JP3743031B2 - Injection molding method and injection mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for injection molding resins of different colors and materials, and an injection molding die used in the method.
[0002]
[Prior art]
Examples of molded products made of resins of different colors and materials include, for example, cassette tape cases with transparent plastic windows, game machine housings, and the like.
Such a molded product made of resin of different colors and materials is generally molded by a rotary type injection molding machine or a core back type injection molding machine.
FIG. 12 is a cross-sectional side view showing an outline of a rotary type injection molding machine that molds molded products made of two resins one by one.
This injection molding machine includes a primary side nozzle 1 and a secondary side nozzle 2 that respectively inject two resins, and a primary side gate 5 that guides each injected resin to the primary side molding unit 3 and the secondary side molding unit 4. And a secondary die 6 that can be moved in the direction of the arrow a by a driving means 18 such as a hydraulic cylinder, and can be moved in the direction of the arrow b by a driving means 8 such as a hydraulic cylinder. And a second mold 10 that can be rotated in a direction indicated by an arrow c by a driving means 9 such as a motor.
[0003]
In such a configuration, an injection molding method will be described. The first mold 7 is moved by the driving means 18 to close the first mold 7 and the second mold 10. The primary side resin is injected from the primary side nozzle 1 to the primary side molding portion 3 through the primary side gate 5. And after hold | maintaining pressure for a predetermined time, it cools for a predetermined time, and the 2nd metal mold | die 10 is moved by the drive means 8 after that, and the 1st metal mold | die 7 and the 2nd metal mold | die 10 are opened. The second mold 10 is rotated by the driving means 9 and moved by the driving means 8 to close the first mold 7 and the second mold 10. The secondary side resin is injected from the secondary side nozzle 2 to the secondary side molding portion 4 through the secondary side gate 6. And after holding pressure for a predetermined time, it cools for a predetermined time, and the 1st metal mold | die 7 is moved by the drive means 18 after that, the 1st metal mold | die 7 and the 2nd metal mold | die 10 are opened, and a molded product is taken out.
However, the injection molding method using this rotary type injection molding machine has the disadvantage that the second mold 10 has to be rotated, takes a long time, and can be applied only to expensive molded products.
[0004]
Therefore, an injection molding method using a core-back type injection molding machine is employed for an inexpensive molded product.
FIG. 13 is a cross-sectional side view schematically showing a core-back type injection molding machine that simultaneously molds two molded articles made of two resins.
The injection molding machine includes a primary side nozzle 11 and a secondary side nozzle 12 for injecting two resins, a primary side gate 15 for guiding each injected resin to a primary side molding part 13 and a secondary side molding part 14, and A first mold 17 having a secondary gate 16 and movable in the direction of the arrow d in the figure by a driving means 19 such as a hydraulic cylinder, a second mold 20 fixed to the injection molding machine body, and a second A slide core 22 is disposed in the mold 20 and moved by a driving means 21 such as a hydraulic cylinder to form a secondary side molding portion 14.
[0005]
In such a configuration, an injection molding method will be described. The first mold 17 is moved by the driving means 19 to close the first mold 17 and the second mold 20, and the slide core 22 is moved by the driving means 21 to contact the first mold 17. The primary side resin is injected from the primary side nozzle 11 to the primary side molding part 13 through the primary side gate 15 ((A) in the figure). And after holding pressure for a predetermined time, it cools for a predetermined time, and the slide core 22 is moved by the drive means 21 after that, and the secondary side shaping | molding part 14 is formed. The secondary side resin is injected from the secondary side nozzle 12 to the secondary side molding part 14 through the secondary side gate 16 ((B) in the figure). Then, the pressure is maintained for a predetermined time and then cooled for a predetermined time. Thereafter, the first mold 17 is moved by the driving means 19 to open the first mold 17 and the second mold 20, and the molded product is taken out.
[0006]
[Problems to be solved by the invention]
However, the injection molding method using the above-described conventional core-back type injection molding machine has a problem that the primary side resin is injected when the secondary side resin is injected when the secondary side resin has a higher melting temperature than the primary side resin. Has the disadvantage of melting.
When injecting the secondary side resin, the slide core 22 is moved to stop the secondary side resin, but the residue of the primary side resin is sandwiched between the slide core 22 and the first mold 17. Therefore, there is a drawback that the surface of the molded product of the secondary side resin becomes uneven.
[0007]
Furthermore, there is a drawback that the shape of a molded product applicable to an injection molding method by a conventional core-back type injection molding machine is limited.
FIG. 14 is a cross-sectional side view showing an example of a molded product suitable for an injection molding method using a conventional core-back type injection molding machine. The molded product 21 is a game machine housing having an outer frame 22 made of a colored primary resin and a window 23 made of a transparent secondary resin disposed in the outer frame 22. The reason why this molded article 21 is suitable for the injection molding method by the conventional core-back type injection molding machine is that the outer frame 22 is not deformed by the pressure P1 applied to the outer frame 22 when the window 23 is molded. This is because the pressure stopper 22a is provided and the width and thickness of the dimension a are taken so as to have sufficient strength against the pressure P1.
[0008]
Accordingly, as shown in the perspective views of FIGS. 15 and 16 and the cross-sectional side view thereof, outer frames 25a and 25b made of colored primary resin, and a transparent secondary side disposed in the outer frames 25a and 25b. In the case of a molded product 24 that is a casing of a game machine having a window 26 made of resin, no pressure stopper is provided, and against the pressure P2 applied to the outer frames 25a and 25b when the window 26 is molded. Since the width of the dimension having sufficient strength is zero and the thickness is thin, there is a drawback that the outer frames 25a and 25b are deformed.
Further, since the molded product 24 has two layers of undercuts 27, the undercuts 27 cannot be taken out from the second mold 20 side as shown in FIG. Therefore, it has to be taken out from the first mold 17 side, and there is a disadvantage that workability is poor.
[0009]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an injection molding method and an injection mold that can obtain a good molded product regardless of the shape of the molded product. It is said.
[0010]
[Means for Solving the Problems]
In the injection molding method for obtaining a molded product by sequentially injecting different materials, the above object is achieved by moving the inner slide core movable in a predetermined direction and molding the inner side of the molded product. The inner slide core is moved in the direction opposite to the moving direction, and the outer slide core movable in a predetermined direction is divided, and the divided portion is moved together to move the inner slide. It is achieved by pressing with a core, molding the outside of the molded product, dividing the divided portion of the outer slide core , moving in the direction opposite to the moving direction, and taking out the molded product. In addition, in an injection mold for sequentially injecting different materials to obtain a molded product, the mold can be moved in a predetermined direction, and an inner slide core for molding the inside of the molded product, and a predetermined direction An outer slide core that is pressed by the inner slide core to mold the outer side of the molded product, the outer slide core being divided, and the molding This is achieved by combining the divided portions when molding the outside of the product and dividing the divided portions when taking out the molded product.
[0011]
According to the above configuration, the inside of the molded product is first molded, and then the outer slide core, which is a combination of the divided parts, is pressed with the inner slide core to mold the outer side of the molded product. It is possible to prevent the molded product from being defective due to pressure at the time of molding.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms.
[0013]
FIG. 1 is a cross-sectional side view showing an embodiment of an injection molding machine provided with an embodiment of an injection mold according to the present invention, and FIG. 2 is a cross-sectional side view in the perpendicular direction.
The injection molding machine 30 is a cross-sectional side view schematically showing a core-back type injection molding machine that simultaneously molds two molded products made of two resins.
In this injection molding machine 30, the window 26 is formed using a transparent resin as the primary side resin, and the outer frames 25a and 25b are formed using a colored resin as the secondary side resin.
[0014]
This injection molding machine 30 includes a primary side nozzle 31 and a secondary side nozzle 32 for injecting two materials of resin, and a primary side nozzle 31 and a secondary side nozzle 32. It has a primary side gate 35 and a secondary side gate 36 that lead to the secondary side molding part 34, and is fixed to a second mold 39 that can be moved in the X direction by a driving means 37 such as a hydraulic cylinder, and an injection molding machine 30 main body. The first mold 38 that forms the second mold 39 and the primary side molding part 33, and the first mold 38 and the second mold 39 are disposed in association with the driving means 51f, 51g such as a hydraulic cylinder. , 52b and a third mold 50 that forms the secondary molding part 34.
[0015]
The third mold 50 provided in the injection molding machine 30 has two side surfaces (hereinafter referred to as core cores) having an undercut 27 in the outer frames 25a and 25b of the molded product 24 shown in FIG. Two sets of core-forward molds 51 for molding each of the first and second sets of core-back molds 52 for molding the remaining two side surfaces (hereinafter referred to as core-back) It has.
As shown in FIG. 4, the core forward mold 51 is divided into three parts, and is integrated with the first slide core 51 a responsible for molding the outer periphery of the window 26 of the molded product 24 and the outer periphery of the window 26. It comprises a second slide core 51b and a third slide core 51c responsible for core forward molding, and driving means 51f and 51g such as hydraulic cylinders.
[0016]
The first slide core 51a is connected to the driving means 51f and slides in the Z direction. The second slide core 51b is fixed to the fixing core 51d, and the third slide core 51c is connected to the second slide core 51b by the compression spring 51e and slides in the Z direction on the fixing core 51d. It has become. The fixing core 51d is connected to the driving means 51g and slides in the X direction.
As shown in FIG. 5, the core-back mold 52 includes a fourth slide core 52a responsible for molding the core-back integrated with the outer periphery of the window 26 of the molded product 24, and driving means 52b such as a hydraulic cylinder. It consists of and.
The fourth slide core 52a is connected to the drive means 52b and slides in the X direction.
[0017]
In such a configuration, an embodiment of the injection molding method of the present invention will be described based on the flowchart of FIG. 3 and the operation diagrams of FIGS. In the second mold 39, + a movement in the X direction is forward, - a and backward movement in the X direction. In the first and third slide cores 51a and 51c, the movement in the + Z direction is defined as forward movement, and the movement in the -Z direction is defined as backward movement. Further, in the fixing core 51d and the fourth slide core 52a, the movement in the + X direction is defined as forward movement, and the movement in the −X direction is defined as backward movement.
[0018]
The driving means 37 is driven to advance the second mold 39 , the first mold 38 and the second mold 39 are closed, and the driving means 51g is driven to retract the fixing core 51d (STP1). At this time, the second and third slide cores 51b and 51c move with the retraction of the fixing core 51d and are opened by the action of the compression spring 51e. Next, the driving means 51f and 52b are driven to advance the first and fourth slide cores 51a and 52a (STP2), thereby forming the primary side molding portion 33 (STP3). Each part at this time is arranged as shown in FIGS.
[0019]
Then, the primary side resin is injected from the primary side nozzle 31 to the primary side molding portion 33 through the primary side gate 35, and after holding for a predetermined time, it is cooled (STP4, 5). In the middle of the cooling, the driving means 51f and 52b are driven to retract the first and fourth slide cores 51a and 52a (STP6). The retracted position of the first slide core 51a at this time is a position retracted by the distance A shown in FIG. 6, and the tapered surface of the first slide core 51a and the tapered surface of the third slide core 51c are on the same plane. Is the position.
[0020]
Then, the driving means 51g is driven to advance the fixing core 51d (STP7). At this time, the second and third slide cores 51b and 51c move as the fixing core 51d advances, and the taper surface of the third slide core 51c slides with the taper surface of the first slide core 51a. To do. Accordingly, the taper surface of the third slide core 51c is gradually pushed by the taper surface of the first slide core 51a, and finally the second and third slide cores 51b and 51c are closed. With the above operation, the secondary side molding portion 34 is formed (STP8). Each part at this time is arranged as shown in FIGS.
[0021]
Then, the secondary side resin is injected from the secondary side nozzle 32 to the secondary side molding portion 34 through the secondary side gate 36, and after holding for a predetermined time, it is cooled (STP 9, 10). Then, the driving means 37 is driven to retract the second mold 39 (STP11), and the first mold 38 and the second mold 39 are opened. At this time, the first slide core 51a moves as the second mold 39 moves backward, and the taper surface of the third slide core 51c and the taper surface of the first slide core 51a are separated from each other. The three slide cores 51b and 51c are opened by the action of the compression spring 51e. Therefore, as shown in FIG. 9, the protrusion 511 c provided on the third slide core 51 c to form the undercut 27 of the molded product 24 comes off from the molded product 24. It can be taken out from the mold 39 side (STP12). Then, it is determined whether or not the injection molding is continued (STP13). When the injection molding is continued, the process returns to STP1 and the above-described operation is repeated. When the injection molding is not continued, all the processes are terminated.
[0022]
FIGS. 11A and 11B show an example of the cycle time when a molded product having a transparent portion and a colored portion as shown in FIG. 10 is molded by a conventional injection molding machine and the above-described injection molding machine. . The numbers in the figure indicate the required time (seconds).
First, in the molding of the transparent portion, what was conventionally the secondary side molding is the primary side molding, so that high-speed injection is possible and the injection time is shortened. Further, in taking out the molded product, what was conventionally taken out from the first mold side is taken out from the second mold side, so that the taking time becomes easy and the taking time is shortened. Further, in the welding of the transparent part and the colored part, conventionally, if the colored part is insufficiently solidified, the colored part is deformed by the molding pressure of the transparent part, so it is necessary to sufficiently cool the colored part. The overlapping time of forming the colored portion, that is, the welding time was short, and the overall cycle time was long. However, since the transparent portion is formed first, the colored portion can be formed during the cooling of the transparent portion, and the welding time becomes long, so that the overall cycle time is eventually shortened.
By reducing the overall cycle time, molding defects such as warpage are less likely to occur.
[0023]
As described above, since the taper surface of the third slide core 51c is pressed against the taper surface of the first slide core 51a during the secondary side molding, the pressure caused by the injected secondary side resin Even if the third slide cores 51b and 51c receive, the second and third slide cores 51b and 51c do not move backward. Therefore, if the outer frames 25a and 25b of the molded product 24 made of the secondary side resin are molded in this state, the outer frame 25a side is pressed by the second and third slide cores 51b and 51c, and the outer frame 25b side is Since it is pressed by the window 26 of the molded product 24 made of the already cured primary resin, there is no risk of deformation due to the molding pressure as in the prior art.
[0024]
Further, since the molding of the window 26 of the molded product 24 is performed by the fixed second mold 39, the outer frames 25a and 25b of the molded product 24 are interposed between the slide core 22 and the first mold 17 as in the prior art. It is possible to prevent a defect that the residue is caught and the surface of the window 26 becomes uneven.
Furthermore, since the welding time of the window 26 of the molded product 24 and the outer frames 25a and 25b becomes longer, the reliability of the molded product can be improved.
Further, since the outer frames 25a and 25b of the molded product 24 that is the colored portion are formed on the secondary side, even if the window 26 of the molded product 24 that is the transparent portion melts, the appearance of the molded product does not stand out.
Note that the above-described molding method can also be applied to molding of three or more different materials, colors, mechanical properties, and the like.
[0025]
【The invention's effect】
As described above, according to the present invention, a good and highly accurate molded product can be obtained regardless of the shape of the molded product.
[Brief description of the drawings]
FIG. 1 is a cross-sectional side view showing an embodiment of an injection molding machine provided with an embodiment of an injection mold according to the present invention.
FIG. 2 is a cross-sectional side view in the direction perpendicular to the cross-sectional side surface showing an embodiment of the injection molding machine shown in FIG.
FIG. 3 is a flowchart showing an embodiment of the injection molding method of the present invention.
FIG. 4 is a first view showing an operation example of one embodiment of an injection mold according to the present invention.
FIG. 5 is a second view showing an operation example of one embodiment of an injection mold according to the present invention.
FIG. 6 is a third view showing an operation example of one embodiment of an injection mold according to the present invention.
FIG. 7 is a fourth view showing an operation example of one embodiment of an injection mold according to the present invention.
FIG. 8 is a fifth view showing an operation example of one embodiment of an injection mold according to the present invention.
FIG. 9 is a sixth view showing an operation example of one embodiment of an injection mold according to the present invention.
FIG. 10 is a plan view showing an example of a molded product.
FIG. 11 is a diagram showing an example of a conventional injection molding method and an example of a cycle time of an embodiment of the injection molding method of the present invention.
FIG. 12 is a sectional side view showing an example of a conventional injection molding machine.
FIG. 13 is a cross-sectional side view showing another example of a conventional injection molding machine.
FIG. 14 is a sectional side view showing another example of a molded product.
15 is a perspective view of the molded product shown in FIG.
16 is a cross-sectional side view of the molded product shown in FIG.
FIG. 17 is a view for explaining problems in conventional injection molding.
[Explanation of symbols]
24 Molded product 25a Outer frame (outside of molded product)
25b Outer frame (outside of molded product)
26 Window (inside the molded product)
27 Under cut (outside of molded product)
30 injection molding machine 31 primary side nozzle 32 secondary side nozzle 33 primary side molding part 34 secondary side molding part 35 primary side gate 36 secondary side gate 37 driving means 38 first mold 39 second mold 50 third metal Mold 51 Core-forward mold 52 Core-back mold 51a First slide core (inner slide core)
51b Second slide core (outside slide core)
51c 3rd slide core (slide core for outside)
51d Fixing core 51e Compression spring 51f Driving means 51g Driving means 52a Fourth slide core (inner / outer slide core)
52b Driving means

Claims (2)

In an injection molding method for obtaining a molded product by sequentially injecting different materials,
Move the inner slide core that can move in the specified direction,
Molding the inside of the molded article,
Moving the inner slide core in a direction opposite to the moving direction;
The outer slide core that can move in a predetermined direction is divided, and the divided portions move together and are pressed by the inner slide core,
Molding the outside of the molded article,
Dividing the dividing portion of the outer slide core and moving in the direction opposite to the moving direction;
An injection molding method comprising: taking out the molded product. In injection molds for sequentially injecting different materials to obtain molded products,
An inner slide core that is movable in a predetermined direction and for molding the inner side of the molded article;
An outer slide core that is movable in a predetermined direction and is pressed by the inner slide core to mold the outer side of the molded product ,
An injection molding metal characterized in that the outer slide core is divided, and the divided portions are united when the outside of the molded product is molded, and the divided portions are divided when the molded product is taken out. Type.

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