heater 40 is provided around the inner passage 22 and the outer passage 23 formed in the sandwich molding block 10.
The resin passing through 2 and 23 is heated to an appropriate temperature.

Next, a method of manufacturing a sandwich molded product using an A type or B type mold superimposed on three layers will be described.

First, the case of molding a molded article having an outer layer and an inner layer using an A-type mold will be described with reference to FIGS. First, the first mold 52a (which forms a part of the fixed mold 7) and the second mold 52b (movable) using an appropriate mold clamping device (not shown) (for example, using a clamping means such as a direct pressure type or a toggle type). The mold 9) is opened and the mold is clamped. Here, the retreat distance of the first mold 52a is slightly increased with respect to the second mold 52b, and the cavity 37 is slightly enlarged. In this state, the shut-off valve 28 is opened, the screw of the first injection unit 2A is advanced, and an appropriate amount of resin A is injected and filled as a skin material into the cavity 37 based on past knowledge.

Then, a so-called outer layer is formed by injection-filling the resin A into the cavity 37. When molding a molded product having an outer layer and an inner layer by co-injection, a virgin material is used for the A resin, and a recycled material or a different material or a material having a different grade is used for the B resin that forms the so-called inner layer, which will be described later. Use it.

Next, the needle valve driving cylinder 20 is driven to retract the needle valve 19 to form a communication passage for the resin between the second injection unit 2B and the cavity 37 (FIG. 4).

Subsequently, the shut-off valve 28 is rotated,
It is closed (FIG. 5). Then, the second injection unit 2B
Is advanced, and a proper amount of B resin as a core material is injected and filled into the cavity 37 through the inner passage 22 and the hot runner 27 (FIGS. 6 and 7). Note that the first injection unit 2A and the second injection unit 2B can be simultaneously injected with the shut-off valve 28 kept open.

In this case, since the mold is opened to a predetermined shape or more in advance, the flow front of the core material, which is injected to form the core layer based on past knowledge, is first injected to form the skin layer. Until the skin material reaches the vicinity of the flow front, the skin material remains in the side wall member 56 (56).
a, 56b), the core material has undergone diffusion flow in the width direction, and many core materials can be filled (FIGS. 7 and 8).

At this time, since the core material does not directly contact the second mold 52b, the core material has fluidity. Therefore, in the cavity 37, the solidification state of the skin material progresses, and at the same time, the core material is injected. Filling is continued. For this reason, more recycled material can be included in the virgin material until the flow front of the core material forming the core layer reaches the vicinity of the flow front of the skin material that is first injected and forms the skin layer, and Can be used effectively.

Thereafter, the shut-off valve 28 is opened, the needle valve 19 is advanced by the driving of the needle valve driving cylinder 20, and the inner annular passage 24 is closed. By advancing the screw and injecting and filling the resin A, the resin B as the core material is sealed by the resin A as the skin material, and a molded article having an outer layer and an inner layer is obtained. Thereafter, the mold is advanced again to a predetermined position to perform mold clamping (FIG. 9).

Next, a case where a molded product having an outer layer and an inner layer is molded using a B-type mold will be described with reference to FIGS. First, the fixed platen 5 and the movable platen 8 are held at a fixed interval by an appropriate mold clamping device (for example, using a direct pressure type or a toggle type). Further, the shut-off valve 28 is opened in the cavity 37 surrounded by the movable molds 9a, 9b and the side wall members 60a, 60b slidably arranged in the direction intersecting with the injection direction, and the first injection unit 2A. Is advanced and the resin A is injected and filled into the cavity 37 as a skin material in an appropriate amount based on past knowledge (FIGS. 3 and 10).

Then, the injection and filling of the resin A into the cavity 37 forms a so-called outer layer. When molding a molded product having an outer layer and an inner layer by co-injection, a virgin material is used for the A resin, and a recycled material or a different material or a material having a different grade is used for the B resin that forms the so-called inner layer, which will be described later. Use it.

Next, the needle valve driving cylinder 20 is driven to retract the needle valve 19 to form a communication passage for the resin between the second injection unit 2B and the cavity 37 (FIG. 4). Subsequently, the shut-off valve 28 is turned to the closed state (FIG. 5). Then, the screw of the second injection unit 2B is advanced, and the B resin as a core material is supplied to the cavity 37 through the inner passage 22 and the hot runner 27.
It is injected and filled in an appropriate amount (FIG. 11). Note that the first injection unit 2A and the second injection unit 2B can be simultaneously injected with the shut-off valve 28 kept open.

In this case, when the movable dies 9a and 9b are opened by a predetermined amount in a direction in which the movable dies 9a and 9b are separated with good timing by driving cylinders (not shown) in accordance with the injection of the B resin as the core material, the movable dies 9a , 9b, when cooled and solidified, the viscosity of the resin increases and the fluidity deteriorates. On the other hand, the B resin of the core material has a good fluidity because the resin temperature is not lowered, and is injected and filled vigorously by the pressing force of the core material having good fluidity while expanding the skin material (FIG. 12). ).

Since the B resin of the core material is vigorously injected and filled into the skin material even after the movable molds 9a and 9b are opened,
Due to the hydrostatic pressure difference acting on the interface between the core material and the skin material, the skin material becomes more and more owing to the shearing stress on the surface layer of the skin material along the interface against the background of the velocity difference accompanying the flow of the core material through the interface. As a result, the core material is injected and filled into the skin material more. In addition, the flow front portion of the skin material that is not in contact with the movable molds 9a and 9b is different from the extremely surface portion of the skin material that has already been cooled by contact with the movable molds 9a and 9b and has almost no fluidity. Due to the action of the core material, which is not cooled but keeps the fluidity, it is thinly extended in the injection direction (FIG. 13).

For this reason, when the flow front of the core material forming the core layer reaches the vicinity of the flow front of the skin material forming the skin layer by injection first, the most recycled material is included in the virgin material. And the effective use of recycled materials.

Thereafter, the shut-off valve 28 is opened, the needle valve 19 is advanced by driving the needle valve driving cylinder 20, and the inner annular passage 24 is closed. By advancing the screw and injecting and filling the A resin, the B resin as the core material is sealed by the A resin as the skin material (FIG. 14).

After the core material is injected, the movable molds 9a, 9b
By opening the mold, a diffusion flow in the width direction occurs, and a large amount of core material can be filled. Thereafter, when the mold is moved forward again to a predetermined position to perform mold clamping, more core material is injected and filled into the thinly stretched skin material, and a molded article having an outer layer and an inner layer is obtained. (FIG. 15).

[0041]

As is clear from the above description, according to the present invention, the skin material can be made thinner while the core material can be injected and filled more, and the recycled material can be effectively used. Further, by injecting and filling more core materials that do not come into direct contact with the mold, the material can be gradually cooled, thereby reducing product distortion. Furthermore, when the flow front of the core layer reaches near the flow front of the skin layer, the mold cavity is reduced, so that the entire surface of both the core material and the skin material in the molten state is uniformly compressed. Since a force is applied, it is possible to obtain a molded product with little distortion without generating a pressure gradient in the flow direction.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold showing an injection state according to the present invention.

FIG. 2 is a partially cutaway front view of the injection molding machine.

FIG. 3 is an operation explanatory view showing movements of a needle valve and a shaft off valve when a mixing nozzle is used.

FIG. 4 is an operation explanatory diagram showing a continuation of the operation in FIG. 3;

FIG. 5 is an operation explanatory view showing the continuation of FIG. 4;

FIG. 6 is an explanatory diagram of an injection operation using a mold capable of expanding and contracting a cavity in an injection direction.

FIG. 7 is an operation explanatory diagram showing a continuation of the operation in FIG. 6;

FIG. 8 is an operation explanatory diagram showing a continuation of the operation in FIG. 7;

FIG. 9 is an operation explanatory diagram showing a continuation of FIG. 8;

FIG. 10 is an explanatory view of an injection operation using a mold capable of expanding and contracting a cavity in a direction intersecting with an injection direction.

FIG. 11 is an operation explanatory diagram showing a continuation of the operation in FIG. 10;

FIG. 12 is an operation explanatory view showing a continuation of the operation in FIG. 11;

FIG. 13 is an operation explanatory view showing a continuation of the operation in FIG. 12;

FIG. 14 is an operation explanatory view showing a continuation of the operation in FIG. 13;

FIG. 15 is an operation explanatory diagram showing a continuation of the operation in FIG. 14;

FIG. 16 is an explanatory diagram for explaining a conventional method for forming a sandwich molded product.

FIG. 17 is an enlarged view of a cavity part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Injection unit 2A 1st injection unit 2B 2nd injection unit 5 Fixed plate 7 Fixed die 8 Movable plate 9 (9a, 9b) Movable die 10 Multi-material molding block 12 (12A, 12B) Injection nozzle DESCRIPTION OF SYMBOLS 13 Contact part 14, 33A, 33B Spool 15 Blocking nozzle 16 Tip block 17 First block 18 Second block 19 Needle valve 20 Needle valve driving cylinder 21 Cylindrical piece 22 Inner passage 23 Outer passage 24 Inner annular passage 25 Outer annular passage 26 Tip end 27, 34A, 34B Hot runner 28 Shut-off valve 31 First nozzle 32 Second nozzle 35 Mixing nozzle 36 Twin nozzle 37 Cavity 50 Upper die 52 Intermediate die 52a First die 52b Second Mold 56 (56a, 56b) Side wall member 8 inner surface 60 (60a, 60b) side wall member 62 inner surface

Claims (4)

[Claims] After a mold is opened in advance and a cavity is formed, a part of an outer core material for forming a skin layer having a smooth surface is first partially injected into the cavity, and then the outer core material is formed. Inject the inner core material that forms the core layer inside,
A sandwich molded product characterized in that the flow front of the core layer reaches the vicinity of the flow front of the previously injected skin layer and then the skin material is continuously injected, and then the mold is tightened to a predetermined position. Production method. 2. An outer core material for forming a skin layer is first partially injected into a cavity, and then an inner core material for forming a core layer is injected into the skin layer, and at the same time, a mold is opened to open a cavity portion. A method for manufacturing a sandwich molded product, wherein the mold is clamped to a predetermined position after expanding and injecting the outer core material again after the inner core material. 3. A sandwich molding die formed by superposing three layers by an upper die having a flat plate shape and an intermediate die interposed between the lower die, wherein the intermediate die is arranged in the injection direction. The first mold and the second mold which can be freely contacted to and separated from each other, and the side wall member which is disposed opposite to the step forming position of the first and second molds are formed so as to form a cavity part which is expandable and contractible. A mold for sandwich molding, characterized in that: 4. A sandwich molding die formed in three layers by an upper die having a flat plate shape and an intermediate die interposed between the lower die, wherein the intermediate die has an injection direction. A sandwich characterized in that it is surrounded by a pair of movable molds that can be freely moved in and out in the cross direction and side wall members respectively attached to the fixed plate and the movable plate to form a cavity portion that can be expanded and contracted. Mold for molding.